Perchlorate in Drinking Water
EPA limits, health effects, and what to do if your water is affected.
🩨 Health Effects
Perchlorate interferes with the thyroid gland's ability to produce hormones needed for normal metabolism. Children, fetuses, and people with thyroid disorders are most vulnerable. Long-term exposure can cause hypothyroidism and may impair fetal neurodevelopment.
📍 Sources in Water
Perchlorate contamination in drinking water comes from rocket fuel and explosives manufacturing, military installations, fireworks, and airbag inflators. It also occurs naturally in some arid western soils. Contamination is most prevalent in California, Texas, Nevada, and near defense manufacturing sites.
✅ What To Do
In 2023, the EPA finalized the first national drinking water standard for perchlorate, setting an MCL of 56 parts per trillion (0.000056 mg/L). Ion exchange and reverse osmosis are effective treatment methods. Water systems have until 2028 to comply with the new standard.
📜 Regulation History
The EPA finalized the first national MCL for perchlorate at 56 ppb (0.000056 mg/L) in 2023, after decades of debate. Compliance is required by 2028. Before this, Massachusetts (2 ppb) and California (6 ppb) had state-level standards. The EPA initially decided not to regulate perchlorate in 2008, reversed that decision in 2011, and finally proposed the rule in 2019. The WHO guideline is 0.07 mg/L.
🔬 How To Test Your Water
Certified lab tests for perchlorate cost $50-$100 using EPA Method 314.0 (ion chromatography) or Method 331.0 (LC/MS/MS). Home test kits for perchlorate are not readily available. Testing is most relevant near military installations, rocket fuel manufacturing sites, or fireworks facilities.
💧 Which Filters Remove Perchlorate?
Ion exchange resins (specifically strong-base anion exchange) are the most effective treatment for perchlorate. Reverse osmosis (NSF/ANSI 58 certified) also removes perchlorate effectively. Biological treatment (bioreactors) is used at the municipal level. Standard carbon filters are not effective against perchlorate.
🔗 Related Contaminants
Check your tap water for Perchlorate
Search your ZIP code to see if your water system has had Perchlorate violations, plus lead testing results and an overall safety grade.
Search your ZIP code →Data from the EPA's Safe Drinking Water Information System (SDWIS). MCLs reflect minimum federal standards; some contaminants may pose health risks below these thresholds.