The disposition of coal dusts in the lungs and tracheobronchial lymph nodes of dogs.

The pulmonary disposition, histopathology and lymphatic uptake of anthracite (Tamaqua) and bituminous (Lower Kittaning) coal dusts were measured as part of a pulmonary retention study which revealed a mean half-time of 1.92 years in dogs (Morrow et al. 1981). After brief (1-2.5 hr) exposures to either natural or neutron-activated coals having an average airborne mass concentration of approximately 90 mg m-3 and a 1.8 mum mass median aerodynamic diameter (sigma g 2.5), dogs (n = 12) were serially sacrificed up to 52 weeks after exposure. Coal dusts were found only in the lungs and pulmonary lymph nodes. The coals were considered indistinguishable as to their pulmonary clearance and disposition and lymphatic uptake. All coals in the lung were associated mainly with the peribronchiolar and perivascular lymphatics or connective tissue spaces, and some were found in alveolar macrophages. The lymphatic uptake of coal dusts followed the powder function 0.55 t0.513 where t is in weeks and uptake is expressed as percent of the initial alveolar burden. In terms of pulmonary dust clearance, only 4 percent of the initial alveolar burden appeared to have been translocated to the tracheobronchial lymph nodes in the first 50 weeks, but this constituted approximately 14 percent of the total alveolar clearance. Histopathologically, one distinction was found: animals exposed to the highest level of neutron-activated anthracite showed patchy hyaline thickening of some small blood vessels and alveolar septa. The response was low grade, probably exposure-related, but otherwise unremarkable.