“Thirdhand smoke” (THS) refers to residues of nicotine and other harmful chemicals from tobacco smoke that absorb into indoor surfaces, furniture, carpets, bedsheets, skin, and pet fur.

THS residue can contain more than 250 chemicals and remain on surfaces for weeks, months, or even years. These chemicals may also re-emit back into the air as gases and react with other chemicals, creating new chemicals that may be harmful to inhale.

Children are particularly susceptible to THS because they spend more time on the floor and often touch surfaces and objects with their hands or mouth.

In this article, we will discuss what THS is, its potential impacts on health, how to prevent it, and when a person should speak with a doctor.

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THS is the residues of nicotine and more than 250 other chemicals in tobacco smoke that can absorb into indoor surfaces.

The residue can stay on surfaces for weeks, months, or even years. It can build up on skin, animal fur, and indoor surfaces such as:

  • furniture
  • clothes
  • carpets
  • bedsheets
  • car dashboards
  • toys

THS residue can also re-emit back into the air and react with other chemicals in the environment, forming new chemicals that can cause harm when people inhale them. The longer these chemicals are in the air, the more toxic they are to inhale.

Read more about secondhand smoking.

There is limited research into the effects of THS on people. However, a 2014 study on mice suggested that THS may cause behavioral and physical effects such as lung damage, liver damage, and hyperactivity.

Pregnant people

Research from 2021 suggests that exposure to any kind of tobacco smoke, including THS, may be harmful during pregnancy, negatively affecting a person’s quality of life.

If a pregnant person lives with someone who smokes, they should encourage that person to quit smoking as soon as possible. Similarly, if a pregnant person smokes, they should try to quit smoking right away, as smoking while pregnant may:

Learn more about the risks of smoking during pregnancy and how to quit.

Children

Children are more vulnerable to THS because they often touch surfaces and objects in the home with their hands or mouths.

Research suggests that children also have thinner skin and breathe faster than adults, which can speed up the absorption of THS. In addition, the harmful chemicals in THS may lead to an increased risk of a child developing cancer.

Adults

Studies suggest that THS may have several negative health effects in adults, including:

However, researchers advise that further studies are necessary to investigate the effects of THS on human health.

The only way to prevent THS exposure is to stop smoking. In particular, people should avoid smoking indoors, where chemicals from tobacco smoke can settle on surfaces.

According to the American Lung Association, smoking next to an open window does not prevent THS.

A person may want to try to quit smoking to eliminate the risks of THS exposure for themselves and others.

Learn more about what happens after a person quits smoking.

If a person wants to quit smoking to prevent THS exposure and other health risks, they should speak with their doctor for support and advice. A healthcare professional can recommend support groups, nicotine replacement therapies, and other strategies that a person may find helpful.

Alternatively, some health organizations, such as the Centers for Disease Control and Prevention (CDC), provide resources that may help a person quit smoking.

A person may also wish to contact a doctor if they smoke or spend time around others who smoke and they are experiencing any new health problems, such as coughing or difficulty breathing.

THS consists of harmful chemicals from tobacco smoke that absorb into indoor surfaces, furniture, skin, and pet fur. These chemicals can also re-emit into the air and mix with other chemicals in the environment, forming new chemicals that can be harmful to inhale.

Children may be more vulnerable to THS exposure because they typically spend more time on the floor, touch many surfaces with their hands, and may often put objects into their mouths.

Research into the effects of THS exposure on people is limited. However, studies suggest that exposure to THS may negatively affect a person’s health in several ways.

The only way to prevent THS exposure is to keep indoor spaces completely smoke-free. A person may want to consider quitting smoking to prevent THS.

People should speak with a healthcare professional if they are considering quitting smoking. Additionally, a person may want to contact a doctor if they are experiencing any symptoms, such as coughing and difficulty breathing, after exposure to tobacco smoke.