Stain-repellent Chemical Linked to Thyroid Disease

A study published in Environmental Health Perspectives links, for the first time, 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 US Centers for Disease Control and Prevention’s nationally representative National Health and Nutrition Examination Survey, the study revealed that people with higher concentrations of PFOA in their blood were more likely to report a history of thyroid disease.

Tamara Galloway, a professor of ecotoxicology at the University of Exeter 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. PFOA can also be formed by the breakdown of certain other highly fluorinated chemicals used in oil- and grease-resistant coatings on fast-food containers and wrappers and in stain-resistant carpets, fabrics, and paints.

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% of PFOA concentrations were more than twice as likely to report being on medication for current thyroid disease as individuals with the lowest 50% of PFOA concentrations.

Numerous animal studies show that PFAAs can affect the functioning of the mammalian thyroid hormone system, which is essential for maintaining heart rate, regulating body temperature, and supporting many other body functions, including metabolism, reproduction, digestion, and mental health.

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.

Source: Environmental Health Perspectives