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Read About Estimated Risk

Year	Months Present	Minimum	Median	Mean	90th Percentile	Maximum	Standard Deviation	Number of Observations	Detection Limit	Estimated Risk
2025		0.6	*	*	*	1.6	0.35	10	0.1	*
2024		0.5	0.9	1.19	2.2	2.6	0.60	26	0.1	25
2023		0.4	0.9	1.09	1.8	2.3	0.50	28	0.1	23
2022		0.3	0.9	1.15	2.1	2.9	0.63	32	0.1	24
2021		0.05	0.9	*	2.1	3.0	0.74	17	0.1	*
2020		0.5	*	*	*	3.1	0.90	9	0.1	*
2019		0.6	0.9	1.29	2.6	4.0	0.88	30	0.1	27
2018		0.3	1.2	1.70	2.3	9.8	1.73	29	0.1	36
2017		0.4	1.3	1.64	2.8	5.7	1.07	30	0.1	35
2016		0.5	1.3	1.56	2.8	4.8	0.93	30	0.1	33
2015		0.6	1.4	1.46	2.4	3.3	0.71	30	0.1	31
2014		0.5	1.0	1.28	2.2	4.8	0.91	30	0.1	27
2013		0.5	1.3	1.37	2.4	3.2	0.75	31	0.1	29
2012		0.3	0.8	1.01	1.9	3.7	0.80	30	0.1	21
2011		0.5	1.1	1.32	2.5	3.1	0.76	30	0.1	28
2010		0.2	0.9	1.31	3.0	5.5	1.13	30	0.1	28
2009		0.05	0.8	1.14	2.3	3.6	0.79	31	0.1	24
2008		0.3	0.9	0.98	1.8	2.9	0.60	30	0.1	21
2007		0.4	0.8	1.15	2.4	3.5	0.83	29	0.1	24
2006		0.4	1.2	1.37	2.5	3.6	0.84	27	0.1	29
2005		0.2	0.9	1.04	1.9	2.5	0.60	30	0.1	22
2004		0.5	1.3	1.54	2.4	4.5	0.95	30	0.1	32
2003		0.5	1.5	1.71	2.4	5.3	1.06	30	0.1	36
2002		0.4	1.2	2.03	3.6	15	2.67	30	0.1	43
2001		0.05	1.0	1.51	3.4	8.7	1.67	31	0.1	32
2000		0.7	1.3	*	2.8	4.2	0.99	16	0.1	*
1999		0.8	1.2	*	2.1	3.7	0.75	21	0.1	*
1998		0.5	1.3	1.45	2.5	3.7	0.78	31	0.1	30
1997		0.7	1.3	1.62	2.9	5.2	0.99	30	0.1	34
1996		0.5	1.4	*	3.1	4.9	1.04	27	0.1	*
1995		0.05	1.1	1.58	3.5	6.1	1.41	29	0.1	33
1994		0.4	1.2	1.33	2.4	3.1	0.73	31	0.1	28
1993		0.2	1.0	*	2.7	3.3	0.88	27	0.1	*
1992		0.3	1.0	*	1.9	2.4	0.57	16	0.1	*
1991		0.4	1.1	*	2.3	3.0	0.70	23	0.1	*
1990		0.7	1.6	1.71	3.1	3.7	0.89	28	0.1	36
1989		0.6	2.0	2.94	4.5	9.8	2.24	25	0.1	62

1989-1995 data and 1996-2025 data represent different methods and should not be compared.
See Report on a Parallel Carbonyl Monitoring Study Using C18 and Silica Gel Sampling Media for details.
	Notes:	Values below the Limit of Detection (LoD) assumed to be ½ LoD. Means and risks shown only for years with data in all 12 months. "*" means there was insufficient or no data available to determine the value.