Modeling cadmium dynamics in the guts and tissues of small mammals: dose implications for predators

Predators that consume contaminated small-mammal prey are exposed to pollutants present in both the prey tissues and the prey gut. However, the contribution of the prey gut and its contents to the contaminant intake of the predator is often ignored. This study developed a two-compartment model of the dynamics of Cd in a model prey species, the wood mouse (Apodemus sylvaticus). The results from the Cd dynamics model were used to calibrate a revised predator dose estimation methodology that accounted for contaminant uptake by a predator from both prey tissues and guts. The dose to the predator predicted by the revised methodology was compared to that predicted by conventional dose calculations, which account for contaminants in prey tissues only. The conventional approach underestimated Cd dose to a model predator by a factor of 1.2- to 10-fold, depending on prey age and predator behavior. Thus, accounting for the contaminant burden in the prey gut as well as in the tissues can markedly increase dose estimates to predators, and this is likely to be true for most low-bioavailability pollutants. This study has major implications for ecological risk assessment involving food chain transfer of low-bioavailability xenobiotics to predators.