ORIGINAL ARTICLE

Cancer mortality among man-made graphite electrode manufacturing workers: results of a 38 year follow up

I Mori

Department of Work Stress Control, National Institute of Industrial Health, Japan

Correspondence to:
Correspondence to:
Dr I Mori, Department of Work Stress Control, National Institute of Industrial Health, 6-21-1, Nagao, Tama-ku, Kawasaki, 214-8585 Japan;
mouri{at}niih.go.jp

Background and Aims: To examine the risk for cancer mortality among workers exposed to coal tar and coal tar pitch volatiles in a man-made graphite electrode factory. The risk for cancer mortality in this type of factory is still inconclusive, although coal tar and coal tar pitch are recognised as human carcinogens.

Methods: The study cohort consisted of 332 male employees who served more than five years in the period 1951–74. The cohort was traced until 1988. Analyses used standardised mortality ratios (SMRs) to compare cause specific mortality with that in the general and local population. Effect of smoking was estimated based on the information collected from the subgroup of the cohort. SMRs for leading causes of death were compared among different job titles, duration of employment, time since first employment, and observation subperiods. Exposure level for tar and benzo[a]pyrene (BaP) in the factory was also discussed, based on measurements done by other researchers in the past.

Results: During the study period, 52 deaths were identified (SMR 0.68), including 22 cancer deaths (SMR 1.01). The SMR for lung cancer was significantly increased in comparison with the general population (SMR 2.62). It was slightly decreased in comparison with the local population, but remained significant (SMR 2.35). Excess deaths were also observed for lymphatic and haematopoietic cancers (SMR 3.46). Smoking habits in the subgroup were similar to those in the general population; thus the increased SMR for lung cancer was unlikely to be explained by smoking.

Conclusion: Previous environmental measurements suggested that considerable exposure to tar and BaP had existed in the factory. The results suggest a possible risk for lung cancer among the cohort, but the limitations of the study, such as the small study population and insufficient information on exposure, indicate that further study is required.

Keywords: epidemiology; occupational cancer; graphite electrode manufacturing

Abbreviations: BaP, benzo[a]pyrene; CTPV, coal tar pitch volatile; PAH, polycyclic aromatic hydrocarbon; SMR, standardised mortality ratio

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