bioaccumulation of cadmium and lead in rodent species from the region of lead-zinc smelting factory – plovdiv (south bulgaria)

The levels of the toxic metals, Cd and Pb, were measured in liver of yellow-necked mouse (Apodemus flavicollis Melchior, 1834), Mediterranean mouse (Mus macedonicus Petrov & Ružić, 1983) and common vole (Microtus arvalis Pallas, 1778) from the vicinity of Plovdiv (South Bulgaria), where the lead-zinc smelting factory is the main source of pollution. The study was carried out at three sites located along a pollution gradient. An unpolluted region, the Strandzha Natural Park was used as a background region. MANOVA analysis revealed significant differences by species (F=9.61, p=0.003), site (F=24.12, p=0.0001) and exposure (F=3.79, P=0.013) effects. Significant increase of Pb and Cd bioaccumulation was found along the pollution gradient. Cd and Pb mean concentrations were highest at the site closest to the smelter and decreased with increasing the distance from them. The bioaccumulation of Pb was significant highest in the individuals of the yellow-necked mouse, followed by Mediterranean mice and common voles, whereas the common voles accumulated more Cd in comparison with the yellow-necked-, and Mediterranean mice. However, there is little evidence of adverse cadmium-mediated effects in yellow-necked- and Mediterranean mice and this species may be tolerant to Cd exposure. High Cd concentrations in body organs may simply reflect an ability to store the metal in a nontoxic, metallothionein-bound state. Liver Pb and Cd concentration did not differ significantly among sexes.