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Modelled exposure to particulate matter air pollution

Based on ground measurements, satellite retrievals of aerosol optical depth, chemical transport models and population data, exposure estimates (as known as population-weighted concentration) for particulate matter are derived at country level. The exposure estimates are available for the 194 WHO Member States, and breakdown for urban and rural areas is also provided.

Exposure estimates at urban levels are reported as SDG 11.6.2.

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Indicator name:
Air pollution: concentrations of fine particulate matter (PM2.5), SDG 11.6.2
Short name:
Annual mean PM2.5 concentration
Topic:
Risk factors
Rationale:
Air pollution consists of many pollutants, among other particulate matter. These particles are able to penetrate deeply into the respiratory tract and therefore constitute a risk for health by increasing mortality from respiratory infections and diseases, lung cancer, and selected cardiovascular diseases. Mean annual concentration of fine suspended particles of less than 2.5 microns in diameters (PM2.5) is a common measure of air pollution. The mean (population-weighted average) annual concentration of PM2.5 in urban areas has been chosen as the SDG indicator 11.6.2.
Definition:
The mean (population-weighted average) annual concentration of fine suspended particles of less than 2.5 microns in diameters, expressed in micrograms per cubic meter [migrograms/m3]. For SDG indicator 11.6.2: The mean (population-weighted average) annual concentration of fine suspended particles of less than 2.5 microns in diameters, specifically in urban areas.
Disaggregation:
The PM2.5 concentrations are geographically classified according to the 2021 UNSD Degree of Urbanization classification: cities, towns and rural areas. Data is also provided for urban (aggregation of cities and towns) and all (aggregation of cities, towns and rural) areas.
Method of measurement
Concentration of PM2.5 are regularly measured from fixed-site, population-oriented monitors. High-quality measurements of PM concentration from all the monitors can be averaged to develop a single estimate. Concentration of PM2.5 are regularly measured from fixed-site,  population-oriented monitors located within the metropolitan areas. High-quality measurements of PM concentration from all the monitors in the metropolitan area can be averaged to develop a single estimate.  
Method of estimation:
Although PM is measured at many thousands of locations throughout the world, the amount of monitors in different geographical areas vary, with some areas having little or no monitoring. In order to produce global estimates at high resolution (0.1◦ grid‐cells), additional data is required. Annual mean concentration of PM2.5 is estimated with improved modelling using data integration from satellite remote sensing, population estimates, topography and ground measurements.
Method of estimation of global and regional aggregates:
The regional and global aggregates are population -weighted figures of the national estimates. Cagg=SUM (Cnat * Pnat)/ SUM (Pnat) where Cagg is the regional/global estimate, Cnat is the national estimate, Pnat is the country population. The sum is done over the countries in the region (regional aggregate) or all countries (global aggregate).
Preferred data sources:
Special studies
Unit of Measure:
Micrograms per cubic meter [micrograms/m3]
Expected frequency of data dissemination:
Every 2-3 years
Expected frequency of data collection:
Every 2-3 years
Comments:
Sources of data include ground measurements from monitoring networks, collected for 6,000 cities and localities (WHO 2022) around the world, satellite remote sensing, population estimates, topography, information on local monitoring networks and measures of specific contributors of air pollution (WHO, 2022)
Contact person email:
bonjourso@who.int
Name:
Sophie Gumy
IMRID:
4674
Limitations:
Urban/rural data: while the data quality available for urban/rural population is generally good for high-income countries, it can be relatively poor for some low- and middle income areas. Furthermore, the definition of urban/rural may greatly vary by country.
Links:
Data Integration Model for Air Quality: A Hierarchical Approach to the Global Estimation of Exposures to Ambient Air Pollution
Ambient air pollution: a global assessment of exposure and burden of disease
WHO Air quality Database 2022
Air quality database
Indicator Metadata Registry List
Indicator 11.6.2: Annual mean levels of fine particulate matter (e.g. PM2.5 and PM10) in cities (population weighted) SDG Indicator 11.6.2 Concentrations of fine particulate matter (PM2.5)
Contact information for general inquiries: aqh_who@who.int