A chemical commonly found in non-stick cookware and stain- and water-resistant coatings for carpets and fabrics could contribute to thyroid disease in people, according to a new study.
Scientists with the University of Exeter and the Peninsula Medical School said in a statement that people with higher concentrations of perfluorooctanoic acid, or PFOA, in their blood have higher rates of thyroid disease.
One researcher, David Melzer, a professor of epidemiology and public health at the Peninsula Medical School, said that his and his colleague's work show a "solid statistical link" between higher concentrations of PFOA in the blood and thyroid disease.
PFOA appears to get into the body by being swallowed or breathed in and there is no way of lowering levels in the blood.
Researcher David Melzer, a professor of epidemiology and public health, said: 'There have long been suspicions that PFOA concentrations might be linked to changes in thyroid hormone levels.
'Our analysis shows that in the "ordinary" adult population there is a solid statistical link between higher concentrations of PFOA in blood and thyroid disease.'
Concerns over PFOA (perfluorooctanoic acid) and a similar chemical PFOS since the 1990s led U.S. safety chiefs to link them to cancer. Manufacturers have agreed to phase them out by 2015.
Perfluorooctanoic acid (PFOA, 'C8') and perfluoroctane sulphonate (PFOS) are stable compounds with many industrial and consumer uses. Their persistence in the environment plus toxicity in animal models has raised concern over low-level chronic exposure effects to human health, the British researchers from the University of Exeter and the Peninsula Medical School said.
In their study, they analysed blood samples from the U.S. Centers for Disease Control and Prevention's National Health and Nutrition Examination Survey.
Included were 3974 adults with measured for PFC concentrations. Regression models were adjusted for age, sex, race/ethnicity, education, smoking status, body mass index, and alcohol intake.
In the event they found those with the highest 25 per cent of PFOA concentrations were more than twice as likely to have thyroid disease than individuals with the lowest 50 per cent of PFOA concentrations.
The study also showed that 16 per cent of women in the top quarter had the disease compared with just 8 in the bottom quarter.
But, they cautioned, more work was needed to establish the mechanisms involved and to exclude confounding and pharmacokinetic explanations.
Tamara Galloway, a professor in Ecotoxicology at the University of Exeter and the study's senior author, said: 'Our results highlight a real need for further research into the human health effects of lowlevel exposures to environmental chemicals like PFOA that are ubiquitous in the environment and in people's homes.'
Previous animal studies have shown the compounds can affect the function of the thyroid hormone system.
This is essential for maintaining heart rate, regulating body temperature and supporting many other body functions, including metabolism, reproduction, digestion and mental health.
But Dr Diane Benford, Head of Toxicology of Food at the Food Standards Agency, said: 'Studies of workers with higher exposure to these compounds have not shown consistent evidence of increased risk of thyroid disease, which would be expected if effects are occurring in the general population.'