Characteristics of heavy metal absorption of river bed sludge components

Chronic inhalation of aerosols of different Cd compounds by rats gave sufficient evidence that inhaled Cd is a lung carcinogen in rats. In contrast, the evidence in humans has been termed limited that inhaled Cd causes lung cancer in occupationally exposed humans. In order to assess the carcinogenic potential of ambient air concentrations of Cd, the accumulated dose of Cd in lung tissue from a rat inhalation study was modelled taking into account deposition and retention of Cd in the lung. A lung Cd—cancer incidence relationship could then be established, and an equivalent human exposure could be calculated using man specific pulmonary Cd retention and deposition data for Cd containing particle sizes in the ambient air. Linear interpolation to low doses showed that the pulmonary carcinogenic risk from inhalation of environmental airborne Cd is generally very low, but may reach about 1 × 10^‐4 in polluted industrialized areas. Combined exposures to Cd plus other carcinogens or air pollutants may increase the risk considerably. Cd in cigarette mainstream smoke was estimated to contribute less than 5 % of the total lung cancer risk from smoking cigarettes. However, the influence of co‐exposure to other compounds in cigarette smoke is not known and should be taken into account.