NYC-WTC_000232959

NYC 9/11 Public Portal Document

which can increase outdoor airborne particulate matter; and recent home renovation activities, which can result in an increase in levels of gypsum, fiberglass, and other materials in air and surface dust.

METHODS

Details on the methods used in the residential sampling investigations are included in the residential sampling plan that is on the New York City Department of Health and Mental Hygiene’s Internet page (http://www.nyc.gov/html/doh/pdf/alerts/indoor 1 .pdf). Printed copies of the plan can be requested from the New York City Department of Health and Mental Hygiene.

A. Sampling Approach

A series of three concentric circles was drawn around the WTC location. The circles were then divided by direction or zone from the WTC (north, south, and west). Attempts were made to obtain access to the same number of residential buildings per zone for sampling. Four residential buildings above 59th Street were selected for testing to determine what levels of fibers and minerals might be routinely found in the city.

Once a building was selected, air and settled surface dust sampling occurred in up to four different locations: an area outdoors near a main entryway to the building; an area inside of the main entry (or other common area); and two residential units. In Io rm cd consent for sampling was obtained and questions were asked about details that could aid in interpreting the sampling results (such as whether the windows were open on the morning of September 11, 2001).

Both air and settled surface dust samples were collected in high traffic or routinely used areas of the space. For example, settled surface dust was collected from areas where individuals frequently walked, not from behind furniture or underneath kitchen apphances. Air sample inlets were at approximately 4 feet in height above the ground/floor surface to provide results more reflective of what might be inhaled.

Attempts were made during air sampling to obtain data that would reflect what might be in the air during periods of high activity. If the selected area was not occupied at the time of sampling, and if there was no central heating or air conditioning system that could result in contaminant migration into another occupied area, aggressive air sampling was conducted. If the area was occupied, the heating or air conditioning system fan was turned on during the period of sampling. This would not represent a period of high activity, but would present data that might be found during typical or normal activity.

B. Samples Taken

Sample collection was conducted from November 4, 2001, to December 11, 2001, for the lower Manhattan area and from December 6-10, 2001, for the comparison buildings above 59th Street. Because of the limited and time critical essence of this investigation, thirty

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