Science News - December 22, 2004

Another route to PFOA

Microbial degradation can produce small amounts of perfluorooctanoic acid (PFOA) from fluorotelomer alcohols, according to research [for Web: recently posted to ES&T’s Research ASAP website (es049466y). The laboratory results are in accord with new data from sewage treatment plants and create a fuller picture of how these substances may be moving throughout the environment.

Fluorotelomer alcohols are volatile chemicals used to make fluorinated stain repellents that are widely applied to fabrics, carpets, and paper. They are also used in the manufacture of products such as paints, adhesives, waxes, polishes, metals, electronics, and caulks. During 2000–2002, an estimated 5 million kilograms of the telomer alcohols were produced annually worldwide, with 40% of that production in North America.

University of Toronto chemist Scott Mabury and colleagues have theorized that these alcohols undergo atmospheric transport and degradation to form perfluorinated carboxylates, or perfluorocarboxylates, including PFOA, whose presence in remote areas is of intense interest (Environ. Sci. Technol. 2004, 38, 11A–12A). The U.S. EPA is currently completing a human health risk assessment of PFOA because of concerns about possible developmental effects.

The new study’s lead author, Ning Wang, is a biologist at DuPont, which uses telomer alcohols to produce stain repellent. Wang and his colleagues conducted aerobic biodegradation studies of telomer alcohol labeled with carbon-14 in diluted activated sludge from a wastewater treatment plan. They tracked the metabolites using a radioisotope counting technique and then identified the degradation products via mass spectrometry. In addition to PFOA, they identified a number of polyfluorinated telomer acids.

Wang’s results and a paper by Mary-Joyce Dinglasan and colleagues at the University of Toronto (Environ. Sci. Technol. 2004, 38, 2857–2864) present a consistent picture, according to Mabury, an author of the Dinglasan paper. “The Wang study confirms our findings and fleshes out the picture by identifying a new degradation product,” says Mabury. In follow-up experiments, he says, his lab has started with the dominant byproduct, the telomer acid, and followed its eventual degradation to perfluorocarboxylates.

The degradation studies complement data from a survey of 10 U.S. urban sewage treatment plants conducted by Oregon State University chemist Jennifer Field and her student Melissa Schultz. The levels of carboxylates in sewage-plant effluents were higher than influent levels in 8 out of 10 plants; this suggests that microbes in the plant are degrading telomer alcohols, Schultz said at the Society of Environmental Toxicology and Chemistry’s annual meeting in Portland, Ore., last month. —REBECCA RENNER