WTC environmental health assessment draft, May 2002

NYC 9/11 Public Portal Document

mi^ht it be)? This should also be discussed because while exposures to certain levels of PM 10 from the WTC may not continue for a full year, they would likely be lonf^er than 24 hours. The same is true of PM 2.5. I don’t think we should only reference exposures to the 24 hour standard. In addition, is the annual standard for PM 2.5 40 ug/m? or 65 ug/nf ?J

Particulate Matter (as fine dust and smoke) in the 10 micron and smaller size range is inhalable and may cause throat and lung irritation. Because of the energy released by the WTC disaster, dust containing particulate matter in this size range was generated. If this dust was had not been able to settle, or there had remained a continuous source of particulates being released into the ambient air, then there would have been a concern that hazardous dust could infiltrate nearby homes and offices. However, ambient monitoring for fine particulate matter in the WTC area has shown that, since late October, the levels of PM 10 (inhalable dust fraction 10 microns and smaller) and PM 2.5 (respirable fraction 2.5 microns and smaller) have been below the level of concern (150 ug/m^ for PM 10 and 40 »g/m^ for PM 2.5).

PMIO 150 ug/m3 NAAQS 24-hour average PM2.5 65 ug/m3 NAAQS 24-hour average ......... 40 ug/m3 Air Quality Index, 24-hour average (moderate impact)

This indicates that there is no continuing concern of hazardous fine particulate matter entering homes and offices in the WTC area. Therefore, it is recommended that particulate matter not be monitored in any further indoor testing.

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CONFIDENTIAL, CITY_21MC100_003423810 SUBJECT TO PROTECTIVE ORDER NO. 2, SEPT. 2008

NYC-WTC_000176181