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In 1973, a plant owned by Velsicol Chemical made a mistake and shipped a toxic flame retardant chemical to a livestock feed plant. The chemical is called polybrominated biphenyl, or PBB. It took about a year to discover the accident. Millions of Michiganders ate contaminated beef, chicken, pork, milk and eggs.

All these years later, researchers are finding that PBB exposure is linked to health problems.

Michele Marcus is a professor of epidemiology, environmental health and pediatrics at Emory University Rollins School of Public Health and Emory University School of Medicine.

She's in Michigan this week to talk about her latest research findings at a conference at Alma College.

PBB sticks around in your body

Marcus says over the past two years, her team has tested more than 800 people across the state.

"We have found that six out of 10 of the people that we tested still have levels that are elevated as a result of the PBB accident," she says. "We compared the levels of PBB in the people that we tested in Michigan to levels that were measured ten years ago on a random sample of the U.S. population."

She says six out of 10 Michiganders had PBB levels higher than 95% of the U.S. population.

"We are concerned that the health effects we have found are continuing among the people who were exposed themselves, but also among their children and grandchildren."

"It means that the PBB is still lingering in people’s bodies and that’s a very long time. It’s 40 years later. And we are concerned that the health effects we have found are continuing among the people who were exposed themselves, but also among their children and grandchildren," she says.

Health effects over multiple generations

She says her team has found that among the women who were exposed to high levels of PBB, there are slightly more breast cancer cases than they expected.

"Among girls, the daughters of women who were highly exposed, we found that they experienced their first menstrual periods a full year earlier than girls who were unexposed, and now that these girls are adults, we find that they have a very high rate of miscarriages. And that the rate of miscarriages is proportional to the PBB exposure that they experienced," says Marcus.

Marcus says at the conference, she's presenting preliminary data on the potential for epigenetic changes that are associated with PBB exposure. Those are changes in how genes are expressed.

"That really sets the stage for our just-funded research," she says. "We will be recruiting multi-generational families where the father was exposed but not the mother, and looking at the children and the grandchildren so we can see if these epigenetic changes are passed along in the absence of actual PBB exposure."

She says her new research project has three goals. One is to determine whether epigenetic marks are being transmitted across generations.

They're also going to test a substance that may be able to help speed elimination of PBB from the body.

"When the results are in, we will let people know if we’ve been able to successfully help people eliminate PBB from their bodies. Because PBB is very slowly eliminated. It takes about 15 years for you to eliminate about half of the PBB in your body. So we are going to try an intervention that we think may help speed the elimination," she says.

She says the third goal is to educate the public and doctors so they understand that people who have been exposed to PBB in Michigan may have a higher risk of breast cancer, pregnancy problems and thyroid problems, so they can be monitored.

You can learn more about Emory's PBB registry for people who were exposed to the chemical here, and you can learn more in our special series on the PBB mix-up and legacy of pollution in St. Louis, Michigan here.