Chapter 5	San Francisco Bay Area Air Quality and Health Risk										Table 5-43					

San Francisco Bay Area Air Basin Toxic Air Contaminants-Annual Average Concentrations and Health Risks																
TAC*	Conc./Risk	1990	1991	1992	1993	1994	1995	1996	1997	1998	1999	2000	2001	2002	2003	2004
Acetaldehyde	Annual Avg	1.3	1.4	1.03	1.31	1.17	0.42	0.83	0.73	0.65	0.76	0.68	0.73	0.63	0.74	0.74
	Health Risk	6	7	5	6	6	2	4	4	3	4	3	4	3	4	4
Benzene	Annual Avg	2.18	1.82	1.49	1.49	1.4	1.26	0.71	0.61	0.71	0.6	0.56	0.425	0.454	0.439	0.372
	Health Risk	202	169	138	138	129	116	66	56	66	55	52	39	42	41	34
"1,3-Butadiene"	Annual Avg	0.359	0.287	0.275	0.367	0.287	0.277	0.218	0.187	0.217	0.17	0.149	0.133	0.137	0.098	0.09
	Health Risk	135	108	103	138	108	104	82	70	82	64	56	50	51	37	34
Carbon Tetrachloride	Annual Avg	0.128	0.125		0.108		0.1	0.078				0.094	0.087	0.089	0.095	
	Health Risk	34	33		29		26	21				25	23	24	25	
"Chromium, Hexavalent"	Annual Avg			0.23	0.2	0.19	0.25	0.13	0.12	0.1	0.1	0.12		0.074	0.096	0.091
	Health Risk			34	29	29	37	19	17	15	15	18		11	14	14
para-Dichlorobenzene	Annual Avg		0.12	0.12	0.12	0.11	0.13	0.14	0.12			0.11	0.14	0.15	0.15	0.17
	Health Risk		8	8	8	7	8	9	8			7	9	10	10	11
Formaldehyde	Annual Avg	1.87	1.73	1.43	1.56	1.66	2.06	2.62	1.85	1.76	2.09	1.77	2.32	2.57	2.22	1.71
	Health Risk	14	13	11	11	12	15	19	14	13	15	13	17	19	16	13
Methylene Chloride	Annual Avg	1.04	2.32	0.65	0.72	0.59	0.6	0.58	0.55			0.53	0.27	0.22	0.22	0.14
	Health Risk	4	8	2	2	2	2	2	2			2	<1	<1	<1	<1
Perchloroethylene	Annual Avg	0.204	0.232	0.169	0.128	0.082	0.094	0.067	0.071			0.078	0.059	0.052	0.039	0.035
	Health Risk	8	9	7	5	3	4	3	3			3	2	2	2	1
Diesel PM**	Annual Avg	(2.5)					(1.9)					(1.6)				
	Health Risk	(750)					(570)					(480)				
Average Basin Risk***	Without Diesel PM	403	355	308	366	296	314	225	174	179	153	179	144	162	149	111
	With Diesel PM	(1153)					(884)					(659)				

"*    Concentrations for Hexavalent Chromium are expressed as ng/m3, and concentrations for Diesel PM are expressed as ug/m3.  Concentrations for all other TACs are expressed as ppb."																
"**  Diesel PM concentration estimates are based on receptor modeling techniques, and estimates are available only for selected years."																
*** Health Risk represents the number of excess cancer cases per million people based on a lifetime (70-year) exposure to the annual average concentration.  It reflects only those compounds listed in this table and only those with																
data for that year.  There may be other significant compounds for which we do not monitor or have health risk information. Additional information about interpreting the toxic air contaminant air quality trends can be found in																
"Chapter 1, Interpreting the Emission and Air Quality Statistics."