Chapter 5	"Toxic Air Contaminant Emissions, Air Quality, and Health Risk"					Table 5-1

Toxic Air Contaminant Unit Risk Factors						
Toxic Air Contaminant	Unit Risk/Million People*	Limit of Detection (ppb)				
Acetaldehyde	2.7	0.10				
Benzene	29	0.05				
"1,3-Butadiene"	170	0.04				
Carbon Tetrachloride	42	0.02				
Chromium (Hexavalent)	"150,000"	0.06**				
para-Dichlorobenzene	11	0.30				
Formaldehyde	6	0.10				
Methylene Chloride	1	0.10				
Perchloroethylene	5.9	0.01				
Diesel Particulate Matter	300***	N/A				

*    The Unit Risk represents the number of excess cancer cases per million people						
"per microgram per cubic meter TAC concentration over a 70-year, lifetime exposure."
**  The unit for hexavalent chromium is nanograms per cubic meter.
*** A diesel particulate matter unit risk value of 300 is used as a reasonable estimate
in the “Risk Reduction Plan to Reduce Particulate Matter Emissions from
"Diesel-Fueled Engines and Vehicles” (ARB, October 2000)."