- Secondhand smoke is a smoker's exhaled smoke plus the smoke from that person's lit cigarette, cigar, or pipe.
- Secondhand smoke contains thousands of chemicals, a number of which are known to cause cancer.
- Even brief exposure to secondhand smoke can cause a number of health problems in both adults and children, including lung cancer, asthma, heart disease, colds, ear infections, and pneumonia.
- Avoiding secondhand smoke completely is the best prevention strategy; opening windows, using a fan, or turning on an air conditioner do not eliminate the risks associated with secondhand smoke.
Secondhand smoke, also known as tobacco smoke pollution or environmental tobacco smoke, refers to both the smoke exhaled from a smoker’s lungs and the smoke created by a burning cigarette, cigar, or pipe. Cigars create larger amounts of secondhand smoke than cigarettes because they contain more tobacco and burn longer.
Secondhand smoke and disease
Nearly all Americans are exposed to secondhand smoke during their life. Breathing secondhand smoke is basically like smoking, which is why it is called passive smoking or involuntary smoking. Many of the harmful substances found in tobacco smoke, including benzopyrene, lead, carbon monoxide, arsenic, ammonia, formaldehyde, and a type of cyanide, stay in the air and go into the lungs and bloodstream, as do the other known cancer-causing chemicals.
According to the U.S. Surgeon General, there is no safe level of exposure to secondhand smoke. Even brief moments around smoke can be harmful to a person’s health. The U.S Surgeon General estimates that living with a smoker increases the chance of getting lung cancer  by 20% to 30%. Although research has not yet proved that secondhand smoke causes cancers other than lung cancer, there is some evidence that exposure to secondhand smoke may raise an adult’s risk of breast , nasopharyngeal , and nasal sinus  cancers.
Many studies show that secondhand smoke causes a large number of other health problems for people of all ages, such as asthma and heart disease in adults. Pregnant women, older adults, and people with breathing (respiratory) conditions and heart disease are especially at risk for negative health effects caused by exposure to secondhand smoke.
Health risks to children from secondhand smoke
Secondhand smoke is especially unsafe for babies and young children because their bodies and lungs are still developing. For children, secondhand smoke exposure raises the risk of the following conditions:
- Ear infections
- Asthma attacks
- Lung infections, such as bronchitis and pneumonia
- Coughing and wheezing
- Sudden Infant Death Syndrome (SIDS)
- Heart disease
Ongoing research continues to find additional links between secondhand smoke and children’s well-being, including evidence of links to mental health issues and problems with children’s ability to learn.
How to avoid secondhand smoke
When someone smokes indoors, it is not enough to keep the smoke away by opening a window or using a fan. In fact, some researchers suggest that the toxins from smoke that remain in a person’s hair and clothes or in carpet and furniture are hazardous to infants and children. Researchers describe this gradual buildup of toxins from secondhand smoke as “thirdhand smoke.”
The only way to avoid the risks of cigarette smoke is to avoid places where smoking occurs. Here are additional ways to help protect yourself and your family from secondhand smoke:
- Keep your home and car smoke-free. This includes making sure family, friends, and visitors never smoke inside your house or vehicle. Ask smokers to step outside.
- Many state and local governments require workplaces to be smoke-free. However, if your workplace does not ban smoking, ask for restrictions, such as banning smoking indoors.
- If your state does not currently have a smoking ban in place, choose to eat in restaurants that are smoke-free, and let the restaurant know that you have chosen to dine there partly because they do not allow smoking. Nonsmoking sections do not provide protection from secondhand smoke.
- When you travel, stay in smoke-free hotels and rent nonsmoking rental cars.
- Make sure the places where your child spends time, such as daycare, school, or after-school programs, do not allow smoking. Ask caregivers and relatives not to smoke around your children.
- If you smoke, quit. Quitting can be difficult, but there are many resources to help you , including talking with your doctor or a nurse.
Experts say that the only way to completely protect people from secondhand smoke is to get rid of smoking indoors. Anti-smoking laws have helped reduce nonsmokers’ exposure to secondhand smoke, and most states have passed laws banning or limiting smoking in public places, including the workplace. Almost half of the states and Washington, D.C., also do not allow smoking in restaurants and bars. Many counties and cities also have passed smoke-free laws. Find out more about your state’s smoking laws .