Secondhand Smoke Basics

What Is Secondhand Smoke?

Two types of lethal smoke waft from a cigarette and into the environment: sidestream smoke and mainstream smoke.
Two types of lethal smoke waft from a cigarette and into the environment: sidestream smoke and mainstream smoke.
©2006 Publications International, Ltd.

Secondhand smoke has a variety of names, including environmental tobacco smoke (ETS), passive smoking, and involuntary smoking. By definition, secondhand smoke is "sidestream smoke" (smoke from the burning end of a lit cigarette) or "mainstream smoke" (smoke that is exhaled from the lungs of a smoker).

When doctors refer to secondhand smoke, they are mostly describing sidestream, or ambient, smoke. Put another way, when a smoker lights up a cigarette, roughly 80 percent of the smoke burns off into the room and only 20 percent is inhaled. Sidestream smoke, then, is more dangerous than mainstream smoke.

While both types of smoke share most of the same compounds -- including more than 200 substances known to be harmful -- sidestream smoke has much higher concentrations of ammonia and chemical carcinogens such as benzene (an additive formerly found in gasoline before it was deemed to be too dangerous). A primary reason for this is that when a smoker inhales, he or she is drawing oxygen through the lit end of the cigarette, thereby nearly doubling the heat at which the smoke is produced. This increase in temperature results in the formulation of smaller, less harmful compounds.

Secondhand smoke is not solely derived from cigarettes; pipes and cigars produce many of the same harmful substances. In fact, a cigar produces much more sidestream smoke than a cigarette because of its larger size. Recent studies have shown that even hookahs carry a significant secondhand smoke risk.

The Contents of Secondhand Smoke

Most people who have been around a burning cigarette will tell you that the smell of the smoke is unpleasant. In addition to smelling bad, it can irritate your eyes and throat. However, the same can be said of just about any type of smoke, so there are other factors that make secondhand tobacco smoke so dangerous. Chief among them are the contents of secondhand tobacco smoke.

It is nearly impossible to come up with an exact accounting of what is in secondhand smoke because there are so many varieties of and ways to smoke. The main influences on the contents of secondhand smoke are:

  • The type of tobacco
  • The chemicals added to tobacco
  • The paper the tobacco is rolled in
  • The way the tobacco is smoked

There are, however, some common substances that most tobacco products produce. More than 4,000 chemicals have been identified in secondhand smoke, and the number goes up with each new study. According to the National Cancer Institute, more than 50 carcinogens have been found in secondhand smoke, including formaldehyde.

In addition, secondhand smoke contains many substances that interfere with normal cell development and function, such as nicotine and carbon monoxide. Secondhand smoke also has many insoluble particles, such as tar, that the body cannot use and simply build up over time.

A study from the August 2004 British Medical Journal reported that a cigarette releases 10 times the amount of air pollution as a diesel engine. In 1993, the Environmental Protection Agency categorized secondhand smoke in Group A -- the most severe form of carcinogen -- along with arsenic, mustard gas, and asbestos.

Naturally, there are a number of serious health problems associated with secondhand smoke. In the next section, we will look at these conditions, which range from heart disease to various types of cancer.

This information is solely for informational purposes. IT IS NOT INTENDED TO PROVIDE MEDICAL ADVICE. Neither the Editors of Consumer Guide (R), Publications International, Ltd., the author nor publisher take responsibility for any possible consequences from any treatment, procedure, exercise, dietary modification, action or application of medication which results from reading or following the information contained in this information. The publication of this information does not constitute the practice of medicine, and this information does not replace the advice of your physician or other health care provider. Before undertaking any course of treatment, the reader must seek the advice of their physician or other health care provider.