Comparative Genotoxicity of Cadmium and Lead in Earthworm Coelomocytes

To determine genotoxicity to coelomocytes, Pheretima peguana earthworms were exposed in filter paper studies to cadmium (Cd) and lead (Pb) for 48 h, at concentrations less than the LC10 Cd: 0.09, 0.19, 0.38, 0.75, and 1.50 μg cm-2; Pb: 1.65, 3.29, 6.58, 13.16, and 26.32 μg cm-2. For Cd at 0.75 μg cm-2, in the micronucleus test (detects chromosomal aberrations), significant increases (P<.05) in micronuclei and bi nucleate cells were observed, and in the comet assay (detects DNA single-strand breaks), tail DNA% was significantly increased. Lead was less toxic with minimal effects on DNA, but the bi nucleates were significantly increased by Pb at 3.29 μg cm-2. This study shows that Cd is more acutely toxic and sublethally genotoxic than Pb to P. peguana. Cadmium caused chromosomal aberrations and DNA single-strand breaks at 45% of the LC10 concentration. Lead, in contrast, did not induce DNA damage but caused cytokinesis defects.