Psychological functions of urban busdrivers exposed to exhaust gases: A cross sectional study of urban busdrivers in Denmark

Busdrivers are assumed to be exposed to air pollutants in the exhaust gases from other vehicles via the defroster system of the buses. A cross sectional study using questionnaires and psychological tests was conducted on 171 urban busdrivers from the three largest cities in Denmark (Copenhagen, Aarhus, and Odense). A group of 47 commuter train drivers, assumed to be exposed to air pollutants no more than the average citizen, was studied as referents. The air of the busdrivers' breathing zone was analysed for its content of toxic agents. The hygienic effect in the winter season was found to be 0.63 and in the summer season 0.36. The year mean hygienic effect was found to be 0.42. Neurastenic complaints such as difficulties of concentration, verbal retrieval, and tiredness were significantly more frequent among the busdrivers, particularly in the Copenhagen group. On psychological tests of verbal and spatial learning, retrieval and memory, psychomotor functions, visual perception, and vigilance, the Copenhagen busdrivers compared to the reference group only showed significant dysfunctions of verbal learning and long-term memory. The bus-drivers from the two smaller cities did not differ significantly from the reference group. It is suggested that the subjective complaints are due to psychosocial stressors in the busdrivers' condition of work, whereas the few differences in psychological test results may indicate a subclinical effect caused by the presence of neurotoxic agents in the busdrivers' working environment.