Impact of indoor air pollution on occupants


Indoor air pollution according to American Society of Heating, Refrigerating and Air-Conditioning Engineers (2013) is the presence of one or more contaminants indoors that carry a certain degree of human health risk. This risk usually goes unnoticed because most often when air pollution is mentioned, many people are quick to think of smog and car emissions which are outdoor air pollution.

Andersen (2009) highlighted that indoor air pollution which is usually taken for granted by the general public is more dangerous to health when compared to outdoor air pollution which enjoys more attention.  Indoor air pollution occurs when certain air pollutants from particles and gases contaminate the air of indoor areas. Millions of people around the world  prepare their meals using traditional methods (i.e. wood, charcoal, coal, dung, crop wastes) on open fires. Such inefficient practices can increase the amount of air pollutants inside the home and can also cause serious health problems.

According to World Health Organisation [WHO] (2012), 4.3 million people a year die from the exposure to household air pollution. This type of pollution is significantly more dangerous due to how concentrated the air is in indoor environments. Before you can fully comprehend the effects of indoor air pollution you must first be able to understand the causes of it as well as what we can do to improve our quality of air both indoors and outdoors.

Akanni (2012) stated that people spend the majority of their time indoors, where they face significant health risks due to repeated exposure to air pollutants in their homes, offices, schools and other indoor environments. Exposure to these pollutants can lead to numerous immediate and long-term health problems. Common pollutants include respirable particles, chemical emissions, mould spores, animal allergens, radon, combustion gases, environmental tobacco smoke and pesticides (Gana, 2013).

Conceptual framework

Godish (2009) defined ‘indoor air’ as air within a building such as your home, classroom, office, shopping center, hospital or gym.  This type of air can be said to be polluted if contaminated by smoke, chemicals, smells or particles. According to Davis (2016) indoor air pollution refers to contamination of quality of air due to physical, chemical, and biological factors in the indoor environment within a home, building, or an institution or commercial facility.

Ayars (2012) opined that indoor air pollution refers to toxic contaminants that we encounter in our daily lives in our homes, schools and workplaces. Many pollutants build up rapidly indoors, resulting in higher levels than usually found outside, especially in newer homes where tighter construction prevents particles from escaping the home. These pollutants can cause a variety of health problems and can even be fatal at high levels.

Unlike outdoor air pollution, the effect of indoor air pollution is health related and less of an environmental issue. In colder regions, building and heating methods make use of airtight spaces, less ventilation and energy efficient heating. Sometimes synthetic building materials, smells from household care and furnishing chemicals can all be trapped indoors. As less fresh air gets indoors, the concentration of pollutants such as pollen, tobacco smoke, mold, pesticides, radon, asbestos and carbon monoxide trapped inside the building increases and people breathe that in (Jones, 2009).

Indoor air pollution is a concern in the developed countries, where energy efficiency improvements sometimes make houses relatively airtight, reducing ventilation and raising pollutant levels. Indoor air problems can be subtle and do not always produce easily recognized impacts on health. Different conditions are responsible for indoor air pollution in the rural areas and the urban areas (Gana, 2013).

Factors determining indoor air quality

According to Bhatt (2013) the main factors that determine indoor air quality are:

  • Chemicals
  • Radon
  • Suspended particles
  • Microbes
  • Pets and pests
  • Humidity
  • Ventilation
  • Temperature


  1. Chemicals

Two common complaints regarding poor indoor air quality are bad smells and irritation of the eyes, nose and throat. Such irritation may be induced by specific chemicals, but also by factors such as dry air. Bad smells are not harmful in themselves but may cause unpleasant effects and increase symptoms such as headache, nausea, and irritation of eyes or throat. The hazards associated with chemicals and their effects on health are not always well known, particularly for long term exposures (Armstrong & Campbell, 2011).

  1. Radon

Radon is a gas that occurs naturally in soil and rock in some regions and that can get inside buildings by diffusing through the soil. Radon gas mixed with indoor air can lead to lung cancer (Bhatt, 2013).

  1. Suspended particles

Coarse, fine and ultrafine particles in ambient air are known to cause adverse health effects, including on the respiratory and cardiovascular systems. Particles may in part come from outdoor pollution, but can also form indoors by the burning of fuels for heating and cooking, and by reactions between ozone and some volatile organic compounds (VOCs). In addition, man-made nanoparticles, that are increasingly used in consumer products, may have an impact as indoor air pollutants (Das, 2014).

  1. Microbes

Microorganisms such as fungi and viruses may play a role in the development of asthma and allergies involving the airways. This is for instance a problem in damp buildings or indoor environments where there is mould because many fungi release substances that cause allergies. Virus infections may also be transmitted through indoor air and some of them can lead to an increase in asthma, measles, influenza and allergies (Sengler, 2011).

  1. Pets and pests

Indoor pests, house dust, mites, cockroaches, and rodents in houses in cities in particular – mice are important sources of allergens. These allergens can lead to diseases of the airways and asthma. Exposure varies depending on the type of environment and cultural habits (Bhatt, 2013).

  1. Humidity

There is an optimal level of humidity in indoor air. Too low humidity causes eye irritation, dry skin, and rashes, whereas too high humidity results in water damage and mould problems and favours the growth of dust mites (Bhatt, 2013).

  1. Ventilation

It is one of the most important factors determining indoor air quality. Poorly aired homes, offices and schools, for instance can affect health and work or academic performance. Controlled ventilation is especially needed in heavily insulated buildings that allow little air exchange with the outside (Haq & Dasgupta, 2016).

  1. Temperature

As well as causing discomfort, indoor air that is very cold or hot is highly unhealthy. Air that is too warm, for example, aggravates the effects of insufficient humidity (Armstrong & Campbell, 2011).

Common indoor air pollutants

Several factors contribute to indoor air pollution. Some of the common indoor air pollutants according to Radford (2016) are:

  • Asbestos
  • Biological pollutants
  • Carbon monoxide
  • Formaldehyde/compressed wood products
  • Lead
  • Nitrogen dioxide (NO2)
  • Pesticides
  • Indoor particulate matter
  • Secondhand smoke/ environmental tobacco smoke
  • Volatile organic compounds

1. Asbestos

Asbestos is a mineral fibre that occurs in rock and soil. Because of its fibre strength and heat resistance it has been used in a variety of building construction materials for insulation and as a fire-retardant. Asbestos has been used in a wide range of manufactured goods, mostly in building materials, friction products, heat-resistant fabrics, packaging, gaskets and coatings. Elevated concentrations of airborne asbestos can occur after asbestos-containing materials are disturbed by cutting, sanding or other remodelling activities. Improper attempts to remove these materials can release asbestos fibres into the air in homes, increasing asbestos levels and endangering people living in those homes (Radford, 2016).

  1. Biological pollutants

Biological contaminants include bacteria, viruses, house dust, mites, cockroaches, and pollen. There are many sources of these pollutants. By controlling the relative humidity level in a home, the growth of some sources of biological pollutants can be minimized. A relative humidity of 30-50 percent is generally recommended for homes. Standing water, water-damaged materials or wet surfaces also serve as a breeding ground for molds, mildews, bacteria and insects. House dust and mites are  source of one of the most powerful biological allergens, grow in damp, warm environments (Radford, 2016).

  1. Carbon monoxide

Carbon monoxide (CO) is an odourless, colourless and toxic gas. Because it is impossible to see, taste or smell the toxic fumes, CO can kill people living in a house before they are aware of it in the home. The effects of CO exposure can vary greatly from person to person depending on age, overall health and the concentration and length of exposure. Sources of CO include unvented kerosene and gas space heaters, leaking chimneys and furnaces, back-drafting from furnaces, gas water heaters, wood stoves and fireplaces, gas stoves, generators and other gasoline powered equipment, automobile exhaust from attached garages, tobacco smoke, auto, truck, or bus exhaust from attached garages, nearby roads, or parking areas, etc. (Radford, 2016).

  1. Formaldehyde/pressed wood products

Formaldehyde is an important chemical used widely by industry to manufacture building materials and numerous household products. It is also a by-product of combustion and certain other natural processes. Thus, it may be present in substantial concentrations both indoors and outdoors. Formaldehyde can cause irritation of the skin, eyes, nose and throat. High levels of exposure may cause some types of cancers (Radford, 2016).

  1. Lead

Lead has long been recognized as a harmful environmental pollutant. Lead is particularly dangerous to children because their growing bodies absorb more lead than adults do and their brains and nervous systems are more sensitive to the damaging effects of lead. Babies and young children can also be more highly exposed to lead because they often put their hands and other objects that can have lead from dust or soil on them into their mouths. Children may also be exposed to lead by eating and drinking food or water containing lead or from dishes or glasses that contain lead, inhaling lead dust from lead-based paint or lead-contaminated soil or from playing with toys with lead paint. Before it was known how harmful lead could be, it was used in paint, gasoline, water pipes, and many other products (Radford, 2016).

Old lead-based paint is the most significant source of lead exposure in the U.S. today. Harmful exposures to lead can be created when lead-based paint is improperly removed from surfaces by dry scraping, sanding, or open-flame burning. High concentrations of airborne lead particles in homes can also result from lead dust from outdoor sources, including contaminated soil tracked inside, and use of lead in certain indoor activities such as soldering and stained-glass making (Spivey & Radford, 2013)

  1. Nitrogen dioxide (NO2)

The two most prevalent oxides of nitrogen are nitrogen dioxide (NO2) and nitric oxide (NO). Both are toxic gases with NO2 being a highly reactive oxidant and corrosive. The primary sources nitrogen dioxide indoors are combustion processes, such as unvented combustion appliances, e.g. gas stoves, vented appliances with defective installations, welding, tobacco smoke and kerosene heaters (Winnick, 2014).

  1. Pesticides

Pesticides are chemicals that are used to kill or control pests which include bacteria, fungi and other organisms, in addition to insects and rodents. Pesticides are inherently toxic. Pesticides can lead to indoor air pollution as a result of contaminated soil or dust that floats or is tracked in from outside, stored pesticide containers, household surfaces that collect and then release the pesticides and through pesticides used in and around the home to control insects (insecticides), termites (termiticides), rodents (rodenticides), fungi (fungicides) and microbes (disinfectants) (Winnick, 2014).

  1. Indoor particulate matter

Particulate matter (also referred to as PM or particle pollution) is a complex mixture of solid and/or liquid particles suspended in air. These particles can vary in size, shape and composition. Once inhaled, particles can affect the heart and lungs and in some cases cause serious health effects (Winnick, 2014).

  1. Secondhand smoke/ environmental tobacco smoke

Secondhand smoke is a mixture of the smoke given off by the burning of tobacco products, such as cigarettes, cigars or pipes and the smoke exhaled by smokers. Secondhand smoke is also called environmental tobacco smoke (ETS) and exposure to secondhand smoke is sometimes called involuntary or passive smoking. Secondhand smoke contains more than 7,000 substances which include arsenic, nicotine, cotinine, carbon monoxide, and other smoke-related chemicals have been found in the body fluids of nonsmokers exposed to secondhand smoke, several of which are known to cause cancer in humans or animals (Winnick, 2014).

  1. Volatile organic compounds

Volatile organic compounds (VOCs) are emitted as gases from certain solids or liquids. VOCs include a variety of chemicals, some of which may have short- and long-term adverse health effects. Concentrations of many VOCs are consistently higher indoors (up to ten times higher) than outdoors. VOCs are emitted by a wide array of products numbering in the thousands. Organic chemicals are widely used as ingredients in household products. Paints, varnishes and wax all contain organic solvents, as do many cleaning disinfectants, cosmetics and hobby products. Fuels are made up of organic chemicals. All of these products can release organic compounds while you are using them, and, to some degree, when they are stored (Winnick, 2014).

Effects of indoor air pollution

Indoor air pollution can be life threatening for people especially children and old age people who are more prone to the after-effects of indoor air pollution.  Some of the effects of indoor air pollution as identified by Sengler (2011) are as stated below.

  • If asbestos is found in the home, it can cause or lead to very serious health problems such as lung cancer, asbestosis and various other types of cancers.
  • If contaminants such as dust mites or other bacteria get into the home, inhabitant will start to experience asthma symptoms, throat irritation, flu, and other types of infectious diseases.
  • If lead is found in the home it can also be severely life threatening. It can cause brain and nerve damage, kidney failure, anemia, and a defective cardiovascular system.
  • Formaldehyde, one of the most common indoor air pollutants, can also cause health problems. Inhabitants of such homes may experience irritation of the throat, eyes, and nose, as well as allergic reactions. There have been a number of cases where it has also caused cancer.
  • Tobacco smoke causes individuals to experience severe respiratory irritation, pneumonia, bronchitis, emphysema, heart disease, as well as lung cancer.
  • Chemicals such as those that are used in certain cleaning agents and paints can cause you to experience a loss of coordination, liver, brain, and kidney damage, as well as a number of types of cancer.
  • If you use gas stoves in your home it can cause respiratory infections and damage and irritation to the lungs.

Measures to minimize indoor air pollution

In order to promote a health indoor air quality, Sengler (2011) recommended the following measures to minimize indoor air pollution.

  • Smoking is one of the most common cause of indoor air pollution. The best thing to do is to quit smoking and make the home anti-smoking zone. The less smoke that is emitted into the air the less chance of one of the listed effects happening to inhabitants of the home. Smoking is a leading cause of cancer. Lung cancer is the most common form of cancer caused by smoking.
  • Ensure that all materials used for disinfection and cleaning are environmentally friendly.
  • Home should be checked for the presence of asbestos. This is typically done before moving into a new home.
  • The use of gas stoves in the home should be minimized as they are found to release harmful chemicals that could be dangerous to human health.
  • The home should be regularly inspected for any mold, radon, or any other harmful chemical or bacteria that may be in the home. These types of inspections are traditionally done before moving into the home.
  • Use a good vacuum cleaner that has strong brushes to keep out chemicals and allergens that can accumulate in the home. Areas in the home which are most commonly visited must be cleaned thoroughly by using the vacuum several times.
  • Most of the dirt comes into the home from the shoes. So it is important to keep a large mat out of every room that will reduce the amount of dirt, and other pollutants from getting into the home.


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