Leukemia risk in caprolactam workers exposed to benzene

Purpose To investigate the leukemia risk in a group of benzene exposed workers. Methods We conducted a retrospective cohort mortality study on 311 men who worked between January 1, 1951 and December 31, 1968 in a Caprolactam plant in the Netherlands. In the production of Caprolactam (the Nylon 6 monomer) pure benzene is used as an extracting agent and the workers at this plant have been exposed to substantial concentrations of benzene. The cohort was followed for mortality until January 1, 2001. The total mortality was below the expected number, which was mainly caused by a deficit of cardiovascular disease mortality. Results In the total group, there was one death from leukemia, compared with an expected number of 1.17. Despite the substantial exposures to benzene (on average 159 ppm-years per person) there was no indication for increased leukemia mortality within the cohort. We have applied earlier quantitative risk assessments to our cohort and conclude that some of these assessments overestimate the risk observed in our cohort of Caprolactam workers.