We usually think of air pollution as being outdoors, but the air in your house or office could also be polluted. Sources of indoor pollution include

• Mold and pollen
• Tobacco smoke
• Household products and pesticides
• Gases such as radon and carbon monoxide
• Materials used in the building such as asbestos, formaldehyde and lead

Sometimes a group of people have symptoms that seem to be linked to time spent in a certain building. There may be a specific cause, such as Legionnaire's disease. Sometimes the cause of the illness cannot be found. This is known as sick building syndrome.

Usually indoor air quality problems only cause discomfort. Most people feel better as soon as they remove the source of the pollution. However, some pollutants can cause diseases that show up much later, such as respiratory diseases or cancer.

Making sure that your building is well-ventilated and getting rid of pollutants can improve the quality of your indoor air.

Environmental Protection Agency