China News Service Client, May 15 (Lang Lang) On the 15th, the Ministry of Ecology and Environment held a press conference, and Liu Bingjiang, director of the Atmospheric Environment Department of the Ministry of Ecology and Environment, said that overall, the air quality in the country will be stable in 2019. However, the ozone concentration increased significantly. In 2019, ozone concentration in 337 prefecture-level and above cities nationwide increased by 6.5% year-on-year, and the number of days with ozone as the primary pollutant exceeded 41.8% of the total number of days exceeded, resulting in a loss of 2.3 percentage points year-on-year. Increasing ozone concentration has gradually become an important factor influencing the number of good days after PM2.5.