What is secondhand smoke?

Secondhand smoke is the combination of smoke from a burning cigarette and smoke exhaled by a smoker. There are two types of secondhand smoke; side stream smoke comes directly from the burning tobacco product, and mainstream smoke is the smoke that the smoker inhales. The smoke that burns off the end of a cigarette or cigar actually contains more harmful substances than the smoke inhaled by the smoker, as there is no filter it must pass through.

How does secondhand smoke affect non-smokers?

If you are a non-smoker but are exposed to secondhand smoke on a regular basis, your body will still absorb nicotine and other harmful substances. Smoke contains more than 4000 chemical compounds, of which 250 are toxic and more than 50 are known cancer-causing agents. These dangerous substances linger in the air for approximately 4 hours and breathing in these particles for only minutes can harm you.

Exposure time to secondhand smoke and effects:

  • 5 minutes – stiffens the aorta as much as smoking a cigarette
  • 20-30 minutes – causes excess blood clotting, as well as increases the buildup of fat deposits in blood vessels, increasing the risk of heart attack and stroke.
  • 2 hours – increases the chance of irregular heart beat (arrhythmia) and can trigger a fatal cardiac event or heart attack.

In addition, the longer you are around secondhand smoke, the greater the level of harmful substances in your body. As a result, you might have an increased risk of developing smoking-related disorders, including:

  • Lung cancer and lung disease, including COPD, emphysema, asthma, and chronic bronchitis. Nonsmokers who live with a smoker have a 20% to 30% increased risk for developing lung cancer.
  • Heart disease
  • Eye and nasal irritation; increased risk of sinus and respiratory infections

Who is at greatest risk of being harmed by secondhand smoke?

Although any person who spends time around those who smoke has an increased chance of developing a smoking-related illness, certain people are extremely susceptible to the harmful effects of secondhand smoke. These include:

Service industry workers, such as bartenders and restaurant servers. People who work in environments where they are constantly exposed to smokers might absorb carcinogens and other harmful substances from secondhand tobacco smoke on a regular basis. This puts them at greater risk of developing the health issues addressed above.

Pregnant women. Second hand-smoke harms not only the mother-to-be, but her unborn child as well. Smoke exposure during pregnancy increases the risk for problems such as placenta previa (low lying placenta), placental abruption (a medical emergency), as well as miscarriage, stillbirth, and ectopic pregnancy. It decreases the amount of oxygen available to mother and baby, increases the baby’s heart rate, and increases the likelihood that the baby will have a low birth weight or be born prematurely.

Infants and children (and pets!). Because young children and animals can't choose to leave a smoke-filled environment, this constant exposure makes them especially vulnerable to the health risks of secondhand smoke. Infants and children who are regularly exposed to secondhand smoke have an increased chance of developing the following conditions:

  • Frequent colds and respiratory infections (including bronchitis and pneumonia)
  • May experience slow or incomplete lung growth and development
  • Asthma and chronic coughs
  • Chronic and/or recurrent ear infections
  • SIDS (Sudden Infant Death Syndrome)
  • High blood pressure
  • Learning and behavior problems, including inattention and aggression.
  • Cataracts
  • Poor dental health
  • Increased likelihood that the children themselves will become smokers
  • Increased risk of tumors and cancer shown in cats, dogs, and birds

What can I do to avoid secondhand smoke?

The following suggestions might be helpful in reducing, or even eliminating, you and your family’s exposure to secondhand smoke:

  • Whenever possible, ask visitors to your home to smoke outside and to use a “smoking coat” or sweatshirt so that they will not carry toxins on their clothes (this is actually known as “third-hand smoke”).
  • Open windows and use fans to ventilate rooms in your home and work.
  • Don't keep ashtrays in your home.
  • Tell babysitters and other caregivers not to smoke around your children, even if it is in their own home.
  • If you are visiting a smoker’s home with your children, try to socialize outside whenever possible.
  • If smoking is allowed where you work, talk to your employer about modifying the company’s smoking policy. Encourage them to support a program to help their employees quit!
  • Ask to work near other non-smokers or as far away from smokers as possible.
  • When staying in a hotel, ask for a non-smoking room.
  • Stay informed about any changes in federal, state, and local smoking laws and become involved in strengthening those laws.

Last reviewed by a Cleveland Clinic medical professional on 01/30/2017.


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