Nested case-control study of tumors of the hemopoietic and lymphatic systems among workers in the meat industry.

Workers in the meat industry are exposed to viruses that cause leukemia and lymphoma in cattle and chickens, and also to carcinogenic chemical agents. This case-control study, nested in a cohort of members of a meatcutters' union in Baltimore, Maryland, investigated whether occupational exposures are associated with death from tumors of the hemopoietic and lymphatic systems. Cases of these tumors represent all deaths which occurred in the cohort between 1949 and 1980. Excess risks of tumors of the hemopoietic and lymphatic systems were observed throughout the meat industry, except in meatpacking plants. Slaughtering activities involving heavy exposure to oncogenic viruses were strongly associated with these tumors, especially with lymphomas. Thus, elevated risks were observed for butchers who killed animals (odds ratio (OR) = 5.3, 95% confidence interval (CI) 1.0-27.0); workers in chicken-slaughtering plants (OR = 3.3, 95% CI 0.8-13.1); and workers in cattle/sheep/pig abattoirs (OR = 2.8, 95% CI 0.8-9.5). Among supermarket workers, wrapping meat (mainly a female activity) was associated with increased risk of tumors of the hemopoietic and lymphatic systems (OR = 3.8, 95% CI 1.0-14.3), with the odds of both lymphomas and tumors of the myeloid stem cell being elevated. On the other hand, meatcutting in supermarkets (almost exclusively a male activity) was associated with multiple myeloma; the odds ratio for men was 18.0 (95% CI 1.6-207.5), with no myeloma cases being recorded in women. These associations persisted after limited control for exposures outside the industry that have also been observed to be associated with excess risk, such as exposure to pesticides, working/living on pig farms, and exposure to X-rays. The findings provide evidence that workers in the meat industry may be at elevated risk of tumors of the hemopoietic and lymphatic systems. Further studies with larger sample sizes are needed to identify more conclusively which exposures play an etiologic role in the occurrence of the different histologic types of these tumors.