In the United States, most people spend about 90 percent of their time indoors. However, the indoor air we breathe at home and in other buildings can be more polluted than the outdoor air and increase the risk of illness.
There are many sources of indoor air pollution in the home. These include biological contaminants such as bacteria, mold, and pollen; the burning of fuels and tobacco; construction materials and furniture; household products; central heating and air conditioning systems; and various external sources.
The major indoor air pollutants in your home include radon, secondhand smoke, carbon monoxide, nitrogen dioxide, formaldehyde, pesticides, lead, volatile organic compounds, particulate matter, mercury, sulfur dioxide, dust, and asbestos (asbestos) . Buildings built before 1978 may contain sealant made with polychlorinated biphenyls, which can be released into indoor air.
Biological contaminants in the home include bacteria, mold, fungi, viruses, pet and other animal dander, dust mites, cockroaches, and pollen. Stagnant water, water-damaged materials, and wet surfaces can serve as breeding grounds for mold, fungi, bacteria, and insects. Biological contaminants can also be found in pets, dirty air conditioners or humidifiers, unventilated attics, laundry rooms with unvented dryers, and heating and air conditioning systems.
Combustion sources include oil, natural gas, kerosene, coal or wood fired stoves, furnaces, and space heaters. Other such sources include leaking fireplaces and ovens, gas-fired water heaters and clothes dryers, fireplaces, car exhaust pipes in garages, and tobacco. Indoor air pollutants from combustion sources are released primarily by malfunctioning or improper ventilation of heating devices or their improper or inefficient use.
Building materials and furniture that can cause indoor air pollution include insulation material, wet or damp rugs, roof tiles, tile, paint made with lead, latex paint made with mercury, fire retardant siding, chipboard, plywood panels. hardwood, fiberboard, and furniture made from certain hardboard products.
Household products that can cause indoor air pollution include solvents, varnishes, waxes, paints, curtains, glues, adhesives, cleaning and maintenance materials, wood preservatives, air fresheners, moth repellants, dry-cleaned clothing, personal care items, useful for activities of interest, and stored fuel and automotive products.
Outdoor air pollution can enter buildings and become a source of indoor air pollution. Sources of outdoor air pollution include radon and pesticides.
Indoor air quality is also a concern in office buildings, where it is affected by the maintenance and operation of ventilation systems and humidity. Sources of office air pollution may include, in addition to those commonly found in the home, office equipment, stored supplies, construction activities, mechanical systems, cleaning products, caulking and sealing pastes , vinyl floors, accumulated garbage and vehicle exhaust gases.
The "sick building syndrome" is an expression used to describe situations in which the occupants of a building have symptoms of illness related only to the time spent there. The causes of this syndrome include inadequate ventilation, indoor air pollution, and biological pollutants.
"Building-related illnesses" can be attributed to specific airborne pollutants within a building. These include Legionnaires' disease, a form of pneumonia related to indoor air pollution, asthma, hypersensitivity pneumonitis (inflammation of the lungs), and fever caused by humidifiers, a flu-like illness related to exposure to bacteria and fungi found in humidifiers, air conditioners, and aquariums.
Long-term health effects of indoor air pollution include respiratory and heart disease and cancer. Several indoor air pollutants are listed in the Fourteenth Report on Carcinogens published by the National Toxicology Program. Asbestos, formaldehyde, radon, and secondhand smoke are listed as carcinogens; lead and polychlorinated biphenyls are listed as "human carcinogens according to reasonable estimates." Some pesticides, solvents, and volatile organic compounds fall into both categories.
The short-term health effects of indoor air pollution include allergic, infectious and toxic reactions, such as watery eyes, runny nose, congestion, itching, coughing, wheezing, shortness of breath, headache, dizziness, nausea, vomiting, skin rash, fever, chills, and fatigue. Health problems related to moisture, biological contaminants, and mold include asthma, allergies, and hypersensitivity pneumonitis.
Virtual links from MedlinePlus (National Library of Medicine)
Passive smoke inhalation
About Asthma (United States Environmental Protection Agency)
Indoor Air Quality (United States Environmental Protection Agency)
Carbon Monoxide Information Center (US Consumer Product Safety Commission)
Home Energy and Health: Fuels for a Better Life (World Health Organization) (PDF - 2.65 MB)
Mold Fact Sheet (University of Maryland Department of Health and Mental Hygiene) (PDF - 56 KB)
Indoor Air Quality Fact Sheet (Centers for Disease Control and Prevention) (PDF - 2.46MB)
Moho (National Library of Medicine)