Indoor Air Pollution: Where Is It Most Dangerous?

Indoor air pollution is a significant problem worldwide, with around 2.1 billion people cooking with solid fuels and inefficient stoves, which generate harmful pollutants. This issue disproportionately affects low-income households and countries, where cleaner fuels may be unavailable or unaffordable. Indoor air pollution has severe health implications, including respiratory diseases, heart disease, pneumonia, stroke, and lung cancer. It is also a trigger for asthma and can cause or worsen lung diseases. The World Health Organization (WHO) has addressed this issue by developing guidelines for indoor air quality and providing recommendations on clean fuels and technologies. Despite progress in some countries, indoor air pollution remains a critical challenge, especially for the poorest communities globally.

Indoor air pollution in low-income countries

Indoor air pollution is a significant issue in low-income countries, with solid fuel use being closely linked to poverty. Around 2.1 billion people worldwide, mostly from low- and middle-income countries, cook using open fires or inefficient stoves fuelled by wood, charcoal, coal, kerosene, animal dung, crop waste, and other biomass. This practice generates harmful household air pollution, which was responsible for an estimated 3.2 million deaths per year in 2020, including over 237,000 children under the age of five. The pollution exposure leads to non-communicable diseases, including stroke, ischaemic heart disease, chronic obstructive pulmonary disease (COPD), and lung cancer. Women and children, who typically carry out household chores like cooking and collecting firewood, bear the brunt of the health consequences from the use of polluting fuels and technologies.

The World Health Organization (WHO) has issued guidelines for indoor air quality and household fuel combustion, aiming to provide recommendations on clean fuels and technologies to protect health. These guidelines discourage the use of kerosene and unprocessed coal and emphasize addressing all household energy uses, especially cooking, space heating, and lighting. However, despite the efforts of governments, multinational companies, and non-governmental organizations to promote improved stoves and clean fuels, there is limited evidence of health benefits from these programs.

The health effects of indoor air pollution are significant, including irritation of the eyes, nose, and throat, headaches, dizziness, fatigue, and more severe issues such as respiratory diseases, heart disease, and cancer. Radon, a common indoor air pollutant, is the second-leading cause of lung cancer. Carbon monoxide, another indoor pollutant, is toxic, and elevated levels can be lethal in the short term. The Legionella bacterium, found in poorly maintained heating and plumbing systems, can cause Legionnaires' disease, a form of pneumonia.

Addressing indoor air pollution in low-income countries requires a systematic approach to research and policymaking, recognizing the link between poverty and the dependence on polluting fuels. It is crucial to develop sustainable solutions that are affordable and desirable for families with limited incomes, such as clean cooking technologies. By improving access to cleaner alternatives and implementing health-based guidelines, the health and environmental impacts of indoor air pollution in low-income countries can be mitigated.

Indoor air pollution in poorly ventilated dwellings

Indoor air pollution is a critical issue, as most people spend a significant amount of time indoors, at home or in the workplace. Poor ventilation is a major contributor to indoor air pollution, especially in outdated buildings. Poor ventilation refers to the insufficient exchange of fresh air between indoor and outdoor locations, leading to stagnant air and a buildup of air pollutants.

In poorly ventilated dwellings, indoor smoke and pollutant levels can be significantly higher than in well-ventilated spaces. The use of solid fuels, such as wood, crop waste, charcoal, coal, and dung, as well as kerosene in open fires and inefficient stoves, generates harmful household air pollution. This is particularly prevalent in low- and middle-income countries, where around 2.1 billion people rely on these fuels for cooking. The resulting household air pollution has severe health impacts, causing approximately 3.2 million premature deaths annually, including the deaths of over 237,000 children under five years old.

The incomplete combustion of solid fuels and kerosene releases particulate matter and other pollutants, including volatile organic compounds (VOCs), carbon monoxide (CO), carbon dioxide (CO2), and fine particulate matter (PM2.5). These pollutants have adverse effects on health, including respiratory problems, eye irritation, headaches, dizziness, nausea, and in extreme cases, even death. Fine particulate matter is particularly dangerous as it penetrates deep into the lungs and can lead to heart disease.

The impact of poor ventilation is not limited to physical health but can also affect mental well-being. High temperatures and humidity, combined with stagnant air and pollutants, can create an uncomfortable and stressful environment. Additionally, poor ventilation can lead to condensation and mould growth, triggering allergic reactions and other health issues.

To improve indoor air quality and protect occupants' health, it is essential to ensure proper ventilation. This can be achieved through natural ventilation, such as opening windows, or mechanical ventilation systems that use fans or blowers. The World Health Organization (WHO) also provides guidance and strategies to promote the adoption of cleaner household fuels and technologies, such as access to clean cooking alternatives and improved ventilation or housing design.

Indoor air pollution and health effects

Indoor air pollution is a significant issue, particularly in low- and middle-income countries, where around 2.1 billion people cook with solid fuels such as wood, charcoal, and coal on open fires or inefficient stoves. This generates harmful pollutants, including small particles that penetrate the lungs and enter the bloodstream. Poor ventilation in dwellings can exacerbate the problem, with indoor smoke levels reaching 100 times higher than acceptable standards.

The health effects of indoor air pollution are wide-ranging and severe. Short-term exposure to elevated carbon monoxide levels, for example, can be lethal. Other pollutants, such as radon, are known human carcinogens, causing lung cancer. Indoor air pollution has also been linked to respiratory diseases, heart disease, stroke, ischaemic heart disease, chronic obstructive pulmonary disease (COPD), and lung cancer. Exposure to indoor air pollution during pregnancy has been associated with impaired lung function in infants, and it may also increase the risk of developing pneumonia in the first year of life.

Certain groups are more vulnerable to the adverse effects of indoor air pollution. Women and children, who typically spend more time near the domestic hearth and are responsible for household chores such as cooking and collecting firewood, bear a disproportionate health burden. Additionally, those who are very young, older adults, or have pre-existing cardiovascular or respiratory conditions, tend to spend more time indoors and are more susceptible to the health impacts of indoor air pollutants.

The sources of indoor air pollution are diverse. They include combustion sources such as tobacco smoke, wood-burning fireplaces, and coal heating appliances, which release harmful byproducts like carbon monoxide directly into the indoor environment. Cleaning supplies, paints, insecticides, and building materials also contribute to indoor air pollution by releasing various chemicals and volatile organic compounds. Natural sources, such as radon, which enters buildings through cracks or gaps in foundations, and mould, are also significant contributors to indoor air pollution.

The World Health Organization (WHO) has issued guidelines for indoor air quality and household fuel combustion to address the negative health impacts of indoor air pollution. These guidelines provide recommendations on clean fuels and technologies, such as solar, electricity, biogas, and liquefied petroleum gas (LPG), to protect health and reduce pollution.

Common indoor air pollutants

Indoor air pollution is a serious threat to human health, causing millions of deaths each year. The World Health Organization (WHO) estimates that around 2.1 billion people worldwide cook using open fires or inefficient stoves fuelled by wood, kerosene, animal dung, crop waste, or coal, which generates harmful household air pollution. This is particularly prevalent in low- and middle-income countries, with a higher percentage of people in rural areas relying on these polluting fuels and technologies compared to those in urban areas.

Indoor air pollution sources that release gases or particles into the air are the primary cause of indoor air quality problems. These sources can be both indoor and outdoor, with outdoor air pollutants entering buildings through open doors, windows, ventilation systems, and cracks in structures. Some common indoor air pollutants include:

• Radon: A naturally occurring gas that can enter buildings through cracks or gaps in foundations. It is a known human carcinogen and the second leading cause of lung cancer.
• Carbon Monoxide: A toxic gas released by combustion sources such as tobacco, wood, and coal heating and cooking appliances. Short-term exposure to elevated levels of carbon monoxide can be lethal.
• Particulate Matter: Small particles released into the air from combustion sources and cooking activities that can penetrate deep into the lungs and enter the bloodstream.
• Volatile Organic Compounds (VOCs): Released from various products and materials, including cleaning supplies, paints, and building materials.
• Biological Pollutants: Such as dust mites, mold, pet dander, and cockroaches, which can be triggered by excessive moisture indoors.

It is important to address indoor air pollution to protect human health and improve indoor air quality. Strategies include proper ventilation, using cleaner fuels and technologies, and maintaining combustion appliances and ventilation systems.

Reducing indoor air pollution

Indoor air pollution is most problematic in low- and middle-income countries, where around 2.1 billion people cook using solid fuels such as wood, charcoal, coal, and dung. This is particularly an issue for women and children, who spend the most time near the domestic hearth. In 2020, household air pollution was responsible for an estimated 3.2 million deaths per year, including over 237,000 children under the age of five.

To reduce indoor air pollution, the World Health Organization (WHO) has developed guidelines for indoor air quality and household fuel combustion. These guidelines offer recommendations on the types of fuels and technologies that protect health, such as discouraging the use of kerosene and unprocessed coal. Additionally, the WHO emphasizes the importance of addressing all household energy uses, particularly cooking, space heating, and lighting, to ensure benefits for health and the environment.

• Improve ventilation: Opening windows and doors, when the weather permits, can help improve indoor air quality by increasing the exchange of indoor and outdoor air. Advanced ventilation systems, such as energy-efficient heat recovery ventilators, can also be installed to bring outdoor air into the home while mitigating the cost of cooling and heating.
• Eliminate sources of pollution: The most effective way to improve indoor air quality is to eliminate individual sources of pollution or reduce their emissions. For example, sealing or enclosing sources that contain asbestos, or adjusting gas stoves to decrease emissions.
• Minimize the use of certain products: Air fresheners, strongly scented products, and cleaning products with pine or citrus scents can react with ozone to form particles and formaldehyde. Products that make surfaces stain-and water-repellent may contain per- and polyfluoroalkyl substances (PFAS).
• Use safer alternatives: Choose cleaning products that are safer for human health and the environment. Look for products that are formaldehyde-free, such as solid wood, gypsum board, stainless steel, adobe, bricks, and tiles.
• Prevent mould and moisture: Keep moisture levels down by using a dehumidifier and cleaning the filter regularly. Control moisture to prevent mould, and be careful not to overwater indoor houseplants, as damp soil can promote the growth of microorganisms.
• Ban smoking indoors: Secondhand smoke impairs respiratory health and is responsible for about 3,000 lung cancer deaths per year in nonsmokers. Keep your home and car smoke-free.
• Maintain ventilation systems: Properly maintain and use your ventilation system, including local exhaust fans, to help remove pollutants from indoor sources.
• Choose building materials carefully: When purchasing building materials or furnishings, look for labels that indicate low emissions, such as California Phase II Compliant or TSCA Title VI Compliant.
• Test for radon: Radon is a known human carcinogen and the second leading cause of lung cancer. Test for radon in your home and fix high levels.

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