This page was reviewed under our medical and editorial policy by
Peter Baik, DO, Thoracic Surgeon
This page was updated on September 27, 2022.
Smoking tobacco is the leading cause of cancer throughout the world. But smoking isn’t just harmful to those who light up. Secondhand smoke, which is the smoke left in the air from cigarettes, cigars, pipes or other forms of tobacco, may also lead to cancer and premature death in both children and adults. Researchers are also looking into something called “thirdhand” smoke—the remnants of tobacco smoke that get caught in fabrics and land on hard surfaces.
Secondhand smoke causes cancer in much the same way as firsthand or direct tobacco smoking. When someone lights up a cigarette, cigar or tobacco pipe, smoke is released into the air from both the burning paper and tobacco itself (sidestream smoke) and from the breath that the smoker exhales (mainstream smoke). Both of these types of smoke contain substances that are harmful to breathe in, including the following carcinogens, or cancer-causing agents:
Exposure to carcinogens may cause cell mutations that lead to cancer. Like all tobacco smoke, secondhand smoke is associated with lung cancer. In the United States, it leads to 7,333 deaths from lung cancer per year among non-smokers and 33,951 deaths from heart disease per year, according to the U.S. Centers for Disease Control and Prevention. Research also suggests that it may be linked to breast cancer, nasal cancer and throat cancer in adults. It has also been linked to stroke.
Children are also harmed by secondhand smoke, starting in the womb.
“Thirdhand” smoke isn’t actually smoke, but rather what smoke leaves behind. Thirdhand smoke refers to the residual particles from tobacco smoke that settle on surfaces or in fabric, including floors, carpets, furniture and clothing. Research into whether thirdhand smoke may cause cancer is more limited than research into secondhand smoke. Still, some of the same carcinogens found in first and secondhand smoke have also been found in samples of dust taken from the homes of people who smoke, suggesting that inhaling or swallowing that dust may be harmful.
Exposure to secondhand and thirdhand smoke exists whenever indoor tobacco smoking is taking place. Keeping yourself and your family away from those situations is the only way to reduce the risk of cancer and other health problems posed by secondhand and thirdhand smoke. There is no safe level of exposure to secondhand smoke (information about thirdhand smoke isn’t yet known).
To avoid secondhand and thirdhand smoke:
If you’re inside where people are smoking, there isn’t anything you can do to protect yourself or others from secondhand or thirdhand smoke.
Public health measures introduced over the past few decades have worked to curb indoor smoking and reduce or eliminate workplace exposure to secondhand smoke. Federal law prohibits smoking on public transportation and in federal buildings. Recently, smoking inside public housing was banned. State laws about smoking vary across the country, but about half of states have banned smoking from places such as hospitals, malls, movie theaters, restaurants and bars. Authorities have also started banning smoking in open spaces such as parks and beaches in some cities and states.