Chemists unravel reactions pathway for carpet chemicals.

Chemists unravel reactions pathway for carpet chemicals.

Polar bears don’t generally benefit much from carpets, but they could be suffering health problems as a result of them. An international team of chemists has discovered that chemicals used to prevent stains on carpets and other textiles may be undergoing atmospheric reactions in remote areas as distant as the Arctic, where they then generate toxic compounds.

Perfluorinated carboxylic acids (PFCAs) are persistent and potentially carcinogenic chemical compounds which have been detected in the blood and tissue of humans and animals around the world, including polar bears in the Arctic. Despite their ubiquity, environmental scientists have been at a loss to explain where the compounds come from, as there are no known large-scale natural or industrial sources.

The best guess is that PFCAs are generated in the atmosphere from a precursor chemical. One possible candidate is fluorotelomer alcohols (FTOHs), which are used to prevent carpets from staining, but the reaction pathway by which they might be transformed into PFCAs was unknown. Now, chemists from the University of Toronto, Canada; the Ford Motor Company, Michigan, US; and the University of Copenhagen, Denmark, have confirmed that PFCAs can be produced from FTOHs. The team carried out its experiments in a smog chamber, where it used chlorine atoms to initiate the oxidation of three different FTOH compounds. OH radicals would initiate this oxidation in the atmosphere, but chlorine atoms are easier to generate and react with FTOH compounds in the same manner. The team collected regular samples from the smog chamber, and analysed them using gas and liquid chromatography, and mass spectrometry.

The chemists detected various PFCA compounds in the samples, including trifluoroacetic acid and perfluorooctanoic acid. They then worked out the simplest production mechanism, which involves successive peroxy radical cross reactions. These reactions probably happen more efficiently in remote areas, where relative concentrations of HO 2 and other peroxy radicals tend to be higher. This helps to explain why PFCAs seem to be accumulating in the Arctic.

’It does appear to be an issue that’s going to affect Arctic food webs and Arctic people who depend on them’, said Jonathan Martin, one of the researchers at the University of Toronto.

Jon Evans