A new study from UC Berkeley has linked a mother's consumption of a chemical called bisphenol A (BPA) to a greater risk for an overactive thyroid in her newborn son.
"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," lead author Jonathan Chevrier, a research epidemiologist at UC Berkeley's Center for Environmental Research and Children's Health, said in a press release. "In addition, studies suggest that small changes in thyroid level, even if they're within normal limits, may still have a cognitive effect."
BPA is an estrogen-like compound that is commonly found in hard plastics, linings of canned food, dental sealants and sales receipts on thermal paper. According to the U.S. Department of Health and Human Services, the chemical has been in use for more than 40 years, and was declared by the Food and Drug Administration (FDA) to be market safe.
However, studies have showed that BPA may have an effect on laboratory animals, even in low amounts. Further research conducted by the National Toxicology Program at the National Institutes of Health and FDA have concluded there is some worry that BPA may affect the brain, behavior and prostate gland in fetuses, infants and young children. Another recent study also tied high BPA levels to childhood obesity
In July, thefrom baby bottles and sippy cups, but many manufacturers had been phasing the chemical out of these products in recent years.
This new research may show that the mother's consumption of BPA may affect her child. Researchers looked at BPA levels in urine samples of 335 women during the second half of pregnancy. Thyroid levels of the mother and newborn were determined using blood samples during pregnancy and a few days after birth, respectively.
Researchers found that every doubling of BPA levels in pregnant moms was tied to a decrease of 0.13 micrograms per deciliter of total thyroxine (T4), meaning their thyroids were less active. Boys whose mother's had doubled their BPA had a 9.9 percent decrease in thyroid stimulating hormone (TSH), meaning their thyroid was overactive.
Chevrier told the San Jose Mercury News that he believes because the mother's thyroid was less active, the newborn son's thyroid was working overtime to compensate for the loss.
Newborn girls were not observed to have any changes with thyroid levels. However, animal studies on rats showed females had a higher level of an enzyme important in metabolizing BPA.
Senior study author Kim Harley, adjunct associate professor of public health and associate director of CERCH, said in a press release that BPA is ubiquitous in our environment, with more than 90 percent of women of reproductive age having detectable levels in their urine. "Until we learn more about the human health effects of these chemicals, it would make sense to be cautious and avoid exposure when possible, particularly for those who are pregnant," she said
Tracey Woodruff, director of UCSF's Program on Reproductive Health and the Environment, said to the San Francisco Chronicle the study was especially important because it was the first to look at the chemicals effects on pregnant women. She was not involved with the research.
"This is one more study in the accumulating evidence that taking steps to avoid BPA would be prudent," Woodruff said to Mercury News.
The study was published in Environmental Health Perspectives on Oct. 4.