Chapter 5	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
Acetaldehyde	Annual Avg	1.30	1.40	1.03	1.31	1.17	0.42	0.83	0.73	0.65	0.76	0.68	0.73	0.63	0.74
	Health Risk	6	7	5	6	6	2	4	4	3	4	3	4	3	4
Benzene	Annual Avg	2.18	1.82	1.49	1.49	1.40	1.26	0.71	0.61	0.71	0.60	0.56	0.43	0.45	0.44
	Health Risk	202	169	138	138	129	116	66	56	66	55	52	39	42	41
"1,3-Butadiene"	Annual Avg	0.36	0.29	0.28	0.37	0.29	0.28	0.22	0.19	0.22	0.17	0.15	0.13	0.14	0.10
	Health Risk	135	108	103	138	108	104	82	70	82	64	56	50	51	37
Carbon Tetrachloride	Annual Avg	0.13	0.13		0.11		0.10	0.08				0.09	0.09	0.09	0.10
	Health Risk	34	33		29		26	21				25	23	24	25
"Chromium, Hexavalent"	Annual Avg			0.23	0.20	0.19	0.25	0.13	0.12	0.10	0.10	0.12		0.07	0.10
	Health Risk			34	29	29	37	19	17	15	15	18		11	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
	Health Risk		8	8	8	7	8	9	8			7	9	10	10
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
	Health Risk	14	13	11	11	12	15	19	14	13	15	13	17	19	16
Methylene Chloride	Annual Avg	1.04	2.32	0.65	0.72	0.59	0.60	0.58	0.55			0.53	0.27	0.22	0.22
	Health Risk	4	8	2	2	2	2	2	2			2	1	1	1
Perchloroethylene	Annual Avg	0.20	0.23	0.17	0.13	0.08	0.09	0.07	0.07			0.08	0.06	0.05	0.04
	Health Risk	8	9	7	5	3	4	3	3			3	2	2	2
Diesel Particulate Matter**	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	145	163	150
	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 parts per billion.															
"**  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."