Chlorite in Drinking Water: Complete Guide (2026)

What is Chlorite and Why Does It Matter?

# Understanding Chlorite in Your Tap Water

Chlorite is a chemical byproduct of water disinfection. When water utilities use chlorine dioxide to kill harmful bacteria and viruses, chlorite forms as a leftover compound. It's not intentionally added like chlorine is — it's an unwanted side effect of the treatment process itself. Some utilities also use it directly as a disinfectant. Once chlorite enters your tap water, it stays there unless removed by filtration. This makes it different from chlorine, which naturally evaporates when you boil water or let it sit.

The problem is widespread. Across the United States, 986 out of 1,077 water systems tested exceeded the Environmental Working Group's (EWG) health guideline for chlorite. The average level found was 319 parts per billion (ppb), with some systems reaching as high as 2,410 ppb. Texas leads the nation with 383 systems exceeding safe levels, followed by Oklahoma (113 systems), Illinois (82), Colorado (68), and Alabama (68). These numbers tell you this isn't a rare issue — it's affecting water systems in nearly every region.

Health effects from chlorite exposure depend on how much you consume and for how long. Short-term exposure to high levels can cause gastrointestinal irritation, nausea, and vomiting. Long-term exposure at elevated levels concerns health experts more. The EWG set their health guideline at much lower levels than the EPA's legal limit because of potential links to anemia and nervous system effects with chronic exposure, particularly in children. The EPA's current legal limit is 1,000 ppb, but the EWG guideline is significantly stricter because new research suggests health risks at lower doses than the EPA's standard accounts for. This gap between EPA and EWG standards is why so many systems appear to exceed guidelines — they're legal by federal standards but exceed what independent health scientists recommend.

Geography matters significantly. Texas's dominance in chlorite exceedances likely reflects its heavy reliance on chlorine dioxide as a disinfectant in municipal water treatment. Southwestern and Midwestern states show higher rates because many older water systems in these regions use older disinfection methods that produce more chlorite as a byproduct. If you live in Texas, Oklahoma, Illinois, Colorado, or Alabama, your risk of exposure is notably higher than in other states. Even within these states, rural areas and smaller municipalities often have fewer resources for advanced water treatment, making them more vulnerable.

Removing chlorite requires specific filtration methods. Standard carbon filters remove some chlorite but aren't reliable enough on their own. Reverse osmosis systems are highly effective, removing up to 99.9% of chlorite and other chemical byproducts. Ion exchange systems can also work, though they're better suited for treating whole-home supplies rather than individual drinking water. Distillation removes chlorite completely by boiling water and condensing the steam, though it's slower and more energy-intensive. For families in high-risk areas, combining a reverse osmosis drinking water system with a whole-home filter for bathing and cooking provides the most comprehensive protection.

The best first step is testing your water. If you live in one of the affected states, contact your local water utility for their latest water quality report — by law, they must provide this annually. If results show chlorite above 500 ppb, a reverse osmosis drinking water system should be your priority. If levels are between 300-500 ppb, it's still worth filtering, especially if children or pregnant women drink from your tap regularly. Even if your system tests below the EPA limit, choosing filtration gives you the peace of mind that comes from knowing exactly what you're drinking.

Regulatory Standards for Chlorite

Cities With the Highest Chlorite Levels

States Most Affected by Chlorite

Frequently Asked Questions

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