Cohort Study of Carbon Black Exposure and Risk of Malignant and Nonmalignant Respiratory Disease Mortality in the US Carbon Black Industry

OBJECTIVE To evaluate lung cancer and respiratory disease mortality associations with cumulative inhalable carbon black exposure among 6634 US carbon black workers. METHODS This analysis was performed using standardized mortality ratio (SMRs) and Cox regression analyses. RESULTS Lung cancer mortality was decreased overall (SMR = 0.77; 95% confidence interval [CI], 0.67 to 0.89) but less so among hourly male workers (SMR = 0.87; 95% CI, 0.71 to 1.05). No exposure-response association was observed with time-dependent cumulative inhalable carbon black: hazard ratio [HR] = 1.0 (95% CI, 0.6 to 1.6) for 20 to less than 50 mg/m·yr); HR = 1.3 (95% CI, 0.8 to 2.1) for 50 to less than 100 mg/m·yr; and HR = 1.4 (95% CI, 0.9 to 2.1) for 100 mg/m·yr or more compared with referent (<20 mg/m·yr). No consistent associations were observed between cumulative inhalable carbon black exposure and respiratory disease mortality. CONCLUSION Quantitative carbon black exposure estimates were not related to lung cancer or nonmalignant respiratory disease mortality.