Secondhand Smoke and Cancer Risk

Secondhand smoke is the tobacco smoke that people breathe in when they are near someone who is smoking. You do not have to smoke to be exposed to it.

This smoke is not harmless. It contains many of the same cancer-causing chemicals as the smoke a smoker breathes in. Because of this, secondhand smoke can cause lung cancer in people who have never smoked.

Secondhand smoke comes from two sources:

• The smoke that drifts off the burning end of a cigarette, cigar, or pipe
• The smoke that a smoker breathes out into the air

When these mix, they fill the air around a smoker. Anyone nearby breathes them in.

Secondhand smoke contains harmful substances such as benzene, formaldehyde, cadmium, and tobacco-specific nitrosamines. Many of them are classified as cancer-causing. These same chemicals are in the smoke a smoker breathes in.

When a nonsmoker breathes secondhand smoke, those chemicals enter their body. Secondhand smoke is known to cause lung cancer in nonsmokers.

Secondhand smoke is known to cause lung cancer in adults who do not smoke. It also increases the risk of heart disease.

You might think a little smoke here and there is harmless. But that is not what the science shows.

Experts have concluded that there is no safe level of secondhand smoke exposure. Even low levels can be harmful.

Common fixes do not work:

NCI says opening windows, using fans or ventilation systems, and limiting smoking to certain rooms or times of day does not eliminate exposure to secondhand smoke.

The only way to fully protect nonsmokers is to keep spaces completely smoke-free.

Secondhand smoke can harm anyone who breathes it. Some groups are especially vulnerable.

Secondhand smoke can cause serious health problems in children, including sudden infant death syndrome, ear infections, pneumonia, bronchitis, colds, and more severe asthma.

NCI also says exposure during pregnancy is linked to pregnancy complications and poor birth outcomes such as low birth weight and preterm delivery.

The best protection is to keep smoke out of the places you spend time.

Helpful steps include:

• Make your home completely smoke-free.
• Keep your car smoke-free.
• Avoid indoor places where smoking is allowed.
• Support smoke-free rules in shared spaces.

If someone you live with smokes, encouraging and supporting them to quit helps everyone. Quitting protects the smoker and clears the air for the whole household.

Your healthcare team can share resources and help connect a loved one with quit support.

Keeping spaces smoke-free is not only about avoiding harm. It also creates a healthier environment for everyone.

When a home or car is smoke-free:

• Children breathe cleaner air.
• People with asthma or heart conditions are better protected.

Setting a smoke-free rule can feel like a big change, but it is one of the clearest ways to protect the people you care about.