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
Alameda	Fremont-Chapel Way	Acetaldehyde	1.28	1.6	1.02	1.28	1.23	0.35	0.88	0.65	0.72		6	8	5	6	6	2	4	3	4	
		Benzene	1.92	1.67	1.21	1.35	1.25	1.24	0.58		0.76	0.61	178	155	112	125	116	115	54		71	57
		"1,3-Butadiene"	0.28	0.26	0.19	0.32	0.25	0.27	0.2		0.24	0.18	106	97	72	120	95	101	75		90	66
		Carbon Tetrachloride	0.13	0.13		0.11		0.1	0.08				35	34		28		27	20			
		Chromium (Hexavalent)			0.2	0.19	0.21	0.2	0.11		0.1				30	28	32	30	16		15	
		para-Dichlorobenzene			0.11	0.11	0.1	0.12	0.1						7	7	7	8	7			
		Formaldehyde	1.84	1.98	1.3	1.37	1.78	2.02	2.16	1.79	1.96		14	15	10	10	13	15	16	13	15	
		Methylene Chloride	0.76	0.58	0.52	0.83	0.5	0.62	0.5				3	2	2	3	2	2	2			
		Perchloroethylene	0.19	0.21	0.13	0.11	0.09	0.12	0.07				8	8	5	5	3	5	3			
		Diesel PM	No Monitoring Data Available																			
	Total Health Risk												349	319	244	332	273	304	197	16	193	123

Contra Costa	Concord-2975 Treat Blvd.	Acetaldehyde	1.41			1.39	1.46	0.62	0.86	0.76		0.87	7			7	7	3	4	4		4
		Benzene	1.84	1.58	1.41	1.13	1.08	1.09	0.48	0.56	0.57	0.57	171	147	130	105	100	101	44	52	53	53
		"1,3-Butadiene"	0.32	0.27	0.25	0.31	0.23	0.24	0.15	0.18	0.19	0.16	118	100	95	114	87	91	56	66	72	58
		Carbon Tetrachloride	0.13	0.13		0.11		0.1	0.08				34	33		29		27	22			
		Chromium (Hexavalent)				0.19	0.18	0.21	0.11	0.11						28	27	32	16	17		
		para-Dichlorobenzene			0.15	0.13	0.14	0.13	0.13	0.14					10	8	9	9	8	10		
		Formaldehyde	1.99			1.99	1.69	2.21	2.3	2.05		2.64	15			15	13	16	17	15		19
		Methylene Chloride	0.67	0.51	0.66	0.54	0.54	0.55	0.55	0.5			2	2	2	2	2	2	2	2		
		Perchloroethylene	0.34	0.42	0.39	0.2	0.1	0.15	0.08	0.1			14	17	16	8	4	6	3	4		
		Diesel PM	No Monitoring Data Available																			
	Total Health Risk												361	298	253	315	248	287	172	169	125	

	Richmond-13th Street	Acetaldehyde			0.78		0.92	0.36	0.59						4		5	2	3			
		Benzene		1.92	1.54	1.76	1.7	1.44	1					177	143	163	157	133	92			
		"1,3-Butadiene"		0.27	0.26	0.39	0.31	0.3	0.25					102	98	148	116	113	94			
		Carbon Tetrachloride		0.12		0.11		0.1	0.08					33		29		26	21			
		Chromium (Hexavalent)			0.19		0.15	0.26	0.13						28		23	39	19			
		para-Dichlorobenzene		0.14	0.12	0.12	0.1	0.12	0.19					9	8	8	7	8	13			
		Formaldehyde			1.08		1.32	2.22	4.27						8		10	16	32			
		Methylene Chloride		0.62	0.54	0.67	0.5	0.54	0.65					2	2	2	2	2	2			
		Perchloroethylene		0.15	0.09	0.09	0.06	0.04	0.03					6	4	4	2	2	1			
		Diesel PM	No Monitoring Data Available																			
	Total Health Risk													329	294	354	320	340	277			

			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
Contra Costa 	San Pablo-El Portal	Acetaldehyde										0.55										3
(continued)		Benzene									0.56	0.42									52	39
		"1,3-Butadiene"									0.15	0.12									56	45
		Carbon Tetrachloride																				
		Chromium (Hexavalent)																				
		para-Dichlorobenzene																				
		Formaldehyde										1.24										9
		Methylene Chloride																				
		Perchloroethylene																				
		Diesel PM	No Monitoring Data Available																			
	Total Health Risk																				107	95

San Francisco	San Francisco-Arkansas Street	Acetaldehyde					0.98	0.4		0.75	0.54		6				5	2		4	3	
		Benzene		1.49	1.25		1.07	0.95	0.53	0.51	0.63	0.65		138	116		99	88	49	48	59	61
		"1,3-Butadiene"		0.25	0.23		0.26	0.23	0.18	0.17	0.22	0.17		95	88		97	85	68	62	81	65
		Carbon Tetrachloride		0.12				0.1	0.08					33				26	21			
		Chromium (Hexavalent)				0.19	0.18	0.25	0.12	0.13	0.1					29	26	37	18	19	15	
		para-Dichlorobenzene		0.15	0.13		0.1	0.15	0.12	0.12				10	9		7	10	8	8		
		Formaldehyde	1.71				1.33	1.58		1.62	1.45		13				10	12		12	11	
		Methylene Chloride		3.22	0.88		0.6	0.63	0.66	0.5				11	3		2	2	2	2		
		Perchloroethylene		0.23	0.13		0.11	0.09	0.08	0.07				9	5		4	4	3	3		
		Diesel PM	No Monitoring Data Available																			
	Total Health Risk												19	295	221	29	250	266	169	157	168	

Santa Clara	San Jose-4th Street	Acetaldehyde	1.53	1.55	1.41	1.58	1.27	0.35	1.04	0.97	0.77	0.93	7	8	7	8	6	2	5	5	4	5
		Benzene	3.02	2.44	2.03	1.89	1.88	1.55	0.97	0.93	1.04	0.73	280	226	188	175	174	144	89	86	97	68
		"1,3-Butadiene"	0.55	0.39	0.44	0.49	0.39	0.35	0.31	0.29	0.29	0.23	207	145	164	182	145	131	117	108	110	85
		Carbon Tetrachloride	0.13	0.13		0.11		0.1	0.08				33	34		28		27	20			
		Chromium (Hexavalent)			0.29	0.25	0.25	0.33	0.17	0.13	0.11				43	37	38	49	25	20	17	
		para-Dichlorobenzene			0.12	0.12	0.1	0.12	0.14	0.12					8	8	7	8	10	8		
		Formaldehyde	2.27	2	2.09	1.83	2.16	2.28	2.7	2.56	2.24	2.69	17	15	15	14	16	17	20	19	17	20
		Methylene Chloride	0.83	6.65	0.66	0.58	0.8	0.69	0.55	0.75			3	23	2	2	3	2	2	3		
		Perchloroethylene	0.16	0.15	0.1	0.09	0.06	0.07	0.07	0.1			6	6	4	4	3	3	3	4		
		Diesel PM	No Monitoring Data Available																			
	Total Health Risk												554	456	431	457	391	383	291	252	244	177

			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	1.3	1.4	1.03	1.31	1.17	0.42	0.83	0.73	0.65	0.76	6	7	5	6	6	2	4	4	3	4
		Benzene	2.18	1.82	1.49	1.49	1.4	1.26	0.71	0.61	0.71	0.6	202	169	138	138	129	116	66	57	66	55
		"1,3-Butadiene"	0.36	0.29	0.28	0.37	0.29	0.28	0.22	0.19	0.22	0.17	135	108	103	138	108	104	82	70	82	64
		Carbon Tetrachloride	0.13	0.13		0.11		0.1	0.08				34	33		29		27	21			
		Chromium (Hexavalent)			0.23	0.2	0.19	0.25	0.13	0.12	0.1				34	30	29	37	19	17	16	
		para-Dichlorobenzene		0.12	0.12	0.12	0.11	0.13	0.14	0.12				8	8	8	7	8	9	8		
		Formaldehyde	1.87	1.73	1.43	1.56	1.66	2.06	2.62	1.85	1.76	2.09	14	13	11	12	12	15	19	14	13	15
		Methylene Chloride	1.04	2.32	0.65	0.72	0.59	0.6	0.58	0.55			4	8	2	3	2	2	2	2		
		Perchloroethylene	0.2	0.23	0.17	0.13	0.08	0.09	0.07	0.07			8	9	7	5	3	4	3	3		
		Diesel PM***	-2.5					-1.9				-1.6	-750					-570				480
	Average Basin Health Risk												403	355	308	368	296	315	224	174	179	138

"*      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.