, changes in pm concentrations of less than 0.25 eg/m3 ) , in both 2010 and 2020 , but more substantial improvements for a large percentage of the population , including improvements in excess of 2 eg/m3 for more 到 2020. 年 的 人数 超过 2.4万 人 .
很 大 一部分 人口 看到 pm 浓度 有 了 显着 改善 .