Background Concentration Estimates

AREA	MAJOR	MOBILE	BACKGROUND
ethylene oxide	coke oven emissions	acetaldehyde	PCBs
perchloroethylene^B	acrylonitrile^A	1,3 butadiene	ethylene dibromide
methylene chloride^B	vinyl chloride^A	acrolein^A	carbon tetrachloride
1,3 dichloropropene	propylene dichoride^A	lead^A	hexachlorobenzene
POM	quinoline^A	benzene	ethylene dichloride
nickel^M	1,1,2,2 tetrachloroethane^A	formaldehyde	chloroform
arsenic^M			mercury
beryllium			trichloroethylene^A
cadmium^M
manganese^M
chromium^M
hydrazine^M
M = for at least 5 States, the dominant source type is major A= for at least 5 States, the dominant source type is area and other B= for at least 5 States, the dominant source type is background