Diesel exhaust has been classified as a probable carcinogen by the International Agency for Research on Cancer and as a potential carcinogen by the National Institute for Occupational Safety and Health (NIOSH). The carcinogenicity of this pollutant is of concern not only for the one million workers who are exposed occupationally, but also for the general population. Over 30 epidemiologic studies of diesel exhaust exposure have been performed, and the results suggest an increase in lung cancer risk. However, the association is not well defined. Past studies have suffered from the use of crude indicators of exposure, inadequate control of confounding, and/or short follow-up periods, low exposure levels, and small numbers of observations.

NCI and NIOSH are collaborating on two related studies of diesel exhaust under the NCI/NIOSH Interagency Agreement. First, a retrospective cohort mortality study of about 8,200 non-metal miners will be performed to investigate lung cancer mortality in relation to quantitative measures of diesel exhaust exposure, and to determine whether there is evidence of elevated mortality from other causes of death among diesel exhaust exposed miners. The retrospective cohort study will be performed using existing records and information and has been exempted from IRB review. NIOSH is the lead agency on the retrospective cohort study.

The proposed study is a case-control study nested in the retrospective cohort of non-metal miners. The study is expected to include at least 160 members of the cohort who died from lung cancer and four matched controls for each case. Using a structured questionnaire, detailed information will be collected on each subject's lifetime exposure to diesel exhaust, as well as information on smoking and other confounders. This information will allow investigators to examine the association between lung cancer and different quantitative measures of diesel exhaust exposure, adjusted for smoking and other potential confounders.