A study analyzing surface ozone trends in China from 2013 to 2017 reveals that while anthropogenic emissions decreased, ozone levels increased in megacity clusters, particularly in the North China Plain. This increase is attributed to a significant reduction in fine particulate matter (PM2.5), which slowed the sink of hydroperoxy (HO2) radicals, thereby stimulating ozone production. The study used a multiple linear regression model to separate meteorological and anthropogenic influences on ozone trends. It found that decreasing PM2.5 had a more significant impact on ozone trends than changes in nitrogen oxides (NOx) or volatile organic compounds (VOCs) emissions, especially in the North China Plain. The study also highlights the importance of understanding aerosol chemistry and its effects on ozone production. While reducing NOx and VOC emissions is necessary to counteract the effects of decreasing PM2.5, a combination of emission controls is needed to achieve effective ozone reduction. The findings emphasize the need for continued efforts to reduce PM2.5 levels in China to improve public health and air quality.A study analyzing surface ozone trends in China from 2013 to 2017 reveals that while anthropogenic emissions decreased, ozone levels increased in megacity clusters, particularly in the North China Plain. This increase is attributed to a significant reduction in fine particulate matter (PM2.5), which slowed the sink of hydroperoxy (HO2) radicals, thereby stimulating ozone production. The study used a multiple linear regression model to separate meteorological and anthropogenic influences on ozone trends. It found that decreasing PM2.5 had a more significant impact on ozone trends than changes in nitrogen oxides (NOx) or volatile organic compounds (VOCs) emissions, especially in the North China Plain. The study also highlights the importance of understanding aerosol chemistry and its effects on ozone production. While reducing NOx and VOC emissions is necessary to counteract the effects of decreasing PM2.5, a combination of emission controls is needed to achieve effective ozone reduction. The findings emphasize the need for continued efforts to reduce PM2.5 levels in China to improve public health and air quality.