NYC-WTC_000199699

NYC 9/11 Public Portal Document

Asbestos Air Monitoring Data Summary for Lower Manhattan WTC Sampling

Totals (for sampling through 01/29/02, in s/mm2) Total Samples 5517 Samples Above Screening Level 15 % Above 0. 27 % Samples Below 5502 Maximum Value (12/04/01): 204.44 Minimum Value: Not Detected Screening Level*: 70 Average All 10.54

0%

Samples Above Screening Lexel- All Louver Manhattan Sites

100% The level of concern for asbestos is based on continuous exposure to more than 70 structures per square millimeter for an extended period. In evaluating data from the World Trade Center and the surrounding areas, EPA is using a protective standard under AHERA, the Asbestos Hazard Emergency Response Act, to evaluate the risk from asbestos in the outdoor and indoor air. This is a very stringent standard that is used to determine whether children may re-enter a school building after asbestos has been removed or abated. It is based on assumptions of long-term exposure. EPA has chosen to use this standard, because it is the most stringent and protective, even though it is unlikely that the public will be exposed to asbestos from the World Trade Center site for extended periods of time.

To determine asbestos levels, air filters are collected from monitoring equipment through which air in the school building has passed and viewed through a microscope. The number of structures - material that has asbestos fibers on or in it - is then counted. The measurements must be 70 or fewer structures per square millimeter before children are allowed inside.

There is also a federal standard for asbestos exposure under OSHA, the Occupational Safety and Health Act. which is used to protect workers on-the-job. The standard is .1 fiber per cubic centimeter averaged over an eight-hour day. To be as protective as possible, EPA is using the school re-entry standard in tests around the World Trade Center. Levels above 70 structures per square millimeter do NOT imply an immediate health threat. Asbestos exposure becomes a health concern when high concentrations of asbestos fibers are inhaled over a long period. Illness is very unlikely to result from a single, high-level exposure, or from a short period of exposure to lower levels.

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NYC-WTC_000199699