Air Today . . . Gone Tomorrow Article|
Potential Exposures to
Airborne & Settled Surface Dust in Residential Areas of Lower Manhattan Following the
Collapse of the WTC -- NYC, November 4 to Decembe4r 11, 2001
Morbidity and Mortality Weekly Report,
February 21, 2003
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 SVF.
Settled surface dust samples also were
taken at each sampling location and analyzed for crystalline minerals and fibers (Figure).
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.
Air Sampling Results
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.
Settled Surface Dust Results
In lower Manhattan, asbestos and SVF were found in some indoor settled dust
samples from residential units and common areas (Table 1). 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 (Table 2). 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
Reported by: 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
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 recommended (1) or who
participate in the EPA cleaning and sampling program are unlikely to be exposed to
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.
- New York City Department of Health and
Mental Hygiene and Agency for Toxic Substances and Disease Registry. Final report of the
public health investigation to assess potential exposures to airborne and settled surface
dust in residential areas of lower Manhattan. Atlanta, Georgia: U.S. Department of Health
and Human Services, Agency for Toxic Substances and Disease Registry, 2002.
- New York City Department of Health and
Mental Hygiene and Agency for Toxic Substances and Disease Registry. Ambient and indoor
sampling for public health evaluations of residential areas near World Trade Center, New
York, New York: sampling protocol. New York, New York: New York City Department of Health
and Mental Hygiene, 2001.
- American Conference of Governmental
Industrial Hygienists. Documentation of TLVs and BEIs, 7th edition. Cincinnati, Ohio:
American Conference of Governmental Industrial Hygienists, 2001.
- U.S. Environmental Protection Agency.
National ambient air quality standards for particulate matter; final rule. Federal
Register, Part II, 40 CFR Part 50, July 18, 1997.
- CDC. Manual of analytical methods, 4th
edition. Atlanta, Georgia: U.S. Department of Health and Human Services, National
Institute for Occupational Safety and Health, CDC, August 1994.
- EMSL Analytical, Inc. EMSL Laboratory's MSD
0700: operating procedures for the analysis of silica by X-ray diffraction (XRD).
Westmont, New Jersey: EMSL Analytical, Inc., January 2000.
- New York State Department of Health.
Environmental Laboratory Approval Program (ELAP) certification manual. Albany, New York:
New York State Department of Health, March 1997.
- CDC. Self-reported increase
in asthma severity after the September 11 attacks on the World Trade Center---Manhattan,
New York, 2001. MMWR 2002;51:781--4.
- CDC. Injuries and illnesses
among New York City Fire Department rescue workers after responding to the World Trade
Center attacks. MMWR 2002;51(Special Issue):1--5.
- CDC. Community needs
assessment of lower Manhattan residents following the World Trade Center attacks ---
Manhattan, New York City, 2001. MMWR 2002:51(Special Issue):10--3.
* 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 health departments.
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