Heart disease mortality among bridge and tunnel officers exposed to carbon monoxide

The authors investigated the effect of occupational exposure to carbon monoxide on mortality from heart disease in a retrospective study of 5,529 New York City bridge and tunnel officers employed between January 1, 1952 and February 10, 1981, at any one of nine major water crossings operated by the Triborough Bridge and Tunnel Authority of New York City. Among former tunnel officers, 61 deaths from arteriosclerotic heart disease were observed, as compared with 45 expected (standardized mortality ratio = 1.35, 90% confidence interval 1.09-1.68); expected rates were based on the New York City population. Using a proportional hazards model, the authors compared the risk of mortality from arteriosclerotic heart disease among tunnel officers with that of the less-exposed bridge officers. No association of arteriosclerotic heart disease with length of exposure was observed, but there was significant interaction of exposure with age. The elevated risk of arteriosclerotic heart disease among tunnel officers, as compared with that of bridge officers, declined after cessation of exposure, with much of the risk dissipating within as little as five years. The parallel findings of this study of occupational exposure to carbon monoxide and those studies showing the relation of cigarette smoking to cardiovascular mortality suggest that carbon monoxide may play an important role in the pathophysiology of cardiovascular mortality associated with cigarette smoking.