Passive smoking, or secondhand smoke exposure, is breathing in smoke from other people using tobacco. Secondhand smoke contains the same harmful chemicals inhaled by the smoker and has no established safe level of exposure.
Health effects are best documented in children, including higher rates of respiratory infections and asthma flares, and in adults sharing homes with smokers. Reducing exposure is one of the strongest motivators reported by parents who quit, and smoke free home rules also improve quit success.