PURPOSE:  The retrospective cohort mortality and nested case control study is investigating risk of lung cancer in relation to quantitative measures of exposure to diesel exhaust. In addition, it will determine whether there is evidence of elevated mortality from other causes among miners exposed to diesel exhaust.

RESEARCH SUMMARY:  The mortality study cohort of about 10,000 miners comprises all non-office workers from eight selected mines who were employed for at least one year during the period from the date of dieselization at the mine until the end of follow up on December 31, 1997. A standard mortality ratio analysis will be undertaken, overall and by level of diesel exhaust exposure. Poisson regression and Cox proportional hazard modeling of mortality will be carried out using exposures derived from the exposure assessment phase of the project.

The nested case control study is based on deaths from lung cancer ascertained during the follow up stage of the cohort study. Four controls will be selected for each case from among members of the cohort who were alive at the time that the case died, matching on mine, year of birth, gender, and race/ethnicity. Information on smoking (active and passive) and other potential confounders (e.g., employment in high risk occupations for lung cancer, diet, and certain medical conditions) will be ascertained by interview of next of kin of deceased cases and controls and direct interview of living controls. Conditional logistic regression will be used to determine risk of mortality from lung cancer for various measures of diesel exhaust exposure, including cumulative exposure and average intensity.

Information from comprehensive industrial hygiene surveys at each working mine, together with past exposure and surrogate data, will be used to construct estimates of personal exposure for input into the cohort and case control studies. The measurements include elemental carbon (currently considered the most specific measure of general diesel exhaust exposure), submicrometer combustible dust, submicrometer particulate, the organic fraction of the exhaust, NO, NO2, CO, CO2, nitro-polycyclic aromatic hydrocarbons (nitro PAHs) and respirable and total particulate. Information on the operating and organizational structure of each mine, together with the sampling results, will be used to define uniform exposure categories (either job based or zone based). This information will be combined with data on significant change periods to develop a matrix of exposure levels by exposure category (zone or job). Then, by employing an exposure category/job dictionary and the job history for each person, individual exposure estimates will be developed. More detailed exposure information will be collected for each subject in the nested case control study in order to refine the exposure estimates.