The analysis was conducted by Taiwanese researchers and published in the Journals of Clinical Endocrinology and Metabolism on July 17. They concluded that high levels of PFCs (perfluorinated chemicals) can alter thyroid function in both men and women.
The researchers also concluded that PFCs increase the risk of mild hypothyroidism, a condition caused by the thyroid gland failing to produce enough hormones.
Dr Chien-Yu Lin, one of the co-authors of the paper, said: "Our study is the first to link PFC levels in the blood with changes in thyroid function using a nationally representative survey of American adults."
The survey was based on data from more than 1,100 people over the age of 20 years who took part in the U.S. National Health and Nutrition Examination Survey from 2007-10.
The researchers found that although thyroid function was altered for both men and women, women with elevated serum levels of a particular type of PFC, perfluorooctanoate, were more likely to have elevated levels of T3.
The PFCs PFOA, PFHxS, and perfluorooctane sulfonate were found to be associated with subclinical hyperthyroidism in women.
Hypothyroidism causes symptoms such as fatigue, depression, weight gain, dry skin and hair, constipation and menstrual irregularities.
PFCs have been connected by other studies to developmental problems in children, decreased fertility and cancer in animals, although a link to humans has not been proven.
PFCs are persistent chemicals, meaning that they take a long time to break down in the environment. According to the EPA, PFCs are found “worldwide”, with high levels of exposure in both animals and humans.
Lin said: "Although some PFCs . . . have been phased out of production by major manufacturers, these endocrine-disrupting chemicals remain a concern because they linger in the body for extended periods.”
“Too little information is available about the possible long-term effects these chemicals could have on human health."
Scientific research into the large family of PFC compounds is still limited and after contacting The Personal Care Products Council, a representative said the body could not comment on the issue.