| | | | 1952 12 | | | | | | | | | | | | 40 | | | | | 1956 | | | | | | | | | | | | 2003 | | | | 100 90 | 10 | | | | | 2008 4 | | PM2.5 | 2020 | 2010 20% | 2010 | 25 | 2015 | | | 2000 15% | | | 1990 | 1997 | PM2.5 | PM2.5 | | | | | | | | | |