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California Air Resources Board

Annual Toxics Summary		 ARB's ADAM Air Quality Database
Concord-2975 Treat Blvd
Methylene Chloride
parts per billion
Year Months
Present		 Minimum Median Mean 90th
Percentile		 Maximum Standard
Deviation		 Number of
Observations		 Detection
Limit		 Estimated
Risk
2002
            0    
2001
            0    
2000
0.5       0.5 0.00 5 1.0  
1999
0.5 0.5   0.5 0.5 0.00 20 1.0  
1998
0.5 0.5   0.5 0.5 0.00 15 1.0  
1997
0.5 0.5 0.50 0.5 0.5 0.00 29 1.0 2
1996
0.5 0.5 0.55 0.5 2.2 0.31 31 1.0 2
1995
0.5 0.5 0.55 0.5 1.3 0.18 30 1.0 2
1994
0.5 0.5 0.54 0.5 2.0 0.27 32 1.0 2
1993
0.5 0.5 0.54 0.5 1.4 0.19 30 1.0 2
1992
0.5 0.5 0.66 0.5 4.0 0.63 31 1.0 2
1991
0.5 0.5 0.51 0.5 1.0 0.10 26 1.0 2
1990
0.5 0.5 0.67 1.2 2.2 0.42 28 1.0 2
1989
0.5 0.5 0.66 0.5 1.9 0.37 22 1.0 2
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.
Risks shown only for those substances with unit risk factors.