SURVIVAL IN COHORTS OF ASBESTOS-CEMENT WORKERS AND CONTROLS

Objectives-To measure the impact on survival of being exposed to asbes tos cement dust. Methods-Survival of 866 asbestos cement workers and 7 55 controls was studied with Cox's proportional hazards regression mod els with age as the basic time variable. The effect of cumulative expo sure up to the age of 40 was investigated in an internal analysis of 6 35 asbestos cement workers who had dose estimates. Results-The death r isk was higher for the asbestos cement workers than for the controls w ith a hazard ratio (HR) of 1 . 15 (95% confidence intervalwas 1 . 00 t o 1 . 31). The increased risk found seemed to be confined to the perio d 20-40 years from start of employment. The estimates of the cohort ef fect were almost unaffected by adjustment for smoking habits. The esti mates of the exposure effect rose with increasing dose (< 4 fibre-year s/ml (f-y/ml): HR = 1 . 00, 4-9 . 9 f-y/ml: HR = 1 . 06, greater than or equal to 10 f-y/ml: HR = 1 . 35, for workers with at least five yea rs of employment), and were higher when restricted only to deaths from malignant or nonmalignant respiratory disease. However, none of the p oint estimates were significantly increased. Median age at death was t wo years lower in the high than in the low, exposure group. Conclusion s-The results indicate that even a moderate asbestos exposure may shor ten the median duration oflife in an exposed population. Compared with the estimated effect on duration oflife from ever being a smoker, tha t of ever being an asbestos cement worker was less, although that of h aving a high exposure was similar.