Beijing is enjoying its best winter air quality in five years, Beijing Youth Daily reported Thursday.

　　据《北京青年报》星期四报道，北京正享受着五年来空气质量最佳的冬天。

　　The yearly average concentrations of particulate matter with a length of 2.5 microns or less, known as PM2.5 and which damage the lungs when inhaled, dropped by 20.5% to 58 micrograms per cubic meter in 2017.

　　2017年，小于或等于2.5微米的颗粒物即PM2.5的年平均浓度下降了20.5%，达到58微克/立方米，呼吸时它会伤害人的肺部。

　　According to the local environment agency, the city has met the national standard of sulfur dioxide density. However, the concentrations of three other major pollutants: carbon dioxide, PM10, and PM2.5, are still out of limits. To improve Beijing’s air quality is still a long-term process.

　　根据当地环保局的说法，北京市已经达到了国家二氧化硫浓度标准。然而，其他三种主要污染物——二氧化碳、PM10和PM2.5的浓度仍然超出了限制值。改善北京的空气质量仍然是一个长期的过程。

　　The number of days during which the air quality was rated “excellent” or “good” was 226, up by 28 compared to 2016, while the number of days when the air was heavily polluted stood at 23, down by 16.

　　空气质量被评为“优秀”或“好”的天数为226天，比2016年增加了28天，而空气污染严重的天数为23天，减少了16天。

　　Over the last five years, the PM2.5 levels of each district in Beijing have experienced significant drops. Li Xiang, an official with Beijing Municipal Environmental Protection Bureau said that Beijing will make more efforts to lower the PM2.5 concentration to 56 micrograms per cubic meter in 2020.

　　在过去的5年里，北京各区PM2.5的值都有显著下降。北京环保局的一名叫李翔的官员说，北京将作出更多的努力，致力于在2020年将PM2.5指数下降到56微克/立方米。