The Short Answer
Thirdhand smoke is the chemicals left behind when someone smokes tobacco. Thirdhand smoke is unhealthy for people and pets. It can stick around for a long time in homes and cars. It gets into your body if you inhale, swallow, or touch the chemicals. Getting rid of it is really hard and can cost a lot of money.
There are many sources of air pollution, like car exhaust and smoke from factories, but pollution from thirdhand tobacco smoke is easier to reduce than many other kinds. People are more likely to change their habits to reduce tobacco smoke—like not smoking near others—than to stop driving cars. Also, some dangerous chemicals in thirdhand smoke only come from tobacco smoke. This means tobacco smoke adds unique cancer-causing chemicals to the air, even if it is already polluted. Thirdhand smoke pollution is often found in places like homes and cars, where we spend much of our time and want our families and pets to be safe. To protect the people and animals we care about, we need to stay away from thirdhand tobacco pollution.
The Long Answer
Thirdhand smoke is the chemical residue from tobacco smoke. It is also called “tobacco smoke residue” or “stale tobacco smoke.” The chemicals in thirdhand smoke are toxic to humans, especially children. It can linger for years in dust and on household surfaces. It can also become embedded in carpets, furniture, clothes, and building materials. It is difficult and expensive to remove.
There are many pollutants that can contaminate our environment, such as vehicle emissions and industrial air pollutants. Policymakers and the public often focus on these types of pollutants. However, there remain a lot of other forms of pollution to consider, such as pollutants from tobacco smoke. Addressing tobacco smoke pollution highlights a preventable cause of harm, in this case, smoking, that can be changed or eliminated to keep the environment clean and healthy. For example, it is much more reasonable to ask someone not to smoke around others than it is to ask someone not to drive a vehicle.
In addition, some of the toxic and cancer-causing chemicals in thirdhand smoke are only found in tobacco smoke. This means that thirdhand smoke adds a unique mixture of harmful substances to the ones already in the air created by pollution from cars and factories. To prevent exposure to these additional pollutants, individuals should never allow smoking indoors or near a doorway or window.
Eliminating exposure to toxic pollutants is important for protecting human health. This means addressing many forms of air pollution, including tobacco smoke residue.
Do you have more questions about the toxic legacy of tobacco smoke, how it affects human health, and what we can do about it? Learn more here.
Updated: March 2025
Sources:
Jacob P 3rd, Benowitz NL, Destaillats H, et al. Thirdhand smoke: New evidence, challenges, and future directions. Chemical Research in Toxicology. 2017;30(1):270-294. doi: 10.1021/acs.chemrestox.6b00343
Whitehead TP, Havel C, Metayer C, et al. Tobacco alkaloids and tobacco-specific nitrosamines in dust from homes of smokeless tobacco users, active smokers and nontobacco users. Chemical Research in Toxicology. 2015;28(5):1007-14. doi: 10.1021/acs.chemrestox.5b00040
Schick SF, Farraro KF, Perrino C, et al. Thirdhand cigarette smoke in an experimental chamber: Evidence of surface deposition of nicotine, nitrosamines and polycyclic aromatic hydrocarbons and de novo formation of NNK. Tobacco Control. 2014;23(2):152-9. doi: 10.1136/tobaccocontrol-2012-050915
