People who don’t smoke but are exposed to secondhand tobacco smoke at home or in the workplace face a 20 percent to 30 percent higher risk of lung cancer. Approximately 7,300 people in the U.S. who don’t smoke die each year from lung cancer because of secondhand smoke.

Secondhand smoke is a mixture of tobacco smoke that is exhaled and the smoke that comes from the lit end of a cigarette, cigar, pipe, or hookah. Secondhand smoke is sometimes referred to as “environmental tobacco smoke,” and exposure to secondhand smoke is also known as “passive smoking” or “involuntary smoking.” There are more than 7,000 chemicals in secondhand smoke, and at least 70 of those chemicals are considered carcinogens (cancer-causing agents).

Lung cancer is cancer that originates in the lungs. It is the leading cause of death by cancer in the United States and throughout the world. Early-stage lung cancer may be asymptomatic. Symptoms of advanced lung cancer include:

• A persistent cough — possibly with blood
• Chest pain
• Hoarse voice
• Shortness of breath
• Unexpected weight loss

Smoking is the leading cause of lung cancer, and researchers believe it accounts for approximately 80 percent of deaths from the disease.

How Secondhand Smoke Contributes to Lung Cancer

Secondhand smoke exposes people to carcinogenic chemicals that can react with DNA and induce tumors, similarly to the effects of smoking directly (also called first-hand smoking). The smoke from the burning end of a tobacco product — known as “sidestream smoke” (as opposed to mainstream smoke that is exhaled) — is particularly harmful.

Sidestream smoke burns at a lower temperature than mainstream smoke that is inhaled, because inhalation increases burning and temperature. Lower-temperature sidestream smoke releases at least 17 chemicals at a higher density and toxicity than exhaled smoke. These chemicals damage DNA and weaken immunity, both of which can contribute to lung cancer.

How Much Secondhand Smoke Is Harmful?

According to the Centers for Disease Control and Prevention (CDC), any level of exposure to secondhand smoke carries risk. No level of exposure is risk-free. Even brief exposure to secondhand smoke can damage cells in the lungs in ways that can accelerate the development of lung cancer. Higher levels of exposure to secondhand smoke and exposure over time increase the risk of lung cancer.

Children and younger people are especially vulnerable to secondhand smoke. People aged 25 or younger who are exposed to secondhand smoke have a two-times higher risk of lung cancer compared to those exposed after age 25. Young people who are exposed to secondhand smoke also have a greater risk of cigarette smoking, which is another risk factor for lung cancer.

Secondhand smoke contributes to illness and premature death from a variety of health problems. It causes a higher risk of heart disease, stroke, and other types of cancer in adults, as well as:

• Sudden infant death syndrome (SIDS)
• Acute lower respiratory infections
• Asthma
• Ear infections in infants and children

Secondhand smoke can also harm fetuses during pregnancy.

Secondhand Smoke Among People With Lung Cancer

Secondhand smoke causes detrimental effects in people who already have lung cancer. People with non-small cell lung cancer (NSCLC), the most prevalent form of lung cancer, have worse outcomes when they are exposed to secondhand smoke.

Secondhand smoke exposure reduces the survival rate of people with NSCLC and can increase disease progression. The exposure also makes quitting smoking more difficult, which can reduce the effectiveness of treatment such as radiation therapy or chemotherapy.

Secondhand Vaping and Lung Cancer

Vaping and electronic cigarettes (e-cigarettes) emit another type of fume or vapor, an aerosol that contains numerous hazardous chemicals and tiny particles that are irritants to lungs. Vaping has been linked to lung diseases such as popcorn lung or bronchiolitis obliterans, lipoid pneumonia, and collapsed lung, all of which are serious conditions.

Because e-cigarettes are a relatively new form factor for smoking, there is not much data yet on links between vaping and lung cancer. But oncology researchers are concerned. Many e-cigarette products do not list all of the hazardous ingredients they contain, and some have been found to be modified with other potentially harmful substances.

Protection Against Secondhand Smoke

Many states have laws that forbid smoking indoors at restaurants, workplaces, and other public buildings. However, there are still numerous states without these protections. The only way to ensure protection against secondhand smoke is to avoid indoor places where smoking occurs. Exposure to secondhand smoke in restaurants that allow indoor smoking has been found to be two to six times higher than in homes or workplaces.

To protect you and your family members from secondhand smoke, it’s important to make your home and car smoke-free and only allow smoking outside. If your workplace allows smoking, you can advocate for a smoke-free environment.

Talk With Others Who Understand

MyLungCancerTeam is the social network for people with lung cancer and their loved ones. More than 5,000 members come together to ask questions, give advice, and share their stories with others who understand life with lung cancer.

Were you exposed to secondhand smoke before your lung cancer diagnosis? Share your experience in the comments below, or start a conversation by posting on MyLungCancerTeam.