Indoor air pollution is a major yet overlooked global health threat, linked to 3.2 million premature deaths annually and affecting people across both high- and low-income regions.

Everyday indoor activities, such as cooking, heating and cleaning, can release harmful pollutants, especially in poorly ventilated or tightly sealed spaces, impacting physical and mental health.

Improving indoor air quality requires urgent, coordinated action on cleaner energy access, better building infrastructure, affordable monitoring tools and equal regulatory focus as outdoor air.

When we think of air pollution, we usually picture the outdoors, from urban traffic to industrial emissions. Despite significant advances in managing outdoor air pollution, a critical dimension of exposure that remains underestimated is the air we breathe indoors.

The stark reality is that many people, particularly vulnerable individuals and children, are exposed to the highest concentrations of air pollutants indoors, in spaces typically considered safe.

On average, people spend between 60–90% of their time indoors, while exposure to indoor air pollution is linked to an estimated 3.2 million premature deaths annually worldwide. Researchers have found that everyday activities, such as cooking, heating and cleaning, release harmful levels of airborne pollutants, including greenhouse gases, into homes.

These indoor sources of air pollution remain poorly understood and are hard to address. Moreover, they pose measurable risks to health, including respiratory disease, sleep health and cognitive performance. Despite this, indoor air quality receives far less regulatory attention and public discussion than outdoor air.

If most of our lives are spent indoors, then the air inside our homes, schools and workplaces must be safe to breathe, which is why clean indoor air should be part of the global health conversation.

“ As people spend most of their time indoors, indoor environments can be the main contributor to people’s individual exposure to air pollution. ”

Failing to address this means leaving behind the very people at risk, especially children, the elderly and low-income communities.

A global problem

Indoor air pollution is a global problem. It affects communities everywhere, whether living in a rural village cottage or a high-rise apartment block. Your daily activity, building infrastructure and especially the type of fuel used to cook and heat your home all impact the indoor air quality.

Although the sources of indoor air pollution may vary between the Global North and South, the issue of indoor air pollution has been consistently overlooked worldwide.

In the Global South, the burden of indoor air pollution is particularly heavy. A combination of structural and financial barriers, limited public awareness and restricted access to cleaner energy alternatives create additional barriers to promoting healthy air.

Over 3 billion people rely on solid fuels for cooking and heating in low- and middle-income countries, according to 2018 estimates. This reliance is particularly prominent in sub-Saharan Africa and South Asia, where a large portion of households often burn wood, charcoal and other forms of solid fuels indoors using traditional or basic stoves, which are highly polluting.

The State of Global Air 2020 report highlights the scale of this issue: around 80% of the population in parts of sub-Saharan Africa and nearly 60% in South Asia are regularly exposed to seriously poor indoor air.

Studies linked to the United States, Europe and the United Kingdom reveal a similar problem of poor indoor air. Energy-efficient modern homes and buildings that rely on cleaner fuels still pose a significant problem.

Interestingly, the problem occurs in well-insulated homes and buildings, where limited ventilation traps air pollutants generated by everyday activities, such as cooking, heating, cleaning, smoking and even using home laser printers, allowing indoor pollution levels to accumulate.

Gas cooking and heating are particularly a growing concern in modern indoor spaces, linked to air pollutant levels that are two to twelve times higher than those in outdoor air.

As people spend most of their time indoors, indoor environments can be the main contributor to people’s individual exposure to air pollution. Moreover, air pollutants such as particulate matter, volatile organic compounds and nitrogen dioxide are incredibly complex and diverse; and they react amongst themselves and with their environment.

This makes understanding indoor environments even more challenging and easier to overlook.

Exposure to these pollutants creates a multidimensional burden, affecting physical health and daily well-being, while also contributing to economic and social challenges.

This extends to mental health issues, where growing evidence links it to anxiety and depression, especially among vulnerable populations. These burdens can lead to increased medical bills and directly affect individual productivity and social well-being.

Opportunities for action

While the problem is complex and overlooked, there are opportunities to address indoor air pollution but such action demands multidimensional efforts, from changing individual behaviour to upgrading infrastructure and advancing policy:

Making indoor air monitoring more affordable and accessible: Monitoring indoor air quality is not easy and traditionally, has required expensive tools. Emerging Monitoring indoor air quality is not easy and traditionally, has required expensive tools. Emerging low-cost sensors and smart internet of things (IoT) devices have proven a remedy. While the accuracy and reliability of new tools are still a question, given their early stage of technological evolution, they remain promising for expanding access to indoor air quality data and informing much-needed interventions.

Cultural and behavioural considerations: Cultural habits further obscure the problem. Cultural habits further obscure the problem. Cooking over open flames or wood burning is still popular, especially, in the latter case, where electricity costs are high. Shifting behaviour will require not only public education but also cultural sensitivity, respecting tradition while promoting cleaner energy options.

Transition to clean energy: Adopting clean energy solutions such as electric cooking or clean heating systems remains challenging due to high upfront costs and limited infrastructure, even when cleaner technologies are available. We need to shift from awareness to action. Clean energy solutions must be affordable, accessible and reliable. This requires expanding financing options, strengthening supply chains and demonstrating how technologies can be integrated into daily life.

Improving infrastructure: Poor ventilation is a common issue in many homes and buildings, allowing indoor pollutants to accumulate over time. Addressing this problem requires infrastructure improvements at regulatory and design levels. While challenging in various regions due to a lack of policy attention, financial limitations and practical difficulties in upgrading buildings, setting clear ventilation standards and supporting basic improvements can help improve indoor spaces.

View indoor and outdoor air with equal regulatory priority: Indoor environments continue to receive far less policy priority than the outdoors, which remains a key challenge in addressing the issue effectively. Closing this gap requires making indoor air a clear policy priority and integrating it into health and environmental strategies. Without equal focus on indoor environments, efforts to improve air quality and protect public health will remain challenging.