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Alachlor Degradates

Treatment Processes
Fate and Transport
CAS Number:
Synonyms: alachlor oxanilic acid (OA), alachlor ethanesulfonic acid (ESA)
Contaminant Type: Chemical

Alachlor or 2-chloro-2'-6'-diethyl-N-methoxymethyl acetanilide is a widely used herbicide in the United States, Europe, and Japan. It is a pre-emergent herbicide used in corn and soybean agriculture and is also a known endocrine distruptor. USEPA has classified alachlor as a B2 carcinogen and has set a maximum contaminant level (MCL) of 2 μg/l for alachlor in drinking water [1449].

While historically, alachlor has been the primary concern, research has recently shown that many of its environmental degradates also occur in drinking water sources. Hydroxyalachlor (2-hydroxy-2',6'-diethyl-N-(methoxymethyl)acetanilide) has been shown to possess similar toxicity to alachlor. Two additional alachlor degradates, 2-choloro-2',6'-diethylacetanilide and 2-hydroxy-2',6'-diethyacetanilide have been shown to be weakly mutagenic, and 2-chloro-2',6'-diethylacetanilide has been shown to form DNA adducts (DNA bonded to a cancer causing chemical). The primary aniline degradate of alachlor, 2,6-diethylaniline, has been reported to be teratogenic and can be altered to demonstrate mutagenic behavior [1449].

Although environmental degradates of the chloroacetamide herbicides are not currently regulated in the United States, they are included on the US EPA's Contaminant Candidate List (CCL3) for which drinking water standards may be established in the future [1450]. Alachlor EthaneSulfonic Acid (ESA) and Alachlor Oxanilic Acid (OA) are the two degradates on the CCL3. 

Date of Literature Search: June 2009

1449 Hladik, M., Roberts, A. and Bouwer, E.; 2005; Removal of neutral chloroacetamide herbicide degradates during simulated unit processes for drinking water treatment; Wat. Res.; 39::20:5033
1450 Hladik, M., Bouwer, E. and Roberts, A.; 2008; Neutral degradates of chloroacetamide herbicides: occurence in drinking water and removal during conventional water treatment; Wat. Res.; 42:20:4905