Perfluoropolymer degrades in decades, study estimates
EPA
tion.” The DuPont scientists Ideally, chemists strive to moniThe breakdown of fluorotelomer declined to comment for this tor biodegradation of a particular polymers, the main fluorinated instory. chemical by measuring both degredient in stain repellants and paBut the custom polymer, with a creases in its weight and increases per coatings, is a significant source grain size similar to table salt, is in the breakdown products, says of perfluorooctanoic acid (PFOA) more than 100 times bigger than environmental chemist Linda Lee and other fluorinated compounds fluorotelomer polymers in comof Purdue University. But the in the environment, U.S. Environmercial use. Washington atpolymer is too big to analyze, so mental Protection Agency (EPA) tempted to account for scientists conclude in a this with a model that study recently published allows for the much in ES&T (2009, DOI greater surface area, and 10.1021/es9002668). The consequently greater finding could impact the degradation rate, of future of these and smaller particles. The myriad other products conversion drops his exthat rely on fluorotelomer perimentally determined polymers, because the polymer half-life from agency is moving to roughly 1000 years to tighten its rules on the EPA scientists tried different solvents to dissolve the acrylatelinked fluorotelomer polymer used in the experiments. about 10-17 years. While basis of this study and Lee agrees that small other research. particles may degrade more rapchemists are left trying to track PFOA occurs at low levels in idly than large ones, she cautions the breakdown products, which the environment and in human that Washington’s conversion is include fluorotelomer alcohols blood. It remains in people’s bodtoo simplistic. and PFOA. ies for years and causes developOther scientists say the EPA But even at the very start of mental problems and other study makes a significant contrithe experiment, the polymer adverse effects in laboratory anibution. “This is an important contains fluorotelomer alcohols mals. Last year, high levels of perquestion, and the EPA study adas residuals from the manufacfluorinated chemicals found in vances the science by finding a turing process. These residuals Decatur, Ala., prompted EPA to better way to deal with the probcomplicate the experiment beissue a short-term drinking-water lem of residuals,” says chemist cause they act as background advisory for PFOA, and New JerScott Mabury at the University of noise that can swamp the signal sey has issued guidance for Toronto. of degradation. A two-year-long chronic drinking-water exposure “We believe that at this point in study by DuPont scientists conof 0.04 parts per billion. time this is the best data available cluded that degradation was a Other chemicals break down to to the agency,” says Cathy Fehvery slow process, but the report form PFOA, but few attempts renbacher, chief of EPA’s expowas criticized by some academic have been made to determine sure assessment branch. “The and industrial chemists for startwhether fluorotelomer polymers relatively short half-life is consising with too high a fluorotelobiodegrade. These polymers reptent with other unpublished studmer alcohol residual signature. resent a potentially large source ies that have been submitted to EPA research scientist John of PFOA and other perfluorocarthe agency.” Washington used an acrylateboxylates, because they constitute In 2006, EPA proposed that it linked fluorotelomer polymer cusabout 80% of total fluorotelomer should review new perfluorinated tom made to minimize residuals. production. polymers before they are made, He also completely dissolved duBut experimentally determining because they could break down to plicate samples of the polymer at whether perfluorotelomer polyproduce PFOA and other perfluothe start of the experiment and mers degrade is fraught with diffirochemicals. The rule has lanthen at 497 days and 546 days to culties. The EPA study has its guished for over three years, but make sure he analyzed all the share of problems, including few EPA now expects to finalize the chemicals. “A key feature of our data, insufficient controls, and a rule this year, according to work is the extraction,” he says. leap from the laboratory results to spokesperson Dale Kemery. “The DuPont study was very broad conclusions, according to good, but they did not undersome scientists who study these —REBECCA RENNER stand the need for total extracchemicals. 10.1021/es9021238
2009 American Chemical Society
Published on Web 07/21/2009
September 1, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 6445
