Carbon black and lung cancer: Testing a new exposure metric in a German cohort

BACKGROUND: A cohort mortality study of a large carbon black production plant in Germany showed an elevation in lung cancer mortality (SMR 1.81 (95% CI: 1.34-2.39)), although the elevation could not be linked to exposure to carbon black. METHODS: In follow up to a British study of carbon black production workers Sorahan et al., 2007] in which risk of lung cancer progressively declined after cessation of employment-in contrast to an expected upward trend-we evaluated the German cohort with a similar methodology, that is, by focusing on the first 15 years after leaving employment in terms of lung cancer SMR. RESULTS: In our SMR analysis of the German cohort of 1,528 men and an inception cohort of 1,271 men, distinctly different results from the British cohort were observed. We observed a rising trend in lung cancer SMR, in contrast to the declining SMR trend noted in the British cohort. In fact, Cox models for lung cancer mortality with attained age as the basic time variable showed negative coefficients for the full and inception cohorts. CONCLUSIONS: Our analysis of a large German cohort of carbon black workers does not support the concept of a declining risk of lung cancer following cessation of employment.