Researchers say findings explain global distribution of perfluorooctane sulfonate

Canadian researchers believe they have found evidence that explains the global ubiquity of perfluorooctane sulfonate (PFOS) in humans and animals (Environ. Sci. Technol. 2001, 35 (7), 154A–160A), which until now has been a mystery, because PFOS is sparingly volatile and moderately water-soluble, making it a poor candidate for long-range atmospheric transport.

In a forthcoming issue of Analytical Chemistry, Jonathan Martin and co-workers report that they’ve found volatile PFOS precursors in an initial reconnaissance of southern Ontario air at picogram–per-cubic-meter (pg/m³) concentrations. The researchers hypothesize that transport of these compounds accounts for PFOS’s global ubiquity.

“Our results suggest a plausible mechanism for the widespread dissemination of PFOS via a volatile precursor transporter. We predict these alcohols are rapidly degraded via hydroxyl reactions in air, and we are currently experimenting to determine [reaction] rates and products [which include PFOS]. Our interest is, in part, driven by the extreme persistence and potential bioavailability of any perfluorinated degradation products,” explains University of Toronto chemist Scott Mabury, the research team leader.

“This team has used powerful analytical tools to provide a superb insight into a difficult problem,” comments atmospheric chemist Steven Eisenreich, at the European Commission Joint Research Center in Ispra, Italy. “The detailed analytical chemistry of the precursors using GC-MS-NCI and GC-MS-PCI is excellent. In addition, the authors showed great insight in the production chemistry of these compounds that PFOS precursors could indeed be formed in transport or biologically in the organism.”

DuPont, one of five companies that manufactures perfluorinated compounds (Environ. Sci. Technol. 2001, 35 (7), 154A–160A), has issued a statement skeptical of the findings. Another of the companies, 3M, has pulled out of manufacturing compounds that could degrade to PFOS and is not investigating their fate and transport, according to a company spokesperson.

Dupont’s criticism concerns the validity of the measurement procedures used, the small number of samples analyzed, and the lack of collaboration with other labs. Given these shortcomings, it would be inappropriate to speculate on potential PFOS sources at this time, the company said.

Martin, however, is not so skeptical, noting that, “The analytical methods are pretty straightforward.” To perform the analysis, he and fellow researchers used high-volume air samplers to collect gaseous and particle-bound fluoroorganics on composite media, gas chromatography to separate a suite of potential PFOS precursors sulfonamides and fluorotelomer alcohols, and chemical ionization-mass spectrometry to detect the chemicals. Low concentrations of fluorooganics (<4 pg/m³) were consistently detected in blanks, but this did not prevent confirmation or quantitation of environmental concentrations, they say.

What’s important now, Martin says, is to perform a source assessment. “Are these precursors released when commercial products such as carpets, paper, and textiles are treated for stain resistance, or does release occur in the home? The answer to this question has ramifications for estimating future environmental burdens of fluorinated organics.” Currently, the scientists are analyzing the results of a more extensive sampling campaign. “It’s our [top] priority to monitor for several years. It would help if other labs were involved,” Martin says. —REBECCA RENNER