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Secondhand Smoke


Being exposed to tobacco smoke is bad for you, even if you’re not the one smoking.

What is Secondhand Smoke?

Secondhand smoke is smoke that is inhaled involuntarily by someone who is not smoking. Secondhand smoke is the combination of:

  1. Smoke from the burning end of a cigarette
  2. Smoke exhaled by a smoker

Every time someone lights up a cigarette, secondhand smoke gets in the air.

How Secondhand Smoke Harms

Secondhand smoke contains thousands of chemicals. More than 250 of these chemicals are known to be harmful. At least 69 of the toxic chemicals in secondhand smoke cause cancer. Nonsmokers who breathe in secondhand smoke take in nicotine and toxic chemicals by the same route smokers do.

Secondhand smoke can stay in the air for hours and even sneak through cracks in windows and doors. Breathing in secondhand smoke—even for a short time—can hurt your body. Secondhand smoke has immediate harmful effects and can cause health problems in kids, teens, and adults. Someone who is exposed to secondhand smoke for a long time can have long-term problems. Nonsmokers exposed to secondhand smoke have increased risk for:

  • Lung cancer
  • Heart disease
  • Stroke
  • Many other health issues

Secondhand smoke can even cause cancer and respiratory problems in your pets!

Protect Yourself from Secondhand Smoke

If you can smell someone smoking, you may be exposed to secondhand smoke. Most secondhand smoke exposure happens in homes, but it also occurs in restaurants, bars, cars, and other public spaces where people might smoke. You can take steps to avoid exposure:

  • Spend your time in smokefree places. Having separate smoking and nonsmoking sections in a restaurant, for example, doesn’t protect you from secondhand smoke.
  • Ask friends to not smoke if you’re in a car with them.
  • Make a plan to find a smokefree space if you’re at a party, concert, or other place where there might be smokers.

Find Out More

NCI Secondhand Smoke: Questions and Answers 
CDC Secondhand Smoke (SHS) Facts 

Take the secondhand smoke quiz.