Network Updates / Global / 2022-09-30

How is air quality measured?:
What tools are available

A look at measurment tools and policy options for air quality

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Air quality across the globe continues to deteriorate due to increasing emissions, threatening human health and contributing to climate change, biodiversity loss, and pollution and waste.

According to the World Health Organization, 99 per cent of the global population breathes unclean air, and air pollution causes 7 million premature deaths a year. PM2.5, which refers to particulate matter with a diameter equal to or less than 2.5 micrometres, poses the greatest health threat and is often used as a metric in legal air quality standards. When inhaled, PM2.5 is absorbed deep into the bloodstream and linked to illnesses such as stroke, heart disease, lung disease and cancer.

To address this air pollution crisis, experts warn that governments must take urgent action to strengthen air quality regulation, including monitoring capacity to track PM2.5 and other pollutants.

2021 report from the United Nations Environment Programme (UNEP) found that air quality monitoring is not a legal requirement in 37 per cent of countries, and experts are concerned about the rigour of monitoring in many others.

“Air quality monitoring and transparent access to data through platforms as the World Environment Situation Room, is critical for humanity as it helps us understand how air pollution impacts people, places and planet,” says Alexandre Caldas, UNEP’s Chief of Big Data, Country Outreach, Technology and Innovation Branch.

“Using this data, governments and countries can identify air pollution hotspots and take targeted action to protect and improve human and environmental well-being and our future,” he adds.

So how is air quality measured? How is this data processed? And what can governments do to improve monitoring?

How is air quality measured?


A screenshot of an air quality map
Real-Time Air Pollution Exposure in Kenya. Credit: UNEP


Air pollutants come from a variety of sources, including human-caused emissions – like fossil fuel use in vehicles and cooking – and natural sources, such as dust storms and smoke from wildfires and volcanoes.

Air quality monitors are outfitted with sensors designed to detect specific pollutants. Some use lasers to scan particulate matter density in a cubic metre of air, while others rely on satellite imaging to measure energy reflected or emitted by the Earth.

Pollutants tied to human and environmental health impacts include PM2.5, PM10, ground-level ozone, nitrogen dioxide and sulfur dioxide. The greater the density of pollutants in the air, the higher the Air Quality Index (AQI), a scale that runs from zero to 500. An AQI of 50 or below is considered safe, while readings above 100 are deemed unhealthy. According to UNEP partner IQAir, only 38 of 117 countries and regions averaged healthy AQI readings in 2021.

How is air quality calculated?

Air quality databanks process readings from governmental, crowd-sourced, and satellite-derived air quality monitors to produce an aggregated AQI reading. These databases may weigh data differently based on reliability and the type of pollution measured.

UNEP, in collaboration with IQAir, developed the first real-time air pollution exposure calculator in 2021. It combines global readings from validated air quality monitors in 6,475 locations in 117 countries, territories, and regions. The database prioritizes PM2.5 readings and applies artificial intelligence to calculate nearly every country’s population exposure to air pollution on an hourly basis.

How can governments improve monitoring?

Air quality monitoring is particularly sparse in Africa, Central Asia, and Latin America, even though these regions are densely populated, meaning people may be disproportionately impacted by air pollution. Governments must adopt legislation that makes monitoring a legal requirement while investing in existing infrastructure to improve data reliability. In the interim, integrating the use of low-cost air quality monitors will improve air quality management in developing nations, says Caldas.

“Low-cost air quality monitors are easier to deploy and come with a significant reduction in operational costs, making them an increasingly viable public alternative in areas that lack government-operated stations, as well as in remote regions,” he added.

UNEP is responsible for analyzing the state of global air pollution initiatives and providing early warning information to promote international cooperation on the environment. For example, UNEP has supported the deployment of 48 low-cost sensors across Kenya, Costa Rica, Ethiopia and Uganda since 2020. UNEP is also aiming to provide technical support to over 50 countries, including Senegal, Botswana, Argentina and Timor Leste.

“UNEP is committed to expanding its air quality monitoring expertise to help countries address the air pollution crisis,” says Caldas. “Governments must also make concerted efforts to bolster air quality management to protect the health and well-being of people around the world.”


To fight the pervasive impact of pollution on society, UNEP launched #BeatPollution, a strategy for rapid, large-scale and coordinated action against air, land and water pollution. The strategy highlights the impact of pollution on climate change, nature and biodiversity loss, and human health. Through science-based messaging, the campaign showcases how transitioning to a pollution-free planet is vital for future generations.