Rats and monkeys differ in patterns of particle retention in the lungs after identical exposures to diesel exhaust (DE) or coal dust at a single concentration (2 mg respirable material/m3), resulting in moderate lung burdens. Here we extend the morphometric studies of particle retention to humans and examine the influence of exposure concentration on retention patterns in rats and humans. Histologic lung sections from a previous study in rats and from the National Coal Workers' Autopsy Study were examined morphometrically to estimate the volume percentage of particulate material in defined anatomic compartments, the rats had been exposed 7 h/day, 5 days/wk for 24 mo to DE at 0.35 (low), 3.5 (medium), or 7.0 (high) mg soot/m3; the 24mo soot lung burdens were 0.6, 12, and 21 mg, respectively. The human lungs sections were from 1) nonsmokers who did not work as miners, 2) nonsmoking coal miners who worked under the current standard of < / = 2 mg dust/m3 for 3 - 20 Y (mean = 13 y), and 3) nonsmoking coal miners who worked under the former standard of < 10 mg dust/m3 for 33-50 Y (mean =40 y). The volume percentage of the lung occupied by particulate material was 0.2, 1.6, and 3.7% in the low, medium, and high exposure concentration rats, respectively. The particulate material was predominately retained in macrophages in the alveolar and alveolar duct lumens, with 82, 81, and 85% of the material being in lumens and 18, 19, and 15% of the material being interstitial in the 1ow, medium, and high exposure concentration rats, respectively. The volume percentage of the lung occupied by particulate material was 0.3, 1.8, and 10.3% in the non-miners, coal miners under the current standard, and coal miners under the former standard, respectively. Fifty-seven, 68, and 91 % of the particulate material was interstitial, and the remainder was in lumens, in the non-miners, coal miners under the current standard, and, coal miners under the former standard, respectively. These results show that chronically inhaled diesel soot is similarly retained predominately in lumens of rats over a wide range of exposure concentrations and resultant lung burdens. In non-miners and coal miners, chronically inhaled particulate material is retained primarily in the interstitium, and the percent of the material in the interstitium is related to dose (exposure concentration, years of exposure, and/or lung burden).
Animal-studies; Laboratory-animals; Statistical-analysis; Analytical-methods; Analytical-chemistry; Exposure-assessment; Toxicology; Toxins; Toxic-materials; Pulmonary-system-disorders; Pulmonary-disorders; Respiratory-system-disorders; Respiratory-irritants; Lung-cells; Lung-disorders; Lung; Lung-irritants; Particulate-dust; Particulates; Diesel-emissions; Diesel-exhausts; Dust-exposure; Dust-inhalation; Dust-particles; Airborne-dusts; Airborne-fibers; Airborne-particles
The Toxicologist. Society of Toxicology 38th Annual Meeting, March 14-18, 1999, New Orleans, Louisiana