Cancer Incidence among Laboratory Workers in Biomedical Research and Routine Laboratories in Israel: Part II - Nested Case-Control Study

Background: A case-control study nested within a cohort study of biomedical laboratory workers was conducted to examine whether the excess cancer morbidity that we found can be explained by exposure to a particular group of substances, taking into consideration potential confounders. Methods: The study population included 163 cases and two matched control groups: laboratory workers (311) and general population (448) workers. Results: Multiple conditional regression analysis showed that working in research laboratories involved an increased risk of cancer generally among women [risk ratio 2.2 (1.2-4.3)], and of breast cancer particularly [risk ratio 2.3 (1.1-4.7). Seventy-six percent (76%) of breast, 87% of thyroid, 60% of ovary and prostate, 94% of melanoma, and 50% of leukemia cases were ever exposed to at least one known human carcinogen. Conclusion: Our results exclude the possibility that the excess cancer morbidity was related to personal risk factors but they may be explained by exposure factors.