EPA interim final report on WTC background study, April 2003

NYC 9/11 Public Portal Document

Contaminant Site Worker Resident alpha methylstyrene 100 ppm .1 ppm Tetrahydrofuran 200 ppm .9 ppm Toluene 200 ppm 1.1 ppm Xylenes 100 ppm 1 ppm^") Reactive Gases Acetaldehyde 200 ppm .05 ppm (6) 1.3 ppm (5) Formaldehyde .75 ppm .04 ppm'(12) .35 ppm <5) Acrolein .1 ppm .0001 ppm <«>

Units

fZcc = fibers (>5 um length) per cubic centimeter of air S/mm2 = structures (>.5 um length) per square millimeter of filter paper ppm = parts per million in air ug/m3 = micrograms of contaminant per cubic meter of air ng/m3 = nanograms of contaminant per cubic meter of air NA - Not Applicable

Footnotes:

1. “Site Workers” refers to all workers involved in the response/demolition of the World Trade Center. Listed values are Occupational Safety and Health Administration (OSHA) Permissible Exposure Limits (PELs), Time Weighted Averages (TWA) unless otherwise noted.

2. “Residents” refers to people living in the vicinity of the World Trade Center as well as all other potentially exposed workers not involved in the response/demolition

3. Resident screening value is based on Asbestos Hazard Emergency Response Act (AHERA) methodology which uses transmission electron microscopy (TEM), and because of its basis in “background” (vs a risk basis) includes all asbestos fibers greater than 0.5 microns in length. Worker values are based on phase contrast microscopy (PCM, - which doesn’t distinguish asbestos fi-om other fibers) or, for results above the PCM screening value, TEM to derive a PCM equivalence that includes all asbestos fibers greater than 5 microns in length.

4. Screening values for chromimn were based on the most toxic form (hexavalent)

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