Beijing's air quality improved significantly from 2014 to 2018 due to the Air Pollution Prevention and Control Action Plan. Pollution levels dropped for most pollutants, except O3. The plan led to fewer deaths from PM2.5 and O3, especially in densely populated areas like Haidian and Chaoyang districts. The most vulnerable groups, like children and the elderly, should take extra precautions on high pollution days. Overall, the plan has been effective in reducing air pollution and improving public health in Beijing.