Nested case-control study of leukaemia, multiple myeloma, and kidney cancer in a cohort of petroleum workers exposed to gasoline.

OBJECTIVES This nested case-control study was based on data in a cohort study of more than 18,000 petroleum distribution workers exposed to gasoline, which contains about 2%-3% benzene. Risks of leukaemia, acute myeloid leukaemia, multiple myeloma, and kidney cancer were examined relative to exposure to gasoline. METHODS For each case, up to five individually matched controls were selected. Analyses based on the Mantel-Haenszel procedure as well as univariate and multivariate conditional logistic regression were performed for each disease category. Jobs with similar exposures were grouped into homogeneous categories for analysis. Several quantitative indices of exposure to gasoline were used in the analyses: duration of exposure, cumulative exposure, frequency of peak exposure, and time of first exposure. RESULTS No increased risks for the four cancers were found for any job category. Analyses with logistic regression models based on duration of exposure, cumulative exposure, and frequency of peak exposure did not show any increased risk or exposure-effect relation. Time of first exposure to gasoline was also found to be unrelated to the four diseases under investigation. CONCLUSION Exposure to gasoline or benzene at the concentrations experienced by this cohort of distribution workers is not a risk factor for leukaemia (all cell types), acute myeloid leukaemia, multiple myeloma, or kidney cancer.