Mortality in a Swedish rubber tire manufacturing plant: occupational risks or an "unhealthy worker" effect?

Background: In this cohort study a classification of 12 work categories, with specified common exposures, is used to evaluate the mortality among workers in a Swedish rubber tire plant.

Methods: Mortality among the cohort members is compared with expected values from national rates. Standardized mortality ratios (SMR) were calculated for the total cohort, for sub-cohorts and with the inclusion of a latency requirement.

Results: Male workers had increased risks for total mortality, circulatory death, respiratory death, mental disorders, epilepsy, injuries/poisoning, and for alcohol-related death. Many risks were noted among workers exposed to dust, fumes, or vapor. No trend in risk with increasing duration of employment was seen.

Discussion: Some established risks for rubber workers could be related to some specified work categories. The highest risks were noted among workers having a very short duration of employment indicating a possible "unhealthy worker effect" associated with life-style factors or to tasks offered to unskilled workers.