Screening Levels

Screening levels for metals and volatile organic compounds detected near WTC that are hazardous air pollutants have been set to protect against significantly increased risks of cancer and other health problems, and are based on continuous exposure for a year. Because these screening levels assume continuous exposure for an extended duration, the average of the measured concentrations is more appropriate for evaluating risk than an individual measurement.

Therefore, individual values above the screening level do not necessarily indicate a potential health problem. Rather, such measurements indicate the need for careful monitoring and the assessment of longer-term data trends for evaluation against appropriate health criteria.

WTC screening levels
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Metals*
arsenic - 0.3 ug/m3
cadmium - 0.2 ug/m3
nickel - 2 ug/m3
antimony - 2 ug/m3
manganese - 0.5 ug/m3

* Lead and chromium shown elsewhere.

VOCs** [all in ppb]
Acetonitrile - 360
benzyl chloride- 30
bromoform - 600
bromomethane -10
1,3-butadiene - 10
carbon disulfide - 2200
carbon tetrachloride - 60
chlorobenzene - 2200
chloroethane - 38000
chloroform - 70
1,4-dichlorobenzene - 100
1,1-dichloroethane - 100
Cis-1,3-dichloropropene - 40
1,4-dioxane - 600
ethylbenzene - 2300
hexachloro-1,3-butadiene - 30
methyl isobutyl ketone - 200
methylene chloride - 2900
methylmethacrylate - 1700
methyl-tert-butyl ether - 8300
naphthalene - 6
styrene - 2300
tetrachloroethene - 180
1,1,2,2-tetrachloroethane - 20
toluene - 1100
1,2,4-trichlorobenzene - 270
1,1,2-trichloroethane - 80
trichloroethene - 650
vinyl acetate - 570
vinyl chloride - 390
o-xylene - 1000

** Benzene screening level presented elsewhere.