Volatile Organic Compounds in Air

VOCs Detected at Sites Around WTC (thru April 2002)

35 VOCs were detected in less than 10% of the samples.
9 others were detected more frequently.
All sample results for 7 of the 26 detected hazardous air pollutants were below screening levels. Of the remaining 19 HAPs detected, the results above screening levels occurred within the WTC work area, or on rare occasions at sites just outside it (during Sept-early Oct 2001). Because the vast majority of individual as well as the average* measured HAP levels have been lower than their respective screening levels, EPA does not expect an increased risk of long-term health problems as a result of volatile organic HAPs emitted from the World Trade Center site and occurring off-site.

Not Detected (as of mid-April 2002):

4-methyl-2-pentanone
bromodichloromethane
carbon disulfide**
dibromomethane
naphthalene**†
2-methyl-naphthalene**†

Detected infrequently, in less than 10% of samples (as of mid-April 2002):

1,1,1-trichloroethane
1,1,2,2 tetrachloroethane**
1,1,2 trichloroethane**
1,1 dichloroethane
1,2,4-trichlorobenzene**
1,2,4-trimethylbenzene
1,2-dibromoethane
1,2-dichlorobenzene
1,2-dichloroethane
1,2-dichloropropane
1,3-butadiene**
1,3-dichlorobenzene
1,4-dichlorobenzene**
2-hexanone
3-chloropropene
benzyl chloride**
bromoform**
bromomethane**
carbon tetrachloride**
chloroform**
cis 1-2-dichloroethene
cis 1,3-dichloropropene**
dibromochloromethane
dichlorodifluoromethane
ethyl acetate
hexachloro1,3-butadiene
methyl-tert-butyl-ether (MTBE)**
methylene chloride**
tetrachloroethene**
trans-1,2-dichloroethene
trans-1,3-dichloropropene
trichloroethene**
trichlorofluoromethane
vinyl acetate**
vinyl chloride**

Detected in >10% of samples (as of mid-April 2002):

1,3,5-trimethylbenzene
1,4-dioxane**
1-butanol
2-butanone
4-ethyltoluene
acetone
acetonitrile**
chlorobenzene**
chloroethane**
ethanol
ethylbenzene**
isopropyl alcohol
methyl isobutyl ketone**
o-xylene**
styrene**
toluene**

* For the purposes of evaluating exposure an average concentration of many samples more closely represents exposure over a longer period. This longer term average is less than the maximum concentration that could be contacted at any one time, but because the screening level assumes continuous exposure for a year, the average of the measured concentrations is more appropriate for evaluating risk than an individual measurement.

** Clean Air Act designated Hazardous Air Pollutants (also called toxic air pollutants).

† Although these two pollutants are not traditionally considered VOCs, they are included here for purposes of simplicity in presentation.