Babies born to mothers with high levels of perchlorate during their first trimester are more likely to have lower IQs later in life, according to a new study.
Perchlorate, which is both naturally occurring and manmade, is used in rocket fuel, fireworks and fertilizers. It has been found in 4 percent of U.S. public water systems serving an estimated 5 to 17 million people, largely near military bases and defense contractors in the U.S. West, particularly around Las Vegas and in Southern California.The research is the first to link pregnant women’s perchlorate levels to their babies’ brain development. It adds to evidence that the drinking water contaminant may disrupt thyroid hormones, which are crucial for proper brain growth.
“We would not recommend action on perchlorate levels from this study alone, although our report highlights a pressing need for larger studies of perchlorate levels from the general pregnant population and those with undetected hypothyroidism,” the authors from the United Kingdom, Italy and Boston wrote in the study published in The Journal of Clinical Endocrinology & Metabolism.
The Environmental Protection Agency for decades has debated setting a national drinking water standard for perchlorate. The agency in 2011 announced it would start developing a standard, reversing an earlier decision. In the meantime, two states, California and Massachusetts, have set their own standards.
EPA officials said they expect to unveil their proposed standard in the summer of 2015, missing their deadline by two years. They would not comment on the new findings.
Dr. Craig Steinmaus, an associate adjunct professor of epidemiology at the University of California, Berkeley School of Public Health, said it was a strong, first-of-its-kind study. “It’s not definitive, but it is certainly intriguing,” said Steinmaus, who was not involved in the research.The researchers analyzed perchlorate levels in the first trimester of 487 pregnant women in Cardiff, Wales, and Turin, Italy, who had iodine deficiency and thyroid dysfunction during pregnancy and examined their children’s IQ scores at 3 years old. Children born to mothers’ with perchlorate levels in the highest 10 percent were more than three times as likely to have an IQ score in the lowest 10 percent.
The study, however, did not factor in information about the home environment and the mothers’ IQs, which can affect children’s IQs.
Thomas Zoeller, a biology professor who specializes in thyroid hormones at University of Massachusetts-Amherst, said it is “very well established” that perchlorate can inhibit transport of iodine to the thyroid. Iodine is an essential component of thyroid hormones, and “severe iodine deficiency is the leading preventable cause of mental deficiency in childhood,” the authors wrote.
“Even mild hypothyroidism and/or hypothyroidism for a short period of time may have adverse neurocognitive effects in later childhood,” said Dr. Angela Leung, a clinical assistant professor of medicine at the University of California, Los Angeles, who was not involved in the study.
Previous studies have linked perchlorate exposure to altered thyroid function in mothers and women. However, Zoeller said what scientists don’t know is how and to what extent perchlorate in a pregnant woman might impair the mental abilities of her children. He said it is “very difficult” to pin chemical exposure during pregnancy to impacts on the fetus or child.
