By Jeremiah Stettler
Sunday, April 4, 2004
A chasm gapes along the Tittabawassee River that even the scientific community can't bridge.
The divide is dioxin - a contaminant born of combustion and other industrial processes that has split public opinion concerning the toxin's potential health effects.
The controversy is no less pronounced in scientific literature, where toxicologists bicker over the harm done by contamination levels found along the Tittabawassee.
Some call dioxin a proven cancer-causer that threatens human health at any level.
Others say the toxin produces no long-lasting health effects, even when people are exposed to concentrations above 1,000 parts per trillion - the federal health standard.
The U.S. Environmental Protection Agency has immersed itself in the toxin controversy for 13 years, hoping to determine through a 3,000-plus-page report the health effects of dioxin.
The agency's report, which remains in draft form, labels the most insidious form of dioxin a proven cancer-causer.
"It is a known human carcinogen," said Christopher J. Portier, director of the environmental toxicology program at the National Institutes of Environmental Health Science. "There's no doubt about it."
Portier has participated in the World Health Organization's review of dioxin and is a joint-author of the EPA's dioxin analysis.
But the form of dioxin mentioned above is not the only contaminant along the banks of the Tittabawassee. Soil samples reveal a mixture of dioxin-like compounds that the EPA lists as "likely human carcinogens."
Yet a question lingers over contamination found in the Tittabawassee: Neither the report nor experts can say how dioxin levels found in the soil downstream of Dow will affect riverside residents.
Some toxicologists say the contaminant is exposing residents to an increased cancer risk. Others say the levels are too low to fret about.
"The majority of the scientific community would conclude that dioxin at high levels is a health concern," Portier said. "But how high is high? That's where it gets very complicated."
Digging into the details
The term "dioxin" is the name of a family of pollutants that causes similar toxic effects but have varying levels of potency.
The real trouble-maker is 2,3,7,8 tetrachlorodibenzo-p-dioxin - a toxin that gained notoriety in the 1970s with the aerial spraying of Agent Orange in Vietnam.
The United States defoliated more than 3.5 million acres of Southeast Asian battlefield with the herbicide, hoping to deprive Vietnamese forces of their hiding places.
But the herbicide, manufactured by Dow and nearly a dozen other U.S. industries, came under attack.
Studies found that dioxin, an impurity in the herbicide, caused birth defects in rodents - a discovery that prompted a rash of health-related claims by Vietnam veterans.
Since then, the dioxin debate has gained momentum with the evacuation of entire communities such as Times Beach, Mo., where government officials unearthed high dioxin concentrations in the soil.
The source of the toxin generally is the same - combustion, federal health officials say.
Dioxin springs from waste incinerators, forest fires and even barbecue pits.
It also grows from the manufacturing of herbicides and paper.
Dioxin then is carried to humans, most prominently through the food supply.
Federal health officials estimate that 95 percent of a person's dioxin intake stems from eating fatty meats, fish and high-fat dairy products that contain the toxin.
However, dioxin also may come through eating soil, inhaling contaminated dust or absorbing the pollutant through one's skin - exposure paths that are particularly relevant to the Tittabawassee River debate.
The state Department of Community Health could not say how much dioxin enters a person's blood through soil contamination, but officials there hope to answer that question soon.
The department has announced a pilot investigation of 25 floodplain residents along the Tittabawassee to determine how much dioxin reaches residents' bloodstreams through such contamination. It will provide no conclusive evidence, but likely lead to a larger exposure investigation into human dioxin levels.
State officials say the study is worthwhile, particularly when soil samples along the river found dioxin levels as high as 7,200 parts per trillion - 80 times the state standard.
Dow officials say that information is key to determining the health risks of river residents.
"It is unclear how much (dioxin) is absorbed," said Michael L. Carson, medical director for Dow's Midland facility. "No one knows. That's an important question to ask because without exposure there can't be toxicity."
Even without further data, however, state officials maintain that the health standard of 90 parts per trillion is appropriate protecting the health of Tittabawassee residents.
Steven E. Chester, director of the Department of Environmental Quality, wrote in a letter The Saginaw News obtained that dioxin levels along the Tittabawassee are high enough to cause concern.
The federal standard of 1,000 parts per trillion, he wrote, "was never intended to represent a concentration in soil that is acceptable for long-term, residential exposure without any further type of evaluation."
Even if dioxin levels fall below the federal standard, Chester wrote the cleanup efforts required of Dow are based on "sound science" and are needed to protect human health.
Reality or ruse?
Jean Hohman never was afraid of the water - even when it shimmered. She bathed in the Tittabawassee River as a child, canoed near the Center Road bridge and watched her children cast fishing lines into the water years later.
That didn't change when state Department of Environmental Quality declared the floodplain a hazardous waste facility because of dioxin contamination. "I just feel bad for these people because they are worrying for nothing," said Hohman, who lived along the Tittabawassee and who boasts of a clean medical history. "If there was a lot of dioxin in that river, then we'd be radiating with it."
While Hohman claims the toxin has no effect, other residents blame dioxin for major health problems. They claim dioxin has erased their property values and deprived them of the emotional security of mowing their lawn without a mask or letting their children run barefoot in the back yard.
Cassandra J. Tucker, 52, can't escape the toxin. She says it lingers four decades after she moved from the river.
Tucker spent her childhood along the Tittabawassee, cultivating the family's acre-and-a-half garden. She cut furrows into the soil with a child-sized hoe and pressed in corn, tomato and pepper seeds.
Today, the Mount Pleasant resident can't help but wonder if dioxin somehow is to blame for the family's illnesses.
She speaks of congenital birth defects, mental retardation and learning disabilities in subsequent generations. She also talks of allergies, chronic fatigue and arthritis.
"There is nothing to support those claims," responded Leonard F. Heinzman, 57, who has lived along the river for nine years. "The science isn't there."
Or is it?
Peter deFur, an associate professor in the Center for Environmental Studies at Virginia Commonwealth University in Richmond and co-chairman of the latest peer review of the EPA's dioxin analysis, argues that dioxin has produced "clear and compelling evidence" of multiple health effects.
He noted reproductive problems, diabetes, birth defects, liver ailments and increased cancer rates in humans.
"This is far from a junk science," he said. "That is the last thing it is." Though deFur said the toxin could lend itself to "bandwagon" behavior - or people blaming unrelated illnesses on the pollutant - he believes dioxin is a legitimate health concern even at any level.
"It increases the threat of cancer at any threshold," he said.
In cases such as the Tittabawassee River, deFur said low levels of the contaminant may accumulate in the body and elevate residents' cancer risk. Federal health officials estimate that dioxin lingers in the body, exhibiting a half-life of seven to 10 years.
"The cause for concern is because it is so widespread," he said. "We can't put our finger on the map and put a fence around it."
Other scientists question the harm caused by low-level pollution.
Michael D. Shaw, a biochemist and chief executive officer of the gas-detection company Interscan Corp. in Los Angeles, labeled dioxin "extraordinarily toxic."
However, contamination levels along the Tittabawassee leave little to worry about, he said.
State Department of Environmental Quality soil samples revealed dioxin levels near or below the federal safety standard of 1,000 parts per trillion, said Shaw, who believes that standard adequately protects human health.
He acknowledged that dioxin, as a carcinogen, may present a health risk at any level. But he said the risk is low enough to guard against dioxin-related health conditions.
"Flying an airplane is more of a risk than developing some life-threatening health problem because of dioxin," he said.
What Dow says
Dow maintains that residents along the Tittabawassee are not exposed to an undue health risk.
Though some soil samples have revealed dioxin levels that exceed the state safety standard of 90 parts per trillion, Dow officials believe exposure to the pollutant is limited.
"With regard to dioxin and health, there's a great deal of conflicting information, and we understand that people are concerned," said Susan Carrington, vice president and director of Dow's Michigan Dioxin Initiative.
"Please remember, however, that the dioxins and (a related compound called) furans have to come off the dirt and get into your body - actually into your bloodstream - before there is any potential for a health risk.
"Based on everything we know, it's unlikely that anyone in this community has absorbed enough dioxin from soils to have any health effects."
Company officials noted that some of the highest samples were unearthed more than a foot beneath the soil - depths that leave little opportunity for exposure.
Dow said proof of dioxin-related health effects remains elusive to the science community. Officials cited 17 studies of company employees who were exposed to the contaminant but have exhibited cancer rates no higher than the general population.
The studies track nearly 2,200 employees of Dow's herbicide production facility, dating to 1940, that were exposed to high levels of dioxin. Though the company has not sampled employees' blood, it found a severe acne-like condition in 11 percent of the workers, which typically denotes high exposure.
Carson said the studies have revealed no increase in cancer rates, diabetes or other major health problems.
"Based on what we know about the science and the levels of dioxin in communities elsewhere, I don't think there is reason to believe that the health of this community is being impacted."
What the EPA says
Federal health officials maintain that the most egregious form of dioxin - 2,3,7,8 Tetrachlorodibenzo-p-dioxin - is a proven carcinogen to humans. The rest fit into a lower category of "likely" human carcinogens.
The toxin is linked at high levels to increased cancer rates, cardiovascular disease, diabetes, birth defects and blood disease.
At low levels, officials say, the health effects are more subtle. They may affect thyroid function, immune function, learning abilities and behavior in developing fetuses.
Other effects of dioxin, such as changes in liver enzymes, hormonal effects and the nervous system, occur in many animals, including humans.
"Based on the available information, dioxins are believed to have the potential to cause a wide range of adverse effects in humans," a report by the state Department of Environmental Quality reads.
Then again, it all depends on exposure, officials say.