Analysis of sediment samples collected from Lake Ontario in North America shows an increase in “unidentified” organic fluorine compounds in recent years. The results suggest that the “use and manufacture of fluorinated organic compounds other than known PFCAs [perfluorocarboxylates] and PFSAs [perfluoroalkane sulfonates] has diversified and increased,” writes a team from Canada, China, and Japan.

Leo Yeung from the City University of Hong Kong worked with researchers from Japan’s National Institute of Advanced Industrial Science and Technology, Environment Canada, and the University of Toronto, to analyse Lake Ontario surface sediments and sediment core samples for 14 perfluoroalkyl substances.

They identified the usual suspects, PFOS and  PFOA, in all surface sediment samples. However, known PFCAs and PFSAs only accounted for up to 44% of a key fraction of extractable organic fluorine in surface sediment, suggesting that “a large proportion of fluorine in this fraction remained unknown,” write the researchers.

Future work should not only aim to characterise, or identify, the unidentified fluorine, but also to understand whether it could degrade to persistent PFSAs or PFCAs, they add.

The study is published in Environment International, 59:389–397. September, by Yeung LWY et al. See abstract.

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