NYC-WTC_000199701

NYC 9/11 Public Portal Document

Benzene Full-Day Air Monitoring Data Summary for Lower Manhattan WTC Sampling

Totals (for sampling through 01/15/02, in ppb) Total Samples Samples Above Screening Level 8 0 I % Above 0.00% Samples Below 8 Maximum Value (09/283/01): 5 Minumum Value: Not Detected Screening Level*: 20 Average 0.18

0% Benzene is a Volatile Organic Compound, or VOC, found in emissions from burning coal, oil and gasoline and in evaporation at gasoline service stations. These and other sources all contribute to the baseline level of benzene ■Samples Above Screenlog Level found in outdoor air. Benzene is also released ■Samples Below from tobacco smoke.

Benzene levels in urban areas like New York City fluctuate widely, across locations (near idling cars or trucks vs. on the waterfront) and 100% across time (rush hour vs. middle of the night). Routine monitoring involves sampling over a 24-hour period to obtain an average concentration during that day.

Full day air samples have also been taken at eight sites, mainly along the outer edge of the work zone. These measurements, which are comparable to levels seen prior to September 11 in New York City, confirm the rapid dissipation of benzene as you move away from the debris pile and illustrate that over a full day, average levels are much lower than many of the levels captured in the few minute grab samples. These full day air samples are all below EPA's screening level, which was set to be protective against significantly increased risks of cancer and other adverse health effects. This screening level assumes continuous exposure for a year to an average concentration of 20 ppb.

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NYC-WTC_000199701