NYC-WTC_000232639

NYC 9/11 Public Portal Document

Final Report 125 Cedar Street, NYC, NY

Wipe Sampling

Background and clearance wipe sampling was performed consistent with generally accepted industrial hygiene practices. All acceptable results of the sampling represent conditions found on the dates the samples were collected. Individual analytes specified herein were analyzed in accordance with the project specifications utilizing the following analytical procedures:

• Lead, EPA Method SW-846-6010B • PAHs, ASTM-6661-01, EPA Method SW-846-8270C • Dioxin, ASTM-6661-01, EPA Method SW-846-8290 • Mercury, EPA Method SW-846-7471A

Wipe Sample analysis

Lead ATC’s New York City laboratory performed atomic absorption spectroscopy (AAS) to determine the presence of lead in clearance wipe samples. In elemental foim, lead will absorb ultraviolet light at a specific wavelength when excited by heat. ATC’s AAS instrument looks for the presence of lead by focusing a beam of uv light at a specific wavelength through a flame and into a detector. The wipe sample is aspirated into the flame. If that metal is present in the sample, it will absorb some of the light, thus reducing its intensity. The instrument measures the change in intensity. A computer data system converts the change in intensity into an absorbance.

As concentration goes up, absorbance goes up. The analyst can then construct a calibration curve by running standards of various concentrations on the AAS and observing the absorbance.

PAH Method 8270 was used to quantitate polyaromatic hydrocarbon compounds that are soluble in methylene chloride and capable of being eluted, without derivatization, as sharp peaks from a gas chromatographic fused-silica capillary column coated with slightly polar silicone.

Dioxin The analytical method calls for the use of high-resolution gas chromatography and high- resolution mass spectrometry (HRGC/HRMS) on purified sample extracts. Samples containing concentrations of specific congeneric analytes (PCDDs and PCDFs) considered within the scope of this method that are greater than ten times the upper MCLs must be analyzed by a protocol designed for such concentration levels, e.g.. Method 8280. An optional method for reporting the analytical results using a 2,3,7,8-TCDD toxicity equivalency factor (TEE) was also conducted. However, in accordance with a request made by the USEPA, all non-detect congeners were reported at 50% of the analytical sensitivity, thereby

ATC Project No. 15.22906.0002 Page?

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NYC-WTC_000232648