A cohort mortality study of U.K. 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 Health and Safety Executive initiated a cohort mortality study on possible carcinogenic 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 1951-1996. All subjects were employed in the carbon black industry for 12 months or more, and all were first employed before 1975. Limited work histories were used to calculate estimates of individual cumulative exposure to carbon black, using a job-exposure matrix derived by the study team.


RESULTS
Based on serial rates for the general population of England and Wales, 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 cancer SMRs at two of the factories, and unexceptional SMRs at the remaining three factories. There was no indication of lung cancer SMRs increasing with period from first employment. Poisson regression analyses failed to find significant trends of lung cancer risks increasing either with cumulative exposure to carbon black (4 levels) or with duration of employment at the participating factories (4 levels).


CONCLUSIONS
Confident interpretation of the elevated SMRs found for lung cancer in two of the factory subcohorts is not possible but the study has been unable to link cumulative exposure to carbon black with elevated risks of lung cancer.
Sorahan
T
T
Institute of Occupational Health, University of Birmingham, Edgbaston, Birmingham, UK. t.m.sorahan@bham.ac.uk
Hamilton
L
L
van Tongeren
M
M
Gardiner
K
K
Harrington
J M
JM
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000393:Air Pollutants / Q000009:adverse effects*; D002244:Carbon / Q000009:adverse effects*; D015331:Cohort Studies; D004305:Dose-Response Relationship, Drug; D004739:England / Q000453:epidemiology; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000401:mortality; D008297:Male; D008875:Middle Aged; D009026:Mortality; D016273:Occupational Exposure / Q000009:adverse effects*; D009790:Occupations; D012140:Respiratory Tract Diseases / Q000401:mortality; D012189:Retrospective Studies; D012306:Risk; D012606:Scotland / Q000453:epidemiology; D013997:Time Factors; D014852:Wales / Q000453:epidemiology
D000393:Air Pollutants; D002244:Carbon