A new study by researchers at the University of Berkeley, California (UC Berkeley) shows a relationship between the already controversial chemical, bisphenol A (BPA), and thyroid hormone changes in pregnant women and newborn baby boys. This is the first study to link the chemical to altered thyroid hormones in babies. BPA—an estrogen-like compound—is used in hard plastics, the linings of canned food, dental sealants, and some paper receipts and has already been banned from baby bottles and sippy cups by the U.S. Food and Drug Administration (FDA).
According to the study, normal thyroid function is necessary to promote healthy growth and cognitive development of fetuses and children. The researchers analyzed BPA levels in urine samples from 335 pregnant women during the second half of their pregnancies as well as thyroid hormone levels in blood samples from the women and from their newborns. For every doubling of the mothers’ BPA levels, the study showed there was a 9.9 decrease in thyroid-stimulating hormone in their newborn sons. No similar effect was found in newborn girls; some animal studies suggest that females may be better able to metabolize BPA.
The women tested were part of the Center for Health Assessment of Mothers and Children of Salinas (CHAMACOS). California’s Salinas Valley is a low-income community of largely Mexican-American farm workers, and most of the mothers had lower levels of BPA—42 percent—than the average American woman. While the study does not prove that the compound affects babies’ thyroid hormones, scientists say the possible link needs more investigation.
In a news release from U.C. Berkeley, the study’s lead author, Jonathan Chevrier, research epidemiologist at the university’s Center for Environmental Research and Children’s Health (CERCH) was quoted, saying, “Most of the women and newborns in our study had thyroid hormone levels within a normal range, but when we consider the impact of these results at a population level, we get concerned about a shift in the distribution that would affect those on the borderline. In addition, studies suggest that small changes in thyroid level, even if they’re within normal limits, may still have a cognitive effect.”
According to Chevrier, thyroid hormones are being continually produced, and BPA doesn’t stay in the body for long, but ongoing exposure to the chemical may still be a cause for concern.
The study was published in the journal, Environmental Health Perspectives, which noted that only a few studies have investigated the potential neurological effects of BPA in children that include a link to hyperactivity in girls and other behavioral problems. Studies of animals show impaired memory, altered behavior, and gene changes. Previous research suggests that lowered thyroid hormones might have an effect on both motor skills and learning abilities. While high thyroid levels are usually problematic, causing developmental problems or mental retardation, too little thyroid hormone can cause reduced IQs or learning problems, according to Thomas Zoeller, a biology professor at University of Massachusetts-Amherst who specializes in studying thyroid hormones and brain development.
The American Chemistry Council, which represents chemical manufacturers, questioned the study’s validity. In a prepared statement, Steven Hentges of the council’s Polycarbonate/BPA Global Group, said, ““The author’s speculation that BPA is linked to health effects caused by thyroid hormone levels in women and newborns is not supported by the data; the authors themselves note that the thyroid hormone levels reported were within normal range and the study was not designed to measure any health effects. In addition, since BPA is efficiently metabolized and rapidly cleared from the body, the limited BPA exposure measurements reported do not likely provide an accurate measure of maternal exposure to BPA during pregnancy.
“BPA is one of the most thoroughly tested chemicals in the market used today and has a safety track record of 50 years. The consensus of government agencies across the world is that BPA is safe for use in food-contact materials. Not only have the U.S. Food and Drug Administration and Health Canada both recently reconfirmed that it is unlikely that BPA could cause human health effects, but the European Food Safety Authority and a World Health Organization panel have also supported the continued use of BPA in products that come in contact with food.”
Currently, 11 U.S. states have banned BPA from several products.