NYC-WTC_000205183

NYC 9/11 Public Portal Document

Air Monitoring in Lower Manhattan Page 1 of 3

re.WG- '‘'GyV , The City of New York OfcP J Department of Environmental Protection

BSBaWj Air, Noise and Hazardous Materials

Air Monitoring in Lower Manhattan DEP is monitoring the ambient outdoor air for asbestos. This effort is augmenting ambient air asbestos sampling being done by the EPA and other state and city agencies. There is currently no outdoor ambient standard for asbestos. The US and NYC standard for asbestos in community and residential buildings is 0.01 fibers/cubic centimeter (f/cc) in indoor air. An indoor area which has had asbestos detected and then removed must show that air samples are at or below the 0.01 f/cc standard before the indoor area can be re-occupied. Although the ambient outdoor air is being monitored, DEP is using this value as a way to characterize the levels of MMB asbestos in the air.

Since the measurement protocol used, phase contrast microscopy (PCM), counts fibers, DEP is also conducting an additional analysis for all samples that are above 0.01 f/cc. This measurement protocol is called transmission electron microscopy Sis (TEM) and counts the number of asbestos fibers in the sample. EPA is reporting their data in TEMs, and provides a good explanation of the interpretation of the standard SI Bi that uses this methodology on their website.

Results indicate that, as expected, asbestos is present in some of the debris at the site a and in areas very close to the site. Between September 28, 2001 and the present, the vast majority of air sampling results outside the security zone have been below the standards for asbestos in indoor air.

As testing continues, there may be the possibility of occasional short-term increases in levels of asbestos in the air above the residential standard of 0.01 fibers per cubic centimeter of air. When the measured level for the outdoor ambient air is above 0.01 f/cc, the samples will be analyzed to determine how many of the fibers are actually asbestos fibers.

To view recent air monitoring results, click on a sampling location below or on the map (Links will open in a new browser window) 1

Sampling Site Location 1 West,Broad way..and 19 Vesey and WQrth.S.ti;eet West Street 2 Broadway and 20 Vesey between Worthstreet Churchjmd Greenwich Street

http://www.nyc.gov/html/dep/htmPairmonit.html 1/11/2002

CITY_21MC100_007220669 NYC-WTC_000205183