Blood work

For years, environmentalists tried to persuade the EPA to ban a suspected carcinogen found in the bloodstreams of nearly every creature on the planet. Then Scott Mabury made a groundbreaking discovery

By Sharon Oosthoek

As the light fades on this late winter afternoon, Scott Mabury stands at the whiteboard in his University of Toronto office drawing complicated-looking chemical formulas. A large man with a full beard and plaid shirt, he looks like he would be more comfortable paddling a canoe on a quiet northern Ontario lake.

But Mabury is best known in scientific circles as the environmental chemist who solved the mystery of how a newly recognized and potentially toxic substance is finding its way into nearly everyone’s bloodstream. Mabury, who holds a PhD in environmental chemistry, loves a mystery and has been trying to solve this particular one for the past seven years, ever since scientists first began systematically measuring for — and discovering — perfluorooctanoic acid (PFOA) in human and animal blood.

In 1976, a University of Rochester researcher unexpectedly discovered an organic fluorine in his blood while researching water fluoridation. But he could not identify the chemical beyond that. It wasn’t until the late 1990s that scientists were able to identify the fluorine-based chemicals in our bloodstreams.

When PFOA was discovered, researchers were baffled by its widespread presence. Even more unexpected was its appearance in the blood of Arctic animals, including Canadian polar bears, living far from the manufacturing plants that produce PFOA. Mabury and his team of researchers — the Mabury Group — have discovered that common consumer products such as microwave popcorn bags and stain-resistant carpets are the most likely source of the PFOA circulating through our bodies. More specifically, these products are treated with stain- and water-resistant chemicals that, over time, break down and release fluorinated alcohols, which in turn degrade into PFOA.

Although PFOA cannot travel long distances, its precursor, fluorinated alcohol, can. The latter can remain in the atmosphere for up to 20 days, enough time to travel as far away as the Arctic before breaking down into PFOA. “Our major contribution is understanding the transport and degradation process,” says Mabury, who has been studying fluorinated chemicals since 1998.

PFOA, sometimes called “C8” because of its eight carbon atoms, is a manufactured chemical that does not occur naturally in the environment. It is a member of a class of chemicals known as fluorinated chemicals that not only bio-accumulate in our bodies, but also retain their molecular arrangement for a very, very long time.

“These chemicals redefine persistence as we know it,” says Mabury. “Chemicals known as ‘persistent toxic chemicals’ do degrade eventually. But these chemicals have never been shown to degrade under any environmentally relevant conditions.” In the United States, science advisers to the Environmental Protection Agency (EPA) recommended in February that the agency classify PFOA as a “likely” human carcinogen. While the agency prepares a final risk assessment for PFOA, its scientists examine studies that indicate the chemical causes liver tumours in rats and immune problems in mice.

Especially alarming is the possibility that the way we are exposed to PFOA may put children at particular risk.

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