The combined stress effects of atrazine and cadmium on the earthworm Eisenia fetida.

To assess the combined toxic effects of atrazine and cadmium on earthworms, specimens of Eisenia fetida were exposed in artificial soil to three concentrations of atrazine (0, 0.5, and 2.5 mg kg(-1)) and a range of concentrations of cadmium (Cd; 0, 0.03, 0.3, and 3.0 mg kg(-1)) both singly and as mixtures. The DNA damage and internal atrazine and cadmium concentrations were assessed in earthworms on days 7, 14, 21, and 28 of the treatment. The results showed that the olive tail moments (OTMs) at individual atrazine and cadmium concentrations were significantly higher than those of the controls (p < 0.01). As exposure to atrazine or cadmium progressed, the OTMs increased and the maximum value occurred on day 28. In all combined treatments, the OTMs were much less than those of the sum of individual atrazine and cadmium OTMs, suggesting that the combined effects of atrazine and cadmium were less than additive. The less than additive toxicity of atrazine and cadmium might be due to the formation of atrazine-cadmium complexes or the activation of detoxification isozymes. Moreover, there was a significant correlation between internal atrazine or cadmium concentrations and DNA damage in most exposures, indicating that body residues were consistent with toxicity response.