secondhand smoke

Secondhand smoke is the tobacco smoke you breathe without choosing to — the haze that fills a room when someone nearby is smoking. It is a mixture of the smoke exhaled by the smoker and the smoke drifting from the burning tip between puffs, so a non-smoker sharing the space inhales many of the same harmful chemicals.

The smoke rising from a smouldering cigarette (called sidestream smoke) is produced at a lower temperature and can carry even higher concentrations of certain toxins and carcinogens than the smoke drawn through the filter. Because of this, involuntary exposure is far from trivial: it is classed as a cause of lung cancer in non-smokers and aggravates asthma, respiratory infections and COPD.

Children are especially vulnerable, with higher rates of wheezing, ear and chest infections, and impaired lung growth when exposed in the home. There is no risk-free level of exposure; ventilation and air-cleaning reduce odour and visible smoke but do not remove the health hazard. Smoke-free environments are the only reliable protection. Residue that settles onto surfaces and dust, sometimes called thirdhand smoke, is a related but distinct concern.