JOHN FLESHER AP Environmental Writer — October 2, 2009
A scientific analysis of dioxin exposure near a Dow Chemical Co. plant in Midland will be of little use in planning a long-delayed cleanup, government regulators said Thursday.
Dow paid for the study done by a University of Michigan team and designed partly to help officials decide how to deal with dioxin pollution in a 50-mile-long watershed including the Tittabawassee and Saginaw rivers and Lake Huron's Saginaw Bay. For decades, the company's plant released dioxins and related chemical byproducts believed to cause cancer.
The study was well done and produced credible information, said the U.S. Environmental Protection Agency, which is negotiating details of the cleanup with Dow and state officials. But the absence of crucial data limits its usefulness, an EPA review said.
"We don't see that it has any immediate relevance as we go forward with decision making at this site," spokesman Mick Hans said.
The university study measured dioxin levels in the blood of nearly 700 residents of Saginaw and Midland counties and about 250 people in Jackson and Calhoun counties selected for comparison purposes.
Results released in 2006 and updated since found some Saginaw-Midland participants had elevated dioxin levels. But those levels were related less to where the people lived than other factors, such as their ages, the study found.
A review by EPA's National Center for Environmental Assessment said several factors would limit the study's usefulness for evaluating human exposure to dioxin in the area.
None of the study subjects were children, who tend to have greater exposure to contaminants because they have more contact with soil and dust, the review said.
Also, it was unclear whether the study included enough residents living on properties with highly polluted soils, EPA said. Also uncertain was how many of the subjects participated in activities that boost exposure, such as eating local fish and game with elevated dioxin levels.
"The lack of emphasis on sampling of subpopulations likely to be most affected ... is a significant drawback," the review said.
David Garabrant, who led the University of Michigan study, said 23 test participants lived on properties where soil dioxin levels exceeded 1,000 parts per trillion — the level that can trigger EPA cleanups. Hundreds of others lived where levels were between 500 and 1,000 parts per trillion.
"That's not trivial by any means," he said. Yet the study concluded that soil is "a small contributor at most" to dioxin in blood.
Garabrant said the study, started in 2003, was meant to address a lack of information about the extent of the pollution and what it might mean to area residents.
"The issue is not whether to clean up, but to what level do you clean up?" he said. "Our study is intended to provide data that would allow people to make good decisions."
EPA reviewers found the study "valid and well done," Garabrant said. "To say this study can't be useful is to say there is no amount of data that can answer the questions and I don't believe that as a scientist. There's no other study close to it in terms of its size, the rigor with which it's done, the amount of scrutiny it's gotten."
Some of the EPA's criticisms echoed those in an outside review for the Michigan Department of Environmental Quality earlier this year.
DEQ also believes the study won't be much help with the cleanup, spokesman Robert McCann said. But a bigger concern is that some people in the affected community believe it found the dioxin contamination poses no health risk, he added.
"It's being characterized as drawing conclusions that it was never intended to draw," McCann said.
Dow spokeswoman Mary Draves said the company was studying the EPA review.