Whereas cadmium from occupational environments and cadmium from cigarette smoke are transferred directly to humans, cadmium in ambient air is generally deposited onto waters or soils, then eventually transferred to plants and animals, and finally enters the human body through the food chain. There are generally little or no differences noted in cadmium levels between indoor and outdoor air in non-smoking environments. Smoking, however, may substantially affect indoor ambient air cadmium concentrations. 3.1.2 Cadmium in Occupational Environments Cadmium air concentrations may be elevated in certain industrial settings, but these exposures are closely controlled today by national occupational exposure standards. Smoke Tobacco leaves naturally accumulate and concentrate relatively high levels of cadmium, and therefore smoking of tobacco is an important source of air cadmium exposure for smokers.
Smokers generally exhibit significantly higher cadmium body burdens than non-smokers.
Even greater variations are quoted for the cadmium contents of rainwater, fresh waters, and surface waters in urban and industrialised areas. Cadmium is a natural, usually minor constituent of surface and groundwater. Cadmium may enter aquatic systems through weathering and erosion of soils and bedrock, atmospheric deposition direct discharge from industrial operations, leakage from landfalls and contaminated sites, and the dispersive use of sludge and fertilisers in agriculture. Some data shows that recent sediments in lakes and streams range from 0.2 to 0.9 ppm in contrast to the levels of generally less than 0. Rivers containing excess cadmium can contaminate surrounding land, either through irrigation for agricultural purposes, dumping of dredged sediments or flooding.