Indoor air pollution: What causes it and how to tackle it

This article has been updated.

Most people think of air pollution as something that comes from factories or motor vehicles. However, did you know that the air inside your home or place of work can also be polluted? In fact, indoor air pollution can be even more harmful to your health than outdoor air pollution.

Indoor air pollution is created by the release of harmful pollutants inside. These can include fine particulate matter (PM), carbon monoxide and various other toxins.

And it's a big problem in developing countries, where people often burn fuels indoors for cooking and heating. It is also a concern for people living in energy-efficient homes. These properties tend to be relatively airtight, meaning that the air inside can quickly become stagnant and pollutant levels can rise rapidly.

And while pollution in all forms can be harmful, indoor air pollution is particularly pernicious because people are often steeped in it for long periods of time. In 2020, it was linked to approximately 3.2 million deaths globally, including 237,000 children under five, according to the World Health Organization (WHO).

There are many causes of indoor air pollution. Some are readily recognized due to their smell, but many others go undetected.

The smoke from cigarettes, cigars, and pipes is one of the most common – and most dangerous – indoor air pollutants. Tobacco smoke contains more than 7,000 chemicals, including at least 70 that are carcinogenic. When inhaled, these chemicals can also cause chronic obstructive pulmonary disease and other cardiovascular diseases that result in heart attacks and other serious consequences.

Secondhand tobacco smoke is another a major indoor air pollutant. In fact, secondhand smoke exposure is estimated to cause about 7,300 lung cancer deaths in non-smoking adults in the United States each year.

Further, some reports suggest that tobacco smoke causes 10 times more air pollution than diesel car exhaust, making it one of the most severe indoor air pollution sources.

Another common indoor air pollutant is PM from cooking stoves. In developing countries, solid fuels such as wood, coal, and dung are often burned indoors for cooking and heating.

Exposure to high levels of PM from indoor cooking stoves has links to a variety of health problems, including respiratory infections, asthma, heart disease and cancer. In fact, indoor air pollution from cooking stoves is responsible for approximately 3.1 million premature deaths each year, primarily women and children, the United Nations says.

The chemicals in many cleaning products can pollute indoor air. These chemical products release toxic fumes, which can be harmful when inhaled. Some of these chemicals have been linked to a variety of health problems, including respiratory infections, asthma, and cancer.

In addition, many cleaning products contain volatile organic compounds (VOCs), gases that can easily evaporate at room temperature. When VOCs are released into the air, they can cause various short- and long-term health effects, including headaches, nausea, and damage to the liver, kidney and central nervous system.

Mould is an indoor air pollutant that can cause myriad health problems, including respiratory infections, asthma, and allergies. It grows in damp and humid environments and can be found in a variety of places in the home, such as on walls, floors, ceilings and basements.

Moreover, for those with weakened immune systems or pre-existing conditions like asthma or allergies, mould exposure can exacerbate illnesses and cause serious respiratory infections.

Pet dander is another common indoor air pollution source. Dander can be found in animals' fur, skin and saliva and is shed by most animals with fur. When pet dander is released into the air, it can be inhaled and cause various respiratory problems, including asthma attacks, hay fever, and other allergies.

Dust is a significant contributor to poor indoor air quality, containing allergen sources and airborne pollutants that can negatively impact health. As outlined above, these microscopic particles, including dust mites, mould spores and pet dander, can worsen existing respiratory conditions and contribute to a number of other health issues.

As people spend increasing amounts of time indoors, including in places of work and education, and on transport, monitoring air quality becomes even more important. Indoor dust, for example, can also contain traces of heavy metals from sources like outdoor dust, furniture and cigarette smoke. Reducing dust can improve lung health and minimize exposure to harmful indoor air pollutants.

It might seem like indoor air pollution is an impossible problem to solve, but there are ways to reduce pollutant levels.

One of the main ways to reduce indoor air pollution is by ensuring proper ventilation. Proper ventilation helps remove polluted indoor air and replace it with fresh, clean air from outside.

When indoor spaces are not adequately ventilated, pollutants can build up to dangerous levels. This is especially a concern in homes that are sealed tight to conserve energy.

Inadequate ventilation can also lead to a build-up of carbon dioxide, which can cause health problems, including headaches, dizziness, and fatigue.

High-efficiency particulate air (HEPA) filters can reduce indoor pollution, effectively removing pollutants like mould spores, pet dander, dust mites, and tobacco smoke. In fact, HEPA filters remove 99.97% of airborne particles that are 0.3 microns or larger from the air that passes through them.

The filters can be used in various ways, including in vacuums, air purifiers, and in heating and air conditioning systems.

Many conventional cleaning products contain harmful chemicals that cause indoor air pollution. To avoid this, choose green cleaners made with natural ingredients like white vinegar, baking soda, borax, citrus fruit, and essential oils.

These natural ingredients are safe for indoor use and are effective at cleaning surfaces and removing dirt, dust, and grime.

Keeping indoor space clean and dry can help reduce indoor air pollution. This is especially important in areas where mould and mildew tend to grow, such as in the kitchen and bathroom. Additionally, it's crucial to promptly repair any leaks or water damage to prevent mould and mildew from growing.

Keeping indoor plants is an effective way to reduce indoor pollutants. Indoor plants help to purify the air by absorbing contaminants and releasing oxygen. Additionally, indoor plants help to improve indoor air quality by increasing humidity and reducing dust levels.

Moreover, the effectiveness of indoor plants to purify indoor air has been backed by NASA, the US space agency. In 1989, the agency conducted a clean air study and found that certain indoor plants were highly effective at removing a variety of pollutants from the air. These include English ivy, pothos, bamboo palm and peace lily plants, among others.

When building or renovating indoor spaces, choosing low-emitting building materials and furnishings is important. These materials and furnishings emit lower levels of volatile organic compounds (VOCs), harmful chemicals that can pollute indoor air.

Some low-emitting materials and furnishings include bamboo, wool carpets, and latex paint.

An air purifier can provide protection against indoor air pollution, eliminating pollutants like dust, pollen, mould spores and pet dander. They can also remove VOCs, carbon monoxide, and other harmful chemicals.

While choosing an air purifier, it's important to select one that is the right size for the room and has a high CADR rating. The CADR rating indicates the unit's ability to clean the air in a given space. To determine the correct CADR, divide your space square footage by 1.55. Let's assume you have a 250-square-foot room. Divide this number by 1.55, and you'll get a figure 161, indicating that you'll need a room air purifier with a CADR of 160 or higher.

The future of indoor air pollution control lies in the hands of technology. Currently, several air purifiers on the market use cutting-edge technology to remove indoor air pollutants.

Further, indoor air pollutants can now be detected with more precise, efficient and compact sensors thanks to advances in environmental sensing technology. As a result, intelligent home systems use sensors like these to keep track of indoor air quality and notify the ventilation system before dangerous levels are reached.

In the future, indoor air pollution may also be controlled through nanotechnology, which works by trapping or destroying indoor contaminants on a molecular level. This technology is already being developed for air purifiers and can potentially remove indoor pollutants at a much smaller scale than current methods.

Innovation is never limited; new and more effective ideas and inventions can be developed to combat indoor air pollution. Today, however, steps can be taken to ensure indoor air pollution is limited. A critical aspect of this effort is addressing air pollution on a global scale. Launched at COP26 by the World Economic Forum, Clean Air Fund and Stockholm Environment Institute, the Alliance for Clean Air brings together business leaders to prioritize air quality, reduce emissions and drive impactful action in the climate movement.