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SULFUR DIOXIDE

See Occupational Exposure Standards

Human Health Effects:

Evidence for Carcinogenicity:

Evaluation: There is inadequate evidence for the carcinogenicity in humans of sulfur dioxide, sulfites, bisulfites and metabisulfites. There is limited evidence for the carcinogenicity in experimental animals of sulfur dioxide. There is inadequate evidence for the carcinogenicity in experimental animals of sulfites, bisulfites and metabisulfites. Overall evaluation: Sulfur dioxide, sulfites, bisulfites and metabisulfites are not classifiable as to their carcinogenicity to humans (Group 3).
[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work).p. 54 178 (1992)]**PEER REVIEWED**

A4; Not classifiable as a human carcinogen.
[American Conference of Governmental Industrial Hygienists. TLVs & BEIs: Threshold limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices for 2002. Cincinnati, OH. 2002.54]**QC REVIEWED**

Human Toxicity Excerpts:

SEVERE INJURIES OF HUMAN EYES BY SULFUR DIOXIDE HAVE BEEN PRODUCED ONLY BY LIQUIFIED FORM. ... IMMEDIATELY AFTER THE EYE HAS BEEN SPRAYED ... THE CORNEAL EPITHELIUM BECOMES GRAY & IRREGULAR, BUT REMAINS ADHERENT TO STROMA ... SEVERAL HR LATER LIDS BECOME SWOLLEN. CONJUNCTIVAL EPITHELIUM APPEARS WHITE & RATHER OPAQUE. VESSELS ... MAY BE ... THROMBOSED.
[Grant, W.M. Toxicology of the Eye. 3rd ed. Springfield, IL: Charles C. Thomas Publisher, 1986. 863]**PEER REVIEWED**

A PERIOD OF ... EXPOSURE OF OVER 2 YR TO VARIABLE CONCN ON THE ORDER OF 30 PPM WITH OCCASIONAL PEAKS OF UP TO 100 PPM ... PRODUCED ... AN ALTERATION OF SENSES OF SMELL & TASTE, HIGH URINARY ACIDITY, & INCREASED FATIGUE.
[Patty, F. (ed.). Industrial Hygiene and Toxicology: Volume II: Toxicology. 2nd ed. New York: Interscience Publishers, 1963. 894]**PEER REVIEWED**

... DESTRUCTION OF PROTECTIVE CILIATED EPITHELIUM, & INVASION OF LUNG BY BACTERIA ARE CONQUENCES OF ACUTE SULFUR DIOXIDE POISONING.
[Hamilton, A., and H. L. Hardy. Industrial Toxicology. 3rd ed. Acton, Mass.: Publishing Sciences Group, Inc., 1974. 210]**PEER REVIEWED**

INHALATION PRODUCES ALL GRADES OF RESPIRATORY TRACT IRRITATION SOMETIMES WITH PULMONARY EDEMA. VAPOR CONCN PROBABLY DETERMINES MODE OF DEATH: EG, SUFFOCATION FROM REFLEX RESP ARREST (VERY HIGH CONCN), PULMONARY EDEMA (MODERATE CONCN), OR SYSTEMIC ACIDOSIS (LOW CONCN). THERE IS SOME INDICATION OF SIGNIFICANT VARIATION IN INDIVIDUAL SUSCEPTIBILITY.
[Gosselin, R.E., R.P. Smith, H.C. Hodge. Clinical Toxicology of Commercial Products. 5th ed. Baltimore: Williams and Wilkins, 1984.,p. II-96]**PEER REVIEWED**

WITH ACUTE EXPOSURE, 5 PPM CAUSES DRYNESS OF NOSE & THROAT AND A MEASUREABLE INCR IN RESISTANCE TO BRONCHIAL AIR FLOW; 6 TO 8 PPM CAUSES A DECR IN TIDAL RESP VOLUME. SNEEZING, COUGH & EYE IRRITATION OCCUR AT 10 PPM; 20 PPM CAUSED BRONCHOSPASM; 50 PPM CAUSES EXTREME DISCOMFORT BUT NO INJURY IN LESS THAN A 30-MIN EXPOSURE ... 1000 PPM CAUSES DEATH IN FROM 10 MIN TO SEVERAL HR BY RESP DEPRESSION.
[Thienes, C., and T.J. Haley. Clinical Toxicology. 5th ed. Philadelphia: Lea and Febiger, 1972. 198]**PEER REVIEWED**

EXPOSURE TO HIGH CONCN CAUSE REFLEX CLOSURE OF GLOTTIS FOR SEVERAL MINUTES. ... PERSONS SUBJECT TO ASTHMATIC ATTACKS WILL EXPERIENCE ASTHMATIC PAROXYSM WHICH MAY PERSIST FOR SEVERAL DAYS FOLLOWING EXPOSURE.
[Thienes, C., and T.J. Haley. Clinical Toxicology. 5th ed. Philadelphia: Lea and Febiger, 1972. 198]**PEER REVIEWED**

IN THE MORE ADVANCED STAGES, ... DILATION OF BLOOD VESSELS IN CERTAIN REGIONS. ULCERATION OF NASAL SEPTUM, WHICH BLEEDS READILY, MAY ... BE OBSERVED.
[International Labour Office. Encyclopedia of Occupational Health and Safety. Vols. I&II. Geneva, Switzerland: International Labour Office, 1983. 2122]**PEER REVIEWED**

THERE MAY ALSO BE THORACIC PAIN & STRICTION, DYSPNEA, LACRIMATION ... BURNING SENSATION & PAIN IN ESOPHAGUS & STOMACH, NAUSEA & (ALTHOUGH RARELY) VOMITING.
[International Labour Office. Encyclopedia of Occupational Health and Safety. Volumes I and II. New York: McGraw-Hill Book Co., 1971. 1370]**PEER REVIEWED**

INHIBITION OF THYROID FUNCTION & IN WOMEN, MENSTRUAL DISORDERS ... .
[International Labour Office. Encyclopedia of Occupational Health and Safety. Volumes I and II. New York: McGraw-Hill Book Co., 1971. 1370]**PEER REVIEWED**

PERSONS WHO HAVE A LONG HISTORY OF EXPOSURE TO HIGH CONCN OF SULFUR DIOXIDE MAY SUFFER FROM CHRONIC BRONCHITIS ACCOMPANIED BY EMPHYSEMA. ... NERVOUS SYSTEM DISORDERS ARE OF A FUNCTIONAL NATURE-NEUROTIC & VEGETO-ASTHENIC-PROBABLY DUE TO THE GENERAL TOXICITY OF SULFUR DIOXIDE ON THE BODY. STOMATOLOGICAL EXAM MAY REVEAL DENTAL CARIES, & PERIDONTAL & GINGIVAL DISORDERS. PATIENTS MAY COMPLAIN OF RAPID & PAINLESS DENTAL DESTRUCTION, LOSS OF FILLINGS, & INCR TOOTH SENSITIVITY TO TEMP CHANGES.
[International Labour Office. Encyclopedia of Occupational Health and Safety. Vols. I&II. Geneva, Switzerland: International Labour Office, 1983. 2122]**PEER REVIEWED**

DUE TO ITS HIGH SOLUBILITY, SULFUR DIOXIDE IS RAPIDLY DISTRIBUTED THROUGHOUT THE BODY, PRODUCING METABOLIC ACIDOSIS WITH A REDUCTION IN BLOOD ALKALI RESERVE & COMPENSATORY ELIMINATION OF AMMONIA IN URINE & ALKALI IN SALIVA. THE GENERAL TOXIC ACTION IS DEMONSTRATED BY PROTEIN & CARBOHYDRATE METABOLISM DISORDERS. IT IS PROBABLE THAT THE ABSORPTION OF LARGE QUANTITIES ... HAS A PATHOLOGICAL EFFECT ON HEMOPOIETIC SYSTEM AND MAY PRODUCE METHEMOGLOBIN.
[International Labour Office. Encyclopedia of Occupational Health and Safety. Vols. I&II. Geneva, Switzerland: International Labour Office, 1983. 2122]**PEER REVIEWED**

Delayed particle clearance times have been observed at low levels of sulfur dioxide exposure. This indicates an impairment of the lung to function properly. This effect is more prominent with prolonged exposure to low concentrations than for short exposures to high concentrations.
[OSHA; Public Hearing on Occupational Standard for Sulfur Dioxide: Statement of Edward Baier (NIOSH) (May 1977) PB 83-182485]**PEER REVIEWED**

Exposures of less than an hour to sulfur dioxide at levels above 10 ppm in air are irritating to the nose and throat, sometimes causing a choking sensation followed by nasal discharge, sneezing, coughing, and increased mucous secretion.
[OSHA; Public Hearing on Occupational Standard for Sulfur Dioxide: Statement of Edward Baier (NIOSH) (May 1977) PB 83-182485]**PEER REVIEWED**

Approx 10,000 workers in the British steel industry were studied for chronic effects. At mean exposures to sulfur dioxide of about 0.35 ppm (0.9 mg/cu m), no effects were found.
[Lowe CR et al; Brit J Industr Med 27: 121 (1970) as cited in OSHA; Public Hearing on Occupational Standard for Sulfur Dioxide: Statement of Edward Baier (NIOSH) (May 1977) PB 83-182485]**PEER REVIEWED**

Twenty five healthy adults were tested and found to have increased airway resistance (determined in a body plethysmograph) at 5 ppm (13 mg/cu m) of sulfur dioxide and at higher levels when breathing normally for 10 min, but not at lower levels. After 25 deep breaths, as might occur in laborers doing hard physical work, the subjects had a statistically significant increase in airway resistance at 1 ppm and after 8 deep breaths at 3 ppm.
[Lawther PG et al; Environ Res 10: 335 (1975) as cited in OSHA; Public Hearing on Occupational Standard for Sulfur Dioxide: Statement of Edward Baier (NIOSH) (May 1977) PB 83-182485]**PEER REVIEWED**

An ecological study examined the relationship between ambient sulfur dioxide peaks and asthma attack incidence in 2 inner-city areas of New York City (NYC). Statistical tests were made for an association between days with sulfur dioxide peaks above various levels (0.1 ppm, 0.3 ppm, 0.5 ppm), as identified from hourly measurements obtained from the NYC Aerometric Network for the years 1969-1971, and days with higher numbers of emergency room visits for asthma at 3 municipal hospitals. No association was found.
[Goldstein IF, Weinstein AL; Environ Res 40: 332-45 (1986)]**PEER REVIEWED**

... Sulfur dioxide together with particulate matter and photochemical pollutants aggravate chronic pulmonary disease and incr the risk of acute and chronic resp illness. These compounds impair pulmonary mucociliary clearance, primarily in those pt with persisting pulmonary disease, probably as a result of hydrogen ion deposition on the bronchial lining.
[Ellenhorn, M.J., S. Schonwald, G. Ordog, J. Wasserberger. Ellenhorn's Medical Toxicology: Diagnosis and Treatment of Human Poisoning. 2nd ed. Baltimore, MD: Williams and Wilkins, 1997. 1461]**PEER REVIEWED**

6-12 ppm: May cause nasal and throat irritation. 10 ppm: Upper resp irritation, some nosebleeds. 20 ppm: Definitely irritating to eyes. Chronic resp symptoms develop at this level.
[Ellenhorn, M.J. and D.G. Barceloux. Medical Toxicology - Diagnosis and Treatment of Human Poisoning. New York, NY: Elsevier Science Publishing Co., Inc. 1988. 874]**PEER REVIEWED**

Acute effects: Direct resp tract irritation, cough, burning, lacrimation, conjunctival injection, difficulty in swallowing, and oropharyngeal erythema occur after substantial exposures. Vomiting, diarrhea, abdominal pain, fever, headache, vertigo, agitation, tremor, convulsions, and peripheral neuritis also have been noted. Acute high-dose exposures may produce immediate bronchospasm and pulmonary edema with subsequent resp failure. Clinical severity usually is readily apparent. Acute high-dose sulfur dioxide exposures have resulted in severe obstructive and restrictive defects 3 months postexposure, which failed to respond to bronchodilators. Rarely, such exposures have been associated with long-term, moderately severe, obstructive defects and persistent, productive cough.
[Ellenhorn, M.J. and D.G. Barceloux. Medical Toxicology - Diagnosis and Treatment of Human Poisoning. New York, NY: Elsevier Science Publishing Co., Inc. 1988. 875]**PEER REVIEWED**

High concentrations of sulfur dioxide may cause respiratory paralysis and pulmonary edema. In addition, about 10 to 20% of the adult population is estimated to be hypersensitive to the adverse respiratory effects of sulfur dioxide; however, workers regularly exposed to compound show an adaptation effect. Even though olfactory fatigue is a reported effect of exposure, the compound is so irritating that it is considered to have good warning properties.
[Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.74 (1985)]**PEER REVIEWED**

Symptomology: Inhalation: Irritation of the eyes, nose, throat, and skin; cough; sneezing and lacrimation; rhinorrhea; anosmia; reflex bronchoconstriction; increased pulmonary resistance to air flow; bronchial asthma; high pitched rales; thoracic pain and struction; nasopharyingitis; tracheitis, laryngeal edema; chemical bronchopneumonia; pulmonary edema; cyanosis; systemic acidosis; asphyxia; death. Ingestion: Irritation, lacrimation, iritis, burns, corneal damage, blindness. Skin contact: Irritation, Urticaria, lesions, burns.
[Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.82-82 (1985)]**PEER REVIEWED**

... 15 healthy subjects remained in an exposure chamber for 7-8 hours; control values were obtained, sulfur dioxide was gradually introduced, and the concentration was maintained at 1, 5, or 25 ppm for up to 6 hours. In seven subjects, the concentration of Sulfur dioxide was measured in pharyngeal gas samples obtained after exposure to the gas; in no subject was the concentration greater than 0.25 ppm, the smallest amount detectable by the methods used. ... Significant changes in nasal mucociliary flow rate at 5 and 25 ppm, and in nasal airway resistance and forced expiratory flow at 1, 5, and 25 ppm. No change in closing volume was found; changes in forced expiratory volume were significant only for the highest level of exposure.
[Anderson J et al; Arch Environ Health 28: 31 (1974) as cited in Nat'l Research Council Canada; Sulphur and its Inorganic Derivatives in the Canadian Environment p.292 (1977) NRCC No. 15015]**PEER REVIEWED**

12 healthy male adults were exposed to three concentrations of sulfur dioxide with and without the addition of sodium chloride aerosol. Pulmonary flow resistance did not increase significantly over control values at 1-2 ppm, but did at higher concentrations: an average increase of 39% over control values occurred 10 minutes after exposure to 4-6 ppm of sulfur dioxide. The addition of sodium chloride particles at concentrations of up to 24 mg/cu m did not increase the effects of sulfur dioxide observed at any concentration.
[Frank NR et al; Int J Air Water Pollut 8: 125 (1964) as cited in Nat'l Research Council Canada; Sulphur and its Inorganic Derivatives in the Canadian Environment p.293 (1977) NRCC No. 15015]**PEER REVIEWED**

Men working in a refrigerator company in the USA where sulfur dioxide was the refrigerant /were studied/. Exposures averaged 60-90 mg/cu m (20-32 ppm) with peaks as high as 200 mg/cu m (70 ppm). These peaks had probably been higher in the past ranging up to 290 mg/cu m (100 ppm) or more. The exposed group had significantly more respiratory symptoms and colds. They also complained more of fatigue and shortness of breath on exertion. Chest X-rays of the exposed and unexposed groups showed the same distribution of abnormalities. /It was concluded that/ there was no injury to the tracheobronchial tree or alveoli.
[Kehoe R et a; J Ind Hyg 14: 159-73 (1932) as cited in WHO; Environ Health Criteria: Sulfur Oxides and Suspended Particulate Matter p.64 (1979)]**PEER REVIEWED**

In a study in Norway, pulp mill workers were compared with paper mill workers using a standard questionnaire on respiration and simple tests of pulmonary function. The smoking histories of the subjects were also studied. Levels of sulfur dioxide ranged from 6-100 mg/cu m (2-36 ppm) with peaks of 290 mg/cu m (100 ppm) when the digester was blowing. The exposed group had more cough, sputum, and dyspnea than the unexposed group but the vital capacities were simliar in both groups. The expiratory peak flows, however, of the exposed men under 50 years of age were lower than those in comparable unexposed group.
[Skalpe IO; Br J Ind med 21: 69-73 (1964) as cited in WHO; Environ Health Criteria: Sulfur Oxides and Suspended Particulate Matter p.65 (1979)]**PEER REVIEWED**

In a study, comprising a series of experiments over a period of 4 yr, a small increase in specific airway flow resistance (flow resistance corrected for lung volume) was seen in response to sulfur dioxide at 1 ppm, but only if the subjects took 25 maximal breaths of the gas starting from residual volume. The procedure was designed to increase dosage to the laryngotracheobronchial airways. In one subject, there was a threefold increase in specific airway flow resistance with this procedure. As expected, sulfur dioxide at 3 ppm elicited greater changes in function than did 1 ppm. The magnitudes of these changes were proportional to the numbers of deep breaths taken.
[Ferris GB et al; Amer Rev Respir Dis 113: 475-85 (1976) as cited in National Academy of Sciences; Sulfur Oxides p.157 (1978)]**PEER REVIEWED**

The effects of sulfur dioxide and ozone alone and in combinations /were studied/, on young normal subjects under conditions of light exercise. When breathed alone, 0.37 ppm of sulfur dioxide had no effect on any measurement of lung function; 0.37 ppm of ozone produced a just significant decline of ventilatory function at the end of a 2 hour exposure. However, when the two gases were present together in eight normal young subjects who were non-smokers, the maximal mid-expiratory flow rate dropped to 67% of its initial value at the end of 2 hours; the forced expiratory volume was 78% of its initial value, and the mid-expiratory flow rate (50% vital capacity) was only 54% of the initial value. A 2 hour exposure to 0.75 ppm of Sulfur dioxide alone dropped the maximal mid-expiratory flow rate to 90% of its control value. /It was/ concluded that sulfur dioxide and ozone are exceedingly corrosive when present together, that "standard" must specify the presence or absence of the other, and that there is a growing incidence of the joint presence of the two pollutants in urban environments.
[Bates DV, Hazucha M; Paris Vol IV: 1977 (1974) as cited in Nat'l Research Council Canada; Sulphur and its Inorganic Derivatives in the Canadian Environment p.294 (1974) NRCC No. 15015]**PEER REVIEWED**

The 0.75 second forced expiratory volume of school children in Cincinnati, Chattanooga, and New York City, was studied, and examined differences by race, sex, socioeconomic levels, and exposure to total particulates, suspended sulfates, and sulfur dioxide. These authors were able to demonstrate differences in forced expiratory volume to support a relationship between suspended sulfates, other particulates and impaired function; the diference was apparent only after matching for age, sex, race, and socioeconomic status and when no overt clinical manifestations were present. The most dramatic difference occurred in Cincinnati, where children in "clean" neighborhoods had similar levels of sulfur dioxide but different levels of total particulates (61-85 ug/cu m in the clean area vs 96-133 ug/cu m polluted areas) and in suspended sulfates (7.7-9.1 ug/cu m vs. 8.9-10.1 ug/cu m).
[Shy CM et al; Arch Environ Health 27: 124 (1973) as cited in Nat'l Research Council Canada; Sulphur and its Inorganic Derivatives in the Canadian Environment p.297 (1977) NRCC No. 15015]**PEER REVIEWED**

Two recent studies have involved persons with underlying lung disease, as well as healthy persons. Nonsmoking health subjects and smokers who demonstrated functional defects associated with early obstructive pulmonary disease /were exposed/ to sulfur dioxide at 0, 0.3, 1.0, and 3.0 ppm. The subjects resided in an environmental chamber maintained at 22 + or - 1 deg C and 50 + or - 5% relative humidity. The exposures were administered in random sequence for 120 hr continuously to the healthy subjects, and for 96 hr to the smokers. Testing was done at 24 hr intervals. Sulfur dioxide at 0.3 ppm elicited no functional changes. Sulfur dioxide at 1.0 ppm caused a significant reduction in dynamic compliance measured at 120 breaths/min after 24 and 48 hr of exposure; results of other tests of ventilation and respiratory mechanics were unaffected. The reduction in dynamic compliance was greater and more prolonged with sulfur dioxide at 3.0 ppm. A notable finding was the absence of clear cut evidence of functional changes among the subjects with underlying lung disease. Their intersubject and intrasubject variability far exceeded the variation associated with exposure to all concentrations of sulfur dioxide. A variety of symptoms were noted in both groups: headache, nasal congestion, throat soreness, cough, nosebleed, gastrointestinal discomfort, and rash.
[Weir FW, Bromberg PA; Recent Advances in the Assessment of the Health Effects of Environmental Pollutants 4: 1989-2004 (1974) as cited in National Academy of Sciences; Sulfur Oxides p.157-58 (1978)]**PEER REVIEWED**

40 healthy nonsmokers and 40 subjects with mild asthma /were exposed/ to air and to sulfur dioxide at 0.5 ppm for periods of 3 hr. Forced expiratory performance, closing volume, airway flow resistance, and lung volumes were measured. As a group, the healthy subjects showed no functional changes that could be judged adverse; indeed, vital capacity, maximal volume of gas that can be forcefully exhaled in 1 second after full inspiration, and maximal mid-expiratory flow rate tended to rise with time, whether clean air or sulfur dioxide was administered. The response of the group with asthma to sulfur dioxide was interpreted as showing slight functional impairment; ie, maximal mid-expiratory flow rate was said to increase less to sulfur dioxide than during the sham exposure. The other functional tests were unaffected. Among the healthy subjects, a 13 yr old boy experienced shortness of breath and had functional evidence of bronchoconstriction. On the evening after exposure to sulfur dioxide, two of the asthmatic subjects experienced shortness of breath, which required medication.
[National Academy of Sciences; Sulfur Oxides p.158 (1978)]**PEER REVIEWED**

A combination of 0.37 ppm sulfur dioxide with 0.037 ppm ozone decr the human midexpiratory flow rate to almost half ... .
[Seiler, H.G., H. Sigel and A. Sigel (eds.). Handbook on the Toxicity of Inorganic Compounds. New York, NY: Marcel Dekker, Inc. 1988. 655]**PEER REVIEWED**

The effects of sulfur dioxide on 190 workers employed in a broom manufacturing factory where sulfur dioxide was used for bleaching broom corn were studied. Concentrations of sulfur dioxide in the air, sulfates in the urine, methemoglobin and sulfhemoglobin in the blood, and irritant effects on the workers were analyzed. Measurements were made in summer when open windows provided natural ventilation and in winter when the building was closed. Sulfur dioxide in air averaged 45.7 mg/cu m in winter and 0.2 mg/cu m in summer. When compared to control groups not exposed to sulfur dioxide in the workplace (43 workers checked for methemoglobin and 39 for sulfates), differences in all parameters were statistically significant. In winter the mean values were: total urinary sulfates 21.2 umol/l (p< 0.01), organic urinary sulfates 4.1 umol/l (p< 0.01) methemoglobin 1.6% (p< 0.01), and sulfhemoglobin 0.7% (p< 0.05). In summer the mean values were: total urinary sulfates 19.3 umol/l (p< 0.05), organic urinary sulfates 3.7 umol/l (p< 0.01), methemoglobin 0.7% (p< 0.05), and sulfhemoglobin 0.5% (p< 0.05). Corresponding values for controls were 16.7 umol/l, 1.8 umol/l, 0.5%, and <0.5%, respectively. Interviews with 190 workers revealed the following discomforts: coughing (94.2%), difficulty in breathing (91.0%), burning sensation in throat (83.7%), burning sensation in eyes (80.0%), sub-sternal pain (75.3%), burning sensation in throat (74.7%), sore throat (65.8%), tearing (64.7%), hoarseness (56.3%), pain in nose (49.5%), pain in eyes (39.5%), red eyelids (35.5%), red eyes (16.3%), nose bleeding (3.7%), and sneezing (3.2%).
[Savic M et al; Int Arch Occup Environ Health 59 (5): 513-8 (1987)]**PEER REVIEWED**

Exposures of two miners to sulfur dioxide concentrations of at least 40 ppm resulted in severe airway obstruction, hypoxemia, markedly reduced exercise tolerance, ventilation perfusion mismatch, and evidence of active inflammation as documented by a positive gallium lung scan. Serial ventilation-perfusion scans over the first 12 months showed progressive improvement without returning to normal. This status has remained for 2 years.
[Ellenhorn, M.J., S. Schonwald, G. Ordog, J. Wasserberger. Ellenhorn's Medical Toxicology: Diagnosis and Treatment of Human Poisoning. 2nd ed. Baltimore, MD: Williams and Wilkins, 1997. 1520]**PEER REVIEWED**

A basic physiological response to inhalation of sulfur dioxide is a mild degree of bronchial constriction that is dependent on intact parasympathetic innervation. When exposed to 5 ppm of sulfur dioxide for 10 minutes, most human subjects show increased resistance to the flow of air. Asthmatics have an increased sensitivity to sulfur dioxide; bronchoconstriction may occur at concentrations as low as 0.25 ppm.
[Hardman, J.G., L.E. Limbird, P.B. Molinoff, R.W. Ruddon, A.G. Goodman (eds.). Goodman and Gilman's The Pharmacological Basis of Therapeutics. 9th ed. New York, NY: McGraw-Hill, 1996.,p. 1674-5]**PEER REVIEWED**

... /Authors/ conducted controlled studies in 15 nose-breathing volunteers who inhaled 1, 5, or 25 ppm sulfur dioxide for 6 hr. A significant reduction in nasal mucous flow rate occurred after exposure at 5 and 25 ppm and reduced forced expiratory volume and forced expiratory flow were seen at all exposure concentrations. Irritation and complaints of discomfort were said to be proportional to the sulfur dioxide concentration but were judged never to be excessive. Based on these data, ... /the authors/ expressed the opinion that the TLV for sulfur dioxide should be reduced to 1 ppm or less, given that exposure at 1 ppm from 1 to 6 hours caused constriction of the upper airways in young, healthy (20-28 years of age) adult males. It is important to note that the ... protocol allowed the subjects to become acclimated slowly to the higher concentrations, whereas subjects who had to enter the chamber abruptly found a distinct sulfur dioxide smell at 1 ppm, strong discomfort and cough at 5 ppm, and 25 ppm was intolerable on first contact. These individuals, however, adapted rapidly, and coughing and rhinorrhea resolved within a few minutes.
[American Conference of Governmental Industrial Hygienists, Inc. Documentation of the Threshold Limit Values and Biological Exposure Indices. 6th ed. Volumes I, II, III. Cincinnati, OH: ACGIH, 1991.1456]**PEER REVIEWED**

... /Authors/ found that exposure at 1 ppm sulfur dioxide produced increased flow resistance in 1 of 11 human subjects. A concentration of 5 ppm produced an average increase of 39% compared to the control; the value for 13 ppm was 72% above the control. The response was related to concentration, not to total dose; extending exposure time from 10 minutes to 30 minutes failed to increase the response. Repeated exposure following a 15 minute interval of clean air produced a lesser response than did the initial exposure.
[American Conference of Governmental Industrial Hygienists, Inc. Documentation of the Threshold Limit Values and Biological Exposure Indices. 6th ed. Volumes I, II, III. Cincinnati, OH: ACGIH, 1991.1456]**PEER REVIEWED**

In humans, survivors of massive sulfur dioxide exposure have shown a chronic, obstructive defect in serial pulmonary function studies, along with bronchial hyperreactivity. The extent to which recurrent occupational or environmental exposures to sulfur dioxide produce adverse effects in humans is not clear, however, in part because in both contexts there are usually confounding exposures to particulates or other irritants. Although some investigations suggest that occupational sulfur dioxide exposure (even at levels below the current TLV) is associated with increased upper and lower respiratory symptoms and decrements in various spirometric indices, others have not.
[Sullivan, J.B. Jr., G.R. Krieger (eds.). Hazardous Materials Toxicology-Clinical Principles of Environmental Health. Baltimore, MD: Williams and Wilkins, 1992. 969]**PEER REVIEWED**

Bronchoalveolar lavage of 12 healthy, nonsmoking subjects 24 hours after exposure for 20 minutes to 4 or 8 ppm (10.5 or 21 mg/cu m) sulfur dioxide showed increased alveolar macrophage lysosomal activity; at the higher level, the numbers of macrophages and lymphocytes in the lavage fluid were increased. No effect on lung function was observed.
[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work).p. V54 167 (1992)]**PEER REVIEWED**

The prevalence of chronic bronchitis was significantly increased over that in controls in workers exposed to sulfur dioxide while working in a sulfite pulp factory in Sweden. During the three years before the study was performed, more than 50% of the daily mean values for sulfur dioxide in the sulfite pulp mill were above 14 mg/cu m (5 ppm), with occasional peak exposures up to 140 mg/cu m. The mean annual concentration of sulfur dioxide in the surrounding community was 6.5-40 ug/cu m.
[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work).p. V54 167 (1992)]**PEER REVIEWED**

The frequency of chromosomal aberrations in cultured lymphocytes from seven workers exposed to sulfur dioxide in a sulfite pulp mill in Sweden was compared with that of 15 controls. The exposed subjects had been employed for > 15 years at the mill, and one was a smoker. The controls were healthy men from Umea, Sweden, five of whom were smokers. The mean numbers of breaks/100 cells were 3.72 + or - 0.31 (standard deviations) for the sulfur dioxide exposed workers and 0.66 + or - 0.81 for the controls, analyzed on the basis of individual values (t = 5.79; p < 0.001). The frequency of gaps was also increased in the exposed workers (p < 0.01).
[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work).p. V54 170-1 (1992)]**PEER REVIEWED**

Skin, Eye and Respiratory Irritations:

VAPORS CAUSE SEVERE IRRITATION OF EYES & THROAT ... .
[U.S. Coast Guard, Department of Transportation. CHRIS - Hazardous Chemical Data. Volume II. Washington, D.C.: U.S. Government Printing Office, 1984-5.]**PEER REVIEWED**

... Strong irritant to eyes & mucous membranes ... .
[Sax, N.I. and R.J. Lewis, Sr. (eds.). Hawley's Condensed Chemical Dictionary. 11th ed. New York: Van Nostrand Reinhold Co., 1987. 1107]**PEER REVIEWED**

Irritating to ... resp system & skin.
[Commission of the European Communities. Legislation on Dangerous Substances - Classification and Labelling in the European Communities. Vol. II. London and Trotman Ltd., 1989. 138]**PEER REVIEWED**

HAZARD WARNING: Because of the high solubility of sulfur dioxide, it is extremely irritating to the eyes and upper respiratory tract.
[Sullivan, J.B. Jr., G.R. Krieger (eds.). Hazardous Materials Toxicology-Clinical Principles of Environmental Health. Baltimore, MD: Williams and Wilkins, 1992. 969]**PEER REVIEWED**

Medical Surveillance:

Preplacement and annual medical examinations should be done whenever TWA exposures exceed 0.25 ppm (0.65 mg/cu m). These examinations should be directed toward complaints of mucous membrane irritation, cough and shortness of breath. They should ascertain that nasal passages are open. Persons with a history of asthma or with subnormal pulmonary function should be watched closely. Simple expiratory function tests should be a part of the examination. They are useful for several purposes: (a) determining whether or not a person is a suitable candidate for using respirators; (b) identifying "reactors", ie, persons who may be most susceptible to the effects of SO2. This can be done by comparing preshift and postshift tests; (c) when done periodically, they can be used to determine whether or not a person's expiratory functions are declining at a faster than normal rate. Such determinations are much more sensitive when pooled data from a number of individuals are used. The forced expiratory volume at 1 second and the maximum mid-expiratory flow rate appear to be the most useful of the simple pulmonary function tests.
[OSHA; Public Hearing on Occupational Standard for Sulfur Dioxide: Statement of Edward Baier (NIOSH) (May 1977) PB 83-182485]**PEER REVIEWED**

PERSONS TO BE EMPLOYED ON WORK WHERE THERE MAY BE EXPOSURE TO SULFUR DIOXIDE SHOULD RECEIVE PREEMPLOYMENT MEDICAL EXAMINATION: PERSONS SUFFERING FROM CHRONIC CONJUNCTIVITIS OR LARYNGITIS, BRONCHITIS, EMPHYSEMA, BRONCHIAL ASTHMA, ANY DISORDER INHIBITING NASAL RESP, OR ANY CARDIOVASCULAR DISEASE MUST BE ADEQUATELY EXPOSED TO THIS SUBSTANCE.
[International Labour Office. Encyclopedia of Occupational Health and Safety. Vols. I&II. Geneva, Switzerland: International Labour Office, 1983. 2123]**PEER REVIEWED**

Populations at Special Risk:

Persons with a history of asthma or with subnormal pulmonary function should be watched closely ... .
[OSHA; Public Hearing on Occupational Standard for Sulfur Dioxide: Statement of Edward Baier (NIOSH) (May 1977) PB 83-182485]**PEER REVIEWED**

Clear cut evidence has ... been obtained that asthmatic individuals are especially sensitive to sulfur dioxide. ... The degree of sensitivity to Sulfur dioxide appears to depend on the magnitude of preexisting airway hypersensitivity.
[Doull, J., C.D.Klassen, and M.D. Amdur (eds.). Casarett and Doull's Toxicology. 3rd ed., New York: Macmillan Co., Inc., 1986. 807]**PEER REVIEWED**

Persons suffering from ... any ... cardiovascular disease should be adequately protected to this substance.
[International Labour Office. Encyclopedia of Occupational Health and Safety. Vols. I&II. Geneva, Switzerland: International Labour Office, 1983. 2123]**PEER REVIEWED**

In high-exposure communities (community mean specific sulfur dioxide level of 45 ug/cu m over 5 yr), smokers and nonsmokers had a higher incidence or persistent cough and sputum production compared with controls in low-exposure communities. Smoking remained the most important variable of the prevalence of persistent cough and sputum production.
[Ellenhorn, M.J., S. Schonwald, G. Ordog, J. Wasserberger. Ellenhorn's Medical Toxicology: Diagnosis and Treatment of Human Poisoning. 2nd ed. Baltimore, MD: Williams and Wilkins, 1997. 1461]**PEER REVIEWED**

PERSONS SUFFERING FROM CHRONIC CONJUNCTIVITIS OR LARYNGITIS, BRONCHITIS, EMPHYSEMA, BRONCHIAL ASTHMA, ANY DISORDER INHIBITING NASAL RESP, OR ANY CARDIOVASCULAR DISEASE SHOULD NOT BE EXPOSED TO THIS SUBSTANCE.
[International Labour Office. Encyclopedia of Occupational Health and Safety. Vols. I&II. Geneva, Switzerland: International Labour Office, 1983. 2123]**PEER REVIEWED**

Probable Routes of Human Exposure:

Inhalation ... /or/ direct contact of gas or liquid phase on ... mucous membranes.
[Sittig, M. Handbook of Toxic and Hazardous Chemicals and Carcinogens, 1985. 2nd ed. Park Ridge, NJ: Noyes Data Corporation, 1985. 813]**PEER REVIEWED**

It has been estimated by the Department of Labor that approx 600,000 American workers may be occupationally exposed to sulphur dioxide. Some of the highest exposures occur when it is a by product, as in the metal smelting industry, and in the processing or combustion of high sulfur coal or oil. Other exposures occur in manufacture of sulfuric acid, fumigating, food preservation, wine making, and bleaching of many substances.
[OSHA; Public Hearing on Occupational Standard for Sulfur Dioxide: Statement of Edward Baier (NIOSH) (May 1977) PB 83-182485]**PEER REVIEWED**

Emergency Medical Treatment:

Emergency Medical Treatment:

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The following Overview, *** SULFUR DIOXIDE ***, is relevant for this HSDB record chemical.

Life Support:
   o   This overview assumes that basic life support measures
       have been instituted.
Clinical Effects:
  0.2.1 SUMMARY OF EXPOSURE
   0.2.1.1 ACUTE EXPOSURE
     A)  Sulfur dioxide is classified as an irritant gas; it
         produces immediate and severe irritant effects after
         exposure. It is extremely irritating to skin and eyes
         and to the mucosa of the nasopharynx and respiratory
         tract.
     B)  Inhalation produces choking, coughing, sneezing,
         rhinorrhea, wheezing, dyspnea, cyanosis, chest pain,
         tracheitis, bronchitis, nausea, vomiting, fatigue,
         bronchoconstriction, pneumonitis, laryngeal/glottal
         edema, upper airway edema or obstruction and increased
         airflow resistance; death may result from pulmonary
         edema, systemic acidosis or respiratory arrest.
     C)  Exposure to levels of 400 to 500 ppm is considered
         immediately life-threatening. Obstructive and
         restrictive lung disease, reactive airway disease
         syndrome (RADS), or chronic bronchitis may develop in
         victims who survive exposure to high concentrations.
         RADS may persist for months to years after exposure.
         Asthmatics are particularly sensitive to the
         respiratory effects of sulfur dioxide.
     D)  Sulfur dioxide is a corrosive irritant of the skin and
         eyes, although actual eye injury from the gas is rare.
         It causes smarting of the eyes, lacrimation and
         conjunctival irritation. Contact with moist skin
         produces increased adverse dermal effects. Serious skin
         and eye frostbite injury or burns may result from
         direct contact with liquefied sulfur dioxide. Corneal
         opacity, erosion or necrosis and ultimately blindness
         are possible consequences of eye exposure. Frostbite
         and chemical burns to the mouth can occur.
  0.2.4 HEENT
   0.2.4.1 ACUTE EXPOSURE
     A)  Eye irritation may occur. Severe corneal damage has
         been reported after direct contact with liquefied
         sulfur dioxide.
     B)  Irritation of the nose, nasopharynx, and glottis is
         common. Glottic edema may cause upper airway
         obstruction. Loss of sensation of smell has been
         reported.
  0.2.6 RESPIRATORY
   0.2.6.1 ACUTE EXPOSURE
     A)  Cough, dyspnea, chest discomfort, bronchoconstriction,
         cyanosis, and pulmonary edema may occur. Pneumonia is a
         common complication. Victims surviving a serious
         inhalation injury may develop reactive airway disease,
         obstructive and restrictive lung disease, or chronic
         bronchitis.
   0.2.6.2 CHRONIC EXPOSURE
     A)  Sulfur dioxide is an important air pollutant with
         multiple chronic health effects.
  0.2.8 GASTROINTESTINAL
   0.2.8.1 ACUTE EXPOSURE
     A)  Nausea, vomiting, and abdominal pain have been
         reported.
  0.2.14 DERMATOLOGIC
   0.2.14.1 ACUTE EXPOSURE
     A)  Direct contact with liquefied sulfur dioxide could
         cause frostbite injury.
  0.2.20 REPRODUCTIVE HAZARDS
    A)  Maternal toxicity and embryotoxicity have been observed.
  0.2.21 CARCINOGENICITY
   0.2.21.1 IARC CATEGORY
     A)  IARC Carcinogenicity Ratings for CAS7446-09-5 (IARC,
         2004):
      1)  IARC Classification
       a)  Listed as: Sulfur dioxide
       b)  Carcinogen Rating: 3
        1)  The agent (mixture or exposure circumstance) is not
            classifiable as to its carcinogenicity to humans.
            This category is used most commonly for agents,
            mixtures and exposure circumstances for which the
            evidence of carcinogenicity is inadequate in humans
            and inadequate or limited in experimental animals.
            Exceptionally, agents (mixtures) for which the
            evidence of carcinogenicity is inadequate in humans
            but sufficient in experimental animals may be placed
            in this category when there is strong evidence that
            the mechanism of carcinogenicity in experimental
            animals does not operate in humans. Agents, mixtures
            and exposure circumstances that do not fall into any
            other group are also placed in this category.
   0.2.21.2 HUMAN OVERVIEW
     A)  A higher incidence of respiratory cancer may be
         observed with exposure to sulfur dioxide and other
         agents in combination.
  0.2.22 GENOTOXICITY
    A)  Genotoxic effects of sulfur dioxide have been
        demonstrated in occupationally exposed humans and in
        various animal and in-vitro systems.
Laboratory:
   A)  Baseline chest x-ray and arterial blood gases or pulse
       oximetry should be obtained in patients with respiratory
       signs following significant inhalation exposure.
Treatment Overview:
  0.4.3 INHALATION EXPOSURE
    A)  INHALATION: Move patient to fresh air. Monitor for
        respiratory distress. If cough or difficulty breathing
        develops, evaluate for respiratory tract irritation,
        bronchitis, or pneumonitis. Administer oxygen and assist
        ventilation as required. Treat bronchospasm with inhaled
        beta2 agonist and oral or parenteral corticosteroids.
    B)  Administer 100% supplemental humidified oxygen with
        assisted ventilation as required.
    C)  Endotracheal intubation, cricothyroidotomy, or
        tracheostomy may be needed if upper airway obstruction
        occurs.
    D)  Inhaled sympathomimetic bronchodilators may be useful to
        treat bronchospasm.
    E)  Steroid use is controversial. Antibiotics may be useful
        for pulmonary infectious complications.
    F)  ACUTE LUNG INJURY: Maintain ventilation and oxygenation
        and evaluate with frequent arterial blood gas or pulse
        oximetry monitoring. Early use of PEEP and mechanical
        ventilation may be needed.
  0.4.4 EYE EXPOSURE
    A)  DECONTAMINATION: Irrigate exposed eyes with copious
        amounts of room temperature water for at least 15
        minutes. If irritation, pain, swelling, lacrimation, or
        photophobia persist, the patient should be seen in a
        health care facility.
  0.4.5 DERMAL EXPOSURE
    A)  OVERVIEW
     1)  Rewarming and a variety of topical treatments are
         indicated for frostbite injury. SEE MAIN TREATMENT
         SECTION FOR MORE INFORMATION.
Range of Toxicity:
   A)  The minimum lethal human exposure is an airborne
       concentration of 400 ppm for 1 minute. An odor or taste
       is noticed at airborne concentrations of 3 to 5 ppm,
       throat and conjunctival irritation and lacrimation begin
       at 8 to 12 ppm, and become severe at 50 ppm.
MONOBASIC

[Rumack BH POISINDEX(R) Information System Micromedex, Inc., Englewood, CO, 2004; CCIS Volume 122, edition expires Nov, 2004. Hall AH & Rumack BH (Eds): TOMES(R) Information System Micromedex, Inc., Englewood, CO, 2004; CCIS Volume 122, edition expires Nov, 2004.]**PEER REVIEWED**

Antidote and Emergency Treatment:

For basic treatment: Establish a patent airway. Suction if necessary. Watch for signs of respiratory insufficiency and assist ventilations if necessary. Administer oxygen by nonrebreather mask at 10 to 15 L/min. Monitor for pulmonary edema and treat if necessary. Anticipate seizures and treat if necessary. Monitor for shock and treat if necessary. For eye contamination, flush eyes immediately with water. Irrigate each eye continuously with normal saline during transport. Do not use emetics. For ingestion, rinse mouth and administer 5 ml/kg up to 200 ml of water for dilution if the patient can swallow, has a strong gag reflex, and does not drool. Administer activated charcoal. Cover skin burns with sterile dressings after decontamination.
[Bronstein, A.C., P.L. Currance; Emergency Care for Hazardous Materials Exposure. 2nd ed. St. Louis, MO. Mosby Lifeline. 1994. 105]**PEER REVIEWED**

For advanced treatment: Consider orotracheal or nasotracheal intubation for airway control in the patient who is unconscious. Early intubation at the first sign of upper airway obstruction may be necessary. Monitor cardiac rhythm and treat arrhythmias if necessary. Start an IV with D5W TKO. Use lactated Ringer's if signs of hypovolemia are present. Watch for signs of fluid overload. Consider drug therapy for pulmonary edema. Treat seizures with diazepam (Valium). For hypotension with signs of hypovolemia, administer fluid cautiously. Consider vasopressors for hypotension with a normal fluid volume. Watch for signs of fluid overload. Use proparacaine hydrochloride to assist eye irrigation.
[Bronstein, A.C., P.L. Currance; Emergency Care for Hazardous Materials Exposure. 2nd ed. St. Louis, MO. Mosby Lifeline. 1994. 106]**PEER REVIEWED**

Animal Toxicity Studies:

Evidence for Carcinogenicity:

Evaluation: There is inadequate evidence for the carcinogenicity in humans of sulfur dioxide, sulfites, bisulfites and metabisulfites. There is limited evidence for the carcinogenicity in experimental animals of sulfur dioxide. There is inadequate evidence for the carcinogenicity in experimental animals of sulfites, bisulfites and metabisulfites. Overall evaluation: Sulfur dioxide, sulfites, bisulfites and metabisulfites are not classifiable as to their carcinogenicity to humans (Group 3).
[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work).p. 54 178 (1992)]**PEER REVIEWED**

A4; Not classifiable as a human carcinogen.
[American Conference of Governmental Industrial Hygienists. TLVs & BEIs: Threshold limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices for 2002. Cincinnati, OH. 2002.54]**QC REVIEWED**

Non-Human Toxicity Excerpts:

POISONING IN CATTLE ... /AT/ A DAILY DOSE OF 80-160 G OF ... SULFUR DIOXIDE GAS CAUSED ANOREXIA: MASSIVE DOSES ADMIN THROUGH RUMEN FISTULAE WERE FATAL. ... MORE SEVERE TISSUE CHANGES WERE CONFINED TO THE FIRST PART OF THE DIGESTIVE TRACT: MOST CONSISTENT LESIONS WERE IN THE LARYNX & IN THE MUCOSA OF THE VENTRAL WALL OF THE TRACHEA.
[Clarke, M. L., D. G. Harvey and D. J. Humphreys. Veterinary Toxicology. 2nd ed. London: Bailliere Tindall, 1981. 84]**PEER REVIEWED**

... SULFUR DIOXIDE POISONING IN A HORSE FOLLOWING BRIEF PERIOD OF EXPOSURE TO THE GAS ... /PRODUCED/ SEVERE RESPIRATORY & CIRCULATORY DISTURBANCES ... SEVERE IRRITATION OF NASAL & PLEURAL MUCOUS MEMBRANES WAS OBSERVED POST MORTEM. ... PIGS EXPOSED TO CONCN OF 5 TO 40 PPM FOR 8 HR SHOWED CLINICAL EVIDENCE OF EYE & RESPIRATORY TRACT IRRITATION, & PULMONARY HEMORRHAGE & EMPHYSEMA ... .
[Clarke, M. L., D. G. Harvey and D. J. Humphreys. Veterinary Toxicology. 2nd ed. London: Bailliere Tindall, 1981. 83]**PEER REVIEWED**

... 200 PPM ARE REQUIRED TO SLOW CILIA OF RABBIT TRACHEA IN VIVO; ONLY 7 PPM ARE REQUIRED FOR ISOLATED RABBIT TRACHEA.
[Thienes, C., and T.J. Haley. Clinical Toxicology. 5th ed. Philadelphia: Lea and Febiger, 1972. 198]**PEER REVIEWED**

... SLIGHT INCREASE IN PULMONARY FLOW RESISTANCE IN GUINEA PIGS @ 0.16 PPM; THE INCR WAS DOUBLED @ 2.6 PPM, BUT ONLY SLIGHTLY MORE @ 19 PPM.
[American Conference of Governmental Industrial Hygienists. Documentation of the Threshold Limit Values for Substances in Workroom Air. Third Edition, 1971. Cincinnati, Ohio: American Conference of Governmental Industrial Hygienists, 1971. (Plus supplements to 1979)238]**PEER REVIEWED**

... MOST ANIMALS SURVIVE EXPOSURES OF 1 TO 5 HR @ 400 PPM, BUT DEATHS RESULTED FROM 600 TO 800 PPM IN SOME SPECIES.
[American Conference of Governmental Industrial Hygienists. Documentation of the Threshold Limit Values for Substances in Workroom Air. Third Edition, 1971. Cincinnati, Ohio: American Conference of Governmental Industrial Hygienists, 1971. (Plus supplements to 1979)238]**PEER REVIEWED**

... INFLUENZA-INFECTED MICE EXPOSED TO SULFUR DIOXIDE DEVELOPED MORE PNEUMONIA THAN VIRUS CONTROLLED MICE. ... INCR IN PNEUMONIA WAS DUE TO ... INDUCED LOW-GRADE INFLAMMATORY CHANGES IN LUNGS.
[Hamilton, A., and H. L. Hardy. Industrial Toxicology. 3rd ed. Acton, Mass.: Publishing Sciences Group, Inc., 1974. 211]**PEER REVIEWED**

... RATS /WERE GIVEN/ SULFUR DIOXIDE AT ... 750 PPM IN DRINKING WATER EXPERIMENTS THAT LASTED NEARLY 3 YR WITH 3 GENERATIONS OF ANIMALS. ... /IT WAS/ REPORTED /THAT/ NO EFFECTS ON GROWTH, INTAKE OF FOOD & FLUID, OUTPUT OF FECES, FERTILITY, WEIGHT OF NEWBORN OR FREQUENCY OF TUMOR DEVELOPMENT.
[Furia, T.E. (ed.). CRC Handbook of Food Additives. 2nd ed. Cleveland: The Chemical Rubber Co., 1972. 144]**PEER REVIEWED**

Eye irritation occurs at 6 ppm/4 hr in the rabbit.
[Seiler, H.G., H. Sigel and A. Sigel (eds.). Handbook on the Toxicity of Inorganic Compounds. New York, NY: Marcel Dekker, Inc. 1988. 650]**PEER REVIEWED**

WHEN WHOLE ANIMAL HAS BEEN EXPOSED, KERATITIS & CORNEAL CLOUDING IN RABBITS & GUINEA PIGS HAVE OCCURRED ONLY UNDER CONDITIONS OF TIME & CONCN WHICH HAVE ULTIMATELY BEEN LETHAL (460 TO 490 PPM FOR 30 HR OR 800 TO 1000 PPM FOR 24 HR).
[Grant, W.M. Toxicology of the Eye. 3rd ed. Springfield, IL: Charles C. Thomas Publisher, 1986. 863]**PEER REVIEWED**

Dogs exposed to 500-600 ppm (1300-1560 mg/cu m) for 2 hr periods twice weekly for 4 to 5 mo showed an incr in goblet cells near the ends of bronchi and bronchioles, and hyperplasia of bronchial glands, with an excess of mucopurulent exudate. ... /It was/ concluded that sulfur dioxide produces chronic bronchitis in dogs.
[Chakrin LW, Saunders LZ; Lab Invest 30: 145 (1974) as cited in OSHA; Public Hearing on Occupational Standard for Sulfur Dioxide: Statement of Edward Baier (NIOSH) (May 1977) PB 83-182485]**PEER REVIEWED**

... Green plants are extremely sensitive to atmospheric sulfur dioxide. Alfalfa, barley, cotton, and wheat can be injured at levels between 0.15 and 0.20 ppm, while potatoes, onions, and corn are far more resistant.
[Seiler, H.G., H. Sigel and A. Sigel (eds.). Handbook on the Toxicity of Inorganic Compounds. New York, NY: Marcel Dekker, Inc. 1988. 654]**PEER REVIEWED**

Exposure of Euglena cells to 5.0 ppm of sulfur dioxide increased the concentration of chlorophyll but reduced the rate of photosynthesis.
[De Koning HW, Jegier Z; Atmos Enviorn 4 (4): 357-61 (1970) as cited in Nat'l Research Council Canada; Sulfur and its Inorganic Derivatives in the Canadian Environment p.271 (1977) NRCC No.15015]**PEER REVIEWED**

Cynomolgus monkeys exposed continuously for 78 weeks to sulfur dioxide levels up to 3.7 mg/cu m (1.3 ppm) did not show any significant pathological changes.
[Alarie Y et al; Arch Environ Health 27: 16-24 (1973) as cited in WHO; Environ Health Criteria: Sulfur Oxides and Suspended Particulate Matter p.56 (1979)]**PEER REVIEWED**

Cynomolgus monkeys and guinea pigs were exposed to mixtures of sulfur dioxide, fly ash, and sulfuric acid mist, were studied for 18 months after an 8 week baseline period. Exposure concentrations varied from ... 0.1 to 5.0 ppm for sulfur dioxide and from 0.1 to 1 mg/cu m for sulfuric acid mist; the concentration of fly ash was approximately 0.5 mg/cu m. Particle size (MMD) varied from 0.53 to 3.11 um in the acid mist and from 4.1 to 5.8 um in the fly ash. Pulmonary function tests and serumbiochemcial and hematological analyses were conducted prior to, and periodically during, the exposure. Lungs were examined microscopically at the end of the experiment. Sulfuric acid mist appeared to be responsible for the effects observed. These were largly histopathological changes in the lungs. No synergistic action was noted between the pollutants.
[Alarie Y et al; Arch Environ Health 30: 254-62 (1975) as cited in WHO; Environ Health Criteria: Sulfur Oxides and Suspended Particulate Matter p.57 (1979)]**PEER REVIEWED**

Rats were exposed for 96 days to sulfur dioxide at concentrations of 0.1, 0.5, and 1.5 mg/cu m (0.04, 0.18 & 0.53 ppm). Histological examination showed interstitial pneumonia, bronchitis, tracheitis, and peribronchitis after exposures to the two higher levels.
[Elfimova EV, Gusev MI; Gig I Sanit 34 (2): 3-7 (1969) as cited in WHO; Environ Health Criteria: Sulfur Oxides and Suspended Particulate Matter p.55 (1979)]**PEER REVIEWED**

Beagle dogs exposed to a sulfur dioxide concentration of 13.4 mg/cu m (4.7 ppm) for 21 hr per day, for 620 days did not develop any specific histopathological changes.
[Lewis TR et al; Arch Environ Health 26: 16-21 (1973) as cited in WHO; Environ Health Criteria: Sulfur Oxides and Suspended Particulate Matter p.56 (1979)]**PEER REVIEWED**

... 16 to 19 ppm of sulfur dioxide killed sunfish in 1 hour. ... Concentrations of 10 ppm of sulfur dioxide in tap water caused trout to float within 10 minutes and also reports that 5 ppm of sulfur dioxide killed trout in 1 hour.
[Nat'l Research Council Canada; Sulfur and its Inorganic Derivatives in the Canadian Environment p.270 (1977) NRCC No. 15015]**PEER REVIEWED**

When rabbits inhaled 300 ppm of sulfur dioxide, ciliary action in the upper airways was inhibited, and at 400 ppm, mucosal irritation, mucous gland hypertrophy, and proliferation of pulmonary goblet cells occurred.
[American Conference of Governmental Industrial Hygienists, Inc. Documentation of the Threshold Limit Values and Biological Exposure Indices. 6th ed. Volumes I, II, III. Cincinnati, OH: ACGIH, 1991.1455]**PEER REVIEWED**

Studies in intact rodents have failed consistently to induce genotoxicity.
[American Conference of Governmental Industrial Hygienists, Inc. Documentation of the Threshold Limit Values and Biological Exposure Indices. 6th ed. Volumes I, II, III. Cincinnati, OH: ACGIH, 1991.1455]**PEER REVIEWED**

Prolonged exposure of dogs to high concentrations of sulfur dioxide (200 ppm) causes a syndrome similar to human chronic bronchitis, involving chronic airway obstruction, airway inflammation, and symptoms of cough and mucus hypersecretion. However, unlike human disease, in this animal model there is decreased airway responsiveness to inhaled bronchoconstrictor agents, which appears to be associated with chronic airway inflammation. When exposed to 15 ppm using the same experimental protocol, none of these effects is evident. With few exceptions, chronic exposure of animals to sulfur dioxide does not produce observable adverse effects at concentrations lower than 20 ppm.
[Sullivan, J.B. Jr., G.R. Krieger (eds.). Hazardous Materials Toxicology-Clinical Principles of Environmental Health. Baltimore, MD: Williams and Wilkins, 1992. 969]**PEER REVIEWED**

Groups of 10 female albino rats (weighing 165-185 g) were exposed for 12 hours per day for three months to 0, 0.159 or 4.97 mg/ cu m sulfur dioxide. An additional group was exposed to 2.52 mg/cu m sulfur dioxide in combination with 1.20 mg/cu nitrogen dioxide. Oestrus cyclicity was determined for 24 days prior to exposure, during exposure and during a recovery period. Females with a normal oestrus cycle were tested for fertility. The ovaries, uterus and pituitary, thyroid and adrenal glands from four rats per group were examined by histopathology at the end of exposure. It was reported that the higher exposure level prolonged the interestrual period (dioestrus) and the oestrus and that these females had fewer monthly oestrus cycles. Cycle length returned to normal within seven months after exposure. Circulatory changes were found in the ovaries and uteri of females in the high exposure group. In a second experiment, decreased litter sizes were found in similarly exposed groups of seven females. Body weights of the offspring were reduced at least through postnatal day 12 in these groups.
[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work).p. V54 168 (1992)]**PEER REVIEWED**

An experimental group of 35 male and 30 female LX mice and a control group of 41 males and 39 females, three months old, were exposed to 0 or 500 ppm (1310 mg/cu m) sulfur dioxide (purity unspecified) for 5 min per day on five days a week for life. Only mice that survived for 300 days or more were considered in the results (average survival time not shown), since lung tumors were not seen before that time. Female mice exposed to sulfur dioxide had an increased incidence of lung tumors: 13/30 adenomas and carcinomas versus 5/30 in controls, (p= 0.02; Peto@@s incidental test); 4/30 lung carcinomas versus none in the controls. The incidence of lung neoplasias was higher in treated males (15/28 versus 11/35 in controls), but the difference was not significant; lung carcinomas occurred with equal frequency in treated and control males (2/28 and 2/35).
[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work).p. V54 162 (1992)]**PEER REVIEWED**

Groups of 40 or 32 CF-1 mice were exposed for 7 hours per day to filtered air or to sulfur dioxide (purity, 99.98%) at 25 ppm (66 mg/cu m) on days 6-15 of gestation, and groups of 20 New Zealand white rabbits were exposed to filtered air or sulfur dioxide at 70 ppm (183 mg/cu m) on days 6-18 of gestation. In both species, less food was consumed during the first few days of exposure to sulfur dioxide; no other significant effect was seen in the dams. In mice, fetal weight was reduced by 5% by exposure to sulfur dioxide; ossification of the sternebrae and occipital was retarded (data not shown), but the incidence of malformations was not significantly increased. In rabbits, the incidence of a few minor skeletal variants was significantly increased (data not shown) in group exposed to sulfur dioxide.
[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work).p. V54 168 (1992)]**PEER REVIEWED**

Non-Human Toxicity Values:

LC50 Mice inhalation 150 ppm/847 hr
[American Conference of Governmental Industrial Hygienists, Inc. Documentation of the Threshold Limit Values and Biological Exposure Indices. 6th ed. Volumes I, II, III. Cincinnati, OH: ACGIH, 1991.1455]**PEER REVIEWED**

LC50 Guinea pig inhalation 1000 ppm/20 hr
[American Conference of Governmental Industrial Hygienists, Inc. Documentation of the Threshold Limit Values and Biological Exposure Indices. 6th ed. Volumes I, II, III. Cincinnati, OH: ACGIH, 1991.1455]**PEER REVIEWED**

LC50 Mouse inhalation 1000 ppm/4 hr
[American Conference of Governmental Industrial Hygienists, Inc. Documentation of the Threshold Limit Values and Biological Exposure Indices. 6th ed. Volumes I, II, III. Cincinnati, OH: ACGIH, 1991.1455]**PEER REVIEWED**

LC50 Guinea pig inhalation 130 ppm/154 hr
[American Conference of Governmental Industrial Hygienists, Inc. Documentation of the Threshold Limit Values and Biological Exposure Indices. 6th ed. Volumes I, II, III. Cincinnati, OH: ACGIH, 1991.1455]**PEER REVIEWED**

Metabolism/Pharmacokinetics:

Metabolism/Metabolites:

Once absorbed, sulfur dioxide appears to be metabolized rapidly to sulfate by the widely distributed enzyme sulfite oxidase. After it has been oxidized to sulfate, it becomes part of the large sulfate pool within the body. /It was reported/ relatively large differences in sulfite oxidase activity among five species: rats had the highest levels and rabbits the lowest. An inverse correlation was shown between enzyme activity and sensitivity to bisulfite toxicity. These results reflect species differences in rate of S-sulfonate formation.
[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work).p. V54 166 (1992)]**PEER REVIEWED**

Absorption, Distribution & Excretion:

BLOOD (35)SULFUR LEVELS ROSE WHILE DOGS WERE EXPOSED TO (35)SULFUR DIOXIDE ... PROTEIN BOUND (35)SULFUR, ACCOUNTING FOR LESS THAN 50% OF PLASMA (35)SULFUR, WAS ASSOCIATED MORE WITH ALPHA-GLOBULINS THAN WITH OTHER PROTEINS. URINARY (35)SULFUR WAS MAINLY (35)SULFATE ION.
[The Chemical Society. Foreign Compound Metabolism in Mammals. Volume 2: A Review of the Literature Published Between 1970 and 1971. London: The Chemical Society, 1972. 158]**PEER REVIEWED**

INHALED SULFUR DIOXIDE IS ONLY SLOWLY REMOVED FROM THE RESP TRACT. RADIOACTIVITY CAN BE DETECTED IN THE RESP SYSTEM FOR WK OR MORE FOLLOWING EXPOSURE. SOME OF THE (35)SULFUR APPEARS TO BE ATTACHED TO PROTEIN.
[Doull, J., C.D.Klassen, and M.D. Amdur (eds.). Casarett and Doull's Toxicology. 3rd ed., New York: Macmillan Co., Inc., 1986. 805]**PEER REVIEWED**

IT MAY ENTER THE BODY VIA RESP TRACT OR, FOLLOWING DILUTION IN SALIVA, IT MAY BE SWALLOWED & ENTER GASTROINTESTINAL TRACT IN FORM OF SULFUROUS ACID. ... /SOME STUDIES INDICATE THAT/ IT CAN ENTER THE BODY VIA SKIN. DUE TO ITS HIGH SOLUBILITY, SULFUR DIOXIDE IS RAPIDLY DISTRIBUTED THROUGHOUT THE BODY ... IN THE BLOOD, SULFURIC ACID IS METABOLIZED TO SULFATES WHICH ARE EXCRETED IN THE URINE.
[International Labour Office. Encyclopedia of Occupational Health and Safety. Vols. I&II. Geneva, Switzerland: International Labour Office, 1983. 2122]**PEER REVIEWED**

By the use of (35)sulfur dioxide ... the absorption /of sulfur dioxide/ by the upper respiratory tract of rabbits over a concn range of 0.05 to 700 ppm /was examined/. At higher concn removal was 90.0% or greater; this is in agreement with the findings of other workers on dogs and human subjects. At concn below 1 ppm, however, only 5.0% or less was removed by the upper resp tract. ... The penetration of sulfur dioxide to the lungs is greater during mouth breathing than during nose breathing. In dogs breathing orally, 99.0% of 1 ppm was removed orally at a flow rate of 3.5 l/min. Increasing the flow rate tenfold decreased the removal efficiency to 33.0%. ... Studies using (35)sulfur dioxide have shown that inhaled sulfur dioxide is readily distributed throughout the body.
[Doull, J., C.D.Klassen, and M.D. Amdur (eds.). Casarett and Doull's Toxicology. 3rd ed., New York: Macmillan Co., Inc., 1986. 805]**PEER REVIEWED**

Most studies on both man and animals have indicated that 40 to 90% or more of inhaled sulfur dioxide is absorbed in the upper respiratory tract. Taken into the blood stream, it appears to be widely distributed throughout the body, metabolized, and excreted via the urinary tract.
[WHO; Environ Health Criteria: Sulfur Oxides and Suspended Particulate Matter p.12 (1979)]**PEER REVIEWED**

Sulfur dioxide is highly soluble in aqueous media. Absorption after inhalation has been studied in rabbits and man. In rabbits, about 40% of the inhaled sulfur dioxide is absorbed in the nose and pharynx when concentrations of about 290 ug/cu m (0.1 ppm) are inhaled. At higher concentrations (29-290 mg/cu m, 10-100 ppm), the fraction absorbed is much higher (about 95%). The reasons for these different rates of absorption are not clear. In dogs, more than 99% of the inhaled sulfur dioxide is absorbed by the nose at exposure levels of 2.9-140 mg/cum (1-50 ppm).
[WHO; Environ Health Criteria: Sulfur Oxides and Suspended Particulate Matter p.50 (1979)]**PEER REVIEWED**

Sulfur dioxide is soluble in water and thus tends to be efficiently absorbed in the upper respiratory tract. Two factors affecting the efficiency of absorption are the mode of breathing (oral versus oronasal) and ventilation rate. The nose filters out most inhaled sulfur dioxide, preventing its passage to sensitive irritant receptors at and below the larynx. At rest, most people (about 85%) breathe through the nose, providing protection against sulfur dioxide toxicity. Mouth breathing, particularly at higher airflow rates, substantially increases the fraction of sulfur dioxide reaching the lung. Thus, voluntary hyperventilation or exercise at a level of exertion requiring oronasal breathing lowers the threshold for sulfur dioxide-induced respiratory symptoms and bronchomotor responsiveness. Deep lung penetration and toxicity are enhanced by oxidation and adsorption to submicron acidic particles.
[Sullivan, J.B. Jr., G.R. Krieger (eds.). Hazardous Materials Toxicology-Clinical Principles of Environmental Health. Baltimore, MD: Williams and Wilkins, 1992. 968]**PEER REVIEWED**

Radiolabeled sulfur dioxide is absorbed from the respiratory tract of experimental animals in the blood and is distributed throughout the body, concentrating in the liver, spleen, esophagus, and kidneys. It is metabolized to a variety of sulfur-containing compounds and is excreted principally via the urine as sulfate. Significant quantities of sulfur dioxide may be retained for a week or more in the lungs and trachea of experimental animals.
[Sullivan, J.B. Jr., G.R. Krieger (eds.). Hazardous Materials Toxicology-Clinical Principles of Environmental Health. Baltimore, MD: Williams and Wilkins, 1992. 969]**PEER REVIEWED**

Mechanism of Action:

On contact with moist mucous membranes, sulfur dioxide produces sulfurous acid, which is a direct irritant and inhibits mucociliary transport. ... Most of the inhaled sulfur dioxide is detoxified by the liver through the molybdenum-dependent, sulfite oxidase pathway to sulfates. The irritant induced stimulation of airway sensory end organs causes vagal stimulation and airway smooth muscle contraction.
[Ellenhorn, M.J. and D.G. Barceloux. Medical Toxicology - Diagnosis and Treatment of Human Poisoning. New York, NY: Elsevier Science Publishing Co., Inc. 1988. 874]**PEER REVIEWED**

Interactions:

AEROSOLS THAT HAVE PRODUCED ... POTENTIATION OF RESPONSE TO SULFUR DIOXIDE ARE SOLUBLE SALTS OF SUCH METALS AS MANGANESE, FERROUS IRON, & VANADIUM. ... THESE AEROSOLS POTENTIATE RESPONSE ABOUT THREE FOLD WHEN PRESENT AT CONCN OF 1 MG/CU M @ 50% RELATIVE HUMIDITY.
[Doull, J., C.D.Klassen, and M.D. Amdur (eds.). Casarett and Doull's Toxicology. 3rd ed., New York: Macmillan Co., Inc., 1986. 811]**PEER REVIEWED**

Sulfur dioxide increases the carcinogenicity of benzopyrene by promoting its metabolism.
[Warshawsky D, et al; EPA Catalysts' Research Program's Sulfuric Acid Research Review Conference; Influence of Particulate and SO2 on Benzo(a)pyrene Metabolism (1977) as cited in OSHA; Public Hearing on Occupational Standard for Sulfur Dioxide: Statement of Edward Baier (NIOSH) (May 1977) PB 83-182485]**PEER REVIEWED**

... Mortality among arsenic exposed smelter workers was greater when exposures had been to high arsenic combined with moderate or high sulfur dioxide exposures.
[American Conference of Governmental Industrial Hygienists. Documentation of the Threshold Limit Values and Biological Exposure Indices. 5th ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, 1986.542]**PEER REVIEWED**

The effects of sulfur dioxide and ozone alone and in combinations /were studied/, on young normal subjects under conditions of light exercise. ... When the two gases were present together in eight normal young subjects who were non-smokers, the maximal mid-expiratory flow rate dropped to 67% of its initial value at the end of 2 hours; the forced expiratory volume was 78% of its initial value, and the mid-expiratory flow rate (50% vital capacity) was only 54% of the initial value. ... /It was/ concluded that sulfur dioxide and ozone are exceedingly corrosive when present together, that "standard" must specify the presence or absence of the other, and that there is a growing incidence of the joint presence of the two pollutants in urban environments.
[Bates DV, Hazucha M; Paris Vol IV: 1977 (1974) as cited in Nat'l Research Council Canada; Sulphur and its Inorganic Derivatives in the Canadian Environment p.294 (1974) NRCC No. 15015]**PEER REVIEWED**

Pharmacology:

Therapeutic Uses:

MEDICATION (VET): AS FUMIGANT AGAINST LICE & MITES IN BUILDINGS (MINIMUM EFFECTIVE AEROSOL CONCN FOR LICE IS 1%; FOR MANGE CAUSING MITES IS 4% ACCOMPLISHED BY COMPLETELY BURNING 2-8 LB SULFUR RESPECTIVELY/1000 CU FT OF SPACE).
[Rossoff, I.S. Handbook of Veterinary Drugs. New York: Springer Publishing Company, 1974. 581]**PEER REVIEWED**

Interactions:

AEROSOLS THAT HAVE PRODUCED ... POTENTIATION OF RESPONSE TO SULFUR DIOXIDE ARE SOLUBLE SALTS OF SUCH METALS AS MANGANESE, FERROUS IRON, & VANADIUM. ... THESE AEROSOLS POTENTIATE RESPONSE ABOUT THREE FOLD WHEN PRESENT AT CONCN OF 1 MG/CU M @ 50% RELATIVE HUMIDITY.
[Doull, J., C.D.Klassen, and M.D. Amdur (eds.). Casarett and Doull's Toxicology. 3rd ed., New York: Macmillan Co., Inc., 1986. 811]**PEER REVIEWED**

Sulfur dioxide increases the carcinogenicity of benzopyrene by promoting its metabolism.
[Warshawsky D, et al; EPA Catalysts' Research Program's Sulfuric Acid Research Review Conference; Influence of Particulate and SO2 on Benzo(a)pyrene Metabolism (1977) as cited in OSHA; Public Hearing on Occupational Standard for Sulfur Dioxide: Statement of Edward Baier (NIOSH) (May 1977) PB 83-182485]**PEER REVIEWED**

... Mortality among arsenic exposed smelter workers was greater when exposures had been to high arsenic combined with moderate or high sulfur dioxide exposures.
[American Conference of Governmental Industrial Hygienists. Documentation of the Threshold Limit Values and Biological Exposure Indices. 5th ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, 1986.542]**PEER REVIEWED**

The effects of sulfur dioxide and ozone alone and in combinations /were studied/, on young normal subjects under conditions of light exercise. ... When the two gases were present together in eight normal young subjects who were non-smokers, the maximal mid-expiratory flow rate dropped to 67% of its initial value at the end of 2 hours; the forced expiratory volume was 78% of its initial value, and the mid-expiratory flow rate (50% vital capacity) was only 54% of the initial value. ... /It was/ concluded that sulfur dioxide and ozone are exceedingly corrosive when present together, that "standard" must specify the presence or absence of the other, and that there is a growing incidence of the joint presence of the two pollutants in urban environments.
[Bates DV, Hazucha M; Paris Vol IV: 1977 (1974) as cited in Nat'l Research Council Canada; Sulphur and its Inorganic Derivatives in the Canadian Environment p.294 (1974) NRCC No. 15015]**PEER REVIEWED**

Environmental Fate & Exposure:

Probable Routes of Human Exposure:

Inhalation ... /or/ direct contact of gas or liquid phase on ... mucous membranes.
[Sittig, M. Handbook of Toxic and Hazardous Chemicals and Carcinogens, 1985. 2nd ed. Park Ridge, NJ: Noyes Data Corporation, 1985. 813]**PEER REVIEWED**

It has been estimated by the Department of Labor that approx 600,000 American workers may be occupationally exposed to sulphur dioxide. Some of the highest exposures occur when it is a by product, as in the metal smelting industry, and in the processing or combustion of high sulfur coal or oil. Other exposures occur in manufacture of sulfuric acid, fumigating, food preservation, wine making, and bleaching of many substances.
[OSHA; Public Hearing on Occupational Standard for Sulfur Dioxide: Statement of Edward Baier (NIOSH) (May 1977) PB 83-182485]**PEER REVIEWED**

Natural Pollution Sources:

Hydrogen sulfide, from the natural decay of vegetation on land, marsh lands and in the oceans, is probably oxidized to sulfur dioxide within hours.
[Monitoring and Assessment Research Centre; Report #7 p.4 (1978)]**PEER REVIEWED**

Volcanoes are a sporadic, yet possibly significant, natural emissions source of sulfur dioxide.
[Monitoring and Assessment Research Centre; Sulfur Dioxide Report #7 p.6 (1978)]**PEER REVIEWED**

Artificial Pollution Sources:

... POTENTIAL HAZARD HAS ARISEN FROM INTRODUCTION OF SODIUM BISULFITE AS PRESERVATIVE FOR SILAGE; SULFUR DIOXIDE IS EVOLVED FROM BISULFITE DURING FERMENTATION PROCESS.
[Clarke, M. L., D. G. Harvey and D. J. Humphreys. Veterinary Toxicology. 2nd ed. London: Bailliere Tindall, 1981. 84]**PEER REVIEWED**

On a global basis, fossil fuel combustion accounts for 75 to 85% of man-made sulfur dioxide emissions, and industrial processes such as refining and smelting account for the remainder.
[Friend JP; Chemistry of the Lower Atmosphere pp.177-201 (1973) as cited in Monitoring and Assessment Research Centre; Report #7 p.5 (1978)]**PEER REVIEWED**

It is estimated that 93.5% of sulfur dioxide pollution is produced in the Northern Hemisphere, and the remaining 6.5% in the Southern Hemisphere.
[Kellogg WW et al; Science 175: 587 (1972) as cited in Monitoring and Assessment Research Centre; Report #7 p.7 (1978)]**PEER REVIEWED**

North-western Europe, an area about 1% of the Earth's surface, accounts for an estimated 13x10+12 or approximately 20% of the global total.
[Granat L; Ecol Bull 22: p.89-134 (1976) as cited in Monitoring and Assessment Research Centre; Report #7 p.7 (1978)]**PEER REVIEWED**

... In several industrial countries, emission of sulfur dioxide from coal burning power plants by tall stacks ... /has produced/ widespread dispersion of low levels of sulfur dioxide, sulfuric acid, sulfate, and nitric oxide that combine to measurable incr of local sulfur air concn and precipitation ... .
[Seiler, H.G., H. Sigel and A. Sigel (eds.). Handbook on the Toxicity of Inorganic Compounds. New York, NY: Marcel Dekker, Inc. 1988. 654]**PEER REVIEWED**

The global sulfur cycle involves an atmospheric flux of about (140-350)X10+6 tons/annum, with (40-60)X10+6 tons as anthropogenic sulfur, in the form of sulfur dioxide, sulfuric acid, and sulfate.
[Seiler, H.G., H. Sigel and A. Sigel (eds.). Handbook on the Toxicity of Inorganic Compounds. New York, NY: Marcel Dekker, Inc. 1988. 640]**PEER REVIEWED**

Most emissions of sulfur into the air are in the form of sulfur dioxide resulting from the combustion of fossil fuel for heating and energy production. Various industrial activities such as petroleum processing, smelter operations, wood, pulping, etc also produce significant emissions of sulfur dioxide and other sulfur compounds.
[WHO; Environ Health Criteria: Sulfur Oxides and Suspended Particulate Matter p.30 (1979)]**PEER REVIEWED**

Emissions of sulfur dioxide from base metal smelting operations, such as nickel, copper, lead, and zinc, or sintering of iron sulfides, constitute strong local sources.
[Nat'l Research Council Canada; Sulphur and its Inorganic Derivatives in the Canadian Environment p.26 (1977) NRCC No.15015]**PEER REVIEWED**

Environmental Fate:

Atmospheric Fate: Direct surface uptake of sulfur dioxide is the most important dry removal process for atmospheric sulfur; ... good sinks /include/ oceans (pH= 8), other non acidic moist surfaces, and some crops and forest species at certain growth stages; where as dry, snow covered surfaces and soils, for example, are less efficient.
[Monitoring and Assessment Research Centre; Report #7 p.13 (1978)]**PEER REVIEWED**

Atmospheric Fate: Deposition by precipitation (wet deposition) is the result of both in cloud and below cloud capture of sulfur dioxide and particulate sulfate. In cloud processes include sulfate particles serving as condensation nuclei, coagulation, and diffusional uptake of sulfur dioxide. Below cloud processes include interception of particles by falling drops and diffusional uptake of sulfur dioxide. In cloud scavenging processes are more important in clean air, ie where sulfur dioxide levels below the clouds are low.
[Monitoring and Assessment Research Centre; Report #7 p.13 (1978)]**PEER REVIEWED**

Atmospheric Fate: Wet deposition is, in general, much more easily measured than is dry deposition. ... Routine measurement of wet deposition ... is determined from ... sulfate concn in precipitation samples and precipitation amount. Typically, the removal rate for particulate sulfate is of the order of 40% per hr, and for sulfur dioxide, an order of magnitude less. The overall efficiency of wet removal depends on many factors: precipitation type, intensity, duration, frequency, the relative amounts of sulfur dioxide and sulfate present, and the size distribution of particulate sulfate.
[Monitoring and Assessment Research Centre; Report #7 p.14 (1978)]**PEER REVIEWED**

Atmospheric Fate: Wet and dry deposition appear to be of comparable importance, on an annual basis, over those large areas where measurments and calculations have been made. Dry deposition is more important closer to source regions where concn are higher, and, in principle, it goes on all the time. /Conversely/, wet deposition occurs only periodically.
[Monitoring and Assessment Research Centre; Report #7 p.14 (1978)]**PEER REVIEWED**

Terrestial Fate: Although snow covered surfaces are inefficient receptors of gaseous and particulate sulfur cmpd, the spring melt of the accumulated winter snowpack can result in rapid, short term inputs of high sulfate, low pH water to freshwater systems with resulting disastrous effects on fish.
[Monitoring and Assessment Research Centre; Report #7 p.21 (1978)]**PEER REVIEWED**

Atmospheric Fate: A photochemically generated aerosol, with sulfates as a major component, accumulates within summertime high pressure systems which affect the northeastern United States. As the high pressure system moves eastward with the accumulating aerosol, total suspended particles and sulfate concn in the New York metropolitan area significantly increase.
[Shils ME, Skolnik JN; Symposium on Environmental Effects of Sulfur Oxides and Related Particulates p.1032 (1978)]**PEER REVIEWED**

Atmospheric Fate: The avg residence time of pollution sulfur is usually between one and five days, depending on the climate of a region. /Sulfur cmpd/
[Monitoring and Assessment Research Centre; Report #7 p.5 (1978)]**PEER REVIEWED**

Environmental Abiotic Degradation:

Suggested values of reaction rates for gas phase oxidation of sulfur dioxide to sulfate for the western European summer range from 0.5 to 5%/hr in sunlight, depending on the degree of pollution of the atmosphere, with the lower figure relating to clean air. This oxidation involves other short lived pollutants which have been photochemically generated, therefore, the direct photo-oxidation of sulfur dioxide is not important. Because these reactions are dependent on solar radiation, their importance decreases significantly in winter time and at night.
[Eggleton A EJ, Cox RA; Atomospheric Environment (1978) as cited in Monitoring and Assessment Research Centre; Report #7 p.11 (1978)]**PEER REVIEWED**

Catalyzed, liquid phase, oxidation in the presence of metals (eg iron, manganese) is important in urban plumes and perhaps urban fogs where their concentrations are sufficiently high, but probably not in cleaner, rural air.
[Monitoring and Assessment Research Centre; Report #7 p.11 (1978)]**PEER REVIEWED**

Liquid phase oxidation involving the strong oxidizing agents ozone and hydrogen peroxide may also be very important (eg hydrogen sulfide and other organic sulfides oxidized to sulfur dioxide); however, reaction rates and atmospheric concentrations, respectively, for these two substances are not sufficiently well known.
[Monitoring and Assessment Research Centre; Report #7 p.11 (1978)]**PEER REVIEWED**

The relative importance of chemical versus dispersion processes in the oxidation of sulfur dioxide in atmospheric plumes is governed by atmospheric conditions (eg after long plume travel times, chemical reactions, rather than the rate of mixing of ambient air, are likely to become the dominant rate limiting factor; and vice versa).
[Monitoring and Assessment Research Centre; Report #7 p.12 (1978)]**PEER REVIEWED**

Sulfur dioxide reduces visibility by taking part in reactions between organic cmpd and nitrogen oxides to form particulates. Oxidation to sulfur trioxide, which then combines with water to form small droplets of sulfuric acid, also reduces visibility.
[Dreisbach, R.H. Handbook of Poisoning. 12th ed. Norwalk, CT: Appleton and Lange, 1987. 210]**PEER REVIEWED**

IN MOIST AIR OR FOGS, IT COMBINES WITH WATER TO FORM SULFUROUS ACID, BUT IT IS ONLY VERY SLOWLY OXIDIZED TO SULFURIC ACID.
[Sax, N.I. Dangerous Properties of Industrial Materials. 6th ed. New York, NY: Van Nostrand Reinhold, 1984. 2487]**PEER REVIEWED**

The oxidation of sulfur dioxide to sulfuric acid and sulfates in the atmosphere is important with regard to air pollution studies. Radicals, eg hydrogen monoxide, water, and carboxcylic acid, appear to be the principal species responsible for the homogeneous oxidation of sulfur dioxide in the atmosphere, which occurs at rates as high as 4.0%/hr.
[Kirk-Othmer Encyclopedia of Chemical Technology. 3rd ed., Volumes 1-26. New York, NY: John Wiley and Sons, 1978-1984.,p. 22(83) 135]**PEER REVIEWED**

Soil Adsorption/Mobility:

Sulfur dioxide uptake is dependent upon soil pH and moisture content.
[Payrissat M, Beilke S; Atmos Environ 9: 211 (1975) as cited in Monitoring and Assessment Research Centre; Report #7 p.21 (1978)]**PEER REVIEWED**

Effluent Concentrations:

Sulfur dioxide was emitted from man made sources in the United States at an estimated rate of 30 teragram/yr in 1973. The fuel combustion exclusive of transportation accounted for 78%, industrial processes (primary metal industry, petroleum industry, chemical manufacturing, etc) for 20%, and tansportation for 2%. Of the fuels used by utilities and industry, about 65% of the national anthropogenic emission of sulfur dioxide came from coal combustion and 13% from oil combustion.
[National Academy of Sciences; Sulfur oxides p.18 (1978)]**PEER REVIEWED**

Annually, the equivalent of about 1X10+8 tons sulfur is emitted into the atmosphere as an atmospheric pollutant from smelters, ore roasting, and coal-fired electric power plant emission. /Sulfur/
[Seiler, H.G., H. Sigel and A. Sigel (eds.). Handbook on the Toxicity of Inorganic Compounds. New York, NY: Marcel Dekker, Inc. 1988. 647]**PEER REVIEWED**

Atmospheric Concentrations:

Representative concn of sulfur dioxide and sulfate in air and precipitation are as follows: 1) rural North America 3 to 5 ug sulfur per cu m for sulfur dioxide, 1 to 3 ug sulfur per cu m for particulate sulfate, and 1 to 2 mg sulfur per l for excess precipitation-sulfate; 2) clean global background (land) up to 1.7 ug sulfur per cu m for sulfur dioxide, 0.1 to 0.5 ug sulfur per cu m for particulate sulfate, and 0.1 mg sulfur per l for excess precipitation sulfate.
[Monitoring and Assessment Research Centre; Report #7 p.23 (1978)]**PEER REVIEWED**

The national max annual avg for sulfur dioxide in community air is 0.03 ppm, and the max 24 hr avg is 0.14 ppm.
[Dreisbach, R.H. Handbook of Poisoning. 12th ed. Norwalk, CT: Appleton and Lange, 1987. 210]**PEER REVIEWED**

Sulfur dioxide exists in remote areas of the earth at 50-120 parts per trillion, and in urban atmosphere at levels between 1 ppb and 1 ppm.
[Seiler, H.G., H. Sigel and A. Sigel (eds.). Handbook on the Toxicity of Inorganic Compounds. New York, NY: Marcel Dekker, Inc. 1988. 654]**PEER REVIEWED**

Atmospheric sulfur dioxide concentrations display an enormous range, depending upon the intensity of industrial and urban activities. Values vary from about 1-5 ug/cu m for very remote clean areas, through 28.6-286 ug/cu m for very remote clean areas, to at least 6000 ug/cu m in industrial areas.
[Nat'l Research Council Canada; Sulphur and its Inorganic Derivatives in the Canadian Environment p.76 (1977) NRCC No.15015]**PEER REVIEWED**

Food Survey Values:

Sulfur dioxide occurs in onion, garlic, & wine.
[Fenaroli's Handbook of Flavor Ingredients. Volume 1. Edited, translated, and revised by T.E. Furia and N. Bellanca. 2nd ed. Cleveland: The Chemical Rubber Co., 1975. 188]**PEER REVIEWED**

Other Environmental Concentrations:

It was found that sulfur dioxide was taken up from atmosphere by sulfate treated plants ... .
[Fenaroli's Handbook of Flavor Ingredients. Volume 1. Edited, translated, and revised by T.E. Furia and N. Bellanca. 2nd ed. Cleveland: The Chemical Rubber Co., 1975. 165]**PEER REVIEWED**

Environmental Standards & Regulations:

FIFRA Requirements:

Residues from the use of sulfur dioxide in liquid grain-fumigant formulations for marker or fire-retardant purposes at levels not exceeding 5% by wt of such formulations are exempted from the requirement of a tolerance in or on barley, buckwheat, corn, oats, popcorn, rice, rye, grain sorghum (milo), wheat.
[40 CFR 180.1013 (7/1/96)]**PEER REVIEWED**

Residues of sulfur dioxide resulting from post harvest fungical use are exempted from the requirement of tolerances in or on corn for feed use only.
[40 CFR 180.1013 (7/1/96)]**PEER REVIEWED**

As the federal pesticide law FIFRA directs, EPA is conducting a comprehensive review of older pesticides to consider their health and environmental effects and make decisions about their future use. Under this pesticide reregistration program, EPA examines health and safety data for pesticide active ingredients initially registered before November 1, 1984, and determines whether they are eligible for reregistration. In addition, all pesticides must meet the new safety standard of the Food Quality Protection Act of 1996. Pesticides for which EPA had not issued Registration Standards prior to the effective date of FIFRA, as amended in 1988, were divided into three lists based upon their potential for human exposure and other factors, with List B containing pesticides of greater concern and List D pesticides of less concern. Sulfur dioxide is found on List D. Case No: 4056; Pesticide type: fungicide; Case Status: OPP is reviewing data from the pesticide's producers regarding its human health and/or environmental effects, or OPP is determining the pesticide's eligibility for reregistration and developing the Reregistration Eligibility Decision (RED) document.; Active ingredient (AI): Sulfur dioxide; Data Call-in (DCI) Date(s): 09/30/93, 10/13/95; AI Status: The producers of the pesticide has made commitments to conduct the studies and pay the fees required for reregistration, and are meeting those commitments in a timely manner.
[USEPA/OPP; Status of Pesticides in Registration, Reregistration and Special Review p.320 (Spring, 1998) EPA 738-R-98-002]**QC REVIEWED**

FDA Requirements:

Sulfur dioxide is generally recognized as safe when used in accordance with good manufacturing or feeding practice, except that it is not used in meats or in food recognized as source of vitamin B1.
[21 CFR 582.3862 (4/1/96)]**PEER REVIEWED**

Allowable Tolerances:

Residues from the use of sulfur dioxide in liquid grain-fumigant formulations for marker or fire-retardant purposes at levels not exceeding 5% by wt of such formulations are exempted from the requirement of a tolerance in or on barley, buckwheat, corn, oats, popcorn, rice, rye, grain sorghum (milo), wheat.
[40 CFR 180.1013 (7/1/96)]**PEER REVIEWED**

Residues of sulfur dioxide resulting from post harvest fungical use are exempted from the requirement of tolerances in or on corn for feed use only.
[40 CFR 180.1013 (7/1/96)]**PEER REVIEWED**

Chemical/Physical Properties:

Molecular Formula:

SO2
[Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996. 1534]**PEER REVIEWED**

Molecular Weight:

64.065
[Lide, D.R. (ed.). CRC Handbook of Chemistry and Physics. 76th ed. Boca Raton, FL: CRC Press Inc., 1995-1996.,p. 4-88]**PEER REVIEWED**

Color/Form:

COLORLESS NON-FLAMMABLE GAS
[Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996. 1535]**PEER REVIEWED**

Colorless gas ... [Note: A liquid below 14 degrees F. Shipped as a liquefied compressed gas].
[NIOSH. NIOSH Pocket Guide to Chemical Hazards. DHHS (NIOSH) Publication No. 97-140. Washington, D.C. U.S. Government Printing Office, 1997. 288]**QC REVIEWED**

Odor:

STRONG SUFFOCATING ODOR
[Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996. 1535]**PEER REVIEWED**

Irritating odor
[Ruth JH; Am Ind Hyg Assoc J 47: A-142-51 (1986)]**PEER REVIEWED**

... Characteristic, irritating, pungent odor ...
[NIOSH. NIOSH Pocket Guide to Chemical Hazards. DHHS (NIOSH) Publication No. 97-140. Washington, D.C. U.S. Government Printing Office, 1997. 288]**QC REVIEWED**

Taste:

Acid taste
[International Labour Office. Encyclopedia of Occupational Health and Safety. Vols. I&II. Geneva, Switzerland: International Labour Office, 1983. 2122]**PEER REVIEWED**

Boiling Point:

-10.05 DEG C
[Lide, D.R. (ed.). CRC Handbook of Chemistry and Physics. 76th ed. Boca Raton, FL: CRC Press Inc., 1995-1996.,p. 4-88]**PEER REVIEWED**

Melting Point:

-75.5 DEG C
[Lide, D.R. (ed.). CRC Handbook of Chemistry and Physics. 76th ed. Boca Raton, FL: CRC Press Inc., 1995-1996.,p. 4-88]**PEER REVIEWED**

Corrosivity:

Corrodes aluminum
[U.S. Coast Guard, Department of Transportation. CHRIS - Hazardous Chemical Data. Volume II. Washington, D.C.: U.S. Government Printing Office, 1984-5.]**PEER REVIEWED**

Iron, steel, nickel, copper-nickel alloys, & inconel nickel-chromium-iron are satisfactory for dry or hot sulfur dioxide, but they are readily corroded below the dew point or by wet sulfur dioxide gas. Liquid sulfur dioxide produces serious corrosion of iron, brass, copper at about 0.2 wt% or higher moisture content.
[Kirk-Othmer Encyclopedia of Chemical Technology. 4th ed. Volumes 1: New York, NY. John Wiley and Sons, 1991-Present.,p. V23 305-306]**PEER REVIEWED**

Liquid sulfur dioxide will attack some forms of plastic, rubber, & coatings
[Mackison, F. W., R. S. Stricoff, and L. J. Partridge, Jr. (eds.). NIOSH/OSHA - Occupational Health Guidelines for Chemical Hazards. DHHS(NIOSH) Publication No. 81-123 (3 VOLS). Washington, DC: U.S. Government Printing Office, Jan. 1981.2]**PEER REVIEWED**

Critical Temperature & Pressure:

Critical temp: 315 deg F= 157 deg C= 430 K; Critical pressure: 1142 psia= 77.69 atm= 7.870 mn/sq m
[U.S. Coast Guard, Department of Transportation. CHRIS - Hazardous Chemical Data. Volume II. Washington, D.C.: U.S. Government Printing Office, 1984-5.]**PEER REVIEWED**

Density/Specific Gravity:

2.811 g/l
[Lide, D.R. (ed.). CRC Handbook of Chemistry and Physics. 76th ed. Boca Raton, FL: CRC Press Inc., 1995-1996.,p. 4-88]**PEER REVIEWED**

Heat of Vaporization:

171 BTU/LB= 94.8 CAL/G= 3.97X10+5 J/KG
[U.S. Coast Guard, Department of Transportation. CHRIS - Hazardous Chemical Data. Volume II. Washington, D.C.: U.S. Government Printing Office, 1984-5.]**PEER REVIEWED**

Solubilities:

17.7% in water @ 0 deg C
[Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996. 1535]**PEER REVIEWED**

11.9% in water @ 15 deg C
[Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996. 1535]**PEER REVIEWED**

8.5% in water @ 25 deg C
[Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996. 1535]**PEER REVIEWED**

6.4% in water @ 35 deg C
[Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996. 1535]**PEER REVIEWED**

25% in alc
[Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996. 1535]**PEER REVIEWED**

32% in methanol
[Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996. 1535]**PEER REVIEWED**

SOL IN CHLOROFORM
[Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996. 1535]**PEER REVIEWED**

SOL IN ETHER
[Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996. 1535]**PEER REVIEWED**

SOL IN ACETIC ACID, SULFURIC ACID
[Lide, D.R. (ed.). CRC Handbook of Chemistry and Physics. 76th ed. Boca Raton, FL: CRC Press Inc., 1995-1996.,p. 4-88]**PEER REVIEWED**

Water solubliity in mol fractions: .0345 at 288.15 K; .029 at 293.15 K; .0246 at 298.15 K; .021 at 303.15 K; .018 at 308.15 K
[Lide, D.R. (ed.). CRC Handbook of Chemistry and Physics. 76th ed. Boca Raton, FL: CRC Press Inc., 1995-1996.,p. 6-5]**PEER REVIEWED**

0.58 g/100 CC water @ 90 deg C
[Weast, R.C. (ed.) Handbook of Chemistry and Physics. 69th ed. Boca Raton, FL: CRC Press Inc., 1988-1989.,p. B-135]**PEER REVIEWED**

11.3 g/100 CC water @ 20 deg C
[Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.4 (1985)]**PEER REVIEWED**

Moderately soluble in benzene, acetone and carbon tetrachloride
[Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.4 (1985)]**PEER REVIEWED**

water solubility = 1.07X10+5 mg/l @ 21 deg C
[Venable CS, Fuwa T; Ind Eng Chem 14:139-42 (1922)]**PEER REVIEWED**

Spectral Properties:

INDEX OF REFRACTION (LIQ): 1.410 @ 24 DEG C
[Lewis, R.J., Sr (Ed.). Hawley's Condensed Chemical Dictionary. 12th ed. New York, NY: Van Nostrand Rheinhold Co., 1993 1104]**PEER REVIEWED**

Surface Tension:

28.59 mN/m (liquid @ 10 deg C)
[Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.4 (1985)]**PEER REVIEWED**

Vapor Density:

2.263 at 0 deg C (air = 1)
[Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.3 (1985)]**PEER REVIEWED**

Vapor Pressure:

vapor pressure = 3X10+3 mm Hg @ 25 deg C/ from experimentally derived coefficients
[Daubert, T.E., R.P. Danner. Physical and Thermodynamic Properties of Pure Chemicals Data Compilation. Washington, D.C.: Taylor and Francis, 1989.]**PEER REVIEWED**

Relative Evaporation Rate:

Greater than 1 (Butyl acetate = 1)
[Mackison, F. W., R. S. Stricoff, and L. J. Partridge, Jr. (eds.). NIOSH/OSHA - Occupational Health Guidelines for Chemical Hazards. DHHS(NIOSH) Publication No. 81-123 (3 VOLS). Washington, DC: U.S. Government Printing Office, Jan. 1981.2]**PEER REVIEWED**

Viscosity:

Gas: 0.0124 mPa.s @ 18 deg C. Liquid: 0.368 mPa.s @ 0 deg C.
[Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.3 (1985)]**PEER REVIEWED**

Other Chemical/Physical Properties:

MIXED WITH OXYGEN & PASSED OVER RED-HOT PLATINUM, IT IS CONVERTED INTO SULFUR TRIOXIDE
[Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996. 1535]**PEER REVIEWED**

WITH WATER FORMS SULFUROUS ACID (H2SO3); BLEACHES VEGETABLE COLORS
[Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996. 1535]**PEER REVIEWED**

1 PPM IS EQUIV TO 2.62 MG/CU M & 1 MG/CU M IS EQUIV TO 0.38 PPM @ 25 DEG C, 760 MM HG
[Patty, F. (ed.). Industrial Hygiene and Toxicology: Volume II: Toxicology. 2nd ed. New York: Interscience Publishers, 1963. 893]**PEER REVIEWED**

RATIO OF SPECIFIC HEATS OF VAPOR (GAS): 1.265
[U.S. Coast Guard, Department of Transportation. CHRIS - Hazardous Chemical Data. Volume II. Washington, D.C.: U.S. Government Printing Office, 1984-5.]**PEER REVIEWED**

HEAT OF SOLN: -94.1 BTU/LB= -52.3 CAL/G= -2.19X10+5 J/KG
[U.S. Coast Guard, Department of Transportation. CHRIS - Hazardous Chemical Data. Volume II. Washington, D.C.: U.S. Government Printing Office, 1984-5.]**PEER REVIEWED**

SULFUR DIOXIDE IS VOLATILE & TENDS TO DISAPPEAR FROM OPEN SYSTEMS & MUCH MAY BE INACTIVATED BY COMBINATION WITH FOOD COMPONENTS. DESTROYING THIAMINE, IT IS SOMEWHAT CORROSIVE
[Furia, T.E. (ed.). CRC Handbook of Food Additives. 2nd ed. Cleveland: The Chemical Rubber Co., 1972. 144]**PEER REVIEWED**

Condensation point: -10 deg C
[Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996. 1535]**PEER REVIEWED**

Ionization potential 12.3 eV
[NIOSH. Pocket Guide to Chemical Hazards. 2nd Printing. DHHS (NIOSH) Publ. No. 85-114. Washington, D.C.: U.S. Dept. of Health and Human Services, NIOSH/Supt. of Documents, GPO, February 1987.212]**PEER REVIEWED**

Extremely stable to heat, even up to 2000 deg C
[Kirk-Othmer Encyclopedia of Chemical Technology. 3rd ed., Volumes 1-26. New York, NY: John Wiley and Sons, 1978-1984.,p. 22(83) 135]**PEER REVIEWED**

An oxidizing and reducing agent
[Lewis, R.J., Sr (Ed.). Hawley's Condensed Chemical Dictionary. 12th ed. New York, NY: Van Nostrand Rheinhold Co., 1993 1104]**PEER REVIEWED**

Ideal gas heat capacity= 0.149 BTU/lb-deg F @ 75 deg F
[U.S. Coast Guard, Department of Transportation. CHRIS - Hazardous Chemical Data. Volume II. Washington, D.C.: U.S. Government Printing Office, 1984-5.]**PEER REVIEWED**

Saturated vapor density= 0.47050 lb/cu ft @ 60 deg F
[U.S. Coast Guard, Department of Transportation. CHRIS - Hazardous Chemical Data. Volume II. Washington, D.C.: U.S. Government Printing Office, 1984-5.]**PEER REVIEWED**

Latent heat of fusion: 7.4 KJ/mole @ -75.5 deg C
[Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.3 (1985)]**PEER REVIEWED**

Latent heat of sublimation: 30.6 KJ/mole (est)
[Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.3 (1985)]**PEER REVIEWED**

Latent heat of vaporization: -296.8 KJ/mole @ 25 deg C
[Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.3 (1985)]**PEER REVIEWED**

Entropy: 248.1 J/(mole deg C)(25 deg C)
[Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.3 (1985)]**PEER REVIEWED**

pH of aqueous solution: produces a slightly acidic aqueous solution when combined with the water in the atmosphere or on hand.
[Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.4 (1985)]**PEER REVIEWED**

VAPOR PRESSURE: 3.2 ATM @ 20 DEG C
[Lewis, R.J., Sr (Ed.). Hawley's Condensed Chemical Dictionary. 12th ed. New York, NY: Van Nostrand Rheinhold Co., 1993 1104]**PEER REVIEWED**

The oxidation of sulfur dioxide leads to sulfurous acid and sulfur trioxide, which is rapidly converted to sulfuric acid; a major constituent of acid rain.
[Harrison RM et al. Environ Tech Lett 9: 521-530 (1988)]**PEER REVIEWED**

Chemical Safety & Handling:

Hazards Summary:

The major hazards encountered in the use and handling of sulfur dioxide stem from its toxicologic properties. Exposure to this strong-smelling, colorless gas or liquid (compressed gas) may occur from its use as a fumigant, as an intermediate in the manufacture of sulfuric acid and other sulfur compounds, in oil, mineral, food and paper processing, and in water treatment. Effectsfrom exposure may include contact burns to the eyes, skin, and mucous membranes, frostbite, bronchoconstriction, and pulmonary edema. OSHA has established a time weighted average (TWA) limit of 2 ppm and a short term exposure limit (STEL) of 5 ppm, to become effective December 31, 1992. Engineering controls, including local exhaust ventilation, should be used to maintain sulfur dioxide at or below the permissible limit. In activities and situations where over-exposure may occur, wear chemical protective clothing and a self-contained breathing apparatus. If contact should occur, immediately remove contaminated clothing (to be left at worksite for cleaning), irrigate exposed eyes with copiousamounts of tepid water for at least 15 minutes, flush exposed skin with water, and treat for possible frostbite. Emergency eyewash facilities should be available in sulfur dioxide work areas. While sulfur dioxide does not ignite easily, it may burn, and cylinders of the compressed material can explode in the heat of a fire. For fires involving sulfur dioxide, extinguish with dry chemical, CO2, Halon, water spray, fog, or standard foam. If water is used, apply from as far a distance as possible because material will react with water to form toxic and corrosive fumes. Sulfur dioxide may be shipped domestically via air (cargo only), rail (cargo only), road, and water, in containers bearing the label, "Nonflammable gas." Sulfur dioxide should be stored in tightly closed containers, in cool, well-ventilated areas, and away from sources of physical damage. For spills of liquid sulfur dioxide, first evacuate area for 50 feet in all directions, use water spray to reduce vapor, and neutralize spilled material with limestone, soda ash, or lime. Keep material from entering water sources and sewers. Before implementing land disposal of sulfur dioxide waste, consult with environmental regulatory agencies for guidance.
**PEER REVIEWED**

DOT Emergency Guidelines:

Health: TOXIC; may be fatal if inhaled. Vapors are extremely irritating and corrosive. Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control may cause pollution. /Sulfur dioxide; Sulfur dioxide, liquefied/
[U.S. Department of Transportation. 2000 Emergency Response Guidebook. RSPA P 5800.8 Edition. Washington, D.C: U.S. Government Printing Office, 2000,p. G-125]**QC REVIEWED**

Fire or explosion: Some may burn, but none ignite readily. Vapors from liquefied gas are initially heavier than air and spread along ground. Some of these materials may react violently with water. Containers may explode when heated. Ruptured cylinders may rocket. /Sulfur dioxide; Sulfur dioxide, liquefied/
[U.S. Department of Transportation. 2000 Emergency Response Guidebook. RSPA P 5800.8 Edition. Washington, D.C: U.S. Government Printing Office, 2000,p. G-125]**QC REVIEWED**

Public safety: CALL Emergency Response Telephone Number. ... Isolate spill or leak area immediately for at least 100 to 200 meters (330 to 660 feet) in all directions. Keep unauthorized personnel away. Stay upwind. Many gases are heavier than air and will spread along ground and collect in low or confined areas (sewers, basements, tanks). Keep out of low areas. Ventilate closed spaces before entering. /Sulfur dioxide; Sulfur dioxide, liquefied/
[U.S. Department of Transportation. 2000 Emergency Response Guidebook. RSPA P 5800.8 Edition. Washington, D.C: U.S. Government Printing Office, 2000,p. G-125]**QC REVIEWED**

Protective clothing: Wear positive pressure self-contained breathing apparatus (SCBA). Wear chemical protective clothing which is specifically recommended by the manufacturer. It may provide little or no thermal protection. Structural firefighters' protective clothing provides limited protection in fire situations ONLY; it is not effective in spill situations. /Sulfur dioxide; Sulfur dioxide, liquefied/
[U.S. Department of Transportation. 2000 Emergency Response Guidebook. RSPA P 5800.8 Edition. Washington, D.C: U.S. Government Printing Office, 2000,p. G-125]**QC REVIEWED**

Evacuation: ... Fire: If tank, rail car or tank truck is involved in a fire, ISOLATE for 1600 meters (1 mile) in all directions; also, consider initial evacuation for 1600 meters (1 mile) in all directions. /Sulfur dioxide; Sulfur dioxide, liquefied/
[U.S. Department of Transportation. 2000 Emergency Response Guidebook. RSPA P 5800.8 Edition. Washington, D.C: U.S. Government Printing Office, 2000,p. G-125]**QC REVIEWED**

Fire: Small fires: Dry chemical or CO2. Large fires: Water spray, fog or regular foam. Move containers from fire area if you can do it without risk. Do not get water inside containers. Damaged cylinders should be handled only by specialists. Fire involving tanks: Fight fire from maximum distance or use unmanned hose holders or monitor nozzles. Cool containers with flooding quantities of water until well after fire is out. Do not direct water at source of leak or safety devices; icing may occur. Withdraw immediately in case of rising sound from venting safety devices or discoloration of tank. Always stay away from tanks engulfed in fire. /Sulfur dioxide; Sulfur dioxide, liquefied/
[U.S. Department of Transportation. 2000 Emergency Response Guidebook. RSPA P 5800.8 Edition. Washington, D.C: U.S. Government Printing Office, 2000,p. G-125]**QC REVIEWED**

Spill or leak: Fully encapsulating, vapor protective clothing should be worn for spills and leaks with no fire. Do not touch or walk through spilled material. Stop leak if you can do it without risk. If possible, turn leaking containers so that gas escapes rather than liquid. Prevent entry into waterways, sewers, basements or confined areas. Do not direct water at spill or source of leak. Use water spray to reduce vapors or divert vapor cloud drift. Avoid allowing water runoff to contact spilled material. Isolate area until gas has dispersed. /Sulfur dioxide; Sulfur dioxide, liquefied/
[U.S. Department of Transportation. 2000 Emergency Response Guidebook. RSPA P 5800.8 Edition. Washington, D.C: U.S. Government Printing Office, 2000,p. G-125]**QC REVIEWED**

First aid: Move victim to fresh air. Call 911 or emergency medical service. Apply artificial respiration if victim is not breathing. Do not use mouth-to-mouth method if victim ingested or inhaled the substance; induce artificial respiration with the aid of a pocket mask equipped with a one-way valve or other proper respiratory medical device. Administer oxygen if breathing is difficult. Remove and isolate contaminated clothing and shoes. In case of contact with liquefied gas, thaw frosted parts with lukewarm water. In case of contact with substance, immediately flush skin or eyes with running water for at least 20 minutes. Keep victim warm and quiet. Keep victim under observation. Effects of contact or inhalation may be delayed. Ensure that medical personnel are aware of the material(s) involved, and take precautions to protect themselves. /Sulfur dioxide; Sulfur dioxide, liquefied/
[U.S. Department of Transportation. 2000 Emergency Response Guidebook. RSPA P 5800.8 Edition. Washington, D.C: U.S. Government Printing Office, 2000,p. G-125]**QC REVIEWED**

Initial Isolation and Protective Action Distances: Small Spills (from a small package or small leak from a large package): First, ISOLATE in all Directions 30 meters (100 feet); then, PROTECT persons Downwind during DAY 0.3 kilometers (0.2 miles) and NIGHT 1.1 kilometers (0.7 miles). LARGE SPILLS (from a large package or from many small packages): First, ISOLATE in all Directions 185 meters (600 feet); then, PROTECT persons Downwind during DAY 3.1 kilometers (1.9 miles) and NIGHT 7.2 kilometers (4.5 miles). /Sulfur dioxide; Sulfur dioxide, liquefied/
[U.S. Department of Transportation. 2000 Emergency Response Guidebook. RSPA P 5800.8 Edition. Washington, D.C: U.S. Government Printing Office, 2000,p. TABLE]**QC REVIEWED**

Odor Threshold:

4.70X10-1 ppm (recognition in air, chemically pure)
[Fazzalari, F.A. (ed.). Compilation of Odor and Taste Threshold Values Data. ASTM Data Series DS 48A (Committee E-18). Philadelphia, PA: American Society for Testing and Materials, 1978. 153]**PEER REVIEWED**

Odor threshold: 0.1 ppm (low); 3.0 ppm (high)
[Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.1 (1985)]**PEER REVIEWED**

Odor threshold: 1.1750 mg/cu m (low); 12.5000 mg/cu m (high); Irritating odor concn: 5.0 mg/cu m.
[Ruth JH; Am Ind Hyg Assoc J 47: A-142-51 (1986)]**PEER REVIEWED**

Skin, Eye and Respiratory Irritations:

VAPORS CAUSE SEVERE IRRITATION OF EYES & THROAT ... .
[U.S. Coast Guard, Department of Transportation. CHRIS - Hazardous Chemical Data. Volume II. Washington, D.C.: U.S. Government Printing Office, 1984-5.]**PEER REVIEWED**

... Strong irritant to eyes & mucous membranes ... .
[Sax, N.I. and R.J. Lewis, Sr. (eds.). Hawley's Condensed Chemical Dictionary. 11th ed. New York: Van Nostrand Reinhold Co., 1987. 1107]**PEER REVIEWED**

Irritating to ... resp system & skin.
[Commission of the European Communities. Legislation on Dangerous Substances - Classification and Labelling in the European Communities. Vol. II. London and Trotman Ltd., 1989. 138]**PEER REVIEWED**

HAZARD WARNING: Because of the high solubility of sulfur dioxide, it is extremely irritating to the eyes and upper respiratory tract.
[Sullivan, J.B. Jr., G.R. Krieger (eds.). Hazardous Materials Toxicology-Clinical Principles of Environmental Health. Baltimore, MD: Williams and Wilkins, 1992. 969]**PEER REVIEWED**

Fire Potential:

NOT COMBUSTIBLE.
[Fire Protection Guide to Hazardous Materials. 12 ed. Quincy, MA: National Fire Protection Association, 1997. ,p. 49-123]**QC REVIEWED**

... Not flammable with air.
[Seiler, H.G., H. Sigel and A. Sigel (eds.). Handbook on the Toxicity of Inorganic Compounds. New York, NY: Marcel Dekker, Inc. 1988. 643]**PEER REVIEWED**

NFPA Hazard Classification:

Health: 3. 3= Materials that, on short exposure, could cause serious temporary or residual injury, including those requiring protection from all bodily contact. Fire fighters may enter the area only if they are protected from all contact with the material. Full protective clothing, incl self-contained breathing apparatus, coat, pants, gloves, boots and bands around legs, arms and waist should be provided. No skin surface should be exposed.
[Fire Protection Guide to Hazardous Materials. 12 ed. Quincy, MA: National Fire Protection Association, 1997. ,p. 49-123]**QC REVIEWED**

Flammability: 0. 0= Any material that will not burn.
[Fire Protection Guide to Hazardous Materials. 12 ed. Quincy, MA: National Fire Protection Association, 1997. ,p. 49-123]**QC REVIEWED**

Reactivity: 0. 0= Includes materials that are normally stable, even under fire exposure conditions, and that do not react with water. Normal fire fighting procedures may be used.
[Fire Protection Guide to Hazardous Materials. 12 ed. Quincy, MA: National Fire Protection Association, 1997. ,p. 49-123]**QC REVIEWED**

Fire Fighting Procedures:

If material involved in fire: Extinguish fire using agent suitable for type of surrounding fire. (Material itself does not burn or burns with difficulty.) Cool all affected containers with flooding quantities of water. Apply water from as far a distance as possible. Use water spray to knock-down vapors. /Sulfur dioxide, liquified/
[Association of American Railroads. Emergency Handling of Hazardous Materials in Surface Transportation. Washington, DC: Association of American Railroads, Bureau of Explosives, 1994. 1017]**PEER REVIEWED**

Use water spray to keep fire-exposed containers cool. Extinguish fire using agent suitable for surrounding fire.
[Fire Protection Guide to Hazardous Materials. 12 ed. Quincy, MA: National Fire Protection Association, 1997. ,p. 49-123]**QC REVIEWED**

Firefighting Hazards:

BEHAVIOR IN FIRE: CONTAINERS MAY RUPTURE & RELEASE IRRITATING, TOXIC SULFUR DIOXIDE.
[U.S. Coast Guard, Department of Transportation. CHRIS - Hazardous Chemical Data. Volume II. Washington, D.C.: U.S. Government Printing Office, 1984-5.]**PEER REVIEWED**

Explosive Limits & Potential:

AN EXPLOSIVE WHEN COMPRESSED.
[International Labour Office. Encyclopedia of Occupational Health and Safety. Volumes I and II. New York: McGraw-Hill Book Co., 1971. 597]**PEER REVIEWED**

Hazardous Reactivities & Incompatibilities:

DANGEROUS; WILL REACT WITH WATER OR STEAM TO PRODUCE TOXIC & CORROSIVE FUMES.
[Lewis, R.J. Sax's Dangerous Properties of Industrial Materials. 9th ed. Volumes 1-3. New York, NY: Van Nostrand Reinhold, 1996. 3359]**PEER REVIEWED**

MONOCESIUM OR MONOPOTASSIUM ACETYLIDES, & THE AMMONIATE OF MONOLITHIUM ACETYLIDE, ALL IGNITE & INCANDESCE IN UNHEATED SULFUR DIOXIDE. THE DIMETAL DERIVATIVES INCL SODIUM ACETYLIDE APPEAR TO BE LESS REACTIVE, NEEDING HEAT BEFORE IGNITION OCCURS.
[Bretherick, L. Handbook of Reactive Chemical Hazards. 4th ed. Boston, MA: Butterworth-Heinemann Ltd., 1990 1415]**PEER REVIEWED**

CESIUM MONOXIDE, IRON(II) OXIDE, TIN OXIDE & LEAD(IV) OXIDE ALL IGNITE & INCANDESCE ON HEATING IN /SULFUR DIOXIDE/ GAS. FINELY DIVIDED (PYROPHORIC) CHROMIUM INCANDESCES IN SULFUR DIOXIDE, WHILE PYROPHORIC MANGANESE BURNS ... ON HEATING IN GAS. MOLTEN SODIUM REACTS VIOLENTLY WITH DRY GAS OR LIQ, WHILE MOIST GAS REACTS AS VIGOROUSLY AS WATER WITH COLD SODIUM.
[Bretherick, L. Handbook of Reactive Chemical Hazards. 4th ed. Boston, MA: Butterworth-Heinemann Ltd., 1990 1415]**PEER REVIEWED**

HEATED OXIDE /BARIUM PEROXIDE/ ATTAINS INCANDESCENCE IN A RAPID STREAM OF ... SULFUR DIOXIDE.
[Bretherick, L. Handbook of Reactive Chemical Hazards. 4th ed. Boston, MA: Butterworth-Heinemann Ltd., 1990 84]**PEER REVIEWED**

ACROLEIN POLYMERIZES WITH RELEASE OF HEAT ON CONTACT WITH MINOR AMT OF ACIDS (INCL SULFUR DIOXIDE) ... .
[Fire Protection Guide to Hazardous Materials. 12 ed. Quincy, MA: National Fire Protection Association, 1997. ,p. 491-10]**QC REVIEWED**

POWDERED ALUMINUM BURNS IN THE VAPOR OF ... SULFUR DIOXIDE ... .
[Fire Protection Guide to Hazardous Materials. 12 ed. Quincy, MA: National Fire Protection Association, 1997. ,p. 491-13]**QC REVIEWED**

RUBIDIUM CARBIDE IGNITES ON WARMING IN SULFUR DIOXIDE ... VAPOR.
[Fire Protection Guide to Hazardous Materials. 12 ed. Quincy, MA: National Fire Protection Association, 1997. ,p. 491-167]**QC REVIEWED**

WHEN STANNOUS OXIDE IS HEATED IN ATMOSPHERE OF SULFUR DIOXIDE, REACTION IS ATTENDED BY INCANDESCENCE.
[Fire Protection Guide to Hazardous Materials. 12 ed. Quincy, MA: National Fire Protection Association, 1997. ,p. 491-186]**QC REVIEWED**

Sodium carbide reacts with incandescence when placed in carbon dioxide, chlorine, or sulfur dioxide.
[Fire Protection Guide to Hazardous Materials. 12 ed. Quincy, MA: National Fire Protection Association, 1997. ,p. 491-177]**QC REVIEWED**

WHEN FERROUS OXIDE, PREPARED AT 300 DEG C, IS HEATED IN SULFUR DIOXIDE, THE MASS BECOMES INCANDESCENT.
[Fire Protection Guide to Hazardous Materials. 12 ed. Quincy, MA: National Fire Protection Association, 1997. ,p. 491-84]**QC REVIEWED**

SULFUR DIOXIDE REACTS EXPLOSIVELY IN CONTACT WITH SODIUM HYDRIDE UNLESS DILUTED WITH HYDROGEN.
[Bretherick, L. Handbook of Reactive Chemical Hazards. 4th ed. Boston, MA: Butterworth-Heinemann Ltd., 1990 1182]**PEER REVIEWED**

CONTACT /WITH POTASSIUM CHLORATE/ @ TEMP ABOVE 60 DEG C CAUSES FLASHING OF THE EVOLVED CHLORINE DIOXIDE. SOLN OF SULFUR DIOXIDE IN ETHANOL OR ETHER CAUSE AN EXPLOSION ON CONTACT @ AMBIENT TEMP.
[Bretherick, L. Handbook of Reactive Chemical Hazards. 4th ed. Boston, MA: Butterworth-Heinemann Ltd., 1990 975]**PEER REVIEWED**

DURING PREPN OF ZINC ETHYLSULFINATE, ADDITION OF DIETHYLZINC TO LIQ SULFUR DIOXIDE @ -15 DEG C LEADS TO AN EXPLOSIVELY VIOLENT REACTION. CONDENSATION OF THE DIOXIDE INTO COLD DIETHYLZINC LEADS TO A CONTROLLABLE REACTION ON WARMING.
[Bretherick, L. Handbook of Reactive Chemical Hazards. 4th ed. Boston, MA: Butterworth-Heinemann Ltd., 1990 494]**PEER REVIEWED**

MIXT /OF PROPENE & SULFUR DIOXIDE/ UNDER CONFINEMENT IN A GLASS PRESSURE BOTTLE @ 20 DEG C POLYMERIZE EXPLOSIVELY, THE POLYMERIZATION PROBABLY BEING INITIATED BY ACCESS OF LIGHT THROUGH THE CLEAR GLASS CONTAINER. SUCH ALKENE-SULFUR DIOXIDE COPOLYMERIZATIONS WILL NOT OCCUR ABOVE A CEILING TEMP, DIFFERENT FOR EACH ALKENE.
[Bretherick, L. Handbook of Reactive Chemical Hazards. 4th ed. Boston, MA: Butterworth-Heinemann Ltd., 1990 372]**PEER REVIEWED**

EACH BUBBLE OF SULFUR DIOXIDE GAS LED INTO A CONTAINER OF FLUORINE PRODUCES AN EXPLOSION.
[Fire Protection Guide to Hazardous Materials. 12 ed. Quincy, MA: National Fire Protection Association, 1997. ,p. 491-88]**QC REVIEWED**

CHLORINE TRIFLUORIDE CAUSES AN EXPLOSIVE REACTION WITH ... SULFUR DIOXIDE ... .
[Fire Protection Guide to Hazardous Materials. 12 ed. Quincy, MA: National Fire Protection Association, 1997. ,p. 491-55]**QC REVIEWED**

DRY SULFUR DIOXIDE REACTS ON CHLORATES WITH EVOLUTION OF CHLORINE PEROXIDE WHICH WILL FLASH @ 60 DEG C & CAN EXPLODE.
[Fire Protection Guide to Hazardous Materials. 12 ed. Quincy, MA: National Fire Protection Association, 1997. ,p. 491-50]**QC REVIEWED**

Reacts with cesium acetylene carbide, becoming incandescent. /From table/
[Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.84 (1985)]**PEER REVIEWED**

Reacts with chromium, becoming incandescent. /From table/
[Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.84 (1985)]**PEER REVIEWED**

Reaction of lithium acetylene carbide diamino or lithium acetylide ammonia with sulfur dioxide produces fire. /From table/
[Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.84 (1985)]**PEER REVIEWED**

Manganese burns when heated in sulfur dioxide vapor.
[Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.85 (1985)]**PEER REVIEWED**

Fire occurs when reacted with potassium.
[Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.85 (1985)]**PEER REVIEWED**

A violent reaction occurs with sodium and sulfur dioxide.
[Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.85 (1985)]**PEER REVIEWED**

Powdered alkali metal (such as sodium & potassium), water, ammonia, zinc, aluminum, brass, copper [Note: Reacts with water to form sulfurous acid].
[NIOSH. NIOSH Pocket Guide to Chemical Hazards. DHHS (NIOSH) Publication No. 97-140. Washington, D.C. U.S. Government Printing Office, 1997. 288]**QC REVIEWED**

Prior History of Accidents:

Meuse Valley, Belgium (1936). High sulfur dioxide emissions from coal-burning plants combined with light winds to produce several thousand cases of pulmonary irritation and 65 deaths (primary cardiac failure in elderly pt).
[Ellenhorn, M.J. and D.G. Barceloux. Medical Toxicology - Diagnosis and Treatment of Human Poisoning. New York, NY: Elsevier Science Publishing Co., Inc. 1988. 816]**PEER REVIEWED**

Donora, Pennsylvania (1948). High concn of particulate matter and sulfur dioxide emissions form industrial smoke associated with poor environmental mixing of pollutants caused a severe pollution episode. Twenty excess deaths were recorded, and almost half of the city residents developed conjunctival and upper resp irritation along with GI symptoms. These pt later had an incr prevalence of resp disease and incr mortality rates.
[Ellenhorn, M.J. and D.G. Barceloux. Medical Toxicology - Diagnosis and Treatment of Human Poisoning. New York, NY: Elsevier Science Publishing Co., Inc. 1988. 816]**PEER REVIEWED**

London (1952). High particulate matter and sulfur dioxide concn in the absence of air movement produced over 4000 excess deaths.
[Ellenhorn, M.J. and D.G. Barceloux. Medical Toxicology - Diagnosis and Treatment of Human Poisoning. New York, NY: Elsevier Science Publishing Co., Inc. 1988. 816]**PEER REVIEWED**

Immediately Dangerous to Life or Health:

100 ppm
[NIOSH. NIOSH Pocket Guide to Chemical Hazards. DHHS (NIOSH) Publication No. 97-140. Washington, D.C. U.S. Government Printing Office, 1997. 288]**QC REVIEWED**

Protective Equipment & Clothing:

RESPIRATORY PROTECTIVE EQUIPMENT OF A TYPE APPROVED BY OSHA FOR SULFUR DIOXIDE (SO2) SERVICE SHOULD ALWAYS BE READILY AVAILABLE ... LOCATED AS TO BE EASILY REACHED IN CASE OF NEED. WHEN LIQ SULFUR DIOXIDE IS USED, THE EYES SHOULD BE PROTECTED BY USE OF GOGGLES OR LARGE-LENS SPECTACLES.
[National Research Council. Prudent Practices for Handling Hazardous Chemicals in Laboratories. Washington, DC: National Academy Press, 1981. 101]**PEER REVIEWED**

AIR-SUPPLIED MASK OR APPROVED CANISTER ... FACE SHIELD; RUBBER CLOTHING WHERE CONTACT WITH LIQ IS POSSIBLE.
[U.S. Coast Guard, Department of Transportation. CHRIS - Hazardous Chemical Data. Volume II. Washington, D.C.: U.S. Government Printing Office, 1984-5.]**PEER REVIEWED**

Recommendations for respirator selection. Max concn for use: 20 ppm. Respirator Class(es): Any chemical cartridge respirator with cartridge(s) providing protection against the compound of concern. May require eye protection. Any supplied-air respirator. May require eye protection.
[NIOSH. NIOSH Pocket Guide to Chemical Hazards. DHHS (NIOSH) Publication No. 97-140. Washington, D.C. U.S. Government Printing Office, 1997. 289]**QC REVIEWED**

Recommendations for respirator selection. Max concn for use: 50 ppm. Respirator Class(es): Any supplied-air respirator operated in a continuous flow mode. May require eye protection. Any powered, air-purifying respirator with cartridge(s) providing protection against the compound of concern. May require eye protection.
[NIOSH. NIOSH Pocket Guide to Chemical Hazards. DHHS (NIOSH) Publication No. 97-140. Washington, D.C. U.S. Government Printing Office, 1997. 289]**QC REVIEWED**

Recommendations for respirator selection. Max concn for use: 100 ppm. Respirator Class(es): Any chemical cartridge respirator with a full facepiece and cartridge(s) providing protection against the compound of concern. Any air-purifying, full-facepiece respirator (gas mask) with a chin-style, front- or back-mounted canister providing protection against the compound of concern. Any powered, air-purifying respirator with a tight-fitting facepiece and cartridge(s) providing protection against the compound of concern. May require eye protection. Any supplied-air respirator that has a tight-fitting facepiece and is operated in a continuous-flow mode. May require eye protection. Any self-contained breathing apparatus with a full facepiece. Any supplied-air respirator with a full facepiece.
[NIOSH. NIOSH Pocket Guide to Chemical Hazards. DHHS (NIOSH) Publication No. 97-140. Washington, D.C. U.S. Government Printing Office, 1997. 289]**QC REVIEWED**

Recommendations for respirator selection. Condition: Emergency or planned entry into unknown concn or IDLH conditions: Respirator Class(es): Any self-contained breathing apparatus that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode. Any supplied-air respirator that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode in combination with an auxiliary self-contained breathing apparatus operated in pressure-demand or other positive-pressure mode.
[NIOSH. NIOSH Pocket Guide to Chemical Hazards. DHHS (NIOSH) Publication No. 97-140. Washington, D.C. U.S. Government Printing Office, 1997. 289]**QC REVIEWED**

Recommendations for respirator selection. Condition: Escape from suddenly occurring respiratory hazards: Respirator Class(es): Any air-purifying, full-facepiece respirator (gas mask) with a chin-style, front- or back-mounted canister providing protection against the compound of concern. Any appropriate escape-type, self-contained breathing apparatus.
[NIOSH. NIOSH Pocket Guide to Chemical Hazards. DHHS (NIOSH) Publication No. 97-140. Washington, D.C. U.S. Government Printing Office, 1997. 289]**QC REVIEWED**

Wear appropriate personal protective clothing to prevent the skin from becoming frozen from contact with the liquid or from contact with vessels containing the liquid.
[NIOSH. NIOSH Pocket Guide to Chemical Hazards. DHHS (NIOSH) Publication No. 97-140. Washington, D.C. U.S. Government Printing Office, 1997. 289]**QC REVIEWED**

Wear appropriate eye protection to prevent eye contact with the liquid that could result in burns or tissue damage from frostbite.
[NIOSH. NIOSH Pocket Guide to Chemical Hazards. DHHS (NIOSH) Publication No. 97-140. Washington, D.C. U.S. Government Printing Office, 1997. 289]**QC REVIEWED**

Quick drench facilities and/or eyewash fountains should be provided within the immediate work area for emergency use where there is any possibility of exposure to liquids that are extremely cold or rapidly evaporating.
[NIOSH. NIOSH Pocket Guide to Chemical Hazards. DHHS (NIOSH) Publication No. 97-140. Washington, D.C. U.S. Government Printing Office, 1997. 289]**QC REVIEWED**

Preventive Measures:

SRP: Local exhaust ventilation should be applied wherever there is an incidence of point source emissions or dispersion of regulated contaminants in the work area. Ventilation control of the contaminant as close to its point of generation is both the most economical and safest method to minimize personnel exposure to airborne contaminants.
**PEER REVIEWED**

IT HAS BEEN RECOMMENDED THAT WORKERS ... RINSE OUT THEIR MOUTH WITH A 10% SODIUM BICARBONATE SOLUTION DURING WORKING HR ... WORKERS SHOULD BE ENCOURAGED TO PRACTICE SCRUPULOUS PERSONAL HYGIENE ... .
[International Labour Office. Encyclopedia of Occupational Health and Safety. Vols. I&II. Geneva, Switzerland: International Labour Office, 1983. 2123]**PEER REVIEWED**

CAUTION: FOOD & FEED SHOULD BE REMOVED. PROTECT & REMOVE METAL, ELECTRICAL EQUIPMENT, & FABRIC MATERIALS /BEFORE FUMIGATION/.
[Farm Chemicals Handbook 1989. Willoughby, OH: Meister Publishing Co., 1989.,p. C-273]**PEER REVIEWED**

Provide emergency eyewash.
[Sittig, M. Handbook of Toxic and Hazardous Chemicals and Carcinogens, 1985. 2nd ed. Park Ridge, NJ: Noyes Data Corporation, 1985. 813]**PEER REVIEWED**

If liquid ... penetrates through the clothing, remove clothing immediately and flush the skin with water.
[Mackison, F. W., R. S. Stricoff, and L. J. Partridge, Jr. (eds.). NIOSH/OSHA - Occupational Health Guidelines for Chemical Hazards. DHHS(NIOSH) Publication No. 81-123 (3 VOLS). Washington, DC: U.S. Government Printing Office, Jan. 1981.3]**PEER REVIEWED**

SRP: The scientific literature for the use of contact lenses in industry is conflicting. The benefit or detrimental effects of wearing contact lenses depend not only upon the substance, but also on factors including the form of the substance, characteristics and duration of the exposure, the uses of other eye protection equipment, and the hygiene of the lenses. However, there may be individual substances whose irritating or corrosive properties are such that the wearing of contact lenses would be harmful to the eye. In those specific cases, contact lenses should not be worn. In any event, the usual eye protection equipment should be worn even when contact lenses are in place.
**PEER REVIEWED**

If material not involved in fire: Keep material out of water sources and sewers. Attempt to stop leak if without undue personnel hazard. Use water spray to knock-down vapors. Do not use water on material itself. /Sulfur dioxide, liquefied/
[Association of American Railroads. Emergency Handling of Hazardous Materials in Surface Transportation. Washington, DC: Association of American Railroads, Bureau of Explosives, 1994. 1017]**PEER REVIEWED**

Personnel protection: Avoid breathing vapors. Keep upwind. Avoid bodily contact with the material. Do not handle broken packages unless wearing appropriate personal protective equipment. Wash away any material which may have contacted the body with copious amounts of water or soap and water. /Sulfur dioxide, liquefied/
[Association of American Railroads. Emergency Handling of Hazardous Materials in Surface Transportation. Washington, DC: Association of American Railroads, Bureau of Explosives, 1994. 1017]**PEER REVIEWED**

If material leaking (not on fire) consider evacuation from downwind area based on amount of material spilled, location and weather conditions. /Sulfur dioxide, liquefied/
[Association of American Railroads. Emergency Handling of Hazardous Materials in Surface Transportation. Washington, DC: Association of American Railroads, Bureau of Explosives, 1994. 1017]**PEER REVIEWED**

SRP: Contaminated protective clothing should be segregated in such a manner so that there is no direct personal contact by personnel who handle, dispose, or clean the clothing. Quality assurance to ascertain the completeness of the cleaning procedures should be implemented before the decontaminated protective clothing is returned for reuse by the workers. Contaminated clothing should not be taken home at end of shift, but should remain at employee's place of work for cleaning.
**PEER REVIEWED**

Work clothing that becomes wet or significantly contaminated should be removed and replaced. /Liquid/
[NIOSH. NIOSH Pocket Guide to Chemical Hazards. DHHS (NIOSH) Publication No. 97-140. Washington, D.C. U.S. Government Printing Office, 1997. 289]**QC REVIEWED**

Stability/Shelf Life:

Extremely stable to heat, even up to 2000 deg C
[Kirk-Othmer Encyclopedia of Chemical Technology. 3rd ed., Volumes 1-26. New York, NY: John Wiley and Sons, 1978-1984.,p. 22(83) 135]**PEER REVIEWED**

Shipment Methods and Regulations:

No person may /transport,/ offer or accept a hazardous material for transportation in commerce unless that person is registered in conformance ... and the hazardous material is properly classed, described, packaged, marked, labeled, and in condition for shipment as required or authorized by ... /the hazardous materials regulations (49 CFR 171-177)./
[49 CFR 171.2 (7/1/96)]**PEER REVIEWED**

The International Air Transport Association (IATA) Dangerous Goods Regulations are published by the IATA Dangerous Goods Board pursuant to IATA Resolutions 618 and 619 and constitute a manual of industry carrier regulations to be followed by all IATA Member airlines when transporting hazardous materials.
[IATA. Dangerous Goods Regulations. 38th ed. Montreal, Canada and Geneva, Switzerland: International Air Transport Association, Dangerous Goods Board, January, 1997. 217]**PEER REVIEWED**

The International Maritime Dangerous Goods Code lays down basic principles for transporting hazardous chemicals. Detailed recommendations for individual substances and a number of recommendations for good practice are included in the classes dealing with such substances. A general index of technical names has also been compiled. This index should always be consulted when attempting to locate the appropriate procedures to be used when shipping any substance or article.
[IMDG; International Maritime Dangerous Goods Code; International Maritime Organization p.2113 (1988)]**PEER REVIEWED**

Storage Conditions:

Keep container tightly closed and in a well-ventilated place.
[Commission of the European Communities. Legislation on Dangerous Substances - Classification and Labelling in the European Communities. Vol. II. London and Trotman Ltd., 1989. 138]**PEER REVIEWED**

STORAGE TEMP: LESS THAN 130 DEG F
[U.S. Coast Guard, Department of Transportation. CHRIS - Hazardous Chemical Data. Volume II. Washington, D.C.: U.S. Government Printing Office, 1984-5.]**PEER REVIEWED**

Compressed gas cylinders containing sulfur dioxide should be stored in accordance with 29 CFR 1910.101.
[Mackison, F. W., R. S. Stricoff, and L. J. Partridge, Jr. (eds.). NIOSH/OSHA - Occupational Health Guidelines for Chemical Hazards. DHHS(NIOSH) Publication No. 81-123 (3 VOLS). Washington, DC: U.S. Government Printing Office, Jan. 1981.2]**PEER REVIEWED**

Liquid sulfur dioxide may be stored under 3 to 10 atmosphere pressure, or at atmospheric pressure @ -10 deg C with refrigeration to condense evaporating gas.
[Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.11 (1985)]**PEER REVIEWED**

Store in a cool, dry, well-ventilated location. Outside or detached storage is preferred. Isolate from oxidizing materials and alkalies.
[Fire Protection Guide to Hazardous Materials. 12 ed. Quincy, MA: National Fire Protection Association, 1997. ,p. 49-123]**QC REVIEWED**

Cleanup Methods:

1. VENTILATE AREA OF SPILL OR LEAK TO DISPERSE GAS. 2. IF IN GASEOUS FORM, STOP FLOW OF GAS. IF SOURCE OF LEAK IS CYLINDER & LEAK CANNOT BE STOPPED IN PLACE, REMOVE LEAKING CYLINDER TO SAFE PLACE IN OPEN AIR, & REPAIR THE LEAK OR ALLOW ... TO EMPTY. 3. IF IN LIQ FORM, ALLOW TO VAPORIZE.
[Mackison, F. W., R. S. Stricoff, and L. J. Partridge, Jr. (eds.). NIOSH/OSHA - Occupational Health Guidelines for Chemical Hazards. DHHS(NIOSH) Publication No. 81-123 (3 VOLS). Washington, DC: U.S. Government Printing Office, Jan. 1981.3]**PEER REVIEWED**

Approach release from upwind. Stop or control the leak, if this can be done without undue risk. Use water spray to cool and disperse vapors and protect personnel. Control runoff and isolate discharged material for proper disposal. Releases may require isolation or evacuation.
[Fire Protection Guide to Hazardous Materials. 12 ed. Quincy, MA: National Fire Protection Association, 1997. ,p. 49-123]**QC REVIEWED**

Disposal Methods:

SRP: At the time of review, criteria for land treatment or burial (sanitary landfill) disposal practices are subject to significant revision. Prior to implementing land disposal of waste residue (including waste sludge), consult with environmental regulatory agencies for guidance on acceptable disposal practices.
**PEER REVIEWED**

Occupational Exposure Standards:

OSHA Standards:

Permissible Exposure Limit: Table Z-1 8-hr Time Weighted Avg: 5 ppm (13 mg/cu m).
[29 CFR 1910.1000 (7/1/98)]**QC REVIEWED**

Vacated 1989 OSHA PEL TWA 2ppm (5 mg/cu m); STEL 5 ppm (13 mg/cu m) is still enforced in some states.
[NIOSH. NIOSH Pocket Guide to Chemical Hazards. DHHS (NIOSH) Publication No. 97-140. Washington, D.C. U.S. Government Printing Office, 1997. 371]**QC REVIEWED**

Threshold Limit Values:

8 hr Time Weighted Avg (TWA): 2 ppm; 15 min Short Term Exposure Limit (STEL): 5 ppm.
[American Conference of Governmental Industrial Hygienists. TLVs & BEIs: Threshold limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices for 2002. Cincinnati, OH. 2002.54]**QC REVIEWED**

A4; Not classifiable as a human carcinogen.
[American Conference of Governmental Industrial Hygienists. TLVs & BEIs: Threshold limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices for 2002. Cincinnati, OH. 2002.54]**QC REVIEWED**

NIOSH Recommendations:

Recommended Exposure Limit: 10 Hr Time-Weighted Avg: 2 ppm (5 mg/cu m).
[NIOSH. NIOSH Pocket Guide to Chemical Hazards. DHHS (NIOSH) Publication No. 97-140. Washington, D.C. U.S. Government Printing Office, 1997. 288]**QC REVIEWED**

Recommended Exposure Limit: 15 Min Short-Term Exposure Limit: 5 ppm (13 mg/cu m).
[NIOSH. NIOSH Pocket Guide to Chemical Hazards. DHHS (NIOSH) Publication No. 97-140. Washington, D.C. U.S. Government Printing Office, 1997. 288]**QC REVIEWED**

Immediately Dangerous to Life or Health:

100 ppm
[NIOSH. NIOSH Pocket Guide to Chemical Hazards. DHHS (NIOSH) Publication No. 97-140. Washington, D.C. U.S. Government Printing Office, 1997. 288]**QC REVIEWED**

Other Occupational Permissible Levels:

Maximum Allowable Concn (MAC) USSR 10 mg/cu m
[International Labour Office. Encyclopedia of Occupational Health and Safety. Vols. I&II. Geneva, Switzerland: International Labour Office, 1983. 2122]**PEER REVIEWED**

Action level (8 hr): 1 ppm
[Braker W et al; Effects of Exposure to Toxic Gases-First Aid and Medical Treatment, Matheson Gas Products, Lyndhurst, NJ (1977) as cited in Environment Canada; Tech Info for Problem Spills: Sulfur dioxide (Draft) p.75 (1985)]**PEER REVIEWED**

Emergency exposure limits: 150 ppm (5 min); 75 ppm (15 min); 50 ppm (30 min); 25 ppm (60 min)
[Nat'l Research Council Canada; Effects of Sulfur dioxide in the Canadian Environ p.175 (1977) NRCC No. 15015]**PEER REVIEWED**

Emergency Response Planning Guidelines (ERPG): ERPG(1) 0.3 ppm (no more than mild, transient effects) for up to 1 hr exposure; ERPG(2) 3 ppm (without serious, adverse effects) for up to 1 hr exposure; ERPG(3) 15 ppm (not life threatening) up to 1 hr exposure.
[American Industrial Hygiene Association. The AIHA 1999 Emergency Response Planning Guidelines and Workplace Environmental Exposure Level Guides Handbook. American Industrial Hygiene Association. Fairfax, VA 1999.26]**QC REVIEWED**

Manufacturing/Use Information:

Major Uses:

PRESERVING FRUITS; DISINFECTANT IN BREWERIES & FOOD FACTORIES
[Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996. 1535]**PEER REVIEWED**

BLEACHING TEXTILE FIBERS, WICKER WARE, GELATIN, GLUE, BEET SUGARS
[Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996. 1535]**PEER REVIEWED**

SULFONATION OF OILS
[Lewis, R.J., Sr (Ed.). Hawley's Condensed Chemical Dictionary. 12th ed. New York, NY: Van Nostrand Rheinhold Co., 1993 1104]**PEER REVIEWED**

APPLICATION OF SULFUR DIOXIDE OR SULFITES TO VEGETABLES TO BE DEHYDRATED INCR STORAGE LIFE, PRESERVE COLOR & FLAVOR, & AIDS IN RETENTION OF ASCORBIC ACID & CAROTENE.
[Furia, T.E. (ed.). CRC Handbook of Food Additives. 2nd ed. Cleveland: The Chemical Rubber Co., 1972. 145]**PEER REVIEWED**

USED AT 2 TO 3% IN LIQUID GRAIN FUMIGANT AS WARNING GAS. ALSO PRODUCED BY BURNING SULFUR IN CLOSED BUILDING OR OTHER SPACE TO BE FUMIGATED. SUCH FUMIGATION NOW SELDOM PRACTICED.
[Farm Chemicals Handbook 1997. Willoughby, OH: Meister Publishing Co., 1997.,p. C-348]**PEER REVIEWED**

MEDICATION (VET)
**PEER REVIEWED**

As intermediate in the manufacture of sulfuric acid
[Seiler, H.G., H. Sigel and A. Sigel (eds.). Handbook on the Toxicity of Inorganic Compounds. New York, NY: Marcel Dekker, Inc. 1988. 643]**PEER REVIEWED**

CHEM INTERMED FOR SULFUR CHEMS-EG, SODIUM HYDROSULFITE
[SRI]**PEER REVIEWED**

CHEM INTERMED FOR CHLORINE DIOXIDE
[SRI]**PEER REVIEWED**

COMPONENT OF SULFITE WOOD PULPING LIQUORS (CAPTIVE USE)
[SRI]**PEER REVIEWED**

For the manufacture of corn syrups and molasses; in the manufacture of wine to destroy bacteria, mold, and unwanted yeasts, and for sterilization; prevents the formation of nitrosamines in beer
[Seiler, H.G., H. Sigel and A. Sigel (eds.). Handbook on the Toxicity of Inorganic Compounds. New York, NY: Marcel Dekker, Inc. 1988. 647]**PEER REVIEWED**

DEPRESSANT IN FLOTATION OF SULFIDE ORES
[SRI]**PEER REVIEWED**

REDUCING AGENT EG, OF IRON, IN MINERALS PROCESSING
[SRI]**PEER REVIEWED**

OXYGEN SCAVENGER & EXTRACTIVE SOLVENT IN OIL REFINING
[SRI]**PEER REVIEWED**

Used to reduce free chlorine after water treatment, in petroleum refining, in the mining industry in magnesium casting, and as a sulfonating agent in organic chemistry
[Seiler, H.G., H. Sigel and A. Sigel (eds.). Handbook on the Toxicity of Inorganic Compounds. New York, NY: Marcel Dekker, Inc. 1988. 647]**PEER REVIEWED**

CATALYST EG, IN OXIDN OF O-XYLENE
[SRI]**PEER REVIEWED**

CLEANING AGENT OF METALLIC OXIDES IN TILE DRAINS
[SRI]**PEER REVIEWED**

SOLVENT EG, FOR SULFUR TRIOXIDE IN SULFONATION REACTIONS
[SRI]**PEER REVIEWED**

AGENT IN GLASS MANUFACTURE EG, AS ALKALI NEUTRALIZER
[SRI]**PEER REVIEWED**

CHEM INTERMED FOR ACETYL CHLORIDE
[SRI]**PEER REVIEWED**

OXIDIZING AGENT IN LITHIUM PRIMARY BATTERIES
[SRI]**PEER REVIEWED**

LEAK DETECTOR
[SRI]**PEER REVIEWED**

COMPONENT OF CORN STEEPING BATHS
[SRI]**PEER REVIEWED**

Use in manufacture of sodium sulfate, sulfuryl chloride, thionyl chloride, organic sulfonates, glass, wine, ice, industrial & edible protein, vapor pressure thermometers, used in the bleaching of flour, fruit, grain, oil straw, wood pulp & wool; tanning of leather
[Sittig, M. Handbook of Toxic and Hazardous Chemicals and Carcinogens, 1985. 2nd ed. Park Ridge, NJ: Noyes Data Corporation, 1985. 812]**PEER REVIEWED**

... Used in pulp bleaching, sulfite pulping, metal mining/refining, water treatment, and food processing.
[Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.11 (1985)]**PEER REVIEWED**

Manufacturers:

BIT Manufacturing Inc., (Formerly known as Tennessee Chemical Co.), State Highway 68, Copperhill, TN 37317 (429)496-3331; Production site: Copperhill, TN 37317
[SRI. 1997 Directory of Chemical Producers -United States of America. Menlo Park, CA: SRI International 1997.. 908]**PEER REVIEWED**

Coulton Chemical Corp, Hq, 6600 Sylvania Ave, Sylvania, OH 43560, (419) 885-4661; Subsidiary: Cairo Chemical Corp, Cairo, OH 45820
[SRI. 1997 Directory of Chemical Producers -United States of America. Menlo Park, CA: SRI International 1997.. 908]**PEER REVIEWED**

Hoechst Celenese Corp, Hq, Route 202-206 N, Somerville, NJ 08876, (201) 231-2000; Specialty Chemical Group, (address same as Hq); Production site: Bucks, AL 36512
[SRI. 1997 Directory of Chemical Producers -United States of America. Menlo Park, CA: SRI International 1997.. 908]**PEER REVIEWED**

Hydrite Chemical Co., Drawer No. 0948, Brookfield, WI 53008-0948 (414)792-8721; Production site: Waterloo, Iowa 50703
[SRI. 1997 Directory of Chemical Producers -United States of America. Menlo Park, CA: SRI International 1997.. 908]**PEER REVIEWED**

Industrial Chemicals Corp, Hq, 17 Emajagua St, Santurce, PR 00913, (809) 726-3668; Production site: Penuelas, PR 00700
[SRI. 1997 Directory of Chemical Producers -United States of America. Menlo Park, CA: SRI International 1997.. 908]**PEER REVIEWED**

Rhone-Poulenc Inc, Hq, 52 Vanderbilt Ave, New York, NY 10017, (201) 297-0100; Basic Chemical Group; Production sites: Baton Rouge, LA 70821; Hammond, IN 46320; Houston, TX 77012
[SRI. 1997 Directory of Chemical Producers -United States of America. Menlo Park, CA: SRI International 1997.. 908]**PEER REVIEWED**

Thatcher Co., 1905 Fortune Rd., P.O. Box 27407, Salt Lake City, UT 84127, (801)972-4587; Production site: Salt Lake City, UT 84127
[SRI. 1997 Directory of Chemical Producers -United States of America. Menlo Park, CA: SRI International 1997.. 908]**PEER REVIEWED**

Methods of Manufacturing:

(A) BY ROASTING PYRITES IN SPECIAL FURNACES. GAS IS READILY LIQUEFIED BY COOLING WITH ICE & SALT, OR @ A PRESSURE OF 3 ATM. (B) BY PURIFYING & COMPRESSING SULFUR DIOXIDE GAS FROM SMELTING OPERATIONS. (C) BY BURNING SULFUR.
[Lewis, R.J., Sr (Ed.). Hawley's Condensed Chemical Dictionary. 12th ed. New York, NY: Van Nostrand Rheinhold Co., 1993 1104]**PEER REVIEWED**

COMBUSTION OF SULFUR, METALLIC SULFIDES-EG, PYRITE, HYDROGEN SULFIDE OR SULFURIC ACID SLUDGES, RECOVERY BY CONCENTRATION & LIQUEFACTION OF SMELTER STACK GASES; REACTION OF SULFUR TRIOXIDE FROM OLEUM WITH SULFUR; MAY BE MADE FROM GYPSUM (NOT CURRENTLY DONE IN USA)
[SRI]**PEER REVIEWED**

Formulations/Preparations:

GRADES: COMMERCIAL; USP; TECHNICAL; REFRIGERATION; ANHYDROUS 99.98% MIN.
[Lewis, R.J., Sr (Ed.). Hawley's Condensed Chemical Dictionary. 12th ed. New York, NY: Van Nostrand Rheinhold Co., 1993 1104]**PEER REVIEWED**

The main grade of liquid sulfur dioxide is known as the technical, industrial, or commercial grade. This grade contains a minimun of 99.98 wt% sulfur dioxide & is a water white liquid free of sulfur trioxide and sulfuric acid. ... Its most important specification is the moisture content, which is generally set at 100 ppm max. The only other grade sold is the refrigeration grade of liquid sulfur dioxide, which is a premium grade having the same purity and specifications as the industrial grade, except for moisture content, which is specified as 50 ppm max. At least one manufacturer sells a single grade for which specifications have been established as follows: color, APHA 25 max; nonvolatile residue, 25 ppm max; moisture, 50 ppm max.
[Kirk-Othmer Encyclopedia of Chemical Technology. 3rd ed., Volumes 1-26. New York, NY: John Wiley and Sons, 1978-1984.,p. 22(83) 145]**PEER REVIEWED**

Compressed gas: technical, food grades; liquefied gas
[Kuney, J.H. and J.N. Nullican (eds.) Chemcyclopedia. Washington, DC: American Chemical Society, 1988. 214]**PEER REVIEWED**

Consumption Patterns:

CHEMICAL PROFILE: Sulfur Dioxide. Hydrosulfites and other chemicals, 40%; pulp and paper, 23%; food and agriculture (mainly corn processing), 14%; water and waste treatment, 9%; metal and ore refining, 6%; oil refining, 4%; other, 4%.
[Kavaler AR; Chemical Marketing Reporter July 28, p. 32 (1997)]**PEER REVIEWED**

CHEMICAL PROFILE: Sulfur dioxide. Demand: 1996: 385,000 tons; 1997: 390,000 tons; 2001 /projected/: 410,000 tons. (Includes imports, which totaled 15,000-85,000 tons last year; exports are negligible.)
[Kavaler AR; Chemical Marketing Reporter July 28, p. 32 (1997)]**PEER REVIEWED**

U. S. Production:

(1977) 1.39X10+11 G
[SRI]**PEER REVIEWED**

(1982) 1.18X10+11 G
[SRI]**PEER REVIEWED**

(1985) 1.18X10+11 g
[CHEMICAL PRODUCTS SYNOPSIS: Sulfur Dioxide, 1985]**PEER REVIEWED**

(1983) 1.21X10+5 short tons
[BUREAU OF THE CENSUS. CURRENT INDUSTRIAL REPORTS, INORGANIC CHEMICALS, 1987]**PEER REVIEWED**

(1984) 1.34X10+5 short tons
[BUREAU OF THE CENSUS. CURRENT INDUSTRIAL REPORTS, INORGANIC CHEMICALS, 1987]**PEER REVIEWED**

(1986) 1.96X10+5 short tons
[BUREAU OF THE CENSUS. CURRENT INDUSTRIAL REPORTS, INORGANIC CHEMICALS, 1987]**PEER REVIEWED**

(1987) 2.29X10+5 short tons
[BUREAU OF THE CENSUS. CURRENT INDUSTRIAL REPORTS, INORGANIC CHEMICALS, 1987]**PEER REVIEWED**

U. S. Imports:

(1977) 5.17X10+10 G
[SRI]**PEER REVIEWED**

(1982) 2.26X10+10 G
[SRI]**PEER REVIEWED**

(1985) 2.33X10+7 g
[BUREAU OF THE CENSUS. U.S. IMPORTS FOR CONSUMPTION AND GENERAL IMPORTS 1985 p.1-574]**PEER REVIEWED**

(1986) 5.72X10+4 short tons
[BUREAU OF THE CENSUS. US IMPORTS FOR CONSUMPTION AND GENERAL IMPORTS 1986 P.1-520]**PEER REVIEWED**

U. S. Exports:

(1978) 1.62X10+9 G
[SRI]**PEER REVIEWED**

(1983) 5.38X10+9 G
[SRI]**PEER REVIEWED**

(1985) 1.60X10+9 g
[BUREAU OF THE CENSUS. U.S. EXPORTS, SCHEDULE E, 1985 p.2-92]**PEER REVIEWED**

(1987) 1.88X10+5 lb
[BUREAU OF THE CENSUS. U. S. EXPORTS, SCHEDULE E, DECEMBER 1987, P.2-99]**PEER REVIEWED**

Laboratory Methods:

Analytic Laboratory Methods:

NIOSH 204: ANALYTE: SULFUR DIOXIDE; MATRIX: AIR; RANGE: 2 TO 625 MG/CU M IN 100 LITER OF AIR; PROCEDURE: MASS SPECTROMETRIC; PRECISION (COEFFICIENT OF VARIATION): 0.002 AT 13 MG/CU M
[U.S. Department of Health, Education Welfare, Public Health Service. Center for Disease Control, National Institute for Occupational Safety Health. NIOSH Manual of Analytical Methods. 2nd ed. Volumes 1-7. Washington, DC: U.S. Government Printing Office, 1977-present.p. V1 204-1]**PEER REVIEWED**

Determination of sulfur dioxide in food ... by distilling sulfur dioxide from acidulated samples into solution of hydrogen peroxide, followed by acidimetric titration of sulfuric acid ... produced.
[Kirk-Othmer Encyclopedia of Chemical Technology. 3rd ed., Volumes 1-26. New York, NY: John Wiley and Sons, 1978-1984.,p. 22(83) 146]**PEER REVIEWED**

NIOSH 146: ANALYTE: SULFUR DIOXIDE; MATRIX: AIR; RANGE: 0.01-10 PPM; PROCEDURE: TITRATION; PRECISION: + or - 10% BELOW THE 0.1 PPM LEVEL
[U.S. Department of Health, Education Welfare, Public Health Service. Center for Disease Control, National Institute for Occupational Safety Health. NIOSH Manual of Analytical Methods. 2nd ed. Volumes 1-7. Washington, DC: U.S. Government Printing Office, 1977-present.p. V1 146-1]**PEER REVIEWED**

NIOSH 160: ANALYTE: SULFUR DIOXIDE; MATRIX: AIR; PROCEDURE: COLORIMETRIC; RANGE: 0.003-5.0 PPM SULFUR DIOXIDE; PRECISION: + or - 5% STANDARD DEVIATION
[U.S. Department of Health, Education Welfare, Public Health Service. Center for Disease Control, National Institute for Occupational Safety Health. NIOSH Manual of Analytical Methods. 2nd ed. Volumes 1-7. Washington, DC: U.S. Government Printing Office, 1977-present.p. V1 160-1]**PEER REVIEWED**

NIOSH 163: ANALYTE: SULFUR DIOXIDE; MATRIX: AIR; RANGE: 0.01-5 MG; PROCEDURE: TITRATION WITH BARIUM PERCHLORATE; PRECISION: 4% RELATIVE STANDARD DEVIATION AT 2.5 PPM
[U.S. Department of Health, Education Welfare, Public Health Service. Center for Disease Control, National Institute for Occupational Safety Health. NIOSH Manual of Analytical Methods. 2nd ed. Volumes 1-7. Washington, DC: U.S. Government Printing Office, 1977-present.p. V1 163-1]**PEER REVIEWED**

NIOSH S308: ANALYTE: SULFUR DIOXIDE; MATRIX: AIR; RANGE: 6.6-26.8 MG/CU M; PROCEDURE: TITRATION WITH BARIUM PERCHLORATE; PRECISION (COEFFICIENT OF VARIATION): 0.054
[U.S. Department of Health, Education Welfare, Public Health Service. Center for Disease Control, National Institute for Occupational Safety Health. NIOSH Manual of Analytical Methods. 2nd ed. Volumes 1-7. Washington, DC: U.S. Government Printing Office, 1977-present.p. V4 S308-1]**PEER REVIEWED**

NIOSH 6004: Analyte: sulfite and sulfate ions; Matrix: air; Sampler: filter (cellulose + potassium hydroxide; preceded by 0.8-um cellulose ester membrane); Flow rate: 0.5 to 1.5 l/min; Vol: min:15 l at 0.5 ppm, max: 400 l; Sample stability: not determined; Technique: ion chromatography; Desorption: 10 ml 3 mM sodium bicarbonate/2.4 mM sodium carbonate; Range: 0.02 to 0.2 mg sulfur dioxide/sample; Precision (Sr): 0.05 @ 0.05 to 1 mg sulfur dioxide/sample; Est limit of detection: 0.01 mg sulfur dioxide; Interferences: Bromide has same retention time as sulfite on these columns. Sulfur trioxide gas, if present in dry atmospheres, may give a positive interference in sulfur dioxide determinations.
[U.S. Department of Health and Human Services, Public Health Service. Centers for Disease Control, National Institute for Occupational Safety and Health. NIOSH Manual of Analytical Methods, 3rd ed. Volumes 1 and 2 with 1985 supplement, and revisions. Washington, DC: U.S. Government Printing Office, February 1984.p. V2 6004-1]**PEER REVIEWED**

A range of 0.5 to 5 ppm of sulfur dioxide in air may be determined with the use of a Drager gas detector tube for sulfur dioxide. A known volume of air is drawn through a Drager gas detector tube for sulfur dioxide using a Drager multi-gas detector pump. A colour change of the blue indicating layer to white indicates sulfur dioxide. The colour change is based on the reaction between sulfur dioxide and iodine in the presence of starch.
[Leichnitz K; Detector Tube Han 4 th ed Lubeck, Germany (1979) as cited in Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.94 (1985)]**PEER REVIEWED**

Concentrations geater than 6 mg/l (ppm) of sulfur dioxide as sulfite ion in water may be determined by titration using an electrometric indicator. A mimimum 2 l volume of representative sample is collected in an appropriate container. A 5 ml volume of 50 percent hydrochloric acid, 5 ml of potassium iodide (50 g/l), and 5 ml of 0.5 N potassium iodate are added as well as the electrodes of a deadstop electrometric titrator. The starch indicator is prepared by making a paste of 6 g arrowroot starch with cold water. The paste is the poured into 1 l of boiling water; 20 g of potassium hydroxide are added with stirring and the mixture is left to stand for 2 hours. A 6 ml volume of glacial acetic acid is added and the pH adjusted to 4.0 using concentrated hydrochloric acid. The mixture is stored in a glass stoppered bottle. The sample analysis continues as follows. The excess iodine chloride in the sample solution is titrated with 0.01 N sodium thiosulphite solution to an electrometric endpoint. A reagent blank must be titrated.
[ASTM; Annual Book of ASTM Standards, Part 31, Water, Philadelphia PA (1980) as cited in Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.94 (1985)]**PEER REVIEWED**

Sulfur dioxide may be determined as sulfite ion in water. A 2 ml volume of sample is placed in a test tube and made basic by adding 6 M ammonium hydroxide, then adding 2 ml in excess. A 2 ml volume of 0.5 M tetraammine zinc nitrate solution is added. If a precipitation forms, it is discarded. A 3 ml volume of 4.4 M strontium nitrate is added to the supernatant. The mixture is stirred thoroughly and left to stand for 10 minutes. The supernatant is discarded. The precipitate is treated with 2 ml of 4.4 M strontium nitrate solution and the washings discarded. A 1 ml aliquot of 1 M barium chloride solution and 1 ml of 6 M hydrochloric acid are each added to the precipitate. The mixture is centrifuged and any residue is discarded. The supernatant is decanted into a clean test tube. Drop wise addition of 0.1 M iodine-potassium iodide is continued until the solution becomes very light yellow. The formation of a finely divided precipitate indicates sulphite.
[Welcher FJ, Hahn RB; Semimicro Qualitative Analysis D Van Nostrand Co Inc, Princeton NJ p.456-7 (1955) as cited in Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.94-5 (1985)]**PEER REVIEWED**

Concentrations greater tha 3 ppm of sulfur dioxide as sulfate ion may be determined using ion chromatography. A 5 g sample of soil is collected and extracted with 0.001 M lithum chloride solution, centrifuged, and filtered. The sample solution is injected into an ion chromatograph and quantitated using retention times and peak heights. The method is simple but requires specialized equipment.
[Wetzel R, Menear J; Application Note 8. Dionex Corp, Sunydale CA (1978) as cited in Environment Canada; Tech Info for Problem Spills: Sulfur Dioxide (Draft) p.95 (1985)]**PEER REVIEWED**

Sampling Procedures:

NIOSH 146: ANALYTE: SULFUR DIOXIDE; MATRIX: AIR; PROCEDURE: COLLECTION VIA IMPINGER PEROXIDE ABSORPTION
[U.S. Department of Health, Education Welfare, Public Health Service. Center for Disease Control, National Institute for Occupational Safety Health. NIOSH Manual of Analytical Methods. 2nd ed. Volumes 1-7. Washington, DC: U.S. Government Printing Office, 1977-present.p. V1 146-1]**PEER REVIEWED**

NIOSH 160: ANALYTE: SULFUR DIOXIDE; MATRIX: AIR; PROCEDURE: COLLECTION VIA IMPINGER
[U.S. Department of Health, Education Welfare, Public Health Service. Center for Disease Control, National Institute for Occupational Safety Health. NIOSH Manual of Analytical Methods. 2nd ed. Volumes 1-7. Washington, DC: U.S. Government Printing Office, 1977-present.p. V1 160-1]**PEER REVIEWED**

NIOSH 204: ANALYTE: SULFUR DIOXIDE; MATRIX: AIR; PROCEDURE: SORPTION ON MOLECULAR SIEVE 5A, THERMAL DESORPTION
[U.S. Department of Health, Education Welfare, Public Health Service. Center for Disease Control, National Institute for Occupational Safety Health. NIOSH Manual of Analytical Methods. 2nd ed. Volumes 1-7. Washington, DC: U.S. Government Printing Office, 1977-present.p. V1 204-1]**PEER REVIEWED**

NIOSH 163: ANALYTE: SULFUR DIOXIDE; MATRIX: AIR; COLLECTION VIA IMPINGER BY PEROXIDE ABSORPTION
[U.S. Department of Health, Education Welfare, Public Health Service. Center for Disease Control, National Institute for Occupational Safety Health. NIOSH Manual of Analytical Methods. 2nd ed. Volumes 1-7. Washington, DC: U.S. Government Printing Office, 1977-present.p. V1 163-1]**PEER REVIEWED**

NIOSH S308: ANALYTE: SULFUR DIOXIDE; MATRIX: AIR; PROCEDURE: BUBBLE COLLECTION
[U.S. Department of Health, Education Welfare, Public Health Service. Center for Disease Control, National Institute for Occupational Safety Health. NIOSH Manual of Analytical Methods. 2nd ed. Volumes 1-7. Washington, DC: U.S. Government Printing Office, 1977-present.p. V4 S308-1]**PEER REVIEWED**

NIOSH 6004: Analyte: sulfite and sulfate ions; Matrix: air; Sampler: filter (cellulose + potassium hydroxide; preceded by 0.8 um cellulose ester membrane); Flow rate: 0.5 to 1.5 l/min; Vol: min: 15 l at 0.5 ppm, max: 400 l; Sample stability: not determined; Sulfur dioxide is collected in the back (treated) filter. Sulfuric acid, sulfate salts, and sulfide salts are collected on the front filter and may be quantitated as total particulate sulfate and sulfite.
[U.S. Department of Health and Human Services, Public Health Service. Centers for Disease Control, National Institute for Occupational Safety and Health. NIOSH Manual of Analytical Methods, 3rd ed. Volumes 1 and 2 with 1985 supplement, and revisions. Washington, DC: U.S. Government Printing Office, February 1984.p. V2 6004-1]**PEER REVIEWED**

Special References:

Special Reports:

OSHA; Public Hearings on Occupational Standards for Sulfur Dioxide: Statement of Edward Baier (NIOSH) (May 1977) PB 83-182485

WHO; Environ Health Criteria: Sulfur Dioxide (1979)

Monitoring and Assessment Research Centre; Atmospheric Pathways of Sulphur Compounds Report #7 (1978)

Miller JE; Recent Adv Phytochem 21 (Phytochem Eff Environ Compd): 55-100 (1987) A review and discussion with 182 refs. on the effect of ozone and sulfur dioxide on the growth, biomass, and yield in plants as well as their physiol effects (photosynthesis, respiration, and cellular mechanisms).

Richardson D HS; BOT J Linn Soc 96 (1) 31-44 (1988) This review summarizes the effects of the various components of air pollution including metals, sulfur dioxide and acid rain. The mechanisms leading to the accumulation of elements by lichens or induction of damage by air pollutants are discussed.

Synonyms and Identifiers:

Synonyms:

Caswell Number 813
**PEER REVIEWED**

EPA Pesticide Chemical Code 077601
**PEER REVIEWED**

Schwefeldioxyd (German)
**PEER REVIEWED**

SIARKI DWUTLENEK (POLISH)
**PEER REVIEWED**

SULFUR DIOXIDE (SO2)
**PEER REVIEWED**

SULFUROUS ACID ANHYDRIDE
**PEER REVIEWED**

SULFUROUS ANHYDRIDE
**PEER REVIEWED**

SULFUROUS OXIDE
**PEER REVIEWED**

SULFUR OXIDE
**PEER REVIEWED**

SULFUR OXIDE (SO2)
**PEER REVIEWED**

SULPHUR DIOXIDE
**PEER REVIEWED**

Formulations/Preparations:

GRADES: COMMERCIAL; USP; TECHNICAL; REFRIGERATION; ANHYDROUS 99.98% MIN.
[Lewis, R.J., Sr (Ed.). Hawley's Condensed Chemical Dictionary. 12th ed. New York, NY: Van Nostrand Rheinhold Co., 1993 1104]**PEER REVIEWED**

The main grade of liquid sulfur dioxide is known as the technical, industrial, or commercial grade. This grade contains a minimun of 99.98 wt% sulfur dioxide & is a water white liquid free of sulfur trioxide and sulfuric acid. ... Its most important specification is the moisture content, which is generally set at 100 ppm max. The only other grade sold is the refrigeration grade of liquid sulfur dioxide, which is a premium grade having the same purity and specifications as the industrial grade, except for moisture content, which is specified as 50 ppm max. At least one manufacturer sells a single grade for which specifications have been established as follows: color, APHA 25 max; nonvolatile residue, 25 ppm max; moisture, 50 ppm max.
[Kirk-Othmer Encyclopedia of Chemical Technology. 3rd ed., Volumes 1-26. New York, NY: John Wiley and Sons, 1978-1984.,p. 22(83) 145]**PEER REVIEWED**

Compressed gas: technical, food grades; liquefied gas
[Kuney, J.H. and J.N. Nullican (eds.) Chemcyclopedia. Washington, DC: American Chemical Society, 1988. 214]**PEER REVIEWED**

Shipping Name/ Number DOT/UN/NA/IMO:

UN 1079; Sulfur dioxide, liquefied

IMO 2.3; Sulfur dioxide, liquefied

Standard Transportation Number:

49 042 90; Sulfur dioxide

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