VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

outdoor surfaces and analyzed for the presence of asbestos by both PLM (polarized light microscopy) and TEM. Asbestos was detected in settled indoor dust in 10 of 57 (16%) lower Manhattan residential units sampled, with the positive samples showing a maximum of 1.5% asbestos in dust. By comparison, no asbestos was detectable in dust samples collected in the 5 comparison residences. In outdoor dust collected at lower Manhattan properties, asbestos was detected in 6 of 14 (43%) samples, with a maximum asbestos concentration in dust of 3.4%.

Volatile Organic Compounds. The Ground Zero samples of volatile organic compounds (VOCs) were generally not taken in the breathing zone of workers and were not representative of the general air quality at the site. Most ofthe data were collected within plumesfrom fires and smoldering rubble to alert the Fire Department ofNew York (FDNY) and the contractors/union health/safety officers working at Ground Zero about conditions that posed immediate health concern to the workers and, as such, were more representative ofemissions rather than exposures. For this reason, an analysis of Ground Zero worker exposures for VOCs was not conducted. However, eleven VOCs were evaluated at sites surrounding Ground Zero. No exceedences ofscreening benchmarks were seen for 1,4-dioxane, ethanol, styrene, tetrahydrofuran, and xylenes. Exceedences ofscreening benchmarks were seen for acetone, benzene, 1,3-butadiene, chloromethane, ethylbenzene, and toluene. Exceptfor benzene, exceedences for these chemicals occurred in restricted zones. Also, the exceedences were all grab samples. Twenty-four hour samples of benzene, 1,3-butadiene, ethylbenzene, and toluene all were about three orders ofmagnitude (1000 times) lower than the grab samples, demonstrating the difference between 4-minute grab samples taken within plumes and day-long averages. The exceedences for benzene were more frequent, some werefurtherfrom Ground Zero than the other VOCs, and the 24-hour samples were lower but within afactor of 10 of the grab sample exceedences. This suggests that elevated concentrations of benzene (above typical background by about a factor of 10) may have been sustainedfor a month or more after September 11.

On the basis of available monitoring data, it is concluded that the exceedences of the screening benchmarks in restricted zones for acetone, 1,3-butadiene, chloromethane, ethylbenzene, and toluene do not represent a public health risk to persons living or working at sites surrounding Ground Zero.

The data for benzene were not as definitive. Because the 24-hour samples were measured at levels that were closer in magnitude to the grab sample exceedences than the other VOCs, within a factor of 10, this would suggest that the grab sample concentrations were closer to sustained concentrations rather than short-term plume concentrations only. Also, these 24-hour concentrations were near the ATSDR Intermediate MRL of 0.004 ppm and higher than the historical average for New York City of about 0.0005 ppm. The data suggest that the possible exposures to benzene at levels that approach the MRL did not last longer than 45 days. Whether or not specific health effects occurred due to exposure to benzene is unknown, but given that the exceedences and elevations above typical background were near Ground Zero and mostly within restricted zones, the data suggests that the exposures to the general population were of minimal concern.

DRAFT-DO NOT QUOTE OR CITE 10 October 2002

NYC-WTC_000149091