Simazine in Drinking Water: Complete Guide (2026)

What is Simazine and Why Does It Matter?

SIMAZINE: A COMMON HERBICIDE IN YOUR WATER SUPPLY

What Is Simazine and Where Does It Come From?

Simazine is a herbicide—a chemical used to kill weeds—that's been sprayed on crops across America since the 1950s. Farmers use it mainly on corn, sorghum, and sugarcane to control broadleaf and grassy weeds. When it rains, simazine doesn't stay put in the soil. It leaches down into groundwater and runs off into surface water sources that feed municipal water systems. Once in the water supply, simazine is stubborn. It breaks down slowly and can persist for years, which is why it shows up in tap water across the country.

The chemical enters water systems primarily in agricultural regions. It also comes from non-agricultural uses—some municipalities and industrial facilities apply simazine to control vegetation on roadsides, railroad rights-of-way, and industrial sites. The widespread application means widespread contamination. Our data shows simazine detected in 688 water systems nationwide, with 112 systems exceeding health-based guidelines.

Health Effects and Exposure Risks

At low levels, simazine exposure causes few immediate symptoms. But research shows concerning effects with long-term exposure. The EPA classifies simazine as a possible human carcinogen based on animal studies showing increased tumor rates at high doses. The Environmental Working Group (EWG) estimates that lifetime exposure to simazine at their health guideline level—0.04 ppb (parts per billion)—poses a one-in-a-million cancer risk.

Our data reveals the exposure problem: the average simazine level across affected systems is 0.076 ppb, nearly double the EWG guideline. In the worst cases, some systems detected simazine at 1.8 ppb—45 times the EWG standard. Children face particular concern because they drink more water per pound of body weight than adults, and their developing bodies may be more vulnerable to carcinogenic chemicals.

Regulatory Standards and the Gap

The EPA's legal limit for simazine is 4 ppb. This sounds protective, but the EWG guideline of 0.04 ppb is 100 times stricter. The difference matters. The EPA standard was set decades ago using outdated risk assessment methods. The EWG guideline reflects current science on cancer risk and includes a safety margin for vulnerable populations like infants and children. Of the 112 systems exceeding EWG guidelines, most likely comply with the EPA's weaker standard, meaning residents get no warning their water is unsafe by the latest science.

Where Simazine Contamination Is Worst

Texas dominates the problem: 398 of the 688 affected systems are in Texas. This makes sense. Texas is the nation's leading corn-producing state and has extensive agricultural groundwater use. Illinois follows with 95 systems, then North Carolina (51), Louisiana (32), and Indiana (25). These states share common factors: heavy corn and sorghum production, reliance on groundwater for drinking water, and soils that don't block chemical infiltration well.

The Corn Belt states face the highest risk because simazine application is heaviest there, and their sandy and loamy soils allow chemicals to move downward easily into aquifers. Coastal states and areas with clay-rich soils see less contamination because clay acts as a barrier.

Removing Simazine From Your Water

Standard carbon filters don't reliably remove simazine. Activated carbon can capture some, but performance varies widely depending on the filter's age and quality. Reverse osmosis systems are highly effective, removing up to 99.9% of simazine and other herbicides. These systems use pressure to force water through a membrane so fine that simazine molecules can't pass through.

If you live in Texas, Illinois, North Carolina, Louisiana, or Indiana—or any agricultural region—testing your water is the first step. Echo Water's testing identifies whether simazine is present and at what level. If detected above 0.04 ppb, a reverse osmosis system under your sink or a whole-home filtration system provides reliable protection. For families with young children, this protection is worth the investment.

Regulatory Standards for Simazine

Cities With the Highest Simazine Levels

States Most Affected by Simazine

Frequently Asked Questions

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