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According to the U.S. Environmental Protection Agency, burning plastics and other materials containing chlorine creates dioxin, which falls on land and water, and gets incorporated into food eaten by animals and fish. Humans then eat meat, fish and dairy products containing concentrated dioxin. The EPA estimates that 95 percent of dioxin in humans comes from eating animal fats.
In a letter, the Wisconsin Department of Health and Family Services calls on the Department of Natural Resources to study cancer risk from French Island dioxin emissions in the food supply, as well as to test the soil for dioxin contamination.
"Because of the affinity for some toxins (particularly dioxins) to bioaccumulate in the food supply, a more deliberate food chain evaluation of air emissions is necessary," according to the letter from chief medical officer Dr. Henry A. Anderson and toxicologist Mark A. Werner of DHFS. "We recognize our agencies' shared commitment to protecting the health of Wisconsin citizens, and we are committed to working with your agency to address this important public health issue."
But DNR officials say they don't have the budget or the scientific resources to do such studies routinely. No decision has been made on whether to do the studies requested by DHFS.
Xcel Energy spokesman Brian Elwood said Friday the company has no comment on the issue of additional cancer risk studies.
The DNR has proposed issuing a new pollution control permit to Xcel's French Island incinerator, which burns a mixture of refuse-derived fuel, wood waste and old railroad ties to generate electricity.
In reports to the U.S. Environmental Protection Agency, Xcel estimates French Island emitted 28 grams of dioxins in 2000, which is more than all of Illinois' power plants combined. Xcel officials say that $10.8 million in new pollution-control equipment being installed this year will dramatically improve the plant's emissions and bring it into compliance with the federal Clean Air Act.
Studies show that municipal solid waste incinerators, which burn plastics, are among the largest producers of dioxin, a family of chlorinated chemicals. Other sources are medical waste incinerators, cement kilns, iron foundries and backyard garbage burners.
Department of Natural Resources staff estimated the cancer risk from inhaling six contaminants, including dioxin, in deciding whether to issue a new permit to French Island. Generally, government begins warning people and issuing regulations when a cancer risk reaches 1 in 1 million. Using computer models, DNR estimated the inhalation risk as 5.96 in 100 million at the nearest home north of the plant. At the point of maximum impact, 40 meters south-southeast of the plant (where the Black and Mississippi rivers meet) the inhalation cancer risk is 2.78 in 10 million.
Environmental groups have criticized DNR for relying on inhalation studies for French Island, because 98 percent of dioxin exposure comes from the food chain, according to the EPA.
Over the last decade, EPA has been reassessing dioxin's dangers and is expected to finish the job later this year. In 2000, the EPA said the risk for the general population "may exceed 1 in 1,000 increased chance of experiencing cancer related to dioxin." That's 10 times higher than the EPA estimated in 1994.
The EPA also says that "fetuses, infants and children may be more sensitive to dioxin exposure because of their rapid growth and development. Data on risks to children are limited, however, and it is not known if the children in the general population are experiencing adverse effects from dioxin. Although breast milk appears to be a significant source of dioxin exposure for nursing infants, the overwhelming body of evidence supports the health benefits of breastfeeding despite the potential presence of dioxin."
In an interview, Werner said that in a situation where the underlying risk from dioxin is so high, regulators have to consider whether any additional contamination is acceptable. "As our chief medical officer says, 'The risk cup is already full,'" Werner said.
Jeff Myers, an environmental toxicologist with the DNR, said the agency typically does inhalation risk studies when it issues air pollution permits. Myers recalled only one DNR study that went beyond the inhalation risks, which was for an incinerator at Ixonia, Wis., between Milwaukee and Madison.
Myers said that studying cancer risks from air pollution reaching the food chain are very complicated, and require many assumptions. "It's educated guessing," he said.
Myers agrees that most dioxin exposure comes from food. But he said the DNR has not issued any permits requiring monitoring of dioxin levels in food or fish or soil.
"We haven't done it before, and we're not sure how to do it," Myers said.
There are other problems of who would do the monitoring and who would pay for it, he said. "The budget of the air program is pretty tight."
In the letter to DNR, Werner acknowledged that it's harder to do studies on food chain exposures than inhalation exposures. And he agrees that food chain studies rely on "a large number of assumptions ... that often make their interpretation contentious."
But just because it's more difficult doesn't mean the state shouldn't do it, Werner said. "The difficulties associated with this analysis, however, do not make the analysis less important or less necessary for this and similar facilities."
Werner and Anderson also suggest DNR do other studies. "Because of the slow rate at which environmental dioxins degrade, the community may be subject to risk from dioxin residues in soil," according to the letter. "DNR should conduct soil sampling on French Island and other locations as needed to evaluate what health risk exists from the past operation of this facility."
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