Having higher blood levels of PFCs -- which are compounds involved in the manufacturing of common products, including carpets, mattresses and food packaging -- may affect the functioning of women's thyroids, according to a new study.
PFCs, or perfluorinated chemicals, are considered persistent -- meaning they take a long time to break down. The National Institute of Environment Health Sciences explains how humans are exposed to these chemicals:
There is widespread wildlife and human exposure to several PFCs, including perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Both PFOA and PFOS are byproducts of other commercial products, meaning they are released into the environment when other products are made, used, or discarded. PFOS is no longer manufactured in the United States, and PFOA production has been reduced and will soon be eliminated. More research is needed to fully understand all sources of human exposure,
but people are most likely exposed to these compounds by consuming PFC-contaminated water or food, or by using products that contain PFCs.
In the new study, researchers from En Chu Kong Hospital, National Taiwan University Hospital and National Taiwan University College of Public Health found an association between higher levels of triiodothyronine, a thyroid hormone, in women, and higher levels of perfluorooctanoic acid (PFOA) in the blood. In addition, researchers found an association between higher levels of the PFC perfluorohexane sulfonate in women's blood, and increased triiodothyronine and thyroxine (another thyroid hormone) in women. They found that these higher levels of thyroid hormones did not occur within the scope of the body's natural process for hormone production.
"Although some PFCs such as PFOS 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," study researcher Dr. Chien-Yu Lin, M.D., Ph.D., of En Chu Kong Hospital, said in a statement. "Too little information is available about the possible long-term effects these chemicals could have on human health."
The findings, published in the Journal of Clinical Endocrinology & Metabolism, are based on data from 1,181 people who were part of the 2007-2008 and 2009-2010 National Health and Nutrition Examination Survey. For the survey, researchers analyzed levels of four different kinds of PFCs, in addition to thyroid functioning of the participants.
Researchers purposely left out people who had a history of thyroid diseases from their study population. Yet they found that having higher levels of the PFCs perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonate (PFHxS) was associated with mild hypothyroidism, a condition where not enough hormones are produced by the thyroid gland, leading to symptoms of fatigue, weight gain and menstrual irregularities.
Last year, a study in the Journal of the American Medical Association showed an association between weakened vaccine effects and high levels of PFCs in children, Health.com reported.
"The immune system is more sluggish when these kids are vaccinated," the researcher of that study, Dr. Philippe Grandjean, M.D., who is an adjunct professor of environmental health at the Harvard School of Public Health, told Health.com. "It doesn't respond as well ... and produces less antibodies."