Secondhand smoke is a mixture of the smoke coming off the end of a lit cigarette, cigar or pipe and the smoke being exhaled from a smoker's lungs. While most of its negative health effects are focused on the smoker, bystanders can inhale it directly or be affected by lingering smoke for hours after the smoker is gone.
The Environmental Protection Agency (EPA) classifies secondhand smoke as a known carcinogen (it causes cancer). It contains thousands of chemicals, over 50 of which are toxic or carcinogenic - including formaldehyde, vinyl chloride, arsenic, ammonia and hydrogen cyanide.
Immediate responses to secondhand smoke can include sore eyes and throat, irritation of the nose, headaches, coughing, nausea and dizziness.
Diseases linked to secondhand smoke
How smoking affects children
Secondhand-smoke exposure has been linked to asthma, sudden infant death syndrome (SIDS), bronchitis, pneumonia and ear infections. Children's lungs are still developing and can be adversely affected by secondhand smoke, especially when it is a constant reality in the home or vehicle. Young children and infants exposed to secondhand smoke make up thousands of hospitalizations for lower-respiratory-tract infections each year.
How to make the home and car safe