A cohort mortality study of UK carbon black workers, 1951-1996

Background Carbon black, a powdered form of elemental carbon is used in the manufacture of rubber products, paints, plastics, and inks. In 1974, the H ealth and Safety Executive initiated a cohort mortality study on possible c arcinogenic effects on carbon black workers. Methods The mortality of a cohort of 1,147 male manual workers from five U. K. factories manufacturing carbon black was investigated for the period 195 1-1996. All subjects were employed in the carbon black industry for 12 mont hs or more, and all were first employed before 1975. Limited work histories were used to calculate estimates of individual cumulative exposure to carb on black, using a job-exposure matrix derived by the study team. Results Based on serial rates for the general population of England and Wal es, significantly elevated mortality was observed in the main study cohort for all causes (Obs 372, Exp 328.7 SMR 113, P < 0.05) and for lung cancer ( Obs 61, Exp 35.3, SMR 173, P < 0.001). There were highly elevated lung canc er SMRs at two of the factories, and unexceptional SMRs at the remaining th ree factories. There was no indication of lung cancer SMRs increasing with period from first employment. Poisson regression analyses failed to find si gnificant trends of lung cancer risks increasing either with cumulative exp osure to carbon black (4 levels) or with duration of employment at the part icipating factories (4 levels). Conclusions Confident interpretation of the elevated SMRs found for lung ca ncer in two of the factory subcohorts is nor possible but the study has bee n unable to link cumulative exposure to carbon black with elevated risks of lung cancel: Am. J. Ind. Med. 39.158-170, 2001. (C) 2001 Wiley-Liss, Inc.