The largest airborne sources of cadmium in the environment are the burning of fossil fuels such as coal or oil and the incineration of municipal waste materials. Cadmium may also escape into the air from zinc, lead, or copper smelters. Exposure to cadmium may also occur through food. Application of phosphate fertilizers or sewage sludge may increase the cadmium levels in soil, which, in turn, can cause increased cadmium levels in food. Smoking is another important source of cadmium.
Smokers have about twice as much cadmium in their bodies as do nonsmokers.
Cadmium has been listed as a pollutant of concern to EPA's Great Waters Program due to its persistence in the environment, potential to bioaccumulate, and toxicity to humans and the environment. The amount of cadmium present in blood or urine can be measured by atomic absorption spectrophotometry and used as an indication of cadmium exposure. A more precise method, called neutron activation analysis, can be used to measure cadmium concentrations in the liver or kidney. A single acute exposure to high levels of cadmium can result in long-lasting impairment of lung function. Cadmium is considered to have high acute toxicity, based on short-term animal tests such as the LC 50 test in rats.