In this paper, several studies were conducted to evaluate the genotoxicity of two pesticides,
Imidacloprid and
RH-5849, for earthworm (Eisenia fetida). Earthworms were exposed in different exposure systems to evaluate their acute toxicity and the genotoxicity of the two pesticides was evaluated by using the method of sperm
deformity assessment, micronucleus test of root tip cells in Vicia faba, a mouse bone-marrow micronucleus test, and comet assay. LC(50) (interpolated concentration at which 50% mortality of test population occurs) for earthworms varied in different exposure systems. The results indicated that
Imidacloprid was consistently more toxic than
RH-5849 in all exposure systems. In this study, sperm
deformity test was used to detect the potential adverse influences of pesticides on the reproduction of earthworms. The results demonstrated that significant induction of sperm
deformity (p<0.01) and a dose-effect relationship displayed at
Imidacloprid concentrations higher than 0.5 mg/kg dry soil. However, the sperm
deformity frequency of groups exposed to
RH-5849 did not show significant difference (p>0.05) from the control until the dose reached 100 mg/kg dry soil. The results of the V. faba micronucleus tests showed that micronuclei frequency of the exposed group did not show significant difference (p>0.05) from the control until the concentration of
Imidacloprid and
RH-5849 reached 100 mg/ml. The results of the mouse bone-marrow micronuclei test also indicate that two pesticides did not show significant effects (p>0.05) on the micronuclei frequency in mice bone-marrow cells until the dose reached 100 mg/kg for
Imidacloprid and 300 mg/kg for
RH-5849 (2/3 LD(50)). Although no genotoxicity was detected by using the micronucleus tests, the results of the comet assay showed that the two pesticides induce significant DNA damage (p<0.01) in earthworms and dose-effect relationships were displayed. The 'earthworm comet assay' is a rapid and sensitive way to screen chemicals or terrestrial environments for their
DNA-damaging properties.