Skip to content

Data Provider: Welsh Government Air Quality Indicators, by Local Health Board
Click here to sortNO2Click here to sortPM10Click here to sortPM2-5
Aneurin Bevan University Health Board373825
Abertawe Bro Morgannwg University Health Board313523
Cardiff and Vale University Health Board514127
Cwm Taf University Health Board293624
Hywel Dda University Health Board183120
Betsi Cadwaladr University Health Board213020
Powys Teaching Health Board132919


Air Quality Exposure Indicators

Last update
December 2018 December 2018

Next update
November 2019

Publishing organisation
Welsh Government

Source 1
Air Concentration, Department for Environment, Food and Rural Affairs

Source 2
Small area population estimates (SAPE), Office for National Statistics

Source 3
Geographical information, Welsh Government

Contact email


Lowest level of geographical disaggregation
Local authorities

Geographical coverage

Languages covered
English and Welsh

Data licensing
You may use and re-use this data free of charge in any format or medium, under the terms of the Open Government License - see

General description
Air Quality Exposure Indicators - average 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)

Data collection and 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.

The Welsh Government has used this published data to assign a concentration of NO2, PM2.5 and PM10 to each residential dwelling in Wales based on which square kilometre of Wales it sits in.

For each census output area (statistical geographic units comprising around 150 properties), the pollutant concentrations associated with each dwelling within it were averaged 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.

Frequency of publication

Data reference periods
Annual average

Users, uses and context
Information is used for local area air quality management and monitoring.

Rounding applied
Population weighted concentrations are rounded to the nearest whole number (µg/m3).

Revisions information

Air quality, pollution, air concentration

Statistical quality
See weblinks.
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.