A "Lugged" analysis of lung cancer risks in UK carbon black production workers 1951-2004

BACKGROUND: Previously published analyses of excess lung cancer risks in UK carbon black production workers attracted no confident interpretation. METHODS: The mortality of a cohort of 1,147 male manual workers from five UK factories manufacturing carbon black was investigated for the period 1951-2004. All subjects were first employed in the period 1947-74 and were employed for 12 months or more. Limited work histories were available to calculate estimates of individual cumulative exposure to carbon black. RESULTS: Based on serial rates for the general population of England and Wales, significantly elevated mortality was observed for lung cancer (Obs 67, SMR 146, P <0.01) but not for all other causes combined (Obs 426, SMR 106). There was highly elevated lung cancer mortality at two of the plants (SMR 230, Obs 35) but no excess mortality at the other three plants combined (SMR 104, Obs 32). Analyses by period since leaving employment indicated elevated lung cancer risks were limited to those workers with some employment in the most recent 15 years. SMR analyses found an overall positive significant trend between lung cancer risks and cumulative carbon black exposure received in the most recent 15 years. Poisson regression analyses provided different results depending on which variables were adjusted for. CONCLUSIONS: The findings suggest that carbon black, or chemicals associated with the production of carbon black, had an effect on later stages of lung cancer carcinogenesis at two of the plants but that no such effect was found at the other plants.