2 tables, 1 figure omitted
Following the terrorist attacks of September 11, 2001, which destroyed
the World Trade Center (WTC) in lower Manhattan, the New York City (NYC) Department
of Health and Mental Hygiene (DOHMH) and the Agency for Toxic Substances and
Disease Registry (ATSDR), with assistance from the U.S. Public Health Service
(PHS) Commissioned Corps Readiness Force* and the WTC Environmental Assessment
Working Group,† assessed the composition of outdoor and indoor settled
surface and airborne dust in residential areas around the WTC and in comparison
areas. This report summarizes the results of the investigation, which found
(1) similar levels of airborne total fibers in lower and in upper Manhattan,
(2) greater percentage levels of synthetic vitreous fibers (SVF) and mineral
components of concrete and building wallboard in settled dust of residential
areas in lower Manhattan than in upper Manhattan, and (3) low levels of asbestos
in some settled surface dust in lower Manhattan residential areas.1 Based in part on the results of this investigation,
the U.S. Environmental Protection Agency (EPA) is cleaning and sampling residential
areas as requested by lower Manhattan residents. In addition, to assess any
short- or long-term health effects of smoke, dust, and airborne substances
around the WTC site, DOHMH and ATSDR are developing a registry that will track
the health of persons who were most highly exposed to these materials.
During November 4–December 11, 2001, air and settled surface dust
samples were collected in and around 30 residential buildings within three
concentric circles surrounding the WTC site in lower Manhattan, including
59 residential units.2 In addition, five
residential units in four buildings located north of 59th Street (approximately
5 miles northeast of the WTC site) were sampled for purposes of comparison.
Attention was focused on building material constituents (1) that have irritant
properties (e.g., SVF, including fiberglass and gypsum) or might have negative
long-term health effects (e.g., crystalline silica and asbestos) and (2) that
were reasonably presumed to be either in the initial WTC collapse dust cloud
or in dust generated by subsequent rescue and recovery activities at the WTC
site. All samples collected during the investigation were analyzed for the
presence of asbestos, SVF, crystalline mineral components of concrete (e.g.,
silica, calcite, and portlandite), and crystalline mineral components of building
wallboard (e.g., gypsum, mica, and halite).
At each sampling location, time-weighted air sampling was conducted
for three or four particulate matter (PM) fractions (i.e., PM 100 microns,
10 microns, 4 microns, and 2.5 microns).3- 5 Each
PM fraction was analyzed for crystalline minerals by using X-ray diffraction
(XRD) analysis.6 The XRD analysis for crystalline
minerals was semiquantitative (i.e., estimated). Air samples for fibers were
analyzed first by phase contrast microscopy (PCM).5 If
the concentration of total fibers was higher than the maximum concentration
of fibers found in the comparison homes (0.003 fibers per cubic centimeter
of air [f/cc]), the sample was re-analyzed for asbestos fibers by using transmission
electron microscopy (TEM).5 In addition,
scanning electron microscopy (SEM) to look for SVF was used for PCM fiber
counts >0.003 f/cc if the settled surface dust sample from that area contained
Settled surface dust samples also were taken at each sampling location
and analyzed for crystalline minerals and fibers. Fiber analysis of settled
dust samples for asbestos and SVF was conducted by using polarized light microscopy
(PLM).7 If asbestos levels were below the
detection limit (i.e., <1%), samples were re-analyzed by using TEM.7 The dust samples also were analyzed for crystalline
mineral content by using XRD.
For 111 (94.9%) of the 117 air samples, the concentrations of fibers
found in lower Manhattan residential areas were similar to the concentration
of fibers found in comparison areas (<0.003 f/cc). The six lower Manhattan
areas that had elevated total fiber counts were re-examined by TEM and SEM
to determine the types of fibers; the results indicated that neither asbestos
nor SVF (e.g., fiberglass) contributed to the elevated total fiber counts.
Air sampling results for minerals detected quartz and other building
material constituents in lower Manhattan. No other forms of crystalline silica
were detected in any air samples except for a one-time detection of cristobalite
(15 micrograms per cubic meter [µg/m3]‡). The estimated
concentrations of these minerals in air were low. In some locations, mineral
components of concrete (quartz [not detected (ND)–19 µg/m3‡], calcite [ND–14 µg/m3‡], and
portlandite [ND–95 µg/m3‡]) and mineral components
of building wallboard (gypsum [ND–15 µg/m3‡],
mica [ND–43 µg/m3‡], and halite [ND–19
µg/m3‡]) were detected at higher estimated levels
in air samples in lower Manhattan than in samples collected in comparison
areas. Gypsum was the only mineral detected in the comparison building air
samples (ND–5 µg/m3‡). No other minerals tested
(i.e., quartz, calcite, portlandite, mica, and halite) were detected in comparison
building air samples.
In lower Manhattan, asbestos and SVF were found in some indoor settled
dust samples from residential units and common areas. No asbestos or SVF was
detected in the comparison area dust samples. Quartz, calcite, portlandite,
and gypsum comprised a higher percentage of the dust in 29 samples from buildings
in lower Manhattan compared with eight samples from comparison area buildings.
Only two (2.1%) of the 97 dust samples collected provided enough bulk material
for pH analysis. The samples, which were collected from two outdoor locations
in lower Manhattan, had pH values of 8.6 and 9.8, respectively.
NL Jeffery, MPH, C D'Andrea, MS, J Leighton, PhD, New York City Dept
of Health and Mental Hygiene, New York. SE Rodenbeck, ScD, L Wilder, CIH,
D DeVoney, PhD, S Neurath, PhD, CV Lee, MD, RC Williams, MS, Div of Health
Assessment and Consultation, Agency for Toxic Substances and Diseases Registry.
Exposure to substantial amounts of SVF, mineral components of concrete,
and mineral components of building wallboard might cause skin rashes, eye
irritation, and upper respiratory irritation, all of which were reported more
frequently than expected seasonal rates by community members and first responders
after the collapse of the WTC towers.8- 10 If
the reported irritant effects were associated with WTC-related materials,
these effects would subside once exposure to SVF, mineral components of concrete,
and mineral components of building wallboard ceased. Persons with pre-existing
heart or lung diseases (e.g., asthma) or a previous history of occupational
exposure to these materials might be more sensitive to their irritant effects.
Settled surface dust might become airborne if disturbed, potentially
causing exposures to occur through inhalation. Several worst-case assumptions
were made to assess the potential long-term public health risks for inhaling
airborne asbestos and quartz. These assumptions included (1) that no cleaning
of indoor spaces had occurred or would occur, (2) that all airborne fibers
were asbestos, and (3) that the highest levels detected during sampling represented
long-term air levels. Under these worst-case conditions, prolonged exposure
(i.e., decades) to airborne asbestos and quartz might increase the long-term
risk for persons developing lung cancer and other adverse lung health effects
(approximately one additional case per 10,000 persons exposed). However, persons
who clean their residences frequently as recommended1 or
who participate in the EPA cleaning and sampling program are unlikely to be
exposed to worst-case conditions.
The findings of this investigation are subject to at least two limitations.
First, the results do not necessarily reflect conditions found in other buildings,
the time period immediately after the collapse, or the time period after December
12, when the sampling was completed. Second, a limited number of samples were
obtained from comparison areas to determine NYC background levels of asbestos,
SVF, mineral components of concrete, and mineral components of building wallboard.
The comparison area results might not reflect NYC background levels.
Following the investigation, DOHMH and ATSDR made three recommendations.1 First, because more asbestos, SVF, mineral components
of concrete and building wallboard were found in settled surface dust in lower
Manhattan residential areas than in comparison residential areas, residents
of lower Manhattan were advised to continue cleaning frequently with high-efficiency
particulate air (HEPA) filter vacuums and damp cloths/mops to reduce the potential
for exposure. Second, to ensure the effectiveness of the recommended cleaning,
DOHMH and ATSDR recommended additional monitoring of residential areas in
lower Manhattan and an investigation to define background levels specific
to NYC for asbestos, SVF, mineral components of concrete, and mineral components
of building wallboard. EPA is implementing this recommendation and conducting
this investigation. Finally, lower Manhattan residents concerned about possible
WTC-related dust in their residential areas were advised to request cleaning
and testing from EPA no later than December 31, 2002. EPA is conducting the
requested cleaning and testing of lower Manhattan residential areas.
DOHMH and ATSDR are developing a registry of those persons who were
most highly exposed, including persons living, working, or attending school
in lower Manhattan; persons who responded to the emergency; persons working
at the WTC site or the Staten Island landfill following the attacks; and persons
working in buildings that were damaged or destroyed in the attacks. The registry
will track the health of participants to determine whether their exposures
to smoke, dust, and airborne substances around the WTC site might have any
short- or long-term impacts on their physical health. Additionally, the registry
is intended to track the mental health of the approximately 100,000-200,000
persons who might enroll.
*A cadre of PHS Commissioned Corps officers who can be mobilized during
disaster, strife, or other public health emergencies and in response to domestic
or international requests.
†A group formed on September 15, 2001, that comprises representatives
of the U.S. Department of Health and Human Services, Environmental Protection
Agency (EPA), Department of Labor, and New York State and NYC government and
private organizations to coordinate public health and occupational sampling
and data review among the three federal agencies in support of state and city
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