To know what is in secondhand smoke, we first have to know what is in a cigarette. To that end, the following is a basic description of what is found in most cigarettes sold in the United States :
Cigarette tobacco is blended from two main leaf varieties: Virginia tobacco that contains 2.5-3% nicotine; and ‘burley’ tobacco that has a higher nicotine content (3.5-4%). U.S. blends also contain up to 10% of imported ‘oriental’ tobacco that is aromatic but relatively low (less than 2%) in nicotine.
In addition to the leaf blend, cigarettes contain ‘fillers’ which are made from the stems and other bits of tobacco that would otherwise be waste products. These are mixed with water and various flavorings and additives. The ratio of filler varies among brands.
Additives are used to make tobacco products more acceptable to the consumer. They include humectants (moisturizers) to prolong shelf life; sugars to make the smoke seem milder and easier to inhale; and flavorings such as chocolate and vanilla.
Additives are used to make cigarettes that provide high levels of 'free' nicotine that increases the addictive 'kick' of the nicotine. Ammonium compounds can fulfill this role by raising the alkalinity of smoke.
Additives are used to enhance the taste of tobacco smoke, to make the product more desirable to consumers. Although seemingly innocuous, the addition of flavorings making the cigarette 'attractive' and 'palatable' is in itself cause for concern. Furthermore, sweeteners and chocolate may help to make cigarettes more palatable to children and first time users; eugenol and menthol numb the throat so the smoker cannot feel the smoke's aggravating effects. Also, additives such as cocoa may be used to dilate the airways allowing the smoke an easier and deeper passage into the lungs exposing the body to more nicotine and higher levels of tar.