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California Air Resources Board

Annual Toxics Summary		 ARB's ADAM Air Quality Database
Concord-2975 Treat Blvd
Carbon Tetrachloride
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
0.01       0.10 0.037 5 0.02  
1999
0.08 0.08   0.09 0.09 0.004 12 0.02  
1998
0.11 0.14   0.16 0.20 0.021 15 0.02  
1997
0.09 0.11   0.12 0.14 0.011 21 0.02  
1996
0.07 0.08 0.082 0.09 0.18 0.019 31 0.02 22
1995
0.07 0.10 0.102 0.11 0.14 0.012 29 0.02 27
1994
0.08 0.12   0.13 0.14 0.019 21 0.02  
1993
0.09 0.11 0.108 0.12 0.16 0.016 28 0.02 29
1992
0.10 0.12   0.13 0.17 0.017 22 0.02  
1991
0.11 0.12 0.125 0.14 0.16 0.014 29 0.02 33
1990
0.09 0.13 0.130 0.14 0.30 0.035 28 0.02 34
1989
0.08 0.11 0.128 0.15 0.34 0.050 23 0.02 34
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.