Year	Nitrogen oxides (NOx)	Sulphur dioxide (SO2)	Dust
2004	100	100	100
2005	99.483	94.334	85.971
2006	98.62	90.947	77.141
2007	96.304	85.041	75.256
2008	79.876	59.876	54.267
2009	70.648	47.52	42.485
2010	67.228	42.274	40.508
2011	65.896	40.066	44.269
2012	66.255	35.864	33.989
2013	58.509	28.372	30.038
2014	52.845	25.787	26.262
2015	50.49	22.829	18.91
2016	42.848	14.994	16.851
2017	40.913	14.271	16.395