Objectives To evaluate lung cancer mortality in relation to quantitative estimates of cumulative inhalable carbon black exposure among carbon black manufacturing workers.
Method Standardised mortality ratios (SMRs) were calculated for 5675 workers employed ≥ 1 year since 1940 at 18 plants. Cox proportional hazards models were used to evaluate the association between cumulative inhalable carbon black exposure and lung cancer mortality risk for the “exposure” sub-cohort of 2099 men with complete work history records that allowed individual quantitative estimation of cumulative exposure.
Results All-cause SMR=0.80 (95% confidence interval [CI]=0.76–0.84), all-cancer SMR=0.80 (95% CI=0.73–0.88) and lung cancer mortality SMR=0.80 (95% CI=0.68–0.94) showed significant deficits. In the exposure sub-cohort, lung cancer mortality was not increased (SMR=0.68, 95% CI=0.44–1.00, n = 20). Time-dependent Cox analyses of the exposure sub-cohort showed no positive associations: Hazards Ratio [HR]=0.20 (95% CI=0.04–0.9) for 20 to < 50 mg/m3-years; HR=0.7 (95% CI=0.20–2.0) for 50 to <99 mg/m3-years; and HR=0.5 (95% CI=0.1–1.7) for ≥100 mg/m3-years, compared with those with < 20 mg/m3-years.
Conclusions No excess lung cancer mortality or association between lung cancer mortality and time-dependent cumulative inhalable carbon black exposure were observed. However, few lung cancer deaths occurred among the exposure sub-cohort. Nevertheless, lung cancer mortality among the older, full cohort also was not increased using duration of employment as a surrogate of cumulative carbon black exposure.