With the advent, in 2005, of a practical ozone-based sterilizer by TSO₃, Inc. (Model 125L), and its subsequent installation into sterile processing facilities, ChemDAQ added ozone monitoring to its product line. However, is it really necessary to monitor ozone in a sterile processing department (SPD), based on the supposed hazard of having an ozone sterilizer installed?

The answer is NO, for essentially the same reasons that you don't have to monitor hydrogen peroxide—based on the presence of a Sterrad^® hydrogen peroxide gas plasma sterilizer—either.

Hazard Versus Risk

By way of various documents of their own, and reference to OSHA regulations, ChemDAQ makes the point—which was never in dispute—that regulatory compliance levels exist not only for ethylene oxide, but for hydrogen peroxide and ozone, as well. They then go on to note that gas leaks from sterilizers are known to occur. Of course, all the available data describes leaks from ethylene oxide sterilizers.

Any reported incidents involving the Sterrad^® unit concern minor burns from liquid hydrogen peroxide, and no incidents of any kind have yet been reported (as of May, 2008) for the new ozone sterilizers.

It is important to note that just because regulatory compliance levels exist for a chemical, and even if that chemical may be present in a workplace, one does not necessarily have to monitor it. Indeed, ChemDAQ seems to be confusing "hazard" and "risk."

Cefic—The European Chemical Industry Council—offers some helpful definitions for us:

"Hazard" is the way in which an object, situation, or substance may cause harm.

"Exposure" is the extent to which the likely recipient of the harm is exposed to—or can be influenced by—the hazard.

"Risk" is the chance that harm will actually occur.

As Cefic expresses it:

Risk = Hazard + Exposure

OSHA and other regulatory bodies are well aware of this. That's why OSHA defined the action level. This is usually one-half of the allowable 8-hour time weighted average for the substance in question. The only significance of the action level is as a benchmark during the initial screening of a workplace. If concentration levels of the chemical in question are greater than or equal to this action level, then regular monitoring will have to be done. For certain compounds, such as ethylene oxide, OSHA has formulated detailed guidelines on the initial monitoring process.

As but a moment's reflection will show, there are countless workplaces that might have present any number of hazardous substances, but for a variety of reasons, including quantity, storage environment, engineering controls, or work practices, these materials pose no risk whatsoever to employees, and are therefore not monitored. ChemDAQ itself acknowledges that:

"...a fully functioning Sterrad^® will contain less than 0.1 ppm hydrogen peroxide, and TSO₃ reports that the 125L will emit less than 0.02 ppm ozone in its exhaust."

How All This Affects SPD Employees

Consider that the OSHA Permissible Exposure Limit (PEL) for Ozone is 0.1 ppm, based on an 8-hour time weighted average. Note from the above data that as a point source, the 125L emits less than 0.02 ppm ozone.

As part of TSO₃'s Premarket Notification [Section 510(k)] submission, data was included as to ambient ozone concentrations that could be measured in the breathing zone of those in close proximity to the sterilizer. These were well below OSHA regulatory levels. Moreover, it was found that:

"...TSO3 125L Ozone Sterilizer could be installed as a free standing unit or recessed behind a wall. No exhaust gas ventilation duct is required in a room that is adequately ventilated."

By the same token, corresponding data was submitted on the Sterrad^® regarding hydrogen peroxide, during its 510(k) processing, and it too was well below regulatory compliance levels.

Ethylene oxide is monitored because of documented effects of long-term exposure—especially pre-OSHA—and its classification as "carcinogenic to humans" by IARC. In contrast, no such body of data exists for either hydrogen peroxide or ozone, as applied to sterilizer leakage.

Promotion of extreme worst case scenarios, whereby leaks "could" occur—in an effort to sell additional monitoring capability—is foolish and irresponsible.