Years	NMVOCs	NOX	PM2.5	SO2
1990	100.0	100.0	100.0	100.0
1991	95.8	89.9	95.2	74.5
1992	94.7	78.8	89.6	68.2
1993	92.2	105.4	84.3	78.9
1994	90.7	89.5	80.5	67.6
1995	90.5	72.6	84.1	66.7
1996	90.4	75.4	80.1	67.1
1997	87.4	67.2	70.9	57.4
1998	80.8	67.7	60.3	60.2
1999	77.8	63.4	60.4	57.8
2000	81.4	58.5	57.1	67.0
2001	77.6	59.7	52.0	49.4
2002	77.3	58.1	49.3	47.9
2003	76.2	57.2	50.7	45.3
2004	72.5	53.4	38.5	48.8
2005	70.9	50.9	40.8	54.0
2006	68.8	58.1	45.7	38.1
2007	64.6	52.7	39.6	43.1
2008	63.8	52.0	38.7	35.1
2009	59.7	53.7	35.0	32.9
2010	59.2	50.0	33.6	29.5
2011	59.6	52.1	34.2	30.5
2012	60.0	53.3	28.6	25.5
2013	56.6	58.3	29.0	22.4
2014	54.6	50.4	28.7	16.4
2015	54.5	58.4	28.2	21.6
2016	52.5	57.0	27.1	22.9
2017	51.2	57.0	28.0	19.1
2018	47.9	56.4	29.9	19.7
2019	44.8	57.8	28.5	18.4
2020	39.2	50.6	26.2	18.7