Genotoxicity of two novel pesticides for the earthworm, Eisenia fetida

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 a cute toxicity and the geno toxicity of the two pesticides was evaluated by using the method of sperm deformity assessment, micronucleus test of root t ip cells in Vicia faba, a mouse bone-marrow micronucleus test, and comet as say. LC50 (interpolated concentration at which 50% mortality of test popula tion occurs) for earthworms varied in different exposure systems. The resul ts indicated that Imidacloprid was consistently more toxic than RH-5849 in all exposure systems. In this study, sperm deformity test was used to detec t the potential adverse influences of pesticides on the reproduction of ear thworms. The results demonstrated that significant induction of sperm defor mity (p < 0.01) and a dose-effect relationship displayed at Imidacloprid co ncentrations higher than 0.5 mg/kg dry soil. However, the sperm deformity f requency 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 res ults of the V.faba micronucleus tests showed that micronuclei frequency of the exposed group did not show significant difference (p > 0.05) from the c ontrol until the concentration of Imidacloprid and RH-5849 reached 100 mg/m l. The results of the mouse bone-marrow micronuclei test also indicate that two pesticides did not show significant effects (p > 0.05) on the micronuc lei frequency in mice bone-marrow cells until the dose reached 100 mg/kg fo r Imidacloprid and 300 mg/kg for RH-5849 (2/3 LD50). Although no genotoxici ty was detected by using the micronucleus tests, the results of the comet a ssay showed that the two pesticides induce significant DNA damage (p < 0.01 ) in earthworms and dose-effect relationships were displayed. The 'earthwor m comet assay' is a rapid and sensitive way to screen chemicals or terrestr ial environments for their DNA-damaging properties. (C) 2000 Elsevier Scien ce Ltd. All rights reserved.