Comparative pulmonary responses of humans and animals to dust exposures

Human and animal responses to inhaled dusts are being compared to aid in the assessment of the risk to humans from inhaling diesel exhaust. Bioassay studies of rats exposed to high concentrations of diesel exhaust have been conducted, but no set of pathology materials from humans similarly exposed to diesel exhaust is available for comparison. Therefore, in the present study, tissue responses and the anatomic location of particles in the lung are being compared between rats exposed in studies of coal dust toxicity and miners in the National Coal Worker's Autopsy Study. Initial quantitative comparisons showed that coal particles were found primarily in the alveoli of rats and in the interstitium of miners. Tissue responses also differed with rats developing more inflammation and epithelial proliferation. Similar comparisons will be made between rats and humans exposed to other dusts. Pathology materials will also be identified from humans exposed to diesel exhaust so that direct comparisons can be made, A better understanding of the response of humans and rats to various types of particles in the lung will help to clarify the significance of bioassay study results in rats to the estimation of human health risks from inhaling diesel exhaust.