VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

EPA; 24-hour samples were not available for chloromethane. These 24-hour sample results are also provided in Tables 9, 10, 11, 13, and 14 to compare with the exceedences (Table 12 is chloromethane).

Chemical-by-chemical summaries of the 6 VOCs that exceeded benchmarks are presented below.

Acetone: Most people are exposed to acetone through consumer product use, including nail polish remover, particle board, and paint removers. Acetone exposure may also occur as a by­ product of exposure to isopropyl alcohol. The typical level of acetone in the air in cities in the United States is about 0.007 ppm (ATSDR, 1994). Acute exposure to acetone at levels above 100 ppm may cause irritation to the nose, throat, lungs, and eyes (ATSDR, 1994).

A total of264 acetone monitoring results were evaluated at sites surrounding Ground Zero. A summary of the screening benchmarks and exceedences is shown in Table 9. All three exceedences were seen at Greenwich and Liberty. Two of the exceedences were on September 28, where grab samples found concentrations of 29 ppm and 22 ppm. On October 1, a concentration of 20 ppm was detected. The other 12 samples taken at Greenwich and Liberty did not show concentrations above 13 ppm, including the samples taken on September 26 and September 27, as well as October 2, October 3, and February 23.

The monitoring data indicate that the acetone level was found to elevated above a typical backgroimd (0.007 ppm as noted above) in grab samples for 4 days only on the end of September and beginning of October just off the southern portion of Ground Zero. Because this would correspond to an acute exposure, the ATSDR acute MRL screening value of 26 ppm (ATSDR, 1994) is most appropriate. This value was only slightly exceeded in one sample on 1 day (29 ppm). The Greenwich and Liberty sampler location was in the restricted zone at the time of the exceedence and it was unlikely that residents would be present in that area.

Twenty-four hour samples were taken on September 27 and for three days in December. As seen in Table 9, these locations bordered Ground Zero and the day-long concentration was nearly 4 orders of magnitude (10,000 times) lower than the grab samples, and well within the range of the cited typical background of 0.007 ppm. This clearly demonstrates that sampling within a “hot spot” can result in very high concentrations that are representative of only the few minutes during which the grab sample is taken .

Benzene: Benzene is widely used in the production of other chemicals. It is also found in crude oil, gasoline, and cigarette smoke. Excluding occupational exposures, the major sources of benzene exposure are tobacco smoke, automobile service stations, automobile exhaust, and industrial emissions. Urban air concentrations of benzene can vary widely, depending on mobile source pollution. One large urban study (ATSDR, 1997a) detected a median benzene level of 0.013 ppm. Background concentrations reported by EPA Region 2 for benzene are 0.00051 ppm and 0.00053 ppm (aimual averages of Brooklyn and Staten Island locations, respectively, over the period 1994 - 98; EPA, 2002b).

Breathing levels of benzene above 100 ppm can cause drowsiness, dizziness, and

DRAFT-DO NOT QUOTE OR CITE 104 October 2002

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