Indoor air is a dominant exposure for humans as more that half of the body’s intake during a lifetime is air inhaled in the home. Thus, most illnesses related to environmental exposures stem from indoor air exposure. Studies indicate that the levels of many air pollutants may be two to five times higher in indoor air than outdoor air. In some cases, indoor air pollutants may even be 100 times higher than outdoors. High levels of indoor pollutants are of particular concern because people may spend as much as 90% of their time indoors.
Indoor air quality is influenced by concentrations of outdoor air pollutants, indoor sources of pollution, characteristics of the building and the habits of the residents. It may arise from the use of open fires, unsafe fuels or combustion of biomass fuels, coal and kerosene. Gas stoves or badly installed wood-burning units with poor ventilation and maintenance can increase the indoor levels of carbon monoxide, nitrogen dioxide and particles. Other pollutants not associated with fuel combustion include building materials such as asbestos and cement, wood preservatives and others. Volatile organic compounds may be released by various sources including paints, glues, resins, polishing materials, perfumes, spray propellants and cleaning agents. Formaldehyde is a component of some household products and can irritate the eyes, nose and airways.
Pollution levels are measured by two important components which are (a) the level in the home, and (b) the length of time for which each person in the home is exposed to that level. Common indoor air pollutants include dust mites, pollen, mold, radon, carbon monoxide, excessive carbon dioxide, and other chemical fumes. A large number of combustion products originate from various different sources. Common sources include: Gas stoves and appliances, wood and coal stoves, gas and propane engines, fireplaces, tobacco smoke, candles and incense and mosquito coils. Combustion products include Carbon monoxide (CO), Nitrogen dioxide (NO2 ), Sulfur dioxide (SO2 ), Nitrogenated compounds (NOx ) and Particulate matter (PM). The largest reductions in indoor air pollution can be achieved by switching from solid fuels (biomass, coal) to cleaner and more efficient fuels and energy technologies.