Year	Lower than 10,000 µg/m3·h	10,000-20,000 µg/m3·h	20,000-30,000 µg/m3·h	30,000-50,000 µg/m3·h	Greater than 50,000 µg/m3·h
2005	20.6	20.6	19.1	30.1	9.7
2006	0.1	30.5	18	40.8	10.6
2007	38.9	14.6	13.6	25.5	7.4
2008	21.5	30.1	21.5	26.4	0.5
2009	33.5	19.2	18.4	25.6	3.3
2010	37.7	14.9	25.6	19.8	2
2011	32.1	16.4	26.2	22.2	3
2012	35.8	18.9	18.4	23.2	3.6
2013	33.6	24.4	19.6	18.6	3.8
2014	32.4	32.1	25.5	9.9	0.1
2015	41.4	7.8	17.5	29.2	4.1
2016	38	19.1	24.3	17.5	1
2017	42.9	17	18.5	18.6	3
2018	12.5	30.1	16.3	36.3	4.8
2019	14.8	32.2	21.2	29.3	2.4
2020	40.9	22.1	28.7	7.9	0.4