What is Simazine and Why Does It Matter?

Simazine is an herbicide that farmers and groundskeepers use to kill weeds in cornfields, orchards, golf courses, and along roadsides. It belongs to a chemical family called triazines, the same group as the more well-known weed killer atrazine. After application, simazine doesn't stay put. Rain washes it off treated land and into streams, rivers, and groundwater — the same sources that feed many public water systems. It's a persistent chemical, meaning it breaks down slowly and can travel far from where it was originally applied.

Right now, simazine shows up in 354 water systems across the United States. The average detected level is 0.072 parts per billion (ppb), but some systems have recorded levels as high as 1.8 ppb. At low doses, short-term exposure is unlikely to cause immediate symptoms. But long-term exposure is a different story. The EPA classifies simazine as a possible human carcinogen (cancer-causing agent). Animal studies have linked chronic simazine exposure to liver and kidney damage, as well as disruption of the endocrine system — the network of hormones that controls everything from metabolism to reproduction (EPA). Children and pregnant women face the greatest concern, since developing bodies are more sensitive to hormone-disrupting chemicals even at low levels.

The EPA's legal limit for simazine in drinking water is 4 ppb. That number sounds reassuring until you compare it to the Environmental Working Group's (EWG) health guideline of 0.004 ppb — 1,000 times stricter. The EWG's guideline is based on current cancer risk research, not just what treatment plants can technically achieve. Of the 354 systems where simazine was detected, 57 had levels above the EWG health guideline. That means those systems are fully legal under federal law, but the water they're delivering may still carry meaningful long-term health risks according to independent scientists.

Geography tells a clear story about where simazine turns up most. Texas leads the country by a wide margin, with 204 affected water systems — far more than any other state. Louisiana (27 systems), Illinois (24), North Carolina (19), and Ohio (16) round out the top five. That pattern isn't a coincidence. These states share two things: heavy agricultural activity and warm, wet climates that help carry herbicides from fields into waterways. Texas and Louisiana sit downstream from some of the most intensively farmed land in the country. Illinois and Ohio are deep in the Corn Belt, where triazine herbicides have been applied for decades. North Carolina's mix of row crops and golf courses adds another layer of exposure. If you live in any of these states — especially in a rural area or near farmland — it's worth knowing what's in your water.

The good news is that simazine is very effectively removed by the right filtration technology. Activated carbon filters (the kind found in many under-sink and pitcher-style filters) can reduce simazine levels significantly. For the most complete protection, a reverse osmosis (RO) system removes up to 99% of simazine and hundreds of other contaminants in a single pass. Echo Water's reverse osmosis systems are designed specifically for this kind of whole-home or point-of-use protection, giving you clean water at the tap without relying on your utility to do all the work. If you're in one of the high-risk states, checking your annual water quality report (called a Consumer Confidence Report) is a smart first step. Your utility is required to send it every year, and it will show whether simazine has been detected in your supply. From there, matching the right filter to your actual water is the most effective thing you can do for your family's long-term health.

Regulatory Standards for Simazine

Cities With the Highest Simazine Levels

States Most Affected by Simazine

Frequently Asked Questions

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