What is thirdhand smoke?

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.


A person smoking represents firsthand smoke, two children inhaling the person’s cigarette smoke represents secondhand smoke, and a house with toys, clothes, and couch in the path of the cigarette’s smoke represents thirdhand smoke 

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.

Thirdhand smoke is the chemical residue left behind after secondhand tobacco smoke disappears from the air. Secondhand smoke is a combination of sidestream smoke from a cigarette and mainstream smoke exhaled by smokers. Thirdhand smoke is a mixture of toxic chemicals that sticks to surfaces, embeds in materials, and gathers in house dust. It embeds in carpets, walls, furniture, blankets, and toys and can re-emit from these into the air. Thirdhand smoke can linger indoors for years. People can be exposed to it by absorbing it through their skin, by consuming contaminated objects or dust, and by breathing polluted air.

The U.S. Surgeon General has concluded that there is no safe level of exposure to tobacco smoke. The California Air Resources Board has classified secondhand smoke as a toxic air contaminant. Many chemicals in secondhand smoke are also in thirdhand smoke, such as cancer-causing compounds, toxicants that harm reproductive organs, and toxicants that interfere with development (as defined by California’s Proposition 65 and the International Agency for Cancer Research). Thirdhand smoke also contains additional toxic chemicals that are not found in secondhand smoke because they form when tobacco smoke chemically changes in the environment.

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 February 2024


California Environmental Protection Agency, Air Resources Board, Office of Environmental Health Hazard Assessment. Technical support document for the “Proposed Identification of Environmental Tobacco Smoke as a Toxic Air Contaminant, Part A. http://www.arb.ca.gov/regact/ets2006/ets2006.htm

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Matt, G.E., P.J. Quintana, H. Destaillats, L.A. Gundel, M. Sleiman, B.C. Singer, P. Jacob, N. Benowitz, J.P. Winickoff, V. Rehan, P. Talbot, S. Schick, J. Samet, Y. Wang, B. Hang, M. Martins-Green, J.F. Pankow, and M.F. Hovell. 2011. Thirdhand tobacco smoke: emerging evidence and arguments for a multidisciplinary research agenda. Environ Health Perspect 119 (9):1218-26. doi: 10.1289/ehp.1103500.

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Son Y, Giovenco DP, Delnevo C, Khlystov A, Samburova V, Meng Q. Indoor Air Quality and Passive E-cigarette Aerosol Exposures in Vape-Shops. Nicotine Tob Res. 2020 Oct 8;22(10):1772-1779. doi: 10.1093/ntr/ntaa094. PMID: 32445475; PMCID: PMC7542645.

State of California, Environmental Protection Agency. Chemicals Known to the State to Cause Cancer or Reproductive Toxicity. Office of Environmental Health Hazard Assessment. February 25, 2022. https://oehha.ca.gov/proposition-65/proposition-65-list

U.S. Department of Health and Human Services. 2006. The Health Consequences of Involuntary Exposure to Tobacco Smoke: A Report of the Surgeon General. Available: http://www.surgeongeneral.gov/library/secondhandsmoke/

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