Future impacts of O₃ on respiratory hospital admission in the UK from current emissions policies

Exposure to ambient ozone (O₃) O₃ is associated with impacts on human health. O₃ is a secondary pollutant whose concentrations are determined inter alia by emissions of precursors such as oxides of nitrogen (NO_x) and volatile organic compounds (VOCs), and thus future health burdens depend on policies relating to climate and air quality. While emission controls are expected to reduce levels of PM_2.5 and NO₂ and their associated mortality burdens, for secondary pollutants like O₃ the picture is less clear. Detailed assessments are necessary to provide quantitative estimates of future impacts to support decision-makers. We simulate future O₃ across the UK using a high spatial resolution atmospheric chemistry model with current UK and European policy projections for 2030, 2040 and 2050, and use UK regional population-weighting and latest recommendations on health impact assessment to quantify respiratory emergency hospital admissions associated with short-term effects of O₃. We estimate 60,488 admissions in 2018, increasing by 4.2%, 4.5% and 4.6% by 2030, 2040 and 2050 respectively (assuming a fixed population). Including future population growth, estimated emergency respiratory hospital admissions are 8.3%, 10.3% and 11.7% higher by 2030, 2040 and 2050 respectively. Increasing O₃ concentrations in future are driven by reduced nitric oxide (NO) in urban areas due to reduced emissions, with increases in O₃ mainly occurring in areas with lowest O₃ concentrations currently. Meteorology influences episodes of O₃ on a day-to-day basis, although a sensitivity study indicates that annual totals of hospital admissions are only slightly impacted by meteorological year. While reducing emissions results in overall benefits to population health (through reduced mortality due to long-term exposure to PM_2.5 and NO₂), due to the complex chemistry, as NO emissions reduce there are associated local increases in O₃ close to population centres that may increase harms to health.