Alachlor in Drinking Water
EPA limits, health effects, and what to do if your water is affected.
🩨 Health Effects
Long-term exposure above the MCL can cause eye, liver, kidney, or spleen problems, and anemia. Alachlor is a probable human carcinogen.
📍 Sources in Water
A widely used herbicide on corn and soybeans. Enters water through agricultural runoff. Detected in surface water and shallow groundwater in the Corn Belt, especially in the Midwest.
✅ What To Do
Activated carbon and reverse osmosis can reduce alachlor. Violations are most common in surface water systems in the Midwest during spring runoff.
📜 Regulation History
The EPA set the alachlor MCL at 0.002 mg/L (2 ppb) in 1991 under the Phase II rule, with an MCLG of zero due to its carcinogenicity. Alachlor use has declined significantly since the 1990s as farmers shifted to newer herbicides. The WHO guideline is 0.02 mg/L, less strict than the US standard.
🔬 How To Test Your Water
Certified lab tests for alachlor cost $50-$100 using EPA Method 525.2 (GC/MS). Home test kits are generally not available. Testing is most relevant for private wells in Corn Belt agricultural areas where alachlor was historically used.
💧 Which Filters Remove Alachlor?
Granular activated carbon (GAC) filters are effective at removing alachlor (NSF/ANSI 53 certified). Reverse osmosis also works. Carbon filtration is the most practical home treatment. Replace filters regularly during agricultural runoff season.
🔗 Related Contaminants
Check your tap water for Alachlor
Search your ZIP code to see if your water system has had Alachlor violations, plus lead testing results and an overall safety grade.
Search your ZIP code →Data from the EPA's Safe Drinking Water Information System (SDWIS). MCLs reflect minimum federal standards; some contaminants may pose health risks below these thresholds.