Combined toxicity of cadmium and lead on the earthworm Eisenia fetida (Annelida, Oligochaeta)

Cadmium (Cd) and lead (Pb) in soil have received extensive attention due to their potential toxicological effects. This study analyzed the combined toxicity of Cd and Pb on the earthworm Eisenia fetida. Cellulase activity and DNA damage were chosen as toxic endpoints. Factorial analysis was applied to identify the interaction of Cd and Pb. The results showed that single Pb and Cd could increase the cellulase activity and DNA damage of coelomocytes. The combination of both metals could significantly inhibit cellulase activity. For low Cd concentration, the addition of Pb could increase the DNA damage. However, for high Cd concentration, Pb could decrease the DNA damage. Factorial analysis showed that the changes of Cd concentrations exerted the highest influence on the combined toxicity, followed by factor “Cd⁎Pb” and “Pb”. The combined toxicological effects between Cd and Pb were complex, which might be influenced by the competition adsorption of both metals in soil and biomembrane and their bioavailability. The results of this study are useful for understanding of combined toxicity of Cd and Pb on terrestrial invertebrates.

► Single Pb and Cd increase cellulase activity and DNA damage of Eisenia fetida.
► Combination of Cd and Pb inhibits cellulase activity.
► Combined effects of Cd and Pb on DNA damage depended on their concentrations.
► Cd concentrations had higher influences on combined toxicity than Cd*Pb and Pb.