Heavy metals in small mammals in roadside environments: implications for food chains.

Lead, cadmium, nickel, and zinc were measured in soil, vegetation, earthworms, small rodents, and shrews from the immediate environs of 4 highways of various traffic densities (range less than 1,000 to c.100,000 vehicles per day) and from 2 control areas. Concentrations of all elements in soil, vegetation, and earthworms varied with volume of traffic and with distance from highways. Concentrations in earthworms of all elements were especially high. Shrews had higher concentrations of lead and cadmium than other small rodents from similar areas.