San Joaquin Valley Air Basin 											
Toxic Air Contaminants - Annual Average Concentrations and Health Risk											
TAC*	Conc./Risk	1990	1991	1992	1993	1994	1995	1996	1997	1998	1999
Acetaldehyde	Annual Avg	1.94	1.84	1.38	1.73	1.29	0.54	1.28	1.19	1.3	1.56
	Health Risk 	9	9	7	8	6	3	6	6	6	8
Benzene	Annual Avg	2.45	2.11	1.36	1.32	1.33	1.16	0.73	0.71	0.76	0.69
	Health Risk 	227	196	126	122	123	107	68	66	71	64
"1,3-Butadiene"	Annual Avg	0.41	0.36	0.24	0.34	0.32	0.26	0.22	0.2	0.23	0.18
	Health Risk 	154	135	89	127	121	99	83	73	88	67
Carbon Tetrachloride	Annual Avg	0.13	0.13		0.11		0.1	0.08		0.11	
	Health Risk 	34	34		29		26	20		30	
Chromium (Hexavalent)	Annual Avg			0.23	0.21	0.19	0.28	0.13	0.11	0.1	
	Health Risk 			34	31	29	42	20	16	16	
para-Dichlorobenzene	Annual Avg		0.11	0.11	0.13	0.11	0.11	0.1	0.13		
	Health Risk 		8	7	9	7	8	7	9		
Formaldehyde	Annual Avg	2.45	1.81	1.46	1.67	1.8	2.1	2.96	2.77	2.86	3.44
	Health Risk 	18	13	11	12	13	16	22	20	21	25
Methylene Chloride	Annual Avg	0.76	0.59	0.55	0.76	0.59	0.61	0.54	0.53	0.52	0.5
	Health Risk 	3	2	2	3	2	2	2	2	2	2
Perchloroethylene	Annual Avg	0.13	0.13	0.1	0.47	0.07	0.07	0.07	0.06	0.04	
	Health Risk 	5	5	4	19	3	3	3	2	2	
Diesel Particulate Matter**	Annual Avg	2.6					1.7				1.3
	Health Risk 	780					510				390
Average Basin Risk***	Without Diesel PM	450	402	279	360	305	304	231	195	235	165
	With Diesel PM	1230					814				555

*   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 parts per billion.											
"**  Diesel PM concentration estimates are based on receptor modeling techniques, and estimates are available only for selected years. Estimated concentration for 1999 reflects the year 2000."											
*** 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."