Bronte Wells
Air pollution is often thought of as an outdoor issue, but the air inside buildings can also be polluted. In fact, indoor air pollution is a serious threat to human health, causing millions of deaths each year. Pollutants that originate outdoors can enter buildings through open doors, windows, ventilation systems, and cracks in structures. They can also be brought in on shoes and clothing. Common outdoor pollutants include smoke, car exhaust fumes, and industrial emissions. Indoor sources of pollution include combustion sources such as tobacco smoke, wood and coal heating, and cooking appliances, which can release harmful byproducts like carbon monoxide directly into the indoor environment. Other indoor sources include cleaning supplies, paints, and building materials.
| Characteristics | Values |
|---|---|
| Common indoor pollutants | Carbon monoxide, radon, smoke, vapors, mold, volatile organic compounds, asbestos, dust mites, pet dander |
| Common outdoor pollutants | Smoke, volatile chemicals, radon, pollen, dust, allergens |
| Health effects of indoor pollutants | Irritation of eyes, nose, and throat, headaches, dizziness, fatigue, respiratory diseases, heart disease, lung cancer, asthma |
| Factors affecting indoor air quality | Ventilation, temperature, humidity, occupant behavior, building materials, human activities, natural origin |
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What You'll Learn
Indoor air pollution sources
One of the primary sources of indoor air pollution is the release of gases or particles from combustion sources. This includes tobacco smoke, wood or coal-heating and cooking appliances, fireplaces, and gas stoves that can emit harmful combustion byproducts such as carbon monoxide, nitrogen oxide, and particulate matter. Inadequately maintained or unvented combustion appliances, such as wood stoves or chimneys, can also release noxious substances like hydrocarbons.
Building materials and home improvement products are another significant source of indoor pollution. These can release pollutants continuously or through degradation over time. For example, asbestos fibers can be released from building insulation, while pressed wood products can emit chemical off-gassing. Other building materials may support the growth of biological pollutants like mould and mildew, which release disease-causing toxins.
Additionally, common household products contribute to indoor air pollution. Cleaning supplies, paints, insecticides, air fresheners, and personal care products introduce various chemicals, including volatile organic compounds (VOCs), into the indoor air. The increased use of synthetic furnishings and household cleaners has been linked to higher indoor pollutant concentrations.
Human activities, such as smoking, cleaning, redecorating, and hobbies, can also release pollutants intermittently. Furthermore, people, pets, and plants are considered sources of indoor biological pollutants, and their presence can impact the indoor air quality.
Lastly, outdoor air pollution can infiltrate indoor spaces through open doors and windows, ventilation systems, or cracks. Weather conditions and occupant behaviour, such as operating air conditioners or heaters, also influence indoor air quality. Inadequate ventilation or high humidity levels can further increase indoor pollutant concentrations.
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Outdoor air pollution sources
Outdoor air pollution is a pressing environmental health issue that affects people in low-, middle-, and high-income countries alike. In 2019, it was estimated to have caused 4.2 million premature deaths worldwide, with 89% of these occurring in low- and middle-income countries. Notably, the WHO South-East Asia and Western Pacific Regions experienced the greatest burden of these premature deaths.
There are numerous sources of outdoor air pollution, and they can be categorized into several groups. One of the significant contributors is vehicle emissions, which release pollutants such as nitrogen dioxide (NO2) into the atmosphere. NO2 is formed during the combustion of fuels, particularly in the transportation sector. Resuspended dust from roadways, which often contains metal particles associated with motor vehicles, is another source of pollution.
Another category of outdoor air pollution sources is industrial and agricultural emissions. These include emissions from agricultural lands, industrial sources, construction sites, and even deserts. Agricultural soils are often contaminated with metals from fertilizer and animal waste, which can become airborne and contribute to air pollution. Similarly, industrial sources and construction sites release pollutants like asbestos and various dusts and chemicals into the atmosphere.
The burning of fossil fuels, especially coal, is another significant contributor to outdoor air pollution. In 2005, it was the largest single source of global GEM emissions, accounting for about 45% of anthropogenic emissions. Additionally, activities such as artisanal/small-scale gold mining (18%) and industrial gold production (5-6%) also contribute significantly to global air pollution.
Other sources of outdoor air pollution include stationary power generation, residential heating and cooking, and the manufacturing, distribution, and use of chemicals. Natural processes, such as terrestrial and aquatic surfaces emitting pollutants, also play a role. Bioaerosols, which are airborne biological particles like bacterial cells, fungal spores, viruses, and pollen, are another source of outdoor air pollution. These can come from various sources, including plants, soil, cooking, and the burning of biological materials.
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Health effects of indoor air pollution
Indoor air pollution is a serious issue, with Americans spending approximately 90% of their time indoors, where the concentration of pollutants is often 2 to 5 times higher than typical outdoor levels. This has a significant impact on health, with certain groups being more vulnerable to the adverse effects. The very young, older adults, and those with pre-existing conditions such as cardiovascular or respiratory disease, are at greater risk and tend to spend more time indoors.
The sources of indoor air pollution are varied and include combustion sources, building materials, and household products. The use of solid fuels, such as wood, coal, or dung for cooking and heating is a major contributor, particularly in low- and middle-income countries. Tobacco smoke, wood-burning stoves, and coal-fired appliances release harmful byproducts such as carbon monoxide, particulate matter, and environmental tobacco smoke. Building materials can also be a source, with asbestos fibers being released from insulation or chemical off-gassing from pressed wood products.
The health effects of indoor air pollution are wide-ranging and can be both short and long-term. Irritation of the eyes, nose, and throat, as well as headaches, dizziness, and fatigue, are common symptoms. More severe health issues include respiratory diseases, heart disease, cognitive deficits, and cancer. Radon, a common indoor air pollutant, is the second-leading cause of lung cancer. Carbon monoxide, another indoor pollutant, can be lethal even in short-term exposure.
The indoor use of polluting fuels and technologies, such as inefficient stoves and open fires, has severe health consequences, especially for women and children, who are typically responsible for household chores. The World Health Organization (WHO) estimates that 3.8 million people die annually from illnesses attributable to harmful indoor air, with exposure to household air pollution being linked to a third of pneumonia cases in children under five.
It is important to address indoor air pollution to protect health and improve the quality of life for those affected. The WHO has issued guidelines for indoor air quality, recommending cleaner fuels and technologies such as solar, electricity, biogas, and natural gas. Implementing these guidelines can reduce exposure to harmful pollutants and mitigate the negative health impacts of indoor air pollution.
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Ventilation and air exchange rates
Ventilation is a critical factor in maintaining good indoor air quality. It helps to reduce indoor air pollution by diluting and removing pollutants released from indoor sources and carrying them out of the indoor environment. Natural ventilation occurs through opened windows and doors, while mechanical ventilation uses fans and ductwork to achieve the same goal. Infiltration, a third type of ventilation, is when outdoor air enters through openings, joints, and cracks in walls, floors, and ceilings.
The rate at which outdoor air replaces indoor air is called the air exchange rate. When there is little ventilation, the air exchange rate decreases, leading to increased pollutant levels. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) recommends a minimum of 0.35 air changes per hour or 15 cubic feet of air per minute per person in residential buildings to maintain acceptable indoor air quality and minimize adverse health effects.
To improve indoor air quality, it is essential to increase the amount of outdoor air coming indoors. This can be achieved through source control, such as sealing off asbestos sources or adjusting gas stoves to reduce emissions, and by utilizing ventilation systems. Opening windows and doors, operating fans, and using air conditioning with the vent control open are simple yet effective ways to increase the outdoor ventilation rate.
However, it is important to be mindful of outdoor air pollution sources, such as nearby highways, factories, or wildfire smoke, as opening windows and doors in such cases may introduce more pollutants indoors. Mechanical ventilation systems, such as energy-efficient heat recovery ventilators, can be employed to bring in fresh outdoor air while mitigating the costs of heating or cooling it.
Additionally, specific locations within a building that produce high levels of pollutants or moisture, such as bathrooms and kitchens, can benefit from outdoor-vented fans that intermittently remove air from these areas, a practice known as "spot ventilation." Overall, a combination of source control, ventilation, and air cleaning techniques is most effective in improving indoor air quality and reducing the health risks associated with indoor air pollutants.
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Strategies to improve indoor air quality
Indoor air quality is critical to health, especially for young children, older adults, and people with existing lung disease. The good news is that there are several low-cost strategies to improve it.
Improve Ventilation
Opening windows and doors for at least 10 minutes daily improves indoor air quality by allowing outdoor air to enter and dilute indoor pollutants. Natural ventilation caused by temperature differences and wind can also be used to improve indoor air quality. However, if outdoor air pollution is high, mechanical ventilation devices, such as outdoor-vented fans or air handling systems, can be used to remove indoor air and distribute filtered and conditioned outdoor air.
Control Sources of Pollution
Indoor pollution sources that release gases or particles are the primary cause of indoor air quality problems. These include combustion sources such as tobacco, wood, and coal heating, which release harmful byproducts like carbon monoxide. Other sources include cleaning supplies, paints, insecticides, building materials, and biological pollutants like dust mites and pet dander. To improve air quality, it is essential to control these sources by, for example, using natural cleaning products, properly maintaining ventilation systems, and keeping homes smoke-free.
Use Air Purifiers and Filters
Air purifiers are portable air cleaners that remove airborne contaminants by drawing in air and passing it through filters. Replacing air filters in heating and cooling systems can also improve airflow and prevent particles from circulating. Using a vacuum with a HEPA filter is also recommended to effectively capture small particles and prevent them from becoming airborne.
Test and Monitor for Pollutants
It is important to test for pollutants such as radon, a naturally occurring radioactive gas that can enter buildings through cracks and gaps and is a known carcinogen. Carbon monoxide alarms should also be installed and regularly tested, as carbon monoxide is a harmful byproduct of combustion sources.
By implementing these strategies, you can significantly improve indoor air quality and create a healthier living environment.
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Frequently asked questions
Radon is an indoor and outdoor pollutant that can cause irritation of the eyes, nose, and throat. Radon forms in the ground as naturally occurring uranium in rocks and soils decay. It can enter buildings through cracks or gaps in structures.
Common indoor pollutants include smoke, vapors, mold, and chemicals used in paints, furnishings, and cleaners. Other sources of indoor pollution include building materials, household cleaners, and biological pollutants such as dust mites and pet dander.
Outdoor air quality can impact indoor air through open doors, windows, ventilation systems, and cracks in structures. Weather conditions, such as temperature and humidity, can also affect indoor air quality by influencing the use of windows, air conditioners, humidifiers, or heaters.
