The global state of air pollution.

Air pollution is the greatest environmental threat to public health globally and accounts for more than 8 million premature deaths every year. Air pollution and climate change are closely linked as all major pollutants have an impact on the climate and most share common sources with greenhouse gases. Improving our air quality will bring health, development, and environmental benefits. The UNEP Pollution Action Note displays the global state of air pollution, major sources, the impact on human health, and national efforts to tackle this critical issue.

With every breath we take, we suck in tiny particles that can damage our lungs, hearts, and brains and cause a host of other health problems. The most dangerous of these particles, which can include anything from soot, soil dust, to sulfates, are fine particles 2.5 microns (µ) or less in diameter —shortened as PM2.5.

In 2021, in response to increases in quality and quantity of evidence of air pollution impacts, the WHO updated the PM2.5 annual mean air quality guideline to 5µg/m3, which represents clean air as few impacts have been observed below these levels. The update halves the previous 2005 guideline level of 10µg/m3. On the way to that level, the agency also sets a series of interim targets, air pollutant concentrations that serve as steppingstones. They are meant for areas where air pollution is high, so governments in those areas can develop policies to reduce air pollution that are achievable within realistic time frames.

Even though air pollution is a global problem, it disproportionately affects those living in developing nations and particularly the most vulnerable, such as women, children and the elderly.

Residential pollution, mostly from cooking and heating using biomass, and generating electricity from fossil fuels for our homes, and transport, are the main human-made sources of fine particles globally.

PM2.5 is emitted through multiple sources. These fine particles that pollute our air mostly come from human activities such as burning fossil fuels to generate electricity, transportation, waste burning, agriculture — a major source of methane and ammonia -- and the chemical and mining industries. Natural sources include volcanic eruptions, sea spray, soil dust, and lightning.

In developing countries, reliance on wood and other solid fuels, like raw coal for cooking, heating and lighting, and the use of kerosene for lighting, increases air pollution in homes. Windblown dust is also a major source in portions of Africa and West Asia that are close to deserts.

Contribution of each sector to fine particle pollution

Human activities have contributed the most to the emission of air pollutants. Understanding the breakdown of PM2.5 sources helps policymakers, scientists, and communities take targeted action to reduce pollution and its impacts on health, climate, and ecosystems.

Over four million seven hundred thousand people died in 2021 from exposure to fine particulate outdoor air pollution, with the highest death rates occurring in West Asia and Africa. Around 2.4 billion people use polluting fuels for cooking and heating, and around 3.2 million people die early each year from household air pollution.

Rising temperatures increase the frequency of wildfires all around the world, which in turn further elevate levels of particulate air pollution.

Air pollution is a major global health crisis and causes one in nine deaths worldwide. Exposure to PM2.5 reduced average global life expectancy by approximately one year and eight months in 2021.

The deadliest illnesses linked to PM2.5 air pollution are stroke, heart disease, lung disease, lower respiratory diseases (such as pneumonia), and cancer. High levels of fine particles also contribute to other illnesses, like diabetes, can hinder cognitive development in children and also cause mental health problems.

Exposure to fine particle outdoor air pollution is the second largest risk factor for premature death globally behind only high blood pressure, and the single largest environmental risk factor for premature death globally. Air pollution exposure contributes to a number of key illnesses globally but its contribution is not borne equally across the world. For example, people living in low- and middle-income countries today are exposed to between one to four times higher levels of air pollution than those living in high-income countries. Children are particularly vulnerable to the damaging health effects of air pollution due to their unique susceptibility and exposure. 26 percent of newborn deaths globally are attributed to air pollution exposure.

Policy actions

Today, 95% of the world’s population lives in a country that is party to an international agreement specifically targeting air pollution.

Air pollutants can travel across borders and impact the air quality and ecosystems of neighboring countries, not just where they originate. Air pollution doesn’t just jeopardize our health and well-being: it contributes massively to climate change, threatens food security, and makes city inhabitants unsafe. This challenge cannot be addressed through local action alone. Regional cooperation is also required to sustainably combat the scourge of dirty air.

From West Asia, Southeast Asia, to the African continent and even the Arctic, more and more regions are addressing this shared emergency, particularly by integrating monitoring, reporting, and knowledge sharing of experience and good practices.

Still, more must be done to ensure that these agreements are implemented effectively and that all countries have the resources to develop knowledge, tools, ground-based observations, and data to reduce air pollution.