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| Read About Estimated Risk | 
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| Year | Months Present | Minimum | Median | Mean | 90th Percentile | Maximum | Standard Deviation | Number of Observations | Detection Limit | Estimated Risk | ||||||||||||
| 2025 | 
 | 0.9 | 1.6 | * | 2.8 | 3.0 | 0.66 | 11 | 0.1 | * | ||||||||||||
| 2024 | 
 | 0.8 | 2.2 | 2.10 | 2.9 | 3.7 | 0.72 | 30 | 0.1 | 44 | ||||||||||||
| 2023 | 
 | 0.4 | 2.0 | 2.12 | 2.8 | 4.0 | 0.76 | 29 | 0.1 | 45 | ||||||||||||
| 2022 | 
 | 0.5 | 2.1 | 2.05 | 2.9 | 3.0 | 0.62 | 31 | 0.1 | 43 | ||||||||||||
| 2021 | 
 | 1.0 | 2.1 | * | 2.9 | 4.8 | 0.89 | 17 | 0.1 | * | ||||||||||||
| 2020 | 
 | 0.8 | * | * | * | 2.5 | 0.58 | 8 | 0.1 | * | ||||||||||||
| 2019 | 
 | 0.7 | 1.7 | 2.04 | 3.5 | 4.5 | 0.93 | 29 | 0.1 | 43 | ||||||||||||
| 2018 | 
 | 0.7 | 2.2 | 2.32 | 3.5 | 4.0 | 0.88 | 31 | 0.1 | 49 | ||||||||||||
| 2017 | 
 | 0.5 | 2.0 | 2.19 | 3.6 | 5.2 | 0.99 | 30 | 0.1 | 46 | ||||||||||||
| 2016 | 
 | 1.1 | 2.3 | * | 3.5 | 4.5 | 0.88 | 27 | 0.1 | * | ||||||||||||
| 2015 | 
 | 1.0 | 2.0 | 2.08 | 3.0 | 3.4 | 0.64 | 30 | 0.1 | 44 | ||||||||||||
| 2014 | 
 | 0.7 | 1.6 | 1.79 | 2.9 | 3.6 | 0.79 | 31 | 0.1 | 38 | ||||||||||||
| 2013 | 
 | 0.9 | 1.5 | 1.65 | 2.2 | 3.9 | 0.64 | 30 | 0.1 | 35 | ||||||||||||
| 2012 | 
 | 0.6 | 1.8 | 1.94 | 3.0 | 5.0 | 0.93 | 30 | 0.1 | 41 | ||||||||||||
| 2011 | 
 | 0.7 | 1.8 | * | 2.6 | 3.2 | 0.69 | 28 | 0.1 | * | ||||||||||||
| 2010 | 
 | 0.5 | 1.4 | 1.52 | 2.3 | 3.2 | 0.63 | 25 | 0.1 | 32 | ||||||||||||
| 2009 | 
 | 0.5 | 1.7 | 1.75 | 2.7 | 3.5 | 0.82 | 31 | 0.1 | 37 | ||||||||||||
| 2008 | 
 | 0.9 | 1.8 | 1.88 | 2.9 | 3.8 | 0.65 | 30 | 0.1 | 40 | ||||||||||||
| 2007 | 
 | 0.8 | 1.5 | 1.83 | 2.7 | 4.7 | 0.83 | 30 | 0.1 | 38 | ||||||||||||
| 2006 | 
 | 0.4 | 2.0 | 1.88 | 2.5 | 3.6 | 0.65 | 31 | 0.1 | 39 | ||||||||||||
| 2005 | 
 | 0.5 | 2.1 | 2.08 | 2.9 | 4.1 | 0.83 | 30 | 0.1 | 44 | ||||||||||||
| 2004 | 
 | 0.2 | 2.0 | 1.93 | 2.8 | 5.1 | 0.95 | 30 | 0.1 | 41 | ||||||||||||
| 2003 | 
 | 0.9 | 2.3 | 2.30 | 3.3 | 4.5 | 0.85 | 31 | 0.1 | 48 | ||||||||||||
| 2002 | 
 | 1.3 | 2.3 | 2.56 | 3.5 | 6.3 | 1.06 | 31 | 0.1 | 54 | ||||||||||||
| 2001 | 
 | 0.8 | 2.0 | 2.54 | 3.9 | 11 | 1.89 | 29 | 0.1 | 53 | ||||||||||||
| 2000 | 
 | 0.8 | 2.1 | 2.14 | 3.2 | 4.5 | 0.86 | 27 | 0.1 | 45 | ||||||||||||
| 1999 | 
 | 0.6 | 2.4 | 2.49 | 4.0 | 5.8 | 1.18 | 30 | 0.1 | 52 | ||||||||||||
| 1998 | 
 | 0.05 | 1.8 | 2.00 | 3.4 | 4.3 | 1.04 | 30 | 0.1 | 42 | ||||||||||||
| 1997 | 
 | 0.9 | 2.3 | 2.37 | 3.6 | 5.1 | 0.92 | 30 | 0.1 | 50 | ||||||||||||
| 1996 | 
 | 0.9 | 2.0 | 2.10 | 3.1 | 5.0 | 0.95 | 30 | 0.1 | 44 | ||||||||||||
| 1995 | 
 | 0.6 | 1.7 | 1.81 | 2.7 | 3.9 | 0.77 | 27 | 0.1 | 38 | ||||||||||||
| 1994 | 
 | 0.9 | 1.9 | 2.08 | 3.3 | 3.8 | 0.78 | 30 | 0.1 | 44 | ||||||||||||
| 1993 | 
 | 0.2 | 1.2 | 1.46 | 2.3 | 2.8 | 0.74 | 29 | 0.1 | 31 | ||||||||||||
| 1992 | 
 | 0.05 | 1.0 | 1.10 | 2.1 | 2.6 | 0.76 | 27 | 0.1 | 23 | ||||||||||||
| 1991 | 
 | 0.2 | 1.1 | 1.30 | 2.0 | 2.7 | 0.65 | 29 | 0.1 | 27 | ||||||||||||
| 1990 | 
 | 0.2 | 0.9 | 1.26 | 2.7 | 3.9 | 1.02 | 34 | 0.1 | 26 | ||||||||||||
| 1989 | 
 | 0.7 | 2.0 | 2.38 | 3.5 | 6.3 | 1.37 | 25 | 0.1 | 50 | ||||||||||||
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| 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. | |||
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|  | 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. |  |