Air Quality

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Next update expected:August 2026

Updates

31st October 2025
Dataset first published.

Main information

Designation
No designation
Data provider 1
Department for Environment, Food and Rural Affairs
Data source 1
Air concentration
Data provider 2
Welsh Government
Data source 2
Geographical information
Data provider 3
Office for National Statistics (ONS)
Data source 3
Small Area Population Estimates (SAPE)

Overview

Summary of dataset and variables

Air Quality Exposure Indicators - average, population weighted NO2, PM2.5 and PM10 concentrations across local authority areas and health board areas, derived from modelled data for each square kilometre in Wales, measured in µg/m3 (DEFRA data)

µg/m3 = microgrammes per cubic metre NO2 = Nitrogen Dioxide PM10 = fine particulate matter with a diameter of 10 micrometers or less PM2.5 = fine particulate matter with a diameter of 2.5 micrometers or less

Data collection or calculation

Each year the UK Government’s Pollution Climate Mapping (PCM) model calculates average pollutant concentrations for each square kilometre of the UK. The model is calibrated against measurements taken from the UK’s national air quality monitoring network.

This data is combined with mid-year population data and dwelling data to provide population weighted data.

For each census output area (statistical geographic units comprising around 150 properties), the pollutant concentrations are weighted by the number of dwellings in each square kilometre to give an average NO2, PM2.5 and PM10 concentration across the census output area.

For each Local Authority and Local Health Board, a population-weighted average over its constituent census output areas were calculated to give an average NO2, PM2.5 and PM10 concentration based on where people live in those Local Authorities and Health Boards. The same calculation was also repeated over all census output areas, to give a comparable figure for the whole of Wales.

Statistical quality

Each year the Pollution Climate Model (PCM) which underpin the background maps is refined and improved ( to account for latest available science and understanding e.g. changes in emissions factors, improved activity data etc.). These method changes are usually only applied in the latest year's figures. See Defra Air Quality report.

2021 air quality figures are based on 2020 population estimates. 2023 air quality figures are based on 2022 population estimates.

Rounding applied

whole number

Related reports

Published by

Organisation
Welsh Government
Contact email
stats.environment@gov.wales