The MDA monitors surface water (e.g., rivers, lakes) and groundwater in agricultural and urban areas for the presence of pesticides. A description of the MDA's Monitoring and Assessment Program and copies of water monitoring reports are available.
Acetochlor and its degradates (breakdown products) have been found by the MDA in both Minnesota's surface water and groundwater. Acetochlor water monitoring data are reviewed by the MDA for both the frequency and concentration at which acetochlor and its degradates are detected. Detected concentrations are compared to risk-based guidelines or standards established by the Minnesota Pollution Control Agency (MPCA) and the Minnesota Department of Health (MDH) to help evaluate potential risks (Table 3). State statute and agency policy lead the MDA to take action when pesticides are frequently detected or when detections occur at concentrations approaching or exceeding these numbers.
Table 3: Minnesota water quality guidelines or standards for acetochlor
| Water Resource | Chemical | Reference Number | Basis for Number | Responsible Agency |
|---|---|---|---|---|
| Drinking Water | Acetochlor parent | 20 μg/L1 | Chronic2 Health Based Guideline | MDH |
| Drinking Water | Acetochlor ESA degradate | 300 μg/L | Chronic Health Based Guideline | MDH |
| Drinking Water | Acetochlor OXA degradate | 90 μg/L | Chronic Health Based Guideline | MDH |
| Surface Water | Acetochlor parent | 3.6 μg/L | Chronic Water Quality Standard3 | MPCA |
| Surface Water | Acetochlor ESA degradate | 9,900 μg/L | Aquatic Life Benchmark for Nonvascular Plants | EPA |
1 μg/L stands for micrograms per liter, which in water is also equivalent to parts per billion (ppb).
2 Chronic guidelines and standards provide protection from long-term exposure over a period of days (surface water) or years (drinking water).
3 The MPCA Chronic Water Quality Standard for acetochlor was adopted into rule in 2008. The Standard has a time component; to violate the standard the average acetochlor concentration over a 4-day (96-hour) period needs to exceed 3.6 μg/L. It is based specifically on protecting aquatic plants, but is also protective of other aquatic life, water recreation, and drinking water sources
Detection of the acetochlor parent compound in groundwater is rare. When detected in groundwater, acetochlor has been found at very low concentrations relative to the standard. Acetochlor degradates have been found more frequently in groundwater but detected concentrations do not approach human health-based guidelines.
The MDA monitoring program has found both acetochlor and its degradates in surface water. Acetochlor has been found at concentrations that either approached or exceeded the water quality standards or guidelines at the time. Acetochlor has been designated as a “common detection pesticide” in groundwater and a “surface water pesticide of concern” in Minnesota. Acetochlor degradates have been found at low levels relative to aquatic life or human health guidelines.
