Car exhaust. Factory smoke. Wildfire haze. Chances are, no matter where on Earth you live, you’re exposed to some form of air pollution almost every day.
The consequences of this pollution can be debilitating – and deadly. Air pollution caused 8.1 million premature deaths in 2021 alone, found one prominent study.
On Sunday, September 7, 2025, the world celebrated the International Day of Clean Air for blue skies, which showcases solutions to air pollution. The theme this year is “Racing for Air”, which reflects the urgent need to address what United Nations Secretary-General, António Guterres, has called a “global emergency.” It is also a nod to the growing support for clean air among sports associations.
Designated by the United Nations General Assembly in 2019, the day aims to strengthen international cooperation in improving air quality and reducing air pollution, recognising the critical importance of clean air for human health and the environment. It emphasises the need for collective efforts from governments, corporations, and individuals to address air quality issues and promote sustainable practices.
“Just like athletes, we all need clean air to move, perform and thrive,” says Steven Stone, the Deputy Director of the Industry and Economy Division of the United Nations Environment Programme (UNEP). “Clean air supports healthy people, resilient communities, strong economies and a healthier planet.”
As the world commemorates the International Day of Clean Air, here’s a look at what air pollution is, why it’s harmful and what can be done about it.
- Air pollution comes in many forms
There are two main types of air pollution: indoor and outdoor.
Indoor air pollution comes chiefly from the burning of wood, charcoal, animal dung and other so-called “solid fuels” which are used by billions around the world for cooking. When these fuels are set ablaze, they release microscopic specs of dust, soot and black carbon, which are collectively known as fine particulate matter.
Outdoor air pollution comes from an array of sources, including factories, motor vehicles – even forest fires and dust storms. Experts say the most concerning pollutants are:
- PM 10 and its smaller cousin PM 2.5, two types of fine particulate matter that often spring from the burning of fossil fuels;
- carbon monoxide, an odourless gas that commonly comes from the combustion of wood, kerosene and charcoal;
- ground-level ozone, a major component of smog that is created when sunlight comes into contact with certain gasses; and
- nitrogen dioxide and sulfur dioxide, two compounds often produced by fossil-fuel-burning factories and vehicles.
- Air pollution is everywhere
Ninety-nine per cent of people on Earth breathe air the World Health Organisation considers polluted.
- Air pollution is terrible for human health
Particles less than 10 microns in size – also known as PM10 – can penetrate deep into the lungs, causing inflammation and damaging the lining of the respiratory tract. PM2.5 is even more problematic. These particles are small enough to enter the bloodstream, where they can affect every organ in the body. Air pollution has been linked to a range of serious health problems, including pneumonia, heart disease, stroke, lung cancer and stillbirths.
- Air pollution can be deadly
In 2021, air pollution led to more than 8.1 million premature deaths, found a study by the non-profit Health Effects Institute. That is more than one in eight deaths worldwide. More than 700,000 of the fatalities were in children under five.
- Air pollution can make popular pastimes, like playing sports, impossible.
Air pollution has imperiled major sports events everywhere from Canada to India, with spiking levels of contaminants like PM2.5 posing a risk to players. That’s in part why sports governing bodies have joined the push for cleaner air, including World Athletics, which sanctions track and field events. It has installed air quality sensors around stadiums to detect poor air quality, especially risky to runners.
- Air pollution feeds the climate crisis
Many of the same substances that make people sick also trap heat near the Earth’s surface, stoking climate change. In fact, research suggests these so-called super pollutants – which include methane and black carbon – are responsible for a large percentage of global warming to date.
- Reducing air pollution can save lives and help achieve the Sustainable Development Goals (SDGs)
The 17 goals are humanity’s blueprint for a better future and several hinge on reducing air pollution. Reining in airborne toxins can, obviously, help improve public health (SDG3). It can also counter poverty (SGD1) by allowing workers to be more productive and reducing the number of lost work days. It can help reduce inequalities (SDG10) because vulnerable groups, including children and the elderly, tend to suffer the most from dirty air. Tackling air pollution can even help counter hunger (SDG2). One common airborne pollutant, ground-level ozone, inhibits the growth of crops.
- Ending air pollution requires international cooperation
Air pollutants can travel across borders, with ozone and some types of particulate matter capable of radiating out hundreds or thousands of kilometres from their source. That’s why experts say the only way to tackle air pollution at scale is for countries to share their knowledge, align their strategies and mobilize their resources in partnership with each other.
- Air pollution is avoidable
Since air pollution comes in many forms, there is no one-size-fits-all solution. But there are some simple, cost-effective things cities and countries can do to begin to address the problem. Those include:
- build robust air pollution monitoring systems to inform data-driven policies and early warning systems;
- leverage global data and reliable science to make decisions to protect human health;
- share real-time air quality data with the public in an easy-to-understand way;
- limit emissions from known sources of pollution through laws and regulations;
- map out the economic benefits of addressing air pollution, which often far exceed the costs; and
- strengthen the institutions designed to address air pollution.
Businesses and individuals also have an important role to play in the campaign against air pollution, says UNEP’s Stone.
“We’re going to need everyone pulling together if we’re going to win the race to clean air,” he says.
A recent report from the World Bank found that integrated policies targeting the heating, cooking, transportation, agriculture and waste sectors could halve the number of people globally exposed to dangerously high levels of air pollution.
- The United Nations is working hard to counter air pollution
The UN has spent decades helping countries, cities and communities tackle this crisis. Partnerships among key stakeholders have been powerful in supporting efforts to beat air pollution. Those initiatives include the Climate and Clean Air Coalition and BreatheLife.
The UN has also come together under the Common Approach to a Pollution-Free Planet. This framework is designed to help UN bodies collectively address pollution challenges through their respective mandates, thus leading to more impact, with the goal of ensuring a clean, healthy, sustainable environment for everyone on Earth.
