Annual Average Concentration* Health Risk** COUNTY SITE NAME TAC 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 Kern Bakersfield-Chester Avenue Acetaldehyde 1.87 1.83 1.6 2 9 9 8 10 Benzene 2.68 2.22 1.54 1.47 248 205 143 136 "1,3-Butadiene" 0.39 0.31 0.24 0.33 146 115 90 123 Carbon Tetrachloride 0.13 0.13 0.1 34 33 27 Chromium (Hexavalent) 0.21 0.21 31 31 para-Dichlorobenzene 0.12 0.17 8 11 Formaldehyde 2.44 1.62 1.36 1.85 18 12 10 14 Methylene Chloride 0.92 0.65 0.52 0.99 3 2 2 3 Perchloroethylene 0.09 0.13 0.08 1.48 4 5 3 59 Diesel PM No Monitoring Data Available Total Health Risk 461 381 295 414 Bakersfield-5558 California Avenue Acetaldehyde 0.49 1.59 1.22 1.27 1.69 2 8 6 6 8 Benzene 1.14 0.78 0.57 0.7 0.71 106 72 53 65 66 "1,3-Butadiene" 0.21 0.21 0.16 0.2 0.15 78 79 60 75 58 Carbon Tetrachloride 0.1 0.08 26 21 Chromium (Hexavalent) 0.26 0.13 0.1 0.1 39 19 15 15 para-Dichlorobenzene 0.11 0.11 0.12 7 7 8 Formaldehyde 1.92 3.48 3.12 2.99 3.67 14 26 23 22 27 Methylene Chloride 0.54 0.64 0.5 0.5 2 2 2 2 Perchloroethylene 0.09 0.12 0.04 4 5 2 Diesel PM No Monitoring Data Available Total Health Risk 279 239 168 183 161 Fresno Fresno-1st Street Acetaldehyde 2.29 1.89 1.4 0.67 1.5 11 9 7 3 7 Benzene 2.42 1.34 1.35 1.44 1.24 0.79 1 0.83 0.8 224 124 125 133 115 73 92 76 74 "1,3-Butadiene" 0.46 0.26 0.34 0.36 0.3 0.23 0.23 0.27 0.21 173 99 129 134 113 88 88 100 81 Carbon Tetrachloride 0.12 0.11 0.1 0.08 32 28 26 21 Chromium (Hexavalent) 0.21 0.15 0.14 0.22 0.1 0.11 0.1 31 22 21 33 16 16 15 para-Dichlorobenzene 0.1 0.1 0.14 0.13 0.11 0.14 7 7 9 8 7 9 Formaldehyde 2.32 1.64 2.01 2.41 3.42 17 12 15 18 25 Methylene Chloride 0.62 0.54 0.69 0.59 0.58 0.5 0.52 2 2 2 2 2 2 2 Perchloroethylene 0.14 0.1 0.1 0.06 0.07 0.04 0.04 6 4 4 3 3 2 2 Diesel PM No Monitoring Data Available Total Health Risk 465 267 339 323 321 208 208 224 154 Annual Average Concentration* Health Risk** COUNTY SITE NAME COMPOUND 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 Stanislaus Modesto-I St. (Courthouse) Acetaldehyde 1.51 1.37 1.75 1.44 0.51 1.17 1.25 7 7 9 7 3 6 6 Benzene "1,3-Butadiene" Carbon Tetrachloride Chromium (Hexavalent) 0.27 0.23 0.22 0.32 0.16 0.11 40 34 33 48 25 17 para-Dichlorobenzene Formaldehyde 1.43 1.32 1.82 1.86 2.16 2.58 2.43 11 10 13 14 16 19 18 Methylene Chloride Perchloroethylene Diesel PM No Monitoring Data Available Total Health Risk 18 57 56 54 67 49 41 Modesto-14th Street Acetaldehyde 1.65 8 Benzene 2.25 1.86 1.2 1.23 1.14 1.2 0.7 0.77 0.85 0.61 208 172 111 114 105 111 65 71 78 56 "1,3-Butadiene" 0.38 0.35 0.22 0.35 0.29 0.3 0.24 0.21 0.26 0.16 142 133 84 131 110 112 89 78 98 61 Carbon Tetrachloride 0.13 0.13 0.11 0.09 0.07 0.11 34 35 30 25 20 30 Chromium (Hexavalent) para-Dichlorobenzene 0.11 0.1 0.12 0.1 0.11 0.1 0.15 7 7 8 7 7 7 10 Formaldehyde 3.09 23 Methylene Chloride 0.65 0.61 0.55 0.65 0.62 0.58 0.5 0.59 0.51 2 2 2 2 2 2 2 2 2 Perchloroethylene 0.15 0.15 0.12 0.11 0.09 0.05 0.04 0.05 0.04 6 6 5 4 4 2 2 2 1 Diesel PM No Monitoring Data Available Total Health Risk 392 355 209 290 227 259 183 163 209 148 San Joaquin Stockton-Hazelton Street Acetaldehyde 1.47 1.75 1.07 1.31 1.1 0.9 0.9 1 1.07 7 9 5 6 5 4 4 5 5 Benzene 2.01 1.95 1.37 1.23 1.05 0.64 0.52 0.69 0.65 186 181 127 113 97 60 48 64 60 "1,3-Butadiene" 0.34 0.32 0.22 0.28 0.25 0.21 0.18 0.21 0.18 126 121 82 106 94 77 68 77 68 Carbon Tetrachloride 0.13 0.14 0.1 0.08 0.12 35 36 26 20 30 Chromium (Hexavalent) 0.22 0.25 0.25 0.14 33 37 37 21 para-Dichlorobenzene 0.1 0.1 0.1 0.11 0.1 0.11 7 7 7 7 7 7 Formaldehyde 1.81 1.88 1.24 1.38 1.56 2.35 2.24 2.33 2.68 13 14 9 10 12 17 17 17 20 Methylene Chloride 0.63 0.5 0.6 0.5 0.75 0.53 0.5 0.5 0.5 2 2 2 2 3 2 2 2 2 Perchloroethylene 0.13 0.11 0.12 0.07 0.06 0.07 0.09 0.03 5 5 5 3 2 3 4 1 Diesel PM No Monitoring Data Available Total Health Risk 374 373 270 54 284 229 211 150 196 154 Annual Average Concentration* Health Risk** COUNTY SITE NAME COMPOUND 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 All Counties BASIN SUMMARY Acetaldehyde 1.94 1.84 1.38 1.73 1.29 0.54 1.28 1.19 1.3 1.56 9 9 7 8 6 3 6 6 6 8 Benzene 2.45 2.11 1.36 1.32 1.33 1.16 0.73 0.71 0.76 0.69 227 196 126 122 123 107 68 66 71 64 "1,3-Butadiene" 0.41 0.36 0.24 0.34 0.32 0.26 0.22 0.2 0.23 0.18 154 135 89 127 121 99 83 73 88 67 Carbon Tetrachloride 0.13 0.13 0.11 0.1 0.08 0.11 34 34 29 26 20 30 Chromium (Hexavalent) 0.23 0.21 0.19 0.28 0.13 0.11 0.1 34 31 29 42 20 16 16 para-Dichlorobenzene 0.11 0.11 0.13 0.11 0.11 0.1 0.13 8 7 9 7 8 7 9 Formaldehyde 2.45 1.81 1.46 1.67 1.8 2.1 2.96 2.77 2.86 3.44 18 13 11 12 13 16 22 20 21 25 Methylene Chloride 0.76 0.59 0.55 0.76 0.59 0.61 0.54 0.53 0.52 0.5 3 2 2 3 2 2 2 2 2 2 Perchloroethylene 0.13 0.13 0.1 0.47 0.07 0.07 0.07 0.06 0.04 5 5 4 19 3 3 3 2 2 Diesel PM*** -2.6 -1.7 -1.3 -780 -510 -390 Average Basin Health Risk 450 402 279 360 305 304 231 195 235 165 "* Concentrations for Chromium (Hexavalent) are expressed as ng/m3, and concentrations for Diesel PM are expressed as ug/m3. Concentrations for all other TACs are expressed as ppb. " ** Health Risk represents the number of excess cancer cases per million people based on a lifetime (70 year) exposure to the annual average concentration. Total Health Risk represents only those compounds listed in this table and only those with data for the year. There may be other significant compounds for which monitoring and/or health risk information are not available. "*** The Diesel PM concentrations are estimates based on receptor modeling. The 1999 concentrations reflect an estimate for the year 2000. Because data are not available for all years, Diesel PM is not included in the " Average Basin Health Risk number.