It’s not often that one team of scientists hits the headlines for two separate studies in a week. But that’s what the groups led by David Melzer, of Exeter’s Peninsula Medical School, and Tamara Galloway, of the University of Exeter, have achieved – thanks to their research finding correlations between ill-regarded chemicals and human disease.

Last week, it was bisphenol A linked (for the second time) to heart disease. Today, it’s the turn of perfluorinated chemicals (PFCs); in a paper published in Environmental Health Perspectives (doi:10.1289/ehp.0901584), higher concentrations of perfluorooctanoate (PFOA) in the blood are correlated with higher incidence of thyroid disease in US adults; while perfluorooctane sulfonate (PFOS) is linked to thyroid disease in US men only.

PFCs were thought to be innocuous when introduced in the 1950s. Their stain-repellent and heat-resistant properties have seen them used in fire-fighting foams, food wrappings, pesticides, carpets, upholstery, industrial surfactants, and to make non-stick coatings. Tthe chemicals have already fallen under suspicion from animal studies, which have sussed them as toxic, potentially carcinogenic, and slow to break down in the environment. Animal studies have also shown links to thyroid hormone imbalances before. Last year, a similar sort of statistical analysis on a set of Danish women linked PFCs to fertility problems.

Correlation does not cause causation, the researchers point out; it may be that having thyroid disease changes the way one’s body deals with PFCs, for example. Other studies of people with higher exposures of PFOA – and potentially more reliable assessments of thyroid function – haven’t found clear associations, though the largest of such studies is underway at the University of West Virginia (preliminary data in pdf). When all’s said and done, more work is needed to show a clear, mechanistic link.

PFCs are already being slowly phased out of production. In May 2009, the Stockholm Convention on Persistent Organic Pollutants decided to restrict (though not ban) PFOS, adding to its list of persistent organic pollutants. The US Environmental Protection Agency has got key PFOA-using companies, including DuPont, to agree to cut use of the chemical down by 95% by 2010, and to eliminate it by 2015.

The story has generally been covered accurately by the press (in the UK, at least, thanks to some sensible comments sent out by the Science Media Centre); prize for most attention-grabbing headline goes to The Guardian: Why your sofa may harm your health.