VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

September 28, at the Vesey and West and the EPA Taga Bus locations showed a very low 24- hour concentration, 0.00081 at Vesey and West and ND at EPA Taga Bus. This demonstrates that concentrations were likely higher in the general direction of plume movement, which on September 28 was likely in the east direction.

Of all the VOC data, the benzene data does suggest that sustained concentrations above the typical New York City background could have occurred for about a month after September 11 outside of Ground Zero. As noted above, the background concentration reported by EPA Region 2 for benzene is about 0.0005 ppm. Four of the nine 24-hour measurements taken on September 28 exceeded this background. The grab sample exceedences were substantially higher than this backgroimd, and there were several exceedences above the ATSDR Intermediate MRL of 0.004 ppm. 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 exposures to the general population were of minimal concern.

1,3-Butadiene: 1,3-Butadiene is found in automobile exhaust, wood smoke, and cigarette smoke, and in the breakdown of other materials. 1,3-Butadiene is almost always found at low levels in urban air samples, but it breaks down very quickly. In sunny weather, the half-life of 1,3-butadiene is only 2 hours. The median concentration of 1,3-butadiene in urban air has been estimated at approximately 0.0003 ppm (ATSDR, 1993).

A total of 304 1,3-butadiene monitoring results were evaluated at sites surrounding Ground Zero. A summary of the available screening benchmarks and exceedences is shown in Table 11. One exceedence of the 1.0 ppm PEL was detected in a ground-level plume on October 1, at 1.5 ppm. On days preceding and following October 1 the levels of 1,3-butadiene measured at this location were below the screening benchmark; in fact, 10 of the 12 samples taken at this location were at 0.002 ppm.

All 24-hour samples were non-detects for 1,3-butadiene.

Chloromethane: Chloromethane is always present in the air at very low levels. Most of the naturally occurring chloromethane comes from chemical reactions that occur in the oceans or that occur when materials such as grass, wood, charcoal, and coal are burned. Reported urban levels of chloromethane have been between 0.00066 and 0.00096 ppm (ATSDR, 1998). The background concentration reported by EPA Region 2 for chloromethane is approximately 0.00029 ppm (the annual average for a Staten Island location for the period 1995-1999; EPA, 2002b).

High-level exposures - above 100 ppm - to chloromethane can cause nervous system damage and adversely affect the liver, kidney, and heart. Lower-level exposures - above 50 ppm - have been shown to cause delayed growth, liver changes, and neurological effects in animals. Data do not exist to determine health effects that would be seen with short-term, very low-level exposures. The EPA-STSC provisional subchronic RfC, the screening benchmark with the lowest acceptable exposure limit, is based on a 2-year animal study that showed neurological effects and liver and kidney damage at 1000 ppm but not at 225 ppm (EPA, 1998).

DRAFT-DO NOT QUOTE OR CITE 107 October 2002

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