Some studies have found a surprisingly large risk of ischemic heart disease in nonsmokers who live with smokers. This risk appears to be out of proportion to the environmental exposure to tobacco products in smoke. Law and colleagues reviewed all available research to verify this apparently disproportionate risk and to offer explanations.

Their meta-analysis of 19 studies that met the study criteria covered 6,600 episodes of ischemic heart disease in never-smoking spouses of smokers. The relative risk of ischemic heart disease in these never-smoking spouses was 1.30. Because these families share dietary and other habits that increase the risk of heart disease, the study corrected for diet. The net effect of living with a smoker was a 23 percent increase in risk of ischemic heart disease. The authors conclude that the most plausible explanation is platelet aggregation; it is possible that the effect could be neutralized by aspirin therapy.

In a related paper, Hackshaw and colleagues reviewed evidence from 37 studies of the risk of lung cancer in nonsmoking female spouses of smokers. They calculated the excess risk of lung cancer for these women to be 24 percent, which rose to 26 percent after adjustment for bias and dietary factors. A definite dose-response effect was observed based on duration and intensity of tobacco smoke exposure. In several studies, tobacco-specific carcinogens had been identified in the blood and urine of nonsmokers who were married to smokers.

Both articles and a related editorial stress the size and consistency of the evidence that environmental tobacco exposure is a major public health problem. One estimate for the United States implicates environmental smoke in 3,000 deaths from lung cancer, up to 62,000 deaths from ischemic heart disease, up to 300,000 cases and 212 deaths from pulmonary disease in young children, and up to 2,700 sudden infant deaths every year. Health advocates are encouraged to use all available strategies to eliminate this hazard.