Higher PFOA exposure increases risk of thyroid disease in children.
Lopez-Espinosa, MJ, D Mondal, Armstrong, B, MS Bloom and T Fletcher. 2012. Thyroid function and perfluoroalkyl acids in children living near a chemical plant. Environmental Health Perspectives http://dx.doi.org/10.1289/ehp.1104370.
High exposures to a well known stain repellent chemical have been linked to increased risk of thyroid disease in highly exposed children, according to a large study of communities in Ohio and West Virginia. The chemical is known as PFOA. Two related chemicals – PFOS and PFNA – were also linked to higher levels of a thyroid hormone called total T4 in these kids.
The results support findings from prior studies with adults. The study is important because it is the first large-scale report of PFOS, PFOA and PFNA exposures and thyroid function in children. More than 10,000 kids aged 1 to 17 took part in the study.
Because the thyroid gland affects nearly all body functions, changes in thyroid function can have head-to-toe consequences. Finding thyroid effects in highly-exposed children adds to the growing list of human health effects linked to PFOA and related chemicals.
Thyroid hormones play critical roles in metabolism, growth and brain development. They are especially important during fetal development and early infancy. Even small changes in thyroid hormone levels during these key periods are known to affect IQ and motor skill development in children.
The findings appear in the journal Environmental Health Perspectives.
DuPont's Washington Works plant on the Ohio River has used PFOA (also known as C8) since the 1950s to make key chemicals needed in the production of nonstick products, oil-resistant paper packaging and stain-resistant textiles. Fluorinated chemicals like PFOA break down slowly and can accumulate in people and animals.
The drinking water in communities in the Mid-Ohio Valley downstream from the plant contains high levels of PFOA. Adults from these communities have approximately 20 times higher PFOA levels in their blood compared to the general U.S. population.
Following the settlement of a class action lawsuit, a large-scale study – the C8 Health Project – was set up to examine the human health effects from exposures to PFOA and related chemicals. So far, adult exposure to PFOA has been linked to a number of health effects, including thyroid disease, high cholesterol, early signs of liver damage, testicular and kidney cancer, and pregnancy-induced hypertension and preeclampsia.
While PFOA, PFOS and PFNA are known to interfere with thyroid function in animal studies, results from human studies are still unclear. Most studies suggest an effect of the chemicals on adult thyroid hormones, but some report increases while others report decreases.
Overall, very little is known about thyroid or other health effects in children.
In this study, researchers measured the levels of PFOA, PFOS, PFNA and two thyroid hormones – TSH and total T4 – in blood samples collected between 2005 to 2006 from 10,725 children aged 1-17 enrolled in the larger C8 Project. They live in communities in Ohio and West Virginia downstream from the Washington Works chemical plant. Pre-birth exposures were also reconstructed for each child from chemical release information and calculated PFOA levels in drinking water during their mother's pregnancy. Both measures were compared with thyroid hormone levels and reports of thyroid disease at the time of study enrollment, controlling for age, gender and the month of sampling.
Children with higher measured PFOA levels were 1.4 times as likely to have thyroid disease – mostly hypothyroidism – compared to children with lower exposures. A similar but less precise trend was found for calculated pre-birth exposures to PFOA. Also, higher PFOS and PFNA, but not PFOA levels were associated with slightly higher total T4 levels in the children. No patterns were found with TSH.
Studies in adults have found similar trends. PFOS levels were also associated with higher total T4 levels in a study of 52,296 adults in the C8 Project. Higher PFOS and PFOA levels have also been linked to thyroid disease in the general U.S. population.
This work adds to the growing list of human health effects associated with PFOA and related chemicals, and is the first to report thyroid effects in children. Further studies are needed to see if similar effects occur in children from the general population, and to see if these chemicals are associated with long-term effects on child neurodevelopment.
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