Mixture toxicity assessment of cadmium and benzo[a]pyrene in the sea worm Hedistediversicolor

In the present study, Hediste diversicolor biotransformation and anti-oxidant responses to acute exposure to cadmium (Cd) and to the polycyclic aromatic hydrocarbons benzo[a]pyrene (B[a]P) were investigated. Worms were submitted to 0.2, 0.4 and 1 μM of each contaminant and to their mixture during a period of test of 48 h. Following biological responses were measured: (1) NADPH cytochrome c reductase (NADPH cyt c) activity, as phase I biotransformation parameter; (2) gluthathione-S-transferase (GST) activity as a phase II conjugation enzyme, (3) catalase activity as anti-oxidant response and (4) malondialdehyde accumulation (MDA) as lipid peroxydation marker. The cholinergic system was evaluated using the acetylcholinesterase activity (AChE). Exposure to the mixture resulted in low dose level additive effects on the investigated biomarkers. However, worms exposed to 1 μM of the single compounds and to their mixture exhibited the highest MDA accumulation and the lowest enzymatic biomarkers activities suggesting severe toxicological effects. These data should be carefully considered in view of the biological effects of mixture pollutants and particularly in marine sediment ecosystems.