DDT Is Still Killing Birds in Michigan

In Michigan, the town of St. Louis neighbors three Superfund sites that were once occupied by plants that produced the pesticide DDT. And so while, in most towns, a few dead birds might not be cause for alarm, in St. Louis, residents worried. And, Environmental Health News reports, when scientists collected the bodies of 22 American robins, six European starlings and one bluebirds, they found incredibly high levels of the pesticide that created Rachel Carson's "Silent Spring."

“I’ve never seen anything like it," Matt Zwiernik, a Michigan State University assistant professor of environmental toxicology who led the testing, told the news site. "When people told me about it I didn’t believe it. And then we ran these tests. These are some of the highest-ever recorded levels in wild birds.”

DDT has been banned in the United States for more than 40 years, and hadn't been produced at that plant in more than half a century. But, as EHN reported:

The birds' brains contained concentrations of DDE, a breakdown product of DDT, from 155 to 1,043 parts per million, with an average of 552. “Thirty in the brain is the threshold for acute death,” Zwiernik said. “All the birds exceeded that by at least two- or three-fold, and many by much more than that.” Twelve of the 29 birds had brain lesions or liver abnormalities.

The culprit is a toxic mess left behind by Velsicol Chemical Corp., formerly Michigan Chemical, which manufactured pesticides until 1963, a year after Rachel Carson’s book Silent Spring exposed the hazards of DDT, especially for birds. Populations of bald eagles and other birds crashed when DDT thinned their eggs, killing their embryos. The pesticide, known for accumulating in food webs and persisting for decades in soil and river sediment, was banned in the United States in 1972.

Why the sudden spike in bird deaths? In reality, it may not be a spike at all; birds have been steadily dying, but it took a while for scientists to collect enough samples for a meaningful study.

Researchers speculate the birds were poisoned by eating contaminated earthworms on one of the Superfund sites. Much of the money allocated toward cleaning up the sites went toward removing DDT-laden sediment in the nearby Pine River, for which the EPA issued a no-consumption advisory. The level of the pesticide in fish downstream of sites has declined, but clearly the contamination hasn't been fully cleaned up.