A US study adds to evidence that higher blood levels of perfluorinated chemicals (PFCs) may be linked to an earlier menopause.

A team led by Kyla Taylor, from the US National Toxicology Program, investigated the association between a range of PFCs and the age at which menopause starts for 2,732 women in the National Health and Nutrition Examination Survey (Nhanes).

They detected PFOS, PFOA, perfluorohexane sulfonate (PFHxS) and perfluorononanoate (PFNA) in at least 95% of the blood samples, and found positive associations between the chemicals and earlier menopause, as suggested by earlier studies (CW 23 March 2011).

Other menopause studies have not included PFNA and PFHxS. This is “of concern”, say Dr Taylor and her colleagues, because levels of PFNA and PFHxS have not declined over time in the same way as PFOA and PFOS. They point to surveys suggesting that mean blood levels of PFNA and PFHxS are in fact increasing in humans.

The underlying mechanism of the association is unknown, say the researchers. Because of the cross-sectional nature of the Nhanes data, they cannot be certain whether the association between PFCs and menopause is causal. PFCs may be excreted in blood during menstruation and so post-menopausal women may have higher levels of the chemicals because they lose an “elimination pathway”, they suggest. Regardless of the underlying cause, women appear to accumulate PFCs more rapidly after they are no longer menstruating, they add.

Dr Taylor and colleagues say that their results support the need for continued monitoring of blood PFC levels in the general population, as well as further studies of the reproductive health effects of PFCs.

The study is published in Environmental Health Perspectives.