Secondhand Smoke

Secondhand smoke is what you inhale accidentally (called passive smoking) when you are near sources of tobacco smoke. For example, at parties or public gatherings, you might mingle with people who smoke. You may not feel any changes, but breathing secondhand smoke can affect your health.

What is secondhand smoke?

Secondhand smoke is smoke you don’t mean to breathe in. Exposure to secondhand smoke comes from burning tobacco products such as cigarettes, cigars or pipes.

Secondhand smoke is a mix of smoke that comes from the burning tip of a tobacco product and the smoke a person breathes out from the burning tobacco product. Just because you aren’t the person smoking doesn’t mean you’re safe from the harm of tobacco products. Secondhand smoke causes over 7,000 lung cancer deaths and over 33,000 heart disease deaths each year in the United States.

Secondhand smoke is also called:

  • Passive smoking.
  • Environmental smoking.
  • Involuntary smoking.


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How harmful is secondhand smoke?

Smoke from burning tobacco products contains harmful chemicals (toxins). Even if you don’t smoke, inhaling other people’s smoke causes you to breathe in these toxins. Smoke from the end of a burning cigarette, cigar or pipe is unfiltered. It may have even more harmful toxins than tobacco smoke that someone breathes out. There are over 7,000 chemicals in tobacco smoke. About 69 of these chemicals are known to cause cancer (carcinogens). About 250 of the chemicals are known to be harmful to your health.

Some of the harmful chemicals in tobacco smoke you may recognize include:

  • Benzene: A chemical in gasoline.
  • Butane: A chemical in lighter fluid.
  • Ammonia: A chemical in household cleaning products.
  • Toluene: A chemical found in paint thinner.
  • Cadmium: A chemical in batteries.
  • Formaldehyde: A chemical found in fertilizer, embalming fluid and building materials.

Is secondhand smoke worse than smoking?

Smoking is worse for your health than secondhand smoke. But, secondhand smoke is also very harmful. People who breathe in secondhand smoke are still affected by the chemicals in the smoke.

What are the effects of secondhand smoke?

The side effects of secondhand smoke can be hazardous to both adults and children. The health impacts range from increased risk of lung cancer and heart disease to more frequent ear infections.

Secondhand smoke and adults

Secondhand smoke damages your body in many different ways. Adults exposed to secondhand smoke may experience:

Studies show that you’re up to 30% more likely to develop heart disease if you’re exposed to secondhand smoke regularly.

Secondhand smoke and children

Children and infants are at an increased risk for health problems due to secondhand smoke because their bodies are still developing. They may be more likely to experience:

Because of these potential dangers, the best thing you can do for your children, family and other loved ones is to quit smoking. Ask your healthcare provider for their recommendations on how to best quit.


How long can you be exposed to secondhand smoke?

There’s no such thing as safe exposure to secondhand smoke. Studies have shown that damage from secondhand smoke occurs in as little as five minutes and inflammatory and respiratory responses occur almost immediately:

  • After five minutes: Arteries become less flexible, just like they do in a person who’s smoking a cigarette.
  • After 20-30 minutes: Blood starts clotting, and fat deposits in blood vessels increase your risk of heart attack and stroke.
  • After two hours: An irregular heartbeat (arrhythmia) can develop and trigger a heart attack or other serious cardiac problems.

How long does secondhand smoke stay in a room?

Secondhand smoke can linger in a room for up to about five hours. In fact, it can even travel through stairwells and ventilation units. This means people who live in apartment buildings risk exposure without ever leaving their home. Particles from tobacco smoke can settle on surfaces and last several months. This is called thirdhand smoke.


Who is most at risk of damage from secondhand smoke?

Secondhand smoke affects anyone near burned or exhaled tobacco, but some groups are more at risk for damage:

  • Service industry workers (like restaurant servers and bartenders): Anyone who works in public smoking areas may be unable to avoid secondhand smoke.
  • Infants, children and pets: Young children and animals can’t always choose to leave a smoke-filled room. The constant exposure increases the harmful effects of secondhand smoke.
  • Pregnant people: Secondhand smoke affects a fetus because it makes less oxygen available. It can increase fetal heart rates and cause low birth weight or premature birth.

Can you get cancer from secondhand smoke?

Yes, it’s possible for secondhand smoke to cause cancer. According to the Centers for Disease Control (CDC), secondhand smoke causes more than 7,300 lung cancer deaths each year among U.S. adults who don’t smoke.

How can you protect yourself from secondhand smoke?

The best way to avoid exposure is to stay away from areas where people smoke. This means avoiding venues and spaces where people are allowed to smoke.

Open windows and air filters don’t remove all secondhand smoke. But they may help a little by lowering some of the toxins found in burning tobacco. It’s OK to ask people not to smoke in your car or in your home.

Other ways you can protect yourself from secondhand smoke include:

  • Moving away from the smoke and finding a smoke-free place to stand or sit.
  • Visiting venues or areas where smoking is prohibited.
  • Making sure guests to your home know they can’t smoke.
  • Not letting passengers smoke in your car (even with the windows down).

The number of people who smoke tobacco products has consistently gone down over the last several decades; however, one survey found that 1 in 4 people who don’t smoke say they still breathe in secondhand smoke. Remember, the only way to completely protect yourself is to stay far away from people who are smoking.

What is the outlook for people exposed to secondhand smoke?

Regular exposure to secondhand smoke can damage your heart and lungs. The best way to stay healthy is to avoid secondhand smoke. Luckily, many cities and several states now ban smoking in public places due to being more aware of its dangers. These bans lower but don’t completely remove your risk for secondhand smoke exposure.

When should I see a healthcare provider?

You may want to visit your healthcare provider if you inhale secondhand smoke regularly. You can ask about secondhand smoke dangers and ways to stay healthy. If you develop heart disease or breathing problems because of constant secondhand smoke exposure, talk to your provider about management options.

Your healthcare provider may treat specific symptoms or diseases caused by secondhand smoke exposure. For example, you may need medications to manage high blood pressure or inhalers to treat asthma or COPD.

A note from Cleveland Clinic

While it’s not quite as harmful as smoking, breathing in secondhand smoke can impact your health. Understanding the dangers of secondhand smoke can help you protect yourself and others. Often, secondhand smoke exposure happens because someone you know smokes tobacco products. If this is the case, suggest they quit smoking for their health and yours. There are many resources available to help you (or a loved one) quit smoking.

Medically Reviewed

Last reviewed on 01/18/2024.

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