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Leukemia mortality and occupational exposure to rubber: a nested case-control study.

OBJECTIVE
The excess risk of leukemia in rubber industry was considered to be real and attributed to the exposure to solvents, particularly benzene.


METHODS
Following a nested case-control study, we used the data of 7 leukemia deaths in 1973-1997 and 28 controls matched for sex and age from the same cohort of a rubber plant. Leukemia risks due to exposure to rubber were assessed, unadjusted and adjusted for non-occupational factors by conditional logistic regression.


RESULTS
OR for leukemia was found to be 7.81 (95% CI = 0.77-78) in grouped analysis for one or more years of work in the inner tire tube department. The models for continuous exposure variables indicated that working for one year in the inner tire tube department was associated with a 10 percent increment in the OR (95% CI = 1.00-1.24; score test for linear trend: chi 1(2) = 6.27, P = 0.012). The confounding effects studied could not be ruled out for the excess risks. No excess risk was found in the remaining four departments.


CONCLUSIONS
Because of widespread exposure to various carcinogens in the process of making inner tire tubes, removal of a single agent (benzene) may not eliminate the risk of leukemia in the entire industry.