根据生态和环境部的数据，今年9月，中国338个城市的空气质量同比有所改善。
The air quality in 338 Chinese cities improved year-on-year in September, according to the Ministry of Ecology and Environment.
根据中国生态环境部的数据，今年9月，中国338个城市的空气质量同比有所改善。
The average density of PM 2.5 stood at 25 micrograms per cubic meter in September, down 16.7 percent from the same period last year.
9月份PM2.5的平均浓度为每立方米25微克，比去年同期下降了16.7%。
A total of 338 cities enjoyed good air quality on 90.8 percent of days last month, up 2.6 percentage points year-on-year, according to the ministry.
根据生态环境部的数据，共有338个城市在上个月90.8%的时间里空气质量良好，同比增长2.6个百分点。
In the Beijing-Tianjin-Hebei region, the share of days with good air quality in September stood at 79.2 percent, a year-on-year increase of 27.8 percentage points, while the PM 2.5 density of the region dropped by 33.3 percent year-on-year to 36 micrograms per cubic meter.
在京津冀地区，9月份空气质量良好的天数为79.2%，同比增长27.8个百分点，而该地区的PM2.5浓度同比下降了33.3%，降至每立方米36微克。
In the first three quarters of this year, seven out of 20 cities with the worst air quality were in northern China’s Shanxi Province.
今年前三个季度，20个空气质量最差的城市中有7个位于中国北部的山西省。
In July, China released a three-year action plan on air pollution control.
今年7月，中国发布了一项为期三年的空气污染控制行动计划。
According to the action plan, by 2020, emissions of sulfur dioxide and nitrogen oxide should have dropped by more than 15 percent compared with 2015 levels, while cities that fail to meet the requirement of PM 2.5 density should see a decline of more than 18 percent from 2015 levels.
根据该行动计划，到2020年，二氧化硫和氮氧化物的排放量将比2015年下降15%以上，而未能达到PM2.5密度要求的城市的排放量将要求比2015年下降18%以上。
Meanwhile, cities at prefecture level and above should see their numbers of good air days reach 80 percent annually and the percentage of heavily polluted days decrease by more than 25 percent from 2015 levels.
与此同时，地级及以上城市每年的空气质量好日数应达到80%，重度污染日的百分比2015年减少25%以上。
