What is Dicamba* and Why Does It Matter?

Dicamba is a broadleaf herbicide that farmers have used since the 1960s to kill weeds in corn, soybean, and wheat fields. It works by mimicking plant growth hormones, causing uncontrolled cell growth that kills the target plant. Rain and irrigation water carry dicamba residues off treated fields and into nearby streams, rivers, and groundwater. From there, it can enter municipal water systems that draw from those sources. Its use has surged in recent years alongside the adoption of dicamba-resistant crop varieties, making it a more common presence in agricultural watersheds.

Dicamba currently appears in 22 water systems across the U.S., with an average detected level of 0.135 parts per billion (ppb) and a peak measurement of 0.493 ppb. At those concentrations, the immediate health risk appears low. That said, research on long-term, low-level exposure is still developing. Some animal studies suggest dicamba may affect the liver and kidneys at higher doses. The International Agency for Research on Cancer (IARC) has not classified dicamba as a human carcinogen, but the EPA notes that chronic exposure warrants monitoring. As with many pesticides, the concern isn't a single glass of water — it's years of regular, low-level exposure that researchers are still working to understand.

The EPA has set a maximum contaminant level (MCL) — the legal limit in public drinking water — for dicamba at 200 ppb. Every detection in this dataset falls well below that threshold, which is why zero systems currently report levels above the regulatory guideline. However, the EPA's legal limit and a true health-protective level aren't always the same number. The Environmental Working Group (EWG) points out that many MCLs were set decades ago and haven't been updated to reflect newer science. For a pesticide like dicamba, whose use has expanded significantly, that gap between legal and precautionary is worth keeping in mind.

Geographically, dicamba detections cluster heavily in agricultural states. Illinois leads with 11 affected systems, followed by South Carolina with 5 and New York with 4. North Carolina and Alabama each report 1 detection. Illinois sits at the heart of the Corn Belt, where dicamba-tolerant soybeans and corn dominate millions of acres. South Carolina and North Carolina both have significant row crop agriculture, particularly soybeans, where dicamba use has grown sharply. New York's detections likely reflect agricultural activity in the state's rural upstate regions. If you live in a farming community near soybean or corn country, your water source deserves a closer look.

The good news is that effective filtration options exist. Activated carbon filters — the kind found in many countertop and under-sink systems — can reduce dicamba concentrations meaningfully. For the most thorough protection, reverse osmosis (RO) filtration removes up to 99% of pesticide residues, including herbicides like dicamba. An RO system works by pushing water through a semi-permeable membrane that blocks contaminants at the molecular level. Echo Water's systems use multi-stage filtration that combines activated carbon with reverse osmosis, addressing not just dicamba but the full range of agricultural chemicals that commonly appear together in water supplies. If you're in Illinois, South Carolina, or another state with confirmed detections, it's worth requesting your utility's annual water quality report — called a Consumer Confidence Report — and checking whether dicamba appears on the list. Knowing what's in your water is the first step. Filtering it out is the easy part.

Regulatory Standards for Dicamba*

Cities With the Highest Dicamba* Levels

States Most Affected by Dicamba*

Frequently Asked Questions

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