NYC-WTC_000233911

NYC 9/11 Public Portal Document

FROM: Laduca, John

TO: Kelpin, Gerry; Kelpin, Gerry 001

COPIED:

BCC:

DATE: 20011004 18:25:30

SUBJECT: Web site text

NYC DEP is monitoring the ambient outdoor air for asbestos. This effort is augmenting ambient air asbestos sampling being done by USEPA and other state and city agencies. There is currently no out door ambient standard for asbestos. The U.S. 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 we are monitoring the ambient outdoor air, we are using this value as a way to characterize the levels of asbestos in the air. Since the measurement protocol used, phase contrast microscopy (PCM), counts fibers, we are doing an additional analysis for all samples that are above 0.01 f/cc. This measurement protocol is called transmission electron microscopy (TEM) and counts the number of asbestos fibers in the sample. Our TEM results will be added shortly. EPA is reporting their data in TEMs.

Results indicate that, as expected, asbestos is present in some of the debris at the site and in areas very close to the site. As of September 28, 2001, most air sampling results outside the security zone were 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 out door ambient air is above .01 f/cc, the samples will be analyzed to determine how many of the fibers are actually asbestos fibers.

John LaDuca NYC Department of Environmental Protection Public Affairs - New Media Communications nyc.gov/dep

CITY_21MC100_003249778

NYC-WTC_000233911