Appendix C	Contra Costa County: San Pablo-El Portal Air Quality and Health Risk													Table C-27	

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										0.55				
	Health Risk										3				
Benzene	Annual Avg									0.56	0.42				
	Health Risk									52	39				
"1,3-Butadiene"	Annual Avg									0.15	0.12				
	Health Risk									56	45				
Carbon Tetrachloride	Annual Avg														
	Health Risk														
"Chromium, Hexavalent"	Annual Avg										0.10				
	Health Risk										15				
para-Dichlorobenzene	Annual Avg														
	Health Risk														
Formaldehyde	Annual Avg										1.24				
	Health Risk										9				
Methylene Chloride	Annual Avg														
	Health Risk														
Perchloroethylene	Annual Avg														
	Health Risk														
Diesel PM	Annual Avg	No Monitoring Data Available													
	Health Risk														
Total Health Risk										108	111				

"*    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."															
**  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 that year.  There may be other significant compounds for which monitoring and/or health risk information are not available.