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Description
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Average micrograms (μg) of NO2 at residential dwelling locations per m3 (Future Generations Indicator 4). The UK Government’s Pollution Climate Mapping (PCM) model calculates average pollutant concentrations for each square kilometre of the UK. The Welsh Government has used this data to assign an average concentration of NO2, PM2.5 and PM10 to each residential dwelling in Wales based on which square kilometre of Wales it sits in. Air quality will vary within any given square kilometre, depending on proximity to busy roads and other sources of air pollution. Therefore, these assigned values should not be taken to be correct for any individual dwelling. For each Local Authority and Local Health Board, the Welsh Government has calculated a population-weighted average over its constituent census output areas to give an average NO2, PM2.5 and PM10 concentration based on where people live in those Local Authorities or Health Boards and 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. |
