By STACY LIBERATORE, US SCIENCE & TECHNOLOGY EDITOR
Published: 00:34 BST, 4 August 2026 | Updated: 13:08 BST, 4 August 2026
The Environmental Protection Agency (EPA) is using data that is more than two decades old to develop the first nationwide drinking water standard for a toxic chemical that has been linked to lower IQ in children.
Perchlorate, used in rocket fuel, missiles, fireworks and military flares, can seep into groundwater that supplies public drinking water systems. Because it is colorless, odorless and tasteless, it cannot be detected without laboratory testing.
A Daily Mail analysis of the EPA's only nationwide survey of perchlorate, conducted between 2001 and 2005, found the chemical in 126 public water systems across 26 states.
Another nationwide occurrence survey was never conducted, and, because the aging survey does not reflect current contamination levels, it offers a murky picture of where perchlorate could still be detected and pose a risk today.
But the EPA is using that survey data – together with compliance monitoring data from California, collected in 2007, and Massachusetts, collected in 2023 – to determine how many water systems nationally could potentially exceed its court-ordered proposed drinking water limit for the chemical.
The agency must finalize the rule by the May 21, 2027 deadline.
The agency told the Daily Mail that the combined datasets are the 'best available representative data' for determining how frequently perchlorate occurs in public water systems and at what levels.
The EPA has repeatedly changed its position on perchlorate without ever putting a national drinking-water limit into effect.
Perchlorate, used in rocket fuel, missiles, fireworks and military flares, can seep into groundwater that supplies public drinking water systems
The agency opposed nationwide regulation under President George W Bush in 2008, arguing that perchlorate was not found at concerning levels often enough to justify a federal limit.
It reversed course under President Barack Obama in 2011 and concluded that a national standard was necessary under the Safe Drinking Water Act. The law required the agency to propose a regulation within two years, but it missed that deadline and was sued by the Natural Resources Defense Council (NRDC) in 2016 to force action.
In 2019, the EPA concluded that perchlorate can impair fetal brain development by disrupting thyroid hormone production, and identified reduced IQ in children following prenatal exposure as the most sensitive health effect when evaluating whether the chemical should be regulated in drinking water.
The agency's assessment relied in part on a human study that found women with the highest perchlorate levels during early pregnancy were more than three times as likely to have children whose IQ ranked in the lowest ten percent at age three.