PFOS and PFOA levels in blood declining

US researchers have reported the first evidence that levels of perfluooctanyl sulphonate (PFOS) and perfluorooctanoic acid (PFOA) in human blood are declining.1 Concentrations of both substances halved between 2000 and 2005.

A survey of 40 US Red Cross blood donors in 2005 reported an average PFOS concentration of 20.2 nanograms per millilitre and 3.5ng/ml of PFOA. A similar survey of 100 blood donors in 2000 had reported levels of 43.3 and 5.7ng/ml respectively.

3M, the main manufacturer of PFOS, phased out production between 2000 and 2002 following concerns about its toxicity, persistence and ability to bioaccumulate (ENDS Report 354, pp 28-31 ).

Manufacturers are now under pressure from the US Environment Protection Agency to phase out PFOA emissions (ENDS Report 373, pp 16-17 ). DuPont has already agreed to stop producing the compound (ENDS Report 386, pp 9-10 ).

The findings are consistent with the rate of breakdown in the human body of PFOS and PFOA, the half-lives of which are five and four years respectively.

The study was a pilot, based on donors living around Minneapolis-St Paul, where 3M’s PFOS production was based. Further work is needed to unpick the links between PFOS and PFOA levels and expand the study geographically, the authors say.