Letter re: EPA/DEP WTC dust cleanup at 114 Liberty Street,

NYC 9/11 Public Portal Document

11

For silica, the levels EPA/NYCDEP found were much higher than their own health benchmarks, and as discussed later, even higher than the NIOSH benchmark for healthy male workers. EPA excused these levels on the false claim that they were within background levels, albeit unsafe background levels. EPA stated the following in its 4/18/03 report of testing at 114 Liberty, admitting the levels did not meet health benchmarks: The secondary clearance level for crystalline silica was met in 64% of the areas tested; however the remaining areas were similar to background values observed from a USEPA background study. Since all of the primary clearance values have been met, the building can be released back to the owner, [fmm cover ietier]

Silica - Eleven air samples were collected and analyzed for crystalline silica at a detection limit of 11 pg/m^ Seven samples were below the detection limit and four samples were above the detection limit, with values of 17.3,19.6,22.1, and 22.1 pg/m®. The numeric criterion that USEPA has proposed in the COPC document, which was adopted as a secondary clearance value for this project, is 1 pg/m^. Although the value chosen for this project was 1 pg/m®, 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 pg/m^, ranging from 17.2 to 22.1 pg/m^ 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 US EPA background study, there was a frequency of detection of 25%, with a range of 4 to 259 pg/m®. Further, the values from the background study without the maximum value of 259 pg/m^ provide a range of 4 to 28 pg/nr. 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.

Unfortunately, at 114 Liberty, the silica test method detection limit of 11 pg/m’ was much higher than the health-based benchmark set by EPA (1 pg/m^), and also higher than detection limits in tests EPA used in other affected residences and it its background study of midtown Manhattan (detection limit of 4 pg/m^).

Furthermore, the detection limit was even lower for EPA’s cleaning study at EPA’s 110 Liberty St cleaning study. “ The detection limit was 0.007 pg/m^, and silica was quantifiable at 0.008 pg/m^. Undoubtedly, the detection limits were very low at 110 Liberty St. because the building had undergone several rigorous abatements by EPA/NYCDEP. ’’

It could well be that EPA/NYCDEP used much better cleaning methods at 110 Liberty St. than it did at 114 Liberty St. This is because the detection limit for silica is related to the “dirtiness” of the sample, or sample overload. If EPA had conducted a thorough enough cleaning at 114 Liberty, this overloading problem would not have occurred, and the silica detection limits would have been lower.

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