NYC-WTC_000232959

NYC 9/11 Public Portal Document

neither asbestos nor SVF contributed to the elevated fiber counts. Sometimes mineral components of concrete (calcite and portlandite) and mineral components of building wallboard (gypsum, mica, and halite) were detected in air samples at higher estimated levels in lower Manhattan residential areas than in samples taken at comparison residential areas. These detected mineral levels are orders of magnitude below occupational standards. Although the occupational standards do not account for sensitive individuals or extended periods of exposure, they provide a comparison to an established health guidance value. The levels of minerals seen in airborne dust do not pose potential health hazards even for a continuous year of exposure at the highest levels detected.

INTRODUCTION

At 8:45 AM eastern standard time on September 11, 2001, a commercial jetliner struck the north tower of the World Trade Center (One World Trade Center). At 9:03 am, the south tower (Two World Trade Center) was also struck by a commercial jetliner. The south tower began to collapse at 10:05 am. At 10:30 am, the north tower began to collapse. (1,2,3,4)

The collapse of these structures released massive amounts of dust and debris that covered lower Manhattan. Residents were evacuated from many areas south of Canal Street. On September 19, pedestrian and vehicular traffic restrictions for below Canal Street were modified (5). As residents moved back into the areas, they requested information on the safety of the dust and air in the area and the types of cleaning methods that should be used. The New York City Department of Health and Mental Hygiene provided guidance on cleaning for area residents and requested federal assistance in assessing potential exposures to airborne and settled surface dust that entered residential ai’eas following the collapse of the World Trade Center (WTC) buildings.

BACKGROUND A. World Trade Center Towers

The World Trade Center was a complex of 7 buildings on 16 acres surrounding a 5-acre plaza in lower Manhattan. The complex was bounded by Vesey Street on the north. Church Street on the east. Liberty Street on the south, and West Street on the west. The twin towers were the center of the complex. Each tower had 110 floors; the north tower was 1,368 feet tall and the south tower was 1,362 feet tall. Each tower had approximately 43,200 square feet on each floor. There were seven underground levels that contained services, shopping areas, and a subway station. There were two plaza buildings (WTC 4 and WTC 5) on Church Street that had nine stories. WTC 7 was a 47-story office building. Design and structure details of the towers are shown in Table 1 (1,2,3,4,6). Basic location and U.S. Census population information about lower Manhattan is provided in Table 2 and Figures 1 through 4.

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