The client of, June 30, 30, the Ministry of Ecology and Environment held a press conference It was revealed at the meeting that from January 20 to June 6, the average percentage of excellent days in 337 cities above prefecture level was 86.9%, and the proportion of excellent days increased by 4.7 percentage points over the same period last year. The national average concentration of PM2.5 is 34 micrograms/cubic meter, a year-on-year decrease of 15.0%.