Exposure to a chemical called perchlorate may be unsafe for pregnant women and their unborn children, according to a new study.

Perchlorate, which is found in everything from fireworks to fertilizers, is a known hormone disruptor. In pregnant women, frequent exposure may decrease levels of a thyroid hormone, called T4, that’s necessary for fetal brain development, potentially leading to developmental issues after birth, according to new research presented Monday at the annual Society for Endocrinology conference in the U.K. While more research is necessary to determine the long-term effects of T4 deficiency, the study’s authors say the findings suggest that pregnant women may want to be extra cautious about perchlorate exposure.

Here’s what you need to know about the health effects of perchlorate:

What is perchlorate?

Perchlorate occurs both naturally and as a result of manufacturing, according to the Environmental Protection Agency. It’s used as a fuel starter for rockets, weapons, fireworks, airbag initiators, matches and flares, and it’s also found in some fertilizers, disinfectants, food packaging and plant killers. It’s often found in water supplies near where rocket fuel is made or used, the U.S. Environmental Protection Agency (EPA) says, but it also appears in other locations around the country. Studies have shown that it turns up in everything from lettuce to milk to bottled water.

Is perchlorate dangerous?

Studies, including the one mentioned above, have shown that perchlorate can disrupt the endocrine system, which regulates hormone levels. At high doses, according to the EPA, the chemical impairs the thyroid’s ability to absorb iodine from the blood, in turn causing the gland to malfunction and potentially underproduce hormones involved in metabolism and infant and childhood development. Studies in fish have also linked the substance to impaired sexual development and function.

Is perchlorate regulated?



Perchlorate’s road to regulation has been full of twists and turns. The EPA first raised a red flag in 1998, then collected data for years before issuing an initial risk assessment in 2002, Politico reports. That report, which suggested that perchlorate levels in drinking water should not exceed one part per billion, was met with backlash from NASA, the Department of Defense and the Department of Energy — all of which use perchlorate regularly — and after much back-and-forth, in 2008 the Bush administration decided not to formally regulate it. Shortly thereafter, an interim EPA advisory suggested that levels in drinking water should not exceed 15 parts per billion.

The Obama administration reopened the case in 2011. Though there’s been some movement since then — the EPA released a draft report on the topic in September of this year, and is currently accepting public input, here — no formal regulation for drinking water is on the books yet. (Two states, California and Massachusetts, have local regulations in place, and the FDA has limited the amount of perchlorate that can be used in food packaging.)

Dr. Nancy Beck, who is currently part of the EPA’s toxic chemical unit and had previously been an executive at the American Chemistry Council, a chemical industry trade association, has been accused of slowing the process of regulating drinking water contaminants including perchlorate, according to a recent New York Times report.

“EPA will continue to review the most up to date and best available science regarding perchlorate and drinking water,” an EPA spokesperson told TIME. “Earlier this year, EPA convened a peer review panel to provide recommendations on a biological model that predicts the relationship between perchlorate exposure and thyroid hormone levels in sensitive life stages. EPA is actively working to incorporate critical feedback and suggestions from this peer review.”

How can you minimize the risks of perchlorate?

Pregnant women and infants must get adequate iodine, the FDA says, either through dietary sources (dairy, seafood, meat, some bread, eggs and iodized table salt), fortified products or supplements, though it’s always smart to consult a doctor before beginning a new supplement regimen. If you live in an area where tap water is known to exceed the EPA’s interim advisory of 15 parts per billion, the FDA also recommends using bottled water to prepare infant formula. Not sure what’s in your water? You can consult the Environmental Working Group’s tap water database.

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Write to Jamie Ducharme at jamie.ducharme@time.com.