How Secondhand Smoke Raises Your Lung Cancer Risk

Medically Reviewed by Melinda Ratini, MS, DO on January 20, 2022
4 min read

If you never light up, the odds that you’ll get lung cancer go way down. But you increase your odds of getting it if you hang out around people who do smoke.

Secondhand smoke is what you breathe in when people around you smoke cigarettes, cigars, hookahs, or pipes. You may also hear it called environmental tobacco smoke.

It’s a mix of two kinds of smoke:

  • Mainstream smoke -- what other people blow out after they take a puff
  • Sidestream smoke -- smoke that drifts from a burning cigarette or cigar

When you breathe it in, it’s called passive or involuntary smoking. You take in the same toxic chemicals the smoker does, just in smaller amounts. Even if you’re in a home or workplace with an air filter or open windows, if people are smoking, you can breathe it and get sick from it.

No amount of secondhand smoke is safe. The amount from just one cigarette is enough to do you harm. A large cigar gives off about as much as an entire pack of cigarettes.

If you live with a smoker, it’s easy to breathe in their secondhand smoke. It’s especially risky if they smoke in the house.

You can also get exposed if you work in places that allow smoking, like bars, restaurants, or public transportation.

If you live in a building with lots of units, you may even breathe it in through air ducts, crawl spaces, or elevator shafts.

You can also take it in if you ride in a car with someone who’s smoking, even if the air conditioner is on or the windows are open.

More than 7,330 lung cancer deaths every year result from secondhand smoke. That means the people who died were nonsmokers.

Lung cancer is the most deadly cancer for both men and women in the U.S. Death rates have been going down over the last decade, but it still kills as many as 130,000 men and women a year.

It contains 7,000 different chemicals. Of these, hundreds are toxic. About 70 can cause cancer. They include poisons, radioactive elements, and metals:

  • Arsenic (a well-known poison)
  • Benzene
  • Beryllium
  • 1,3 Butadiene
  • Cadmium
  • Chromium
  • Ethylene oxide
  • Nickel
  • Polonium
  • Vinyl chloride
  • Formaldehyde
  • Benzo[α]pyrene
  • Toluene

When you breathe it in, the smoke and its toxic chemicals go deep into your lungs and damage the lining. Smoke irritates your airways every time you breathe it in. And it starts working as soon as you inhale.

At first, your body may be able to repair the damage. But if you’re around secondhand smoke for a long time, your body may not be able to fix it any longer. Cells in your lung tissue start to act in an abnormal way, and then they form tumors, or cancer.

The longer you’re around it, the more likely you are to get cancer. It’s hard to say exactly how much. Many things, like the mix of chemicals you breathe in and how strong they are, play a role. But if you live with a smoker, your odds for lung cancer go up 20%-30%

Lung cancer isn’t the only risk. Secondhand smoke can cause other types of cancer:

You’re also more likely to get heart disease and stroke. And if you already have asthma, it may get worse.

Babies and children who live with smokers can get childhood cancers like leukemia, lymphoma, liver cancer, and brain tumors. Secondhand smoke is also linked to sudden infant death syndrome, or SIDS, in babies. Pregnant moms exposed to secondhand smoke may have babies with low birth weight.

It’s bad for growing kids who spend a lot of time inside the house. It can slow lung development and lead to ear or lung infections. They might have breathing problems, a chronic cough, or just get sick more often than their friends.

Dogs are more likely to get lung and nasal cancer. Cats have higher chances of getting lymphoma and oral cancer. Even pet birds can also get lung cancer if someone smokes in the house.

We don’t know yet. No research has linked smoke odors to cancers in people. But we do know that cancer-causing parts from tobacco smoke will cling to dust, carpets, sofas, and clothes.

Doctors call this thirdhand smoke. It probably affects you much less than a lit cigarette or pipe, But it can lurk in your house for months. That’s a special worry for babies and toddlers, who like to put things in their mouths.

The best way is to avoid smokers. Don’t let anyone smoke in your house or car. If a houseguest wants to smoke, ask them to take it outside. Pick smoke-free restaurants, and ask for nonsmoking rooms at hotels and motels.

You can’t get rid of smoke residue in your home or car by opening windows or using fans. Clean or wash curtains, furniture fabric, rugs, walls, and counters often.

Show Sources


American Lung Association: “9 of the Worst Diseases You Can Get from Secondhand Smoke,” “Lung Cancer Fact Sheet.”

American Cancer Society: “Health Risks of Secondhand Smoke.”

National Cancer Institute: “Lung Cancer Prevention (PDQ) -- Patient Version,” “Secondhand Smoke and Cancer.”

U.S. Surgeon General and CDC: “Secondhand Smoke: what it means to you.”

CDC: “Health Effects of Secondhand Smoke,” “Secondhand Smoke (SHS) Facts.”

Mayo Clinic: “How risky is secondhand smoke?” “Lung Cancer: Causes,” “What is thirdhand smoke, and why is it a concern?”

The Lancet Oncology: “Second-hand smoke and human lung cancer.”

Department of Health and Human Services: “The Health Consequences of Involuntary Exposure to Tobacco Smoke: A Report of the Surgeon General.”

Environmental Protection Agency: “Secondhand Tobacco Smoke and Smoke-Free Homes.”

International Journal of Environmental Research and Public Health: “Sex and Age Differences in Exposure to Secondhand Smoke at Home among Korean Adolescents: A Nationally Representative Survey.”

Americans for Nonsmokers’ Rights: “Tobacco, Secondhand Smoke, and Pets.”

Tobacco Control: “When smokers quit: exposure to nicotine and carcinogens persists from thirdhand smoke pollution.”

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