Secondhand smoke can be as harmful as actually smoking a cigarette. Even when you think you are protecting yourself from secondhand smoke, you can be affected in many different ways.
Glantz, S.A. & Parmley, W., Passive Smoking and Heart Disease: Epidemiology, Physiology, and Biochemistry, (1991) 1-12. Taylor, A., Johnson, D. & Kazemi, H., Environmental Tobacco Smoke and Cardiovascular Disease, ( 1992) pp. 699-702.
U.S. Department of Health and Human Services, The Health Consequences of Involuntary Exposure to Tobacco Smoke: A Report of the Surgeon General, (2006).