Perchlorate in Drinking Water Frequent Questions

What is perchlorate and where is it found?

Perchlorate is a chemical compound that occurs naturally and can also be manmade. It is commonly used in solid rocket propellants, munitions, fireworks, airbag initiators, matches, and signal flares. Perchlorate has also been found in fertilizers and as a byproduct of improper handling of hypochlorite solutions used for drinking water treatment.
Perchlorate exposure occurs mainly through ingesting contaminated food and drinking water. You can also be exposed through tobacco products, household products such as bleach, dietary supplements, signal flares and fireworks, and contaminated dust at perchlorate production facilities.
The vast majority of communities are not expected to have perchlorate occurring at levels of concern in their drinking water.

Perchlorate interferes with the normal functioning of a person’s thyroid gland by reducing iodide uptake, which can affect thyroid hormone production. Thyroid hormones help keep the metabolism working properly and are critical for growth and development, including brain development.
Changes in thyroid hormone levels in pregnant women can have harmful effects on brain development in their children. Additionally, changes in thyroid hormone levels at other life stages can lead to hypothyroidism, harmful reproductive and developmental effects, and impacts to the cardiovascular system.
Based on the available science, a population at increased risk to health impacts on brain development from perchlorate exposure is children of hypothyroxinemic pregnant women with low iodine intake exposed during pregnancy to perchlorate levels above the proposed Maximum Contaminant Level Goal (MCLG). Young children may also be at increased risk.
If hypothyroxinemic pregnant women with low iodine intake are exposed to perchlorate levels above the proposed MCLG, it may have impacts on their children’s health including brain development. Young children may also be at increased risk. If you are concerned about your iodine intake and thyroid hormone levels during pregnancy, talk to your doctor.

The EPA is proposing a perchlorate National Primary Drinking Water Regulation (NPDWR) and Maximum Contaminant Level Goal (MCLG) as a result of the D.C. Circuit’s May 2023 decision in NRDC v. Regan.
The EPA is required per a consent decree to sign a proposed NPDWR and MCLG for perchlorate by January 2, 2026 and to sign a final rule by May 21, 2027.

The EPA is proposing a health-based Maximum Contaminant Level Goal (MCLG) at 0.02 mg/L (20 µg/L). Additionally, the EPA is proposing an enforceable Maximum Contaminant Level (MCL) for perchlorate at 0.02 mg/L (20 µg/L), 0.04 mg/L (40 µg/L), or 0.08 mg/L (80 µg/L).
For the small number of systems that find perchlorate above the MCL, the EPA is also proposing requirements for water systems to mitigate perchlorate, provide information about perchlorate to their consumers, and report to their respective primacy agency. The EPA anticipates that very few regulated water systems (approximately one tenth of one percent) are likely to find perchlorate in drinking water above the proposed MCLs.

Contact your water utility to find out your water system’s perchlorate levels. If you are concerned about perchlorate in your water, consider taking steps to reduce your exposure. Learn more about perchlorate in drinking water and what you can do.

Contact your water utility to find out your water system’s perchlorate levels, what actions the water system is taking to reduce perchlorate levels, and any steps you can take to reduce your exposure to perchlorate in drinking water.
If you are pregnant or planning to become pregnant and concerned about your risk factors, talk to your doctor.