Carbon monoxide hazard in city traffic. An examination of traffic policemen in three Swedish towns.

The hazard of carbon monoxide (CO) exposure in dense traffic was examined in policemen by analysis of the carboxyhemoglobin (COHb) in blood, after they had controlled the traffic during rush hours. The mean COHb levels in smokers were from three to five times higher than in nonsmokers who had a normal, or only slightly increased, COHb concentration in blood. The COHb in smokers tended to decrease when their hours of traffic duty increased. Since the increase of COHb, due to smoking, conceals the effect exerted on COHb by exposure to air in crowded city streets, the biologically significant CO exposure, due to urban air pollution, ought to be evaluated on the basis of the COHb levels in nonsmokers.