Secondhand smoke causes acute respiratory effects.

• Secondhand smoke contains many chemicals that can quickly irritate and damage the lining of the airways.
• Even brief exposure can trigger respiratory symptoms, including cough, phlegm, wheezing, and breathlessness.
• Brief exposure to secondhand smoke can trigger an asthma attack in children with asthma.
• Persons who already have asthma or other respiratory conditions are at especially high risk for being affected by secondhand smoke, and should take special precautions to avoid secondhand smoke exposure.

Secondhand smoke can cause sudden infant death syndrome and other health consequences in infants and children.

• Smoking by women during pregnancy has been known for some time to cause SIDS.
• Infants who are exposed to secondhand smoke after birth are also at greater risk of SIDS.
• Children exposed to secondhand smoke are also at an increased risk for acute respiratory infections, ear problems, and more severe asthma. Smoking by parents causes respiratory symptoms and slows lung growth in their children.

Separating smokers from nonsmokers, cleaning the air, and ventilating buildings cannot eliminate secondhand smoke exposure.

• The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), the preeminent U.S. standard-setting body on ventilation issues, has concluded that ventilation technology cannot be relied on to completely control health risks from secondhand smoke exposure.
• Conventional air cleaning systems can remove large particles, but not the smaller particles or the gases found in secondhand smoke.
• Operation of a heating, ventilating, and air conditioning system can distribute secondhand smoke throughout a building.

What Is Secondhand Smoke?

• Secondhand smoke is composed of sidestream smoke (the smoke released from the burning end of a cigarette) and exhaled mainstream smoke (the smoke exhaled by the smoker).
  
  
• While secondhand smoke has been referred to as environmental tobacco smoke (ETS) in the past, the term “secondhand” smoke better captures the involuntary nature of the exposure.
  
  
• The 2006 Surgeon General’s report uses the term “involuntary” in the title because most nonsmokers do not want to breathe tobacco smoke. The term “involuntary” was also used in the title of the 1986 Surgeon General’s report on secondhand smoke.
  
  
• Cigarette smoke contains more than 4,000 chemical compounds.
  
  
  • Secondhand smoke contains many of the same chemicals that are present in the smoke inhaled by smokers.
  • Because sidestream smoke is generated at lower temperatures and under different conditions than mainstream smoke, it contains higher concentrations of many of the toxins found in cigarette smoke.
  
  
• The National Toxicology Program estimates that at least 250 chemicals in secondhand smoke are known to be toxic or carcinogenic.
  
  
• Secondhand smoke has been designated as a known human carcinogen (cancer-causing agent) by the U.S. Environmental Protection Agency, the National Toxicology Program, and the International Agency for Research on Cancer, and an occupational carcinogen by the National Institute for Occupational Safety and Health.
  
  
  • Secondhand smoke contains more than 50 cancer-causing chemicals.
  • When nonsmokers are exposed to secondhand smoke, they inhale many of the same cancer-causing chemicals that smokers inhale.

The Surgeon General has concluded that:

• There is no risk-free level of exposure to secondhand smoke: even small amounts of secondhand smoke exposure can be harmful to people’s health.
• Many millions of Americans continue to be exposed to secondhand smoke.
• A smoke-free environment is the only way to fully protect nonsmokers from the dangers of secondhand smoke. Separating smokers from nonsmokers, cleaning the air, and ventilating buildings cannot eliminate exposure of nonsmokers to secondhand smoke.