What is Perchlorate* and Why Does It Matter?

Perchlorate is a chemical compound that shows up in tap water more often than most people realize. It comes from two main sources: industrial activity and nature itself. Rocket fuel, explosives, and fireworks manufacturing all release perchlorate into the environment. From there, it seeps into groundwater and eventually into drinking water systems. Some perchlorate also occurs naturally in certain soils and mineral deposits, particularly in arid regions of the American Southwest.

The health concern with perchlorate centers on the thyroid gland. Your thyroid uses iodine to make hormones that regulate metabolism, energy, and development. Perchlorate competes with iodine for absorption, essentially blocking your thyroid from doing its job. At higher exposure levels, this can disrupt hormone production in adults. For pregnant women, infants, and young children, the stakes are higher. The EPA and National Academy of Sciences both recognize that developing fetuses and newborns are especially vulnerable, since thyroid hormones play a critical role in brain and nervous system development during those early stages.

Right now, perchlorate sits in a complicated regulatory position. The EPA established a maximum contaminant level (MCL) of 18 parts per billion (ppb) in 2019 — but then withdrew that rule in 2020, leaving perchlorate without a federally enforceable limit in public water systems. The Environmental Working Group (EWG) sets its own health guideline at just 0.1 ppb, based on the level they consider protective for the most sensitive populations. That gap matters. Of the 53 water systems in the national dataset that detected perchlorate, 2 tested above the EWG health guideline. The average detected level was 0.333 ppb — more than 3 times the EWG threshold. The highest recorded level reached 2.04 ppb, over 20 times that guideline.

California leads all states with perchlorate detections appearing in 30 water systems. That's not surprising. The state has a long history of aerospace and defense manufacturing, and perchlorate contamination from those facilities has been documented for decades. Massachusetts comes in second with 13 affected systems, reflecting its own history of military and industrial sites. Nevada follows with 4 systems, New York with 3, and Virginia with 1. The pattern holds: states with significant military bases, rocket testing sites, or munitions manufacturing tend to see higher perchlorate levels in their water. In California and Nevada especially, the dry climate means contaminants don't dilute as easily, which can concentrate levels in groundwater sources.

The good news is that perchlorate is one of the contaminants that water filtration handles well — if you use the right system. Standard pitcher filters and basic carbon filters don't remove perchlorate effectively. Reverse osmosis (RO) filtration is the most reliable option for home use. A properly functioning RO system removes up to 99% of perchlorate from drinking water, according to the EPA. Ion exchange filters, which swap perchlorate ions for harmless ones, are also highly effective and are commonly used at the municipal level. If you're on a well or live in one of the states with documented perchlorate detections, testing your water first is the smartest move. Knowing your actual levels helps you choose the right solution rather than guessing. Echo Water's reverse osmosis systems are designed specifically to address contaminants like perchlorate, giving your family a reliable layer of protection between the tap and your glass.

If you're in California, Massachusetts, or Nevada, perchlorate is worth taking seriously. The absence of a federal limit doesn't mean the risk disappears — it just means the responsibility shifts more to you. Check your annual water quality report, also called a Consumer Confidence Report, which your utility is required to provide each year. And if perchlorate shows up in your results, don't wait for regulators to act. A home filtration system puts the control back in your hands.

Regulatory Standards for Perchlorate*

Cities With the Highest Perchlorate* Levels

States Most Affected by Perchlorate*

Frequently Asked Questions

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