Accumulation of lead and cadmium in wild populations of the commensal rat, Rattus norvegicus.

Lead and cadmium concentrations were analyzed in the tissues of Rattus norvegicus captured from a variety of urban and rural habitats in Houston, Texas. Variations in tissue metal concentations were expected to reflect differences in metal contamination among habitats. Tissue lead levels of urban rats were higher than those reported in the literature for other small mammal species while cadmium concentrations were lower. Lead accumulated with age in liver, kidney, and lung tissue of urban rats, and cadmium accumulated in liver and kidney tissue of female rats. Urban populations had more lead in their muscle, bone, liver, and kidney tissues as well as more cadmium in their liver tissue than did rural populations. Higher fecal lead and cadmium concentrations found among urban rats probable reflect higher levels of soil lead and cadmium contamination within urban environment and the relative human health risks associated with these levels.