Exeter Study Links PFOA to Thyroid Disease in U.S. Adults
A study for the first time links thyroid disease with human exposure to perfluorooctanoic acid (PFOA), a persistent organic chemical used in industrial and consumer goods, including nonstick cookware and stain- and water-resistant coatings for carpets and fabrics.
Using samples taken via the U.S. Centers for Disease Control and Prevention’s nationally representative National Health and Nutrition Examination Survey (NHANES), the study revealed that people with higher concentrations of PFOA in their blood were more likely to report a history of thyroid disease.
The free article is available from Environmental Health Perspectives (EHP) at http://ehp03.niehs.nih.gov/article/info:doi/10.1289/ehp.0901584. EHP is published by the National Institute of Environmental Health Sciences (NIEHS), part of the U.S. Department of Health and Human Services. It is an Open Access journal.
Tamara Galloway, a professor of ecotoxicology at the University of Exeter (U.K.) School of Biosciences and the study’s senior author, says, “These results highlight a real need for further research into the human health effects of low-level exposures to environmental chemicals like PFOA that are ubiquitous in the environment and in people’s homes. We need to know what they are doing.”
PFOA is a very stable man-made chemical that excels at repelling heat, water, grease, and stains. It is used during the process of making common household and industrial items, including nonstick pots and pans, flame-resistant and waterproof clothing, wire coatings, and chemical-resistant tubing.
The study included 3,966 adults 20 or more years of age whose blood serum was sampled between 1999 and 2006 for PFOA and other perfluoroalkyl acid (PFAA) compounds, and who indicated whether they had ever been diagnosed with a thyroid problem or were currently taking medication for thyroid disease. The researchers found that the individuals with the highest 25 percent of PFOA concentrations were more than twice as likely to report being on medication for current thyroid disease as individuals with the lowest 50 percent of PFOA concentrations.
Although more research is needed to elucidate the mechanism by which PFOA may affect human thyroid functioning, Galloway says it is plausible that the compounds could disrupt binding of thyroid hormones in the blood or alter their metabolism in the liver. However, serum PFOA measurements were taken at the same time that study participants were asked about their history of thyroid disease, thus making it impossible to determine whether higher PFOA levels preceded the diagnosis. Galloway therefore stresses that the evidence from the new study does not rule out the possibility that having thyroid disease changes the way the body handles PFOA.
Other authors of the paper include David Melzer and Neil Rice of the Peninsula Medical School (U.K.) Epidemiology and Public Health Group, Michael H. Depledge of the Peninsula Medical School’s Environment and Human Health Group, and William E. Henley of the School of Mathematics and Statistics of the University of Plymouth (U.K.). Funding for the study came from Peninsula Medical School and University of Exeter internal support.