Year	0-6,000 μg/m3·h	6,000-12,000 μg/m3·h	12,000-18,000 μg/m3·h	Greater than 18,000 μg/m3·h
2000	10.7	25.4	21.2	42.6
2001	8.2	20.7	22.0	49.1
2002	4.2	25.1	23.6	47.1
2003	5.7	10.5	13.2	70.5
2004	15.0	24.6	23.2	37.3
2005	7.7	16.0	26.8	49.5
2006	1.9	4.9	20.3	73.0
2007	17.8	26.9	19.9	35.5
2008	4.3	23.3	33.5	38.8
2009	15.0	34.5	25.7	24.7
2010	9.9	29.6	37.2	23.3
2011	6.5	28.5	45.4	19.5
2012	8.2	34.6	28.2	29.1
2013	14.7	38.6	24.5	22.2
2014	9.2	38.5	33.0	19.3
2015	15.6	26.6	25.4	32.4
2016	18.9	34.3	26.3	20.5
2017	19.5	32.7	20.0	27.8
2018	4.0	16.8	31.1	48.2
2019	9.3	25.0	26.4	39.3
2020	23.3	48.3	23.0	5.5
2021	19.5	37.0	25.4	18.1