Air Quality database Updates 2023/2024 (Version Sixth)

The WHO Ambient Air Quality Database compiles data on ground measurements of annual mean concentrations of nitrogen dioxide (NO₂), particulate matter of a diameter equal or smaller than 10 μm (PM₁₀) or equal or smaller than 2.5 μm (PM_2.5) which aim at representing an average for the city or town as a whole, rather than for individual stations. Both groups of pollutants originate mainly from human activities related to fossil fuel combustion. In order to present air quality data that represent human exposure, we used mainly urban measurements, comprising urban background, residential areas, commercial and mixed areas or rural areas and industrial areas close to urban settlements.

The database is updated regularly every 2-3 years since 2011. The data compiled in this database is used as input to derive the Sustainable Development Goal Indicator 11.6.2, Air quality in cities, for which WHO is custodial agency. The primary sources of data were official countries reports sent to WHO upon request, official national and subnational reports, national and subnational websites that contain measurements of PM₁₀, PM_2.5 or NO₂.

Update 2024 (minor) – Released on 31 Jan 2024 – 6th edition (V6.1)

The Sixth version of the database (V6.1), also called Update 2024 (minor) was realized in January 2024 and currently hosts data from 7 182 human settlements in more than 120 member states.

This version does not contain new data compared to V6.0 released in May 2023 and has been further analyzed and processed to ensure quality and consistency.

Limitations

Data from different countries are of limited comparability because of:

• The coverage is not comprehensive and only captures a small fraction of cities in some countries
• Omission of data which are known to exist, but which could not yet be accessed due to language issues or limited
  accessibility
• The measure is localized (city average are an average of ground measurement stations)
• Large heterogeneity of measurement methods and techniques
• Different temporal coverage of certain measurements included: if only part of the year was covered, the measurement may significantly deviate from the annual mean due to seasonal variability
• Possible inclusion of data which were not eligible for this database due to insufficient information to assess compliance
• Heterogeneous quality of measurements

What it can do:

✅️ serve as input data in models to estimates air pollution exposure with topographic, population and satellite data together with chemicals transport models among other.

✅️ contribute to advocate for better monitoring of air quality everywhere

✅️ acknowledge growing effort of the number of monitoring stations around the world

✅️ raise awareness about the importance for publicly available data and of high quality

✅️ serve as a building block to calculate the mortality and morbidity of air pollution- according to the latest World Health Organization estimates, 4.2 million died in 2019 due to breathing bad air quality. 4.2 million that developed cardiovascular diseases like stroke or heart disease, lung cancer or COPD.

What it cannot do:

❌️ draw direct comparison between countries

❌️ rank the most polluted cities

Ideally, the monitoring data used to calculate the average annual PM and NO₂ concentrations should be collected throughout the year, for several years, to reduce bias owing to seasonal fluctuations or to a non-representative year. Care should be taken that the monitors used are not unduly influenced by a single source of pollution (i.e. a power plant, factory or highway); rather, the monitors should reflect exposures over a wide area. Although it is likely that PM and NO₂ data will be available only for larger cities, residents of agglomerations of less than 100 000 inhabitants and of rural areas are also exposed to PM and NO₂ from local industrial activity, transportation, biomass fuels, open burning and regional haze.

Update 2023 – Released on 15 May 2023 – 6th edition (V6.0) [Superceded]

The Sixth version of the database, also called Update 2023 was released in May 2023 and currently hosts data on air quality for over 8 600 human settlements in more than 120 member states.