VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

Broadway and Park Place were not found on October 15, October 16, October 17, and October 22 (the highest value was only 0.002 ppm). The range of sampling results (0.002 to 0.026 ppm) shows the temporal variability in the benzene levels. At 290 Broadway from November 26 through January 3,10 samples were taken. They showed benzene levels to be below the intermediate MRL. At Broadway and Liberty, the sample taken on October 17, the only sample taken after the exceedence on October 8, was below the intermediate MRL at 0.0009 ppm. At Albany and West, 16 samples were taken between October 22 and January 3. They showed the benzene levels to be below the intermediate MRL.

Monitoring results from the EPA-ORD sampling suggest that benzene never exceeded screening benchmarks for more than 45 days. At all the sites there was great temporal variability in the samples. The largest gap between an exceedence of the intermediate MRL and a value below the MRL was only 11 days at West Broadway and Park Place. For 290 Broadway, Broadway and Liberty, and Albany and West, the first samples below screening benchmarks were taken November 26, September 22, and September 23, respectively. If one assumes that exposures began September 11, the worst case exceedences of the intermediate MRL could not have lasted longer than 45, 8, and 18 days, respectively, at 290 Broadway, Broadway and Liberty, and Albany and West. Thus the worst-case, longest possible exposure, would have been 45 days at 290 Broadway.

On the basis of data summarized above, it is concluded that the exceedences measured at Liberty and Trinity, Greenwich and Liberty, W. Broadway and Park Place, Broadway and Liberty and Albany and West were not a public health risk to residents. These sites were in the restricted zone or on the border of the zone, and it is unlikely that residential exposures occurred for extended periods. The samples taken were grab samples (taken within a 4 minute period) and are not representative of the average exposures. Samples taken at Liberty and Trinity and Greenwich and Liberty were purposefully taken at ground level and/or in a plume and are not representative of average breathing zone exposures. The temporal variability of the other samples, as shown by exceedences intermixed between days that were below screening benchmarks, also leads to the conclusion that exceedences of the Intermediate MRL were not sustained for extended periods of time. For exposures lasting less than 14 days, the acute MRL is a more appropriate health screening benchmark, and this value was not exceeded at these sites.

At 290 Broadway, elevated measurements were found as late as October 11 (see Table 10) and exposures could have occurred, as the measurement was taken in a non-restricted zone. In a worst-case scenario, the longest possible exposure would have been 45 days at this site. At this site, measurements were taken on a 16* floor balcony. Whether or not the VOC samples collected at this site are representative of the breathing zone exposures will depend on the meteorology and air mixing at the site. The highest benzene value measured at this site was 0.007 ppm and the intermediate MRL is 0.004 ppm (ATSDR, 1997a). Adverse effects would not be expected at 0.004 ppm, and it is unlikely that adverse effects would occur at 0.007 ppm.

The 24-hour samples are mostly lower than all the grab sample exceedences; only the finding of 0.005 ppm at Church and Dey on September 28 approached the grab samples listed as exceeding the ATSDR Intermediate MRL of 0.004 ppm. This Church and Dey location is on the edge of Ground Zero which was also restricted on September 28. In the northwest direction on

DRAFT-DO NOT QUOTE OR CITE 106 October 2002

NYC-WTC_000149050