Indoor Air Pollution: An Evaluation of Three Agents


Environmental Tobacco Smoke


Combustion Gases

Environmental Tobacco Smoke


Environmental tobacco smoke (ETS) is the particulate matter that is emitted either directly from a tobacco product or exhaled by a smoker. It is comprised of “mainstream” smoke or that which is exhaled by a smoker and “side stream” smoke that is emitted directly from the burning tobacco product. There are approximately 4,000 individual compounds that make up tobacco smoke, including formaldehyde, carbon monoxide, benzene, and ammonia (1).

ETS contains most of the same compounds that a smoker is exposed to, including some forty to sixty carcinogenic or potentially carcinogenic compounds. The Environmental Protection Agency (EPA) has classified ETS as a Group A carcinogen meaning that is does cause cancer in humans.


Fate and Transport

The persistence of ETS in the indoor environment can vary depending on the size of the room and the air exchange rate. In a low-exchange environment, ETS may be slow to disseminate and persist in the environment. Similarly, in an area with greater ventilation, ETS may be diluted more quickly. Some studies have shown higher consistent levels of ETS when air is re-circulated such as in air conditioned environments. Generally, ETS in an indoor environment is measured in terms of hours (1).

ETS can be inhaled by individuals, released from a room through vents or other points of egress, or, due to its particle nature, deposited on furniture, flooring, or other objects. The rates at which these outcomes occur depend on ventilation and volume in the room.


Monitoring in the Environment

ETS can be monitored in the indoor environment using two different types of monitoring; personal and stationary monitors (1). Personal monitors can be worn by an individual to capture the particulate that they come into contact with and analyzed for constituents commonly found in ETS. These monitors must be worn in the breathing zone and are only useful in determining individual exposures due to various activities that might take place outside of the indoor environment.

Stationary monitors are another means of collecting ETS data. With this type of monitoring, a monitor is placed in a fixed location and used to collect particulate in a specific room or area. These monitors, similar to personal monitors, usually rely on some type of paper or fabric filter media that collects particulate. Filters are collected and weighed to obtain a total mass of particulate. That particulate is then analyzed in a laboratory for individual constituents that may be indicators of ETS.


Exposure Pathway

Human exposure to ETS occurs through breathing contaminated air. Once in the lungs, certain chemical compounds contained in the smoke may be absorbed into the bloodstream through lung tissue. ETS can also come in contact with mucosal membranes in the nose and eyes. Exposures may be acute or chronic and children or people with respiratory illnesses may be especially sensitive to ETS.

Measuring Human Exposure

Human exposure to ETS can be measured in ways much like those used to measure other indoor air pollutants. But due to the nature of ETS and its sources, there may be significant variability in some monitoring procedures. The amount of smoking that an individual is exposed to, the length of time during which someone is exposed to ETS, and the volume of the room in which they are exposed may affect the degree of accuracy achieved in human exposure monitoring. Time scales are very important for ETS when looking at correlations to health effects (1).

One way of measuring exposure to ETS in the human body is through the use of biomarkers or chemicals that can be found in the body that are indicative of exposure to an agent that carries the same chemical compound. One example of this is monitoring the level of cotinine in a person’s blood, saliva, or urine. Cotinine, a metabolite of nicotine, is specific to tobacco smoke and is an indicator of chronic exposure (2). While there is data available for cotinine, other chemical compounds present in ETS can be monitored as biomarkers. However, since ETS is comprised of numerous compounds, some of which may have other sources in an indoor environment, there is no single indicator of human exposure (1).

Another source of information on human exposure can come from personal monitoring from passive monitors worn by an individual to track their exposure throughout a specific period of time or in a specific area. These monitors use a paper or fabric filter as the media and must be work in the individual’s breathing zone. They are designed to capture aerosols or very fine particulate matter such as that which ETS consists of. For best results, time and activity diaries should be kept by participants in order to correlate activities with exposure (1).



Several individual actions can limit the amount of ETS exposure non-smokers receive by:

  • Simply staying away from smoking areas
  • Eating in non-smoking areas and banning smoking in your home are fairly obvious interventions.
  • If you have children, be sure that daycares and schools enforce non-smoking policies.
  • Most workplaces ban smoking in part or all of their premises or can designate a ventilated area for smoking, thereby reducing non-smokers’ exposure in the workplace.

If you don’t currently have a smoke-free workplace, you may want to lobby the employer to see if they would designate an appropriate smoking area or verify that they are in fact compliant with state or federal regulations regarding smoking in the workplace. bcaffair/files/wcb.htm <>