USEPA Data Evaluation Summary, 125 Liberty Street, Nov 2002

NYC 9/11 Public Portal Document

Fibrous glass — We reviewed approximately 120 PCM results reported as fibrous glass analysis. The highest detected concentration was 0.009 f/cc, which is below the numeric criteria of 0.01 f/cc in the COPC document. Thus, for fibrous glass, the data we reviewed indicates that fibrous glass is not a hazard at 125 Cedar Street.

Mercury — We reviewed 66 wipe results which were analyzed for mercury. Seventeen samples were below the detection limit of 0.000478 µg/m2 and the highest detected concentration was 0.0164 µg/m2. The COPC document does not establish a numeric criteria for mercury, however since USEPA is collecting 250 wipe samples for mercury as part of residential cleanup program a numeric criteria is currently being developed. The draft value, which is subject to revision based upon further evaluation of exposure parameters, is currently 94 µg/m2. Comparison of the mercury concentrations detected to the draft numeric criteria of 94 µg/m2 indicates that mercury is three orders of magnitude below the draft numeric criteria. Thus, for mercury, the data we reviewed indicates that mercury is not a hazard at 125 Cedar Street.

Silica — We reviewed the data for 19 air samples which were analyzed for silica (i.e., total quartz). All of the samples were below the detection limit of 10 µg. The numeric criterion that USEPA has proposed in the COPC document is 1 µg/m3. Although the COPC document has chosen the value of 1 µg/m3, the available methodology for collecting indoor air samples for silica cannot achieve a value this low, therefore a result that is below the detection limit is considered to be protective of public health. This is the same approach we are using at 110 Liberty Street, where the detection limit was 4µg. Thus, for silica, the data we reviewed indicates that silica is not a hazard

NYC-WTC 000107526