VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

unconsciousness. Long-term continued exposures to benzene will depress and may cause damage to the blood-forming system, as seen by a decrease in red and white blood cells, lymphocytes, platelets, and other blood constituents. However, after exposure has ended, red blood cell levels may return to normal. Benzene can also harm the immune system and increase the chances of infection and cancer. Benzene is a known human carcinogen, causing leukemia. Most of what is known about the acute and chronic effects of benzene comes from animal and human studies where decreases in bone marrow function have been measured. The intermediate MRL, 0.004 ppm, was derived from a study in mice, where changes in locomotor activity were seen after exposure to 0.78 ppm benzene for 2 hours a day for 30 days. A 100-fold uncertainty factor was used to derive the intermediate MRL (ATSDR, 1997a).

A total of 332 benzene monitoring results were evaluated at sites surrounding Ground Zero. A summary of the screening benchmarks and exceedences is shown in Table 10. According to sampling notes for other VOCs with the same sample number, all these samples were taken at ground level, and the October 1 measurement was taken at ground level in a plume. Nine measurements taken at Greenwich and Liberty between September 16 and September 26, and on October 2 and October 3, were at levels below 0.02 ppm. From these data, it appears that exceedences did not last more than 5 days. Furthermore, these exceedences all occinred within the restricted zone. At Liberty and Trinity, the exceedence detected was 11 ppm on September 26. According to sampling notes for other VOCs with the same sample number, this measurement was taken at ground level in a plume. Measurements taken on September 16, September 22, September 23, and on October 26 did not show exceedences.

From these data, it appears that the exceedence did not last longer than 32 days and throughout this period was in a restricted zone. Because previous sampling did not show exceedences, it is likely that the measurement was taken deliberately in a plume to represent a worst-case transient exposure.

For the 262 samples recorded in the WTC EPA database for sites surrounding Ground Zero, the minimal detection limit was 0.02 ppm, as compared to the ATSDR intermediate MRL of 0.004 ppm (ATSDR, 1997a). This means that the analytical method could not detect benzene contamination levels below 0.02 ppm. Therefore, one cannot evaluate whether or not the ATSDR intermediate MRL was exceeded because the detection level for the samples was higher than the intermediate MRL. Five samples exceeded the ATSDR acute MRL of 0.05 ppm (ATSDR, 1997a), and these are shown in Table 10. Four samples had values above 0.02 ppm but below the 0.05 ppm level. The rest of the samples in the EPA WTC database were reported to be 0.02 ppm. These values are not reported above. Sample results reported to be below 0.05 ppm (257 sampling results) were not screened against the intermediate MRL.

Results from the 70 EPA-ORD samples show that the OSHA PEL and STEL values for benzene were never exceeded. Since these EPA-ORD samples did have a lower detection than the samples reported on in the WTC EPA database, they could be compared against the ATSDR intermediate MRL of 0.004 ppm. It was found that the ATSDR acute and intermediate MRL values were exceeded a total of 17 times at 4 different sampling sites. At West Broadway and Park Place, 10 samples were taken between November 9, 2001, and January 3, 2002. They showed benzene levels to be below the intermediate MRL. Additionally, exceedences at West

DRAFT-DO NOT QUOTE OR CITE 105 October 2002

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