New research finds another chemical compound bioaccumulates and may be more persistent than DDT and PCBs

New research has found that PFOS, used to treat carpets, leather, paper and fabrics, is present in the tissues of many species of animals around the globe, and may present more of a problem than other well-known bioaccumulating compounds.


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Using a highly sensitive new technique, researchers at Michigan State University have detected traces of a commercially produced polymer, perfluorooctane sulphonate (PFOS), in a surprisingly wide variety of wildlife – from Arctic seals to Ganges river dolphins and Mississippi turtles. John Geisy and Kurunthachalam Kannan of the National Food Safety and Toxicology Center at Michigan State University collected samples of blood or tissue from mammals, birds, fish and reptiles from various parts of the world and tested them for fluorinated organic compounds (FOCs), the class of compounds to which PFOS belongs. They found that some species contained varying levels of other FOCs but all contained PFOS, with the highest levels found in animals found close to urban areas.

What surprised the researchers was that PFOS, like other FOCs, consisting mainly of carbon and fluorine atoms, was found in animals from pristine environments. Because it is a large molecule and its atoms are tightly bound together, the chemical is exceedingly stable, therefore researchers did not expect it to spread in the environment or become concentrated in the food chain. “It got into the bald eagle’s blood, polar bears, fish, birds, everywhere. That surprised me,” said Geisy.

There have long been suspicions about FOCs. But there had previously been no way of studying them at the low concentrations found in blood and tissues. “This is a class of chemicals that had not received a lot of attention,” says Scott Mabury, a chemist at the University of Toronto, who is trying to develop models to compare the behaviour of FOCs in the environment with that of the well-studied POCs.

The suggestion that PFOS can bioaccumulate and has spread worldwide has “blind-sided most people”, says environmental chemist Tom Cahill of Trent University in Ontario, Canada. The new results have led environmental chemists to wonder if , because FOCs are so persistent, they may represent even more of a problem than the polychlorinated organic compounds (POCs), which include PCBs (polychlorinated biphenyls) and DDT (dichlorodiphenyltrichloroethane).

“There’s no known degradative pathway for these compounds,” Mabury points out. The journal, Nature says that there is much work still to be done on FOCs and it is not known how a chemical as inert and non-volatile as PFOS is spreading around the globe. Mabury conjectures that volatile or more water-soluble chemical precursors to PFOS may be travelling around the globe and forming PFOS in situ.

It is also unclear whether FOCs are toxic. At 1,000-fold higher concentrations than those found in Giesy’s study, PFOS poisons laboratory rats. But the effects of low concentrations of the compound on wildlife are not known. “As more species-specific information becomes available, a refined assessment of the risks to wildlife will be possible,” says Geisy.

Other FOCs that are still being manufactured, or their breakdown products, may be of as much concern as PFOS, Geisy warns. “There are over 100,000 synthetic fluorinated compounds, many of them perfluorinated [like PFOS], that people haven’t really looked at,” says Geisy. One group in particular, the perfluorinated carboxylates, are widely used to manufacture materials such as fire-fighting foams and Teflon. “They’re generally at lower concentrations, but we find them in remote areas as well,” says Geisy.

Industry representatives from many countries, including the United States, United Kingdom and Canada, met in January to discuss the problem of PFOS after the 3M Corporation of St Paul, Minnesota, which funded the study and was the leading world producer of the chemical, voluntarily stopped making it last year. And this month the US Environmental Protection Agency published new rules restricting the manufacture of PFOS.

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