Occupational solvent exposure and adult chronic lymphocytic leukemia: No risk in a population‐based case–control study in four Nordic countries

The aim of this study was to assess the effect of occupational solvent exposure on the risk of adult chronic lymphocytic leukemia (CLL). The current case–control study was nested in the Nordic Occupational Cancer Study (NOCCA) cohort. 20,615 CLL cases diagnosed in 1961–2005 in Finland, Iceland, Norway, and Sweden, and 103,075 population‐based controls matched by year of birth, sex, and country were included. Occupational histories for cases and controls were obtained from census records in 1960, 1970, 1980/1981, and 1990. Exposure to selected solvents was estimated by using the NOCCA job‐exposure matrix (NOCCA‐JEM). Odds ratios (OR) and 95% confidence intervals (95% CI) were estimated by using conditional logistic regression models. Overall, nonsignificant CLL risk elevations were observed for methylene chloride, perchloroethylene, and 1,1,1‐trichloroethane. Compared to unexposed, significantly increased risks were observed for cumulative perchloroethylene exposure ≤13.3 ppm‐years (OR = 1.85, 95% CI 1.16–2.96) and average life‐time perchloroethylene exposure ≤2.5 ppm (1.61, 95% CI 1.01–2.56) among women, and cumulative methylene chloride exposure ≤12.5 ppm‐years (OR = 1.19, 95% CI 1.01–1.41) and 12.5–74.8 ppm‐years (OR = 1.23, 95% CI 1.01–1.51) among men in an analysis with 5 years lag‐time, though without dose–response pattern. Decreased CLL risk was observed for aliphatic and alicyclic hydrocarbon solvents and toluene. This study did not support associations for solvent exposure and CLL. Observed weak associations for methylene chloride, perchloroethylene, 1,1,1‐trichloroethane exposures, aliphatic and alicyclic hydrocarbons and toluene were not consistent across sexes, and showed no gradient with amount of exposure.