Second Hand Smoke
Secondhand smoke is also known as Environmental Tobacco Smoke. Secondhand smoke includes both exhaled mainstream smoke from smokers and sidestream smoke from the end of a cigarette, cigar, or pipe. Secondhand smoke contains more than 4,000 substances, including over 40 that are linked to cancer. Many of the compounds in tobacco smoke are released at higher rates in sidestream smoke than in mainstream smoke.
Secondhand smoke may trigger asthma episodes and make asthma symptoms more severe in children who already have asthma. Moreover, secondhand smoke is a risk factor for new cases of asthma in children who have not previously exhibited asthma symptoms.
The means by which secondhand smoke triggers an asthma episode is believed to be through its irritancy effects. That is, smoke irritates the chronically inflamed bronchial passages of asthmatics. This is a different pathway from most of the other environmental triggers of asthma, like dust mites and pet dander, which trigger asthma episodes through allergenic effects.
Exposure to secondhand smoke is also known to cause a variety of other negative health consequences, including lung cancer, ear infections in children, and respiratory illnesses.
Many of the health effects of secondhand smoke (including asthma) are most clearly manifested in children. This is because children are particularly vulnerable to secondhand smoke. This is likely due to several factors, including the fact that children are still developing physically, have higher breathing rates than adults, and have little control over their indoor environments. Children receiving high doses of secondhand smoke, such as those with smoking mothers, run the greatest relative risk of experiencing damaging health effects.