FOLLOW-UP-STUDY OF CHRYSOTILE ASBESTOS TEXTILE WORKERS - COHORT MORTALITY AND CASE-CONTROL ANALYSES

Previous studies of mortality among white males employed in a Charlest on, South Carolina asbestos textile plant using chrysotile demonstrate d significant excess mortality due to asbestos-related disease and a s teep exposure-response relationship for lung cancer. This cohort was f urther studied by adding 15 years of follow-up and including mortality among white female and black male workers. Nested case-control analys es were undertaken to further explore possible differences in lung can cer risk by textile operation as well as possible confounding by miner al oil exposures. Preliminary data for white males have been previousl y published. White males experienced statistically significant excess mortality due to lung cancer (standardized mortality ratio [SMR] = 2.3 0; confidence interval [CI] = 1.88-2.79), all causes (SMR = 1.48; CI = 1.38-1.58), all cancers (SMR = 1.50; CI = 1.29-1.72), diabetes mellit us (SMR = 2.05; CI = 1.18-3.33), heart disease (SMR = 1.41; CI = 1.26- 1.58), cerebrovascular disease (SMR = 1.50; CI = 1.08-2.02), pneumocon iosis and other respiratory diseases (SMR = 4.10; CI = 3.10-5.31), and accidents (SMR = 1.49; CI = 1.15-1.91). Among white females, statisti cally significant excesses occurred for lung cancer (SMR = 2.75; CI = 2.06-3.61), all causes (SMR = 1.21; CI = 1.11-1.32), pneumoconiosis an d other respiratory diseases (SMR = 2.40; CI = 1.53-3.60), and other r espiratory cancers (SMR = 14.98; CI = 4.08-38.7). Among the total coho rt of black males, the only statistically significant excess observed was for pneumoconiosis (SMR = 2.19; CI = 1.23-3.62). Based on historic al exposure measurements at the plant, there was a postive exposure-re sponse relationship for both lung cancer and pneumoconiosis. Data for the entire cohort demonstrate an increase in the lung cancer relative risk of 2-3% for each fiber/cc-year of cumulative chrysotile exposure. This relationship was more consistent for the white male workers. The excess risk for lung cancer among white males and females appeared to occur at cumulative exposures lower than those for black males. Possi ble reasons for the lesser lung cancer risk among black male include l ess smoking and differences in airborne fiber characteristics experien ced by black males as a result of plant job placement patterns. The ca se-control analysis found employment in preparation and carding operat ions (where most of the black males worked) to be associated with a sl ightly reduced lung cancer risk, although not statistically significan t, whereas spinning and twisting employment was associated with a stat istically significant increased lung cancer risk compared to other pla nt operations. Airborne fiber size data, determined by transmission el ectron microscopy, demonstrated slightly longer fibers in spinning and twisting compared to other textile operations. Case-control analyses demonstrated little effect of mineral oil exposures on the lung cancer exposure-response estimates. Two deaths due to mesothelioma were obse rved among this cohort. (C) 1994 Wiley-Liss, Inc.