1,3-Butadiene and
styrene are suspected
carcinogens and common chemicals used in the synthesis of rubber. To investigate any potential human hazards from exposure to these chemicals, a case-control study of 59 lymphohematopoietic
cancers was conducted within a cohort of male workers employed between 1943 and 1982 in eight North American
styrene-butadiene rubber polymer-producing plants. A total of 193 controls were matched to the cases by plant, age, year of hire, duration worked, and survival to time of death of the case. Each job was assigned an estimated exposure rank, and each worker's cumulated rank score was calculated on the basis of the time spent in each job throughout his employment. "Exposure" as a dichotomous variable was defined as a log rank score above the mean of the log scores for the total population of cases and controls within a subtype of
cancer. Matched-pair analysis identified a strong association between
leukemia and
butadiene, with an odds ratio of 9.36 (95% confidence interval 2.05-22.9) and an association between
styrene and
leukemia (odds ratio = 3.13, 95% confidence interval 0.84-11.2) that did not achieve statistical significance. When exposure to both
styrene and
butadiene was included in a conditional logistic regression model, the odds ratio for
butadiene remained high (odds ratio = 7.39), but the estimated association of
leukemia with
styrene was small. The results of this study support the hypothesis that exposure to
butadiene is associated with the risk of
leukemia. There also appears to be an additional risk from work in specific subdivisions of the industry.