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By Tom Neltner
Pursuant to a consent decree with the Natural Resources Defense Council (NRDC), the U.S. Environmental Protection Agency (EPA) is developing drinking water regulations to protect fetuses and young children from perchlorate, a toxic chemical that inhibits the thyroid's ability to make the hormone T4 essential to brain development. The rulemaking is part of a long process that began in 2011 when the agency made a formal determination that Safe Drinking Water Act standards for perchlorate were needed. Under the consent decree, EPA should propose a standard by October 2018.
In the latest step in that process, EPA's scientists released a draft report in September that, at long last, answers questions posed by its Science Advisory Board in 2013: does perchlorate exposure during the first trimester reduce production of T4 in pregnant women with low iodine consumption? Does reduction in maternal T4 levels in these women adversely affect fetal brain development? According to EPA's scientists, the answers are Yes and Yes.