Impacts of net zero policies on air quality in a metropolitan area of the United Kingdom: Towards world health organization air quality guidelines
Jian Zhong, James Robert Hodgson, William J. Bloss, Zongbo Shi
Abstract
Climate change and air pollution are closely interlinked since carbon dioxide and air pollutants are co-emitted from fossil fuel combustion. Net Zero (NZ) policies aiming to reduce carbon emissions will likely bring co-benefits in air quality and associated health. However, it is unknown whether regional NZ policies alone will be sufficient to reduce air pollutant levels to meet the latest 2021 World Health Organisation (WHO) guidelines. Here, we carried out high resolution air quality modelling for in the West Midlands region, a typical metropolitan area in the UK, to quantify the effects of different NZ policies on air quality. Results show that NZ policies will significantly improve air quality in the West Midlands, with up to 6 μg m−3 (21%) reduction in annual mean NO2 (mostly through the electrification of vehicle fleet, EV) and up to 1.4 μg m−3 (12%) reduction in annual mean PM2.5 relative to levels expected in 2030 under the “business as usual” (BAU) scenario. Under 2030 BAU, PM2.5 concentrations in most wards would be below 10 μg m−3 whilst under the Net Zero scenario, those in all wards would be below 10 μg m−3. This means that West Midlands would meet the UK PM2.5 target a decade early under the Net Zero scenario. However, no ward-level-averaged annual mean PM2.concentrations meet the 2021 WHO Air Quality guideline level of 5 μg m−3 under any scenario. Similarly for NO2 only 18 wards (8% of the region's population) have predicted NO2 concentrations below the 2021 WHO guideline level (10 μg m−3). Decarbonisation policies linked to Net Zero deliver substantial regional air quality benefits, but are not in isolation sufficient to deliver clean air with pollutant levels low enough to meet the 2021 WHO guidelines.