Mortality among workers at municipal waste incinerators in Rome: a retrospective cohort study

A retrospective mortality study of a cohort of 532 male subjects employed at two municipal plants for garbage recycling and incinerating has been conducted. All workers ever employed at the plants since 1962 were enrolled and followed up from January 1, 1965 to December 31, 1992. Standardized Mortality Ratios (SMRs) and 90% confidence intervals (90%CI) were calculated using regional population mortality rates. The study yielded a total of 8,585 person-years of observation. Mortality from all causes was significantly lower than expected (observed [obs] = 31; SMR = 0.71; 90%CI = 0.51-0.95). All cancer mortality was comparable with that of the general population (obs = 15; SMR = 0.95; 90%CI = 0.58-1.46). Mortality from lung cancer was reduced (obs = 3; SMR = 0.55; 90%CI = 0.15-1.42). Increased risk was found for gastric cancer (obs = 4; SMR = 2.79; 90%CI = 0.94-6.35). Analysis by latency indicated that the excess risk of gastric cancer was confined in the category with more than 10 years since first exposure. Our results for gastric and lung cancers indicate the need to further investigate the role on cancer of occupational exposure to organic dust and bacterial endotoxins in the waste management.