Lung deposition and clearance of cadmium in rats exposed by inhalation or by intratracheal instillation.

115mCdCl2 was nebulized by a jet nebulizer, yielding an aerosol concentration of Cd of 660 ng/l. Rats were exposed nose only for 1 h. For the instillation study 115mCdCl2 was instilled intracheally, 8 microgram in 0.3 ml NaCl. Rats of both studies were serially sacrificed from day 0-100, and the lung activity was counted. The results showed a bi-exponential clearance pattern in both studies, where the long clearance gave half lives of 61 d (inhalation) and 66 d (instillation), respectively. The short term clearance half lives were 1.1 d (inhalation) and 0.7 d (instillation). About half of the deposited Cd is cleared in both studies in the fast phase. After inhalation, 16% more Cd was deposited in the alveolar area as compared to instillation. It was found that on the second day after instillation of CdCl2 only 2% could be lavaged out of the lungs, suggesting a protein binding of Cd in the lung.