A cohort study of cancer mortality among Biology Research Laboratory workers in The Netherlands

Abstract

Objective: To examine cancer mortality among persons employed in biology research institutes.

Method: A historical cohort study was undertaken in the Netherlands. The cohort, comprising 7307 laboratory workers employed by the four participating institutes between 1960 and 1992, was followed for mortality from 1960 to 1995 (median follow-up time 16.5 years). Causes of death were obtained for 98% of all deaths. Cancer mortality in the cohort was compared with that in the general population by computation of the standardized mortality ratio (SMR). The Cox proportional hazards model was used to compare cancer mortality among laboratory workers with that in an internal reference population consisting of unexposed research personnel (n = 2,404).

Results: All-cause mortality among laboratory workers was significantly lower than that in the general population. Total cancer mortality and lung cancer mortality were also significantly decreased (SMR = 0.8; 95% confidence interval CI = 0.7-0.9 and SMR = 0.7; 95% CI = 0.6-0.9), respectively. However, when compared to the internal reference population, laboratory workers had a slightly increased cancer mortality (relative risk (RR) = 1.3 95% CI = 0.9-1.9). Among men, a 2.5-fold (95% CI = 1.0-6.3) increase of lung cancer mortality was observed which could not be explained by differences in smoking habits. Lung cancer mortality increased with longer follow-up. Results with regard to a priori defined fields of research showed significantly increased cancer mortality (in particular from lung cancer) for men working in genetics (RR = 3.8), virology (RR = 4.1) and plant physiology (RR = 2.1).

Conclusion: Laboratory workers have a favorable cancer mortality pattern as compared to the general population. However, this favorable pattern disappears when a comparison is made with a control group of unexposed research personnel. The excess lung cancer mortality among male laboratory workers was concentrated in certain fields of research, which warrants further research to identify specific exposures related to the increased risk.