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Secondhand Smoke
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Poisoning Toxicology Environmental Health

Secondhand Smoke

Secondhand smoke is a dangerous mixture of chemicals that poses serious health risks to nonsmokers, with no safe level of exposure.

What is secondhand smoke?

Secondhand smoke is a mixture of the smoke from the burning end of a cigarette, cigar, or pipe, and the smoke exhaled by the smoker. It contains more than 7,000 chemicals, hundreds of which are toxic, and approximately 70 are known to cause cancer.

Health effects

Exposure to secondhand smoke is linked to several health issues, including:

  • Ear infections in children.
  • More frequent and severe asthma attacks in children.
  • Heart disease and lung cancer in adults who have never smoked.

Prevention

There is no safe amount of secondhand smoke; even low levels can be harmful. The only way to fully protect nonsmokers is to prohibit smoking indoors.

Frequently Asked Questions

No, smoking outdoors does not completely eliminate the risk. Chemicals from tobacco smoke can cling to a smoker's hair, skin, clothing, and belongings, and then be carried indoors. This is known as "thirdhand smoke" and can expose others, especially children, to harmful toxins. The only way to fully protect nonsmokers is to ensure no smoking occurs indoors.
Children are particularly vulnerable to secondhand smoke. Exposure significantly increases their risk of developing ear infections and experiencing more frequent and severe asthma attacks. It can also contribute to respiratory infections, sudden infant death syndrome (SIDS), and slower lung growth.
The most effective way to protect your family is to establish a smoke-free home and car policy, meaning no one smokes anywhere inside your living spaces or vehicles. Encourage smokers to quit, and avoid places where smoking is permitted. If you cannot avoid a smoky environment, try to minimize exposure time and ensure good ventilation.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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