Discovery News | May 15, 2009
By Emily Sohn

May 15, 2009 -- To the growing list of chemicals showing up in human blood, a new study adds compounds that make food wrappers grease-proof.

Called diPAPs, these chemicals are fairly new and scientists don't yet know if they are harmful to human health. But diPAPs break down into another worrisome chemical, called PFOA, which may be carcinogenic.

"The take-home message is that some chemicals that make our lives easier, better and more satisfying end up in our bloodstream with unknown toxicological consequences," said Scott Mabury, a chemist at the University of Toronto. "We should be smart enough to design chemicals that do what we want them to do without causing a chemical pollution problem."

The new study builds on accumulating and worrisome research into a class of compounds called perfluorochemicals. PFOA (perfuorooctanoic acid) is a major one. PFOS (perfluorooctane sulfonate) is another.

PFOA and PFOS are resistant to oil and water, which makes them perfect for use as liners on carpets, nonstick pans, microwave popcorn bags, clothes, electronics and pizza boxes, among many other applications. The problem is that these compounds end up in the environment, our food and our bodies.

Scientists have found perfluorochemicals in every human blood sample they've tested, Mabury said, often at relatively high levels. In animal experiments, PFOA and PFOS have been linked to cancer, developmental problems and other issues.

Polar bears in the Arctic harbor particularly high levels of PFOA, which confused scientists at first but then led them to discover a large number of precursor chemicals that can escape their sources, fly through the air and end up in animals in remote locations, where the chemicals break down into PFOA.

Mabury was interested in learning more about an overlooked precursor: diPAPs (polfluoroalkyl phosphoric acid diesters), which are used to make food wrappers resistant to grease. These chemicals were designed to stick to the paper, but Mabury suspected that they were getting out of the wrappers and into the food. Because diPAPs break down quickly, he thought that evidence of human contamination would be difficult to find.

The researchers used a highly sensitive, $500,000 mass spectrometer to analyze 20 samples that combined the blood of 10 people. To their surprise, their results, showed levels of diPAPs that were just as high as levels of PFOA in human blood.

It's the first time anyone has found these chemicals in our bodies. And the findings, published in the journal Environmental Science & Technology, suggest that diPAPs are contributing a significant portion of the PFOA found in human blood, Mabury said -- maybe 10 percent or more.

What's more, Mabury said, the intermediate steps in that breakdown process produce molecules that have been shown in experiments to be 10,000 times more toxic than PFOA itself.

"In going from diPAPs to PFOA, you go through things that have been entirely ignored by essentially all of the academic research community," Mabury said. "This is not something you want to be a common contaminant in humans. Certainly not at the concentrations its at."

The team also found high levels of diPAPs in sewage sludge and paper pulp, suggesting that these chemicals might be getting into the water supply and onto farm fields, as well.

Already, the Environmental Protection Agency has convinced 3M, the only U.S. manufacturer of PFOS to stop using that chemical. The EPA has also been encouraging companies to reduce emissions and find alternatives for PFOA and many of its precursor molecules as they further investigate the chemical. The new work suggests that diPAPs themselves need more attention.

"We were told before that PFOS and PFOA don't do anything," said John Giesy, an environmental chemist and toxicologist at the University of Saskatchewan in Saskatoon. "Well, in fact, they do. They're quite potent toxicants through a couple mechanisms of action. The question for me and people like me now is: What do these chemicals do?"

So far, no one has studied the health effects to humans of exposure to food-wrapper chemicals or their breakdown products. But, Giesy said, it's worth looking into right away.

"I don't know if it's time to panic, and I doubt it is," he said. "But we really don't know what it's doing. It's something we need to worry about. It's something we need to find out about."