Air Quality Indicators
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2007Metadata
- High level information
- Keywords
- Statistical quality information
- Summary information
- Weblinks
- Open Data
Title
Air Quality Exposure IndicatorsLast update
August 2024Next update
2025Publishing organisation
Welsh GovernmentSource 1
Air Concentration, Department for Environment, Food and Rural AffairsSource 2
Small area population estimates (SAPE), Office for National StatisticsSource 3
Geographical information, Welsh GovernmentContact email
stats.environment@gov.walesDesignation
NoneLowest level of geographical disaggregation
Local authoritiesGeographical coverage
WalesLanguages covered
English and WelshData 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 http://www.nationalarchives.gov.uk/doc/open-government-licenceKeywords
Air quality, pollution, air concentrationStatistical 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.
2021 air quality figures are based on 2020 population estimates.
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.
For the 2022 update of the air quality national indicators, a methodological improvement was implemented to the way in which the dwelling weights are calculated, as the original process used for estimating the air quality national indicators (prior to 2022) was not calculating the weights in the way intended. An assessment of the impact on the historic data has been undertaken and the impact is small. Given that the air pollution data is modelled and the population estimates are subject to rebasing following the Census, there is existing uncertainty associated with these estimates. Due to this uncertainty, the lack of detailed historic dwelling data and the small impact of the methodological change, the historic data has not been revised.
