Common Household Chemical PFOA Linked to Thyroid Disease

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Your couch, carpet, pots and pans, food, and even your clothing may contain a household chemical called PFOA that has been linked to an increased risk of thyroid disease. The research, which was conducted at University of Exeter and Peninsula Medical School, is the first major study to investigate the effect of PFOA on health.

PFOA stands for perfluorooctanoic acid, a substance perhaps most known for its use on nonstick cookware. Manufacturers use PFOA to make fluoropolymers, which are turned into flame retardants for furniture, stain protection treatment for carpeting, greaseproof wrappers for food, waterproof clothing such as Gore-Tex, and wire coatings, along with Teflon® and other trademark products.

According to the Environmental Protection Agency (EPA), PFOA, once it enters the human body, is found in the tissues and organs of the general US population and remains in the body for a very long time. PFOA is believed to get into the body through household dust and contaminated food.

In the Exeter study, researchers surveyed the medical records of 3,966 otherwise healthy US adults aged 20 and older whose blood had been tested for PFOA and PFOS (perfluorooctane sulfonate, a related substance) between 1999 and 2006. The investigators found that individuals who had high levels of PFOA in their blood were twice as likely to have thyroid problems as those with the lowest levels of the chemical. The thyroid gland manufacturers and secretes hormones that control the body’s metabolism and are essential for regulating temperature and heart rate.

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The researchers found that 16 percent of women who had high levels of the chemicals had thyroid problems compared with 8 percent of those who had the lowest levels. In men the trend was similar but the number who had thyroid problems was small. The two most common thyroid diseases include hypothyroidism (underactive thyroid, associated with fatigue, weight gain, and depression) and hyperthyroidism (overactive thyroid, characterized by rapid heartbeat, weight loss, and nervousness). Generally, women are ten times more likely to experience thyroid problems than men.

Although these findings do not mean PFOA is directly responsible for the rise in thyroid disease, previous animal studies have shown that PFOA and PFOS can cause thyroid disorders and various other problems, including liver disease, cancer, and hormone imbalances.

Previous studies of people who live in areas near where PFOA and PFOS are manufactured have not shown a relationship between exposure to these chemicals and thyroid functioning, the largest study of such exposure is now being conducted near DuPont’s Washington Works plant in Marietta, Ohio, and Parkersburg, West Virginia. Results of the study are not expected until 2011.

For now, David Melzer, professor of epidemiology and public health at the Peninsula Medical School in Exeter, says “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.” In the United States, the FDA has a voluntary—not mandatory--agreement with several companies to phase out PFOA production over the next few years.

SOURCES:
Environmental Protection Agency
The Guardian, Jan. 21, 2010
University of Exeter news release

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