Chemistry

Fate of Fluoropolymers

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Science  24 Jul 2009:
Vol. 325, Issue 5939, pp. 369
DOI: 10.1126/science.325_369c

The synthetic materials we rely on in everyday life are typically required to pass a series of laboratory tests before they can be used in consumer products. Outside the controlled environment of the lab, however, some approved compounds may degrade into potentially harmful byproducts. Washington et al. explored the capacity of a fluorotelomer polymer, similar to those commonly used in stain-resistant clothing and firefighting foam, to degrade into potentially toxic perfluorooctanoic acid when added to soil columns. In general, such studies face substantial challenges in unraveling the complex chemical and microbial pathways at play in real soil (often first-generation byproducts must be inferred from observation of their own induced by-products). Moreover, analysis of this specific type of degradation is hampered by the tendency of the byproduct to cling to the parent polymer and so elude sampling. The authors therefore developed a multistep extraction protocol involving the successive use of several different solvents. Their experiments yielded a degradation half-life on the order of 1000 years, consistent with prior studies; however, modeling of the data suggested great sensitivity of the kinetics to exposed surface area, potentially raising the degradation rate by two orders of magnitude for commercial polymers more finely grained than the authors' test samples. The exact degradation pathway remains unknown but could involve local microorganisms.

Environ. Sci. Technol. 43, 10.1021/es9002668 (2009).

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