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January 24, 2004

Science News

Perfluorinated sources: factories outside, consumer products inside?

By Rebecca Renner

The levels of some volatile compounds that break down to perfluorooctane sulfonate (PFOS) inside North American homes are about 100 times higher than those of outdoor levels, according to the first indoor measurements of three perfluorinated sulfonamides, which are published in research recently posted to ES&T’s Research ASAP website (10.1021/es0305555). Another recent article presents some of the first outdoor atmospheric measurements of these PFOS precursors, called perfluorinated sulfonamides, and measurements for telomer alcohols, a second class of volatile chemicals that could be precursors to perfluorooctanoic acid (PFOA). These studies offer important clues to the mystery of how the nonvolatile PFOS and PFOA compounds have become ubiquitous in the environment and in people.

Perfluorinated sulfonamides and telomer alcohols are used to protect the surfaces of fabric, leather, upholstery, carpet, and paper. In 2000, PFOS emerged as a priority pollutant because of its widespread detection in wildlife, its persistence and ability to bioaccumulate, and concerns about its adverse health effects.

The U.S. EPA is investigating PFOA because of its long residence time in humans and the possibility that it may pose developmental risks to children at current concentrations in mothers’ blood (Environ. Sci. Technol. 2003, 37, 201A). In December 2003, an EPA work group accepted an offer from five telomer manufacturers to develop a monitoring scheme in the heart of Georgia’s carpet manufacturing region to determine whether carpet manufacturers and treaters are emitting PFOA or its precursors. Details of the monitoring plan remain to be determined, according to an EPA spokesperson.

The measurements of the perfluorinated sulfonamides in indoor air were made by Environment Canada chemist Mahiba Shoeib and colleagues in Canada and the United States, who analyzed air inside four houses and two laboratories. N-methyl perfluorooctane sulfonamidoethanol (MeFOSE), a volatile PFOS precursor that is widely used as a stain repellent on carpets, was the most abundant of the three chemicals that they measured in indoor and outdoor air. Next most abundant was N-ethyl perfluorooctane sulfonamidoethanol (EtFOSE), a precursor that is used to treat paper. A third chemical was below detection in most samples. The mean indoor concentrations of MeFOSE and EtFOSE were 2589 and 772 picograms per cubic meter, respectively, about 100 times higher than those of outdoor values.

Meanwhile, University of Toronto chemist Naomi Stock and Canadian colleagues present strong evidence for point sources of polyfluorinated telomer alcohol and sulfonamide contamination in their survey of the air around six North American cities in research recently posted to ES&T’s Research ASAP website (10.1021/es034644t). The evidence for point source emissions includes substantial differences in both total measured concentrations in various cities and the chemicals that dominated the sampling profile, says Stock.

The air samples that Stock and her colleagues analyzed were collected in November 2001— before the 3M phaseout of PFOS chemicals—from six U.S. and Canadian cities. Both sulfonamides and telomer alcohols were found at all sampling locations, with Griffin, Ga., having the highest levels. Because Griffin is located near the center of carpet manufacturing and the air samples were dominated by MeFOSE, Stock and her colleagues believe that factories associates with the carpet industry are the source.

Many treatment products consist of fluorocarbons linked to a group that can polymerize and thus bind to the carpet. In the past, it has been assumed that this linkage would effectively sequester the fluorocarbons from the environment. However, a small percentage of the fluorinated treatment product lacks the polymerizing linkage. As a result, free chemicals may be left in the carpet fibers after treatment. Stock hypothesizes that these volatiles could be an important source of PFOS and PFOA in the environment. In addition, breakdown processes in homes may even release the chemically bound precursors.
Read this story at: http://www.EWG.ORG/news/story.php?id=2214