Biomonitoring Summary


CAS No. 34256-82-1

General Information

Acetochlor is a chloroacetanilide type herbicide with restricted usage for preemergent control of grasses and broadleaf weeds on agricultural crop land, mainly corn. It is absorbed by plants and inhibits plant protein synthesis. Acetochlor is microbiologically degraded, remains in soils for up to 3 months, and has been detected in watersheds of agricultural lands (Battaglin et al., 2000; Hladik et al., 2005; Kolpin et al., 2000). Acetochlor degrades in water to acetochlor sulfonic acid and acetochlor oxanilic acid. Plants can degrade acetochlor to 2-ethyl-6-methylaniline, 2-hydroxyethyl-6-methylaniline, and hydroxymethyl ethyl aniline (U.S.EPA, 2006). Acetochlor is moderately toxic to fish and honey bees.

General population exposure to acetochlor may occur through diet or drinking water. Estimated human intakes of acetochlor have been below recommended limits (U.S.EPA, 2006). In animals, a major pathway for acetochlor metabolism involves mercapturate conjugation, but other pathways occur, including one that produces 2-methyl-6-ethylaniline and its reactive metabolite, the latter which may account for some observed tumor effects (Coleman et al., 2000; Davison et al., 1994; Feng and Wratten, 1989; Jefferies et al., 1998). People exposed to acetochlor will excrete acetochlor mercapturate in their urine; however, this metabolite is not a marker of exposure to most plant metabolites or environmental degradates, which are often more prevalent in the environment.

Human health effects from acetochlor at low environmental doses or at biomonitored levels from low environmental exposures are unknown. Acetochlor has low acute toxicity. Acetochlor has not shown developmental or fetal toxicity in chronic animal studies, but it produced testicular atrophy, renal injury, and neurologic movement abnormalities (U.S.EPA 2000, 2006). Acetochlor is not mutagenic, and it is unlikely to be genotoxic at relevant doses (Ashby et al., 1996). However, in some species and at doses above maximum tolerated doses, animals have demonstrated tumors of the lung, nasal epithelia, and thyroid (U.S.EPA, 2000, 2006). U.S.EPA considers acetochlor likely to be carcinogenic in humans; NTP and IARC do not have ratings regarding human carcinogenicity. Additional information about external exposure (i.e., environmental levels) is available from U.S. EPA at: icon.

Biomonitoring Information

Urinary levels of acetochlor mercapturate reflect recent exposure. Urinary levels of acetochlor mercapturate were generally not detectable in the NHANES 2001-2002 subsample (CDC, 2009). Acetochlor mercapturate was measured in the urine of farmers actively spraying the pesticide and the geometric mean was 8.0 µg/L (Curwin et al., 2005). Urinary acetochlor mercapturate levels of 0.5 to 449 µg/L were measured in commercial applicators within 24 hours following its application (Barr et al., 2007).

Finding measurable amounts of acetochlor mercapturate in the urine does not imply that the levels of acetochlor mercapturate cause an adverse health effect. Biomonitoring studies on levels of acetochlor mercapturate provide physicians and public health officials with reference values so that they can determine whether people have been exposed to higher levels of acetochlor than are found in the general population. Biomonitoring data can also help scientists plan and conduct research on exposure and health effects.


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