
The study by Kozak et al demonstrates that metal intoxication in dogs is a direct reflection on environmental pollution. Lead, cadmium and arsenic raise particular concern because of these toxins wide-spectrum negative influence on live organisms.
http://www.detoxmetals.com/content/ANIMALS%20AND%20PETS/Heavy%20metals%20in%20dogs.pdf
Studies by the South Korean Institute of Public Health and Environments of Seoul indicate that dogs are a very good indicator of the pollution load on the Environment. The animals studies showed significantly elevated lead (Pb) Levels. Cadmium (Cd), Mercury (Hg), and Chromium (Cr) were also high, and increased with age. Dogs fed Commercial pet foods had significantly higher Cd and Cr concentration in hairs. Dogs of smokers showed higher concentrations of toxic metals then dogs from nonsmokers.