A find of dioxin at the bottom of the Saginaw River could be the highest level of such contamination ever discovered in the nation's rivers and lakes, according to a federal scientist involved in cleanup efforts downstream from a Dow Chemical Co. plant.
A crew testing the Saginaw and Tittabawassee rivers discovered the sample, which measured 1.6 million parts of dioxin per trillion of water, The Saginaw News and The Detroit News reported last week. That level is about 20 times higher than any other find recorded in the EPA archives.
"There may be more surprises out there," said Milton Clark, a health and science expert for the U.S. Environmental Protection Agency. "I'd be surprised if there's not more surprises out there."
State guidelines require corrective action on contamination above 1,000 parts per trillion.
Dioxins are toxic byproducts of the manufacture of chlorine-based products, and some have been linked to cancer and other health problems.
Michigan health officials were worried enough about last week's announcement that they extended a fish consumption advisory already in effect for the Tittabawassee River — a Saginaw River tributary that winds through Dow's plant in Midland — to include the entire Saginaw River and a portion of Lake Huron's Saginaw Bay, where both rivers' water ends up.
Dow is removing three dioxin concentrations along a six-mile stretch of the Tittabawassee. The company plans to remove the latest find, Dow spokesman John C. Musser said.
"We don't believe there's any imminent or significant human health or environmental threat," Musser said.
The Michigan Department of Community Health advisory warns against eating carp, catfish and white bass — fish that feed near the riverbed where contaminants are buried. It also alerts women of childbearing age and children against eating certain types of other fish.