Previous research updated the mortality experience of North American synthetic rubber industry workers during the period 1944-1998, determined if leukemia and other cancers were associated with several employment factors and carried out Poisson regression analysis to examine exposure-response associations between estimated exposure to 1,3-butadiene (BD) or other chemicals and cancer. The present study used Cox regression procedures to examine further the exposure-response relationship between several unlagged and lagged, continuous, time-dependent BD exposure indices (BD parts per million (ppm)-years, the total number of exposures to BD concentrations >100 ppm ("peaks") and average intensity of BD) and leukemia, lymphoid neoplasms and myeloid neoplasms. All three BD exposure indices were associated positively with leukemia. Using continuous, untransformed BD ppm-years the regression coefficient (beta) from an analysis that controlled only for age was 2.9 x 10(-4) (p
We examined the relation between styrene and ischemic heart disease (IHD) mortality among 16,579 men in the synthetic rubber industry.
Associations were measured using stratified and multivariable analysis.
Compared with workers with no exposure to styrene, men in the highest quintile of average intensity of exposure (5.50+ parts per million [ppm]) and in the highest quintile of cumulative exposure (60.67+ ppm-years) had IHD rate ratios of 1.14 (95% confidence interval [CI]=0.96-1.35) and 1.07 (95% CI=0.90-1.27), respectively. Acute IHD was not associated with average intensity of exposure within the most recent 2 years or with other indices of exposure. Chronic IHD rates were elevated in subjects with the highest exposure; these associations were weak and imprecise, and evidence of a positive exposure-response relation was limited.
This study does not indicate that exposure to styrene causes fatal IHD.