Indoor Air Quality: Is It Worse Than We Think?

Indoor air pollution is a serious issue, causing approximately 3.2 million deaths globally each year, according to the World Health Organization. The air inside homes and buildings can be more polluted than the outdoor air in industrialized cities, and people spend approximately 90% of their time indoors, increasing the risk to health. Indoor air pollution is caused by various sources, including combustion, building materials, household products, central heating and cooling systems, and outdoor sources such as radon and pesticides. Inadequate ventilation can also increase indoor pollutant levels by not bringing in enough outdoor air to dilute emissions and carrying indoor air pollutants out. Certain groups, such as the young, elderly, and chronically ill, are more susceptible to the harmful effects of indoor air pollution, which can cause respiratory infections, asthma, heart disease, and cancer.

Indoor air pollution sources

Indoor air pollution is a serious issue, with indoor air potentially being more polluted than outdoor air in large industrialized cities. People spend approximately 90% of their time indoors, so the health risks from indoor air pollution are significant. Indoor pollution sources that release gases or particles into the air are the primary cause of indoor air quality problems in homes.

There are many sources of indoor air pollution, including combustion sources such as building materials and furnishings, household cleaning and maintenance products, central heating and cooling systems, and outdoor sources such as radon, pesticides, and outdoor air pollution. Building materials and furnishings can include deteriorated asbestos-containing insulation, wet or damp carpet, and cabinetry or furniture made of certain pressed wood products. Products for cleaning, maintenance, and personal care can also contribute to indoor air pollution.

Central heating and cooling systems and humidification devices can also be sources of indoor air pollution. Inadequate ventilation can increase indoor pollutant levels by not bringing in enough outdoor air to dilute emissions from indoor sources and by not carrying indoor air pollutants out. Weather conditions can also influence indoor air quality by affecting whether building occupants keep windows open or closed and whether they operate air conditioners, humidifiers, or heaters.

Outdoor air pollution can also impact indoor air quality, especially in buildings designed to minimize the amount of outdoor air that can "leak" in and out. However, even in ""leaky"" homes, pollutants can build up due to weather conditions that reduce the amount of outdoor air entering the home. Outdoor sources of indoor air pollution include radon, which is a known human carcinogen and the second-leading cause of lung cancer, and pesticides.

Biological sources of indoor air pollution include plants, people, and animals. Contaminated central air handling systems and building materials that support the growth of biological pollutants can also be significant sources. Infectious illnesses, such as influenza, measles, and chickenpox, are transmitted through the air, and molds and mildews release disease-causing toxins.

Outdoor air pollution sources

Outdoor air pollution is a critical 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. The greatest number of deaths were in the WHO South-East Asia and Western Pacific Regions.

There are numerous sources of outdoor air pollution, but the largest contributors can be categorised as vehicle emissions, stationary power generation, industrial and agricultural emissions, residential heating and cooking, re-emission from terrestrial and aquatic surfaces, chemical manufacturing and distribution, and natural processes.

Vehicle emissions, a significant contributor to outdoor air pollution, include not only cars, trucks, and other vehicles that burn fossil fuels, but also planes, ships, and trains. The burning of fossil fuels, particularly coal, is a major source of emissions, and it contributes to the release of harmful pollutants such as nitrogen oxides, sulfur oxides, and carbon monoxide. These emissions can lead to respiratory issues, especially in vulnerable individuals such as children, the elderly, and those with asthma.

Stationary power generation, another major source of outdoor air pollution, includes power plants that burn coal, gas, oil, and biomass, releasing pollutants into the atmosphere. Industrial and agricultural emissions also play a significant role, with agricultural soils often containing metals from fertilisers and animal waste, and industrial sources releasing asbestos and other harmful substances.

Residential heating and cooking practices can also contribute to outdoor air pollution, especially in areas with a high population density. Additionally, natural processes, such as wildfires, flooding, and hurricanes, can create unhealthy air, particularly for individuals with pre-existing lung conditions.

Health effects of indoor air pollution

The World Health Organization (WHO) has issued guidelines for indoor air quality, highlighting the negative impact of household air pollution on health. Indoor air pollution is caused by the use of inefficient and polluting fuels and technologies, such as solid fuels (wood, crop waste, charcoal, coal, and dung) and kerosene, for cooking and heating. These sources release gases and particles that contain a range of health-damaging pollutants, including small particles that can penetrate deep into the lungs and enter the bloodstream.

The health effects of indoor air pollution can be immediate or long-term, and they vary depending on the concentration and duration of exposure, as well as individual factors such as age and pre-existing health conditions. Immediate effects of indoor air pollution can include irritation of the eyes, nose, and throat, headaches, dizziness, and fatigue. These symptoms may be similar to those of a cold or other viral disease, making it difficult to attribute them solely to indoor air pollution. It is important to pay attention to when and where these symptoms occur, as they may fade or disappear when away from the polluted environment.

Long-term exposure to indoor air pollution has been linked to more severe health issues, including respiratory diseases, heart disease, cognitive deficits, and cancer. The WHO estimates that 3.8 million people worldwide die annually from illnesses attributable to harmful indoor air, particularly from dirty cookstoves and fuel. Additionally, prenatal exposure to household air pollution has been associated with an increased risk of developing pneumonia in the first year of life.

Certain groups are more susceptible to the adverse effects of indoor air pollution, including children, older adults, individuals with pre-existing health conditions, and those from low socioeconomic backgrounds. These groups tend to spend more time indoors and may have higher exposure to indoor pollutants due to inadequate ventilation or the use of polluting fuels and technologies.

To mitigate the health effects of indoor air pollution, it is essential to improve indoor air quality by addressing specific sources of pollution, increasing ventilation, and transitioning to cleaner fuels and technologies.

Energy-efficient homes and indoor air quality

The air within homes can be more polluted than the outdoor air in industrialized cities. People spend approximately 90% of their time indoors, and certain groups, such as the young, the elderly, and the chronically ill, are more susceptible to the effects of indoor air pollution. Energy-efficient homes aim to minimize the amount of outdoor air that can "leak" into and out of the home, which may result in higher indoor pollutant levels.

Energy-efficient homes may have special mechanical means of ventilation to compensate for the reduced outdoor air exchange. Ventilation is critical in maintaining healthy indoor air quality by diluting and removing indoor contaminants. Energy-efficient homes may also incorporate air sealing to minimize pathways for pests and outdoor pollutants, such as automobile exhaust from attached garages.

Sources of indoor air pollution in energy-efficient homes can include combustion appliances, building materials, household products, and outdoor sources such as radon and pesticides. For example, improperly adjusted gas stoves or unvented appliances can emit high levels of carbon monoxide. Other sources, like building materials and household products, can release pollutants continuously or intermittently.

To maintain good indoor air quality in energy-efficient homes, it is essential to have proper ventilation and air sealing. ENERGY STAR-certified homes, for instance, are equipped with ventilation systems, exhaust fans, and air filters to improve indoor air quality and remove contaminants. Additionally, education and training on the installation and maintenance of new technology are recommended to ensure optimal indoor air quality and occupant comfort.

Steps to reduce indoor air pollution

Indoor air pollution can be more harmful than outdoor air pollution, and people generally spend 90% of their time indoors. Therefore, it is important to take steps to reduce indoor air pollution. Here are some ways to do so:

Increase Ventilation

Opening windows and doors is an easy way to increase ventilation and promote a good exchange of indoor and outdoor air. Natural ventilation can help improve indoor air quality by reducing pollutants that are indoors. However, if you suffer from allergies, be mindful of the pollen count outdoors before opening windows. Mechanical ventilation devices, such as outdoor-vented fans, can also help remove air pollutants from specific rooms, such as bathrooms and kitchens.

Ban Smoking

Secondhand smoke is responsible for about 3,000 lung cancer deaths per year in nonsmokers. Therefore, it is important to ban smoking indoors to improve indoor air quality and respiratory health.

Maintain Cleanliness

If you have pets, bathe them regularly and wash their bedding to reduce allergy-causing dander. Also, keep pets out of bedrooms. Minimize the use of carpets as they can trap pollutants such as dust mites, pet dander, and mold spores. Use hard-surface flooring instead. Keep moisture levels low to reduce mold growth, and use a dehumidifier, cleaning the filter regularly. Store chemicals, solvents, and pesticides away from living areas, and opt for homemade cleaning products, such as a mixture of white vinegar and water.

Use Clean Energy Sources

Transition to clean energy sources such as solar, electric, biogas, liquefied petroleum gas, and alcohol (e.g., ethanol). These sources are considered clean for health at the point of use. Additionally, cleaner technologies, such as improved stoves and cooking appliances, can reduce harmful emissions.

Monitor Indoor Plants

While houseplants have been suggested to reduce certain chemicals, there is currently insufficient evidence to support this claim. Overly damp soil from over-watering houseplants can promote the growth of microorganisms, which can affect allergic individuals.

Frequently asked questions