Pooled study of occupational exposure to aromatic hydrocarbon solvents and risk of multiple myeloma

The relationship between occupational exposure to aromatic hydrocarbon solvents and risk of multiple myeloma (MM) in a large, Interlymph consortium-based study consisting of 2854 cases and 10743 controls. Occupational exposures to benzene, toluene, and xylene were assigned by a job-exposure matrix, coupled with "correction" of exposure probability by self-reported or expert-assessed exposure from the individual studies. Cumulative intensity was calculated as the job-specific exposure intensity multiplied by job duration, summed across jobs. The relationships were estimated using logistic regression, with inclusion of covariates for study matching factors and other potential confounders. For the three solvents, the highest quartile of high-probability cumulative intensity exposure (vs. unexposed) was associated with 42% to 63% increased risks of MM. Relationships with toluene and xylene exposures were fairly consistent and robust to sensitivity analyses. The estimated effect for benzene was moderately heterogeneous between the studies. Each solvent's association with MM was stronger for exposure occurring within 20 yr of diagnosis than with exposure lagged by more than 20 yr.