Most people are aware of the health dangers of outdoor air pollution, but may not realize that air pollution in their homes, offices, and schools also can have significant health effects. Recent studies have shown that people are exposed to higher concentrations of air pollution for longer periods of time inside buildings that outside. Air pollutant levels may be two to five times, and occasionally up to one hundred times, higher indoors than outdoors. These indoor air pollution levels are of concern to regulatory agencies because most people spend most of their time indoors. Indoor air pollution can cause immediate health effects, including headaches, dizziness, fatigue, asthma, hypersensitivity to particular substances, and irritation of the ears, nose, and throat. In the long term, people exposed to indoor air pollution may develop cancer, respiratory diseases, or heart disease.

Exposure to indoor air pollutants has increased over the past several decades because of construction of more tightly sealed buildings; reduced ventilation rates to save energy; use of synthetic building materials and furnishings; and use of chemically formulated personal care products, pesticides, and household cleaners. Sources of indoor air pollution include:

• combustion sources such as oil, gas, and wood;
• tobacco;
• building materials, including asbestos-containing insulation;
• furnishings, including flooring, wet or damp carpets, and cabinets or furniture made from certain processed wood products;
• household cleaning and personal care products;
• central heating and air conditioning equipment that contains microbes and dust;
• equipment such as printers;
• underground sources such as radon and pesticides; and
• outdoor air pollution, including pollen, dust, industrial emissions, and vehicle exhaust.

Usually the most effective way to improve indoor air quality is to eliminate pollution sources or reduce their emissions. Some sources, such as those containing asbestos, can be sealed or enclosed. Other sources, like gas stoves and furnaces, can be adjusted to decrease the amount of emissions. Banning smoking and substituting less toxic cleaning supplies, art materials, and paints also can reduce indoor air pollution.

Improving ventilation is another approach to lowering concentrations of indoor air pollutants. Fans that exhaust to the outdoors can be used in bathrooms, kitchens, laboratories, copy and print rooms, and cleaning-supply storage rooms. Some buildings need additional outdoor air brought in by way of fans, open windows, or improved ventilation systems.

Air cleaners also can improve indoor air quality. Furnaces and portable air cleaners can filter particles out of the air in homes. Gaseous contaminants can be removed by more sophisticated filtering.