What is Endrin* and Why Does It Matter?

Endrin is a pesticide that was once widely used to control insects, rodents, and birds on crops like cotton and grains. The EPA banned most uses of endrin in the United States back in 1986, but its legacy lingers. Because endrin binds tightly to soil, it can persist in the environment for decades. Rainwater and agricultural runoff slowly carry trace amounts into rivers, lakes, and groundwater — which is how it ends up in drinking water supplies today.

Health concerns around endrin center mainly on the nervous system and liver. Short-term exposure to high doses can cause headaches, dizziness, nausea, and in severe cases, seizures (according to the EPA). Long-term, low-level exposure raises concerns about liver damage and neurological effects. Children and pregnant women are generally considered more vulnerable to pesticide exposure, though the available data on endrin specifically is more limited than for some other chlorinated pesticides. The good news is that current detection levels in U.S. water systems are extremely low.

The EPA's maximum contaminant level (MCL) for endrin is 2 ppb (parts per billion). That's the legal ceiling — the point at which a water utility must take action. Across the 15 water systems where endrin was detected, the average measured amount was just 0.011 ppb, and the highest recorded level reached 0.037 ppb. Both numbers sit well below the EPA's legal limit. No systems in this dataset exceeded any regulatory guideline. That said, the EPA's legal limits were set with feasibility and cost in mind, not purely on health grounds. Some researchers and advocacy groups argue that even low-level pesticide exposure warrants caution, particularly for children.

Geographically, New York accounts for the largest share of detections — 9 out of 15 systems. Kansas follows with 4 systems, and Florida and Oklahoma each report 1. The New York pattern likely reflects the state's history of intensive agricultural activity in certain regions, combined with older infrastructure that can concentrate trace contaminants. Kansas makes sense given its deep roots in grain and row-crop farming, where endrin was historically applied. Florida's detection could tie to legacy agricultural use in its northern farming regions. Oklahoma's single detection fits a similar story — decades-old pesticide applications that haven't fully cleared from the environment. In all cases, the detections appear to reflect historical contamination rather than active, ongoing pesticide use.

If you're on a water system where endrin has been detected — or you simply want peace of mind — filtration is your most reliable option. Activated carbon filters (the kind found in many under-sink and whole-house systems) are effective at reducing chlorinated pesticides like endrin. Reverse osmosis (RO) systems go a step further, removing a broad range of contaminants including pesticides, heavy metals, and more. An RO system paired with a carbon pre-filter gives you strong, layered protection. Echo Water's reverse osmosis systems are designed specifically for this kind of comprehensive removal. Pitcher filters with basic carbon cartridges offer some reduction but typically aren't as thorough for pesticide removal. Whatever system you choose, look for one certified by NSF International — that certification means the performance claims have been independently tested and verified.

The bottom line: endrin detections in U.S. drinking water are rare, and current levels are far below legal limits. But if you live in New York, Kansas, Florida, or Oklahoma — and especially if you have young children at home — it's worth knowing your local water report. You can find it at the EPA's Consumer Confidence Report database or request it directly from your utility. Knowledge is the first step. A good filter is the second.

Regulatory Standards for Endrin*

Cities With the Highest Endrin* Levels

States Most Affected by Endrin*

Frequently Asked Questions

Related Contaminant Guides