Why Secondhand Smoke Is Dangerous

First published 2007. To view the latest Heads Up content, click here.


More than 126 million nonsmoking Americans are regularly exposed to secondhand smoke—at home, at work, and in indoor public spaces. Secondhand smoke is the smoke from the burning end of a cigarette and the smoke breathed out by smokers. Cigarette smoke contains thousands of dangerous chemicals that endanger the health of smokers and nonsmokers.

The U.S. Surgeon General’s report on secondhand smoke warned in 2006, “There is no risk-free level of exposure to secondhand smoke.” A research project highlighted in the Surgeon General’s report was conducted in 2001 by Dr. Ryo Otsuka and other scientists in Osaka, Japan. They looked at what happened to healthy young adults, both smokers and nonsmokers, who were exposed to secondhand smoke for 30 minutes. The researchers measured changes in blood flow through the subjects’ hearts before and after they spent 30 minutes in a hospital smoking lounge.

The researchers found that even a brief 30-minute exposure to secondhand smoke had a harmful effect on the blood vessels of the nonsmokers. Blood vessels are lined by a cell layer known as the endothelium. The endothelium plays a critical role in controlling blood flow. In nonsmokers the effects of 30 minutes of exposure to secondhand smoke significantly reduced the velocity of blood flow to the heart. In smokers, the blood flow velocity was already low and did not change significantly.

Based on this study and on other research, the 2006 Surgeon General’s report described smoking as “the single greatest avoidable cause of disease and death.” Major conclusions of the report included:

  • Many millions of Americans, both children and adults, are still exposed to secondhand smoke in their homes and workplaces despite substantial progress in tobacco control.
  • Secondhand smoke exposure causes disease and premature death in children and adults who do not smoke.
  • Children exposed to secondhand smoke are at an increased risk for sudden infant death syndrome (SIDS), acute respiratory infections, ear problems, and more severe asthma. Smoking by parents causes respiratory symptoms and slows lung growth in their children.
  • Exposure of adults to secondhand smoke has immediate adverse effects on the cardiovascular system and causes coronary heart disease and lung cancer.
  • The scientific evidence indicates that there is no risk-free level of exposure to secondhand smoke.
  • Eliminating smoking in indoor spaces fully protects nonsmokers from exposure to secondhand smoke. Separating smokers from nonsmokers, cleaning the air, and ventilating buildings cannot eliminate exposures of nonsmokers to secondhand smoke.

Learn more about the deadly effects of tobacco addiction.

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U.S. Department of Health and Human Services, The Health Consequences of Involuntary Exposure to Tobacco Smoke: A Report of the Surgeon General, 2006, Chapter 2. Accessed at www.surgeongeneral.gov/library/secondhandsmoke/report/chapter2.pdf

U.S. Department of Health and Human Services, “Six Major Conclusions of the Surgeon General Report,” The Health Consequences of Involuntary Exposure to Tobacco Smoke: A Report of the Surgeon General, 2006. Accessed at www.surgeongeneral.gov/library/secondhandsmoke/factsheets/factsheet6.html.

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