The EPA’s Proposed Tap Water Standard for Rocket Fuel Perchlorate Threatens Millions

According to the agency’s technical support document, children drinking water at the EPA’s proposed standard are at risk of suffering harm to their brains and decreased IQs. Many children would be harmed; some, the EPA admits, will be at risk of suffering a “mild intellectual disability” and others could be “shifting from a gifted IQ level [of over 135] into a lower IQ category.” Yet the EPA says this would not be an “adverse effect” on health under the law, even though, indisputably, this is an adverse health effect.  

The EPA also chose its MCLG based on IQ loss alone, neglecting the other health harms and adverse neurodevelopmental outcomes that are likely to flow from low levels of perchlorate exposure interfering with the thyroid and brain development, including ADHD, expressive language delay, reduced school performance, and delayed cognitive development.  

The EPA relies on the quarter-century-old Unregulated Contaminant Monitoring Rule 1 (UCMR1, which was collected in 2000–2005) and on highly limited data. The agency also heavily biases its “updated” dataset toward water systems with low perchlorate levels by adding data only from the two states that already regulate perchlorate in drinking water. In fact, 82.5 percent of the data that the EPA relies upon to evaluate perchlorate occurrence is from the only two states (California and Massachusetts) that have regulated perchlorate, and most of that data was collected after those states adopted strict perchlorate standards. Yet even the EPA’s deeply flawed occurrence dataset shows that perchlorate was present in 40,656—or 20.7 percent—of the samples taken by water systems.

Buried in the appendices to the EPA’s technical documents is data that the agency strangely ignored in its analysis. For example, the U.S. Geological Survey (USGS) found perchlorate in more than 72 percent of drinking water samples, with a median detection level of 16 ppb. Nearly 55 percent of USGS groundwater samples and more than 93 percent of surface water samples found perchlorate. 

The EPA appendices also show that perchlorate was detected in 508 public water systems serving more than 17 million people, and a U.S. Centers for Disease Control and Prevention survey found perchlorate in 83 percent of tap water samples. Many of these detections were below the EPA’s extraordinarily unprotective proposed standard, but if the agency were to establish a perchlorate standard that protected the public, comprehensive and updated monitoring would clearly show widespread and problematic tap water contamination.

The EPA has been under sustained pressure from the DOD and its allies not to strictly regulate perchlorate. Perhaps not surprisingly, the EPA has chosen to be willfully blind to the likelihood of spreading perchlorate contamination from hundreds of DOD and other federal facilities, as well as industrial and Superfund sites. The EPA collected data in 2005 showing more than 100 such sites spread across the country, and the Government Accountability Office flagged hundreds of these perchlorate-contaminated sites in a 2010 report. But since then, the EPA has shown no discernable interest in collecting updated information on whether perchlorate contamination has spread from these and other sites.  

Moreover, even though it has been documented that the use of fireworks can cause perchlorate water contamination, the EPA ignored the more than doubling of fireworks use in the country since its national monitoring effort decades ago. The agency abruptly canceled a study in 2025 of the impacts of expanding fireworks use on perchlorate contamination. But the preliminary study’s data “strongly suggested that fireworks do impact drinking water sources across the U.S. and that their use leads to elevated surface and groundwater concentrations as well as increased deposition.” The EPA has also not sought updated data on whether the inappropriate storage and use of the water disinfectant hypochlorite (basically, bleach) is causing widespread tap water contamination. The EPA admits improper storage or use of this disinfectant can cause perchlorate contamination, but it has failed to require any national monitoring to determine its impact. Hypochlorite is now much more widely used than it was when the EPA last did national testing—in fact, it is now used by the majority of water systems that disinfect their water.