Mortality of urban transit workers: indications of an excess of deaths by suicide using gas.

Urban bus drivers are exposed to a variety of discomforts and physical hazards associated with their occupation. We obtained death certificates for 99 per cent of 219 decreased members of the Amalgamated Transit Union Local 596 of Edmonton, Alberta, and conducted a proportionate mortality study against the distribution of all deaths among men in the province of Alberta, standardized by age and year of death. We found a highly significant excess from undetermined accidents due to gas (proportionate mortality ratio (PMR) 3761, based on 3 cases; p less than 0.003), which may bear a relationship to an elevation observed for suicide due to gas, which failed to achieve statistical significance (PMR 242, based on 2 cases). Collateral evidence suggests that this excess may include misclassification of some suicides. Gas inhalation as an instrument of suicide may be suggested by familiarity with vehicle exhaust. No other excess achieved statistical significance. Several causes of death showed elevated PMRs of relatively modest magnitude; elevations in PMR for lung cancer (PMR 154) and chronic obstructive pulmonary disease (PMR 176) suggest a mutual association with smoking.