Key Highlights
- Perchlorate is used in rocket fuel, fireworks and explosives, and can contaminate water through industrial and natural sources.
- It interferes with iodine uptake in the thyroid, affecting metabolism and development, especially in infants and pregnant women.
- Common treatment technologies include ion exchange, biological treatment and reverse osmosis, with effectiveness depending on the system.
Perchlorate is a naturally occurring and man-made chemical that can contaminate drinking water sources, raising concerns for utilities, regulators and public health officials. While perchlorate has long been used in industrial and defense applications, its presence in groundwater and surface water has made it an emerging issue for drinking water management—particularly in arid regions and areas with historical industrial or military activity.
Understanding what perchlorate is, where it comes from, and how it affects drinking water systems is essential for water professionals tasked with protecting public health and meeting regulatory expectations.
What is perchlorate?
Perchlorate is a chemical compound consisting of chlorine and oxygen (ClO₄⁻). It is highly soluble in water and does not easily break down, which allows it to persist in the environment once released. Perchlorate is best known for its use as an oxidizer in rocket fuel, fireworks, explosives, road flares and some industrial processes.
In drinking water, perchlorate is regulated due to its ability to interfere with the human body’s uptake of iodine, which is necessary for proper thyroid function. Because the thyroid plays a critical role in growth and development, especially for infants and pregnant women, perchlorate contamination is considered a potential public health concern even at low concentrations.
The U.S. Environmental Protection Agency (EPA) does not currently regulate perchlorate under the Safe Drinking Water Act. Enforceable standards are determined at the state level. California, for example, has established a maximum contaminant level (MCL) of 6 micrograms per liter (µg/L).
What are the sources of perchlorate in drinking water?
Perchlorate can enter drinking water supplies from both human-made and natural sources.
Man-made sources
The most common sources of perchlorate contamination include:
-
Manufacturing and disposal of rocket fuel and explosives
-
Fireworks production and displays
-
Military bases and weapons testing facilities
-
Industrial chemical production
-
Improper disposal of perchlorate-containing materials
These activities can lead to perchlorate leaching into soil and groundwater, where it may migrate into drinking water wells or surface water sources used for treatment.
Natural sources
Perchlorate can also form naturally in the atmosphere and be deposited on land through precipitation. In arid and semi-arid regions, natural perchlorate can accumulate in soils over time and eventually dissolve into groundwater. This is one reason perchlorate detections are more common in the southwestern United States.
According to the U.S. Geological Survey (USGS), naturally occurring perchlorate has been detected in groundwater even in areas without known industrial sources.
Are perchlorates toxic to humans?
Perchlorate is not acutely toxic in the way some contaminants are, but long-term exposure can pose health risks. Its primary concern lies in its effect on the thyroid gland.
Perchlorate blocks the uptake of iodine, which the body needs to produce thyroid hormones. Reduced thyroid hormone production can:
-
Disrupt metabolism
-
Affect brain development in infants and children
-
Increase the risk of developmental delays during pregnancy
The National Academies of Sciences has identified pregnant women, infants, and people with iodine deficiencies as the most sensitive populations.
For most adults, low-level exposure is unlikely to cause noticeable health effects, but water utilities must manage perchlorate carefully to protect vulnerable populations.
Do water filters remove perchlorate?
Whether perchlorate can be removed depends on the type of treatment technology used.
At the utility level
Public water systems use several effective treatment methods to remove perchlorate, including:
-
Ion exchange systems, which selectively remove perchlorate ions
-
Biological treatment, which uses microorganisms to reduce perchlorate to chloride
-
Reverse osmosis, which can remove perchlorate along with other dissolved contaminants
Ion exchange is the most commonly used technology for perchlorate treatment in municipal systems due to its reliability and cost-effectiveness.
At the point-of-use level
Not all household water filters remove perchlorate. Standard activated carbon filters (such as pitcher or faucet filters) are generally not effective. Filters certified for perchlorate reduction typically rely on:
-
Reverse osmosis
-
Specialized ion exchange media
Consumers looking to remove perchlorate should verify that a product is certified to NSF/ANSI Standard 58 or 53 for perchlorate reduction.
How is perchlorate regulated in drinking water?
There is no federal MCL for perchlorate, but EPA has determined that regulation is appropriate due to potential health risks. Several states have established their own enforceable limits, including:
-
California: 6 µg/L
-
Massachusetts: 2 µg/L
-
New Jersey: 5 µg/L
Utilities in affected regions must monitor perchlorate levels and implement treatment when concentrations exceed regulatory thresholds.
Why perchlorate matters to the water sector
Perchlorate presents a unique challenge for drinking water providers because it:
-
Persists in groundwater
-
Can originate from legacy contamination
-
Requires specialized treatment
-
Affects sensitive populations at low levels
As regulatory scrutiny increases and analytical methods improve, more utilities may identify perchlorate in their source waters. Proactive monitoring, source water protection, and treatment planning are critical for maintaining compliance and public confidence.
The bottom line
Perchlorate in drinking water is an emerging contaminant of concern with both industrial and natural origins. While it does not pose immediate toxicity risks for most adults, its impact on thyroid function—especially for infants and pregnant women—makes it a priority for drinking water utilities. With effective treatment technologies available and growing regulatory attention, water systems are increasingly equipped to manage perchlorate and protect public health.
About the Author
Alex Cossin
Associate Editor
Alex Cossin is the associate editor for Waterworld Magazine, Wastewater Digest and Stormwater Solutions, which compose the Endeavor Business Media Water Group. Cossin graduated from Kent State University in 2018 with a Bachelor of Science in Journalism. Cossin can be reached at [email protected].