Risk factors of tumors of the hemopoietic and lymphatic systems among workers in the meat industry
Description
Findings from a cohort mortality study between 1949-1980 of 28,900 members of a meatcutter's union in Baltimore, Maryland, suggested that certain workers in the meat industry have an excess risk of death from tumors of the hemopoietic/lymphatic systems (HLS). The aim of the present case-control study, nested in the Baltimore cohort study, was to investigate whether any job-categories and related tasks are associated with an excess of death from tumors of the HLS, taking into account length of exposure, as well as potential confounding factors in the assessment of risk While the cohort study was being concluded, all subjects who died from tumors of the HLS in Maryland were identified, and their next-of-kin interviewed by telephone to provide detailed information on history of occupation, lifestyle, diet, medical conditions, use of medications, leisure, etc. Controls were randomly selected from deceased members who had never been diagnosed with cancer of the HLS. Inclusion of controls was restricted to those who had lived at least as long as an assigned case. Additional data from the employment records of the Union and medical charts were used to validate occupational exposures and the cause of death Consistent results were obtained with (1) different statistical approaches viz. unmatched analyses with one control per case (n = 106) or two controls per case (n = 159) and matched analysis with one control per case; and (2) different sources of information including data from the interviews of the next-of-kin and limited data from the Union's records. The main findings are as follows: (1) Increased risks of all tumors of the HLS were observed among workers in the meat industry in general, and in abattoirs, grocery stores/supermarkets, and chicken-slaughtering plants specifically. Workers in meatpacking plants were at decreased risk. (2) Meat-related tasks with high exposure to oncogenic viruses such as butcher, work in kill/dress areas involving slaughtering activities were highly associated with tumors of the HLS. (3) The positive associations between job-categories and specific occupational tasks and tumors of the HLS remained stable after controlling for exposure to pesticides, working/living on pig farms, and exposure to X-rays. (4) The excess risks of tumors of the HLS seen throughout the meat industry, except in meatpacking plants, were mostly due to lymphomas. In supermarkets, myeloid tumors and multiple myeloma also contributed to the excess risk. There was a suggestion also of an increased risk of myeloid leukemia in abattoirs. (5) There was no sex-related difference in the risk of developing all tumors of the HLS in the meat industry in general and within each job-category, except for supermarket workers. In this department, lymphomas and leukemias were predominant in females who are exclusively engaged in wrapping, while multiple myeloma was over-represented in men. (6) The observed risks generally increased for long duration of employment in abattoirs and chicken-slaughtering plants, except in grocery stores/supermarkets where an inverse dose-response relationship, or lack of it was observed. (Abstract shortened by UMI.)