Exploratory assessment of the risk of lung cancer associated with exposure to diesel exhaust based on a study in rats. Exploratory diesel risk assessment

A request was made by the Mine Safety and Health Administration to assess quantitatively the risk of lung cancer among those occupationally exposed to diesel exhaust. The Armitage-Doll multistage model was adapted to fit both the cases of all tumors and malignant neoplasms alone. A number of assumptions were made to extend the risk estimates derived from the models of tumor response in rats to the risks for humans. These assumptions fell into three categories: those concerning the development of biologically equivalent doses for rats and humans, those relating external exposure to internal dose, and those concerning the scaling of age between rats and humans to account for the temporal aspects of exposure. Uncertainties in the study included the effects of exposure on lung clearance mechanisms, the deposition rates in humans, and the relevance of the exposure index limit. Based on the findings of the study the excess risk to miners of lung cancer at the upper range of the diesel particulate exposure reported, 1.5mg/cu m, was approximately 1.5 to 3 in 100. According to the authors, the results are consistent with previous recommendations by NIOSH that diesel exhaust should be regarded as a potential human carcinogen, and that effortsmore » should be made to reduce exposures to the lowest feasible concentration.« less