Air Quality database Update 2026 (Version Eight)
Released on 30 June 2026 – 8th edition (V8.0)

 The WHO Ambient Air Quality Database compiles ground-level measurements of annual mean concentrations for nitrogen dioxide (NO₂), and particulate matter with a diameter equal to or smaller than 10 μm (PM₁₀) and 2.5 μm (PM_2.5). These measurements aim to represent an average for the city or town, rather than for individual monitoring stations.

Both groups of pollutants originate mainly from human activities related to fossil fuel combustion. To ensure the data accurately reflects population exposure, the database primarily utilizes urban measurements, encompassing urban background, residential, commercial, and mixed areas, as well as rural and industrial zones close to urban settlements.

• Frequency: Updated regularly every 2–3 years since 2011.
• Impact: This data serves as the primary input to derive Sustainable Development Goal (SDG) Indicator 11.6.2 (Air quality in cities), for which WHO is the custodian agency.
• Primary Sources: Official national and subnational datasets provided by countries upon request, official reports, and government websites. For European Union members, data is sourced from the European Environment Agency (EEA). 

This version of the database (V8.0, released in June 2026) currently hosts data from 8 023 human settlements in 127 WHO Member States, WHO Associate Members or WHO Territory or Areas, for the period 2010-2024. 

Limitations

While the database provides critical insights, data comparability between different countries is limited due to the following factors:

• Coverage and Accessibility Gaps: The database is not comprehensive. It captures only a small fraction of cities in some countries, and certain existing data could not be accessed due to language barriers or limited availability.
• Methodological and Quality Differences: There is large heterogeneity in measurement methods, techniques, and data quality across regions. Additionally, some data points may lack sufficient documentation to fully verify their compliance with inclusion criteria.
• Spatial and Temporal Variations: Measurements are localized (city averages are based on ground stations) and temporal coverage varies. Data spanning only part of the year may significantly deviate from the true annual mean due to seasonal variability.

How this data is used

The WHO Ambient Air Quality Database serves these critical functions:

✅ Advancing Air Pollution Exposure Modeling: It provides foundational input for complex models—combining ground measurements with topographic, population, satellite data, and chemical transport models—to accurately estimate global air pollution exposure. This modeling framework ensures homogeneous and standardized exposure estimates across all countries, regardless of local monitoring capacity.

✅ Driving Advocacy and Transparency: It raises awareness about the vital importance of open-access, high-quality data, while actively advocating for the expansion and improvement of air monitoring networks worldwide.

✅ Quantifying the Global Health Burden: It acts as a cornerstone for calculating the mortality and morbidity burdens attributed to air pollution. WHO estimates that outdoor air pollution caused 4.3 million premature deaths in 2021 due to stroke, ischaemic heart disease, lung cancer, chronic obstructive pulmonary disease and acute lower respiratory infections.

How this data is not used

To ensure the database is used accurately and responsibly, it should not be used to:

❌️ Rank the most polluted cities: The database is not designed to create city rankings, as monitoring capacities and data completeness vary significantly between locations.

❌️ Draw direct comparisons between countries: Differences among monitoring networks, and measurement methodologies make direct cross-country comparisons misleading.