[Spatial and Temporal Distribution Characteristics of Ozone Concentration and Population Health Benefit Assessment in the Yangtze River Delta Region from 2017 to 2020].

In recent years, the ozone (O) concentration has showed a rising trend in China, becoming second only to PM as an important factor affecting air quality. To grasp the spatial-temporal variations characteristics of O and the associated health impacts during the implementation of the three-year plan on defending the blue sky in the Yangtze River Delta (YRD) region, data collected from 210 monitoring stations in the YRD from 2017 to 2020 were analyzed using the global Moran's index and Getis-Ord index methods, and the associated health benefits of reduced O exposure were evaluated using the health risk and environmental value assessment methods. The results showed that during the study period, the interquartile range (IQR) of the annual average O concentration and that of the warm season both presented a declining trend. The average O concentrations in both warm and cold seasons showed a similar spatial distribution pattern, with the northern part exhibiting the higher concentrations and the southern part showing the lower concentrations. Furthermore, the O concentrations in the warm season were characterized by high O concentrations clustering in the northern and central part of the region. The proportion of the population exposure to annual average O concentration over 160 μg·m decreased from 72.3% in 2017 to 34.8% in 2020 in the YRD. Although the population-weighted annual mean O concentration in the whole YRD region showed a downward trend, some cities in western Anhui province, northern Jiangsu province, and central Jiangsu province showed fluctuations and even an increasing trend. In terms of health benefits, there were 3782 cases (95% CI:2050-5511 cases) of avoided premature deaths associated with reduced O concentrations in the warm season in 2020 compared to 2017. The total health benefit was 26198 million yuan (95% CI:14201-38175 million yuan). Compared to the cost of the main O precursor emission reduction, the cost-benefits ratio was 1:1.67 to 3.23.