APA Dictionary of Psychology

tobacco smoke breathed in by someone other than the person who is smoking. Secondhand smoke has two components: smoke exhaled by the smoker and smoke from the burning end of the tobacco source (e.g., cigarette, cigar, pipe). It contains more than 7,000 chemicals: Hundreds of them are toxic, and approximately 70 are carcinogenic. Breathing secondhand smoke (called passive smoking) is believed to have the same negative effects on adult health that direct smoking does—including increased risk for lung cancer, heart disease, and stroke—and to raise the risk of sudden infant death syndrome, ear infections, and asthma in children. Also called environmental tobacco smoke.