Air Pollution's Indoor Threat: What's The Risk?

Air pollution is a leading cause of illness, from asthma to heart disease, stroke, lung cancer, and probably even dementia. While outdoor air pollution has received a lot of attention, indoor air pollution is equally harmful and warrants more scientific attention. According to the World Health Organization, indoor air pollution caused approximately 3.2 million deaths in 2020, with developing countries being the most affected.

Indoor air pollution is caused by various sources, including inefficient and polluting fuels, such as wood, coal, and kerosene, used for cooking and heating. These fuels release harmful pollutants such as fine particulate matter, carbon monoxide, and volatile organic compounds. Inadequate ventilation in energy-efficient homes can further exacerbate the problem by trapping pollutants indoors.

The health impacts of indoor air pollution are significant and vary depending on age, location, underlying health conditions, and other factors. It can trigger asthma attacks, worsen respiratory and lung diseases, increase the risk of respiratory infections, heart disease, stroke, and lung cancer, and affect vulnerable groups such as infants, young children, the elderly, and people with cardiovascular or respiratory issues.

To address indoor air pollution, it is essential to adopt clean fuels and technologies, improve ventilation, and raise awareness about the risks associated with indoor air pollution. Additionally, scientific research and global collaborations are crucial to developing standards, regulations, and interventions to reduce emissions, exposure, and health harms.

Indoor air can be up to 100 times more polluted than outdoor air

There are many sources of indoor air pollution, including outdoor pollution, but the level of indoor pollution depends on how much of a given pollutant is emitted, how hazardous those emissions are, and the ability of the ventilation system to remove the contaminant.

In recent decades, indoor air quality has been significantly affected by the increase in airtightness and lack of ventilation in modern buildings. While making buildings more airtight will make them more energy-efficient, it will also make it much more difficult for poor-quality air to escape.

Common indoor air pollutants

• Tobacco smoke is one of the most common and dangerous indoor air pollutants. It contains over 7,000 chemicals, including at least 70 carcinogens, and is linked to chronic obstructive pulmonary disease and other cardiovascular diseases.
• Particulate matter is a complex mixture of particulate and gaseous components, including sulfates, nitrates, endotoxin, polycyclic aromatic hydrocarbons, and heavy metals. It is especially concerning as it is sometimes inhalable and can affect the lungs and heart, causing serious health effects.
• Volatile organic compounds (VOCs) are gases containing a variety of chemicals, often emitted from liquids or solids. Formaldehyde, a colourless gas with an acrid smell, is one of the most common VOCs and is released from many building materials.
• Nitrogen oxides are associated with combustion sources, such as cooking stoves and heaters.
• Ozone is a powerful oxidising agent mainly produced by photochemical reactions of O2, NOx, and VOCs in the atmosphere.
• Sulfur dioxide is a common gas in the atmosphere, primarily produced by the combustion of fossil fuels.
• Carbon monoxide is mainly produced by combustion processes, such as cooking or heating.
• Carbon dioxide is a well-known constituent of the earth's atmosphere and a major human metabolite.
• Heavy metals are released into the atmosphere through human activities or natural processes. Exposure to heavy metals can have adverse effects on human health, and they are classified as carcinogenic or non-carcinogenic.
• Biological pollutants include biological allergens (e.g. animal dander, pollen, mould spores) and microorganisms (e.g. viruses, fungi, bacteria).

Ways to tackle indoor air pollution

• Ventilation is one of the main ways to reduce indoor air pollution. Proper ventilation helps remove polluted indoor air and replace it with fresh, clean air from outside.
• Air purification technologies can be used to filter and purify indoor air pollutants.
• Choosing low-emitting building materials and furnishings can help to reduce the emission of volatile organic compounds (VOCs).
• Keeping indoor spaces clean and dry can help to reduce indoor air pollution, especially in areas where mould and mildew tend to grow, such as kitchens and bathrooms.
• Indoor plants can help to purify the air by absorbing contaminants and releasing oxygen.

Indoor air pollution is caused by a variety of sources, including cooking with solid fuels, tobacco smoke, cleaning products, mould, and pet dander

Indoor air pollution is a serious issue, causing approximately 3.2 million deaths globally each year, including 237,000 children under the age of five. There are many sources of indoor air pollution, including cooking with solid fuels, tobacco smoke, cleaning products, mould, and pet dander.

Cooking with solid fuels, such as wood, coal, and animal dung, releases harmful pollutants, including fine particulate matter and carbon monoxide, which can cause a range of health problems such as respiratory infections, asthma, heart disease, and cancer. This is particularly prevalent in developing countries, where these fuels are burned indoors for cooking and heating.

Tobacco smoke is another major source of indoor air pollution. It contains over 7,000 chemicals, including at least 70 known carcinogens. Secondhand smoke exposure is especially dangerous and has been linked to thousands of lung cancer deaths in non-smoking adults annually. Tobacco smoke also lingers as third-hand smoke on surfaces, which is difficult to remove and can pose health risks.

Cleaning products can also contribute to indoor air pollution. Many conventional cleaning products release toxic fumes and volatile organic compounds (VOCs) when used, which can cause various health issues, including respiratory infections, asthma, and even cancer.

Mould is another common indoor air pollutant that thrives in damp and humid environments. It can cause respiratory infections, trigger asthma attacks, and lead to allergies. Those with weakened immune systems or pre-existing conditions are particularly vulnerable to the effects of mould exposure.

Lastly, pet dander, which consists of dried skin cells from pets, can be a significant source of indoor air pollution, especially for individuals with allergies. Pet dander can settle on various surfaces and remain airborne for extended periods, triggering respiratory problems such as asthma and hay fever.

It is important to address these sources of indoor air pollution to improve air quality and protect the health of those who spend time indoors.

It can lead to a range of health issues, including respiratory infections, asthma, heart disease, and lung cancer

Indoor air pollution can lead to a range of respiratory issues, including respiratory infections, asthma, heart disease, and lung cancer. Respiratory infections are one of the top five leading causes of death globally, and air pollution increases the risk of infection. For example, increased levels of PM2.5 are associated with higher rates of emergency department visits and hospital admissions for pneumonia.

Additionally, indoor air pollution can trigger asthma attacks. Asthma is a chronic respiratory disease characterised by inflammation and narrowing of the airways, and indoor air pollutants such as second-hand smoke, mould, and pet dander can act as triggers.

Heart disease is another concern, as air pollution can exacerbate existing cardiovascular conditions and increase the risk of heart attacks and strokes. This is particularly true for fine particulate matter (PM2.5), which can increase the risk of cardiovascular events and lead to higher rates of hospitalisation for conditions such as coronary syndrome, arrhythmia, and heart failure.

Lastly, indoor air pollution has been linked to lung cancer. Particle pollution, which includes solid and liquid particles in the air, can cause lung cancer. These particles can be emitted from various sources, including wood stoves, vehicles, and industrial sources. When inhaled, these particles can become trapped deep in the lungs and increase the risk of lung cancer.

Vulnerable groups, such as children, the elderly, and those with pre-existing health conditions, are particularly at risk

Children are more susceptible to the harmful effects of indoor air pollution due to their smaller, still-developing airways and higher breathing rates relative to their size compared to adults. They also have less developed immune systems, making them more vulnerable to infections. Studies have shown that pollutants can disrupt the proper development of the lungs in foetuses and young children, increasing their risk of respiratory diseases, coughs, bronchitis, and asthma. Furthermore, children are more likely to engage in hand-to-mouth activities, increasing their exposure to pollutants.

The elderly are also at heightened risk due to their reduced ability to eliminate chemicals from their bodies as a result of altered physiology and toxicokinetics. While they may be less sensitive to certain irritants, such as eye and nose irritation, they are still more vulnerable to the overall effects of indoor air pollution.

People with pre-existing health conditions, such as cardiovascular and respiratory diseases, are more vulnerable to indoor air pollution. Those with cardiovascular diseases are more susceptible to particles in the air, which can worsen their condition. Similarly, individuals with respiratory diseases, such as asthma, are more sensitive to air pollutants, which can trigger asthma attacks and worsen their symptoms.

Genetic traits, lifestyle, nutrition, and other health problems can also contribute to increased vulnerability to indoor air pollution. For example, individuals with immunodeficiency or allergic rhinitis may experience greater health risks when exposed to indoor pollutants.

It is crucial to consider vulnerable groups when assessing health risks associated with indoor air quality and to address their specific needs through targeted interventions and policies.

Improving indoor air quality can be achieved through proper ventilation, the use of air purifiers, and source control, such as switching to cleaner energy sources for cooking and heating

Improving indoor air quality is essential to protect health and ensure a comfortable living environment. Here are some detailed strategies to achieve that through proper ventilation, the use of air purifiers, and source control:

Proper Ventilation

Ventilation is a critical aspect of maintaining good indoor air quality. It involves increasing the amount of outdoor air circulating indoors, which helps to remove or dilute indoor airborne pollutants. Here are some ways to improve ventilation:

• Open windows and doors: Natural ventilation is an effective way to increase air circulation and moderate indoor temperatures.
• Utilize fans: Window or attic fans, as well as local bathroom or kitchen fans, can be used to exhaust contaminants and increase the outdoor air ventilation rate.
• Mechanical systems: Advanced home designs now feature mechanical systems that bring outdoor air inside. These may include energy-efficient heat recovery ventilators, which help manage the cost of heating or cooling the air.
• Heating, Ventilation, and Air Conditioning (HVAC) systems: Ensure your HVAC system is well-maintained and utilizes outdoor air intakes to introduce fresh air.
• Infiltration: All homes experience some level of infiltration, where outdoor air enters through openings, joints, and cracks. While this can be a source of outdoor pollutants, it also aids in ventilating indoor spaces.

Air Purifiers

Air purifiers, also known as air cleaners, are devices that remove pollutants from the air. They can be highly effective in improving indoor air quality, especially when used alongside proper ventilation. Here are some considerations when using air purifiers:

• Choose the right type: Avoid ozone-generating or electronic air purifiers due to health concerns associated with ozone emissions. Instead, opt for filtering air cleaners equipped with High Efficiency Particulate Air (HEPA) filters, which can remove at least 99.97% of airborne particles with a size of 0.3 microns or larger.
• Select an appropriate model: Consider the size of the room and the Clean Air Delivery Rate (CADR) of the air purifier. The CADR indicates the volume of filtered air delivered per unit of time, and it should be at least two-thirds of the room's area.
• Regular maintenance: All filters need to be replaced as recommended by the manufacturer to ensure optimal performance. Carbon filters, for example, passively absorb Volatile Organic Compounds (VOCs) and should be sealed until installed.

Source Control

Source control is often the most effective and cost-efficient way to improve indoor air quality. It involves eliminating or reducing the emissions from individual sources of pollution. Here are some tips for source control:

• Sealing or enclosing: Certain pollutants, such as asbestos, can be sealed or enclosed to prevent their release into the indoor environment.
• Adjusting emissions: Some sources, like gas stoves, can be adjusted to decrease the amount of emissions they produce.
• Regular cleaning: Dust accumulation can be a significant source of indoor air pollution. Regular cleaning, especially with natural products, can help prevent this.
• Switching to cleaner energy sources: In developing countries, burning solid fuels like wood, coal, or dung for cooking and heating releases harmful pollutants. Switching to cleaner energy sources, such as electricity or LPG, can significantly improve indoor air quality.

Frequently asked questions