Pulmonary retention and translocation of insufflated tantalum

Studies of pylmonary clearance of tantalum dust labeled with 182Ta in dogs have been extended to as far as 816 days postexposure in order to substantiate earlier pulmonary retention data, examine lymphatic uptake, and seek long-term pathological changes. Exposure to 5-mug and 10-mug powders was compared with the results of earlier 1-mug studies. The 2.1-year long-term clearance half-time of 1-mug powder was confirmed, while the 5-mug and 10-mug powders were found to have a mean long-term retention half-time of 333 days. All three particle sizes demonstrated rapid postinsufflation uptake by the pulmonary lymph nodes, followed by either retention or very slow clearance. No tantalum-induced pathological changes were found on histological examination.