Secondhand smoking refers to exposure to someone else’s tobacco smoke. It can cause many of the same health issues that smoking causes. This might include lung cancer, coronary heart disease, and stroke.

When nonsmokers receive exposure to secondhand smoke, they can still inhale toxins present in cigarettes and other forms of tobacco. According to the Centers for Disease Control and Prevention (CDC), there are more than 7,000 chemicals in cigarette smoke, at least 70 of which researchers know cause cancer.

There is no safe level of exposure to secondhand smoke. However, the damage may be worse in people who frequently have exposure to secondhand smoke in unventilated spaces. The damage may also be worse in babies and children.

Read on to learn about the health issues that exposure to secondhand smoke can lead to and how people can limit exposure.

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Secondhand smoke damages the body’s cells, especially in the lungs, and negatively affects their ability to exchange oxygen. This can lead to short-term and long-term symptoms and increases the risk of health conditions.

Children and infants

In children, secondhand smoke exposure can increase the risk of:

Both secondhand smoke exposure and smoking while pregnant can increase the risk of sudden infant death syndrome (SIDS). Babies whose birth parent smokes are three times more likely to die from SIDS.

Secondhand smoke exposure may affect the growth and development of children of all ages. A 2020 systematic literature review found a correlation between secondhand smoke exposure and:

Heart and lung diseases

Secondhand smoke exposure can increase the risk of heart and lung diseases. For example, a 2020 study found that it increases the risk of hypertension almost as much as smoking. This then elevates the risk of heart disease, including heart attack.

Additionally, exposure to secondhand smoke can damage other organs and organ systems. A 2019 study reports that secondhand smoke exposure — especially frequent exposure — elevates the risk of developing chronic kidney disease.

Other health problems

Some other health issues that secondhand smoke may cause include:

The CDC estimates that, since 1964, secondhand smoke exposure has killed 2.5 million people who did not smoke.

A person can receive exposure to secondhand smoke anywhere people are smoking. Some examples include:

  • at home, if a household member is a smoker
  • living in a multiunit accommodation, where many houses are close together — smoke can drift in from units through stairwells, hallways, or ventilation systems
  • at work
  • riding in the car with someone who is smoking
  • visiting someone who smokes inside their home
  • being around people who smoke in a bar or restaurant

No level of secondhand smoke exposure is safe. A person in the vicinity of someone else who is smoking should get as far away from the smoke as they can. As with firsthand smoking itself, the risks of exposure to secondhand smoke are cumulative.

A person can try the following strategies to avoid or limit their exposure to secondhand smoke:

  • Encourage loved ones to quit smoking — they can also offer support when they attempt to quit.
  • Ask workplaces to implement smoke-free policies.
  • If someone smokes at home, ask them to avoid smoking when visiting.
  • Leave the immediate area if a person begins smoking, if possible.
  • Avoid riding in cars with people while they smoke.
  • If living with a roommate, partner, or others who may be smokers, ask them to smoke outside.
  • When a person cannot avoid exposure to secondhand smoke, open windows or remain as far away from the smoke as possible.

Because it can be difficult for someone to control every environment, the CDC advocates for public health policies to reduce secondhand smoke exposure. These policies include making workplaces and businesses smoke-free.

According to CDC, exposure to secondhand smoke can increase the risk of premature birth and low birth weight. Both of these increase the risk of negative outcomes in the baby.

Secondhand smoke exposure during pregnancy may increase the risk of SIDS and lead to lung health issues, such as asthma and respiratory infections, for the fetus.

Below are some common questions and answers on secondhand smoke and its effects on people:

How long does it take for secondhand smoke to affect a person?

Secondhand smoke can cause immediate effects such as coughing or burning eyes. It also damages cells and organs and can cause long-term and chronic health problems such as heart disease.

Is exposure to secondhand e-cigarette smoke harmful?

Electronic cigarettes are relatively new, and so is the research assessing their risks. Scientists have not yet identified or ruled out all the possible health risks.

That said, a 2021 study found that electronic cigarettes release many of the same toxins as nicotine smoke. This suggests that exposure might damage the airways and cause other damage similar to cigarette smoke.

What is thirdhand smoke?

Thirdhand smoke is a harmful residue that persists in the environment long after a person stops smoking a cigarette. This chemical residue settles on surfaces and is especially likely to harm children and babies who come into contact with it.

Secondhand smoke causes serious public health consequences, including worsening health and preventable deaths. It is especially harmful during pregnancy and early childhood.

There is no safe level of exposure to smoke or secondhand smoke. People can reduce their risk of secondhand smoke-related health effects by eliminating as many potential sources of exposure as possible.