MORTALITY OF WORKERS EXPOSED TO METHYLENE-CHLORIDE EMPLOYED AT A PLANT PRODUCING CELLULOSE TRIACETATE FILM BASE

Objective-To study mortality among 1785 employees of a factory that pr oduced cellulose triacetate film base at Brantham in the United Kingdo m. Also, to investigate patterns of mortality after exposure to methyl ene chloride; in particular, mortality from liver and biliary tract ca ncer, lung cancer, pancreatic cancer, and cardiovascular disease. Subj ects and methods-All male employees with a record of employment at the film factory in 1946-88. A total of 1473 subjects worked in jobs that entailed exposure to methylene chloride. The mean duration of exposur e was nine years at 19 ppm (eight hour time weighted average). Results -In the cohort, 334 deaths were identified up to 31 December 1994. Mor talities for the cohort were compared with national and local rates an d expressed as standardised mortality ratios (SMR). In the subcohort o f workers exposed to methylene chloride, substantially reduced mortali ties compared with national and local rates were found for all causes, all cancers, and the principal cancer sites of interest. The signific antly reduced lung cancer mortalities in exposed workers (SMR 48) seem ed to reflect the restrictions on smoking at the workplace. In contras t, mortality from ischaemic heart disease in exposed workers, although lower than national rates (SMR 92), was slightly increased compared w ith local rates. However, mortality from ischaemic heart disease was l ower in active employees (SMR 83) where a direct effect of exposure to methylene chloride should be concentrated. No in service mortality du e to ischaemic heart disease was found in workers with the highest cum ulative exposure (greater than or equal to 800 ppm-years). Conclusions -The study provided no indication that employment at the plant, or exp osure to methylene chloride, had adversely affected the mortalities of workers.