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Indoor air pollution is experienced through contamination of air in indoor areas from air pollutants arising from gases and particles. Compared to the commonly known outdoor air pollution, indoor air pollution is more dangerous. According to WHO, exposure to indoor air pollution causes the death of about 4.3 million people each year. Poor indoor air quality usually causes discomfort which ends after removal of the cause of the contamination. However, some air pollutants tend to cause respiratory diseases and cancer which shows up later in life. One of the primary sources of indoor air pollution is the use of solid fuels in homes, with others being biological pollutants, pesticides, and carbon monoxide from stoves and chimneys.

Biological Pollutants

Living things produce biological contaminants, which occur in areas with food and water or moisture. People and animals carry bacteria and viruses which contaminate the indoor air. Saliva and dander from household pets also cause this type of pollution. Other types of these pollutants include pollen from plants, droppings of some insects and rodents as well as their body parts, and mold. Health effects arising from these pollutants include allergic reactions such as some asthma types, allergic rhinitis, and hypersensitivity pneumonitis, which occur after repeated exposure. Microorganisms that grow in ventilation systems release toxins which can cause humidifier fever.

Pesticides

Pesticides help to control or kill pests which may include insects, rodents, and organisms such as fungi and bacteria. Use of these products in households contributes to indoor air pollution. Pesticides come in the form of sprays, powders, balls, sticks, and liquids. Exposure arises from containers storing the chemicals, surfaces collecting them and contaminated soil which generates dust that floats into households. The health effects resulting from exposure to pesticides include a higher risk of cancer and irritation of the respiratory tract and eyes. Some pesticides can lead to damaging of the kidneys, liver and the nervous and endocrine systems.

Carbon Monoxide And Nitrogen Dioxide

Nitrogen dioxide (NO₂) and Carbon monoxide (CO) are toxic gases. These two gases have almost the same sources and lead to indoor air pollution. Burning of solid fuel in fireplaces and wood stoves generates these gases. Other causes include tobacco smoke, gas stoves, unvented gas and kerosene heaters as well as back-drafting, equipment powered by gasoline, and welding. Health effects arising from these causes of indoor air pollution and other sources vary with the level of exposure. Carbon monoxide at low concentrations may cause fatigue in healthy individuals as well as chest pain in people suffering from heart diseases. Higher levels of the gas may lead to confusion, impaired vision, flu-like symptoms and even death. On the other hand, minimal exposure to nitrogen dioxide may irritate the respiratory tract and eyes, as well as causing an increase in bronchial reactivity among some asthmatics. High concentrations of nitrogen dioxide cause chronic bronchitis and pulmonary edema. Secondhand smoke resulting from tobacco use in cigarettes creates a higher risk of lung cancer.

Volatile Organic Compounds

Gases released by some solids and liquids make up volatile organic compounds, which have indoor concentrations that are up to ten times higher than levels found outdoors. Many household products have organic chemicals as their ingredients. These compounds arise from aerosol sprays, pesticides, wood preservatives, paint, cleansers, and dry-cleaned materials. Building materials, office equipment, and furnishings also produce volatile organic compounds. Exposure to these pollutants may cause dizziness, epistaxis, nausea, allergic reactions to skins, irritation of the respiratory tract, and may damage the nervous system, liver, and kidneys. Some of these compounds can cause cancer in both animals and humans.

Asbestos

Asbestos is a naturally occurring mineral fiber that was a common component in building construction materials in the past due to its fiber strength and ability to resist heat. Manufactured goods containing asbestos include floor tiles, ceilings, roofing shingles, some cement, and paper products. Heat-resistant fabrics and coatings also had this pollutant. Remodeling activities such as cutting and sanding may disturb materials made with asbestos leading to release of its fibers into the indoor air. Effects resulting from inhaling asbestos have no early signs and include cancer of the lungs, chest, and abdomen, as well as links to stomach, rectum, and intestines cancers. Exposure to asbestos may also cause heart failure and breathing problems, mainly from a condition known as asbestosis.

Radon

Radon is a radioactive gas formed when radium decays. Radon gains access to households and buildings through the ground water from wells, and building materials. The gas lacks color, taste, and odor making it hard to detect. There is a link between inhalation of radon and a high risk of lung cancer, which increases with exposure to tobacco smoke. Alpha particles emitted by the gas in the lungs damage lung tissue through bursts of energy they release. Damaged lung cells may reproduce resulting in cancer. According to the US Consumer Product Safety Commission, exposure to radon results in lung cancer deaths ranging between 7,000 and 30,000 every year. In Canada, radon causes up to 16% of all deaths related to lung cancer.

Particulate Matter And Formaldehyde

Particulate matter consists of small particles, either solid or liquid, floating in the air. These pollutants come from tobacco smoke as well as from wood stoves, kerosene heaters, and fireplaces. When inhaled, this matter can cause eye and respiratory tract irritation, development of bronchitis and also cancer. Formaldehyde is a chemical used in manufacturing household and building products. Exposure to formaldehyde causes fatigue, rashes, and irritation of the eyes, skin and respiratory tract. High concentrations of the chemical may cause some cancers.

Reduction Of Indoor Air Pollution

WHO recommends some interventions to reduce and control indoor air pollution. Use of alternative fuels such as biogas, solar power, and electricity is the primary method of overcoming this pollution. In regions where alternative fuels are limited, improved stoves will help to lower levels of pollutants emitted. Improved ventilation in the living environment will reduce exposure to smoke. Such interventions include incorporation of chimneys, eaves spaces, and smoke hoods. Behavioral changes when dealing with solid fuels is another method of controlling indoor air pollution. Wood needs drying before it is used, because dry wood improve combustion and reduce smoke production.