COPC document, which was adopted as a secondary clearance value for this project, is 1
Although the value chosen for this project was 1 the analytical detection limit available for
analyzing crystalline silica in indoor air samples is higher than this value, therefore a result that is below
the detection limit is considered to be protective of public health. Four out of eleven samples (36%) were
above the detection limit of 11 /xg/m’, ranging from 17.2 to 22.1 These values are also above the
secondary clearance value.
Although these values are above the clearance value, they are similar to concentrations detected in a
background study conducted by USEPA. In the USEPA background study, there was a frequency of
detection of 25%, with a range of 4 to 259 Further, the values from the background study without
the maximum value of 259 /tg/m’, provide a range of 4 to 28 This indicates that the range of
values observed in 114 Liberty Street are similar to those observed in the background study. Based on
this, it has been determined that the crystalline silica results are similar to background values and
therefore additional cleaning is not necessary.
NYC-WTC_000151528
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NYC-WTC_000151528Source: NYC Law Department, mirrored locally