Indoor Air Pollution

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We spend over 90% of our lives indoors, so the quality of indoor air we breathe is particularly important. Unfortunately, over the past few decades indoor air quality has continuously deteriorated. In an effort to reduce heating and cooling loads, many newer buildings have been weather-proofed by insulating walls and ceilings and by sealing windows. Little did anyone realize that these cost and energy saving measures would cause a multitude of problems resulting in what is commonly known as the “sick building syndrome.” It is estimated that 20-30% of people are exposed to toxins, and losses of as much as $400 billion dollars are attributed to sick buildings.

There are three basic sources of indoor contaminants:

1. People: People are carriers of many contaminants such as bacteria, germs, allergens, and not-so-obvious pollutants such as perfumes and fragrances. Even the simple act of breathing can emit many chemicals and shed millions of dead skin flakes.

2. Building materials: These include construction materials such as formaldehyde outgassing from particle boards, paints, glues, waxes, fiberglass, paper, dust, lint, carpet fibers, dirt, detergents and other cleaning materials, and, in the case of old buildings, asbestos from ceiling tiles.

3. Processes: Major contributing processes are tobacco smoking and indoor appliances, such as copying machines, computers, gas water heaters, gas stoves, and oven ranges.

The adverse effects of various gaseous pollutants were covered earlier when we discussed outdoor air pollution, so only those of other pollutants present mostly in indoor environments are given below:

Radon is a naturally occurring gas derived from the radioactive decay of uranium-238. It diffuses through rocks and soil and enters through cracks into concrete and clay basements. When ingested, a small amount diffuses through the lungs causing ionization of molecules and other unwanted chemical reactions along its path that may cause lung cancer and other ailments. According to EPA estimates about 20,000 persons are developing lung cancer as a result of exposure to radon in the home. Areas with naturally high concentration of radon are Brazil, China, India and Iran. Ionizing radiation will be discussed in greater detail in nuclear radiation.

Tobacco smoking is a significant contributor to indoor air pollution. Worldwide, over 2-3 million people die annually of smoke-related diseases such as lung cancer, emphysema, and bronchitis. The number in the United States is around 400,000. It has been reported that even a single cigarette in an office can quickly raise the levels of particulate matter to over 30 times the EPA standards (Neumann, 1973). In addition to tar and nicotine, tobacco smoke contains large amounts of carbon dioxide, formaldehyde, hydrogen cyanide, and benzene.

The concern about smoking became significantly greater among the general populace when it was discovered that smoking was not only a hazard for the smokers themselves, but for people around them. As evidence on the dangers of secondhand smoking mounted, smoking was banned in public places such as office buildings, theatres, shopping malls, buses, and airplanes in many US and Canadian cities. Other countries are slowly following their leads.

Asbestos is one of the most dangerous contaminants still found in older buildings. Because of its fire resistancy asbestos has been widely used in woven fiber mats, fireproof suits, gloves, gaskets, brake shoes, and even gas masks. The most popular applications of asbestos have been its use as insulating material in roof panels and corrugated walls.

Reports of fibrotic lung damage (asbestosis) among textile workers and ship insulators, massive increases in the number of lawsuits, and pressure from labor unions have forced the EPA to ban the use of asbestos in most products. Today, asbestos is used in US Navy submarines, and space shuttles’ solid fuel boosters carry asbestos-impregnated rubber liners to protect the steel casings from the heat of takeoff.

Pesticide is a general term that refers not only to insecticides (for killing insects), but also herbicides (for controlling weeds), fungicides, and fumigants and constitutes as a major contributor to indoor air pollution.

Mold refers to the growth of microorganisms on damp surfaces. Much of the mold found indoors comes from outdoor sources.

Other harmful substances found in everyday household products include formaldehydes, benzene, and chlorinated compounds. Formaldehyde, a component of many glues, resins, paints, surface coatings, particleboards, insulation foam, and wood paneling, is present in most furniture, shelving, and cabinetry. The major health effects associated with formaldehydes are headaches, dizziness, burning of the eyes and throat, nausea, and dermatitis. Benzene is known to cause leukemia and is present in most petrochemical products, tobacco smoke, and also many household products (such as glues and paints). Chlorinated substances are found in many dry cleaners, spray aerosols, and paint removers. PCB or polychlorinated biphenyl is used in insulation, lubricants, paints, and fluorescent lights. PCB is carcinogenic and is known to damage the liver, the skin, and to cause birth defects.

There is no federal law to regulate or limit indoor air pollutants. Several states have enacted their own regulations in terms of building codes, and some industries have adopted standards and developed guidelines that are mostly voluntary. In the absence of federal laws, it is best that we use our common sense and implement strategies that safeguard our health and the health of our loved ones. To reduce complications associated with indoor air pollution and “sick building syndrome,” it is best to remove their source by eliminating or reducing the use of toxins and substituting them with more environmentally friendly chemicals, proper maintenance, and increased ventilation. The costs are somewhat higher, but considering the cost of exposure to indoor pollutants, many feel it is worthwhile.


(1) Neumann, R. J., “Smoking and Air Pollution Standards,” Science, 182:335-336, 1973.

(2) Toossi Reza, "Energy and the Environment:Sources, technologies, and impacts", Verve Publishers, 2005

Further Reading

Gore, A., An Inconvenient Truth, Penguin Books, 2007.

Roleff, T., Pollution: Opposing viewpoints, Greenhaven Press, 2000.

Walsh, P. J., Dudney, C. S., Copenhave, E. D., Indoor Air Quality, CRC Press, 1984.

Environmental Science and Technology, published by the American Chemical Society.

External Links

Environmental Protection Agency (

Occupational Safety and Health Administration (OSHA) (

Intergovernmental Panel on Climate Control (IPCC), (

United Nations Environment Programme (

World Health Organization (WHO) (