Are low doses of tritium genotoxic to Mytilus edulis?

The genotoxic effects of tritium (3H) in the adult life stage of Mytilus edulis have been evaluated by the induction of micronuclei (MN) and DNA single strand breaks/alkali labile sites (Comet assay) in the haemocytes of exposed individuals. Assays were optimised and validated using ethylmethane sulfonate (EMS) as a reference genotoxic agent over different exposure periods. M. edulis were exposed, for 96 h, to a range of concentrations of 3H equivalent to a dose range of 12-485 microGy h(-1). Results revealed a dose-dependent increase for both the MN and Comet assays, and for both EMS and 3H. Since less than 500 microGy h(-1) 3H is capable of inducing genetic damage, generic doses recommended by the IAEA for the protection of aquatic biota may be overestimated for some organisms.