Also called: Environmental tobacco smoke · Passive smoking · Tobacco smoke pollution
Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.
About Secondhand Smoke
Secondhand smoke is a mixture of the smoke that comes from the burning end of a cigarette, cigar, or pipe, and the smoke breathed out by the smoker. It contains more than 7,000 chemicals. Hundreds of those chemicals are toxic and about 70 can cause cancer.
Health effects of secondhand smoke include:
- Ear infections in children
- More frequent and severe asthma attacks in children
- Heart disease and lung cancer in adults who have never smoked
There is no safe amount of secondhand smoke. Even low levels of it can be harmful. The only way to fully protect nonsmokers from secondhand smoke is not to allow smoking indoors.
Centers for Disease Control and Prevention
It sits within Poisoning, Toxicology, Environmental Health.
The lead U.S. institute for this subject is the National Cancer Institute.
When to speak to someone. Reading about a topic cannot tell you whether it applies to you. Speak to a doctor or pharmacist if symptoms are severe, sudden, getting worse, or simply not going away — and seek emergency care immediately for chest pain, breathing difficulty, sudden weakness or confusion, or a serious allergic reaction.
Research on Secondhand Smoke
122 studies areregistered for this condition on ClinicalTrials.gov, the U.S. National Library of Medicine's public registry. A selection is below — the links go straight to the registry entry, not to a summary of ours.
What a registered study does and does not mean. Registration means a study exists and has been declared publicly. It says nothing about whether the treatment being tested works, is safe, or is available to you. Many studies find no benefit — that is what research is for. Never seek out an experimental treatment on the strength of a registry entry alone.
Research currently under way
- Smoking Cessation Intervention Including Health Navigators to Address Unmet Social Needs of Parents Who SmokeSt. Justine's Hospital
- Modifying Progesterone and Estradiol Levels to Prevent Postpartum Cigarette Smoking Relapse and Reduce Secondhand Smoke Exposure in Infants and ChildrenUniversity of Minnesota
- Implementing an Adapted Smoke-free Homes Intervention in SpainInstitut Català d'Oncologia
- Measuring Environmental Tobacco and Cannabis: Pollutants and ExposuresUniversity of California, San Francisco
- Secondhand Smoke Respiratory Health StudyUniversity of California, San Francisco
- Early Life Intervention in Pediatrics Supported by E-health - SMOKEInsel Gruppe AG, University Hospital Bern
Research already completed
- Impact of Ban on Smoking in Pubs, Restaurants and Nightclubs on Endothelial Function in WorkersUniversity Hospital, Toulouse
- Educational Models for Tobacco Exposure AwarenessKarabuk University
- Novel Methods to Reduce Children's Secondhand Smoke Exposure IIUniversity of Oklahoma
- Preliminary Investigation of Novel Methods to Reduce Children's Secondhand Smoke ExposureUniversity of Oklahoma
- Supporting Smoke-Free Policy Compliance in Public HousingColumbia University
- Perioperative Counselling and Parental Awareness of Second-hand SmokeUniversity of Liege
Study data from ClinicalTrials.gov, a service of the U.S. National Library of Medicine. Retrieved 2026-07-30. Registry entries are supplied by study sponsors and investigators; ClinicalTrials.gov does not verify their scientific validity. PocketsInfo is not affiliated with, and not endorsed by, the NLM or the NIH.
Where to read more
Rather than paraphrase, we point you to the primary sources. Every link below is to a government health agency, a national institute or a recognised medical body — grouped by what you are trying to find out.
Start Here
- About Secondhand SmokeCenters for Disease Control and Prevention
- Health Risks of Secondhand SmokeAmerican Cancer Society
- Secondhand SmokeNational Cancer Institute, Tobacco Control Research Branch
- Secondhand Smoke and CancerNational Cancer Institute
- Secondhand Smoke and Electronic-Cigarette AerosolsEnvironmental Protection Agency
- Secondhand Tobacco Smoke (Environmental Tobacco Smoke)National Cancer Institute
Prevention and Risk Factors
- Preventing Exposure to Secondhand Smoke in the HomeCenters for Disease Control and Prevention
Related Issues
- Health Harms from Secondhand SmokeCampaign for Tobacco-Free Kids
- Health Problems Caused by Secondhand SmokeCenters for Disease Control and Prevention
- How Long Do the Harmful Elements of Secondhand Smoke/Aerosol Linger Indoors?Environmental Protection Agency
- Is Outdoor Exposure to Secondhand Smoke/Aerosol Comparable to Indoors?Environmental Protection Agency
- Tobacco Smoke, Vaping, and AsthmaAsthma and Allergy Foundation of America
- What Can I Do about Secondhand Smoke/Aerosol Exposure Coming From My Neighbor's Apartment?Environmental Protection Agency
- What is Thirdhand Smoke, and Why Is It a Concern?Mayo Foundation for Medical Education and Research
Statistics and Research
- Secondhand Smoke ExposureNational Cancer Institute
- Trends and Disparities in Secondhand SmokeCenters for Disease Control and Prevention
Clinical Trials
- ClinicalTrials.gov: Tobacco Smoke PollutionNational Institutes of Health
Medical subject headings
Clinicians and researchers index this subject under Tobacco Smoke Pollution. These are the terms to use when searching medical literature.
This page is built from the MedlinePlus health topic record for Secondhand Smoke, a service of the U.S. National Library of Medicine (NLM), National Institutes of Health. Information is from MedlinePlus.gov. PocketsInfo is not affiliated with, and is not endorsed by, the NLM or the NIH. Retrieved 30 July 2026.