Dimethachlor is a chloroacetanilide herbicide that interferes with the synthesis of very long-chain fatty acids (VLCFAs) in target plants (Yang et al., 2010). Because VL-CFAs are important lipid components in seeds and surface covering materials, such as plant waxes (von Wettstein-Knowles, 1993;Cassagne et al., 1994), compounds of the chloroacetanilide family have been used in crop production for more than 50 years (Junghans et al., 2003). Although these herbicides effectively increase agricultural productivity via the regulation of unwanted weeds, they have caused environmental pollution by leaching. For example, other chloroacetanilides, such as acetochlor, alachlor, and metolachlor, are detectable in surface water samples from rivers and streams (Battaglin et al., 2000). In the case of dimethachlor, its water solubility is 2,300 mg/ L; thus, a large amount of dimethachlor dissolves in water (Lewis et al., 2016). As the exposure of aquatic ecosystems to dimethachlor is highly probable because dissolved herbicides can leach with water flow (Ferreira Mendes et al., 2020), it is necessary to identify whether dimethachlor has a harmful effect on aquatic organisms.