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EP A/600/P-2/002A
October 2002
External Review Draft
http://www.epa.gov/ncea
Exposure and Human Health Evaluation of Airborne
Pollution from the World Trade Center Disaster
National Center for Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
October, 2002

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DISCLAIMER
This document is a draft. It has not been formally released by the U.S. Environmental
Protection Agency and should not at this stage be construed to represent Agency policy.
Mention of trade names or commercial products does not constitute endorsement or
recommendation for use.
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Table of Contents
Page
Executive Summary
I.	Overall Purpose and Scope of Assessment
II.	Exposure Assessment and Risk Characterization Approach
III.	Monitoring Data
IV.	Evaluation
IV.a.	Particulate Matter
IV.b.	Metals
IV. c.	Polychlorinated Biphenyls
IV.d.	Dioxins
IV. e.	Asbestos
IV.f.	Volatile Organic Compounds
V.	Comment on the First Several Days After September 11
VI.	Data on Occupational and Indoor Exposures
V1. a. Occupational Exposures
V1. b. Indoor Exposures
VII.	Overall Comments and Future Studies
VIII.	References
Appendix A. World Trade Center Health Effects Screening Criteria for Ambient Air Developed
by EPA's Region 2
Appendix B. Table of Monitoring Locations
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List of Tables
Table 1. Inhalation health risk screening benchmarks used in this assessment.
Table 2. Concentrations (maximum and Sept-Oct average) of PM25 and Component Elements
Measured at the EPA/ORD World Trade Center Perimeter Sites and at Four Other Sites in the
Northeast U.S. (PM25 concentrations in |ig/m3; all other components in ng/m3).
Table 3. Summary of PCB monitoring data between September, 2001, and April, 2002.
Table 4. Measured dioxin TEQ air concentrations at the WTC Building 5 monitor, the Church
& Dey monitor, and the Park Row monitor (all units = pg TEQ/m3; NR = not reported; all TEQ
calculated at ND = V2 DL except values in parenthesis, which are calculated at ND = 0).
Table 5. Human exposure and health risk assessment assumptions and results for dioxin TEQs.
Table 6. Locations and concentrations of asbestos exceeding the AHERA level of 70 S/mm2.
Table 7. VOC sampling locations outside of Ground Zero.
Table 8. Locations that showed exceedences of screening benchmarks for VOCs and
restrictions to access.
Table 9. Acetone grab sample exceedences and 24-hour sample monitoring summary.
Table 10. Benzene grab sample exceedences and 24-hour sample monitoring summary.
Table 11. 1,3-Butadiene grab sample exceedences and 24-hour sample monitoring summary.
Table 12. Chloromethane grab sample exceedences monitoring summary
Table 13. Ethylbenzene grab sample exceedences and 24-hour sample monitoring summary.
Table 14. Toluene grab sample exceedences and 24-hour sample monitoring summary.
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List of Figures
Figure 1. Figure showing the shrinkages of the restricted zones in the vicinity of Ground Zero
over time. For example, the area below Canal Street was no longer prohibited after 9/14, and
similarly, the shaded area beneath Chambers Street became available only after 9/27. [Figure
extracted from map supplied by City of New York, Emergency Mapping Center],
Figure 2. Particulate matter monitoring sites, including ORD surface sites (A, C, K) on
the WTC perimeter, the ORD site at 290 Broadway, and NYSDEC sites located elsewhere.
Figure 3. Spread of dense dust/smoke cloud over all of lower Manhattan and drifting to the
E/SE immediately after the September 11, 2001, collapse of the World Trade Center buildings.
Figure 4. World Trade Center plume from intense fires (>1000 °F) during days following
September 11, 2001, with high concentrations of both newly formed fine particles from
combustion and reentrained coarse particles likely being transported upward by convection
processes and being dispersed in the WTC plume over varying NY City areas, depending on
prevailing wind directions and speeds.
Figure 5. ORD-modeled WTC plume dispersion on September 11, 2001, at 12 noon. The
values indicated by red numerals are hourly PM2 5 concentrations (in |ig/m3) measured at pre-
existing NJ and NY State-operated PM monitoring stations in northern New Jersey and New
York City. Red, orange, and yellow shading represent most likely areas of plume dispersion (red
= estimated dilution to 100th to 500th and dark blue = dilution to 
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Figure 10. Satellite photograph of WTC plume lofting from Ground Zero at 11:54 am EDT on
September 15, 2001, and dispersion to the S/SW out over the New York Harbor. (Source:
Mandatory Credit: "spaceimaging.com").
Figure 11. Panel A (top) : Daily PM25 concentrations monitored by EPA/ORD at sites A, C, and
K around Ground Zero perimeter and at 290 Broadway 6 blocks northeast of Ground Zero.
PanelB (bottom): PM2 5 concentrations observed at several extended monitoring network sites
in lower Manhattan within 3 to 10 blocks of WTC Ground Zero.
Figure 12. ORD-modeled WTC plume dispersion on October 4, 2001 at 3:00-4:00 a.m. Note
the general regional elevation of hourly PM2 5 levels (in |ig/m3) indicated by red numerals for
monitoring sites scattered across both northern New Jersey and NYC areas, even outside
modeled areas of likely greatest plume intensity indicated by red shading.
Figure 13. Daily PM2 5 concentrations recorded at NYSDEC PS 64 monitoring site after
September 11, 2001 (9/11/01 to 10/27/01) compared to historic record of 24-hr PM2 5 values at
the same site during prior 2 years (2/23/00 to 9/01/01). Note exceedence of 40 |ig/m3 AQI Level
of Concern on September 13 and likely again on October 4; red portion of bar indicates 24-hr
average if three high hourly values (> 100 |ig/m3) being evaluated for data quality are included in
24-hr average calculation.
Figure 14. ORD measurement of PM2 5 elemental constituents Ca, Si, and K at Ground Zero
perimeter sites and 290 Broadway site.
Figure 15. ORD measurements of PM2 5 elemental composition for S, CI, and Br at Ground
Zero perimeter sites and 290 Broadway site.
Figure 16. ORD measurements of PM2 5 elemental constituents Pb, Cu, and Zn at Ground Zero
perimeter sites and 290 Broadway site.
Figure 17. ORD measurements of PM2 5 elemental constituents As, Pd, and Sb at Ground Zero
perimeter sites and 290 Broadway site.
Figure 18. ORD measurements of PM2 5 elemental constituents Ni, Cd, and Cr at Ground Zero
perimeter sites and 290 Broadway site.
Figure 19. PM2 5 concentrations recorded on rooftop of DOE Facility at Varick St.,
approximately 2.0 miles N/NE of Ground Zero. Note single very high PM2 5 excursion mainly
restricted to morning hours of October 3 (see inset figure for October 3), consistent with ORD
measurements at location A on the WTC north perimeter and Ground Zero plume plot shown in
Figure 2 for October 3.
Figure 20. Ambient air lead concentrations (|ig/m3) at sites within Ground Zero or in lower
Manhattan locations in immediate vicinity of the WTC.
Figure 21. Location of PCB monitoring stations.
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Figure 22. Location of dioxin air monitoring. The locations marked "N" are New York State
Department of Environmental Conservation (NYSDEC) samplers maintained by EPA Region 2
with analysis of the samples by Region 7 (Region 2/7), whereas all other samplers are
maintained by EPA's Environmental Response Team (EPA ERT). See text for discussion of the
differences in the two sets of data from these two air monitoring teams.
Figure 23. Location of asbestos monitoring stations in Lower Manhattan.
Figure 24. Location of asbestos monitoring stations in Staten Island and nearby locations in
New Jersey (note: sampling sites in the Staten Island Landfill identified only by number).
Figure 25. North-South directional analysis for asbestos TEM weekly maximums (taken from
EPA, 2002a).
Figure 26. East-West directional analysis for asbestos TEM weekly maximums (taken from
EPA, 2002a)
Figure 27. Northwest-Southeast directional analysis for asbestos TEM weekly maximums
(taken from EPA, 2002a).
Figure 28. Northeast-Southwest directional analysis for asbestos TEM weekly maximums
(taken from EPA, 2002a).
Figure 29. North-South directional analysis for asbestos TEM weekly maximums (taken from
EPA, 2002a).
Figure 30. East-West directional analysis for asbestos TEM weekly maximums (taken from
EPA, 2002a).
Figure 31. Northwest-Southeast directional analysis for asbestos TEM weekly maximums
(taken from EPA, 2002a).
Figure 32. Northeast-Southwest directional analysis for asbestos TEM weekly maximums
(taken from EPA, 2002a).
Figure 33. Location of VOC monitoring stations outside Ground Zero.
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List of Acronyms and Abbreviations
ACGIH	American Conference of Governmental Industrial Hygienists
ACM	asbestos-containing materials
ADD	Average Daily Dose
AHERA	Asbestos Hazard Emergency Response Act
AIRS	Aerometric Information Retrieval System
AQI	Air Quality Index
As	arsenic
ATSDR	Agency for Toxic Substances and Disease Registry
Br	bromine
Ca	calcium
cc	cubic centimeters
Cd	cadmium
CDC	Centers for Disease Control and Prevention
CI	chlorine
CO	carbon monoxide
Cr	chromium
Cu	copper
DL	detection limit
DOE	Department of Energy
EOHSI	Environmental and Occupational Health and Safety Institute
EPA	Environmental Protection Agency
EPA ERT	Environmental Protection Agency Environmental Response Team
EPA-STSC	Environmental Protection Agency Superfund Toxics Support Center
ESD	Environmental Services Division, of EPA's Region 7 Office in Kansas
City
f	fibers of asbestos
FDNY	Fire Department of New York
FEMA	Federal Emergency Management Agency
GFF	glass fiber filter
HEAS	Human Exposure and Atmospheric Sciences Division, in EPA's NERL
IBB	increment in body burden
K	potassium
kg	kilogram
LADD	lifetime average daily dose
LOC	level of concern
LW	lipid weight
MCL	Maximum Contaminant Level
|ig	microgram
jam	micrometer
MOE	Margin of Exposure
MRL	Minimum Risk Level
NAAQS	National Ambient Air Quality Standard
NCEA	National Center for Environmental Assessment, of EPA's Office of
Research and Development
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ND
Non-detect
NERL
National Exposure Research Lab of EPA's Office of Research and

Development
ng
nanogram
NHEERL
National Health and Environmental Exposure and Risk Laboratory, of

EPA's Office of Research and Development
NIEHS
National Institute of Environmental Health and Safety
NIOSH
National Institute for Occupational Safety and Health
no2
nitrogen dioxide
NOAEL
no-ob served-adverse-effect level
NY
New York
NYC
New York City
NYCDEP
New York City Department of Environmental Protection
NYCDOHMH
New York City Department of Health and Mental Hygiene
NYSDOH
New York State Department of Health
NYSDEC
New York State Department of Environmental Conservation
ORD
EPA's Office of Research and Development
OSHA
Occupational Safety and Health Administration
PAH
polycyclic aromatic hydrocarbons
Pb
lead
PCB
polychlorinated biphenyl compounds
PCM
phase contrast light microscopy
Pd
palladium
PEL
Permissible Exposure Limit
Pg
picogram
PM, PM2 5, PM10
Particulate matter, and PM at less than 2.5 |im and less than 10 |im

diameter
ppb
part per billion
ppm
part per million
PS
public school
PUF
polyurethane foam plug for air monitoring
REL
Recommended Exposure Levels
RfC
Reference Concentration
S
sulfur, or structures of asbestos
Sb
antimony
SF
cancer slope factor
Si
silica
so2
sulfur dioxide
SRIXE
synchrotron radiation-induced X-ray emission
STEL
Short Term Exposure Level
STSC
Superfund Technical Support Center
TEF
toxicity equivalency factor
TEM
transmission electronic microscopy
TEOM
tapered element oscillating microbalance
TEQ
toxic equivalent concentration
TLV
Threshold Limit Value
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TWA
time-weighted average
UR
unit risk, for estimating cancer risk due to inhalation
USGS
United States Geological Survey
VAPS
versatile air pollutant sampler
VOC
Volatile organic compound
WTC
World Trade Center
XRF
x-ray flourescent
Zn
zinc
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FOREWORD
The National Center for Environmental Assessment (NCEA), a major component of the
Office of Research and Development (ORD), is EPA's national resource center for human health
and ecological risk assessment. NCEA conducts risk assessments, carries out research to
improve the state-of-the-science of risk assessment, and provides guidance and support to risk
assessors.
Following the collapse of the World Trade Center towers on September 11, 2001, New
York State and Federal agencies initiated numerous air monitoring activities to better understand
the ongoing impact of emissions from the disaster. This report focuses on these air measurement
data, evaluating them in terms of what is typical for New York City or general urban background
and interpreting it with regard to the potential for human health consequences. The report does
not evaluate exposures possibly faced by rescue or clean-up workers and briefly discusses past
and current indoor monitoring efforts.
The analysis in this report supports three general findings: 1) Persons exposed to the
extremely high levels of ambient particulate matter and its components during the collapse of the
World Trade Center towers and for several hours afterwards were likely to be at risk for
immediate acute (and possibly chronic) respiratory and other types (e.g., cardiovascular) of
symptoms. 2) The first measurements of some of the contaminants were on September 14,
while other contaminants were not measured until September 23. Available data suggest that the
concentrations within and near Ground Zero were likely to be highest in the few days following
September 11. Because there are only limited data on these critical few days, exposures and
potential health impacts cannot be evaluated with certainty for this time period. 3) Except for
exposures on September 11 and possibly during the next few days, persons in the surrounding
community were unlikely to suffer short-term or long-term adverse health effects caused by
exposure to elevations in ambient air concentrations of the contaminants evaluated in this report.
These elevated concentrations were measured mostly within and near Ground Zero, and they
lasted for one to three months after September 11. The monitoring data indicate that air
concentrations decreased to background levels that are characteristic of pre-September 11 levels
in the New York City metropolitan area by around January or February of 2002.
Ultimately, it will be difficult to ascertain with certainty what effects resulted when
people were surrounded by initial clouds of dust, or were subsequently exposed to the elevated
concentrations that are discussed in this report. Epidemiologic studies of the exposed
populations that are being conducted by various agencies and institutions should provide a more
scientifically robust evaluation for future evaluations of health effects.
George W. Alapas
Acting Director
National Center for Environmental Assessment
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AUTHORS, CONTRIBUTORS, AND REVIEWERS
The National Center for Environmental Assessment (NCEA), Office of Research and
Development, was responsible for preparing this document. Matthew Lorber and Herman Gibb,
of NCEA, provided overall direction and coordination of the production effort.
AUTHORS
Executive Summary
Herman Gibb
Matthew Lorber
Linda Tuxen
Section I. Overall Purpose and Scope of Assessment
Herman Gibb
Matthew Lorber
John Schaum
Section II. Exposure Assessment and Risk
Characterization Approach
Section III. Environmental Monitoring
Matthew Lorber
Herman Gibb
Nancy B. Beck
Herman Gibb
Matthew Lorber
Section IV. Evaluation
IV.a. Particulate Matter
IV.b.l. Lead
IV.b.2. Chromium and Nickel
IV.c. Polychlorinated Biphenyls
IV.d. Dioxins
Lester Grant
Joseph Pinto
Lester Grant
Joseph Pinto
Nancy B. Beck
David Cleverly
Matthew Lorber
IV.e. Asbestos
Matthew Lorber
Aparna Koppikar
Paul White
IV.f. Volatile Organic Compounds
Nancy B. Beck
Matthew Lorber
V. Comment on the First Several Days After September 11 Matthew Lorber
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VI.	Data on Indoor and Occupational Exposures	Matthew Lorber
John Schaum
VII.	Comments and Future Studies	Herman Gibb
Matthew Lorber
Nancy B. Beck
VIII.	References
CONTRIBUTORS
The following individuals have also provided valuable support in the review and comment of
this document, as well as supplying text and other materials for individual sections:
Stephen H. Gavett, NHEERL/ORD/US EPA
Sven Rodenbeck, AT SDR
Audrey Galizia, Region 2, US EPA
Barbara Finazzo, Region 2, US EPA
Mark Maddaloni, Region 2, US EPA
Marcus Kantz, Region 2, US EPA
Robert Kelly, Region 2, US EPA
REVIEWERS
Philip J. Landrigan, M.D., M.Sc.
Ethel H. Wise Professor Community Medicine
Chairman, Department of Community and Preventive Medicine
Mount Sinai School of Medicine
One Gustave L. Levy Place
Box 1057
New York, New York 10029-6574
Paul J. Lioy, Ph D
Associate Director
Environmental and Occupational Health Sciences Institute of New Jersey
UMDNJ-Robert Wood Johnson Medical School, and Rutgers University
170 Frelinghuysen Road
Piscataway, NJ 08854
George D. Thurston, Ph.D
Associate Professor
NYU School of Medicine
National Institute of Environmental Medicine
57 Old Forge Rd.
Tuxedo, NY 10987
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Executive Summary
In the days following the September 11, 2001, terrorist attack on New York City's World
Trade Center (WTC) towers, many federal agencies, including the United States Environmental
Protection Agency (EPA), were called upon to bring their technical and scientific expertise to the
national emergency. EPA, other federal agencies, and New York City and New York State
public health and environmental authorities initiated numerous air monitoring activities to better
understand the ongoing impact of emissions from that disaster. These efforts generated an
immense amount of data. Many EPA offices and programs quickly became involved with these
activities, providing scientific, engineering, public health, and management expertise to help
cope with the after effects of the collapse of the WTC towers. EPA Region 2, which includes the
New York City metropolitan area in New York and New Jersey, is the Agency's lead office on
these activities, including the important and complicated task of community outreach and
communication. As part of these activities, Region 2 requested that EPA's Office of Research
and Development (ORD) conduct a human health evaluation of exposure to air pollutants
resulting from the WTC disaster.
The evaluation in this report relies primarily on the analyses of ambient air samples from
monitors located at the perimeter of the WTC Ground Zero and at various other sites in lower
Manhattan and surrounding areas. It is an assessment of the inhalation exposure and potential
human health risk incurred by the general population residing and working in the vicinity of the
WTC. Numerous other efforts have been conducted or are ongoing that address other aspects of
exposure and potential risk associated with the collapse of the WTC towers, including:
1)	Ground Zero worker exposures: This report reviews some of the data collected by the
Occupational Safety and Health Administration (OSHA) and the National Institute of
Occupational Safety and Health (NIOSH) that address the exposures faced by fireman and rescue
workers, but does not explicitly evaluate these exposures.
2)	Indoor exposures: Similarly, this report reviews some of the data collected on indoor
air and dust, particularly a recently completed study by the New York City of Department of
Health and Mental Hygiene (NYCDOHMH) and the Agency for Toxic Substances and Disease
Control (ATSDR). It also provides an overview of the ongoing efforts by EPA Region 2 to clean
apartments and evaluate the quality of indoor air and dust. Future reports by EPA Region 2 will
detail these efforts and monitoring results.
3)	Epidemiology studies: Chapter 7 of this report provides an overview of the types of
studies that are ongoing which will evaluate health impacts experienced by workers and others
known to be in the vicinity of WTC in the days and weeks following September 11, 2001. These
studies are being conducted and sponsored by the National Institute of Environmental Health
Studies (NIEHS), and others.
The ambient air monitoring activities described in this report were undertaken by federal,
state and local agencies which have made their analytical results available to EPA for analysis.
Most of the monitors were placed following the disaster, with the intent of characterizing
outdoor levels of WTC-generated air pollutants at locations surrounding the WTC site at
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different distances. Some monitors for particulate matter (PM), operated by New York State,
existed prior to the disaster.
This report focuses on: PM, metals (lead, chromium and nickel compounds),
polychlorinated biphenyls (PCBs), dioxin-like compounds, asbestos, and volatile organic
compounds (VOCs). These substances are included because monitoring indicated that they
correlated with the disaster site in both time and space, and because they pose a potential
concern for health impacts. PM was generated by the collapse of the WTC buildings, the
recovery and demolition operations, and the lingering fire. Lead and asbestos were believed to
be components of the WTC building materials. PCBs were used as dielectric fluid in
transformers and capacitors. Dioxin and VOCs are produced as a result of combustion and
volatilization from fuels. The assessment is limited to an evaluation mainly of the inhalation of
airborne contaminants, although dust ingestion and dermal contact may also have led to
exposures within and near Ground Zero.
Elevated concentrations of these contaminants were found within and near Ground Zero
for a short period of time after September 11. "Elevated" is used in this discussion to denote
concentrations of a contaminant that were significantly higher, by a factor of 10 or more and
often by factors of 100 or 1000, compared to other measurements of the contaminant taken in the
WTC monitoring program or compared to concentrations that are typically found in New York
City or in general United States urban settings. Many of these elevated measurements were
identified as having occurred in "restricted zones," that is, zones where access was limited to
emergency management and rescue personnel and to other credentialed people. In general, the
monitoring data, even within Ground Zero, indicate that ambient air levels for all of these
substances decreased to background ambient concentrations that are characteristic of pre-
September 11 levels in the New York City metropolitan area by around January or February of
2002.
The analysis in this report finds that:
•	Persons exposed to the extremely high levels of ambient particulate matter and
its components during the collapse of the World Trade Center towers and for several
hours afterwards were at risk for immediate acute (and possibly chronic) respiratory
and other types (e.g., cardiovascular) of symptoms.
•	The first measurements of some of the contaminants were on September 14,
while other contaminants were not measured until September 23. Available data
suggests that the concentrations within and near Ground Zero were likely to be highest
in the few days following September 11. Because there are only limited data on these
critical few days, exposures and potential health impacts cannot be evaluated with
certainty for this time period.
•	Except for exposures on September 11 and possibly during the next few days,
persons in the surrounding community were unlikely to suffer short-term or long-term
adverse health effects caused by exposure to elevations in ambient air concentrations
of the contaminants evaluated in this report. These elevated concentrations were
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measured mostly within and very near Ground Zero, and they lasted for 1 to 3 months
after September 11.
While the conclusions reached in this report represent the current scientific understanding
of the toxicity that these contaminants pose to people, combined with EPA's evaluation of
exposure to these contaminants based on available air monitoring data, it cannot be stated with
certainty what effects resulted when people were engulfed in the initial cloud of dust or were
subsequently exposed to the elevated concentrations that were found. Epidemiologic studies of
the exposed populations that are currently being conducted by various agencies and institutions
should provide a more scientifically robust evaluation for future evaluations of health effects.
The risk evaluation approach taken in most instances was to compare the measured air
levels at locations near Ground Zero to established health benchmarks for inhalation exposure
and to typical urban background levels. OSHA Permissible Exposure Levels (PELs), NIOSH
Recommended Exposure Levels (RELs), and Agency for Toxic Substances and Disease Registry
(ATSDR) Minimum Risk Levels (MRLs) were among the benchmarks included in this
evaluation. Where available, benchmarks established to protect against acute and subchronic
exposures were used. Benchmarks that are intended to protect against exposures lasting over
one year or throughout a lifetime, like the EPA Reference Concentration (RfC), were only used
if other more appropriate benchmark values were not available.
A simple comparison of air measurements to health benchmarks or to typical background
levels can be thought of as a "screening" exercise; the purpose of the exercise is to identify
possible problems. If the majority of samples are much less than a benchmark, in most cases it
would be appropriate to conclude that a health impact is unlikely. Similarly, if most air
measurements are similar to typical background levels, then it can be concluded that emissions
from the WTC are not impacting air or influencing exposure and health. On the other hand, if
most samples exceed a benchmark, then it may be appropriate to consider the possibility that a
health impact may have occurred, or could occur, depending on the circumstances.
Efforts will continue at EPA to further characterize exposures and health impacts that
resulted from the collapse of the WTC Towers, and to build on the risk evaluation presented in
this report. Some additional future considerations could include: evaluating other contaminants
that were measured, evaluating the indoor environment in more depth, evaluating other pathways
of exposure and other exposure media such as dermal contact to contaminated dust, investigating
the combined effects of exposure to more than one contaminant, conducting further toxicity
testing with laboratory animals, and considering results from ongoing epidemiological studies.
Summaries of the findings for each contaminant/class of contaminants are presented
below:
Particulate Matter. People caught in the initial dust/smoke cloud that encompassed lower
Manhattan after the collapse of the WTC buildings on September 11 were briefly exposed (4-8
hours) to quite high levels (in the milligrams per cubic meter, mg/m3, range) of airborne
particulate matter (PM). Also, during the first several days after the disaster, PM levels in the
air at the WTC perimeter exceeded EPA 's daily PM25 NAAQS (65 ngfm3, 24-hr); and PM25
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concentrations at some other nearby lower Manhattan sites exceeded EPA's 40 micrograms per
cubic meter (ng/m3) 24-hour Air Quality Index (AQI) level of concern for susceptible subgroups.
The high PM concentrations recorded very near WTC Ground Zero during late September and
early October may imply increased chronic health risks for the most highly exposed individuals
(e.g., persons spending extended periods of time within the WTC work zone without wearing
protective respirators). By mid- to late October, PM values across lower Manhattan had largely
returned to levels typical of New York City and other US urban areas, with only a few WTC or
nearby sites occasionally approaching or exceeding the AQI level of concern.
Many individuals were exposed for a few hours to very high PM concentrations in the
initial dust cloud that spread over lower Manhattan on September 11. Also, high levels
of airborne particles were detected during the first several days after September 11 at a
few already existing PM monitoring sites scattered across the New York City area.
Hourly or daily fine particle (less than 2.5 |im in diameter, PM2 5) values at some new
sites set up by EPA or New York State exceeded 40 |ig/m3 (though the AQI applies only
to the daily averages).
PM2 5 measurements from newly established monitoring sites around the WTC perimeter
varied widely, depending on wind direction. Daily average (24-hr) PM2 5 concentrations
on some days exceeded 200 |ig/m3 at one WTC perimeter site or another during late
September and early October. However, PM2 5 concentrations decreased rapidly with
distance from the WTC, with few PM2 5 values exceeding the 40 |ig/m3 AQI at
monitoring locations ranging from 3 to 10 blocks away from the WTC. During the entire
period following September 11, PM2 5 values recorded at lower Manhattan sites away
from the WTC perimeter were not markedly different than during periods before or since,
as the New York metropolitan area routinely experiences PM2 5 values near and above the
AQI.
Concentrations of various elements (e.g., calcium, sulfur, silicon, lead, and other metals)
in WTC PM2 5 particles also were enriched above typical background levels on an
episodic basis at sites mainly on or near the WTC perimeter, including on some days
extending into late October and into November.
The issue of alkalinity of WTC dust and its potential as a possible health concern for
exposed individuals is raised by observations by the United States Geological Survey
(USGS) and academic researchers of high pH (> 11.0) of aqueous solutions of settled
WTC dust not leached by rainfall. After late September, indoor exposures to such dust
probably warrant more concern than outdoor exposures for possible acute irritative
effects or more chronic health effects, not only because of the basic nature of some
constituent particles but also because of other unusual features, such as slender
microscopic glass fibers with toxic materials attached to them or very fine particles
composed of unusual combinations of silica coalesced with lead or other toxic materials.
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Metals
Lead. Persons caught in the initial WTC-related dust cloud experienced brief exposures to
high levels of lead (Pb), based on analyses of deposited dust samples. In late September 2001,
air lead concentrations at the WTC perimeter sites reached levels above 1.5 ng/m3 on some
days. However, the air lead levels averaged over 90 days (late September - late November) did
not exceed the EPA National Ambient Air Quality Standard (NAAQS) of 1.5 ng/m3 averaged
over a 90-day period. After mid-October, air lead at all sites in lower Manhattan outside WTC
Ground Zero dropped to levels more comparable with background concentrations typical of
NYC and other northeastern United States urban areas. On the basis of ambient air and dust
data, there is little indication of any substantial health risks being associated with lead
exposures of the general population in lower Manhattan areas around the WTC site.
On several days in late September 2001, 24-hour Pb concentrations at the WTC Ground
Zero perimeter sites exceeded 1.5 |ig/m3. This level was again approached or exceeded
at one or another WTC perimeter site during early October (10/3 -10/5). However,
airborne Pb rapidly decreased with distance from the WTC perimeter sites, with Pb
concentrations on the same days when Pb levels were elevated at Ground Zero being
substantially lower at several locations within 3-10 blocks from the WTC (i.e., mostly
within the 0.11 to 0.63 |ig/m3 range of 24-hour Pb levels observed at some Manhattan
and Brooklyn sites during the 1990's). After mid-October, 2001 Pb readings for all WTC
perimeter sites and other lower Manhattan sites remained below 1.5 |ig/m3, with few
even exceeding 0.5 |ig/m3.
Lead concentrations in bulk dust samples taken close to the WTC within days after
September 11 ranged up to 625 |ig/g (ppm). This level is well below street dust Pb levels
on or near heavily traveled roadways prior to phase-down of Pb in gasoline in the late
1970's, which often were well in excess of 1000 - 2000 ppm, and it compares well with
the 500 - 1000 ppm street dust or soil lead levels found in northeastern or midwestern
U.S. urban areas well into the 1990s.
In general, the observed ambient air lead levels did not appear to pose increased health
risks for the general public. However, susceptible persons (especially any pregnant
women) who may have experienced extended exposures to elevated Pb levels within
WTC Ground Zero work areas while not wearing appropriate respiratory protective gear
or who were exposed to indoor WTC-derived dusts with high Pb loadings could possibly
be at increased risk for chronic health effects. Evaluation of blood lead levels and
pertinent medical records for any pregnant women exposed at Ground Zero or in its
immediate vicinity during late September/early October could provide useful further data
by which to assess any such possible health risks associated with WTC-generated lead
emissions.
Chromium. Samples evaluatedfor total chromium at Ground Zero and at sites surrounding
Ground Zero never exceeded the OSHA PEL of 1 mg/m3 or the ATSDR Intermediate Minimum
Risk Level (MRL) for chromium VIparticulates of 1.0 ng/m3. On the basis of the samples
evaluated, exposures to chromium were not likely to cause any adverse health effects.
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All 21 Ground Zero air samples evaluated for total chromium were collected at Building
5 between September 23 and January 31. Additionally, approximately 512 air samples
collected at sites surrounding Ground Zero were evaluated for chromium, including 86
samples collected at landfills and 16 samples from personal air monitors worn by New
York City fire department personnel. No exceedences of the OSHA PEL or the ATSDR
Intermediate MRL for chromiumVI particulates were detected. However, it was noted
that concentrations in the range of 0.20 and 0.40 |ig/m3 were measured for about a month
month after September 11, to then drop to more typical urban backgrounds less than 0.10
|ig/m3
Nickel. Nickel samples evaluated at Ground Zero and at sites surrounding Ground Zero never
exceeded the OSHA PEL of 1 mg/m3. On the basis of samples evaluated, exposures to nickel
were not likely to cause any adverse health effects.
All 21 Ground Zero air samples evaluated for nickel were collected at Building 5
between September 23 and January 31. Additionally, approximately 637 air samples
collected at sites surrounding Ground Zero were evaluated for nickel, including 86
samples collected at landfills. No exceedences of the OSHA PEL were detected.
Furthermore, and unlike chromium and other contaminants, all measurements from
September 11 on at all sites were at background levels.
Polychlorinated Biphenyls. Of the several hundred polychlorinated biphenyl (PCB) air
measurements available, only one sample was elevated above 100 nanograms total PCB per
cubic meter (ng/m3), at 153 ng total PCB/m3, and only three samples were above 50 ng total
PCB/m3. This compares to typical urban background PCB concentrations in the range of 1 - 8
ng total PCB/m3. After a month, nearly all readings were in the range of typical urban PCB
concentrations or were not detected. There were no exceedences of any short-term occupational
health benchmark, including the NIOSHREL of 1*103 ng/m3 or the OSHA PEL of 5*103 ng/m3.
It is concluded that exposures were of minimal concern for cancer risk.
Several hundred PCB air measurements were obtained at a total of 12 locations in the
vicinity of Ground Zero from September 16, 2001, through April 24, 2002. The highest
PCB air concentration measured was 153 ng PCB/m3, and this occurred on October 2,
2001, at the Ground Zero site, WTC Building 5 SW. Typical urban air concentrations of
PCBs are in the range of 1 - 8 ng/m3. The source of these elevated PCB air
measurements is speculated to be the smoke emanating from the smoldering fires at
Ground Zero. PCBs were entrained in the smoke as a consequence of PCB-containing
materials in the WTC buildings. After November 3, 2001, all of the PCB monitoring
sites showed results consistent with PCB levels in air that are typical of urban areas of the
U.S. A simple screening exercise showed that an incremental lifetime cancer risk due to
exposure to short-term elevation of PCBs would be in the range of 10"8 or lower, which is
judged to be of minimal concern. With respect to non-cancer effects, all PCB air
measurements are several orders of magnitude below No Observed Effect Levels
(NOELs) in experimental animal studies. In addition, levels of PCBs observed near or at
the WTC site are below the NIOSH REL of 1*103 ng/m3 (NIOSH, 2002), and several
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orders of magnitude below the OSHA PEL of 5* 10s ng/m3. The NIOSH REL is an 8-hr
time-weighted average air concentration. It is associated with long-term or repeated
exposures, and is protective of effects on the liver and the reproductive system. The
OSHA PEL is also an 8-hr time-weighted average air concentration. It is associated with
long-term or repeated exposures and is protective of effects on the ski (dermatitis).
Dioxins. Monitoring data indicate that dioxin toxic equivalent (TEQ) levels in air near the
WTC were up to three orders of magnitude higher (1000 times higher) than is typical for urban
areas in the United States. Typical levels for urban areas are 0.1 to 0.2 picograms of TEQ per
cubic meter (pg TEQ/m3), while levels found in Ground Zero and near Ground Zero, starting
September 23 (the date of the first sample taken) and continuing through late November ranged
from 10 to over 150 pg TEQ/m3. Concentrations measured several blocks from Ground Zero
were still elevated above typical urban background, but considerably lower than sites in or near
ground zero, ranging from 1 to 10 pg TEQ/m3 during this same time period. Everywhere these
elevations dropped rapidly, and the data suggest that by December 2001, levels decreased to
background levels. These levels need to be considered in the context of total exposure to dioxin,
95% of which is attributed to dietary intake in normal background settings. Therefore, although
inhalation exposure to dioxin at these elevated air concentrations is significantly higher than
typical inhalation exposure to dioxin, an individual's overall exposure to dioxin may not be
impacted significantly. An exposure and risk screening exercise was conducted with available
monitoring data, and the results suggest that these elevations did not result in a significant
elevation in cancer or non-cancer risk over the background risk for exposure to dioxin-like
compounds.
The monitoring data indicate that, through late November, dioxin TEQ levels in air near
the WTC were distinctly elevated compared with typical levels in urban air. An exposure
and risk screening exercise based on these high concentrations suggest a temporary
elevation in exposures for Ground Zero workers but very minimal impact for nearby
residents and office workers. It is concluded that these potential exposures during 2001
do not constitute a public health concern. Dietary intake of dioxins is much higher than
inhalation intake, and thus, the ambient concentrations of dioxin within and near Ground
Zero, although considerably elevated above typical urban air concentrations of dioxin,
are not as significant as suggested by the orders of magnitude in elevation indicated
above.
However, much of the data obtained from within and near the WTC site are of limited
interpretive value due to high detection limits. When dioxin-like compounds were not
detected in an air sample, the TEQ concentration was determined by assuming that each
dioxin-like compound was present in the air at one-half the detection limit for that
compound. This is typical for calculating dioxin TEQ concentrations, and for other
contaminants as well. Because dioxin-like compound concentrations were considerably
elevated in the ambient air from September through late November 2001 within and near
Ground Zero, these concentrations were able to be measured, despite high detection
limits. Concentrations ranged from 10 to 150 pg TEQ/m3 during this time, which was
between 100 and over 1500 times higher than typically found in urban air.
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The reported TEQ concentrations that were compromised due to high detection limits
ranged in value from 0.5 to 5.0 pg TEQ/m3, which is about 5 to 50 times higher than
normal urban background air concentrations. These measurements came from 9 specific
air samplers which were located within Ground Zero (1 sampler) and near the WTC site
(8 samplers). In general, the dioxin method's detection limit is calculated by dividing the
lowest mass of dioxin that the method can detect by the air that contained that amount,
namely the air that flowed through the sampler. Thus, as more air is drawn through the
sampler, the detection limit is lowered. These 9 air samplers operated for 8-hour periods,
and drew in about 7 m3 of air. They began operation on September 23, 2001.
Three other air samplers were operated for 72-hour periods, and drew in about 1000 m3
of air. These monitors were located several blocks from the perimeter of Ground Zero,
and began operation on October 12. Because much more air was drawn into these
samplers, the detection limits obtained for the dioxin-like compounds were lower, and
TEQ concentrations could be routinely quantified as levels less than 1.0 pg TEQ/m3. The
first sampling events in October through November in these three monitors resulted in
concentrations that were still elevated above typical background TEQ concentrations, at
between 1 and 10 pg TEQ/m3. Starting at the beginning of December, 2001, and
continuing through the termination of sampling in May of 2002, the measurements in
these samplers decreased to levels that were mostly less than 0.10 pg TEQ/m3. More
detail on these two sets of monitors (the 9 monitors sampling for 8 hours, and the 3
monitors sampling for 72 hours) is provided in Section IV.d below.
All the reported TEQ measurements from these 9 monitors for 2002, and the
measurements from them in upwind conditions during 2001 (i.e., when the plume was
moving in a direction opposite the monitors), were in this one-half detection limit range
of 0.5 to 5.0 pg TEQ/m3. Thus, the ability to assess exposure during the early months of
2002, where there may have been elevations near Ground Zero as a result of cleanup
activities, was compromised. Because the health risk from dioxin exposure is associated
with accumulation of residues in body tissues, continued dioxin TEQ exposure within
and near Ground Zero throughout 2002 could not be evaluated. The risk screening
exercises conducted for dioxin were limited to the time period when the concentrations
were highest and dioxin was detected. This issue is described in more detail in Section
IV.d.
Asbestos: The large majority of outside air measurements of asbestos were below established
benchmarks and within the range of typical background levels. However, and similar to other
contaminants, the few exceedences that were measured occurred near September 11 in time and
close in proximity to the WTC. Limited available evidence suggest the incursion of asbestos to
the indoor environment. A small study which sampled the indoor environment of two
apartments on September 18 showed very high indoor levels of asbestos. A larger and more
systematic study which sampled in November and December of2001 suggested that indoor
levels of asbestos in dust were slightly higher near the WTC as compared to indoor levels in dust
further away. Current efforts by the EPA focus on the measurement and clean-up of residential
apartments near the WTC.
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A total of 12,676 ambient samples in lower Manhattan were measured by phase contrast
light microscopy (PCM, used to identify structures greater than 5 |im in length), and
8,872 of these were also measured by transmission electronic microscopy (TEM; used to
identify structures less than 0.5 |im in length). Only 23 samples were found to exceed the
Asbestos Hazard Emergency Response Act (AHERA, which uses the TEM measurement
technique) abatement standard of 70 structures per square millimeter (S/mm2), and there
were no exceedences of the OSHA PEL (which uses the PCM measurement technique) of
0.1 fiber per cubic centimeter (f/cc). Most of the exceedences of the AHERA standard
occurred during September 2001 adjacent to Ground Zero in "restricted zones". The
highest concentrations of PCM-measured fibers in ambient air were recorded during the
30 days following September 11, 2001, at sites in the vicinity of the WTC.
Concentrations during this time were in the range of 0.04 to 0.08 f/cc. There has been a
steady decline in the asbestos levels through the first few months of 2002, to correspond
to a steady background state of ND to <20 S/mm2 as measured by TEM and in the range
of 0.003 f/cc as measured by PCM, a level which is typical for urban background.
A slightly higher occurrence rate of AHERA exceedences occurred within the exclusion
zone at the Staten Island Landfill; 51 out of 5,207 samples taken. Most of the
exceedences occurred during October and November 2001, corresponding to the time
that most of the debris was being unloaded. Only one sample in Queens was above 70
S/mm2, whereas no exceedences were observed in the other boroughs of NYC or in New
Jersey.
The highest measurements of asbestos available for evaluation in this report were taken
within two apartments sampled on September 18, 2001. One apartment was highly
affected by the collapse of the WTC towers with completely shattered windows and dust
piled throughout the apartment. The other was in a building that had little exterior
damage, but had visible dust on surfaces within the building and in the apartment
sampled. In the severely damaged apartment, five air measurements of asbestos ranged
from 6277 to 10,620 S/mm2 using the AHERA protocol. One sample taken just outside
on a window ledge of this apartment measured 548 S/mm2. However, it is likely this
high reading was influenced by the air quality on the inside of the apartment, which
showed exceedingly high asbestos concentrations, and was likely not representative of
outdoor concentrations. The six indoor samples in the less impacted apartment exceeded
the 70 S/mm2 AHERA standard at levels ranging from 141 to 379 S/mm2. A rooftop
sample at this location was low at 6.5 S/mm2.
A systematic study of residential apartments by the NYCDOHMH and the ATSDR
showed very little impact to residential apartments compared with this September 18
study, but still a difference between apartments in lower Manhattan and comparison
apartments. From November 4 through December 11, 2001, environmental samples were
collected in and around 30 residential buildings in lower Manhattan. In addition, four
buildings above 59th Street were sampled and used as a comparison area for this
investigation. Importantly, asbestos was not detected above background levels in air
samples in all apartments sampled (with background defined as 0.003 f/cc, a level which
is typical for urban background). Bulk dust samples were collected both indoors and on
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outdoor surfaces and analyzed for the presence of asbestos by both PLM (polarized light
microscopy) and TEM. Asbestos was detected in settled indoor dust in 10 of 57 (16%)
lower Manhattan residential units sampled, with the positive samples showing a
maximum of 1.5% asbestos in dust. By comparison, no asbestos was detectable in dust
samples collected in the 5 comparison residences. In outdoor dust collected at lower
Manhattan properties, asbestos was detected in 6 of 14 (43%) samples, with a maximum
asbestos concentration in dust of 3.4%.
Volatile Organic Compounds. The Ground Zero samples of volatile organic compounds
(VOCs) were generally not taken in the breathing zone of workers and were not representative of
the general air quality at the site. Most of the data were collected within plumes from fires and
smoldering rubble to alert the Fire Department of New York (FDNY) and the contractors/union
health/safety officers working at Ground Zero about conditions that posed immediate health
concern to the workers and, as such, were more representative of emissions rather than
exposures. For this reason, an analysis of Ground Zero worker exposures for VOCs was not
conducted. However, eleven VOCs were evaluated at sites surrounding Ground Zero. No
exceedences of screening benchmarks were seen for 1,4-dioxane, ethanol, styrene,
tetrahydrofuran, and xylenes. Exceedences of screening benchmarks were seen for acetone,
benzene, 1,3-butadiene, chlorome thane, ethylbenzene, and toluene. Except for benzene,
exceedences for these chemicals occurred in restricted zones. Also, the exceedences were all
grab samples. Twenty-four hour samples of benzene, 1,3-butadiene, ethylbenzene, and toluene
all were about three orders of magnitude (1000 times) lower than the grab samples,
demonstrating the difference between 4-minute grab samples taken within plumes and day-long
averages. The exceedences for benzene were more frequent, some were further from Ground
Zero than the other VOCs, and the 24-hour samples were lower but within a factor of 10 of the
grab sample exceedences. This suggests that elevated concentrations of benzene (above typical
background by about a factor of 10) may have been sustainedfor a month or more after
September 11.
On the basis of available monitoring data, it is concluded that the exceedences of the
screening benchmarks in restricted zones for acetone, 1,3-butadiene, chloromethane,
ethylbenzene, and toluene do not represent a public health risk to persons living or
working at sites surrounding Ground Zero.
The data for benzene were not as definitive. Because the 24-hour samples were
measured at levels that were closer in magnitude to the grab sample exceedences than the
other VOCs, within a factor of 10, this would suggest that the grab sample concentrations
were closer to sustained concentrations rather than short-term plume concentrations only.
Also, these 24-hour concentrations were near the ATSDR Intermediate MRL of 0.004
ppm and higher than the historical average for New York City of about 0.0005 ppm. The
data suggest that the possible exposures to benzene at levels that approach the MRL did
not last longer than 45 days. Whether or not specific health effects occurred due to
exposure to benzene is unknown, but given that the exceedences and elevations above
typical background were near Ground Zero and mostly within restricted zones, the data
suggests that the exposures to the general population were of minimal concern.
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Air Concentrations During the First Several Days After September 11: An event such as
September 11 demonstrates that the greatest environmental impacts occur in the first 24 to 48
hours and in areas close to the site. Difficulties associated with site access and security, power
supply sources, equipment availability and analytical capacity hindered efforts by EPA and the
New York State Department of Environmental Conservation (NYSDEC) to put air monitors in
place immediately after the attack. While dust samples were collected for analysis on September
11, the first air samples of some of the critical contaminants were not taken until September 14,
such as asbestos, while other contaminants were not sampled until September 23, such as dioxin.
Rapid initiation of monitoring will allow the measurement of air concentrations that can be very
important for evaluation of inhalation exposures and potential short and long-term human health
impacts. An examination of the concentrations measured during September show that the
highest concentrations were the ones taken closest in time to September 11, closest in proximity
to Ground Zero, and in the downwind direction. For example, five measurements of dioxin
TEQs were over 100 pg TEQ/m3 (all others were under 100 pg TEQ/m3), and these were the first
measurements in the three nearest downwind monitors: the first 3 measurements in the WTC
Building 5 monitor on September 23 (160 pg TEQ/m3), October 2 (170 pg TEQ/m3), and
October 4 (170 pg TEQ/m3), the first measurement at the Church and Dey monitor on September
23 (130 pg TEQ/m3), and the first measurement at the Liberty and Broadway monitor on
September 23 (100 pg TEQ/m3). While the highest dioxin measurements were found on
September within and to the east of Ground Zero, three samplers to the west of Ground Zero
showed background levels of dioxins on September 23. Similar trends were seen for other
contaminants. It is reasonable to conclude that air concentrations within and very near Ground
Zero would have been at least at these high levels and probably higher during the first several
days after September 11. These areas were in restricted zones, which minimized overall
exposures, and exposures were further minimized for individuals who used protective gear and
clothing.
Occupational and Indoor Exposures: Extensive data sets are available from OSHA and
NIOSH on occupational exposures on the Ground Zero site. Many of these samples were
personal air monitors, and as such, are the most appropriate types of samples for evaluating
inhalation exposures of workers. The contaminants evaluated in this report and many more are
included in these data sets. The vast majority of samples in both data sets were below
occupational standards including OSHA PELs and NIOSH RELs. The ATSDR has completed a
study of residential apartments (NYCDOHMH/ATSDR, 2002). Testing occurred between
November 4 and December 11, and included 57 apartments in lower Manhattan as well as 5
comparison apartments. In all tested apartments (lower Manhattan and comparison), airborne
fibers were not detected above background levels in any of the indoor air samples. However,
bulk dust samples showed asbestos in 16% of the apartments in Lower Manhattan, and none in
the comparison apartments. Also, synthetic vitreous fibers (SVF or fibrous glass) were found in
both indoor and outdoor samples in Lower Manhattan. Another study sampling indoor air and
dust on September 18 in 2 locations very near Ground Zero found significantly high
concentrations of asbestos in both air and dust, but low, background, concentrations of dioxin,
PCBs and metals.
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Exposure and Human Health Evaluation of Airborne Pollution from
the World Trade Center Disaster
Section I. Overall Purpose and Scope of Assessment
The purpose of this document is to provide a preliminary assessment of the potential
human health impacts associated with exposures to emissions caused by the September 11, 2001,
collapse of the World Trade Center (WTC) towers. This assessment focuses on a disaster that
has already occurred, and it became a challenge to evaluate the seriousness of health impacts that
may have resulted (or may still result) from past exposures to contaminants. This situation
presents problems that are different from those faced in analyses to support the proactive
establishment of environmental standards, to determine emission limits from air sources, and in
similar regulatory venues where risk assessment procedures are used. In such circumstances,
risk managers can make an active choice regarding the level of protection that is to be achieved
and how uncertainties will be weighed in that process. In addressing exposures resulting from
the WTC attack, those options are not available. Accordingly, this report attempts to take a
practical, integrative approach to evaluating and conveying the potential impacts and their
seriousness from a public health perspective.
Six contaminants/contaminant classes were evaluated in this assessment. These
included: particulate matter (PM), metals (lead, chromium, and nickel), polychlorinated
biphenyls (PCBs), dioxins, volatile organic compounds (VOCs; benzene and several others), and
asbestos. Although hundreds of different substances have been measured in various media, these
substances were selected for evaluation because monitoring indicates that they correlate with the
disaster site in both time and space, and because they pose a potential concern for health impacts.
PM was generated by the collapse of the WTC buildings, the recovery and demolition
operations, and the lingering fire. Lead and asbestos were believed to be components of the
WTC building materials. PCBs were likely used as dielectric fluid in transformers and
capacitors. Dioxin and VOCs are produced as a result of combustion and volatilization from
fuels. A screening of all substances was not possible in the time available. Instead, a judgement
was made that the above listed chemicals might pose the greatest health concerns. Other
contaminants may be evaluated in later reports.
Potentially exposed populations could include anyone who lives or works in the vicinity
of WTC, such as cleanup workers, office workers, merchants, or residents. Available data were
not always sufficient to evaluate the potential impacts to all populations from all contaminants.
For example, it was decided that monitoring data for VOCs at Ground Zero could not be used to
evaluate VOC exposure to Ground Zero workers. The reasons for this are twofold. First, most
of the EPA data for VOCs at Ground Zero came from simple grab samples taken within plumes
and within rubble piles. The principal purpose for this sampling strategy was to understand the
source emissions of VOCs from the WTC rubble and fires, and to alert the Fire Department of
New York (FDNY) and the contractors/union health/safety officers working at Ground Zero
about conditions that posed immediate health concern to the workers. As such, these data were
deemed not appropriate for evaluating human exposure and potential health impacts. Second,
analyses of exposure of Ground Zero workers to VOCs were conducted by the Occupational
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Safety and Health Administration (OSHA) and the National Institute for Occupation Safety and
Health (NIOSH), who employed personal air monitors for their analysis. These monitors are
much more appropriate for human exposure assessment. The OSHA data, as posted on their
website (http://www.osha.gov), are summarized in Section VI. The NIOSH data are also
summarized there, with a reference provided for further information (CDC, 2002).
On the other hand, an evaluation of Ground Zero worker exposure was conducted for
dioxin-like compounds. Unlike the case with VOCs, the dioxin monitors were stationary high-
volume monitors operating for 8-hour periods. High concentrations captured by these monitors
in the few months after September 11 are representative of air quality to which unprotected
workers were potentially exposed (i.e, those not wearing respirators). Exposures to asbestos at
the Staten Island Landfill were also evaluated using ambient air data. Although workers were
not specifically identified as the exposed population, conservative assumptions in an exposure
and risk assessment suggest that even continuous exposure for the limited time period when
asbestos at the Landfill may have been elevated would not have resulted in exposures that
suggest a potential human health risk.
Exposures that were specific to the indoor environment were also not explicitly addressed
in this assessment. Section VI describes completed and ongoing studies which have measured
levels of contaminants, mostly asbestos, in indoor environments. A major study completed by
the Agency for Toxic Substances and Disease Registry (ATSDR) is summarized in that section.
Also, EPA Region 2 is currently conducting indoor measurements during the clean-up of
residences in lower Manhattan. Clearly, this will reduce future indoor exposures. It is expected
that this EPA effort, and future compilations of all available indoor data, will allow for a more
complete evaluation of impacts on residents and office workers to contaminants that were
present as a result of the collapse of the WTC Towers.
This assessment focuses on the inhalation pathway. Exposure can potentially occur via
inhalation, dust ingestion and dermal contact with contaminated dust on surfaces. Dermal
contact and dust ingestion were not assessed due to a lack of appropriate data and reliable
methods. For residents, contacts with contaminated dust will occur mostly indoors where people
spend the majority of their time. The health assessment conducted in this study assumed that
ambient air measurements were representative of long- and short-term exposures. In some cases,
this could be misleading or inappropriate, particularly if indoor concentrations are higher than
outdoor concentrations. It is emphasized that the evaluations in this document focus on ambient,
outdoor measurements.
Because of the difficulties in setting up an effective monitoring program in such
circumstances, very little data for most chemicals were collected prior to September 18, 2001. As
a result, exposures occurring on September 11 and during the week after are poorly
characterized. It can reasonably be assumed that the concentrations within and near Ground
Zero would have been at least as high and more likely higher than the first measurements taken
near September 18. Section V reviews this hypothesis and demonstrates that, for many critical
contaminants, the highest concentrations were the first ones taken. The individual contaminant
assessments address this lack of data in different ways. For dioxin, it was assumed that the first
concentrations measured on September 23 were representative of the period between September
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11 and that first measurement. For some chemical classes, like VOCs, an exposure and health
evaluation for this time period cannot be conducted because the data do not exist. This could be
critical for benzene, for example, which could have been present at very high levels near
September 11 due to volatilization from gasoline and aviation fuel. EPA-ORD researchers are
working to use modeling and available data and meteorological information to reconstruct
probable exposures for some contaminants such as PM. Some preliminary results of plume
dispersion are included in this report. When this and other work on immediate post-September
11 issues has been completed, further health evaluations of this critical window may need to be
conducted.
Similarly, data regarding contaminant levels prior to September 11, or levels that might
be considered background and typical for New York City (NYC), do not exist for all compounds
because such measurements have not been performed routinely in all urban areas. Where
information specific to NYC is available, such data are discussed. Otherwise, general urban or
general background concentrations are identified and used to place the post September 11
monitoring results in perspective.
This assessment evaluates the potential for health impacts from the exposures that have
occurred from September through about April of 2002. Most monitoring was discontinued in
July of 2002, but data only through April was available at the time this evaluation was
conducted. The air concentration data shows that, by April 2002, initially high levels decreased
to background levels, with most reaching background by December 2001. However, the data
collected between April and July, 2002, will be examined in the coming year to see if there were
any elevations which could change the findings presented in this report.
As more data become available, further assessments may be conducted in order to
evaluate more chemicals, more pathways, the indoor environment, the period between April and
July, 2002, and other identified data gaps. Local and Regional needs, peer review and public
comments on this assessment, and professional judgment will be used to determine the direction
of future assessments.
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Section II. Exposure Assessment and Risk Characterization Approach
Exposure assessments and risk characterizations for all contaminants focus on the
inhalation pathway. For most chemicals, potential health risks are evaluated by comparing the
measured air levels at locations near Ground Zero to established benchmarks for inhalation
exposure and to typical urban background levels. Occupational Safety and Health
Administration (OSHA) Permissible Exposure Limits (PELs), National Institute for
Occupational Safety and Health (NIOSH) Recommended Exposure Levels (RELs), and Agency
for Toxic Substances and Disease Registry (ATSDR) Minimal Risk Levels (MRLs) are among
the benchmarks included in this evaluation. Where available, benchmarks established to protect
against acute and subchronic exposures are used. Benchmarks that are intended to protect
against exposures lasting more than one year or throughout a lifetime, such as EPA's Reference
Concentrations (RfCs), were only used if other more appropriate benchmark values were not
available. Table 1 provides a summary of the inhalation benchmarks used in this analysis.
EPA's Region 2, in consultation with federal health agencies, also used benchmark
values to compare with measured air concentrations. These are described and listed in Appendix
A, and are also cited on EPA's WTC web site: http://www.epa.gov/wtc. Region 2 used existing
standards where appropriate, and for other contaminants, developed unique standards
specifically for the purpose of evaluating the air measurement data from the WTC site. Some of
the existing standards which they used included occupational standards such as OSHA PELs,
which were used for all site workers conducting response/demolition activities covered by
OSHA, and environmental standards such as National Ambient Air Quality Standards (NAAQS:
e.g., for lead) and the Asbestos Hazard Emergency Response Act (AHERA) level of concern for
asbestos to evaluate monitoring data from the site perimeter and beyond where residents or non-
WTC site workers may have been exposed. In cases where appropriate standards did not exist,
the Region developed risk-based screening criteria. The risk assessment paradigm detailed in
EPA's "Hazard Evaluation Handbook: A Guide to Removal Actions" (HEH; EPA, 1997b) was
employed in the development of these risk-based criteria. Screening levels that the Region
developed reflect the most current toxicity criteria (Slope Factors and RfCs) on EPA's IRIS
database (http://www.epa.gov/iris). The Region developed benchmark values for cancer and
non-cancer effects. Details of the Region's derivation procedure are provided in Appendix A.
Some of the benchmarks used by the Region were also used as benchmarks in this report,
such as the AHERA standard, while others were not. The unique benchmarks developed by
Region 2 for evaluating WTC air measurements were not used in this report. The Region needed
to develop and utilize those benchmarks in order to provide daily data reports that were readily
understandable. Only existing benchmarks were used in this report, and in some cases, cancer or
non-cancer screening exercises that went beyond a simple comparison to a benchmark were
employed (e.g., dioxin-like compounds, see discussion below). Efforts are underway within
EPA to develop benchmarks and similar standards to evaluate the impacts from a short-term
inhalation exposure such as that experienced by some individuals at the WTC site. One such
effort entails the development of Acute Exposure Guideline Levels. Final AEGLs are available
for some contaminants, such as vinyl chloride, methylene chloride, methyltrichlorosilane, and
others, but finalized (or draft) AEGLs are not currently available for the contaminants evaluated
in this report.
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A simple comparison of an air measurement and a health benchmark can be thought of as
a "screening" exercise; the risk assessor is screening for possible problems. If the majority of
samples are much less than a benchmark, then in most cases it would be appropriate to conclude
that a health impact is unlikely. On the other hand, if most samples exceed the benchmark, then
it may be appropriate to consider the possibility that a health impact may have occurred, or could
occur, depending on the circumstances.
For dioxin toxic equivalent (TEQ) exposures, the air monitoring data are additionally
used to conduct an assessment on cancer and noncancer risk. This involved defining the
exposure scenario in greater detail, quantifying exposure within these scenarios for purposes of
cancer risk estimation, and modeling the change in body burden over the exposure period for
non-cancer assessment. Simple cancer screening exercises are also conducted for PCBs and
asbestos. Insufficient information about the other chemicals precluded similar modeling. Where
the data allowed, the best possible screening approach appropriate to each chemical class is used
to evaluate potential health consequence from measured air concentrations.
In order to characterize exposure and risks, it is necessary to characterize the duration of
exposure. Immediately following the collapse of the WTC towers, the NYC Mayor's Office of
Emergency Management restricted access to the WTC and surrounding sites. From September
11 through 14, this restricted zone included lower Manhattan south of 14th Street. Figure 1
shows the zones restricted after September 14. The areas in Figure 1 that are identified by a date
show when those areas became accessible to the general public. Further details and additional
maps can be found at,
http://www.nyc.gov/html/oem/html/other/restricted_zones/frozen_zone_history_pdf_page.html.
When a zone was restricted, all pedestrian and vehicular traffic was limited to emergency
management and rescue personnel and other credentialed people. Residents were not allowed to
occupy homes located in the restricted zones. Although some people in certain areas might have
come and gone quickly (for example, to collect pets), noone was living or spending a significant
amount of time in these areas unless they were part of the rescue, recovery and cleanup
operations. As of mid-May, 2002, there were 15 residential buildings in the restricted zone.
As described below, the collapse of the WTC towers resulted in exceedences of screening
benchmarks. However, most of these exceedences were in restricted zones and persons who live
and routinely work in these areas were unlikely to have been exposed. Regardless of the level of
contamination that may be present, if there is no exposure there is no human health risk. In
discussions below, the timing and location of all exceedences are identified, and it is noted
whether the location was in a restricted zone at the time of exceedence. These restricted zones
also influenced the development of "exposure scenarios" that were used in some of the
contaminant-specific evaluations.
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Table 1. Inhalation health risk screening benchmarks used in this assessment.
Agency
Screening Benchmark
I. Short-Term Exposures
OSHA
Permissible Exposure
Limit (PEL)
The maximum allowable exposure to a concentration of
a substance in the air. PELs are set to protect workers
and are based upon an 8-hr time-weighted average
exposure. PELs are enforceable standards.
OSHA
Short Term Exposure
Limit (STEL)
A 15-minute time-weighted average that should not be
exceeded at any time during a workday. STELs are
enforceable standards.
AT SDR
Acute inhalation
Minimal Risk Level
(MRL)
An acute MRL protects against exposures that may last
1-14 days. An MRL is defined as an amount of
chemical that gets into the body (i.e., dose) below which
health effects are not expected.
AT SDR
Intermediate inhalation
Minimal Risk Level
(MRL)
An intermediate MRL protects against exposures that
may last 15 - 364 days.
EPA-
STSC
Provisional Sub chronic
Reference
Concentration (RfC)
The STSC subchronic RfC is the exposure level that is
likely to protect humans from adverse health effects
when exposed over a period not exceeding 10% of their
lifetime (usually assumed to be 7 years). These values
are only provisional guidance.
ACGM
Threshold limit value
(TLV)
A recommended exposure limit based on an 8-hour
workday and a 40-hour work week.
NIOSH
Recommended
Exposure Level (REL)
The maximum recommended exposure limit determined
to protect workers.
EPA
Asbestos Hazard
Emergency Response
Act (AHERA) level of
concern
This standard was developed to be applied to asbestos in
schools. School children were not to be allowed back
into an "abatement" area (an area where activities were
undertaken to reduce air concentrations) until several
consecutive readings were less than the AHERA
standard.
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Table 1 (cont'd).
Agency
Screening Benchmark
EPA
Air Quality Index
(AQI)
The AQI provides reference points by which (a) to judge
increasing levels of concern for potential health effects
associated with acute exposures to air pollutants (e.g.,
particulate matter [PM]) for which short-term National
Ambient Air Quality Standards (NAAQS) have been set
and (b) to help guide the public and local government
officials on actions to minimize unhealthy exposures.
EPA
National Ambient Air
Quality Standard
(NAAQS)
National air standards set by EPA (under the Clean Air
Act) to protect against effects on public health and
welfare of major urban air pollutants, e.g., PM. Short-
term (24-hr) NAAQS for PM are more relevant here
than are long-term (annual average) PM NAAQS.
II. Long-Term Exposures
EPA
Reference
Concentration (RFC)
An estimate of a daily exposure to the human population
(including sensitive subgroups) that is likely to be
without an appreciable risk of harmful effects during a
lifetime.
EPA
Cancer Slope Factor
(SF)
An upper-bound 95% confidence limit on the increased
cancer risk from a lifetime exposure to an agent. The SF
is used in conjunction with a dose term, such as the
amount of a chemical inhaled, to conservatively estimate
the potential for incurring cancer within a lifetime as a
result of that exposure.
EPA
Unit Risk (UR)
The UR factor is used to estimate the upper-bound 95%
confidence limit on the increased cancer risk from a
lifetime of inhalation to a contaminant. It is derived
starting with the SF for a contaminant and then
assuming a lifetime of exposure (24 hr/day, 70 yrs).
When using the UR, a concentration corresponding to a
lifetime average concentration should be used.
EPA
Maximum
Contaminant Level
(MCL)
The MCL is the highest level of a contaminant that is
allowed in drinking water. It is an enforceable standard
that is set considering health effects and assuming the
best available treatment technology, while taking cost
into consideration.
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Figure 1. Figure showing the shrinkages of the restricted zones in the vicinity of Ground Zero
over time. For example, the area below Canal Street was no longer prohibited after 9/14, and
similarly, the shaded area beneath Chambers Street became available only after 9/27. [Figure
extracted from map supplied by City of New York, Emergency Mapping Center]
C
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Section III. Environmental Monitoring
Within a month after the disaster, EPA's Office of Environmental Information (OEI)
began compiling the monitoring information generated by various agencies and providing that
information directly to the public on the EPA web site: http://www.epa.gov/wtc. Environmental
monitoring data were made available on a daily basis. EPA also developed three "trend reports,"
dated November 20, 2001; January 24, 2002; and May 1, 2002. Most of these data were made
available to the EPA's National Center for Environmental Assessment (NCEA) in an electronic
form for purposes of this report. These three principal sources - the web site, the trend reports,
and the electronic data base - represent compilations/interpretations of much of the same data.
The sources of data that have been relied upon in the development of this report are
further described below.
The "EPA WTC monitoring database" In the aftermath of the WTC disaster,
many organizations and agencies conducted sampling and monitoring activities to
assess environmental impacts. The New York City Department of Health and
Mental Hygiene (NYCDOHMH) initially requested that these monitoring
organizations forward their results to them so they could be aggregated and made
available for internal use by federal, state and local decision-makers. On
September 25, 2001, NYC asked EPA to assist in the management of these data
by developing a database capable of tracking and reporting on the environmental
data. The Agency delivered on September 28, 2001, the EPA WTC Multi-
Agency Database that houses data from thirteen federal, state and private
organizations (including EPA, the New York State Department of Environmental
Conservation (NYSDEC), and the New York City Department of Environmental
Protection (NYCDEP) who conducted environmental monitoring after the
September 11 disaster. Roughly 95% of all data in the database are from either
EPA or the NYSDEC. This database has been maintained by EPA's Office of
Environmental Information and provided a clearinghouse and comprehensive site
for use by all government agencies responding to the disaster. The database was
provided to the authors of this report in May of 2002, and at the time, was current
as of mid-April, 2002.
Environmental Data Trend Report World Trade Center Disaster (EPA. 2002a).
These reports have been developed by IT Corporation under contract to EPA's
Office of Solid Waste and Emergency Response. IT Corporation has completed
reports dated November 20, 2001; January 24, 2002; and May 1, 2002. This
latest trends report is current to April 24, 2002. These trend reports focus solely
on monitoring data and are summaries primarily of the data included in the EPA
WTC monitoring database.
EPA web site. Most of the data in the EPA WTC monitoring database have been
summarized for the general public on the EPA web site dedicated to information
on the WTC site (http://www.epa.gov/wtc).
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Historical concentrations of metals, VOCs, PM, dioxin, PCBs, carbon monoxide
(CO), nitrogen dioxide (N02), and sulfur dioxide (S02) for the NYC area
provided by EPA Region 2 and found otherwise in the open literature.
Air monitoring data for VOCs and PM that were not part of the EPA WTC
monitoring data base were provided by the ORD National Exposure Research
Laboratory (NERL) staff.
Reports and data developed by non-EPA Agencies involved in sampling at the
WTC site, who used the data for their individual purposes. These data sets are
described when appropriate and include, for example, the Occupational Safety
and Health Administration (OSHA) Sampling Results Summary posted on their
web site (http://www.osha.gov) on 8/15/02, the National Institute for
Occupational Safety and Health (NIOSH) data base (CDC, 2002), and the Agency
for Toxic Substances and Disease Registry (ATSDR) study of indoor residences
(NYCDOHMH/ATSDR. 2002).
Appendix B shows a summary of the monitoring stations that provided air monitoring
data to the EPA WTC monitoring database that is used in this assessment. Prior to the terrorist
attack on September 11, air monitoring stations for PM already existed at a number of locations
in NYC, including lower Manhattan, upper Manhattan, Brooklyn/Queens, the Bronx, and Staten
Island, as well as New Jersey. Following the disaster, EPA's Environmental Response Team set
up monitoring sites at various locations near the WTC. The strategy employed in positioning the
various "alphabet" monitoring sites was to place the monitors at varying distances surrounding,
but near, Ground Zero. These alphabet monitoring sites are listed first in Appendix B.
Pollutants that have been measured at these locations include polycyclic aromatic hydrocarbons
(PAHs), dioxins, asbestos, PCBs, metals, silica, and PM. The second major set of monitoring
stations listed in Appendix B were established by NYSDEC. These sites have been designated
by numbers to contrast with the alphabet sites. Generally, these sites were further from Ground
Zero. Pollutants monitored at these sites included particulates, VOCs, dioxins, asbestos,
aldehydes, and particle size fractions. In addition, EPA's National Exposure Research
Laboratory (NERL) set up monitoring at three of the alphabet sites (A,C, and K) and at site 16
where monitoring generally for particulates (and metals), VOCs and particle size fractions was
conducted. Finally, the New Jersey Department of Environmental Protection assisted in the
monitoring of asbestos at nearby locations in New Jersey
Laboratories contracted by EPA have conducted most of the pollutant analyses, but EPA
laboratories have done some of the analyses, including some of the dioxin and particulate
analyses. The EPA laboratories that have participated in this effort include NERL's Human
Exposure and Atmospheric Sciences Division (HEAS) in Research Triangle Park, NC, and the
Region 7 Environmental Services Division in Kansas City, KS.
Information on the monitoring procedures and the data includes several other details,
such as dates of monitoring, different monitoring and analytical procedures, and other issues that
are specific to the pollutants. These pollutant-specific issues are discussed in each of the
pollutant sections. Also, each section includes a map showing only those sites where monitoring
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was conducted for the specific pollutant.
Meteorological stations were also established following the attack. Six stations were set
up by the U.S. Department of Interior, and one station was set up by EPA. These meteorological
data, in conjunction with monitoring data, are being used by EPA researchers to model and
recreate the potential exposures that might have occurred immediately after the collapse of the
WTC buildings. Some important preliminary results of the modeling efforts are presented in this
report. The overall modeling analysis, when complete, will be presented in future EPA reports
and assessments.
In addition to air samples, bulk dust, water, river sediments, and drinking water samples
were collected from sites associated with the WTC and surrounding areas to determine the
degree to which the disaster may have caused contamination of these media. Sampling and
analyses were conducted by various agencies, including but not limited to, EPA Region 2, the
United States Geological Survey (USGS), NYSDEC, and the New York State Department of
Health (NYSDOH). Between September 11, 2001, and January 14, 2002, more than 150,000
sampling results were reported for the WTC and other New York and New Jersey sites. Results
were reported for over 500 substances (statistics from the second of three trend reports; the third
is cited as EPA, 2002a).
Although the data generated since September 11 included results for air, bulk dust, water,
river sediments, and drinking water, the focus of this evaluation is on the air sampling, with
some discussion of the bulk dust as it relates to asbestos and other contaminants. It should be
noted that none of the drinking water samples were found to have concentrations that exceeded
any of EPA's Maximum Contaminant Levels (MCLs) for drinking water.
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Section IV. Evaluation
A uniform approach to characterizing the impacts of all pollutants is not possible because
the available background data and screening benchmarks vary between compounds. Similarly,
the relevance of these data for the circumstances of exposure following the WTC disaster also
varies with the type of contaminant being evaluated. When benchmarks are available for the
circumstances at hand they provide a quantifiable approach for assessing the impact of human
exposure. Such benchmarks are used and described, as appropriate.
Background or pre-existing levels of environmental contaminants provide an important
reference point for describing the environmental impact of the destruction of the WTC. If the
monitored levels for a pollutant after the disaster did not appreciably exceed values commonly
found in New York or other urban settings, concerns about elevated health risks will be reduced.
On the other hand, when contaminant levels are in excess of background, a careful evaluation of
the potential health impacts is warranted. Exceedence of background levels does not itself
necessarily imply that potential health risks exist. Also, for some pollutants, background
measurements might at times show substantial levels and have associated health risks. Thus,
comparisons with background levels need to be interpreted in light of the health risk data for the
pollutants.
As discussed below, air concentrations and subsequent exposures after September 11
were generally elevated for each pollutant over a limited span of time. Measured concentrations
for most air pollutants were reduced by the beginning of 2002. Many of the environmental
health criteria have been developed to address "chronic" exposures to contaminants that are
present in the environment for years or decades. Exposure levels that exceed a chronic health
reference level for a limited period would generally be less likely to result in adverse health
effects. Where available, this report has tried to use acute and sub-chronic screening standards.
When chronic screening standards are used, the relevance of the comparison is discussed.
In this report, reference is made to OSHA health criteria for the protection of worker's
health. These criteria are valuable for the analysis of WTC data for several reasons. Criteria
exist for many compounds, not all of which have established environmental health criteria, and
they address risks due to less than lifetime exposures. However, there are limitations in applying
occupational criteria to evaluations of environmental health risks. Occupational criteria serve to
protect relatively healthy worker populations that would typically be less diverse than the
general population (in terms of age and health status). Occupational criteria also apply for
workday periods, with exposures ceasing during nonworking hours; environmental exposures are
typically more continuous. Finally, risk levels that have been accepted in occupational settings
may exceed those accepted for long-term environmental exposures to the general population.
For these reasons, EPA has not generally used occupational standards as a basis for
environmental health criteria.
It is important to reiterate that very limited data are available on the levels of exposure
that occurred to individuals due to direct contact with the plume of smoke and dust generated by
the WTC collapse on September 11. Such exposures would have been of limited duration, but
levels of contaminants may have been significantly higher than those measured in monitoring
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programs that have tracked exposures in New York since that time. This is an issue that
warrants further examination. Also, the ambient monitoring did not begin immediately on
September 12. The earliest reported data are from asbestos monitoring, which began on
September 14. The dioxin monitoring did not begin until September 23. It is highly likely that
air concentrations within and near Ground Zero were highest during these first several days, but
monitoring is unavailable to confirm that hypothesis. This issue is addressed in more detail in
Section V, which observes that the highest concentrations were among the first ones measured.
Many monitoring programs and studies are currently under way to help us understand health
outcomes that have resulted from acute exposures on September 11 and the next several days.
These studies are discussed in the final section of this report.
This report should be viewed as the first phase of an ongoing analysis, and the
conclusions and findings cited below should not be considered the final EPA judgement. At this
point, the available data and analyses are still too preliminary to support reliable quantitative
predictions of potential human health risks. Although a complete quantitative evaluation of the
health impacts of the disaster may never be possible, future EPA analyses will attempt to
develop more quantitative estimates of risks and health impacts using additional exposure-
related data and possibly, the results of epidemiological studies that are currently underway. An
overview of epidemiological studies that are underway is provided in Section VII.
Following are assessments on the individual pollutants.
IV.a. Particulate Matter
Airborne particulate matter (PM) is a complex mixture of inorganic and organic
substances transported in air as solid particles or liquid droplets. PM in ambient (outdoor) air
can typically be divided by size into two groups: fine particles (less than -2.5 |im diameter) and
larger, or coarse, particles (ranging from -2.5 |im to 50 |im or more). Fine PM includes primary
particles formed by combustion (including condensed metal and organic vapors), as well as
secondary aerosols (formed by gas-to-particle conversions). Coarse PM consists mainly of earth
crustal materials formed by natural erosion processes or by human activities such as driving on
paved or unpaved roads, agriculture and mining operations, industry, and
construction/demolition.
PM exposures and associated potential human health risks are addressed in this
preliminary analysis because the collapse of WTC buildings resulted in vast quantities of
structural materials and building contents being crushed and pulverized into airborne particles in
a wide range of sizes, including both fine and coarse particles. These particles, along with
particles and gases emitted from burning jet fuel, aircraft parts, and building debris, formed the
immense dust/smoke cloud that rapidly spread across the NYC area and dispersed over hundreds
of square miles. Thus, PM air monitoring was essential to help characterize potential health
effects resulting from human exposure to the initial dust/smoke cloud, particles produced by the
ensuing fires, and reentrained particles stirred up into the air during recovery activities and
transport of debris away from the WTC site.
Airborne PM exposures are of concern for human health because they can be associated
with a wide variety of adverse human health effects. Some health impacts could include
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respiratory effects (such as lung inflammation and exacerbation of asthma) and cardiovascular
effects (including exacerbation of preexisting chronic heart disease). As with exposures to other
environmental contaminants, potential health impacts depend on PM concentrations and duration
of exposure, as well as the size of the particles inhaled and many other factors (including the age
and health status of exposed individuals). Depending on age and health status, some groups
(such as infants and children, the elderly, and/or individuals with preexisting cardiovascular or
respiratory diseases) may be considered sensitive or susceptible populations to possible effects of
PM exposure.
Particulate matter is one of six common, widespread air pollutants (the others are ozone,
carbon monoxide, nitrogen oxides, sulfur dioxide, and lead) for which EPA has set National
Ambient Air Quality Standards (NAAQS). A NAAQS is an air quality standard, set under the
Clean Air Act, that is designed to protect public health. In 1987, EPA set PM10 NAAQS
(150 |ig/m\ 24-hour average, and 50 |ig/m3, annual average, averaged over 3 years) to protect
against health risks associated with inhalable particles (mainly those <10 |im diameter) that can
deposit in lower (thoracic) portions of the human respiratory tract. These health-related PM10
particles include both fine particles <2.5 |im diameter (PM2 5) and a subset of coarse particles
larger than 2.5 |im but less than <10 |im diameter (PM10_25). After reviewing the scientific bases
for PM NAAQS in 1996, EPA concluded that fine and coarse components of PM10 particles
should be treated as separate classes of pollutants. Thus, EPA moved in 1997 to set an annual
PM2 5 NAAQS (15 |ig/m3, annual average, averaged over 3 years) to protect against both short-
and long-term exposures and a supplemental 24-hour average PM2 5 NAAQS (set at 65 |ig/m3) to
protect against unusually high peak levels to decrease health risks associated with fine particle
exposures. The PM10 NAAQS were retained to address risks related to coarse particles. As
more scientific evidence becomes available, consideration may be given to setting PM standards
for shorter averaging periods (< 24 hr).
Also, to provide real-time, day-to-day information to State and local health officials and
the public, EPA established an Air Quality Index (AQI) level of concern (LOC) for daily PM2 5
ambient concentrations at 40 |ig/m3. The AQI is meant to provide reference points forjudging
levels of potential health concern and to guide actions by citizens or government officials to
protect the health of the public, including susceptible groups. Thus, in order to minimize risk of
potential health effects among highly susceptible individuals (e..g, the elderly over 65 yr old or
individuals with preexisting chronic cardiovascular or respiratory disease), actions should be
taken to reduce or avoid exposures of such persons to 24-hour PM2 5 concentrations above 40
|ig/m3.
IV.a.l. Air Quality Monitoring of Ambient Particulate Matter Mass/Composition
At the time of the September 11, 2001, WTC attack, there were no monitoring sites
measuring ambient air PM2 5 or PM10 concentrations in the immediate vicinity of the WTC or
surrounding neighborhoods in lower Manhattan, except for PM instruments operating at the
Canal Street Post Office about a half mile north of the WTC. However, there were numerous
New York State-operated PM sampling sites monitoring ambient air PM concentrations at
various other locations throughout the five boroughs of New York City (NYC), with most
measuring PM2 5 levels by Tapered Element Oscillating Microbalance (TEOM) monitors.
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During the days following the September 11 events, substantial efforts were made to
quickly augment existing PM monitoring capabilities by the addition of PM sampling sites
immediately around the WTC Ground Zero work zone and in surrounding lower Manhattan
neighborhoods. Of particular note, staff from EPA's National Exposure Research Laboratory
(NERL) worked with EPA Region 2 colleagues to set up PM samplers at three surface sites
triangulating the WTC Ground Zero work zone perimeter, as shown in Figure 2 (lettered sites A,
C, and K). Site A was located at Barclay and W. Broadway just north of Ground Zero, Site C at
Liberty and Trinity to the southeast of Ground Zero, and Site K at Albany and West to the
southwest of Ground Zero. In addition to these surface sites, ORD PM sampling was initiated at
the 16th floor level in EPA Region 2 facilities in the Federal Building at 290 Broadway about
six or seven blocks northeast of the WTC. These sites are noted in Table 1 of Appendix B, as
EPA Response Team Lettered Sites at Locations A, C, and K and Site #16 under EPA/ORD
Numbered Air Monitoring Stations. By October 2, the U.S. EPA Region 2 and EPA OAQPS,
along with New York State Department of Environmental Conservation (NYSDEC) personnel,
set up PM instruments at Chambers Street, Park Row, and the Coast Guard Building at the
Battery, which along with the existing monitors at Canal St., surrounded Ground Zero a few
blocks farther out than the ORD sites.
Measurements of ambient air PM2 5 elemental composition were made by ORD staff
(Vette et al., 2002) at the three ORD surface sites (A, C, and K), using saturation samplers (SS),
and on the 16th floor of the 290 Broadway Federal Building, using a modified dichotomous
versatile air pollutant sampler (VAPS). The VAPS also collected PM10_2 5 samples. Only the
battery-powered saturation samplers could be operated within the WTC perimeter because power
outages precluded operation of conventional samplers, such as EPA Federal Reference Method
(FRM) samplers in use at preexisting NY State-operated PM monitoring sites. Although the SS
has been shown (Hill, et al., 1999; also see http://www.airmetrics.eom/products/studies/l.html)
to achieve accuracy within 6-10% compared to PM2 5 FRM measurements at concentrations
typically found in ambient air, uncertainty in measured PM2 5 concentrations increase as ambient
concentrations increase, especially above 100 |ig/m3 (24-h average). Indeed, even the FRM is
subject to increasing uncertainties at high PM2 5 levels. However, the general characterization of
air quality used for EPA's Air Quality Index (AQI) should be largely unaffected. The use of
these samplers (SS) allowed for x-ray flourescent (XRF) analyses of the elemental composition
of aerosol samplers. Such XRF analyses were performed on filters collected from September 21,
2001, to January 31, 2002. These samples were collected on an almost daily basis for sampling
periods of about 22 hours per day. In addition to the VAPS sampler, high time-resolution
measurements of light scattering by particles (which is related approximately to the
concentration of fine PM) and light extinction (which is related to the concentrations of black
carbon and to complex organic compounds such as PAHs) were also made. The main focus of
discussion here with regard to EPA/ORD results is on findings from filter-derived PM mass and
elemental composition measurements.
The ORD PM monitoring sites triangulating the WTC Ground Zero perimeter were
placed so as to allow: (a) continuous tracking of PM2 5 emissions from Ground Zero, useful for
detecting any extraordinarily high-level PM2 5 exposures to rescue/recovery workers and others
operating within or immediately around Ground Zero; and (b) the determination of the
physical/chemical composition of WTC-generated PM emissions from the smoldering fires or
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recovery operations, which could serve as a "WTC signature" for tracking the movement of the
WTC plume and its potential impacts on ground-level air quality in the NYC area. Along with
the addition of several more New York State-operated PM sampling sites in lower Manhattan
and elsewhere as part of an extended air monitoring network set up by NYSDEC, the ORD
290 Broadway site helped to ensure reasonably good coverage (within feasibility constraints) of
lower Manhattan neighborhoods surrounding the WTC Ground Zero work zone. In addition to
the ORD monitoring sites (A, C, K, and 290 Broadway), Figure 2 shows the location of New
York State-operated PM25 and PM10 sampling sites.
This expanded monitoring coverage greatly enhanced federal/state government
capabilities for tracking trajectories of WTC-generated plumes, areas potentially affected by the
plumes, and possible WTC-related PM exposures in the NYC area. For example, notable PM
increases at ORD Site A (on the WTC Ground Zero north perimeter), coupled with PM
elevations at the NYSDEC site at Chambers St. and West St. about 5 blocks north of the WTC
(labeled BMCC for Borough of Manhattan Community College in Figure 2) and/or at the Canal
St. Post Office would be indicative of a northerly trajectory of the WTC plume and potential
surface-level exposures of population groups in the vicinity of those monitoring sites and
intermediate locations. Alternatively, marked increases PM levels at Site A, coupled with PM
elevations at 290 Broadway and/or PS 64 (~ 2.5 km northeast of the WTC), would be consistent
with a northeasterly WTC plume trajectory. Also, any increases in PM levels at Site C, coupled
with elevations at Park Row and/or preexisting PM sites at PS 199, the Maspeth Library in
Queens, or PS 274 in Brooklyn would be consistent with an easterly WTC plume trajectory;
whereas PM increases at ORD Sites C or K, along with PM elevations at Battery Park, would
indicate a southerly plume movement. PM increases at multiple ORD sites proximal to the WTC
perimeter and in several neighborhoods in various directions from the WTC could also
conceivably occur under meteorological conditions involving low wind speeds and thermal
stability conditions, producing low mixing layer heights and a more well-defined WTC plume
traversing across lower Manhattan or other NYC areas. On the other hand, if PM concentrations
at other sites across lower Manhattan or other areas in NYC tend to vary with each other (i.e., go
up and down together) and are similar in values, this would imply that they are responding more
to urban or regional background sources rather than to emissions from the WTC sites.
To aid in assessing the potential effects of WTC-related air pollutants on air quality in
NYC areas, ORD has also embarked on the modeling of the dispersal of WTC Ground Zero-
generated plumes, based on prevailing meteorological conditions (e.g., wind speed and
direction). This includes: (a) initially, classical Gaussian plume modeling, providing regional-
scale hour-by-hour plots that roughly delineate the likely spread and direction of the WTC
plume, and (b) more recent initiation of detailed local-scale computational fluid dynamic
modeling which is expected to provide improved, detailed estimation of the dispersal of
emissions from Ground Zero in the street canyons of lower Manhattan. Some preliminary results
of the regional-scale plume modeling are discussed below and compared with PM monitoring
results for certain days of particular interest. It is important to note that the preliminary results
of the regional-scale modeling primarily allow the estimation of the likely direction and width of
the WTC plume at particular times, but they do not alone enable one to conclude if or where the
plume may have touched down and resulted in surface-level increases in pollutant levels. They
alone also do not allow one to conclude what the PM concentrations would have been, only what
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the estimated dilution would have been relative to WTC Ground Zero concentrations. During
periods when emissions from Ground Zero were low, any increases in concentrations within the
plume would also be low. Other inputs (e.g., evaluation of surface-level PM measurements at
various sites and/or photos of the WTC plume) are also needed to aid in characterizing likely
occurrences of plumes affecting the surface and/or possible human exposures.
In addition to the above expanded EPA and New York State government PM monitoring
and modeling efforts, numerous other investigators (e.g., some from other Federal government
agencies, academia, and commercial firms or sponsored by nongovernmental organizations)
collected data aimed at in estimating likely PM exposures associated with the WTC attack and
ensuing fires and recovery operations. Limited published reports from such studies are
becoming available, and a few salient points from these reports are alluded to here. More
thorough discussion of these and other reports that become available in the coming months will
be included in any subsequent, fuller EPA/ORD evaluation.
One important set of newly available findings are those reported by Lioy et al. (2002),
based on work done cooperatively with EPA/ORD and also partly funded by NIEHS. Direct air
measurements of the composition of WTC-generated airborne particles by EPA/ORD did not
begin until September 21, 2001. Before that date, only bulk samples of settled dust were
available for chemical analyses. Lioy et al. (2002) measured the mass of particles in several size
ranges in the settled dust and analyzed their composition. Also, detailed chemical analyses of
fine fraction particles (< 2.5 |im diameter) from settled WTC dust has recently been reported
(McGee et al., 2002). Although the bulk samples do not provide direct data on ambient air PM
concentrations, they do provide strong clues as to the likely composition of airborne PM in lower
Manhattan and the size distribution of particles in the suspended dust immediately after the
collapse of WTC buildings. Small amounts of WTC-derived settled dust were also provided by
New York University investigators for laboratory toxicity testing by EPA scientists (EPA,
2002c; Gavett et al., 2002) in EPA/ORD's National Health and Environmental Effects Research
Laboratory (NHEERL).
Also, in a cooperative U.S. Department of Energy (DOE)/University of California study,
measurements of the size distribution of particles in 10 channels from 0.09 to 12 |im were made
on the roof of the Federal Building on Varick Street, using the rotating drum impactor developed
at the University of California, Davis (Cahill et al., 2002). This Varick Street DOE site is about
2.0 km north of the WTC (see Figure 2). Sampling began October 2, 2001 and continued into
December 2001. Elemental analyses of samples collected approximately every 3 hours were
done by synchrotron radiation-induced X-ray emission (SRIXE).
IV.a.2. Particulate Matter Air Monitoring/Modeling Results
1. Particulate Matter Mass Measurements and Plume Trajectory Plots
The collapse of the WTC buildings and the associated fires resulted in the initial
dispersion of large quantities of various-size particles in the massive dust/smoke cloud that
enveloped lower Manhattan. It is clear from Figures 3 and 4 (and other photographs) that the
densest portion of the dust/smoke cloud initially spread in all directions and impacted most of
lower Manhattan, especially below Chambers Street. On the basis of the size classifications (by
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gravimetric and aerodynamic methods) of particles settled in dust collected September 16-17 at
weather-protected sites just east of the WTC, Lioy et al. (2002) reported the largest mass
concentrations in the settled dust to be due mostly to particles > 53 |im diameter (~ 51-64% of
total mass) and 10-53 |im (~ 35-45% of total mass), followed by lesser percentages for
2.5-10 |im (0.3-0.4%) of total mass), and < 2.5 |im (~ 0.9-1.3%) of total mass) particles. Given
the tendency of large coarse particles to settle out of the atmosphere closer to their emission
source(s) than smaller fine particles, it is likely that higher percentages of small coarse particles
(> 2.5 but < 10 |im) and fine particles (< 2.5 |im) were more widely dispersed in the plume of
dust and smoke that spread primarily to the southeast over Brooklyn and to the south over New
York Harbor during the first 18 to 24 hours after the collapse of the WTC buildings on
September 11.
Figure 5 shows the results of initial plume dispersion modeling for September 11. The
predominant wind direction was to the south-southeast; and this direction continued well into the
next day (September 12). As seen in Figure 5, the predominant direction of the modeled WTC
plume flow is to the southeast, based on wind directions and speeds indicated by black arrows in
this figure. This is consistent with photo images, such as the one shown in Figure 6.
Although no direct measurements of PM concentrations are available for nearby lower
Manhattan areas during the collapse of the WTC, some rough estimates can nevertheless be
made of what concentrations may have been reached. The dust cloud was optically dense, as can
be seen from the airborne images. Under such conditions, sunlight does not reach the surface,
and visibilities are greatly restricted. Conditions such as these have been encountered in dust
storms and in the London smog episodes of 1952 and 1962 (Elsom, 1992). During such
conditions, PM concentrations could have been several milligrams per cubic meter (mg/m3), i.e.,
thousands of micrograms per cubic meter (|ig/m3).
Particles smaller than 2.5 micrometers (fine particles) limit visibility much more
effectively than larger (coarse) particles and under conditions usually found in the eastern United
States, ambient air concentrations of fine particles are typically higher than those of coarse
particles. As a result, under these conditions, visibility reductions are caused mainly by fine
particles. There are a number of simple formulas that relate visibility to the concentration of
PM2 5, such as one from Stevens, et al. (1984):
0.5 (km- mg/m3) = Vis (km)* C (mg/m3)	(1)
where V is the visibility range (km) and C is the concentration of PM2 5 (mg/m3). During the
collapse of the WTC towers, visibilities were reduced to less than 100 m (about 1 city block) on
many streets. If we assume that visibility on streets in lower Manhattan affected by the dust
cloud (see Figure 3) was controlled by fine particles, then application of the above formula
indicates that PM2 5 concentrations could have been about 5 mg/m3 (5,000 |ig/m3). However, the
collapse of the World Trade Center towers mainly produced coarse particles (Lioy et al., 2002),
that, as mentioned above, are less effective than fine particles in controlling visibility. Thus, the
values given above represent lower limits on the abundance of total PM. It should also be noted
that the above estimate of visibility is based on the loss of contrast between light and dark
objects. In many streets, sunlight was blocked and, hence, total PM concentrations could have
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been much higher than the lower limit given above, perhaps even approaching concentrations of
condensed water vapor that are observed in dense fogs (i.e., thousands of |ig/m3).
Thus, individuals engulfed in the initial dust/smoke cloud may have been exposed for
several hours to concentrations of both fine and coarse inhalable particles anywhere in the range
from milligrams per cubic meter (> 1,000 |ig/m3) to perhaps hundreds of milligrams per cubic
meter (> 100,000 |ig/m3). However, it does not appear that people outside the lower Manhattan
area (except possibly very briefly for those on Governor's Island or in Brooklyn Heights)
experienced such extreme PM exposures. This estimation is based, for example, on hourly PM2 5
levels observed at several NYSDEC monitoring sites (Figure 7) during September 11 to 13.
Of most note, as seen in Figure 7, PM2 5 concentrations at NYC sites generally remained
under 25 |ig/m3 during most of September 11 and 12. However, hourly PM2 5 concentrations did
increase to the 50-100 |ig/m3 range for a few hours on September 12 and 13 at PS 64, which is
located about 2.5 km northeast of Ground Zero, and at PS 199, which is located in Queens
several miles east-northeast of Ground Zero. These PM2 5 increases most likely reflected east-
northeast dispersal of not only windblown fine PM from settled dust but also probably of newly
formed fine PM generated by the intense fires (> 1000 °F) at WTC Ground Zero. This would be
consistent with dispersal to the east-northeast of the WTC plume, as indicated by the ORD
modeled trajectory plotted for September 13 (shown in Figure 8). The increased hourly PM25
levels at PS 64 and PS 199 (reaching 166 and 100 |ig/m3 at 9 a.m. September 13) indicate that
the WTC plume likely briefly fumigated the surface for a few hours at those and/or intervening
locations during the morning of September 13.
Changes in wind direction later in the day on September 13 resulted in rotation of the
WTC plume back to a flow predominantly to the south-southwest (mainly over New York
Harbor) through September 14 and 15, as indicated in Figures 9 and 10. Note the very low PM2 5
hourly values (almost all < 6 |ig/m3) at NYSDEC monitoring sites throughout the NYC area
following rain associated with a frontal passage and, also, likely reflecting in part decreased
vehicular traffic in the aftermath of September 11 events.
During the next several days, ORD plume dispersion modeling indicates that the plume
rotated in such a manner as to result in transport in varying directions, including sometimes to
the north-northwest (over northern New Jersey and NYC areas), but there was little indication of
the plume fumigating the surface, based on surface PM measurements at preexisting PM
monitoring sites. During the rest of September and on into October, 24-hour PM2 5 values at
preexisting NYSDEC monitoring sites did not exceed the daily PM2 5 NAAQS (65 |ig/m3, 24-h).
In fact, daily PM2 5 values from most pre-existing fixed sites throughout the NYC area did not
show marked elevations in comparison to historical PM2 5 levels for NYC areas, with the
occurrence through mid- to late October (from time to time or from site to site) of a few 24-hour
PM2 5 values approaching the 24-hour AQI LOC (40 |ig/m3) not being notably out of line with
past frequency of such excursions in NYC.
Starting September 21, the EPA/ORD WTC perimeter monitoring sites at Sites A, C, and
K (within 100-200 meters of Ground Zero) allowed tracking of WTC-related ambient PM
emissions in the immediate WTC vicinity. The ORD monitoring data, shown in Figure 11 (top)
showed widely varying PM concentrations across the WTC perimeter sites from day to day, with
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high hourly or daily PM2 5 levels being seen at one or another perimeter site downwind from
Ground Zero on given days. As seen in Figure 11, exceedances of the 24-hour PM25 NAAQS
level (65 |ig/m3) occurred at some Ground Zero perimeter sites during late September and into
October, but on only a few occasions thereafter. A general downward trend in daily PM
concentrations, as well as a decreasing range of 24-hour variations, were seen for PM2 5
concentrations at these WTC perimeter sites from early October, 2001, onward. The range of
24-hour values among these ORD sites generally remained below the AQILOC of 40 |ig/m3
during December, 2001, and January, 2002 (as depicted by black bar in lower right of Figure 11
top panel). In contrast to the results seen for the ORD/WTC perimeter sites, distinctly lower
PM2 5 concentrations were observed at the 290 Broadway site about six blocks northeast of
Ground Zero. The 24-h PM2 5 concentrations recorded there by VAPS sampling exceeded
65 |ig/m3 (daily PM2 5 NAAQS level) only once, on October 4; and the 24-h AQI LOC (40
|ig/m3) for highly susceptible persons was approached or exceeded at the 290 Broadway site on
only a few occasions (e.g., Sept. 27; Oct. 3, 4, 5; Oct 20; Nov. 15-16). These daily values often
reflect high hourly values occurring overnight mainly during early morning hours before 7 or 8
a.m. The overall pattern of results from ORD perimeter monitoring stations near the WTC,
coupled with distinctly lower PM2 5 concentrations monitored by ORD on the 16th floor at
290 Broadway (about 6 blocks northeast of the WTC) suggest occasional short-term increments
in fine PM values at WTC Ground Zero and, at times, along the WTC fire plume path (with areas
impacted shifting with prevailing winds).
For example, when low wind speeds and mixing layers associated with a high pressure
system over New York City area occurred during October 3-5, generally increased region-wide
PM2 5 levels were observed across much of northern New Jersey and New York City, with some
additional PM increments being superimposed at a few monitoring sites within modeled WTC
plume dispersion areas. During such weather conditions, plumes tend to be more well-defined
than if there were turbulence and are more identifiable for longer distances (see Stull 2000, for
example). In particular, 24-hour PM2 5 at WTC Site A (on north perimeter of Ground Zero)
reached 400 |ig/m3 on October 3-4, but 24-hour PM2 5 values dropped off to 90 |ig/m3 at the
290 Broadway site several blocks northeast of WTC and to 53 |ig/m3 at PS 64 about 1.5 km
further to the northeast of WTC Ground Zero and only reached 60 |ig/m3 at Site K (on southwest
perimeter of Ground Zero). This was consistent with prevailing winds (to the northeast) and the
modeled plume dispersion depicted in Figure 12 for October 4.
Daily average PM2 5 data obtained at additional sites in lower Manhattan (Chambers St.,
Park Row, and the U.S. Coast Guard Station at Battery Park) are shown in the lower half of
Figure 11. These sites are located from 3 to 10 blocks to the north, east, and south from the
WTC (see Figure 2). It can readily be seen in Figure 11 that concentrations of PM2 5 were much
lower than found at the WTC perimeter, indicating a very rapid decline with distance from
Ground Zero. PM2 5 concentrations at these three sites can also be seen to go up and down
together. Correlation coefficients between pairs of these sites are all > 0.9; and the
concentrations are all very similar, suggesting that these sites were responding mainly to
variations in urban and regional background sources rather than to WTC emissions. None of the
daily PM2 5 values exceeded the 65 |ig/m3 PM2 5 24-hr NAAQS. Only a few daily PM2 5 values,
as seen in Figure 11 and listed in the WTC Environmental Data Trend Report (EPA, 2002a) for
the NYSDEC lower Manhattan sites to the north, east, and south of the WTC even approached
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the 40 |ig/m3 AQILOC value; many of the 24-hour PM2 5 levels for such sites were below 20
|ig/m3, PM10 values (not graphically depicted here) observed at the same NYSDEC lower
Manhattan locations around the WTC were also consistently below the daily PM2 5 NAAQS
(150 |ig/m3, 24-h) and showed a general decreasing trend from October 1 to November 30 and
beyond, with 24-hour values decreasing from ~ 50-90 |ig/m3 at some sites in early October to
generally less than 50 |ig/m3 in November (except for ~114-135 |ig/m3 on October 25-26 for
Park Row and 55-75 |ig/m3 on November 15-16, 2001 for all the sites).
Overall, then, the PM2 5 data appear to support the following conclusions:
(1)	Notable PM2 5 elevations occurred in the immediate vicinity of the World Trade Center
Ground Zero during late September/early October, with concentrations at ORD WTC perimeter
sites on some days exceeding the 24-hr PM2 5 NAAQS. However, PM concentrations at the
WTC perimeter sites fell to typical background levels by late November/early December, 2001.
(2)	Such high PM2 5 elevations were not observed at other lower Manhattan monitoring sites
within 3 to 10 blocks of WTC Ground Zero. On only a few sporadic occasions did daily PM2 5
concentrations approach or exceed the AQI LOC (40 |ig/m3) at one or two sites (e.g.,
290 Broadway or PS 64) along the WTC plume path in addition to elevations seen at WTC
perimeter sites. The frequency of such excursions were not out of line with historical frequency
of PM2 5 values approaching or exceeding 40 |ig/m3 either before the Sept. 11 WTC attack or
since the WTC fires ended. See Figure 13, for example, where post September 11 PM2 5 24-h
values for PS 64 are compared to historic levels seen at PS 64 during the previous two years.
(3)	No notable elevations in PM2 5 concentrations were seen at NYSDEC lower Manhattan sites
located 3-10 blocks to the north, east, and south from the WTC, with no PM2 5 values exceeding
either the PM2 5 daily NAAQS or the AQI LOC from the start-up of PM monitoring on October 1
onward.
2. Measurements of Particle Composition
Analyses of bulk samples of dust produced by the collapse of the WTC towers were
performed by EOHSI at Rutgers University (Lioy et al., 2002). Two bulk dust samples were
collected on September 16 and another on September 17. The samples were collected at
weather-protected sites located less than 1 km to the east of the WTC. The particle samples were
separated according to size by aerodynamic and gravimetric methods. As noted earlier, results
of the aerodynamically separated samples indicate that only a very small fraction (about 1%) of
PM was in the PM2 5 size range and less than 0.5% was in the PM10_2 5 size range. The
overwhelming fraction of the mass of PM was found in settled dust particles larger than 10 |im.
Most of the mass consisted of pulverized building and construction materials such as cement and
glass fibers and office building materials such as cellulose. High concentrations of inorganic
constituents such as silica, calcium, and sulfate components of building material and metals
such as lead and zinc, were found. Also, total polycyclic aromatic hydrocarbons (PAHs), which
are products of incomplete combustion, constituted more than 0.1% of the total mass of dust.
The fraction of adsorbed PAHs in each size fraction is expected to be roughly related to the
relative surface area in each size fraction. According to this criterion, smaller particles would
have contained proportionately greater concentrations of PAHs than indicated by their relative
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mass.
Lioy et al. (2002) provides complete descriptions of numerous other specific compounds
that were found in dust particles that settled outdoors. They also noted that penetration of
substantial quantities of WTC-derived dust into indoor office or residential spaces likely notably
increased the potential for indoor exposures (via ingestion or by inhalation of re-entrained
particles) to high levels of constituent elements and compounds.
More detailed chemical analyses have been performed on aerodynamically size-separated
PM2 5 derived from bulk dust samples collected on September 12 and 13 from several locations
withing 0.5 miles of Ground Zero (EPA, 2002c; McGee et al., 2002). These analyses showed
that calcium sulfate (gypsum) and calcium carbonate (calcite) were major components of the fine
fraction, indicating that very finely crushed building materials were still dominant components
even in this size range. Fine particles more easily penetrate into offices and residential spaces
and thereby contribute to indoor exposures more readily than coarse particles.
Data for EPA/ORD measurements of PM elemental composition of fine particles (PM2 5)
for samples collected starting September 21 are graphically depicted in Figures 14 to 18. The
elements are grouped in each figure roughly according to their relative abundance in the subject
air samples, those in Figures 14 to 16 being among the most abundant and those in Figures 17 to
18 being distinctly less abundant. Most of the elements shown in the figures were well
correlated (r > 0.85) with each other at individual sites, with several being much more highly
correlated (r > 0.95) with each other and with PM2 5 throughout the sampling campaign. The
very high correlations suggest a common source origin for these elements, that is, WTC fires.
The composition of the emissions from Ground Zero combustion sources changed with time as
evidenced by initial peaks in several elements (e.g., calcium, potassium, sulfur, chlorine,
bromine, lead, copper, and zinc) during late September and early October (Figures 14 to 16),
followed by later peaks in the concentration of chromium, arsenic and antimony during mid- or
late November (Figures 17 and 18). The elements for which data are depicted in Figures 14 to
18 were selected for illustration from a larger set measured by ORD, based on evident elevations
of their concentrations over typical background levels at some point during the sampling
campaign.
Consistent with Lioy et al.'s finding of highly enriched calcium in both fine and coarse
fractions of settled dust near the WTC, markedly increased levels of calcium continued to be
seen in airborne fine particles (Figure 14) at ORD's Ground Zero perimeter sites off and on
throughout September and October and much of November, decreasing to low background levels
by late November. Elevated levels of calcium in the fine fraction are indicative of highly
pulverized building materials (e.g., wallboard) from the WTC site. However, except for a few
occasions (e.g., on October 6), airborne fine PM calcium levels were not markedly elevated
above background levels at the EPA 290 Broadway site a few blocks northeast of Ground Zero,
whereas calcium in the PM10_2 5 coarse fraction (not graphically depicted here) did show rather
frequent elevations at the 290 Broadway site but decreased to low background levels by the end
of November.
Fine PM silicon elevations were only evident briefly during October 3-5 at Location A
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and at the 290 Broadway site, in contrast with coarse (PM10_2 5) silicon elevations (generally in
the 1000-3000 ng/m3 range) seen at 290 Broadway on a number of days well into late November.
The coarse fraction calcium and silicon enrichments most likely reflect (a) windblown
re-entrainment of calcium and silicon-contaminated dust remaining on rooftops or window
ledges, for example, after hazardous material cleanup of WTC-derived dust in lower Manhattan
during the two weeks after September 11, and/or (b) calcium and silicon particle re-entrainment
into ambient air associated with WTC recovery operations and transport of debris away from
Ground Zero.
Data for concentrations of elemental carbon and total organic compounds in the aerosol
phase based on analyses of paired filter samples are not yet available. However, ORD
nephelometer results and the results of analyses of bulk dust composition mentioned below
suggest that the WTC emissions contained substantial quantities of carbon produced by
incomplete combustion. Surprisingly low total carbon levels (1.5 to 8.5%) were found in
aerodynamically size-separated PM2 5 samples from the bulk dust samples collected on
September 12 and 13 (McGee et al., 2002). These results indicate that crushed building
materials were the dominant sources of fine PM immediately after the collapse of the towers,
whereas combustion from ongoing fires was a relatively more important source of PM25 in later
emissions from the WTC disaster site. Potassium enrichments were also especially notable for
ORD Site A measurements into early October (consistent with combustion of organic materials
such as wooden furniture, paper, etc.); but much lower potassium concentrations occurred at
290 Broadway, and air levels of potassium at all ORD sites returned to very low background
levels by late November.
Elevations of sulfur, chlorine, and bromine (shown in Figure 15) were clearly evident at
ORD Ground Zero perimeter sites and sometimes at 290 Broadway during late September and
decreasingly so into October, again consistent with the notable enrichments seen by Lioy et al. in
WTC dust particles. The sulfur was likely in oxidized form, some perhaps having been
converted from primary emissions of S02 into secondary sulfate particles, consistent again with
both reports of elevated sulfate levels in settled WTC dust particles (Lioy et al., 2002; McGee
et al., 2002) or airborne particles (including very fine fraction particles) collected at the DOE
Varick St. site on October 3 (Cahill et al., 2002). Also consistent with the Lioy et al. findings of
chlorine and bromine enrichments in WTC settled dust are ORD measurements of unusually
elevated chlorine and bromine at Ground Zero perimeter sites. The WTC sources of these
halides are not clear, but chlorine from burning plastics is not unlikely. The specific enrichment
in fine particles of chlorine (versus more typical sodium chloride present as coarse particles) and
no notable sodium enrichment rule out attribution of the chlorine levels simply to airborne sea
salt influxes into the WTC fire site.
As seen in Figures 16-18, lead and certain other metals (copper, zinc, antimony,
palladium, and cadmium) were notably elevated on some days in late September and into early
October at EPA/ORD Site A, as compared with concentrations at Sites C and K, but the
concentrations of these metals had generally decreased to background levels by mid-October.
The late September/early October elevations at Site A on the WTC north perimeter indicate that
the WTC fires were likely a common source of emissions of these metals, because the winds
were mainly from the southwest at this time. The detection of elevated levels of arsenic and
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antimony in mid-November at ORD Site K on the southwest perimeter of Ground Zero (but not
at Sites A or C or at 290 Broadway to the north, northeast, or southeast of the WTC) suggests
both a different source of WTC fire emissions and a likely climatic shift to winds flowing mainly
from the north/northeast to the south/southwest. The chromium elevations seen around
November 20, mainly at Site C, suggest possibly yet another later shift in the composition of
Ground Zero sources of WTC-generated airborne particle emissions. Hence, the "WTC
signature" appears to have varied over time in terms of its specific elemental composition.
In contrast to the above patterns of element levels which indicate that they may have
originated from the WTC fires, the gradually increasing concentrations of nickel up to a range
sustained during December and January (after the WTC fires were out) seem to argue against
any notable airborne fine-particle nickel emissions from the WTC fires subsequent to the
collapse of the WTC buildings on September 11. Still, enrichments in samples of settled dust
from sites east of the WTC (Lioy et al., 2002) are likely indicative of nickel having been among
the metals present in high concentrations of airborne particles in the initial dust/smoke that
enveloped lower Manhattan on September 11. This raises the possibility of (a) any remaining
nickel-containing dust being re-entrained into outdoor air during later rescue/recovery operations
and/or (b) continued elevations of nickel concentrations in WTC-derived indoor dust and
re-entrained indoor air particles.
3. High Temporal Resolution Analyses
The ORD PM2 5 and associated element measurements discussed above were obtained
over sampling periods of close to 24 hours. Examination of additional data is necessary to
determine more precisely the duration and nature of enhanced concentrations of PM constituents
and to help understand possible public health impacts of such excursions. For example, of much
interest are PM elemental composition data for the period October 3-5, when a high pressure
system settled over New York during the early morning hours of October 3 and 4.
Concentrations of sulfur were close to six times higher at the downwind ORD WTC site (Site A)
than at the upwind site (Site K) on October 4. Concentrations of a number of other elements
were also much higher by large enrichment factors at Site A as compared to Site K, as indicated
by the enrichment factors (noted in parentheses) for the following elements: silicon (4IX),
chlorine (500X), potassium (47X), calcium (5X), bromine (350X), copper (130X), zinc (110X),
palladium (> 100X), cadmium (>100X), antimony (>100X), and lead (66X). Overall, the above
results are most consistent with brief, episodic increases from WTC Ground Zero during early
morning hours on October 3 and 4 leading to elevated concentrations of PM and its constituent
elements at WTC perimeter sites and one or another sites in lower Manhattan located downwind
of the WTC on those days (i.e., to the north and/or northeast). These enhanced concentrations
were superimposed on generally higher concentrations of PM and its constituents found upwind
of the WTC on those days. The higher concentrations found at the upwind sites were associated
with a high pressure system that settled over the New York Metropolitan Area during that
period. In any case, the results suggest strongly that the WTC site was the dominant source of
these elements on October 3-4.
University of California, Davis measurements (Cahill et al., 2002) on the roof of the DOE
building indicate a sharp increase in concentrations of PM2 5, mainly in the size range between
0.34 to 0.56 |im on the morning of October 3, as shown in Figure 19. This very brief excursion
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only lasted a few hours. Concentrations of sulfur and silicon at this time were notably elevated
at the DOE site as compared to days immediately before and after. Also, ORD data collected by
both the nephelometer and the aetholometer sited on the Federal Building at 290 Broadway
indicated substantial elevations of PM and light-absorbing components within the space of a few
hours early in the morning of October 4. Hourly PM2 5 levels at PS 64 were also elevated (some
in excess of 100 |ig/m3) during or shortly after the same hours on October 4, suggesting brief
surface fumigation by the WTC plume to the north-northeast of Ground Zero.
It has been suggested that the high concentrations of sulfur observed at the DOE building
on Varick Street were related to transport from power plants either in the Northeast or in the
Ohio Valley. During this early October period, there were most probably some increases in the
concentration of sulfur associated with regional scale transport of sulfates derived from distant
sources. However, the extremely high abundance of sulfur at Site A on the Ground Zero
perimeter observed by ORD and the ratio of sulfur observed at Site A compared with that
observed at Site K suggests that Ground Zero was a large source of sulfur on October 3 and
could have also contributed to sulfur readings at the DOE rooftop site.
The peak elevations of airborne fine PM silicon limited to October 3-4 at Site A and at
290 Broadway are notable, suggesting high temperature volatilization of silicon from glass
and/or cement by intense WTC fires on those dates and transport of the WTC plume in a north to
northeasterly direction. This is consistent both with the plume trajectory plotted in Figure 12
and the marked increases in silicon levels reported by Cahill et al. (2002) at the DOE Varick
Street site, to the north-northeast of the WTC, including unusual measured elevations of silicon
in very fine (0.09-0.50 |im) and, possibly, inferred ultrafine (< 0.01 |im) PM size ranges (silicon
otherwise typically being mainly associated with coarse fraction particles > 2.5 |im). There were
also marked increases in ORD-observed concentrations of various metals on October 3-4,
reinforcing the conclusion that the DOE Varick Street data for October 3 reflected emissions
from intense Ground Zero fires. The very brief increase in PM2 5 values and high levels of
silicon at the DOE site on October 3 apparently did not occur again at that site, based on
preliminary EPA evaluation of the Cahill et al. raw data provided by DOE (Figure 19).
Interestingly, Lioy et al. (2002) reported lead and other substances as being unusually congealed
together with silicon in particles from the WTC settled dust, likely due to the vaporization of
silicon, lead, and/or other metals by intense heat, followed by their condensation and coagulation
into particles with unusual composition.
The above high-resolution measurements suggest that WTC emissions in late September
and early October varied greatly at times over 24-hour periods and that some of the more notable
emissions probably occurred in discrete events which resulted in air pollutant elevations that
lasted only a few hours (mainly overnight during cooler early morning hours before temperature
increases after sunrise). Such events were likely related to activities of rescue and recovery
operations at the WTC, such as removal of large pieces of debris perhaps resulting in increased
oxygen flow and brief flareups of fires within the WTC rubble pile. Further high temporal
resolution analyses, including more detailed local-scale WTC plume plots, will be needed to
better understand the specific lower Manhattan areas impacted by short-term WTC emission
events and the implications of these sporadic events for potential human exposures and health
impacts.
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October 2002
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IV.a.3. Evaluation of Potential Particulate Matter Human Exposures and
Health Impacts
Because no direct measurements were obtained for airborne particle concentrations present
in the dense dust/smoke cloud that enveloped lower Manhattan for up to about 4 hours after the
collapse of the WTC buildings on September 11, estimates of likely exposures to airborne PM
for individuals caught in the initial dust/smoke cloud can only be deduced from indirect evidence
and are subject to great uncertainty. Nevertheless, several tentative conclusions appear to be
warranted on the basis of available inputs thus far.
First, it is likely that many persons caught outdoors (or some even indoors) in the initial
dust/smoke cloud were exposed for several hours to extremely high levels of airborne particles.
This exposure probably included inhalation of PM concentrations in the milligrams per cubic
meter range, well in excess of 1 to 2 mg/m3 (1000-2000 |ig/m3), for both fine (PM < 2.5 |im
diameter) and coarse (PM > 2.5 |im) inhalable particles. Although there were no measurements
available during this critical time period, an examination of available photographs in
combination with an empirical relationship based on visibility suggests that concentrations could
very easily have been this high and likely were even much higher (e.g., possibly > 5 mg/m3).
Such a finding is also supported by analyses of bulk dust samples conducted by Lioy et al.
(2002).
The coarse inhalable particles (PM > 2.5 |im) likely included substantial quantities of
particles in the PM10_2 5 range, which are capable of reaching lower respiratory tract (thoracic)
regions of the lung, even though such coarse particles made up less than 0.5% of the particles
found in WTC-derived settled dust by Lioy et al. (2002). Individuals who inhaled such high
concentrations of WTC dust particles, even for a few hours, would logically be expected to be at
potential risk for immediate acute respiratory and other symptoms and/or, possibly, more chronic
health impacts associated with lung deposition of notable quantities of constituent PM materials
(e.g., calcium, silicon, potassium, lead, other metals).
Persons exposed to the very high PM levels in the initial dust cloud and who continued to
work at Ground Zero or returned to work there within a few days without wearing adequate
protective respiratory gear might be at especially increased risk for potential acute or chronic
health effects, depending on the extent of any ensuing exposures to high PM levels on or
immediately around the Ground Zero rubble pile. The latter could include additional exposures
to coarse PM constituents (e.g., calcium or silicon) present in re-entrained dust particles from the
initial WTC building collapse and/or exposures to newly formed fine particle constituents (e.g.,
metals), as well as to organic constituents (e.g., PAHs present in both size ranges) emitted from
the WTC fires.
Evaluation of potential health impacts associated with the above types of PM exposures
should be further facilitated by disease registry efforts and retrospective epidemiologic analyses
of physician/emergency department visits and hospital admission records being sponsored by the
Centers for Disease Control (CDC), the Agency for Toxic Substances and Disease Registry
(ATSDR), the National Institute of Environmental Health Sciences (NIEHS), and other federal,
state, and NYC agencies and that are now under way. Recent reports (Prezant et al., 2002)
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October 2002
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indicate that large percentages of firemen caught in the initial WTC dust cloud and others who
worked at Ground Zero during the first 2 to 7 days post September 11 experienced respiratory
(e.g., "WTC cough" and/or bronchial hyperactivity) or other symptoms that still continue to
persist for some individuals several months after cessation of exposures at WTC Ground Zero.
During the week following September 11, the plume from initial high-intensity WTC fires
appears to have been largely convected upwards and dispersed mainly to the south-southeast or
south-southwest without much evident ground level contact, except perhaps for a few hours on
the mornings of September 12 and 13, when it flowed to the east-southeast of the WTC. This
resulted in briefly increased hourly PM2 5 levels at sites in lower Manhattan (166 |ig/m3 at PS 64
on 9/13) and in Queens (100 |ig/m3 at PS 199 on 9/13). Probably few people were exposed
around the PS 64 site, given the restrictions in effect on motor vehicular or pedestrian traffic
below 14th Street until September 14, but some may have been briefly exposed in the vicinity of
the PS 199 site and/or at locations between the two sites. Although it is doubtful that the brief,
several-hour PM2 5 excursion on the morning of September 13 resulted in harmful PM exposures,
retrospective examination of physician and emergency department visits and/or hospital records
in the affected areas may help to verify this.
After September 21, EPA/ORD monitoring indicated initially high levels of WTC-derived
airborne particles (especially at certain Ground Zero perimeter sites) during late September and
early October, but occurrences of PM excursions decreased over time through late October and
into November. The rate of decrease in concentrations was not uniform throughout the
monitoring period; rather, there were episodes of high PM levels spaced between periods of
much lower concentrations. The frequency of the episodes was highest during the first month
following the collapse of the WTC buildings and then declined afterwards. For example, notable
PM emission episodes occurred during the first month of sampling, as shown in Figure 11. PM2 5
concentrations varied over a wide range (sometimes exceeding the relevant AQI40 |ig/m3 action
level) during late September and early October at EPA/ORD WTC perimeter Site A. The
concentrations of a number of elements measured at this site also showed large day-to-day
variability, as shown in Figures 14-18. On a number of days in late September and early
October, concentrations of several elements were many times higher than the more typical
background levels recorded for December-January, after the WTC fires had largely or entirely
burned out.
On the basis of overall air quality results summarized above, it appears that 24-hour PM10
and PM2 5 values throughout most all of the NYC metropolitan area generally remained at or
returned rather quickly to historical background levels and WTC PM emissions posed no
increased health risks beyond those due to usual PM levels for most areas of NYC. On the other
hand, high PM2 5 concentrations recorded on the perimeter of Ground Zero during late September
and early October may imply increased health risks for the most highly exposed individuals (that
is, persons who spent extended periods of time within the WTC Ground Zero work zone without
wearing protective respirators). Specifically, acute exposures to irritating materials present in
either the PM2 5 or coarse particle components of PM10, especially during any high hourly peak
excursions, may have contributed to acute or continuing respiratory symptoms reported by some
workers and/or residents in lower Manhattan areas in the immediate WTC vicinity. It is much
less likely that any markedly increased health risks were posed by ambient air PM exposures
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October 2002
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elsewhere in the lower Manhattan neighborhoods surrounding the WTC, although more thorough
analysis and modeling of potential PM exposures and correlation with health records is needed to
evaluate this issue more fully.
It may be useful to place the above potential airborne PM exposures in perspective by
comparing them to (a) exposures that occurred during some past notable PM air pollution
episodes and (b) more recent historical data recorded for New York City areas. As discussed in
U.S. EPA (1982, 1986a) and Elsom (1992), a number of past severe air pollution episodes
involved extended periods of exposure of urban populations to high concentrations of airborne
PM and associated air pollutants such as S02. In contrast to relatively brief periods (< 8 hours)
of September 11 inhalation exposures on September 11, 2001 to concentrations in the range of,
and maybe in excess of, 1000-2000 |ig/m3 of WTC-derived airborne coarse and fine PM, a
number of past air pollution episodes in U.S. cities (e.g., Donora, PA in 1948; NYC in 1953 and
1962/63) and internationally (e.g., Neuse Valley, Belgium, 1930; London, UK in 1952, 1957,
1963) involved exposures to very high levels of PM that lasted for at least several days.
Probably the most famous such episode occurred in London in December 1952, when millions of
Londoners were exposed to daily PM levels (measured as British Smoke, which included high
percentages of fine particles) of 1000-4000 |ig/m3 (sometimes reaching hourly peaks of
6000 |ig/m3 or more) on 3 to 5 consecutive days in the presence of 1000-4000 |ig/m3 of S02.
In NYC, PM2 5 values recorded on some days at the Ground Zero perimeter and
occasionally elsewhere in lower Manhattan during late September and early October clearly
exceeded the more usual background levels of fine PM seen in NYC since implementation of the
PM NAAQS in the 1970s began to substantially reduce ambient PM concentrations in U.S.
urban areas. For example, some ORD WTC perimeter site 24-hour PM2 5 measurements of more
than 100 |ig/m3 likely exceeded most - but not necessarily all - values recorded at the New York
University Medical Center in an aerosol sampling study conducted in August 1976 (Lippman, et
al. 1979), as per the mean value shown for PM2 0 samples in Table 2. However, the 24-hour
PM2 5 concentrations (predominantly below 30-40 |ig/m3) usually seen during most of the rest of
October and into November at ORD WTC perimeter sites were notably lower than the 1976
values; and the PM2 5 levels reached by December and January generally compare favorably with
PM2 5 values obtained at a monitoring site at the Bronx Botanical Gardens during February-June
2000. This Bronx site can be considered to be a relatively "clean" urban background site largely
free of the effects of strong local sources. Maximum PM25 values ranged from 35.4 to 43.3
|ig/m3 from three inter-compared collocated samplers at that Bronx site and average 24-hour
PM2 5 values ranged from 12.5 to 15.6 |ig/m3, analogous to the mean PM2 5 concentrations shown
in Table 2 for Boston and Philadelphia during February-June, 2000. Also, PM10 values for lower
Manhattan sites, which were mainly in the range of 50-90 |ig/m3 during October and mostly
below 50 |ig/m3 in November, were not markedly different from historical values observed in
NYC. For example, the fourth highest and the maximum 24-hour PM10 values reported in the
EPA Aerometric Information Retrieval System (AIRS) database for the five NYC boroughs
during 1996 to 2001 ranged from 40-89 |ig/m3 and from 51-121 |ig/m3, respectively.
During September-October, 2001, concentrations of many elements, including heavy
metals, at Ground Zero perimeter sites were at times much greater than those observed at several
sites in the Northeast in February-June 2000. As part of a pilot study for EPA's PM2 5 speciation
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October 2002
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network, concentrations of PM25 and a number of key elements were measured from February to
June, 2000, in NYC (at the Bronx Botanical Gardens), Boston, and Philadelphia, at sites that
were likely characteristic of urban backgrounds. As shown in Table 2, the average
concentrations of PM25 and the individual elements measured at the three sites varied relatively
little in contrast to those measured near the WTC site. The highest measurements of PM2 5 and
heavy metals are also shown in Table 2 for comparison. During the first weeks after September
11, PM2 5 levels and concentrations of several elements often were many times higher than those
obtained at the northeastern sites listed in Table 2. As also seen in Table 2, concentrations
recorded at the New York University Medical Center in 1976 (Bernstein and Rahn, 1979) were
higher than those at the other Northeastern sites, but they were still distinctly lower than the
measurements made soon after September 11.
During December and January, the concentrations of most of the elements measured by
ORD decreased to levels similar to those measured at the northeastern sites, suggesting that the
WTC was no longer a significant source of these elements. However, it should be noted that
even the markedly elevated element concentrations over typical background values noted mainly
in September and October did not exceed applicable OSHA PEL (8-hour time-weighted average)
values or other more broadly applicable health benchmark values, suggesting a generally low
health risk for those working at Ground Zero or others present in lower Manhattan
neighborhoods around the WTC.
Alkalinity of the dust from the WTC disaster may have been a possible health concern for
exposed individuals. Some reported symptoms (eye, nose, and throat irritation; nose bleeds;
cough) may have been due to exposure to unusually elevated quantities of certain crustal
materials derived from pulverized concrete, wallboard, and other WTC structural components
present in airborne particles and settled dust in neighborhoods near the WTC. The United States
Geological Survey (USGS, 2002). Lioy et al. (2002), and McGee et al. (2002) all reported
testing aqueous solutions of WTC settled dust and finding an initially high alkalinity (generally
> pH 10.0), which decreased to pH 8-9 for outdoor samples taken after rainfall (as reported by
USGS). Because much of the outdoor settled dust was removed by hazardous material cleanup
procedures or was washed away by rainfall during late September, outdoor exposures to highly
basic PM components would seem to be of much less potential health concern beyond late
September when restricted zone shrinkages allowed more people and traffic in neighborhoods
immediately surrounding the WTC work zone. However, USGS noted higher alkalinity for dusts
sampled indoors, raising the possibility of greater risk of acute irritation symptoms being
associated with indoor exposures to WTC dusts than with outdoor dusts leached by rainfall.
Lioy et al. (2002) more broadly highlighted indoor exposures to WTC-derived dust PM as
posing potential increased health risks. Individuals visiting, residing, or working in buildings
not adequately cleaned before reoccupation could have been subjected to repeated, long-duration
exposure to many of the components from the original WTC collapse found by Lioy et al. in
settled dust to the east of the WTC. Lioy et al. noted that long, narrow glass fibers in the
WTC-derived dust had various potentially toxic materials attached to them and could contribute
to acute short-term irritative effects and possibly to more chronic health risks.
Also of potential concern would be any extended indoor air exposures to finely pulverized
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October 2002
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building materials (e.g., calcium, silicon, iron, and sulfate) in PM particles, to PM of either fine
or coarse size containing marked elevations of certain metals, or to fine PM containing usual
combinations of silicon coagulated with metals or other toxic materials. Lioy et al. directed
notable attention to indoor dust loadings of lead as posing potential chronic health risks. The
possible contributions of certain other metals (e.g., nickel, chromium) found in settled dusts or
airborne PM to irritative symptoms also need further evaluation. The discussions below for lead,
nickel, and chromium contain more information on the possible bases for concern with these
particular metals. The issue of potentially greater toxicity being associated with unusually
increased quantities of very fine or ultrafine particles present in airborne PM also needs to be
evaluated further.
Some newly available findings from the laboratory toxicity studies of WTC-derived dusts
may offer insights into potential health responses associated with exposures on September 11 to
WTC-derived materials in the initial WTC building collapse dust cloud and later exposures to
WTC-particles deposited indoors. ORD NHEERL scientists analyzed chemical and
toxicological properties of PM2 5 derived from the collapsed WTC buildings (EPA, 2002c;
McGee et al., 2002; Gavett et al., 2002). Deposited dust samples were collected from sites
within a half-mile of Ground Zero on September 11 and 12 and size-separated to collect the
PM2 5 fraction. Gavett et al. (2002) evaluated responses of young adult female mice to bolus
doses of WTC-derived PM2 5 dusts administered by intratracheal instillation directly into the
lungs and to 5-hour inhalation exposures to WTC PM2 5. On the basis of the overall pattern of
results obtained, Gavett et al. observed both a small degree of pulmonary inflammation in
response to WTC dust, which was distinctly less compared with exposure to residual oil fly ash
(ROFA), and some notable increases in airway hyperresponsiveness to methacholine, a
nonspecific bronchoconstricting agent, greater than that observed in mice exposed to ROFA or
other PM samples. These effects may be interpreted as being consistent with reports of airway
hyperresponsiveness and irritant responses in people exposed to high concentrations of WTC-
derived dusts. Whereas the mild pulmonary inflammation in mice diminished from 1 to 3 days
after exposure, the airway hyperresponsiveness appeared to persist longer.
These results suggest possible limited, short-term lung inflammation effects from
exposures to high concentrations of WTC dust (as may have occurred mainly on September 11)
or possible long-term airway hyperresponsiveness that might portend more prolonged
sensitivities and irritative symptoms for persons experiencing extended high-level exposures to
WTC-derived dusts indoors. Gavett et al. (2002) estimated the human exposure equivalent of
the doses that led to these responses in mice, and calculated an 8-hour exposure at moderate
activity level to a concentration of 425 |ig/m3 using a multiple-path particle deposition model
(Ferijer et al., 1999). Individuals who are especially sensitive to inhalation of dusts, such as
asthmatics, might experience these effects at lower concentrations over more prolonged periods
of exposure. As mentioned previously, it is likely that persons caught in the initial dust/smoke
cloud could have been exposed to PM2 5 concentrations in excess of 1000 |ig/m3. However, a
dose equivalent to a human exposure of 130 |ig/m3 over 8 hours caused no significant effects in
the mice, suggesting that most healthy people would not be expected to respond to this
moderately high exposure level with any adverse respiratory responses (EPA, 2002c; Gavett et
al., 2002).
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October 2002
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These studies did not address the effects of the coarse fraction of WTC PM on responses in
mice, which may be very important, considering the upper airways responses and ocular irritant
effects that have been reported.
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October 2002
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Table 2. Concentrations (maximum and Sept-Oct average) of PM25 and Component Elements Measured at the EPA/ORD
World Trade Center Perimeter Sites and at Four Other Sites in the Northeast U.S. (PM2 5 concentrations in |ig/m3; all other
components in ng/m3).

WTC Max. (Site, Date)
WTC Average Sept-Oct1
NYU Med. Ctr.2
Bronx, NY3
Boston, MA3
Phila, PA3
A
C
K
Aus '76
Feb-June '00
Feb-June '00
Feb-June '00
PM25
400 (A, 10/4)
85
34
50
81.74
12.5
10.7
14.7
Na
870 (A, 10/4)
273
157
169
570
72
178
63
Mg
490 (K, 11/13)
101
67
79
103
4.8
16
7.7
A1
670 (A, 10/20)
198
74
113
187
9.2
25
18
Si
20000 (A, 10/4)
943
224
333

75
92
118
S
23000 (A, 10/3)
4796
1808
2524
6820
1200
933
1500
CI
45000 (A, 10/4)
7247
540
845
119
9.8
68
7.7
K
5600 (A, 9/22)
988
147
260
194
38
38
60
Ca
4900 (A, 10/11)
1304
345
749

38
50
57
Cr
34 (C, 11/19)
5
4
3
28
0.3
0.5
1.1
Fe
9400 (K, 12/12)
1745
904
975
400
91
76
103
Co
24 (A, 10/3)
4
bdl
bdl
3.2
0.4
0.4

Ni
50 (K, 12/11)
11
9
11
18
12
2.8
4.4
Cu
2800 (A, 9/22)
435
59
92

2.8
2.2
4.5
Zn
10000 (A, 10/4)
1526
164
307
224
21
9.7
16
As
1100 (K, 11/14)
9
bdl
bdl
3
1.1
0.9
1
Br
5700 (A, 9/20)
800
82
124
133
2.5
2.5
3.4
Pd
900 (A, 10/4)
132
2
7




Cd
150 (A, 9/22 & 10/4)
33
9
9
7.7
1.7
1.7
1.8
Sb
350(A, 9/22)
50
2
1
11
3.6
2.4
3.5
Pb
5500 (A, 9/22)
791
83
167
1170
4.2
3.4
5.6
'A time series of PM2 5 measurements for Site A (as well as Sites C, K, and 290 Broadway) can be seen in Figure 11. Time series measurements for the
DRAFT-DO NOT Q UOTE OR CITE	43	October 2002
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elements in PM2 5 from the same sites can be seen in Figures 14-18. Measurements in these tables are the high measurements seen in these figures, and the
dates of the measurements are shown in parenthesis. Nearly all elevated measurements were seen in Site A, and in late September, early October, bdl =
below detection limit and n.a. = data not available. 2NY Summer Aerosol Study, 1976. 3Coutant et al., 2001. 4PM2 0 0.9 * PM2 5 (estimated).
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October 2002
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'¦! - )
'ark Row ¦
rSprucs
iraw
Coant Guarrl
Battery Park
hn jteaattf Fl.
cvEPA EnwroMapper

sSMBfl
Key for ORD
Lettered Sites
A = Barclay and
West Broadway
C = Liberty and
Trinity
K = Albany & West
(as noted on figure)
Figure 2. Particulate matter monitoring sites, including ORD surface sites (A, C, K) on the WTC perimeter, the ORD site at 290
Broadway, and NYSDEC sites located elsewhere..
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October 2002
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Figure 3. Spread of dense dust/smoke cloud over all of lower Manhattan and drifting to the
E/SE immediately after the September 11, 2001, collapse of the World Trade Center buildings.
Figure 4. World Trade Center (WTC) plume from intense fires (>1000 °F) during days
following September 11, 2001, with high concentrations of both newly formed fine particles
from combustion and reentrained coarse particles likely being transported upward by convection
processes and being dispersed in the WTC plume over varying NY City areas, depending on
prevailing wind directions and speeds.
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CALMET Surface Wind Field and CALPUFF Plume Dilution
(ndnfivB to volume sauroe at recovery site)
\ \ #y j\ \ v	v
,aB *Y" ?V
k \ \j \ \ \ y \ \

v v>7v r
rOV/j< C;-
-------
Manhattanville P.O.
.juia ,
Afternoon/
WWlWfl
Bronx
Queens
Maspeth Library
Fresh Kill Met
PS 44
709718
Richmon
Figure 7. Increased hourly PM2 5 concentrations measured on September 12 and/or 13 at PS 64, PS 199, Maspeth Library, and PS
274 to the E/SE of WTC, reflecting dispersal of newly formed fine particles from WTC fires and/or fine particles reentrained from the
settled dust from initial collapse of WTC buildings. (PM2 5 data provided courtesy of NYSDEC).
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October 2002
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CALMET Surface Wind Field and CALPUFF Plums Dilution
(relative to volume source '{' I
•/A'l A' <•
j /v / ; v7 / i w
12:00
pkjme final mpv
Figure 9. ORD-modeled WTC plume dispersion on September 14, 2001 at 12 noon, indicative
of plume flow mainly out over New York Harbor.
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October 2002
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Figure 10. Satellite photograph of WTC plume lofting from GZ at 11:54 a.m. EDT on Sept. 15,
2001, and dispersing to the S/SW out over the New York Harbor. (Source: Mandatory credit:
"spaceimaging. com".)
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October 2002
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a 500
400
E 300
CT)
200
-	Site A
-SiteC
-SiteK
-	290 Broadway
100
NAAQS A * I • U A
\
A. ^ ll..

aoi ¦) * Vffy jfyi
r	-Jrf. :

n
LOC


9/11
9/18 9/25 10/2 10/9 10/16 10/23 10/30 11/6 11/13 11/20
11/27 Average
+ SD
All Sites
12/1 thru 1/31
500
400
D1
=J_
200
100

-~-Chambers St.

—a— Park Row
_
-~-C.G.S. (Battery Row)
ii*.
¦V
3
M

NAAQS

AQI	.
L°C iui^ |

9/11
9/18
9/25
10/2
10/9 10/16 10/23 10/30 11/6 11/13 11/20 11/27 Average
+ SD
All Sites
12/1 thru 1/31
Figure 11. Panel A (top) : Daily PM2 5 concentrations monitored by EPA/ORD at sites A, C, and
K around Ground Zero perimeter and at 290 Broadway 6 blocks northeast of Ground Zero.
Panel B (bottom): PM2 5 concentrations observed at several extended monitoring network sites
in lower Manhattan within 3 to 10 blocks of WTC Ground Zero.
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October 2002
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Hourly ADAS/CALMET Meteorology with CALPUFF Plume Dispersion
04-0ct-2001 03:00
46
U>i'
Figure 12. ORD-modeled WTC plume dispersion on October 4, 2001 at 3:00-4:00 a.m. Note
the general regional elevation of hourly PM2 5 levels (in jig/nr') indicated by red numerals for
monitoring sites scattered across both northern New Jersey and NYC areas, even outside
modeled areas of likely greatest plume intensity indicated by red shading.
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October 2002
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PM2 5 Since September 11
9/13
10/4
7°^
24-Hour
Health-
Based
Level of
Concern
/
Did.


PM2 5 Over 2-Years
§ §
O	TO
CJ Cj
O T-
Q o
8 3
CM *-
<2 9
3 S
Q 9
£J §
Figure 13. Daily PM2 5 concentrations recorded at NYSDEC PS 64 monitoring site after
September 11, 2001 (9/11/01 to 10/27/01) compared to historic record of 24-hr PM2 5 values at
the same site during prior 2 years (2/23/00 to 9/01/01). Note exceedence of 40 |ig/m3 AQI Level
of Concern on September 13 and likely again on October 4; red portion of bar indicates 24-hr
average if three high hourly values (> 100 jig/m3) being evaluated for data quality are included in
24-hr average calculation.
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October 2002
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6,000
5,000
4,000
Site C
SiteK
290 Broadway
3,000
2,000
1,000
9/11 9/18 9/25 10/2 10/9 10/16 10/23 10/30 11/6 11/13 11/20 11/27
Average
Range
All Sites
12/1 thru 1/31
24.000
j? 12.000
C/)
6,000

Site A

Site C

Site K

290 Broadway
	Ifeaaiaiaiai

9/11 9/18 9/25 10/2 10/9 10/16 10/23 1 0/30 11/6 11/13 11/20 11/27
Average
Range
AJI Sites
12/1 thru 1/31
6,000
5,000
4,000
Ul 3,000
c
2,000
1,000
f t
Site A
Site C
SiteK
- 290 Broadway

9/11 9/18 9/25 10/2 10/9 10/16 10/23 10/30 11/6 11/13 11/20 11/27
Average
Range
All S«tes
12/1 thru 1/31
Figure 14. ORD measurement of PM2 5 elemental constituents Ca, Si, and K at Ground Zero
perimeter sites and 290 Broadway site.
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October 2002
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20,000
^ 15.000
o>
c
(/) 10.000
5.000
Site A
-	Site C
-SiteK
-	290 Broadway
t	r \
9/11 9/18 9(25 10/2 10/9 10/16 10/23 10/30 11/6 11/13 11/20 11/27 Average
Range
All Sites
12/1 thru 1/31
40.000
30.000
10.000


Site A


Site C


Site K
1

290 Broadway

'





1 ,
/V

*
t*
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9/11 9/18 9/25 10/2 10/9 10/16 10/23 10/30 11/6 11/13 11/20 11/27
Average
Range
AllSf.es
12/1 thru 1/31
10.000
-	Site A
Site C
Site K
-	290 Broadway
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1
!

9/11 9/18 9/25 10/2 10/9 10/16 10/23 10/30 11/6 11/13 11/20 11/27
Average
Range
All Sites
12/1 thru 1/31
Figure 15. ORD measurements of PM2 5 elemental composition for S, CI, and Br at Ground
Zero perimeter sites and 290 Broadway site.
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6,000
T


Site A
Site C
5,000


Site K
290 Broadway
_ 4.000



I
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A
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1,000
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am 9/18 9/25 10/2 10/9 10/16 10/23 10/30 11/6 11/13 11/20 11/27
Average
Range
Ail Sites
12/1 thru 1/31
3,000
2,400
~	Site A
*	Site C
~	SiteK
•	290 Broadway
1.800
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=j 1.200
600
0
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9/11 9/18 9/25 10/2 10/9 10/16 10/23 10/30 11/6 11/13 11/20 11/27 Avefage
Range
AM Sites
12/1 thru 1/31
12,000
Ui
c
£
N
6.000
3.000


—Site A


Site C
1

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—290 Broadway
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9/11 9/18 9/25 10/2 10/9 10/16 10/23 10/30 11/6 11/13 11/20 11/27
Average
Range
All Sites
12/1 thru 1/31
Figure 16. ORD measurements of PM2 5 elemental constituents Pb, Cu, and Zti at Ground Zero
perimeter sites and 290 Broadway site.
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October 2002
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1,200
1,000
E
O)
cn
<
600
-	Site A
-	Site C
-SiteK
-	290 Broadway
¦aato
9/11 9/18 9/25 10/2 10/9 10/16 10/23 10/30 11/6 11/13 11/20 11/27
Range
All Sites
12/1 thru 1/31
1,200
1,000
800
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c
¦o
Q.
600
400
Site A
•*— Site C
Site K
•- 290 Broadway
9/11 9/18 9/25 10/2 10/9 10/16 10/23 10/30 11/6 11/13 11/20 11/27
300

-Q
CO
-	Site A
-SiteC
-	Site K
-	290 Broadway
9/11 9/18 9/25 10/2 10/9 10/16 10/23 10/30 11/6 11/13 11/20 11/27
Average
Range
Al Sites
12/1 thru 1/31
Figure 17. ORD measurements of PM2 5 elemental constituents As, Pd, and Sb at Ground Zero
perimeter sites and 290 Broadway site.
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Site A
Site C
Site K
290 Broadway
60
U)
c
:= 40
9/11 9/18 9/25 10/2 10/9 10/16 10/23 10/30 11/6 11/13 11/20 11/27
Average
Range
AJlSrtes
12/1 thru 1/31
•o
o
100
50
-	Site A
Site C
Site K
-	290 Broadway
9/11 9/18 9/25 10/2 10/9 10/16 10/23 10/30 11/6 11/13 11/20 11/27
39
36
33
30
27
r*> 0,
£ 24
O) 21
r18
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12
9
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Site A
•	SiteC
•	Site K
290 Broadway
I •	ff	/1 i i /1 faff
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•	•	I j	*	4	• I
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*. * * .. v ' :* t'<; •* r .!:
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9/18 9/25 10/2 10/9 10/16 10/23 10/30 11(6 11/13 11/20 11/27 Averaae
Range
All Sites
12/1 thru 1/31
Figure 18. ORD measurements of PM2 5 elemental constituents Ni, Cd, and Cr at Ground Zero
perimeter sites and 290 Broadway site.
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250
200
U)
=L
150
c
o
2 100
c
o>
o
c
o
o
50
0 ¦
10/1 10/2 10/3 10/4 10/5 10/6 10/7 10/8 10/9 10/10 10/11 10/12 10/13 10/14 10/15
Figure 19. PM2 5 concentrations recorded on rooftop of DOE Facility at Varick St.,
approximately 2.0 miles N/NE of Ground Zero. Note single very high PM2 5 excursion mainly
restricted to morning hours of October 3 (see inset figure for October 3), consistent with ORD
measurements at Location A on the WTC north perimeter and ORD WTC plume plot shown in
Figure 12 for October 3.
12:00 AM 4:00 AM 8:00 AM 12:00 PM 4:00 PM 8:00 PM 12:00 AM
250 n	October 3,2001
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IV.b. Metals
IV.b.l. Lead
Lead, a silver-grayish soft metal with a relatively low melting point, was still widely used
in the 1960s and 1970s (when the WTC was built) in paint and for soldering indoor plumbing
joints and electrical wiring systems. It was also used for soldering of computer circuit boards
and wiring in a variety of electrical appliances. These uses make it likely that lead would be
among the toxic substances of concern at the WTC site. Lead could have been emitted as a
combustion product of the ensuing fires or could have been present in reentrained particles
stirred up into the air in the course of recovery activities and transport of debris away from the
WTC site.
The potential public health concern due to lead exposure most relevant for consideration in
relation to the WTC situation is lead intoxication associated with prolonged low-level lead
exposures. As discussed in EPA (1986b), such exposure can result in subtle, often subclinical,
health effects such as altered calcium metabolism and bone formation/loss, slowed physical
growth, and slowed nervous system development of the fetus. Effects on the fetus may be due to
exposure of the mother during pregnancy, therefore, women of childbearing age have been
identified as an important susceptible population. Other effects of lead intoxication may be
slower postnatal growth and neurobehavorial development, IQ decrements and learning deficits,
and other neuropsychological effects among young infants and children (another susceptible
group).
In 1978, the EPA NAAQS for lead was set at 1.5 |ig/m3 (90-day average). This level was
set to reduce the risk of occurrence of lead intoxication impacts associated with prolonged low-
level exposures of susceptible groups. With the EPA phase-down of lead as an additive in
gasoline during the past several decades and the current widespread use of unleaded gasoline in
the U.S., ambient air lead concentrations have decreased dramatically. Before the start of the
phase-down of lead in gasoline in the late 1970s, air lead levels as high as 2.0 |ig/m3 or more
were often detected in U.S. urban areas such as NYC. Currently, 24-hour ambient air lead levels
below 0.5 |ig/m3 are typical of NYC and other U.S. urban areas. NYSDEC Annual Air Quality
Reports, for example, indicate (a) arithmetic mean annual-average 24-hour airborne lead levels
during 1994 - 1998 of 0.04 to 0.08 |ig/m3 for a Manhattan (Madison Ave.) curbside sampling site
(maximum daily value = 0.34 |ig/m3) and (b) arithmetic mean annual-average values ranging
from 0.02 to 0.09 |ig/m3 for three Brooklyn/Staten Island sites (maximum daily value =
0.63 |ig/m3) during 1992 - 1997.
Before the start of gasoline lead phase-out, lead concentrations in outdoor dust were
reported (in studies assessed in EPA, 1986b) to range from 280 to 1500 |ig/g (ppm) in residential
areas of NYC and Philadelphia and from 900 to 13,000 |ig/g in street dust or near heavily
traveled roadways in several northern U.S. urban areas (NYC; Philadelphia; Washington, DC;
Chicago; Detroit). Despite significant decreases in air lead concentrations, soil and street dust
lead concentrations in excess of 500 - 1000 |ig/g were still observed into the early 1990s in U.S.
urban areas (e.g., Boston, Baltimore, and Cincinnati, as described in EPA, 1996). This may
reflect, in part, the residuum from earlier gasoline lead deposition from air or more current
contamination from deterioration of lead-based paint from residential or other structures or from
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industrial production or waste disposal activities.
The potential for very high short-term lead exposures existed during the initial spread of
the dust/smoke cloud from the initial WTC collapse; and the ensuing fires, recovery operations,
and debris removal may have also posed some lead exposure risks. Examination of air lead data
from ORD WTC perimeter sites (Figure 16) and for additional lower Manhattan sites (Figure 20)
reveals that 24-hour lead concentrations within (e.g., at WTC Building 5 SW) or at the WTC
Ground Zero perimeter (e.g., at Location A, Barclay and W. Broadway; Location B, Church and
Dey) approached or exceeded 1.5 |ig/m3 on several days in late September/early October (e.g.,
September 17, 23, 27 and October 4, 5). There appeared, however, to be rapid fallout
(deposition) of the lead from air close to the WTC rather than the lead being transported over
longer distances. This interpretation is based on the relatively uniform low air lead values
(mostly less than 0.5 |ig/m3) seen at the EPA ORD 290 Broadway monitoring site (Figure 16)
and at several other locations within a few blocks of the WTC (Figure 20). Consistent with the
pattern seen in Figure 16 for EPA/ORD WTC perimeter and 290 Broadway monitoring sites,
lead elevations at other lower Manhattan sites outside the WTC work zone generally returned to
more typical low background concentrations by mid-October. After October 8, none of the air
lead concentrations shown by the WTC Trends Report (EPA, 2002a) for any of the lower
Manhattan monitoring sites outside WTC Ground Zero approached or exceeded 1.5 |ig/m3; in
fact, with very few exceptions, nearly all were below 0.5 |ig/m3. Thus, prolonged lead
concentrations averaged over 90 days during late September to late November, 2001, at WTC
perimeter or other nearby lower Manhattan sites did not exceed the EPA Lead NAAQS (i.e., 1.5
|ig/m \ 90-day average). The overall pattern of data, coupled with restrictions of vehicular or
pedestrian traffic in lower Manhattan areas close to Ground Zero until very late September/early
October, make it doubtful that persons outside the Ground Zero area were exposed sufficiently to
airborne lead levels so as to experience any chronic health risks.
There may, however, exist some basis for potential concern with regard to short-term
(hours, days) highly elevated lead exposures of individuals working within the Ground Zero
perimeter without appropriate respiratory protection. The highest 24-hour lead level shown in
Figure 20 was 5.4 |ig/m3 at WTC Building 5 on September 24. It is likely that comparable or
higher elevations in ambient air may have occurred within Ground Zero on some days preceding
the start of EPA monitoring in late September. This possibility and the above-noted data
showing air lead values approaching or exceeding 1.5 |ig/m3 on certain days during late
September and into October at sites within the WTC work zone or at perimeter sites very close
to Ground Zero (within 100 - 200 m) suggest that flare-ups of Ground Zero fires or lead
emissions associated with recovery and debris removal operations might have posed risks for
individuals within the WTC Ground Zero perimeter. The potential risks would probably be of
most concern for pregnant women or other women of childbearing age if any were working
within Ground Zero without wearing appropriate protective respirators for extended periods
during the first 2 to 4 weeks after September 11. OSHA data (http://osha.gov/nvc-
disaster/map.html) do indicate that high air lead levels were detected on September 22 (69.3
|ig/m3, averaged over 4.5 hr) and September 23 (18.1 |ag/m\ averaged over 3 hr) by area
monitoring near WTC Building 5 well within the Ground Zero work zone. However, none of the
OSHA personal sampling data reported for WTC recovery workers (e..g, ironworker, torch-
cutter/burner) exceeded the OSHA Lead PEL (50 |ig/m3, 8-hr average) during late
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September/mid-October (although some personal sampling results were reported that exceeded
PEL levels on widely-scattered days from late October into early 2002 for the WTC 5 Building
area at Ground Zero). Nor were there any notable blood lead elevations (maximum values < 20
|ig/dl) among more than 300 male fire fighters serving at WTC Ground Zero and sampled by
CDC in October 2001 (personal communication, P. Edelman). These data tend to suggest that,
although it can not be entirely ruled out, it is unlikely that any pregnant or other women of
childbearing age working within the WTC Ground Zero perimeter (e.g., among rescue/recovery
personnel or assisting with dispensing of food, beverages or other aid to such personnel) would
have experienced sufficient lead exposures to be at high risk for lead intoxication effects on them
or any fetuses in-utero during or soon after WTC-related lead exposures.
It should also be noted that limited lead results available for analyses of bulk dust samples
taken at locations close to the WTC did not appear to show any notably high lead concentrations.
The values for bulk dust samples near the WTC noted in the WTC trends report ranged from
120 to 370 |ig/g (ppm) - the latter value for a sample taken at Park Place and West Broadway on
September 16. These values are consistent with lead concentrations found by ORD in bulk dust
near the WTC (median 142 ppm) or those reported by cooperating academic investigators (Lioy
et al., 2002) as ranging from 101 to 625 |ig/g in bulk dust collected several blocks east of the
WTC within days after September 11. They are also not exceptional in comparison with the 500
- 1000 ppm street dust or residential soil lead concentrations often still found in U.S. urban areas
in the 1990s, as earlier stated. However, as Lioy noted, indoor exposures to lead-contaminated
WTC-derived dust that penetrated indoors could continue to pose risks to individuals
re-occupying buildings not cleaned by effective decontamination procedures.
On the basis of results evaluated to date, there is little indication of any substantial health
risks being associated with lead exposures of the general population in lower Manhattan areas
around the WTC site. However, evaluation of blood lead levels and pertinent medical records
for any pregnant women exposed at Ground Zero or in its immediate vicinity during September
or early October could provide useful further data by which to assess any such possible health
risks associated with WTC-generated lead emissions.
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Lead (Pb) Air Monitoring Trends
Inside and Outside WTC Zone
255 Ambient Air 24hr integrated samples from September 2001 to mid-January 2002
6
5.4
5
4
3
2
1
.0.3'
,42
0.28
0
&
s
A

a
C>
—location A
O Location B
	Location C
	Location CI
Location D 	Location E
	Location F
	Location P
	Location R *
Location S
Church A Vesey St A Building 5 5W
"Higher of two (2) sample results, taken per day, is included here.	"Location R has 2 results therefore 255.
Figure 20. Ambient air lead concentrations (|.ig/m3) at sites within Ground Zero or in lower
Manhattan locations in immediate vicinity of the WTC.
Source: EPA Region 2
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IV.b.2. Chromium and Nickel
Chromium and nickel were chosen for evaluation in this assessment because both can be
irritating and sensitizing. Chromium and nickel are used in the production of stainless steel and
other metal alloys. Chromium, in the hexavalent form, Cr+6, can damage the nose and cause
cancer. Similarly, workers who have breathed large amounts of nickel have developed lung and
nasal sinus cancers. Total chromium in urban air typically ranges from 0.01 to 0.03 |ig/m3
(ATSDR, 2000c), and nickel concentrations in urban air range from 0.001 to 0.328 |ig/m3
(AT SDR, 1997b).
To evaluate chromium and nickel, the OSHAPELs (chromium, 1 mg/m3; nickel, 1 mg/m3)
were used as a screening benchmark (NIOSH, 2002). For chromium, the ATSDR intermediate
inhalation MRL for Cr+6 PM (1.0 |ig/m3) was also used (ATSDR, 2000c). For this evaluation, it
was assumed that chromium would be released as solid PM, not as a mist, in order to compare
measurements with the ATSDR MRL, which is specific to PM concentrations.
Data for evaluating chromium and nickel came mostly from the EPA WTC monitoring
database. A total of 21 air samples, collected between September 23 and January 31 at Building
5, were evaluated for chromium and nickel at Ground Zero. None of the samples evaluated
exceeded a screening benchmark for either chromium or nickel, nor did any values detected by
ORD monitoring on the Ground Zero perimeter (Figure 18) exceed any benchmark values for
chromium or nickel. On the basis of the results reported, chromium and nickel releases would
not have been expected to cause any adverse health effects within Ground Zero.
Approximately 512 monitoring samples collected at sites surrounding Ground Zero were
evaluated for chromium, including 86 samples taken at the Staten Island landfill and 16 samples
from personal air monitors worn by NYC fire department personnel. Approximately 637
monitoring samples collected at sites surrounding Ground Zero were evaluated for nickel,
including 86 samples taken at the Staten Island landfill. Samples were collected between
September 23 and January 31. None of the samples evaluated for either chromium or nickel
exceeded a screening benchmark. On the basis of the samples collected, chromium and nickel
releases would not have been expected to cause any adverse health effects at sites surrounding
Ground Zero.
Like most contaminants, however, elevations in chromium were seen in concentrations
measured near Ground Zero, and near September 11 in time. At the Ground Zero monitoring,
WTC building 5, chromium was not detected in four samples from September 23 to October 8,
but then it was detected at 0.24 and 0.38 |ig/m3 on October 11 and October 15. Further sampling
at Ground Zero through February of 2002 showed mostly non-detects (9 samples) and samples
near typical background for chromium (4 samples between 0.02 and 0.07 |ig/m3), except for one
higher reading at 0.22 |ig/m3 in January, 2002. Chromium sampling at all other sites around
Ground Zero showed the same trend: elevations above typical urban background through about
mid-October, with measurements then dropping to typical urban background (with a spike in
January, which may or may not be due to Ground Zero emissions) through the sampling in
February of 2002.
Unlike chromium, nickel was not found elevated above background at any time or location
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in sampling. Measurements were mostly non-detects in within Ground Zero and in all locations
measuring nickel, with sporadic measurements all less 0.1 |ig/m3.
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IV.c. Polychlorinated Biphenyls (PCBs)
PCBs are a group of synthetic organic chemicals potentially composed of 209 individual
chlorinated biphenyl compounds (known as congeners). PCBs were manufactured as mixtures
of individual compounds having 1 to 10 chlorine atoms on the molecule. Being relatively stable
compounds, their high boiling points and resistance to breakdown by high temperatures made
them useful in a broad array of industrial applications. Furthermore, as PCBs do not conduct
electric current, they were useful for commercial purposes as insulating material and electrical
dielectric fluid in transformers and capacitors.
In 1971, Monsanto Corporation, the major U.S. producer, voluntarily restricted the sales of
PCBs to uses as dielectric fluids in "closed electrical systems." This restriction was prompted by
growing evidence of PCBs' persistence in the environment, their tendency to bioaccumulate in
animal tissues, and their toxic effects, namely as probable human carcinogens. Monsanto ceased
PCB manufacture in mid-1977 and shipped the last inventory in October 1977 (Erickson, 1997).
Regulations issued by EPA beginning in 1977, principally under the Toxic Substances Control
Act (40 CFR 761), have strictly limited the production, import, use, and disposal of PCBs.
Because the WTC was built in the early 1970s, it can be surmised that PCBs may have
been present or contained in transformers, capacitors, electrical insulating and cooling
applications, fire-resistant coatings to building materials, and electrical fluorescent lighting
fixtures. As a consequence of the collapse of the WTC towers, many of these materials were
pulverized, ruptured, or burned, which caused PCBs to be released into the surrounding
environment. Additionally, PCBs were likely entrained within the smoke plume that emanated
from the debris piles at Ground Zero. The primary focus of this section is to evaluate the
potential human health risks that may be associated with inhalation exposure to the variable air
concentrations of PCBs measured in lower Manhattan in the aftermath of the disaster.
IV.c.l. Air Monitoring for PCBs
PCBs were monitored at 12 different sites around Ground Zero and in other areas of lower
Manhattan. Several hundred ambient air samples were collected between September 16, 2001,
and April 24, 2002. One-day samples were taken using a high-volume polyurethane foam (PUF)
and glass fiber filter (GFF) sampler. The GFF is used to collect and retain PCB- contaminated
particles that may be present in the air, whereas the PUF material is used to capture any gaseous
form of PCBs. In this monitoring program, only the sum of the PCB congeners present in air
was quantified. Figure 21 displays the locations of the PCB air monitoring stations in lower
Manhattan.
The primary source of PCB monitoring data used in this analysis was the publicly
accessible information posted on EPA's WTC web site (http://www.epa.gov/wtc). This
information is current through April 24, 2002. Table 3 presents a summary of the ambient air
sampling results for PCBs in and near the WTC disaster site.
To put these measurements into perspective, background levels of total PCBs in air at
urban locations in the U.S. are typically in the range of 1 to 8 ng/m3 (ATSDR, 2000a). Slightly
elevated air concentrations were found up to 1 month after September 11 only at the Ground
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Zero site, WTC Building 5 SW. The highest one-day PCB air measurement of 153 ng/m3
occurred on October 2, 2001. This level is approximately three-fold higher than the next two
PCB levels observed at WTC Building 5 on September 16 and October 4: 55.9 and 58.6 ng/m3,
respectively. By November 2, PCB levels at this site had further decreased to 18 ng/m3.
Measurements from November 6, 2001 to April 24, 2002 showed that total PCB levels in air
decreased to below the limits of detection. Barclay and West Broadway registered the next
highest one-day PCB air concentration at 77 ng/m3 on October 4. This monitor bordered a
restricted zone, but could represent a concentration in an area just above the corner of Barclay
and West Broadway that was unrestricted after September 19. This October 4 measurement was
about nine times greater than the measurement taken October 2 at this site (8.3 ng/m3), and
approximately ten times higher than typical urban background air. By November 2, PCB air
levels had decreased to 9.7 ng/m3. Following November 2, total PCB was not detected at
Barclay and West Broadway until February 19, 2002, at which time a concentration of
approximately 3 ng PCB/m3 was detected. From February 24, 2002, through April 24, 2002,
PCB levels dropped below the limit of detection. Because the limits of detection were within the
range of typical urban air measurements, it can be concluded that PCBs had dropped to and
remained within this range of typical urban air concentrations after November 8.
To summarize, elevations above the typical background range of 1 - 8 ng/m3 were only
seen in the initial month after 9/11, and only within Ground Zero and the border sampling
location of Barclay and West Broadway. All monitoring sites to the west of Ground Zero
showed no elevation above background PCB concentrations at any time in the month following
the disaster. By November 8, PCB levels in air were within the range of expected urban
background air at all monitoring locations, including Ground Zero.
IV.c.3. Potential Human Health Consequences of Exposure to PCBs in Air
Different approaches are used here to assess potential health effects of exposure to PCBs at
or near the WTC site. First, EPA's procedure for estimating cancer risk is used. Then,
comparison of air concentrations to benchmarks published by ATSDR, NIOSH, and OSHA are
conducted.
EPA currently classifies PCBs as B2 carcinogens; a probable human carcinogen (IRIS,
2002). The basis for this classification stems largely from long-term animal studies
supplemented with human studies. A 1996 study found liver tumors in female rats exposed to
Aroclorsl260, 1254, 1242, and 1016, and in male rats exposed to 1260. These mixtures contain
overlapping groups of congeners that, together, span the range of congeners most often found in
environmental mixtures. Earlier studies found high, statistically significant incidences of liver
tumors in rats ingesting Aroclor 1260 or Clophen A 60 (Kimbrough et al., 1975; Norback and
Weltman, 1985; Schaeffer et al., 1984). Mechanistic studies are beginning to identify several
congeners that have dioxin-like activity and may promote tumors by different modes of action.
PCBs are absorbed through ingestion, inhalation, and dermal exposure, after which they
are transported similarly through the circulatory system. This pattern provides a reasonable
basis for expecting similar internal effects from different routes of environmental exposure.
Information on relative absorption rates suggests that differences in toxicity across exposure
routes are small. The human studies are being updated; currently available evidence is
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inadequate, but suggestive of PCB carcinogenicity.
From the dose-response data derived from animal studies, the EPA has calculated an upper
bound cancer slope factor of 1*10"4 [|ig/m3]"' associated with continuous lifetime inhalation
exposure to PCBs. This slope factor pertains to exposure to total PCBs, which may or may not
contain dioxin-like PCBs. For exposure to dioxin-like PCB congeners alone, the slope factor
developed for dioxin-like compounds should be applied (EPA, 2000a). This assessment does not
consider exposure and risk from dioxin-like PCBs because these congeners were not measured
separately. The Toxic Equivalent (TEQ) concentrations discussed in the dioxin section below
are specific to dioxin and furan congeners only.
A cancer risk from a less-than-lifetime inhalation exposure to total PCBs is given as:
Risk = LAC * UR	(2)
where LAC is the air concentration averaged over a lifetime, calculated as: AC * [ED/LT],
where AC is the average air concentration during the period of exposure (|ig/m3), ED is the
exposure duration (days), LT is lifetime (days), typically 70 years, and UR is the unit risk factor,
expressed in units of 1/concentration.
In order to conduct a simple screening exercise to evaluate the cancer risk from inhalation
of elevated levels of PCBs near the WTC site, a representative air concentration and a time
during which exposure to that concentration occurred need to be determined. The areas in which
PCB air concentrations were elevated were generally located within the "restricted zone". Still,
even if an individual were exposed to the highest concentration found at 153 ng PCB/m3 for a
period of 1 month (and all the data suggests that elevations did not exist beyond 1 month), the
lifetime cancer risk would be estimated at about 2*10"8 (calculated as: [0.153 |ig/m3] * [30 days/
(70 years*365 d/yr)] * [1*10"4 (|ig/m3)"'] ). EPA regulatory programs, such as the Superfund
Program, typically consider individual incremental cancer risk estimates made in this manner
(i.e., in the context of a scenario-based risk assessment) in the range of 10"4 to 10"6 to be of
potential significance, depending on the circumstances. On this basis, an incremental cancer risk
estimate in the range of 10"8 is judged to be insignificant.
ATSDR has published a Toxicological Profile for PCBs (ATSDR, 2000a). This
Toxicological Profile is a comprehensive review and summary of existing health effects
information relevant to human exposures. From this review, it is concluded that all the measured
PCB levels in air in or around the WTC site were well below the levels of significant exposure to
PCB mixtures that were found not to cause adverse effects in experimental animals as a
consequence of short-term inhalation exposure. These no-observed-adverse-effect-levels
(NOAELs) in experimental animals ranged from 1.5 x 106 ng/m3 for renal effects to 9 xl03ng/m3
for hepatic effects. These NOAELs are one to six orders of magnitude higher than the highest
PCB air levels measured in Lower Manhattan.
Occupational exposure limits provide an additional perspective by which to evaluate
potential non-cancer health effects that may be associated with inhalation exposure to PCBs
measured in the air at or near the WTC site. NIOSH publishes RELs and OSHA publishes PELs
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for occupational exposures to chemical contaminants. The NIOSH REL is 1 x 103 ng/m3 as an 8-
hr TWA air concentration (NIOSH, 2002). The REL is associated with long-term or repeated
exposures and is protective of effects on the liver and the reproductive system. All PCB air
measurements at or near the WTC site have been below the NIOSH REL. The OSHA PEL is 5 x
105 ng/m3 as an 8-hr TWA air concentration (NIOSH, 2002). The PEL is associated with long-
term or repeated exposures and is protective of effects on the skin (dermatitis). All PCB air
measurements at or near the WTC site have been below the OSHA PEL.
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Table 3. Summary of PCB monitoring data between September, 2001, and April, 2002.
Location
Sampling Date
Concentration
ng PCB/m3 air
Sampling Date
Concentration
ng PCB/m3 air
Albany &
Greenwich
9/16 - 10/4; 7 samples
ND
11/02-12/11; 10 samples
ND
10/8
9.2
12/19/01
2.2
10/11 -10/26; 4 samples
ND
12/27 - 4/24; 29 samples
ND
10/30/01
1.8


Albany & South
End
9/16 - 4/24/; 53 samples
ND


Barclay & West
Broadway
9/16/01 & 9/23/01
ND
10/15 - 10/30; 4 samples
ND
9/27
38.7
11/02

10/2
8.3
11/8 - 2/14; 23 samples
ND
10/4
77.0
2/19
3.2
10/8
ND
2/21 - 4/24; 15 samples
ND
10/11
25.0


Church & Dey
9/16
7.0
10/8
4.5
9/23
4.0
10/11
2.2
9/27
5.0
10/15 - 10/26; 3 samples
ND
10/2
17.9
11/02
3.3
10/4
13.3
11/8 - 4/24; 39 samples
ND
Church & Vesey
11/15 -11/27; 4 samples
ND
12/11
1.4
12/4
1.7
12/19 - 4/24; 30 samples
ND
12/6
ND


EPA TAGA Lab
9/11 - 4/24; 54 samples
ND


Liberty & Trinity
9/16
8.1
9/23 - 4/24; 52 samples
ND
Liberty &
Broadway
9/23 - 9/28; 3 samples
ND
10/8
16
10/2
8.2
10/11 - 10/26; 4 samples
ND
10/4
ND


Rector & South
End
9/16 - 4/11; 51 samples
ND


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Table 3. Summary of PCB monitoring data between September, 2001, and April, 2002 (cont'd).
Location
Sampling Date
Concentration
ng PCB/m3 air
Sampling Date
Concentration
ng PCB/m3 air
Vesey & West
9/16 & 9/27
ND


Liberty & South
End
9/23 - 5/28; 67 samples
ND


WTC Building 5
SW
9/16
55.9
10/15
16.0
10/2
153.0
10/18
5.7
10/4
58.6
10/26
6.8
10/8
18.1
11/2
18.2
10/11
28.2
11/6 - 4/24; 38 samples
ND
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SERA
Figure 21. Location of PCB monitoring stations.
KEY
1)	EPATagaLab
2)	Barclay & West Broadway
3)	Church & Vesey
4)	Church & Dey
5)	Liberty & Trinity
6)	Liberty & Broadway
7)	Liberty & Greenwich
8)	Rector & South End
9)	Albany & South End
10)	Liberty & South End
11)	Vesey & West
11) WTC Building 5 SW
hwW-'?-
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IV.d. Dioxin
Dioxin-like compounds (referred to also in discussions below simply as "dioxins") are
formed during combustion, and it is expected that production of these compounds would have
resulted from the initial impact and ensuing fires at the WTC. Dioxin-like compounds may be
formed in other ways as well, such as in the chlorine bleaching process for paper products or in
the manufacturing process for certain chlorinated organic chemicals. However, uncontrolled or
improperly controlled combustion appears to be the major source of new emissions (EPA, 2000).
A total of 30 compounds are considered to be "dioxin-like": 7 polychlorinated dibenzo-p-dioxins
(abbreviated dioxins), 10 polychlorinated dibenzofurans (furans), and 13 coplanar PCBs. These
individual compounds are called "congeners." Measurements at the WTC included only the 17
polychlorinated dioxin and furan congeners, not the PCB congeners (total PCBs were measured,
as discussed above). Because dioxin-like compounds are present at minute quantities,
concentrations in this section will be described in terms of picograms per cubic meter (pg/m3).
Concentrations of dioxin-like congeners are expressed on a toxic equivalent, or TEQ basis.
A TEQ concentration is calculated as the sum of the toxically equivalent concentrations of each
of the 17 congeners. A congener's TEQ concentration is calculated as its concentration (C;)
times its toxicity equivalency factor, or TEFr TEF values are equal to 1.0 or less, and relate the
toxicity of 16 of the 17 congeners to the most toxic congener, 2,3,7,8-TCDD (the 17th congener
naturally assigned a TEF of 1.0). An overall TEQ concentration is, therefore, IXTEF^CJ.
When a congener was not detected in the sample, a value of one-half the detection limit was used
for that congener in calculating the TEQ concentration. This is the traditional approach to
calculating a TEQ concentration when some of the congeners are not detected and others are;
alternate approaches include assigning either 0 or the detection limit to the congeners that are not
detected.
The TEQ concentrations on the WTC web site were developed using the "International" set
of TEF values (I-TEF; EPA, 1989). In 1998, the World Health Organization proposed a new set
of TEF values (WHO-TEF; Van den Berg, 1998). The principal change relevant to quantifying
the TEQ concentration of a mixture comprised of the 17 dioxin and furan congeners is that the
TEF for the penta dioxin-like congener, 1,2,3,7,8-PCDD, has been increased from 0.5 to 1.0.
The other change of less impact to calculating the TEQ concentration is that the TEF values of
the two octa congeners, OCDD and OCDF, were reduced from 0.001 to 0.0001. Since the penta
congener occurs in most samples, the net effect of this change is to increase the TEQ
concentration slightly, in the range of 5-10%, depending on the prevalence of 1,2,3,7,8-PCDD in
the sample. For example, on the sample taken from the WTC Building 5 monitor on September
23, when the I-TEQ concentration was 161 pg TEQ/m3, the 1,2,3,7,8-PCDD concentration was
40.8 pg/m3. In the I-TEF scheme, this contributes 20.4 pg/m3, but in the WHO-TEF scheme, this
would add 40.8 pg/m3 to the final TEQ concentration. Therefore, the measurement of 161 pg
TEQ/m3 would increase to 181 pg TEQ/m3 when switching to the WHO-TEF scheme, an
increase of about 12%. An examination of the data shows that other I-TEQ concentrations
would also increase, some by less than 5%.
This assessment uses the I-TEQ concentrations presented on the EPA WTC web site.
Converting to WHO-TEQ concentrations would make a small and insignificant change to the
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calculations presented in this section, would not result in changing any of the principal findings,
and would possibly be confusing to those who notice a difference in the concentrations described
here compared to those posted on the EPA web site.
Some of the major health risks associated with dioxin exposure include, but are not limited
to, cancer and noncancer effects, including reproductive, developmental, and immunologic
effects. A complete discussion of the health effects of exposure to dioxin-like compounds can be
found in EPA's draft Dioxin Reassessment Document (EPA, 2000). This WTC report draws on
procedures outlined in that document for conducting simple screening assessments relating to
potential long-term cancer and noncancer effects from exposure to dioxin concentrations
measured on and near the WTC site.
IV.d.l. Dioxin Air Monitoring Data
Figure 22 shows the location of 16 air monitoring sites at which dioxin measurements have
been taken. Four of the sites had very few samples, so the focus in this section is on the 12
samplers that had a significant number of samples. At all sites, high-volume air samplers were
used. Each sampler contained both a GFF and a PUF cartridge. The GFF is used to collect and
retain particle-phase dioxins, whereas the PUF material is used to capture gas-phase dioxins.
The GFFs and PUFs were sent to laboratories for measurement of the 17 dioxin-like congeners
using EPA method SW8290.
Two different groups conducted the dioxin monitoring. Nine of the 12 sites measuring a
significant number of dioxin samples were "lettered" sites managed by the EPA's Environmental
Response Team (EPA ERT). These 9 sites sampled for 8 hours per sampling event. On the
other hand, 3 of the 12 sites were "numbered" sites were established by the New York State
Department of Environmental Conservation (NYSDEC), and they monitored for 72 hours per
sampling event. For dioxin sampling, these 3 NYSDEC samplers were managed by EPA's
Region 2 personnel, who sent the samples to EPA's Region 7 laboratory for analysis. For this
reason, these will be referred to as the Region 2/7 monitors/samples.
The amount of time the monitor operates directly affects the amount of air that went
through the monitors for dioxin collection: the Region 2/7 sampling captured dioxins contained
in about 1000 m3 of air (i.e., about this much air was drawn into the sampler over 72 hours),
whereas the EPA ERT sampling captured dioxins in about 7 m3 air. The majority of the EPA
ERT samples simply did not contain enough mass of dioxins to be able to detect, much less
quantify, the dioxin-like congeners in the sample. When the method cannot detect the congener
in the sample, a result of "nondetect" (ND) is reported, and the detection limit (DL) is supplied.
The method's detection limit is calculated by dividing the lowest amount of dioxin that it can
detect (on the GFF and PUF) by the air that contained that amount, namely the air that flowed
through the sampler. The greater the air flow, the greater the divisor for the unchanging
detection amount, and the lower the detection limit. Except for the high concentrations
measured within and near Ground Zero from September through late November, most of the
samples taken by the EPA ERT samplers contained mostly non-detects. Therefore, TEQ
concentrations ended up being calculated with all or most congeners set equal to a value of one-
half the detection limit.
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Calculating TEQ concentrations with most congeners assigned values of one-half detection
limit is not an issue when a sufficient quantity of air is drawn into the monitor, and the inability
to measure the dioxin in the sample truly does signify a very low amount of dioxin in the sample.
For example, congeners in the Region 2/7 samples could be quantified if they were present at
concentrations higher than about 0.5 pg/m3 because enough air was drawn into the monitors
leaving behind enough dioxin molecules on the monitor's filters. The congeners in the EPA
ERT samples could not be quantified unless they were present at about 5-10 pg/m3. When most
of the congeners reported a non-detect in one of the Region 2/7 samples, the calculated TEQ
concentration was in the range of 0.01 to 0.10 pg TEQ/m3, whereas when most of the congeners
were reported as non-detect in the EPA ERT samples, the calculated concentration ranged from
0.5 to 5.0 pg TEQ/m3. As will be discussed below, typical urban air concentrations are in the
range of 0.10 to 0.20 pg TEQ/m3, and these measurements come out of studies where, like the
Region 2/7 samples, a sufficiently large quantity of air was drawn into the monitors.
Assigning one-half detection limit for non-detects is typical and appropriate for evaluating
exposure to airborne contaminants, dioxins or otherwise. In some circumstances, this practice
can underestimate the amount of contaminant in the air - i.e., when the actual concentration is
just below the detection limit and above the half-detection limit value. However, in this case, it
is clear based on comparison with the Region 2/7 samples and from other historical
measurements around the United States, that the practice of assigning one-half detection limit to
non-detects in the EPA ERT samples resulted in an overestimate of the TEQ concentration when
most of the congeners in the sample were non-detects.
For purposes of analysis in this section, a limited set of the dioxin data is used. Table 4
shows reported TEQ concentrations for the WTC Building 5 EPA ERT monitor, the Church &
Dey EPA ERT monitor, and the Park Row Region 2/7 monitor. These values were calculated at
ND = '/2 DL; in parenthesis for the two EPA ERT monitors is the TEQ calculated at ND = 0.
The WTC Building 5 monitor had the highest concentrations, and the Church & Dey monitor
was in the predominant downwind direction for most monitoring events and had the second
highest measurements. The Park Row monitor began operation on October 12 and had
numerous measurements through March of 2002. Figure 22 shows the location of these three
monitors. The following observations are based on the data in Table 4:
The WTC and Church & Dey measurements from the first measurement day of
September 23 through November 21 show unambiguous elevation, with
concentrations ranging from about 10 to 170 pg TEQ/m3.
In this same time frame and for these two samplers, the influence of having high
detection limits is seen in a few samples (WTC sample on 10/4: 176 pg TEQ/m3
at ND = V2 DL versus 140 pg TEQ/m3 at ND = 0; WTC sample on 10/11: 52.4
versus 9.6), but mostly, the congeners were detected and quantified, and TEQs
were similar at ND = 0 and ND = V2 DL.
The 6 Park Row measurements between October 12 and October 29 averaged 5.6
pg TEQ/m3. These measurements are consistent with the mid- to late-October
measurements at Church & Dey, which is slightly off-site from Ground Zero, of
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10 to 20 pg TEQ/m3. Further, the Church & Dey measurements of 10 - 20 pg
TEQ/m3 for mid to late October are consistent with the WTC measurements for
that time period of 20 - 50 pg TEQ/m3. In other words, the highest measurements
are onsite (WTC); the next highest measurements are slightly offsite (Church &
Dey), and slightly lower concentrations are farther offsite (Park Row). This is
strong evidence that emissions from the WTC site are the cause for elevated air
concentrations within and near the WTC site.
•	The Park Row measurements from December 2001 through the last reported
measurements of March 18, 2002, are less than 0.11 pg TEQ/m3, and all the 2002
measurements are less than or equal to 0.05 pg TEQ/m3. These values are
consistent with those of the other two Region 2/7 samplers (see Figure 22). They
are also consistent with typical urban concentrations of dioxin TEQs (see
discussion after bullets), which leads one to believe that these concentrations
might be representative of typical "background" New York conditions.
The December through April measurements from the WTC Building 5 and
Church & Dey monitors are nearly all non-detects. The reported concentrations
average about 1.4 pg TEQ/m3, but this is of limited interpretive value since the
detection limits were too high. The actual concentrations could be more like the
concentrations of about 0.05 pg TEQ/m3 found at the Park Row sampler, but it is
not possible to conclude that since the data are not available.
Other measurements made in the United States and around the world can be used to put
these measurements in perspective. As noted earlier, EPA's draft Dioxin Reassessment
compiled urban and rural air monitoring studies and found average ambient concentrations of
0.12 pg TEQ/m3 for urban and 0.017 pg TEQ/m3 for rural settings. Higher concentrations have
been identified in the literature, particularly near a known source of dioxin emissions. The
highest TEQ concentration reported in the U.S. was >1.0 pg/m3, downwind of an incinerator in
Niagara Falls, NY. Concentrations in the plume of a solid waste incinerator in Columbus, OH,
that was known to be emitting large amounts of dioxins were about 0.25 pg TEQ/m3. In this
case, the stack was very tall (about 80 meters) and air measurements were taken about 2
kilometers away. Background air concentrations in Columbus were measured to be about 0.05
pg TEQ/m3.
Air concentrations near an incinerator in Japan adjacent to a U.S. Naval Air Base were
regularly measured on the base for dioxin-like compounds. Measurements at the nearest
downwind monitor, at about 200 meters, averaged 3.5 pg TEQ/m3 for weekly samples over a 15-
month period. For five samplers (including the nearest downwind sampler) at various locations
on the base up to 800 meters, the average air concentration was 1.6 pg TEQ/m3. An examination
of the air concentration data on this base in conjunction with wind rose data, suggested that a
background air concentration in this area was less than 0.5 pg TEQ/m3 and that measurements
above that were due to the influence of the incinerator (Walker, et al., 2002). Other
measurements in cities in Japan have been in the 0.3 to 0.7 pg TEQ/m3 range, and these are the
highest that have been reported as typical air concentrations worldwide.
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Although none of these literature measurements can be assumed to represent New York
levels, they provide some basis for perspective. Certainly, no reports in the literature could be
found on similar circumstance where there is, what is essentially, an area source at ground level
continually emitting dioxins near to where individuals are exposed. It would be reasonable to
conclude that the concentrations to which individuals could potentially be exposed, in the range
10.0 to 170.0 pg TEQ/m3 within and near the WTC site found through the latter part of
November, are likely the highest ambient concentrations that have ever been reported.
IV.d.2. Potential Human Health Consequences of Exposure to Dioxins in Air
The exposure of humans to dioxins is predominantly through the food supply; about 95%
of exposure is through consumption of animal food products. Inhalation exposure and
absorption via the skin are generally minor pathways for the average U.S. citizen (i.e., the
background population). EPA has estimated that about 4% of the background human dose of
dioxin is due to inhalation, based on an average urban level of 0.12 pg TEQ/m3 and an inhalation
rate of 13.3 m3/day. If the concentration of dioxin in the air is increased, the amount of exposure
due to inhalation would be increased, but the total amount of dioxins contributed by the
inhalation pathway might still be small in comparison to the contribution made by food
ingestion.
In the WTC situation, elevated dioxin concentrations in the air can be expected to increase
the proportion and extent of human exposure via inhalation and possibly skin contact routes for
those people residing or working close to the WTC location. The extent to which these elevated
atmospheric levels will translate into increased human doses depends on an individual's pattern
of exposure, considering, for example, his or her location in relation to the WTC and downwind
areas; the duration and time period of exposure such as workshift and return to residence
patterns, movement and activity patterns during the time of elevated atmospheric levels; and
whether respiratory protection devices were used. Dioxin-like compounds exist substantially in
the atmosphere attached to particles, and these devices would remove a substantial portion of the
dioxins through the removal of particulates; if these respirators contained a carbon filter, a
substantial portion of the dioxins in vapor phase would also be removed.
This section will use the data shown in Table 4 to conduct cancer and non-cancer
assessments of an individual's inhalation exposure to dioxins. The procedures used are
described in detail in the draft Dioxin Reassessment (EPA, 2000; available at,
http://www.epa.gov/ncea/dioxin.htm), with further references supplied below as necessary.
1. Daily Inhalation Doses
Cancer and non-cancer assessments entail the development of a "dose" term, which in this
case is the dose received via inhalation. Inhalation dose estimates require assumptions about the
hourly rate of inhalation (m3/hr), the number of hours per day a person inhales at the site where
he or she could be exposed (which could obviously be less than 24 hours if the individual does
not live in the vicinity where air concentrations measurements were taken), the time period
during which this exposure occurs, and, of course, the air concentration to which the individual
is exposed.
Daily inhalation exposure dose is given by:
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DD = [IN * HRD * C * ABS]/[BW]
(3)
where DD is daily dose (pg TEQ/kg-day); IN is the inhalation rate (m3/hr), HRD is the hours/day
of inhalation, C is the concentration (pg TEQ/m3), ABS is the fraction of contaminant inhaled
which is absorbed (unitless), and BW is the body weight (kg). The draft Dioxin Reassessment
assumes an adult body weight of 70 kg and an absorption fraction of 0.8 for TEQ exposures,
both from inhalation and food consumption, and these assumptions are used here. The average
daily dose (ADD) is calculated simply as the average of the daily doses over the period of
exposure.
2. Exposure Scenarios
The scenarios which were evaluated here include:
1)	WTC worker: This individual was exposed 10 hours per day, 5 days per week, in the time
period between September 12 and November 30, 2001. This time frame roughly corresponds to
the time when it seemed clear that dioxin air levels were elevated according to the monitoring
data. Measurements from the WTC Building 5 monitor represent the concentration to which this
individual is exposed. A time-weighted average (TWA) air concentration was derived for this
period. The air concentration between September 12 and September 23 (the date of the first
measurement at the WTC monitor) is assumed to be equal to the September 23 measurement,
and the concentration between November 8 (the last date in November for the WTC monitor)
and November 30 was similarly assumed to be equal to the measurement on November 8.
These seem to be reasonable assumptions since the September 23 measurement from the WTC
monitor was the second highest found at 161 pg TEQ/m3, and the November 8 measurement of 5
pg TEQ/m3 reasonably reflects the downward trend of measurements at the site. Between
September 12 and November 30, a TWA air concentration was derived to represent the
concentration to which the workers were exposed. A TWA concentration is not the same as the
simple average of concentrations measured. To derive the time-weighted concentration,
concentrations were assigned to each day between September 12 and November 30. From one
measurement to the next, air concentrations were assumed to linearly rise or fall. For example, if
the concentration was measured as 100 pg TEQ/m3 on one day and 5 days later it was 50 pg
TEQ/m3, the concentrations assigned to the intervening days were 90, 80, 70, and 60 pg TEQ/m3.
The TWA concentration is then simply the average of all the concentrations assigned to days
when the worker was assumed to be exposed. With these assumptions, the average TEQ
concentration during this time was calculated as 60.7 pg/m3. The rate of inhalation for a WTC
worker was 1.3 m3/hr. This is equivalent to the rate for a "laborer" as quantified in EPA's
Exposure Factors Handbook (EPA. 1997).
2)	Office worker: This individual is exposed 10 hours per day, 5 days per week, and the
exposure began on September 19, corresponding to the time when individuals were allowed back
into office buildings outside of the Ground Zero site itself but in areas initially "restricted" near
Ground Zero. The office worker was assumed to be exposed to air concentrations measured by
the Park Row monitor. This simplistically assumes that the air concentrations within office
buildings near Ground Zero were similar to air concentrations outside of office buildings this
close to Ground Zero. The period of exposure was September 19 to November 30, and the same
strategy to derive TWA concentrations was used as for the WTC worker. The TEQ air
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concentration from September 19 to October 12 was assumed to be 8.4 pg/m3, the measurement
on October 12 at the Park Row monitor, and the TWA concentration between September 19 and
November 30 was 4.8 pg TEQ/m3. The rate of inhalation for an office worker was assumed to be
the average inhalation rate of 1.0 m3/hr, which is defined as "light activity" in EPA's Exposure
Factors Handbook fEPA. 1997).
3s) Resident: This individual was exposed 24 hours per day, 7 days per week, and the exposure
began on September 19 and ended on November 30. As with the office worker scenario, the
assumption here again was that individuals living near Ground Zero, in the vicinity of the Park
Row monitor, were more exposed after September 19, when some of the locations outside of
Ground Zero opened up to workers and residents. The daily inhalation rate was 0.55 m3/hr, an
average daily rate, activity unspecified, as developed in EPA's Exposure Factors Handbook
(EPA, 1997). As noted, the air monitor used to characterize the air concentration was the Park
Row monitor, which was located in an area not restricted after September 19. The average TEQ
concentration during this time was 4.8 pg/m3, as noted above.
3.	Procedure for Cancer Risk Estimation
These assumptions and the resulting ADDs are shown in Table 5. Cancer risk were
estimated simply as:
LADD = ADD * [ED/LT]	(4a)
Risk = LADD * SF	(4b)
where LADD is the lifetime daily dose (pg TEQ/kg-day), Risk is the upper bound incremental
excess lifetime cancer risk that results from the exposure described by LADD, ADD is the
average daily dose during the period of exposure (pg TEQ/kg-day), ED is the exposure duration
(days), and LT is lifetime (days), typically 70 years, and SF is the upper bound cancer slope
factor, expressed in inverse units to LADD, or [pg TEQ/kg-day]"1. The SF of .000156 [pg/kg-
day]"1 was developed by EPA in 1984 for 2,3,7,8-TCDD exposures (EPA, 1984). It is applied to
TEQ exposures in this cancer risk screening exercise. The draft Dioxin Reassessment (EPA,
2000) proposed an SF of 0.001 [pg/kg-day]"1, which applies to dioxin TEQ exposures.
4.	Procedure for Non-Cancer Risk Estimation
For noncancer risk, a different approach was taken. The best indicator of exposure for
persistent, bioaccumulative, toxic substances such as dioxin is the concentration of the chemical
in the organ or tissue of concern. A common metric for dioxin exposure is the "body burden",
which is defined as the concentration of dioxins in the body, typically on a whole-weight basis.
Body burden in this screening assessment is expressed on a lipid basis. It is assumed that adults
are 25% lipid by weight, so that a lipid-based concentration can easily be converted to a whole-
weight-based concentration by multiplying by 0.25.
Dioxins build up and decline over prolonged periods of time, since the overall biological
half-life (the time for half the chemical to dissipate by either biological degradation or
elimination) of dioxins in the human body is approximately 7 years. The use of the body burden
as the measure of dose has implications for short-term exposures, such as those near the WTC
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site, where elevated exposure rates limited to a period of days or months contributed to a pool of
dioxin already accumulated in the human body over a lifetime. The current estimated body
burden of dioxin (including only the 17 dioxin and furan congeners, not the dioxin-like PCB
congeners discussed above) in U.S. adults is approximately 18 pg TEQ per gram of body lipid
(18 ppt TEQ lipid). This average was derived from data on older as well as younger adults.
Because exposures were known to be higher in the past, the body burdens of younger adults will
be lower than those of older adults. Another factor contributing to the variability seen in the
entire population is dietary pattern; individuals whose diets are higher in animal fat will have
higher body burdens.
The effects of dioxin in humans range from biochemical changes at or near background
levels to potentially adverse effects of increasing severity as body burdens increase above
background levels. The "margin of exposure", MOE, can be defined as the ratio of body burden
where effects are found divided by a body burden at a level of interest. The MOE for dioxin at
current average body burdens (i.e., current average body burdens being the level of interest) is
considerably less than that typically seen for environmental contaminants of toxicological
concern. The potential contribution to health risks from specific dioxin sources or specific
exposures, such as exposures from inhalation of air with elevated levels of dioxin, is best
evaluated through calculating the incremental contribution of this source to the body burden.
The draft Dioxin Reassessment has assumed that a one-compartment, first-order
pharmacokinetic (PK) model can be used to estimate the body burden that results from a specific
intake regime. This simple PK model and its application to dioxin TEQs is also described in
Lorber (2002). For an exposure of a finite time, the nonsteady-state form of this model to predict
an increment in body burden (IBB) from a constant intake dose is given by:
IBB = [ADD/(k * LW)] * [1 - e"kt]	(5)
where IBB is the increment of body burden on a lipid basis (pg/g, or ppt, lipid basis); ADD is the
average daily dose (pg TEQ/day; not on a body weight basis), k is the first-order dissipation rate
constant (1/day), LW is the weight of body lipids (g; equal to full body weight times 0.25, as
described above), and t is the time of exposure (days). Use of Equation (5) with an average
ADD over the period of exposure will provide an estimate of body burden at the end of the
exposure. This is the time when the incremental body burden will be at its largest. In the
scenarios of this assessment, different daily exposures result from different air concentrations as
well as differences in exposure - 5-day work week followed by 2 days of non-exposure for the
office worker scenario. Equation (5) is applied on a daily time step using Excel® spreadsheet
procedures for this simple screening exercise.
A value of 17,500 g for the lipid weight (calculated as: 70 kg * 0.25 lipid fraction * 1000
g/kg), and a k of 0.000267 day"1 ( = 0.098 yr"1, corresponding to a 7.1 year half-life) will be used
(Lorber, 2002). Results for this exercise include both an incremental body burden estimate, the
IBB of Equation (5), calculated at the end of the exposure period, as well as a percent increase
over background this represents. This percent increase is calculated as, [IBB/BK] * 100%. The
BK is the background, which was assigned a value of 18 ppt TEQ lipid, as described above.
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5. Results and Discussion
The exposure assumptions, the cancer risk estimates, and the incremental body burdens,
are shown in Table 5. Before commenting on these results, it is important that they be put into
perspective for general U.S. population dioxin TEQ exposures. As noted above, the background
body burden of dioxin TEQs in adults is 18 ppt lipid. The draft Dioxin Reassessment estimates
that the general adult population background TEQ exposure is 65 pg/day, or, expressed on a
body-weight basis, 0.93 pg TEQ/kg-day. If this exposure is experienced over a lifetime, then the
resulting incremental cancer risk from background TEQ exposure to the general adult
population is equal to about 1.4*10"4 (assuming the 1984 SF of 0.000156 [pg/kg-day]"1).
Table 5 shows that the TEQ ADD due only to inhalation during the period of exposure is 9
pg/kg-day for the WTC worker, 0.55 pg/kg-day for the office worker, and 0.73 pg/kg-day for the
nearby resident. Although the WTC worker's daily exposure is higher than that of the general
U.S. population, it is experienced for only a small number of days. Therefore, when averaged
over a lifetime, the WTC worker dose calculates to an incremental cancer risk that is 3*10"6,
which is about 2 orders of magnitude lower (100 times lower) than the U.S. background cancer
risk from dioxin-like compounds (1.4*10"4 as calculated above). The office worker and resident
experience incremental lifetime cancer risk at about 3*10"7, three orders of magnitude lower
(1000 times lower) than background. EPA regulatory programs, such as the Superfund Program,
typically consider individual incremental cancer risk estimates made in this manner (i.e., in the
context of a scenario-based risk assessment) in the range of 10"4 to 10"6 to be of potential
significance, depending on the circumstances. Exposure to dioxin-like compounds represents a
unique circumstance, in that background exposures are already within this range and, in fact, at
the upper end of this range. Therefore, although the upper bound incremental cancer risk to the
WTC worker is estimated to be within the range of 10"4 to 10"6, EPA judges these incremental
cancer risks to be of minimal concern because they are 100 times and more lower than typical
background exposures to dioxin-like compounds.
For noncancer risk, an increment of body burden, IBB, approach has been used. Table 5
shows that the exposure of the WTC worker suggests that his or her body burden could rise up to
10% above current average background, but that the nearby office worker and the residents have
a rise of only 1% or less. EPA judges these incremental body burden increases to be of low
significance, given the relatively high background exposures already experienced by the general
population.
A key uncertainty remains as to the inhalation exposures that could be experienced by
WTC rescue or clean-up workers, or nearby resident and office workers, who were in the area
during the time period from about December onward. As discussed earlier, most of the samples
had non-detects, but after assuming that the concentrations in the air were one-half the detection
limit, all the measurements in 2002 from the EPA ERT samplers, which included the WTC
Building 5 monitor, the Church & Dey monitor and many others, ranged from about 0.5 to 5.0 pg
TEQ/m3, which is about 5 to 50 times higher than normal background air concentrations. The
three Region 2/7 samplers, the Park Row, Chambers St, and the Albany & West samplers,
reported concentrations near 0.05 pg TEQ/m3 from around December, 2001, through their last
reported measurements in March, 2002. These were further away or generally upwind from the
WTC site, so it cannot be assumed that they represent concentrations to which WTC workers and
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others were exposed. Because the health risk from dioxin exposure is associated with
accumulation of residues in body tissues, continued exposure throughout 2002 to dioxin, which
was possibly elevated in the air, could not be evaluated. The risk screening exercises conducted
for dioxin were limited to the time period when the concentrations were highest and dioxin was
detected.
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Table 4. Measured dioxin TEQ air concentrations at the WTC Building 5 monitor, the Church
& Dey monitor, and the Park Row monitor (all units = pg TEQ/m3; NR = not reported; all TEQ
calculated at ND = V2 DL except values in parenthesis, which are calculated at ND = 0).
Date
WTC - Building 5
Date
Church & Dey
Date
Park Row
9/23
161.0(161.0)
9/23
139.0 (139.0)
10/12a
8.35
9/27
NR
9/27
50.0 (NR)
10/14a
0.34
10/2
175.0 (170.0)
10/2
59.3 (57.2)
10/15a
4.78
10/4
176.0 (140.0)
10/4
51.9 (50.6)
10/16a
7.55
10/8
32.0 (28.7)
10/8
17.7 (15.5)
10/26
6.51
10/11
52.4 (9.6)
10/11
15.6 (11.8)
10/29
6.34
10/18
NR
10/18
9.6 (8.8)
11/1
3.05
10/26
28.1 (24.9)
10/26
11.4(10.2)
11/5
1.54
11/2
26.8 (25.4)
11/2
16.1 (15.1)
11/8
0.27
11/6
0.3 (0)
11/6
0.1(0)
11/12
1.33
11/8
5.6 (4.9)
11/8
7.6(7.1)
11/15
1.33
11/12
NR
11/12
1.3 (0.6)
11/19
2.50
ll/15b
5.4(1.6)
11/15
3.4(1.6)
11/22
1.30
11/2 lb
4.1(3.1)
11/21
10.0 (8.3)
11/26
0.80
No samples reported from 11/21
to 1/15
11/27
2.5 (NR)
11/29
0.16
12/4
0.7 (NR)
12/3
0.12
Jan 15 - April 24
n= 31
reported range: 0.4-5.5
average: 1.4 at ND - '/? DL and
0.0 at ND = 0.
12/6
0.2 (NR)
12/6
0.04
12/11
0.2 (NR)
12/10
0.05
12/19
0.6 (NR)
12/13
0.04


12/27
0.3 (NR)
12/24
0.04


Jan 3 - April 24
n= 29
reported range: 0.2 - 4.1
average: 1.4 at ND - '/? DL and
0.0 at ND = 0.
12/27
0.06


12/31
0.11


Jan - Feb
n= 17
all samples reported < = 0.05




a These Park Row samples were 24-hour samples; all other Park Row samples were 72 hour samples.
b These two World Trade Center samples were actually taken at the Church & Vesey sampler, which was sometimes
used in place of the WTC Building 5 sampler.
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Table 5. Human exposure and health risk assessment assumptions and results for dioxin TEQs.
Description
WTC worker
Office Worker
Resident
I. Exposure Assumptions and Results
Inhalation rate, m3/hr
1.3
1.0
0.55
Hours/day exposed
10
10
24
Days/week exposed
5
5
7
Air monitoring data used
WTC site
Park Row
Park Row
Period of exposure, dates/days
Sep 12- Nov
30, 57 working
days
Sep 17-Nov 30,
54 working days
Sep 12-Nov 30, 79
days
Average TEQ air
concentration, pg/m3
61
4.8
4.8
Body weight, kg
70
70
70
Absorption, fraction
0.8
0.8
0.8
ADD, pg TEQ/kg-day
9.0
0.55
0.73
II. Cancer Risk Estimates
Exposure Duration, yrs
0.16
0.15
0.22
LADD, pg TEQ/kg-day
2.0*10"2
1.2*10"3
2.1*10"3
Cancer Risk
3.1*10"6
1.9* 10"7
3.6*10"7
Percent increase over
1.4* 10"4 background risk
2.2 %
<1 %
<1 %
III. Body Burden Increases as a Measure of Potential NonCancer Risk
Dissipation rate, 1/day
0.0002671
0.0002671
0.0002671
Change in body burden, pg
TEQ/g lipid
+1.86
+0.14
+0.20
Percent increase over 18.0 pg
TEQ/kg lipid background
10%
<1 %
1 %
1This dissipation rate corresponds to a 7.1 year half-life in the body.
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T>J / IKJ i/m
cvEPA EnviroMopper
^VjJSOiSPN
Key
1	= WTC Site
2	= Liberty & Trinity
3	= Church & Dey
4	= Albany & Greenwich
5	= Barclay & West
Broadway
6	= Liberty & South End
7	= Albany & South End
8	= Rector & South End
9	= Albany & West St
10	= EPA TAGA Lab
11	= Chambers St
12	= Park Row
N = NYSDEC samplers
® = sites with very few
samples
Figure 22. Location of dioxin air monitoring. The locations marked "N" are New York State
Department of Environmental Conservation (NYSDEC) samplers maintained by EPA Region 2
with analysis of the samples by Region 7 (Region 2/7), whereas all other samplers are
maintained by EPA's Environmental Response Team (EPA ERT). See text for discussion of the
differences in the two sets of data from these two air monitoring teams.
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IV.e. Asbestos
Asbestos is a term used to describe a family of hydrated metal silicate minerals. Asbestos
exhibits some special properties, such as high tensile strength, the ability to be woven, heat
stability, and resistance to attack by acid and alkali. Thus, it was widely used for building
fireproofing insulation and other purposes during the 1960s and early 1970s. At the peak of its
demand, about 3000 applications or types of products were listed for asbestos. In 1973, EPA
prohibited the spraying of asbestos-containing material on buildings and structures for
fireproofing and insulation purposes. The use of asbestos has been sharply declining for more
than two decades. Sprayed on asbestos was used to fireproof approximately the lower half of
one of the WTC towers, and may have been used in other places in the towers as well. One of
the reasons that asbestos has been so useful is that it exists in long, thin fibers that can be
sprayed, woven or mixed. The extremely light and aerodynamic asbestos fibers also lead to their
ability to become and remain airborne. The fibrous nature also contributes to the health effects
associated with asbestos exposure.
There are six minerals whose fibrous forms are characterized as asbestos and that are
currently regulated. All the six minerals also occur in non-fibrous forms and these forms are not
known to cause any health effects. The six regulated asbestos fibers include one from the
serpentine family of minerals: chrysotile, and five from the amphibole family: fibrous reibeckite
(crocidolite), fibrous grunerite (amosite), actinolite asbestos, anthophylite asbestos, and tremolite
asbestos. Inhalation of these asbestos fibers has been linked to several adverse health effects
including primarily fibrosis of the lungs (asbestosis), benign pleural plaques and thickening, lung
cancer, and mesothelioma (a cancer of the thin membrane that surrounds the lungs and other
internal organs). It also may increase the risk of cancer at other sites, but the evidence is not
strong. Over the years the evidence has accumulated that longer thinner "asbestiform" fibers are
of more concern for human health. The widely accepted definition of the asbestiform fiber is a
particle having a length to diameter (aspect) ratio of >3:1 and a length of at least >5 |im. The
evidence is overwhelming that both the mineral content and the size and shape of the fiber
affects the severity of the disease. The respirable fibers are those with the diameter of <3 |im.
Fibers exceeding the diameter of 3 |im are considered to be non-respirable.
Asbestosis, a chronic, degenerative lung disease, has been documented among asbestos
workers from a wide variety of industries. The disease is generally expected to be associated
only with the higher levels of exposure commonly found in workplace settings (Brown et al.,
1994; Case and Dufresne, 1997). Several researchers have found that asbestosis and lung
cancer are associated with cumulative exposure to asbestos. Benign pleural plaques and
thickening also have been linked to higher cumulative exposure to asbestos (Albin et al., 1996;
de Klerk et al., 1993). Both asbestosis and benign pleural plaques result in reduced breathing
capacity and mortality. In a review of the epidemiologic evidence for asbestosis exposure-
response relationship, the World Health Organization Task Group on Environmental Criteria for
Chrysotile Asbestos (WHO, 1998) concluded that "asbestotic changes are common following
prolonged exposures of 5 to 20 f/mL." These prolonged exposures corresponded to cumulative
exposure of 50 to 200 f/mL for a 10-year exposure period. They also concluded that "the risk at
lower exposure levels is not known."
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The majority of evidence indicates that lung cancer and mesothelioma are the most
important risks associated with exposure to low levels of asbestos over a long period of time.
There is ample evidence that all types of asbestos have been found to be associated with lung
cancer. Several investigators have reported lung cancer mortality in workers exposed to
chrysotile, amosite, crocidolite, anthophyllite, tremolite, and to multiple fiber types. The onset
of exposure to time of occurrence of the disease is known as "latency period." As with most
carcinogens, asbestos-related cancers have a substantially long latency period. The latency
period for lung cancer has been reported to be 10 to 40 years. Most researchers have found that
occurrence of lung cancer depends on the cumulative dose as well as other underlying lung
cancer risk factors (U.S. EPA, 1986c; Peto et al., 1985). Similarly, several investigators have
found that all types of asbestos cause mesothelioma of either pleura or peritoneum in adults who
had occupational exposure. This finding also pertains to individuals who had no occupational
exposure but who lived with a parent, spouse, or sibling who was an asbestos worker and
presumably carried asbestos home on work clothes. Mesothelioma has a latency period of about
30 to 40 years. Lanphear and Buncher (1992) reviewed 1,105 mesothelioma cases in workers
occupationally exposed to asbestos. They reported that 99% had a latency period >15 years and
calculated a median latent period of 32 years. Further details on the toxicology and
epidemiology of asbestos exposure can be found in the recent ATSDR Toxicological Profile for
asbestos (ATSDR, 2001).
This next section reviews the air monitoring data for asbestos and discusses how these data
relate to human health benchmarks developed for asbestos. The following sections discuss the
analytical methods for measuring asbestos in air, the health risk benchmarks that measured air
concentrations will be compared to, the background concentration of asbestos that can be
compared to the measured values, and then the actual air data.
IV.e.l. Analytical Methods for Asbestos Ambient Air Measurements
The two analytical methods used in analyzing the WTC air samples for asbestos are phase
contrast light microscopy (PCM) and transmission electron microscopy (TEM). PCM, although
cheaper, is unable to distinguish between asbestos and nonasbestos fibers. It counts all fibrous
structures with a minimum diameter of 0.3 |im and has a magnification range of 100 - 400X.
Fibrous structures are defined as particles exhibiting a length of > 5 |im and an aspect ratio of
length to width of 3:1. PCM cannot resolve internal structure or distinguish the mineralogy.
PCM results are reported on a mass-per-volume basis, fiber per cubic centimeter (f/cc or f/cm3)
or, equivalently, fiber per milliliter (f/mL). TEM, on the other hand, is more expensive, but it
can count the fibrous structures with a diameter of < 0.01 |im, and it can resolve internal
structure and distinguish mineralogy. It has a magnification range of 5,000 - 20,000X. TEM
results may be reported as concentrations or, for comparison with EPA AHERA standards (see
below), as structures per square millimeter (S/mm2) of filter in the ambient air monitor used.
Details about the monitoring apparatus appropriate for measurement of asbestos using the TEM
method and the appropriate ways to count and interpret the electron microscopy results are
supplied in EPA (1987) and NIOSH (1994). Details about the PCM method for workplace
measurements can be found in NIOSH (1994) and in OSHA (1994).
TEM data, expressed on a structures per filter unit area basis (as listed on the EPA web
site), can be converted to a concentration in air in structures per cubic centimeter. This is
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accomplished by multiplying the S/mm2 term by a conversion factor defined as the area of the
filter paper, mm2, divided by the volume of air, liters or cubic centimeters, that is drawn into the
air monitor. The AHERA Final Rule establishing a 70 S/mm2 standard for asbestos in schools
(EPA, 1987; see next section for more details on this benchmark), one of the standards used in
this report to evaluate the WTC data, specifies that a volume at least 1199 L (liters; 1.199* 106
cc) must be drawn into a monitor with a 25 mm filter (this filter size corresponds to an effective
area of 385 mm2) or that a volume of at least 2799 L (2.799* 106 cc) must be drawn into a
monitor with a 37 mm filter (effective area of 855 mm2) when applying the standard. Therefore,
the conversion factors for both filters, to convert S/mm2 to S/cc, are 0.000321 mm2/cc for the 25
mm filter and 0.000305 mm2/cc for the 37 mm filter. As a reasonable approximation, all results
in S/mm2 can be converted to a volumetric S/cc basis by multiplying by 3*10"4 [S/cc]/[S/mm2],
assuming 1200 L or 2800 L is drawn through an appropriate filter. Using this conversion factor,
the AHERA standard of 70 S/mm2 is equivalent to 0.021 S/cc.
However, the conversion to S/cc still does not put the data on an equal footing with PCM
data expressed on a f/cc basis, because "fibers" are almost always different from "structures".
Structures are bundles of fibers and many more "structures" can be identified by TEM than
"fibers" by PCM because TEM can identify much smaller structures. Therefore, a TEM result
for a given air sample (expressed on a volume basis, S/cc) will generally be greater than a PCM
result for that same air sample (expressed as f/cc). In general there is not a good correlation
between PCM and TEM measurements, and the ratios of the fiber counts seen with these two
methods will vary according to the types of asbestos involved and the nature of the exposure
setting. As noted below in making some rough comparisons, ATSDR has assumed a ratio of 60
of volumetric TEM data to volumetric PCM data; that is, PCM data was multiplied by 60 to
convert the data to TEM units by ATSDR (ATSDR, 1999). The was done for the purpose of
comparing different data from around the country to make observations about background
asbestos concentrations.
As much of the health effects data on asbestos are expressed in terms of PCM f/cc, a useful
variant of the TEM technique is to include counts of structures that would be expected to be
visible under PCM and meet PCM criteria for counting as fibers. Specifically, structures
meeting a minimum diameter of >0.3 |im with length >5 |im are counted as PCM equivalent
("PCME") fibers.
IV.e.2. Risk Assessment Benchmarks for Evaluation of Asbestos Air Data
The principal benchmark used in this assessment for evaluation of asbestos in air data from
the WTC site is the Asbestos Hazard Emergency Response Action (AHERA) standard of 70
S/mm2. This standard is determined by TEM analysis. This standard is described in the Final
Rule and Notice for Asbestos-Containing Materials in Schools (40 CFRPart 763, October 30,
1987; cited in this report as EPA, 1987), and that rule also provides details on the monitoring
apparatus and the structure counting procedure. This counting procedure includes discussions on
the amount of filter area to examine with different volumes of air, and also the requirement to
count fibers with an aspect ratio of > 5:1 (aspect ratio = length to width ratio) and a length > 0.5
|im. Briefly, this count of 70 S/mm2 is specific to a minimum volume of air requirement (1200 L
if the filter size is 25 mm, and 2800 L if the filter size is 37 mm), and with this volume, a reading
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of 70 S/mm2 was evaluated as being statistically distinguishable from the count that would come
from a blank filter. That background count is about one-fourth the standard, or 17.5 S/mm2. The
AHERA rule specifies that children would be allowed back into a school that has been
undergoing asbestos abatement (removal and/or encapsulation) if the TEM readings were
consistently below the count of 70 S/mm2. This would be evidence that the concentration was
similar to background readings. Alternately, an abatement area could be deemed suitable for
occupation if samples taken within the area were statistically similar to samples simultaneously
taken outdoors in an asbestos-free environment. Details of these procedures are provided in the
Final Rule, as cited above.
It should be noted that this standard is not health based, but rather technology based. It is
also noted that the technology has improved since 1987, such that current filters often have much
less than 17.5 S/mm2, sometimes close to 0 S/mm2. Therefore, 70 S/mm2 would be much higher
than blanks and represents more than just a statistical elevation above background, above.
Finally it is noted that while the AHERA standard was originally intended as an indoor
'clearance' standard, it is being used to evaluate outdoor exposures in this assessment.
The current OSHA PEL is also used in this assessment to evaluate air concentrations of
asbestos measured using the PCM method. The PEL for occupational exposures to asbestos is
0.1 f/cc by PCM averaged over an 8-hour day (OSHA, 1994). This standard is relevant for the
comparison of exposure of rescue and other workers at the WTC site with current workplace
standards. EPA also collected air samples analyzed for fibers by the PCM method that may be
used for this purpose.
IV.e.3. Background Air Concentrations for Asbestos
ATSDR's Toxicological Profile for Asbestos (ATSDR, 1999) provides a summary of
background asbestos levels. Because the health effects data regarding inhalation exposure to
asbestos are usually expressed in terms of PCM f/cc, ATSDR chose to convert ambient air data
reported in units of ng/m3 or TEM f/cc to units of PCM f/cc. ATSDR's summary included these
crude assumptions: 1 PCM f/cc is equal to 60 TEM f/cc and also approximately equivalent to a
mass concentration of 30,000 ng/m3. (Note, however, that there was not sufficient analysis
available for this current report to suggest applying these factors to asbestos measurement data
for the WTC data.)
On this basis, the following summaries are excerpted from the profile (specific references
supplied in ATSDR, 1999). It should be noted that these "background" data are derived from
settings where no identified asbestos materials are present, as well as other settings, such as
buildings containing asbestos materials where there may have been some local releases.
Data from several studies indicate that in urban areas, most ambient air concentrations
range from 3*10"6 to 3*10"4 PCM f/cc, but they may range up to 3*10"3 PCM f/cc as a result
of local sources. In another investigation, the median concentration in U.S. cities has been
estimated to be 7*10"5 PCM f/cc.
A recent analysis of monitoring data for asbestos in ambient air worldwide estimated rural
and urban levels at about 1*10"5 TEM f/cc (2*10"7 PCM f/cc) and 1*10"4 TEM f/cc (2*10"6
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PCM f/cc), respectively.
In a review of indoor air monitoring data from a variety of locations, arithmetic mean
concentrations ranged from 3*10"5 to 7*10"3 PCM f/cc. Levels of asbestos in 94 public
buildings that contained asbestos ranged from ND to 0.2 TEM f/cc (ND to 3*10-3 PCM
f/cc), with an arithmetic mean concentration of 0.006 TEM f/cc (10-4 PCM f/cc). Analysis
of data based on air samples from 198 buildings with asbestos-containing materials (ACM)
indicated mean asbestos levels ranging from 4*10"5to 2.43 *10"3 TEM f/cc (7*10"7 to 4*10"5
PCM f/cc).
Asbestos concentrations in 41 schools that contained asbestos ranged from ND to 0.1 TEM
f/cc (ND to 2*10"3 PCM f/cc), with an arithmetic mean of 0.03 TEM f/cc (5*10"4 PCM
f/cc). Another study reported average concentrations of airborne asbestos fibers > 5 |im in
length of 8*10"5 TEM f/cc and 2.2* 10"4 TEM f/cc in 43 non-school buildings and 73 school
buildings, respectively (the 60:1 conversion factors would not apply to these data, since the
TEM readings were already on fibers >5 |im in width, so they are likely to be more directly
comparable to PCM results). In another study in 71 U.S. schools, the mean, the 95
percentile, and the maximum asbestos levels were 1.7* 10"4, 1.4*10"3, and 2.3*10"3 PCM
f/cc, respectively.
A study of 49 buildings in the United States reported mean asbestos fiber levels of 9.9*10"
4 PCM f/cc in buildings with no ACM, 5.9* 10"4 PCM f/cc in buildings with ACM in good
condition, and 7.3 *10"4 PCM f/cc in buildings with damaged ACM.
In general, concentrations of asbestos in both indoor and outdoor settings and in both rural
and urban settings appears to be less than, and by some studies, sometimes substantially less
than, 3*10"3 f/cc on a PCM volumetric basis.
IV.e.4. Asbestos Air Monitoring Data at the WTC
Three sources of information were used to evaluate the asbestos air monitoring. One was
the EPA WTC database itself. Downloads of this database occurred in May of 2002, and the
data evaluated are current as of about mid-April, 2002. The WTC database includes
measurements by several federal, state, and local agencies. The second source of data was the
Trends Report dated May 16, 2002 (EPA, 2002a). There have been three Trend Reports.
Generally, these reports obtain all their data from the EPA WTC database and provide
summaries and interpretative analyses. The third source of data is a study commissioned by a
"Ground Zero Elected Officials Task Force" to principally sample two apartments on September
18, 2001 (Chatfield and Kominsky, 2001). While the focus of that study was on the indoor
environment (it is reviewed in more detail in Section V), two outdoor air samples were also
taken.
The May Trends Report contains a summary of the PCM and TEM data collected between
September 12, 2001 (the date of the first reported sample), and April 13, 2002, in the lower
Manhattan area in the vicinity of Ground Zero. Additional TEM data from the Staten Island
Landfill were obtained directly from the Region 2 WTC database. Figures 23 and 24 show the
locations of fixed monitors at the Lower Manhattan and Staten Island Landfill areas,
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respectively. A few more stations were set up in public schools (Manhattan - PS 143, Queens -
PS 199, Brooklyn - PS274, Bronx - PS 154, and Staten Island - PS44), and New Jersey (4
locations). There were over 600 samples taken in these public schools. Nearly all the samples
were non-detected, with only one high reading of 93.3 S/mm2 in PS199 in Queens on October
12, 2001, and 2 other low readings (< 20 S/mm2). Over 100 samples were reported for the New
Jersey locations through early December of 2001. Nearly all readings were non-detect with a
few low measurements (< 20 S/mm2).
On the basis of these findings, there does not appear to be any significant concern for a
health impact at these Brooklyn, upper Manhattan, and New Jersey locations, and they are not
discussed further.
The latest trends report (EPA, 2002a) summarizes the results of 8,870 samples taken from
lower Manhattan and measured for TEM (locations in Figure 23). Samples taken during the time
period between September 14 (the date of the first asbestos sample taken) and September 30
showed generally the highest concentrations. Table 6 lists the TEM measurements above 70
S/mm2, and, as shown, more readings above this level were found for September (11 readings)
than for any other month: October (2), November (1), December (1), January (1), February (2),
March (3), and April (1).
The Trends Report also presents a directional analysis that supports this general
observation in most cases. For this directional analysis, a subset of the sites was selected to
represent the north, south, east, west, northeast, northwest, southeast, and southwest quadrants.
Two-week maximums were then identified for each of these sites. These two maximums were
plotted on 3-d graphs for N-S, E-W, NE-SW, and NW-SE. These graphs are duplicated in
Figures 25 - 28 for TEM. The N-S graph in Figure 25, for example, shows that most of the
samplers had their highest 2-week maximums during the first 2-week period identified,
September 16 to September 30. Some samplers did have additional elevations later in time, such
as Albany and Greenwich, which had a high reading of 204 S/mm2 in December (from Figure 25
and also listed in Table 6).
The same general observation that early readings were the highest is seen in the NE-SW
graph of Figure 28. These two graphs also do not exhibit a predominant wind direction: high
measurements of the same magnitude were found on both the N and S sides (Figure 25) and the
NE and SW sides (Figure 28). Figures 26 and 27, on W-E and NW-SE, do not show the same
predominant elevations in September; concentrations are mostly level throughout time, with
occasional elevated readings, such as a reading of 213 S/mm3 in February, 2002, at Church &
Dey (from Figure 26 and Table 6). It does appear that during 2002, most readings were at what
appears to be background for the area, at nondetect or reported at less than 20 S/mm2.
A number of samples at the Staten Islands Landfill recorded higher levels than the AHERA
standard. This presumably results from WTC debris being unloaded at this location, which
causes the asbestos structures to become airborne. The WTC database listed 5207 measurements
in numerous Staten Islands Landfill sites (see Figure 24), and 50 samples were identified as
above 70 S/mm2. These are listed in Table 6. Unlike the air monitors near Ground Zero, which
showed the most elevations in September, the most elevations in the landfills occurred fairly
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uniformly in October and November. This was perhaps a time period of most rigorous
unloading. Of the 50 readings above 70 S/mm2, 36 occurred during these two months. The
highest level of 275.56 S/mm2 was observed on November 5, 2001.
The Trends Report (EPA, 2002a) summarizes the results of 12,674 ambient samples
measured for PCM, of which 8870 were also measured for TEM. Figures 29 - 32 show the
directional analysis results for PCM. It is noted that all samples were less than 0.1 f/cc. The
trend observed above for TEM, that most high readings were found in the early readings in
September, holds as well for PCM. The range of these higher measurements is about 0.04 to
0.08 f/cc, and only 7 measurements in this range are seen in Figures 29 - 32. As noted above,
PCM analyses identify the presence of fibers, including fibers of materials other than asbestos.
By December, the maximum 2-week readings were all at apparent background for the area.
With a few isolated exceptions, levels ranging from non detect to about 0.003 f/cc had been
observed from lower Manhattan sampling sites since February, 2002 (EPA, 2002a). This
background is consistent with the background measurements in other locations summarized
above.
Chatfield and Kominsky (2001) describe the sampling of two apartments one week after
September 11, on September 18. In addition to sampling of indoor air and dust (described in
Section V), and some outdoor dust, two samples of outdoor air were also sampled. One was at a
residential dwelling characterized as "high", so named due to the expectation that higher
concentrations would be measured within it. It was in an apartment building located on 250
South End Avenue, close to and southwest of Ground Zero. Apartment 10D, on the east side of
this building and which had sustained window damage, was selected for sampling. Heavy dust
deposits were in the apartment. One air sample at this site was taken by positioning the sampler
outside a sliding window. The concentration of chrysotile asbestos (S > 0.5 jam) was 548
S/mm2, which is the highest outdoor air measurement found. However, it is likely this high
reading was influenced by the air quality on the inside of the apartment, which showed
exceedingly high asbestos concentrations (>10,000 S/mm3; see the discussion on this study in
Section VI. Data on Occupational and Indoor Exposures), and was likely not representative of
outdoor concentrations. The "low" location was located four blocks north on 45 Warren Street.
The apartment building did not appear to sustain any external damage. Apartments on the
second and fifth floors were sampled. A sample taken on the roof above the fifth floor apartment
showed a reading of 6.5 S/mm2 chrysotile asbestos.
IV.e.5. Human Health Evaluation of Asbestos Air Measurements
Only 22 of 8870 TEM measurements in lower Manhattan from EPA's WTC data base
exceeded the AHERA standard of 70 S/mm2, and one additional sample (of two taken) from an
independent study exceeded the standard. The 12 exceedences, which occurred in September,
were all at sites bordering Ground Zero: 250 South End Ave., Barclay & West Broadway,
Albany & Greenwich, Liberty & South End, Vesey & West, and Albany & West. These sites
were still in the restricted zone during September. The same general trend can be seen with the
PCM data. Measurements near to or greater than 0.04 f/cc occurred mostly in September (6 of 7
samples during September, with 1 high sample during the first two weeks in October) and at sites
bordering Ground Zero: Broadway & Liberty, Rector & South End, Albany & West, West
Broadway & Barclay, Wall & Broadway, Albany & Greenwich, and Liberty & South End. It is
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reasonable to conclude that general population exposures to ambient levels of asbestos were
minimal and potential short- and long-term health impacts were minimal during the early weeks
when a small percent of elevated measurements of asbestos were reported.
The potential for exposure appeared to be somewhat greater at the Staten Island Landfill.
A total of 50 samples exceeded the AHERA standard of 70 S/mm2, with most exceedences
occurring during October and November. The average of the 36 exceedences during October
and November was 92.6 S/mm2. Exceedences in February through April of 2002 were likely
due to the continued unloading of WTC debris. Assuming the crude TEM to PCM conversion
factor of 1/60 used by ATSDR and the TEM surface area to volume conversion factor of 3*10"4
[f/cc]/[S/mm2], then this converts to a PCM-equivalent concentration of 0.0005 f/cc. This is
significantly lower than the OSHA PEL of 0.1 f/cc. It is reasonable to conclude that the
exposure of workers to asbestos at the Staten Island Landfill was minimal and potential short-
and long-term health impacts were minimal during the unloading of debris at the site.
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Table 6. Locations and concentrations of asbestos exceeding the AHERA level of 70 S/mm2.
Location
Date
Concen-
tre ti nn
Date
Cone
I. Landfill Locations




Location 01 Landfill
Apr 27
125.98


Location 02 Landfill
Mar 23
170.6


Location 05 Landfill
Mar 14
78.74


Location 08 Landfill
Nov 5
112


Location 09-A Landfill
Oct. 8
71.11
Nov 5
71.11

Oct 25
128
Nov 11
120.0

Oct 25
128


Location 09-B Landfill
Oct 18
96.24
Nov 5
71.11 |
Location 09-C Landfill
Oct 17
97.78


Location 10-A Landfill
Nov 7
80


Location 11 Landfill
Oct 18
96.24
Feb 6
110.24

Nov 6
80
Feb 7
170.6

Nov 7
88.89
Feb 15
78.74

Nov 17
80
Feb 16
78.74
Location 12a Landfill
Oct 8
88
Nov 12
80

Oct 16
124.44
Nov 13
72

Oct 18
96.24
Nov 20
71.11

Oct 20
80
Jan 11
166.23

Oct 31
115.56
Mar 21
157.48

Nov 5
275.56
Mar 23
125.98

Nov 11
195.56
Apr 20
104.99
Location 12b Landfill
Oct 25
115.56
Nov 5
106.67
Location 13 Landfill
Oct 15
80
Nov 13
97.78

Oct 25
88.89


Location 14 Landfill
Oct 17
80
Dec 11
104.99

Oct 26
88.89
Dec 11
104.99

Nov 7
80
Apr 3
91.86
Location 15 Landfill (mess tent)
Nov 6
90
Nov 18
97.78
Location 16 Landfill (suddIv tent)
Oct 20
72
Nov 9
80
II. Lower Manhattan Locations




250 South End Avenue3
Sep 18
548


Location A - Barclay St & West
Sep 15
128
Sep 15
160
Broadway




Location B - Church St & Dey St
Feb 11
213.33


Location C - Liberty St & Trinity St
Feb 5
88


Location D - Albany St & Greenwich
Sep 27
97.78
Dec 27
204.44 |
St
Sep 30
88.88


Location E - Liberty St & South End
Sep 16
90
Sep 30
80
Ave




Location F - Vesev St & West St
Sep 27
71.11
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Table 6. Locations and concentrations of asbestos exceeding the AHERA level of 70 S/mm2 (cont'd).
Description
Date
Cone
Date
Cone
Location K - Albany & West St
Sep 22
80
Sep 27
177.78
Sep 23
88.89
Sep 30
71.11
Location L - North Side of Stuyvesant
High
Nov 28
124.44


Location V - Pier 6 Bus Sign
Jan 14
72


Wash Tent - West St. Between
Murray & Vesey
Mar 9
144
Mar 30
96
Mar 29
96
Apr 2
80
Site 2 - Chambers Street
Oct 9
104.99


Public School 199 in Queens
Oct 12
93.33


a This sample was reported on in Chatfield and Kominsky (2001); all other data was from the
EPA WTC data base. See text for more detail.
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SEPA
Figure 23. Location of asbestos monitoring stations in Lower Manhattan.
Harrison & West
EPATaga 3as —-L
	I J,Vi
j-cjgric' Vj-m-jiCcTTj-; y Cc *g? I
Siuyvasant H;gn Schao'
Chcrch&tXiana
W.0madwajf & Barclay
Pica Ortvarssy P^aza
Aibany & Graa™-c!n
HscSarSc j?i End
Waii & 3-aadvray
C-iasa Waitaran Piaia
CaasiGuand SaSaty flarii.
EnviroMapper
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Figure 24. Location of Asbestos monitoring stations in Staten Island and nearby locations in
New Jersey (note: sampling sites in the Staten Island Landfill identified only by number).
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Asbestos TEM - Weekly Maximums
North - South Axis
M/UWOf-OG
IDQMDMi
01/20*1?
0
Figure 25. North-South
directional analysis for asbestos
TEM weekly maximums (taken
from EPA, 2002a).
Week
Ft. North • P«ir25
	Ft. North • Harrison & West
. Ft. North • EPATaga 9u$
	North • &uyv«anc High School
- Ft. North - Manhattan College
- North • Vton?n S West
Ft North - Wist & Barctay
W Ft. North • \teay S Wfest
	A Zero ¦ WJC
Ft. South • Afijany S Gre enrich
Ft. Souh • Wail & firei&ray
3960 Ft. Soi*h ¦ Coast Guard Battery Parte
Asbestos TEM - Weekly Maximums
East-West Axis
-------
Asbestos TEM - Weekly Maximums
Northwest - Southeast Axis
Owl OA) 1-09
HV2MH.11/
SE
12j©M>M2ft
O1/2Ofl)2-02/tr
Week 03/D34D2-0
3740 Ft. SE - Pier 6 Heliport
'3030 Ft. SE - Pier 6 Beit 2
'3520 Ft. SE • Pier 0 Bus Sign
1700 Ft. SE - Chase iwbnhanan
100 Ft. SE - Broadway 8. Liberty
"Ground Zen - WTC
NW
Figure 27. Northwest-
Southeast directional
analysis for asbestos TEM
weekly maximums (taken
from EPA, 2002a).
Asbestos TEM
Northeast-
Weekly Maximums
Southwest Axis
(M
E
E
(A
NE
Figure 28. Northeast-
Southwest directional
analysis for asbestos TEM
weekly maximums (taken
from EPA, 2002a).
12A34MDI-I2J
01/20/02-02?
Week 03/D3/D2-037T
2200 Ft, NE - Church 5 Duane
'000 Ft. NE - West Broadway 8 Barclay
Ground Zero WTC
~1100 Ft. SW - Kbany & West
1210 Ft, SW • Albany & South End
"1S40 Ft. SW - RectorS South Bid
SW
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Fibers PCM - Weekly Maximums
North - South Axis
0.08
0.07
OiW
0.05
044
0-03
0.02
0.01
0

i


-¦

-
if







N
10/28/Dt-TT
12MDM&
01/20/02^
Week**u**n
—r 3520 ft M - Pier 2$
^2070 ft N • Harrison & Weji
^ 2750 ft N - EPA Taga Bus
^ 2530 f N - Stuyv«sar* High School
„	c3/t2-037Y
ft E- ParV Row
.50 ft E ¦ Church & Dey
'Ground Zero - WTC
)00 ft W - Liberty & South &d
Figure 30. East-West
directional analysis for
asbestos TEM weekly
maximums (taken from
EPA, 2002a)
W
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Fibers PCM - Weekly Maximums
Northwest - Southeast Axis
SE
12/D®j0M272
01/20/02-02X)
Wee^3^-olt
3740 Ft. SE - Pier 6 HeBport
Ft. SE- Rer6 Exit 2
Ft. SE - Pier6 Bus Sign
Ft. SE • Chase Manhattan
Ft. SE - Broadway & Liberty
Ground Z#ro - WTC
NW
Figure 31. Northwest-Southeast
directional analysis for asbestos
TEM weekly maximums (taken
from EPA, 2002a).
Fibers PCM - Weekly Maximums
Northeast- Southwest Axis
NE
Figure 32. Northeast-
Southwest directional analysis
for asbestos TEM weekly
maximums (taken from EPA,
2002a).
01/20/02-02)tr
Week 034)3,02-03?
Ft. NE - Ctartb & Duant
Ft. NE - Wen Broadway & Barclay
I Zero -WTC
^	Ft. SW • Abany & West
1210 Ft. SW- Atony S South B-vJ
Ft. SW - Rtctor & Sooth ErxJ
SW
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IV.f. Volatile Organic Compounds (VOCs)
VOCs are carbon compounds that exist exclusively in the gaseous phase in the ambient
environment and include benzene, toluene, chloromethane, ethylbenzene, acetone, and styrene.
VOCs have been associated with a variety of health effects, including immunologic, hematotoxic
and neurologic effects; chromosomal damage; and cancer. VOCs are produced as a result of
combustion of products containing carbon, such as plastics, wood, paper, carpeting, gasoline,
and jet fuel. Thus, they would have been produced as a result of the WTC disaster.
Analysis of all VOCs released at the World Trade Center would require evaluating
hundreds of different compounds. The list was narrowed down by emergency response
personnel, representatives from EPA headquarters, EPA Region 2, NYSDEC, and NYSDOH.
In this assessment, data for 14 VOCs were examined and screened, including acetone, benzene,
1,3 butadiene, chloromethane, 1,4 dioxane, ethanol, ethylbenzene, freon-22, methyl styrene,
propylene, styrene, tetrahydrofuran, toluene, and xylenes. These VOCs were chosen on the basis
of frequency of detection, concentration, toxicity, and carcinogenicity. Two of these 14 VOCs,
freon-22 and methyl styrene, were not systematically measured outside of Ground Zero. Freon-
22 was measured only at the WTC Chiller Plant and methyl styrene was only measured at
Ground Zero. For this reason, freon-22 and methyl styrene are not evaluated in this report.
Additionally, because no screening standards are available for propylene, a health assessment
cannot be conducted for this chemical. Therefore, a total of eleven VOCs were evaluated for this
report.
To evaluate the VOC exposures, a variety of screening benchmarks were used, including
OSHA PELS and STELS, ATSDR acute and intermediate inhalation MRLs, and EPA Superfund
Technical Support Center (STSC) provisional subchronic RfCs. If none of these benchmarks
were available, the American Conference of Governmental Industrial Hygienists (ACGIH)
Threshold Limit Values (TLVs) for an 8-hour exposure and the NIOSH RELS were used. The
goal of this assessment was to evaluate effects due to short-term exposure, thus screening tools
that are based upon lifetime exposures to a chemical (i.e. EPA RfC values or ATSDR chronic
MRLs) were not used.
IV.f.l. Evaluation of VOCs at Ground Zero
The majority of the EPA data collected for VOCs were within Ground Zero (North Tower
Center, South Tower Center, and Austin Tobin Plaza) and nearby locations. For example, for
acetone, benzene, ethylbenzene, and 1,3 butadiene, more than 500 samples were taken in the
restricted zone near and within Ground Zero, where authorized personnel were directed to wear
respirators. The majority of the measurements taken were grab samples that were usually
collected within a 4-minute period. Samples at North Tower Center and South Tower Center
were taken in potential hot spot areas such as plumes, areas of fire and combustion, and steam
releases. The efforts at these two locations were subjective and were intended to capture
potential worst case emissions. Samples at Austin Tobin Plaza were taken at a breathing zone
height, but were still grab samples and were not purposively where workers were currently
working, but where they might work or where there was visible smoke to contend with. Thus,
collected samples at the three sites cannot be considered representative of the general air quality
to which workers were exposed. Rather, the principal purpose of the EPA sampling at Ground
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Zero was to provide results within four hours to alert the Fire Department of New York (FDNY)
and the contractors/union health/safety officers working at Ground Zero about conditions that
posed immediate health concern to the workers. This sampling was specifically requested by the
FDNY and was conducted on a daily basis until the removal activities were completed at Ground
Zero (end of May 2002).
As would be expected given this intention, some of the results (including data for benzene,
1,3-butadiene, and styrene) did show exceedences of OSHA limits. A few samples clearly
demonstrated exceptionally high measurements of VOCs produced as a result of the disaster.
Some samples were collected on top of, and at times, inside the actual debris pile, clearly
demonstrating subjective sample design. Because the VOC sampling at the site is not believed
to be representative of actual exposures to personnel, it would not be appropriate, or valid, to use
these VOC sampling data to analyze worker exposures.
OSHA collected approximately 700 samples for organic compounds, as described in
Chapter VI. Most of these samples were taken using personal air monitors, and the samples
were taken over longer periods (one to eight hours) and are representative of a worker's
breathing zone exposure. As described in Chapter VI, the OSHA data did not show routine
exceedences of screening values (the OSHA standards). For that reason, WTC worker exposures
will not be evaluated further. Instead, sampling data that were collected at sites surrounding the
WTC site were used to evaluate potential health risks to persons who live or work in surrounding
areas.
IV.f.2. Evaluation of VOCs at Sites Surrounding Ground Zero
The EPA WTC monitoring database and data from EPA-ORD monitors were used to
evaluate VOC exposures to persons who may live and work in areas surrounding the WTC site.
Most of the data in the WTC monitoring database are from EPA sampling, but data from other
groups (e.g., NYSDEC, OENHP) are also included. Data from the WTC monitoring database
covered approximately 27 locations and the EPA-ORD monitors covered 5 locations.
A map of the VOC sampling locations outside of Ground Zero is shown in Figure 33.
Table 7 lists the site name, street address, approximate dates of sampling and the approximate
number of samples that were taken. Because the number and dates of sampling varied
depending on the VOC, the sample dates and number of samples taken shown in the table are for
benzene monitoring only. These numbers are, in general, representative of the dates and
frequency of sampling of the other VOCs.
Exceedences of benchmark standards were seen for 6 of the 11 VOC compounds evaluated
in this assessment, including acetone, benzene, 1,3-butadiene, chloromethane, ethylbenzene, and
toluene. 1,4 Dioxane, ethanol, styrene, tetrahydrofuran, and xylenes showed no exceedences of
screening benchmarks at any of the sampling sites and are therefore not considered to be
contaminants of concern at sites surrounding Ground Zero. Table 8 lists the sites that showed
exceedences of screening benchmarks, the dates of exceedence, and the location of the site in
relation to the restricted zone. Tables 9-14 show the exceedences of these 6 VOC compounds.
For 5 of these 6 VOC compounds, data were also available for 24-hour samples taken by
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EPA; 24-hour samples were not available for chloromethane. These 24-hour sample results are
also provided in Tables 9, 10, 11, 13, and 14 to compare with the exceedences (Table 12 is
chloromethane).
Chemical-by-chemical summaries of the 6 VOCs that exceeded benchmarks are presented
below.
Acetone: Most people are exposed to acetone through consumer product use, including nail
polish remover, particle board, and paint removers. Acetone exposure may also occur as a by-
product of exposure to isopropyl alcohol. The typical level of acetone in the air in cities in the
United States is about 0.007 ppm (ATSDR, 1994). Acute exposure to acetone at levels above
100 ppm may cause irritation to the nose, throat, lungs, and eyes (ATSDR, 1994).
A total of 264 acetone monitoring results were evaluated at sites surrounding Ground Zero.
A summary of the screening benchmarks and exceedences is shown in Table 9. All three
exceedences were seen at Greenwich and Liberty. Two of the exceedences were on September
28, where grab samples found concentrations of 29 ppm and 22 ppm. On October 1, a
concentration of 20 ppm was detected. The other 12 samples taken at Greenwich and Liberty did
not show concentrations above 13 ppm, including the samples taken on September 26 and
September 27, as well as October 2, October 3, and February 23.
The monitoring data indicate that the acetone level was found to elevated above a typical
background (0.007 ppm as noted above) in grab samples for 4 days only on the end of September
and beginning of October just off the southern portion of Ground Zero. Because this would
correspond to an acute exposure, the ATSDR acute MRL screening value of 26 ppm (ATSDR,
1994) is most appropriate. This value was only slightly exceeded in one sample on 1 day (29
ppm). The Greenwich and Liberty sampler location was in the restricted zone at the time of the
exceedence and it was unlikely that residents would be present in that area.
Twenty-four hour samples were taken on September 27 and for three days in December.
As seen in Table 9, these locations bordered Ground Zero and the day-long concentration was
nearly 4 orders of magnitude (10,000 times) lower than the grab samples, and well within the
range of the cited typical background of 0.007 ppm. This clearly demonstrates that sampling
within a "hot spot" can result in very high concentrations that are representative of only the few
minutes during which the grab sample is taken .
Benzene: Benzene is widely used in the production of other chemicals. It is also found in
crude oil, gasoline, and cigarette smoke. Excluding occupational exposures, the major sources
of benzene exposure are tobacco smoke, automobile service stations, automobile exhaust, and
industrial emissions. Urban air concentrations of benzene can vary widely, depending on mobile
source pollution. One large urban study (ATSDR, 1997a) detected a median benzene level of
0.013 ppm. Background concentrations reported by EPA Region 2 for benzene are 0.00051 ppm
and 0.00053 ppm (annual averages of Brooklyn and Staten Island locations, respectively, over
the period 1994 - 98; EPA, 2002b).
Breathing levels of benzene above 100 ppm can cause drowsiness, dizziness, and
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unconsciousness. Long-term continued exposures to benzene will depress and may cause
damage to the blood-forming system, as seen by a decrease in red and white blood cells,
lymphocytes, platelets, and other blood constituents. However, after exposure has ended, red
blood cell levels may return to normal. Benzene can also harm the immune system and increase
the chances of infection and cancer. Benzene is a known human carcinogen, causing leukemia.
Most of what is known about the acute and chronic effects of benzene comes from animal and
human studies where decreases in bone marrow function have been measured. The intermediate
MRL, 0.004 ppm, was derived from a study in mice, where changes in locomotor activity were
seen after exposure to 0.78 ppm benzene for 2 hours a day for 30 days. A 100-fold uncertainty
factor was used to derive the intermediate MRL (ATSDR, 1997a).
A total of 332 benzene monitoring results were evaluated at sites surrounding Ground
Zero. A summary of the screening benchmarks and exceedences is shown in Table 10.
According to sampling notes for other VOCs with the same sample number, all these samples
were taken at ground level, and the October 1 measurement was taken at ground level in a
plume. Nine measurements taken at Greenwich and Liberty between September 16 and
September 26, and on October 2 and October 3, were at levels below 0.02 ppm. From these data,
it appears that exceedences did not last more than 5 days. Furthermore, these exceedences all
occurred within the restricted zone. At Liberty and Trinity, the exceedence detected was 11 ppm
on September 26. According to sampling notes for other VOCs with the same sample number,
this measurement was taken at ground level in a plume. Measurements taken on September 16,
September 22, September 23, and on October 26 did not show exceedences.
From these data, it appears that the exceedence did not last longer than 32 days and
throughout this period was in a restricted zone. Because previous sampling did not show
exceedences, it is likely that the measurement was taken deliberately in a plume to represent a
worst-case transient exposure.
For the 262 samples recorded in the WTC EPA database for sites surrounding Ground
Zero, the minimal detection limit was 0.02 ppm, as compared to the ATSDR intermediate MRL
of 0.004 ppm (ATSDR, 1997a). This means that the analytical method could not detect benzene
contamination levels below 0.02 ppm. Therefore, one cannot evaluate whether or not the
ATSDR intermediate MRL was exceeded because the detection level for the samples was higher
than the intermediate MRL. Five samples exceeded the ATSDR acute MRL of 0.05 ppm
(ATSDR, 1997a), and these are shown in Table 10. Four samples had values above 0.02 ppm
but below the 0.05 ppm level. The rest of the samples in the EPA WTC database were reported
to be 0.02 ppm. These values are not reported above. Sample results reported to be below 0.05
ppm (257 sampling results) were not screened against the intermediate MRL.
Results from the 70 EPA-ORD samples show that the OSHA PEL and STEL values for
benzene were never exceeded. Since these EPA-ORD samples did have a lower detection than
the samples reported on in the WTC EPA database, they could be compared against the ATSDR
intermediate MRL of 0.004 ppm. It was found that the ATSDR acute and intermediate MRL
values were exceeded a total of 17 times at 4 different sampling sites. At West Broadway and
Park Place, 10 samples were taken between November 9, 2001, and January 3, 2002. They
showed benzene levels to be below the intermediate MRL. Additionally, exceedences at West
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Broadway and Park Place were not found on October 15, October 16, October 17, and October
22 (the highest value was only 0.002 ppm). The range of sampling results (0.002 to 0.026 ppm)
shows the temporal variability in the benzene levels. At 290 Broadway from November 26
through January 3, 10 samples were taken. They showed benzene levels to be below the
intermediate MRL. At Broadway and Liberty, the sample taken on October 17, the only sample
taken after the exceedence on October 8, was below the intermediate MRL at 0.0009 ppm. At
Albany and West, 16 samples were taken between October 22 and January 3. They showed the
benzene levels to be below the intermediate MRL.
Monitoring results from the EPA-ORD sampling suggest that benzene never exceeded
screening benchmarks for more than 45 days. At all the sites there was great temporal variability
in the samples. The largest gap between an exceedence of the intermediate MRL and a value
below the MRL was only 11 days at West Broadway and Park Place. For 290 Broadway,
Broadway and Liberty, and Albany and West, the first samples below screening benchmarks
were taken November 26, September 22, and September 23, respectively. If one assumes that
exposures began September 11, the worst case exceedences of the intermediate MRL could not
have lasted longer than 45, 8, and 18 days, respectively, at 290 Broadway, Broadway and
Liberty, and Albany and West. Thus the worst-case, longest possible exposure, would have been
45 days at 290 Broadway.
On the basis of data summarized above, it is concluded that the exceedences measured at
Liberty and Trinity, Greenwich and Liberty, W. Broadway and Park Place, Broadway and
Liberty and Albany and West were not a public health risk to residents. These sites were in the
restricted zone or on the border of the zone, and it is unlikely that residential exposures occurred
for extended periods. The samples taken were grab samples (taken within a 4 minute period) and
are not representative of the average exposures. Samples taken at Liberty and Trinity and
Greenwich and Liberty were purposefully taken at ground level and/or in a plume and are not
representative of average breathing zone exposures. The temporal variability of the other
samples, as shown by exceedences intermixed between days that were below screening
benchmarks, also leads to the conclusion that exceedences of the Intermediate MRL were not
sustained for extended periods of time. For exposures lasting less than 14 days, the acute MRL
is a more appropriate health screening benchmark, and this value was not exceeded at these sites.
At 290 Broadway, elevated measurements were found as late as October 11 (see Table 10)
and exposures could have occurred, as the measurement was taken in a non-restricted zone. In a
worst-case scenario, the longest possible exposure would have been 45 days at this site. At this
site, measurements were taken on a 16th floor balcony. Whether or not the VOC samples
collected at this site are representative of the breathing zone exposures will depend on the
meteorology and air mixing at the site. The highest benzene value measured at this site was
0.007 ppm and the intermediate MRL is 0.004 ppm (ATSDR, 1997a). Adverse effects would not
be expected at 0.004 ppm, and it is unlikely that adverse effects would occur at 0.007 ppm.
The 24-hour samples are mostly lower than all the grab sample exceedences; only the
finding of 0.005 ppm at Church and Dey on September 28 approached the grab samples listed as
exceeding the ATSDR Intermediate MRL of 0.004 ppm. This Church and Dey location is on the
edge of Ground Zero which was also restricted on September 28. In the northwest direction on
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September 28, at the Vesey and West and the EPA Taga Bus locations showed a very low 24-
hour concentration, 0.00081 at Vesey and West and ND at EPA Taga Bus. This demonstrates
that concentrations were likely higher in the general direction of plume movement, which on
September 28 was likely in the east direction.
Of all the VOC data, the benzene data does suggest that sustained concentrations above the
typical New York City background could have occurred for about a month after September 11
outside of Ground Zero. As noted above, the background concentration reported by EPA Region
2 for benzene is about 0.0005 ppm. Four of the nine 24-hour measurements taken on September
28 exceeded this background. The grab sample exceedences were substantially higher than this
background, and there were several exceedences above the ATSDR Intermediate MRL of 0.004
ppm. Whether or not specific health effects occurred due to exposure to benzene is unknown,
but given that the exceedences and elevations above typical background were near Ground Zero
and mostly within restricted zones, the data suggests that exposures to the general population
were of minimal concern.
1,3-Butadiene: 1,3-Butadiene is found in automobile exhaust, wood smoke, and cigarette
smoke, and in the breakdown of other materials. 1,3-Butadiene is almost always found at low
levels in urban air samples, but it breaks down very quickly. In sunny weather, the half-life of
1,3-butadiene is only 2 hours. The median concentration of 1,3-butadiene in urban air has been
estimated at approximately 0.0003 ppm (ATSDR, 1993).
A total of 304 1,3-butadiene monitoring results were evaluated at sites surrounding Ground
Zero. A summary of the available screening benchmarks and exceedences is shown in Table 11.
One exceedence of the 1.0 ppm PEL was detected in a ground-level plume on October 1, at 1.5
ppm. On days preceding and following October 1 the levels of 1,3-butadiene measured at this
location were below the screening benchmark; in fact, 10 of the 12 samples taken at this location
were at 0.002 ppm.
All 24-hour samples were non-detects for 1,3-butadiene.
Chloromethane: Chloromethane is always present in the air at very low levels. Most of the
naturally occurring chloromethane comes from chemical reactions that occur in the oceans or
that occur when materials such as grass, wood, charcoal, and coal are burned. Reported urban
levels of chloromethane have been between 0.00066 and 0.00096 ppm (ATSDR, 1998). The
background concentration reported by EPA Region 2 for chloromethane is approximately
0.00029 ppm (the annual average for a Staten Island location for the period 1995-1999; EPA,
2002b).
High-level exposures - above 100 ppm - to chloromethane can cause nervous system
damage and adversely affect the liver, kidney, and heart. Lower-level exposures - above 50 ppm
- have been shown to cause delayed growth, liver changes, and neurological effects in animals.
Data do not exist to determine health effects that would be seen with short-term, very low-level
exposures. The EPA-STSC provisional subchronic RfC, the screening benchmark with the
lowest acceptable exposure limit, is based on a 2-year animal study that showed neurological
effects and liver and kidney damage at 1000 ppm but not at 225 ppm (EPA, 1998).
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A total of 257 chloromethane monitoring results were evaluated at sites surrounding
Ground Zero. A summary of the available screening benchmarks and exceedences is shown in
Table 12. As with all VOCs, all grab sample exceedences were taken in a restricted zone, and in
the time frame from late September to early October. It is noted that all of the samples that
showed exceedences at Greenwich and Liberty were taken at ground level and that the October 1
measurement was taken at ground level in a plume. Measurements taken at this site September
24 - 27 and on October 2 and 3 were all at levels below 0.02 ppm. From these data, it appears
that exceedences did not last more than 4 days. At Liberty and Trinity, the exceedence detected
was 0.82 ppm on September 26, and it was noted that this measurement was taken at ground
level in a plume. Measurements taken on September 22, September 23, and on October 26 did
not show exceedences.
Ethylbenzene: Ethylbenzene occurs naturally in petroleum and coal tar and can be released
into the air from burning oil, gas, and coal The median level of ethylbenzene in city and
suburban air is about 0.00062 ppm (ATSDR, 1999).
Breathing high levels of ethylbenzene (above 100 ppm) can cause dizziness, tightness in
the chest, and eye and throat irritation. Short-term exposure of laboratory animals to high
concentrations of ethylbenzene in air may cause liver and kidney damage, nervous system
changes, and blood changes. No data exist to evaluate the short-term effects of low levels of
ethylbenzene exposure in humans or animals. The EPA-STSC provisional subchronic RfC for
ethylbenzene is adopted directly from the EPA RfC for a lifetime exposure. The EPA-STSC
confidence level in this derivation is low. The EPA RfC is based on developmental effects seen
in female rats that were exposed to ethylbenzene throughout their pregnancy. Adverse effects in
this study were not seen at levels below 100 ppm (EPA, 1999a).
A total of 338 ethylbenzene monitoring results were evaluated at sites surrounding Ground
Zero. A summary of the available screening benchmarks and exceedences is shown in Table 13.
As with the other VOCs, exceedences occurred in the restricted zone in the latter part of
September and early October. A value of 0.4 ppm ethylbenzene was detected at Liberty and
Trinity and it was noted that this sample was taken in a ground-level plume. Three samples
obtained between September 16 and September 23 and a breathing zone sample taken on
October 26 were all below 0.05 ppm.
The 24-hour ethylbenzene samples that were detected were three orders of magnitude
(1000 times) lower than these grab sample exceedences; 10 out of 13 samples were non-detected.
This demonstrates again the difference between grab samples taken within a plume and the 24-
hour average concentration of the VOC.
Toluene: Toluene occurs naturally in crude oil and is added to gasoline. Toluene is also
used in making paints, paint thinners, fingernail polish, lacquers, and adhesives. It can also be
detected in cigarette smoke. Urban concentrations of toluene have been estimated to be around
0.003 ppm (ATSDR, 2000b). The background concentration reported by EPA Region 2 for
toluene is approximately 0.002 ppm (annual average for a Brooklyn location over the period
1994 - 1998).
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High-level exposures to toluene (above 100 ppm) may affect the nervous system and
kidneys. Headaches, confusion, and sleepiness are also seen after high-level exposures. A short-
term exposure study (4 days) in human subjects showed eye and nose irritation and neurological
effects at 100 ppm; these effects were not seen at 40 ppm. The EPA-STSC provisional
subchronic RfC for toluene is adopted directly from the EPA RfC for a lifetime exposure. The
EPA-STSC confidence in this value is medium. This value is derived from a study where
workers were exposed to 88 ppm of toluene for 6 years. In this study, adverse neurological
effects were seen in the workers (EPA, 1999b).
A total of 335 toluene monitoring results were evaluated at sites surrounding Ground Zero.
A summary of the available screening benchmarks and exceedences is shown in Table 14. The
available benchmarks that were exceeded were the ATSDR acute MRL of 1 ppm and the EPA-
STSC provisional subchronic RfC of 0.25 ppm. At Greenwich and Liberty, measurements taken
on September 28 were collected in ground-level grab samples; on October 1, the sample was
taken in a ground-level plume. Measurements taken at this site on September 16 through
September 27 and on Oct 2 and 3 were all at levels below 0.02 ppm. From these data, it appears
that exceedences did not last more than 4 days. At Liberty and Trinity, the September 26 sample
was collected in a ground level plume. Four samples obtained between September 16 and
September 23 and a breathing zone sample taken October 26 were all below 0.05 ppm.
The 24-hour toluene samples were three orders of magnitude (1000 times) lower than these
grab sample exceedences. Similar to ethylbenzene, 1,3-butadiene, and acetone, this difference in
toluene concentrations between the grab sample exceedences and the 24-hour samples
demonstrates the difference between grab samples taken within a plume and the long-term
average concentration of the VOC.
Findings from VOC monitoring: As discussed above, most of the samples that showed
exceedences were short duration grab samples that were taken in a plume or at ground level, not
in the breathing zone. In fact, the exceedences for benzene, ethylbenzene, chloromethane and
toluene measured at Liberty and Trinity on September 26, all came from the same collected grab
sample which was taken in a plume. Similarly, all the exceedences measured at Greenwich and
Liberty for acetone, 1,3-butadiene, benzene, chloromethane and toluene, came from the same 3
collected grab samples. Because these are 4-minute grab samples, it is not known how long the
plume lasted - from minutes to hours to days. These exceedences all occurred in late September
and early October; available grab sample data before and after these exceedences are all lower in
value. In addition to being grab samples, all exceedences occurred within restricted zones or just
on the border of the restricted zones. Finally, all 24-hour samples of four of the VOCs -
ethylbenzene, 1,3-butadiene, acetone, and toluene - were lower than the grab samples, by about a
factor of 1000. On the basis of the available monitoring data, it is concluded that the
exceedences of the screening benchmarks in the restricted zone did not represent a public health
risk to persons living or working at sites surrounding Ground Zero for at least these four VOCs.
The data for benzene was not as definitive. When compared with the other VOCs, the 24-
hour benzene samples were measured at levels that were closer in magnitude to the grab sample
exceedences, within a factor of 10. This would suggest that the grab sample concentrations were
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closer to sustained concentrations rather than short-term plume concentrations only. Also, these
24-hour concentrations were near the ATSDR Intermediate MRL of 0.004 ppm and higher than
the historical average for New York City of about 0.0005 ppm. The data suggests that the
exposures to benzene at levels that approach the MRL were no longer than 45 days. Whether or
not specific health effects occurred due to exposure to benzene is unknown, but given that the
exceedences and elevations above typical background were near Ground Zero and mostly within
restricted zones, the data suggests that exposures to the general population were of minimal
concern.
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Table 7. VOC sampling locations outside of Ground Zero.
Site Name
Street Location
Sampling Dates
for Benzene
Number of
Samples Taken
ORD Site A
W. Broadway & Park Place
Sept 22- Jan 3
22
ORD Site B
290 Broadway
Sept 25-Jan 3
14
ORD Site C
Broadway & Liberty
Sept 23-Oct 17
6
ORD SiteC'
Cedar & Trinity
Nov 7-Nov 12
4
ORD Site K
Albany & West
Sept 23-Jan 3
24

140 Broadway
Sept 28
6

75 Park Place & Greenwich
Sept 28
8

Albany & Washington
Sept 16
2

Church & Vessey
Feb 13
2

Greenwich & Liberty
Sept 16-Feb 23
15

Liberty & Trinity
Sept12-Sept 26
6

Liberty & West
Sept 16-Oct 5
10
Loc A
Barclay & W Broadway
Sept 22-Sept 27
3
Loc B
Church & Dey
Sept 16-Oct 10
3
Loc C
Broadway & Liberty
Sept 27
1
Loc D
Albany & Greenwich
Sept 27
1
Loc E
Liberty & South End
Sept 27
1
Loc F
Vessey & West
Sept16-Sept 27
2
LocK
Albany & West
Sept 23-Sept 25
2
Loc N
Pier 25 (southside)
Oct 13
1
Loc P
Albany & South End
Sept 27
1
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Table 7. VOC Sampling Locations Outside of Ground Zero (cont'd).
Site Name
Street Location
Sampling Dates
for Benzene
Number of
Samples Taken
Loc R
EPA TAGA Bus
Sept 23-Jan 1
11
Loc S
Rector PI & South End
Sept 27
1

Murray St & W Broadway
Oct 12-Oct 14
3

Murray St betw West & N End
Nov 5-Mar 31
134

Rockefeller Park
Sept 18-Nov 7
37

Park PI (225 Rector)
Sept 28
6

Park Row & Spruce
Oct 14
1
Site 1
(NYSDEC)
Park Row
Oct 12-Oct 13
2
Site 16
290 Broadway
Sept 25
1

130 West (Verizon Building)
Sept 29
1

South of Building 4
Sept 25
1
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Table 8. Locations that showed exceedences of screening benchmarks for VOCs and
restrictions to access.
Location
Dates of Exceedence
Restrictions to Access
West Broadway and
Park Place
Sept 22, Sept 25, Oct
3, Oct 9, Oct 19, Oct
20, Oct 21, Oct 24
in the restricted zone until Sept 27, was a
border of the restricted zone until Oct 24
290 Broadway
Sept 25, Sept 26, Sept
27, Oct 11
in the restricted zone until Sept 19
Broadway and
Liberty
Sept 23, Oct 8
in the restricted zone until Jan 28
Albany and West
Oct 1, Oct 20
was in the restricted zone until Oct 24, and
became, and still is, a border of the
restricted zone as of May 8
Liberty and Trinity
Sept 26
was in the restricted zone until Feb 12, and
became, and still is, a border of the
restricted zone as of May 8
Greenwich and
Liberty
Sept 27, Sept 28, Oct 1
still in the restricted zone as of May 8
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Table 9. Acetone grab sample exceedences and 24-hour sample monitoring summary.
I. Grab Samples
Acetone
Screening Benchmarks
Exceedence
concentration
Exceedence Location and Date
Restricted
Zone
OSHA PEL 1000 ppm1

None

AT SDR Acute MRL 26
ppm2
29 ppm
Greenwich and Liberty Sept 28
Yes
ATSDR Intermediate
MRL 13 ppm2
22 ppm
20 ppm
Greenwich and Liberty Sept 28
Greenwich and Liberty Oct 1
Yes
Yes
II. 24-Hour Samples
Location
Concentration (ppm)
Date
Albany and Greenwich
0.0064
Sep 27
Albany and South End
0.0066
Sep 27
Barclay and West Broadway
0.0071
Sep 27
Church & Dey
0.0078
Sep 27
EPA Taga Bus
0.012
0.0056
0.0040
0.0044
0.0048
Sep 27
Sep 27
Dec 3
Dec 10
Dec 17
Liberty and Broadway
0.0053
Sep 27
Liberty and South End
0.010
Sep 27
Rector and South End
0.0069
Sep 27
Vesey and West
0.0045
Sep 27
^IOSH (2002)
2 AT SDR (1994)
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Table 10. Benzene grab sample exceedences and 24-hour sample monitoring summary.

I. Grab Samples

Benzene
Exceedence

Restricted
Screening
Concentration
Exceedence Location and Date
Zone
Benchmarks



OSHA PEL 1 ppm1
11 ppm
Liberty and Trinity Sept 26-
Yes
OSHA STEL 5 ppm1
19 ppm
Greenwich and Liberty Sept 28
Yes

49 ppm
Greenwich and Liberty Sept 28
Yes

1.3 ppm
Greenwich and Liberty Oct 1
Yes
AT SDR Acute MRL
0.1 ppm
Greenwich and Liberty Sept 27
Yes
0.05 ppm2

samples noted above also exceed



the ATSDR acute MRL

ATSDR Intermediate
0.011 ppm
W. Broadway and Park PI. Sept 22
Yes
MRL 0.004 ppm2
0.024 ppm
W. Broadway and Park PI. Sept 25
Yes

0.026 ppm
W. Broadway and Park PI. Oct 3
Border

0.007 ppm
W. Broadway and Park PI. Oct 9
Border

0.012 ppm
W. Broadway and Park PI. Oct 19
Border

0.008 ppm
W. Broadway and Park PI. Oct 20
Border

0.016 ppm
W. Broadway and Park PI. Oct 21
Border

0.008 ppm
W. Broadway and Park PI. Oct 24
Border

0.005 ppm
290 Broadway Sept 25
No

0.007 ppm
290 Broadway, Sept 26
No

0.0043 ppm
290 Broadway, Sept 27
No

0.005 ppm
290 Broadway Oct 11
No

0.021 ppm
Broadway and Liberty Sept 23
Yes

0.007 ppm
Broadway and Liberty Oct 8
Yes

0.024 ppm
Albany and West Sept 30
Yes

0.008 ppm
Albany and West Oct 1
Yes

0.008 ppm
Albany and West Oct 20
Yes
II. 24-Hour Samples
Location
Concentration (ppm)
Date
Barclay and West Broadway
0.0025
Sep 27
Vesey and West
0.00081
Sep 27
Liberty and South End
<0.0007
Sep 27
Albany and South End
<0.0007
Sep 27
Rector and South End
<0.0007
Sep 27
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Table 10. Benzene grab sample exceedences and 24-hour sample monitoring summary
(cont'd).
II. 24-Hour Samples
Location
Concentration (ppm)
Date
Church and Dey
0.005
Sep 27
Liberty and Broadway
0.002
Sep 27
Albany and Greenwich
<0.0007
Sep 27
EPA Taga Lab
<0.0007
Sep 27

<0.0007
Sep 27

<0.0007
Dec 3

0.0007
Dec 10

0.0007
Dec 17
^IOSH (2002)
2ATSDR (1997)
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Table 11. 1,3-Butadiene grab sample exceedences and 24-hour sample monitoring summary.
I. Grab Samples
1,3-Butadiene
Screening
Benchmarks
Exceedence
Concentration
Exceedence Location and
Date
Restricted
Zone
OSHA PEL 1 ppm1
OSHA STEL 5 ppm1
1.5 ppm
Greenwich and Liberty Oct 1
Yes
II. 24-Hour Samples
Location
Concentration (ppm)
Date
Albany and Greenwich
<0.0028
Sep 27
Albany and South End
<0.0027
Sep 27
Barclay and West Broadway
<0.0027
Sep 27
Church & Dey
<0.0026
Sep 27
EPA Taga Bus
<0.0027
<0.0026
<0.0034
<0.0027
<0.0026
Sep 27
Sep 27
Dec 3
Dec 10
Dec 17
Liberty and Broadway
<0.0027
Sep 27
Liberty and South End
<0.0027
Sep 27
Rector and South End
<0.0027
Sep 27
Vesey and West
<0.0027
Sep 27
^IOSH (2002)
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Table 12. Chloromethane grab sample exceedences monitoring summary.
Chloromethane
Screening
Benchmarks
Exceedence
Concentration
Exceedence Location and
Date
Restricted
Zone
OSHA PEL 100 ppm1

None

AT SDR Acute MRL
0.5 ppm2
8.3 ppm
11 ppm
17 ppm
0.82 ppm
Greenwich and Liberty Sept 28
Greenwich and Liberty Sept 28
Greenwich and Liberty Oct 1
Liberty and Trinity, Sept 26
Yes
Yes
Yes
Yes
ATSDR Intermediate
MRL 0.2 ppm2

same as above

EPA-STSC Provisional
Sub chronic RfC 0.14
ppm3

same as above

^IOSH (2002)
2ATSDR (1998)
3EPA (1998)
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Table 13. Ethylbenzene grab sample exceedences and 24-hour sample monitoring summary.
I. Grab Samples
Ethylbenzene
Screening Benchmarks
Exceedence
Concentration
Exceedence Location and
Date
Restricted
Zone
OSHA PEL 100 ppm1

None

ATSDR Intermediate
MRL 1 ppm2
4.0 ppm
4.7 ppm
1.7 ppm
Liberty and Greenwich Sep 28
Liberty and Greenwich Sep 28
Liberty and Greenwich Oct 1
Yes
EPA-STSC Provisional
Subchronic RfC 0.23
ppm3
0.4 ppm
same as above
Liberty and Trinity Sept 26
Yes
II. 24-Hour Samples
Location
Concentration (ppm)
Date
Albany and Greenwich
<0.0007
Sep 27
Albany and South End
<0.0007
Sep 27
Barclay and West Broadway
0.0011
Sep 27
Church & Dey
0.0022
Sep 27
EPA Taga Bus
<0.0007
<0.0007
<0.0009
<0.0007
<0.0007
Sep 27
Sep 27
Dec 3
Dec 10
Dec 17
Liberty and Broadway
0.001
Sep 27
Liberty and South End
<0.0007
Sep 27
Rector and South End
<0.0007
Sep 27
Vesey and West
<0.0007
Sep 27
^IOSH (2002)
2ATSDR (1999)
3EPA (1999a)
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Table 14. Toluene grab sample exceedences and 24-hour sample monitoring summary.
I. Grab Samples
Toluene
Screening Benchmarks
Exceedence
Concentration
Exceedence Location and
Date
Restricted
Zone
OSHA PEL 200 ppm1

None

AT SDR Acute MRL 1
ppm2
7.5 ppm
9.0 ppm
3.7	ppm
1.8	ppm
Greenwich and Liberty Sept
28
Greenwich and Liberty Sept
28
Greenwich and Liberty Oct 1
Liberty and Trinity Sept 26
Yes
Yes
Yes
Yes
EPA-STSC Provisional
Sub chronic RfC 0.25
ppm3

same as above

II. 24-Hour Samples
Location
Concentration (ppm)
Date
Albany and Greenwich
0.0014
Sep 27
Albany and South End
0.0019
Sep 27
Barclay and West Broadway
0.0020
Sep 27
Church & Dey
0.0033
Sep 27
EPA Taga Bus
0.0009
0.0007
0.0018
0.0017
0.0015
Sep 27
Sep 27
Dec 3
Dec 10
Dec 17
Liberty and Broadway
0.0019
Sep 27
Liberty and South End
0.0014
Sep 27
Rector and South End
0.001
Sep 27
Vesey and West
0.0015
Sep 27
^IOSH (2002)
2 AT SDR (2002b)
3EPA (1999b)
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Key
18
19
20
21
22
= Rockefeller Park
= EPA Taga Bus
= Barclay & West Broadway
= Pier 25
= Murray & West Broadway
23
24
25
26
27
28
1	= Church & Dey
2	= Liberty & Trinity
3	= Broadway & Liberty
4	= 140 Broadway
5	= Cedar & Trinity
6	= Albany & Greenwich
7	= Albany & Washington
8	= Albany & West
9	= Greenwich & Liberty
10	= Liberty & West
11	= 225 Rector Place
12	= Rector & South End
13	= Albany & South End
14	= Liberty & South End
15	= Vessey & West
16	= 130 West (Verizon bldg)
17	= Murray St (between
West & North End)
= 75 Park Place & Greenwich
= Church & Vessey
= Park Row & Spruce
= Park Row
= 290 Broadway
= West Broadway and Park Place
Figure 33. Location of VOC monitoring stations outside Ground Zero.
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Section V. Comment on the First Several Days After September 11
An event such as September 11 demonstrates that the greatest environmental impacts occur
in the first 24 to 48 hours and in areas close to the site. Difficulties associated with site access
and security, power supply sources, equipment availability and analytical capacity hindered
efforts by EPA and the New York State Department of Environmental Conservation (NYSDEC)
to put air monitors in place immediately after the attack. Region 2 collected numerous samples
of dust on September 11 and the next few days, and analyzed them for asbestos and lead.
However, the first air samples of some of the critical contaminants from Ground Zero and nearby
were not taken until September 14, such as asbestos, while other contaminants were not sampled
until September 23, such as dioxin. Rapid initiation of monitoring will allow the measurement
of air concentrations that can be very important for evaluation of inhalation exposures and
potential short and long-term human health impacts.
Therefore, very little data are available to quantify exposures which could have occurred in
the hours and days following the collapse of the WTC towers on September 11. As discussed in
all of the individual contaminant sections, the general trend was that air concentrations were
elevated in the earliest samples, and that concentrations appeared to return to background within
weeks to a few months. The section on particulate matter (PM) went further by speculating on
what the air concentrations of PM might have been in the initial plume cloud that occurred on
September 11, based on an empirical relationship between visibility and PM concentration. The
PM section also included discussions on the findings published by Lioy et al. (2002), who
sampled dust which had settled onto cars and other surfaces, and had been undisturbed when
their sampling occurred a few days after September 11. The USGS has similarly sampled and
reported on measurements of contaminants in dust and debris (http://speclab.cr.usgs.gov/wtc/).
Modeling studies within EPA to evaluate the movement of plumes in the few days after
September 11 are ongoing (preliminary results are presented in the PM section), and these may
shed light on exposures which could have occurred during these few critical days.
Epidemiological studies may also elucidate information on exposures during the first few days
after September 11.
It seems apparent that higher concentrations would have been found in the time frame of
about September 11 to September 18 compared to the concentrations that were found when
monitors did get in place. The earliest ambient monitoring data within Ground Zero and in the
closest monitors are the asbestos sampling results which were measured first on September 14.
Benzene and PCB measurements were reported for September 16. Lead was reported starting on
September 18, and PM2 5 was reported first on September 21. The first measurements for dioxin-
like compounds were not available until September 23.
Table 15 lists the first measurements on dioxin, asbestos, and lead in samplers within
Ground Zero (the "WTC" sampler) and at locations bordering Ground Zero (e.g., Church &
Dey). The data on that table supports the hypothesis that higher concentrations were likely to
have been present within the first few days after September 11 as compared to when monitoring
did begin. As seen, generally the highest concentrations were the very first ones available or
within the first week or two of sampling. It is also noted that for dioxin and lead, the monitoring
stations on South End Avenue (Liberty & South End, Albany & South End, and Rector & South
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End) were showing very low background measurements on these first days of sampling at the
same time the samplers within the plume - the WTC sampler and the Church & Dey sampler -
were showing very high concentrations.
These data and similar data for other contaminants underscore the importance of being able
to monitor very early after such an event. It is also recognized that a major uncertainty for the
evaluations presented in this report is the lack of information on exposures which could have
occurred within that first critical week after September 11.
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Table 14. Summary of the first measurements of dioxin TEQs, asbestos, and lead at locations
within or very near Ground Zero.
Contaminant
Concentration; Location;
Sampling Date
Later Measurements and Other Comments
Dioxin TEQ,
pg/m3
160 WTC 9/23
170 WTC 10/2
170 WTC 10/4
All subsequent measurements were less than 100 pg
TEQ/m3 through 5/28/02. Note: Upwind monitors on
South End (Liberty, Albany and Rector) all showed NDs
on 9/23, indicating that elevations were tied to plume.
130 Church/Dey 9/23
No further samples > 10 pg/m3; samples through 5/17/02
100 Liberty/Broadway 9/23
No further samples > 10 pg/m3; samples through 10/26/01
Asbestos,
S/mnf
160 Barclay/W Broadway 9/14
ND Barclay/W Broadway 9/15
128 Barclay/W Broadway 9/15
All subsequent Barclay/W Broadway lower than 100
S/inin2.
80 Albany/West 9/22
89 Albany/West 9/23
178 Albany/West 9/27
71 Albany/West 9/30
Concentrations were less than 70 S/inin2 on Sep. 17, 18,
20, and 21, but no measurements above 70 after 9/30.
48 Liberty/S. End 9/14
90 Liberty/S. End 9/15 (dup)
53 Liberty/S. End 9/15
80 Liberty/S. End 9/30
There were measurements between 9/15 and 9/30 that
were less than 50 S/mnf, but no measurements after 9/30
above 50 S/mnf
Asbestos3,
f/cc
0.1 Fulton/Church 9/13
0.078 Fulton/Church 9/26
0.059 Fulton/Church 9/28
All subsequent measurements after 9/28 were under 0. 04
f/cc (through 8/03/02), but 6 samples between 9/15 and
9/19 were between 0.020 and 0.034, and samples on 10/1
and 10/3 were at 0.035 and 0.023, respectively.
0.035 Veseyb 9/16
0.024 Veseyb 9/17
Next samples on 10/6-10/9 were between 0.008 and 0.023;
no samples taken after 10/9.
0.035 Fultorf 9/15
0.030 Fultorf 9/16
One sample on 9/14 was below LOQ; no samples taken
after 9/16.
0.020 Liberty/Church 9/14
0.021 Liberty/Church 9/18
One sample on 9/14 was below LOQ; no samples taken
after 9/18.
Lead, |ig/m3
4.3 Barclay/W. Broadway 9/23
2.8 Barclay/W. Broadway 9/27
One sample >1.0 |ig/m3 on 10/4, otherwise, all samples <
0.6 |ig/m3: samples through 2/5/02
1.9 Church/Dey 9/18
1.7 Church/Dey 9/23
all other < 0.7 |ig/m3: samples through 2/5/02.
5.4 WTC 9/23
next sample at WTC on 10/2 was 1.1, and one other 1.1 on
10/15, but otherwise all samples < 0.8 through 2/5/02.
Similar to dioxin, all South End sampling locations had
very low findings in initial 9/23 samples.
a All of these samples taken by and reported by the NYCDEP.
b Actual location was described as, Vesey between Church and Broadway.
c Actual location was described as, Fulton between Church and Broadway.
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Section VI. Data on Indoor and Occupational Exposures
This section provides a summary of data that are available, or that are being generated,
from Ground Zero sites where rescue, clean-up and other workers may have been present, and on
the indoor air environment. The occupational exposure data are related directly only to the
workers on Ground Zero who were potentially exposed to contaminants generated during the
course of their work . The indoor exposure data relate to residents in buildings off of Ground
Zero whose exposure is from contaminated air that may have infiltrated their living or working
spaces during or at some point after the disaster. It is emphasized that this section does not
provide any human health risk evaluations in the way that ambient air data were evaluated in
Section IV, except when summarizing conclusions of the original authors of the data.
Vl.a.	Data From Ground Zero Relating to Occupational Exposures
The Occupational Safety and Health Agency (OSHA) and the National Institute for
Occupational Safety and Health (NIOSH) have generated data sets on air quality at Ground Zero.
These data sets are summarized below. Further information on the data and the evaluation of
these data can be obtained through the web sites that are identified below.
As part of the evaluations contained in this report, exposures to PCBs and dioxin toxic
equivalent (TEQ) concentrations that were measured at Ground Zero were evaluated for on-site
workers, which could include workers involved in rescue and clean-up operations. That
evaluation is summarized here, with reference to the more detailed evaluations in Sections IV.
Vl.a.l. OSHA Data
The OSHA data are posted on their Ground Zero monitoring web-site, at
http://www.osha.gov/nyc-disaster/summary.html. Further information on these data can be
obtained from OSHA, with contacts provided at, http://www.osha.gov. No interpretative
analysis of the OSHA data, other than an identification of exceedences of benchmarks, is
provided on the web site or from other available sources.
A total of 1434 asbestos samples (excluding bulk and blank samples) were taken. From
September 19-21, 177 samples were taken in the financial district. Since September 21,
sampling focused on the WTC site and those workers working in or immediately next to it. A
total of 179 of the samples analyzed exceeded OSHA's PEL of 0.1 f/cc. However, upon further
analysis using discriminating counting methods and/or TEM analysis, the number of asbestos
fibers found dropped dramatically to below detectable levels or well below 0.1 f/cc.
The web site also summarizes data taken on CO, total dust, respirable silica, several
organic compounds including PCBs, PAHs, dioxins, VOCs, and others, freon-22, hydrogen
fluoride, phosgene, inorganic acids, oxides of nitrogen/sulfur, metals including lead, mercury,
arsenic, and others, ionizing radiation, and noise. The web site indicates very few exceedences
of OSHA PELs or other relevant benchmarks.
The results for respirable silica suggested some exposure. Of 1353 silica samples, 94
exceeded the PEL. The highest sample result was approximately twenty-one times the OSHA
limit (jack hammering concrete 16 feet below grade). The other elevated exposures were
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approximately one to fourteen times the OSHA limit. These exposures occurred during: 1)
pre-drilling /slurry wall 2) jack hammering, 3) rubble removal and loading operations near the
Winter Garden; 4) during the breaking up of concrete in the pit; 5) while drilling the concrete
slurry wall, 6) flagging operations in pit, and 7) while chipping concrete with power tools during
demolition activities at 7 WTC's parking garage. Most of the work areas where apparent
overexposures to silica occurred were in the rubble pile/pit.
Similar to other results, very few exceedences of organic compounds were identified,
including one exceedence for the benzene OSHA Allowable Limit of 1 ppm, and 8 PAH
exceedences of OSHA's coal tar pitch volatile PEL of 0.2 mg/m3.
For metals, OSHA took a total of 1331 samples (excluding bulk and blank samples) to
monitor worker exposures to dusts, fumes, oxides, and other compounds of metals such as
antimony, beryllium, chromium, cobalt, copper, iron, lead, manganese, mercury, molybdenum,
nickel, vanadium, zinc, cadmium, magnesium, and arsenic. Results from these samples were
generally well below the applicable OSHA limits. However, torch cutting and burning structural
steel at the rubble pile resulted in instances of overexposures as follows: copper (17); iron oxide
(28); lead (19); zinc oxide (1), antimony (1); and cadmium (3).
There were 236 samples collected for employee noise, and 20 samples exceeded the OSHA
PEL of 90 dBA.
VI.a.2. NIOSHData
The NIOSH sampling occurred between September 18 and October 14, 2001. The focus
was on search-and-rescue personnel, heavy equipment operators, and workers cutting metal
beams, but other occupations were also sampled. A total of 1174 air samples were taken,
including 804 for asbestos. The New York City Department of Health and Mental Hygiene
(NCDOHMH) collected most of the asbestos samples, while NIOSH personnel collected all
other samples. In addition to air samples, 33 samples of dust, debris, and other materials were
taken. NIOSH has reported on results for asbestos, metals, respirable particulate, CO, hydrogen
sulfide, inorganic acids, VOCs, elemental carbon, Freon™-22, and PAH (CDC, 2002).
The bulk samples mostly showed asbestos concentrations at <1% (by mass); 3 of 29
samples had mass concentrations ranging from 1-3%. Analysis of air samples for asbestos by
PCM revealed fibers in 358 of 804 samples (45%). Of 25 samples measured by PCM which
exceeded the 0.1 f/cc REL, 18 were measured then by TEM, and all had asbestos concentrations
less than 0.1 f/cc. Differential analysis by polarized light microscopy of these 25 air samples
revealed that most nonasbestos fibers were fibrous glass, gypsum, and cellulose.
Air concentrations of total (36 samples) and respirable (18 samples) particles showed
maximum concentrations of 2.3 and 0.3 mg/m3, respectively, which are below the corresponding
RELs of 10 and 5 mg/m3 for Portland cement. Respirable crystalline silica was not detected in
any of the 18 samples measured for it.
Two instantaneous peak CO measurements exceeded the 1,200 ppm level (at 1239 and
1369 ppm), the level NIOSH considers an immediate danger to life and health. One was from a
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torch cutter and the other from a gasoline-powered saw operator. In 99 other samples,
concentrations of CO ranged from 0.2 to 242.0 ppm. This high value was from a 32 minute
sample, and it exceeded the NIOSH limit of 200 ppm and would have exceeded the PEL of 50
ppm had it been sustained for 2 hours.
CDC (2002) contains descriptions of all other contaminants measured. In general, nearly
all samples were below relevant limits. An "Editorial note" at the end of the article (CDC, 2002,
p. 455) concludes that, "At the time of the NIOSH sampling, the ambient air did not appear to be
contaminated with toxic substances from the building or their contents or with combustion
products to an extent that posed an occupational health hazard."
Vl.a.3. Occupational Exposure to PCBs and Dioxins
These two classes of compounds were measured at Ground Zero (WTC Building 5
monitor) and for several locations just off-site. It was judged that EPA's 8-hour continuous air
monitoring data on these two classes of compounds was adequate to be evaluating worker
exposures in Section IV. These evaluations are contained in Sections IV.c (PCBs) and IV.d
(dioxins), and are summarized here.
For PCBs, the highest concentration measured was 153 ng/m3, which was measured at
Ground Zero. All other measurements were less than 100 ng/m3, with most at ND or within a
typical urban range of 1-8 ng/m3. These are much lower than the NIOSH REL at 1000 ng
PCB/m3 as an 8-hr time weighted average air concentration (NIOSH, 2002) and the OSHA PEL
at 500,000 ng PCB/m3 as an 8-hr time weighted average air concentration (NIOSH, 2002).
Using EPA procedures for estimating 95% upper bound cancer risk, an individual exposed to the
highest concentration found at 153 ng PCB/m3 for a period of one month is estimated to have an
excess lifetime cancer risk of about 2*10"8. EPA regulatory programs, such as the Superfund
Program, typically consider individual incremental cancer risk estimates made in this manner
(i.e., in the context of a scenario-based risk assessment) in the range of 10"4 to 10"6 to be of
potential significance, depending on the circumstances. On this basis, an incremental cancer risk
estimate in the range of 10"8 is judged to be insignificant.
For dioxins, potential cancer and non-cancer risk were assessed using methods that are
detailed in EPA's Draft Dioxin Reassessment (EPA, 2000). First, a "scenario" is defined, which
describes the pathways of exposures, contact rates with dioxin within these pathways, and the
concentrations of dioxin in the exposure media. The scenario for the Ground Zero worker was as
follows: this individual is exposed 10 hours per day, 5 days per week, in the time period between
September 12 until November 30, 2001. The pathway of exposure is via inhalation, and the rate
of inhalation for a WTC worker is 1.3 m3/hr. Using data from the Ground Zero monitor, the
average concentration during this time was calculated as 60.7 pg TEQ/m3. Exposure during that
time, expressed in terms of mass inhaled divided by body weight and time (pg TEQ/kg-day) is
converted to a lifetime dose, and when combined with the appropriate dioxin cancer slope, a
95% upper bound estimate of cancer risk was estimated as 3*10"6, which is about 2 orders of
magnitude lower (100 times lower) than current US background cancer risk to dioxin-like
compounds. This background risk is primarily due to ingestion of foods of animal origin. For
non-cancer risk, a newer approach based on calculation of an incremental increase to background
body burden was employed. The dose over the three month exposure period was used in a
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simple model to predict body burden increase, and it was found that the exposure of the WTC
workers suggests that their body burden could rise up to 10% above current average background.
These cancer and non-cancer results resulting from dioxin exposure were evaluated as not
significant risks over average background risks for this class of compounds.
Vl.b.	Data on Indoor Environments
EPA Region 2 is currently conducting extensive monitoring and clean-ups of indoor
residences. Much of the information on this effort can be seen on the following
website:www.epa.gov/wtc. Part of their effort is to also evaluate background conditions, so that
measurements can be compared to this background. It is expected that this effort will provide
data from which EPA can conduct further health risk assessments. Also, EPA's Region 2 has
been collecting data from various public and private monitoring efforts, and have provided a
tabular summary of their preliminary compilation for use in this report (table provided by M.
Maddaloni, Region 2, to M. Lorber, EPA Washington, August 18, 2002). The Agency for Toxic
Substances and Disease Control (ATSDR) has conducted the only systematic study of the
residential environment to date, and the results of their efforts are summarized below. Other
summaries are provided below only for the systematic efforts that have been conducted or are
underway.
Vl.b.l. ATSDR Study on Apartments in Lower Manhattan
The New York City Department of Health and Mental Hygiene (NYCDOHMH) and
ATSDR have released the Final Report of the Public Health Investigation to Assess Potential
Exposures to Airborne and Settled Surface Dust in Residential Ares of Lower Manhattan
(NYCDOHMH/ATSDR, 2002). From November 4 through December 11, 2001, environmental
samples were collected in and around 30 residential buildings in lower Manhattan. In addition,
four buildings above 59th Street were sampled and used as a comparison area for this
investigation.
Bulk dust samples were collected both indoors and on outdoor surfaces and analyzed for
the presence of asbestos by both the PLM (polarized light microscopy) and TEM methods. PLM
can distinguish between fiber types in a bulk sample by their unique appearance and color when
viewed under different wavelengths of light. Asbestos was detected in settled indoor dust in 10
out of 57 (18%) residential units sampled, with the positive samples showing a maximum of
1.5%) asbestos in dust. By comparison no asbestos was detectable in dust samples collected in
the 5 comparison residences. In outdoor dust collected at Lower Manhattan properties, asbestos
was detected in 6 of 14 (43%>) samples, with a maximum asbestos concentration in dust of 3.4%>.
Importantly, airborne fibers were not detected above background levels (stated as 0.003
f/cc — fibers meeting criteria for optical visibility) in any of the indoor air samples collected at
the 57 residences in Lower Manhattan. Some understanding of the protocol design is needed to
interpret the air sampling data. All air filter samples were analyzed first using PCM to determine
if fibrous materials were present. If the PCM count (which does not distinguish fiber type)
exceeded a 0.003 f/cc level identified as background (using the upper Manhattan measurements),
then a TEM analysis for asbestos fibers was performed. Airborne asbestos fibers (meeting
equivalent criteria for optical visibility) were not detectable in any TEM analyses (generally <
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.001 f/cc).
However, since only a minority of the sampling locations (6) had PCM counts above
background, and hence were analyzed by TEM; results are not conclusive regarding the potential
for low levels of airborne asbestos (i. e., at levels < 0.003 f/cc — fibers meeting criteria for
optical visibility). In this regard it should be noted that the specific residences that had
detectable asbestos in indoor dust did not have elevated airborne PCM levels and TEM data were
not collected for these residences. Note that when conditions allowed the residential sampling
utilized an "aggressive" methodology involving the operation of the vacuum exhaust, used for
settled dust sample collection, to stir the air. Additionally, evidence of elevated asbestos levels
was not found in air samples collected in common areas of the apartment buildings or in
adjoining outdoor areas.
The NYCDOHMH/ATSDR Final report also included data on synthetic vitreous fibers
(SVF or fibrous glass) concentrations in indoor and outdoor dust samples at the same residential
locations. SVF (PLM analysis) was detected in a larger number of indoor dust samples (26 of 57
or 46%) and at higher concentrations (range 2-35%) than asbestos. In outdoor dust at these
properties, SVF was detected in 11 of 14 {19%) of samples (concentration range 15 - 72%). As
with asbestos, the study did not provide evidence of airborne SVF above background levels in
indoor air samples collected at the residences in lower Manhattan. PCM measurements will
detect SVF, and in those locations where air samples had total PCM fibers exceeding
background, Scanning Electron Microscopy (SEM) also reexamined filters for SVF. While such
fibers were detectable in two samples, all samples were below 0.001 f/cc.
Air and settled surface dust samples were also analyzed for mineral components of
concrete (quartz, calcite, and portlandite) and mineral component of building wallboard
(gypsum, mica, and halite). The X-ray diffraction analysis (XRD) analysis for crystalline
minerals in air and settled surface dust is reported by NYCDOHMH/ATSDR as semiquantitative
(labeled with a "J"). Air sampling for minerals detected quartz and other building-related
materials in lower Manhattan. The other forms of crystalline silica were not detected in any air
samples except for a one-time detection of cristobalite. The estimated concentrations of these
minerals in air were low. In some locations, mineral components of concrete (quartz [3-19
|ig/m3J], calcite [ND-14 |ig/m3J], and portlandite [ND-95 |ig/m3J]) and mineral components of
building wallboard (gypsum [4-15 |ig/m3J] and mica [ND-43 |ig/m3J]) were detected in air
samples at higher estimated levels in lower Manhattan residential areas than in samples taken at
comparison residential areas above 59th Street (quartz up to 6 |ig/m3J, calcite up to 6 |ig/m3J,
portlandite up to 30 |ig/m3J, gypsum up to 6 |ig/m3J, and mica up to 17 |ig/m3J), Quartz, calcite,
portlandite and gypsum appear to make up a higher percentage of dust in some buildings in
lower Manhattan when compared to settled surface dust samples from buildings above 59th
Street. Quartz was detected up to an estimated 3 1 %J versus up to 2%J found in the comparison
areas above 59th Street. Neither cristobalite nor tridymite was detected in any of the settled
surface dust samples. Similarly gypsum was found at a maximum estimated concentration of
30%J in settled surface dust, higher than the 4%J estimated in the comparison areas above 59th
Street. Calcite and portlandite had maximum concentrations of 21%J and 8%J respectively. At
lower Manhattan locations sampled, quartz was detected in 81% of common areas and 53% of
residences. Gypsum was seen in 88% of common areas and 79% of residences. Minerals were
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found in all lower Manhattan outdoor settled surface dust samples at estimated values ranging as
high as 27%J quartz, 19%J calcite, 5.5%J portlandite, and 27%J gypsum. No visible settled
outdoor dust was available in the comparison areas above 59th Street.
The NYCDOHMH/ATSDR investigators caution that the results of the
NYCDOHMH/ATSDR investigation in Manhattan cannot be extrapolated to the lower
Manhattan dwellings due to the limited number of units sampled and limited ability to address
different cleaning methods, distance from ground zero, or other confounding factors.
Some of the key conclusions of the NYCDOHMH/ATSDR final report are:
•	Exposure to significant amounts of SVF, mineral components of concrete (quartz,
calcite, and portlandite), and mineral components of building wallboard (gypsum) may
cause skin rashes, eye irritation, and upper respiratory irritation, all of which have been
voiced as concerns by citizens and first responders. These irritant effects will subside
once exposure to SVF, mineral components of concrete, and mineral components of
building wallboard end. Some people with pre-existing heart or lung disease (e.g.,
asthma) or a previous history of very high levels of exposures (occupational) to SVF,
mineral components of concrete, and mineral components may be more sensitive to the
irritant effects of SVF, mineral components of concrete, and mineral components of
building wallboard.
•	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.
•	Some settled surface dust could become airborne if disturbed. Therefore, people could
potentially inhale the asbestos, SVF, mineral components of concrete (quartz, calcite, and
portlandite), and mineral components of building wallboard (gypsum, mica, and halite)
found in settled surface dust of some lower Manhattan residences. Because the weight of
dust present in the areas sampled was not determined, it is not possible to determine
whether any particular residence had an elevated dust loading. Appropriate continued
frequent cleaning should minimize exposures.
•	Several worst-case assumptions were made in order to assess the potential long-term
public health risks of airborne asbestos and quartz. Some of the assumptions were that no
cleaning of indoor spaces has occurred or will occur, all fibers found in air were asbestos
fibers, and the highest levels detected last fall in air represent long-term air levels. Using
these worst-case assumptions, prolonged exposure (decades) to airborne asbestos and
quartz may increase the long-term, theoretical risk of people developing lung cancer and
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other adverse lung health effects (more than 1 additional case in 10,000 people exposed).
For individuals who conduct frequent cleaning of their residences, or participate in the
EPA cleaning/sampling program (described below), it is unlikely that their exposure
would resemble these worst-case conditions. Residents who follow these cleaning
recommendations would not be expected to have any significant increased risk of cancer
or other long-term health effects due to asbestos or quartz.
Based upon the conclusions of their investigation, NYCDOHMH and ATSDR made the
following recommendations (NYCDOHMH/AT SDR, 2002):
•	Because more asbestos, synthetic vitreous fibers (e.g., fiberglass), mineral components
of concrete (quartz, calcite, and portlandite), and mineral components of building
wallboard (gypsum, mica, and halite) were found in settled surface dust in lower
Manhattan residential areas when compared to comparison residential areas, the New
York City Department of Health and Mental Hygiene and the Agency for Toxic
Substances and Disease Registry are recommending that people continue to conduct
frequent cleaning with HEPA vacuums and damp cloths/mops to reduce the potential for
exposure.
•	To ensure that the recommended frequent cleaning is effective and to ensure that the
health of the people of New York City is protected, the New York City Department of
Health and Mental Hygiene and the Agency for Toxic Substances and Disease Registry
are recommending additional monitoring of residential areas in lower Manhattan. In
addition, an investigation should be conducted to better define background levels specific
to the city of New York for asbestos, synthetic vitreous fibers, mineral components of
concrete (quartz, calcite, and portlandite), and mineral components of building wallboard
(gypsum, mica, and halite).
•	Lower Manhattan residents concerned about possible World Trade Center-related dust
in their residential areas can request cleaning and/or testing from the Environmental
Protection Agency as part of their current clean-up program (see next section).
VI.b.2. The Multi-Agency Task Force Efforts Led by US EPA
EPA and its federal, state and city partners have begun to clean up residences impacted
by the collapse of the World Trade Center. The clean-up covers residential units south and west
of Canal, Allen and Pike Streets, river to river. This effort is being coordinated by the
multi-agency Task Force on Indoor Air in Lower Manhattan created by the EPA Administrator.
Much of the information on this clean up effort can be found on the web at
http://www.epa.gov/wtc. The clean-up includes:
upon request, the clean-up of residential units, using certified contractors, with followup
testing for asbestos in the indoor air, or; testing-only of asbestos in the indoor air;
• reimbursement for HEPA (High Efficiency Particulate Air) filter vacuums;
distribution of health and cleanup information;
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establishment of a Web page (http://www.epa.gov/nyrdust2/dustcleanup/) and a toll-free
hotline (1-877-796-5471 (TTY for the deaf and hard of hearing: 1-800-396-1018)) to take
cleanup and testing requests;
professional cleanups of remaining unoccupied, uncleaned buildings;
evaluation of effectiveness of dust cleanup techniques already used, and testing to
establish what the pre-existing levels of contaminants were for Manhattan residences.
Three studies are underway to help develop this clean up plan:
Indoor Air Assessment: Selecting Contaminants of Potential Concern and Setting Health-Based
Benchmarks - The Contaminants of Potential Concern (COPC) Committee of the World Trade
Center Indoor Air Task Force is preparing this report to select COPCs and set health-based
benchmarks for levels in residences to assist the Pilot Cleaning Effectiveness Initiative and
inform the selection of contaminants in the Background Study (these latter two studies are
addressed below). Six COPCs have been proposed: lead, PAHs, dioxin, asbestos, fibrous glass
and crystalline silica. For each COPC, benchmark screening levels have been established for
both indoor air and indoor surfaces, using a three tier approach:
Tier I - Level above which, after elimination of potential indoor sources (combustion by-
products, stored chemicals, etc.), aggressive clean-up action should be taken
expeditiously along with follow-up sampling to confirm attainment of Tier III level.
Tier II - Range where diligent cleaning should continue, after elimination of potential
indoor sources (combustion by-products, stored chemicals, etc.), with follow-up sampling
to confirm attainment of Tier III level.
• Tier III - Level below which the risk is negligible or consistent with the New York City
background level found in the Background Study.
Pilot Cleaning Effectiveness Initiative - EPA is conducting a pilot program in an
uncleaned/unoccupied building at 110 Liberty Street to determine the effectiveness of various
cleaning methods for removing asbestos and other contaminants of potential concern from
residential dwellings. EPA has completed sampling for contaminants in 110 Liberty Street, a
still-unoccupied building close to the WTC site, in what is a comprehensive test of the
effectiveness of various cleanup techniques. Cleaning procedures to be tested include those that
were recommended following the collapse of the WTC as well as others that may have been used
in cleaning residential units. Comprehensive sampling has been or will be conducted before,
during and after the pilot cleanup.
Background Study - Most if not all of the pollutants associated with the collapse of the World
Trade Center were present in New York City's environment prior to September 11. To establish
a baseline for the presence of these contaminants in affected residences, EPA will collect and
analyze samples to look for some of these pollutants in apartments in parts of Manhattan that
were not impacted. The Agency will use the data to determine pre-existing or "background"
levels of these pollutants in interior spaces in New York City.
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VI.b.3. Ground Zero Elected Officials Task Force Study of Apartments
A "Ground Zero" Elected Officials Task Force convened within days of September 11 to
evaluate the environmental safety of apartments that housed an approximate population of
50,000 residents of lower Manhattan who lived within blocks of Ground Zero. A small-scale
monitoring study of two residential buildings was conducted by contract (Chatfield and
Kominsky, 2001). Surface wipe samples were taken from both exposure residential dwellings
characterized as "high" and "low". The "high" location, so named due to the expectation that
higher concentrations would be measured, was in an apartment building located on South End
Avenue, close to and southwest of Ground Zero. Apartment 10D, on the East side of this
building and which had sustained window damage, was selected for sampling. Heavy dust
deposits were in the apartment and were sampled for this study. The "low" location was located
four blocks north on Warren Street. The apartment building did not appear to sustain any
external damage. Apartments on the 2nd and 5th floor were sampled. Dioxins, furans, and PCBs
were measured in wipe and bulk dust samples. Inorganic metals including arsenic, cadmium,
mercury, lead, and several others, were measured. Asbestos in air and dust was also measured in
all sites.
Concentrations of dioxin, PCBs and metals were generally within "background" levels
for both the "high" and "low" exposure apartments. However, asbestos readings were elevated
in both air and dust, particularly in the "high" apartment. Chrysolite asbestos fiber counts were
obtained using TEM analysis and AHERA counting protocols (fibers > .5 |im) and also by
PCME (fibers >5 |im). Looking at the TEM analysis using AHERA protocols for this summary,
7 air samples in the "low" site showed 6 indoor exceedences of the 70 S/mm2 AHERA standard
at 316, 379, 279, 142, 141, and 162, with the last sample being a rooftop sample showing a
reading of 6.5 S/mm2. All these samples were obtained at volumes very near the required 1200
liters. The "high" air samples were extremely elevated with asbestos, and most samplers were
discontinued before 1200 liters due to high dust on the filter. Counting of structures greater than
0.5 |im was stopped after just one grid opening because of the large number of structures to
count. The six measurements equal 10,620; 7,832; 6,277; 6.285; 7,155; and 548 S/mm2. The
last sample listed here was an exterior sample; it was taken from just outside a sliding window in
the apartment.
Asbestos in indoor dust samples was similarly very high. At the "low" apartment, dust
was visible on all surfaces and wipe samples were taken with a wet non-woven cloth in
accordance with ASTM D6480-99. At the "high" apartment, furniture and surfaces were coated
with a thick coat of dust that could be swept up with a brush. A new toothbrush was used to
collect samples in this apartment. At the low apartment, surface chrysotile concentrations up to
470,000 S/cm2 were observed, of which up to 79,000 fibers/cm2 were fibers and bundles longer
than 5 |im. In the high apartment, surface chrysotile concentrations of up to 990,000 S/cm2 were
observed, of which up to 46,000 were fibers and bundles longer than 5 |im.
Outdoor dust samples and the percentage chrysotile by weight included: a sample
collected on the roof of an automobile parked on Church St on the North side of the WTC site -
0.67% chrysotile, on top of an apartment house on Warren St - 1.05% chrysotile, and two
samples on the southwest side of the WTC site on South End Ave - 2.25% and 2.05% chrysotile.
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VI.b.4. New York City Department of Environmental Protection Sampling of
Indoor Dust and Air
The New York City Department of Environmental Protection (NYCDEP) has gathered
indoor dust and air sampling data from numerous building owners/managers as part of their
Asbestos Control Program. Sampling procedures and analytical methods vary from building to
building making data summary difficult. For settled dust, bulk samples were generally obtained
and analyzed for percent asbestos content. Many buildings report pending results. Available data
indicate non-detect or trace amounts of asbestos in most locations. In general, asbestos
concentrations were low especially when compared with occupational standards. Most sample
analyzed by PCM (NIOSH 7400) were below 0.01 f/cc while most samples analyzed by TEM
(AHERA) were below 70 S/mm2.
VI.b.5. New York City Board of Education Sampling of Schools
At the request of the Board of Education (BOE), ATC Inc. conducted bulk dust/wipe and
indoor air sampling during the time period December 2001 to March 2002 in the following WTC
area schools: Stuyvesant HS (345 Chambers St), HS of Economics and Finance (100 Trinity
Place), HS for Leadership and Public Service (90 Trinity Place), PS 150 (334 Greenwich St), PS
234 (292 Greenwich St), and PS/IS 189 (201 Warren St). A limited amount of asbestos bulk
dust samples were obtained from these schools. No samples taken from inside the schools exceed
1% asbestos. One sample from PS/IS 189 taken from outside the building exceed 1% asbestos
and one sample taken from debris on the roof of PS 234 exceeded 1% asbestos. Wipe samples
were obtained and analyzed for a host of contaminants including lead, chromium, cyanide,
PCBs, dioxin, silica and fibrous glass. With few exceptions, levels were below health-based
guidelines/standards. Exceptions included: P S 150 had one lead sample from a window well
that exceeded HUD guidelines; HS of Economics and Finance had multiple lead wipes that
exceeded HUD guidelines; Stuyvesant HS had lead samples from the 5th and 6th floor that
exceeded 40 |ig/ft2 on 02/06/02, but follow-up sampling the next day were below HUD
guidelines.
All six schools were repeatedly sampled (samples from Stuyvesant began on 9/21/01) for
asbestos in air by AHERA TEM protocols. All samples were below the AHERA standard of 70
S/mm2 with the following exceptions: HS for Leadership and Public Service - (2/23/02) 956
S/mm2 found in the 2nd floor auditorium; (2/24/02) 2,379 S/mm2 found in the basement gym;
(2/26/02) 978 S/mm2 found in the basement gym. Two follow-up samples taken from the gym
on 2/28/02 were non detect.
All six schools were repeatedly sampled for respirable particulates (PM 2 5). Most
schools had multiple days that exceeded the 24 hr standard for sensitive subpopulations (40
|ig/m3) but few exceeded the 24 hour standard of 65 |ig/m3.
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Section VII. Comments and Future Studies
Ambient concentrations of monitored substances of concern have generally decreased to
background concentrations in the aftermath of the September 11 disaster. Most substances were
at these backgrounds during 2002, although some exceptions were noted. Concentrations of
benzene and other VOCs at the North Tower site were considerably above typical urban
background as recently as early January, and air concentrations of dioxin were considerably
elevated above urban background at monitors close to the WTC site through early December.
The average daily benzene concentration at the North Tower was also above the OSHA PEL in
early January. Concentrations of asbestos above the AHERA standard were detected in February
and March.
Although the general trend of decreasing ambient concentrations for the measured
pollutants is reassuring, there are limitations in the interpretation of the data. For example, very
little data are available for exposures in the few days to a week immediately after September 11,
and there is very little information on exposures inside residences or offices where people spend
most of their time. Sampling of air and dust within residences has been conducted by ATSDR,
and the results of that study are provided. This study showed very little asbestos in the air in
apartments near the WTC and in the comparison apartments. However, a small number of
apartments near the WTC had asbetsos detected in the dust samples while none were detected in
the comparison apartments. Air and dust within 2 apartments located near the WTC were
sampled on September 18. Very low concentrations of dioxin, PCBs and metals were found.
However, asbestos readings were elevated in both air and dust in both apartments. EPA is now
conducting extensive indoor air monitoring, and the results will be evaluated in future EPA
reports.
Data do exist for reactive VOCs such as formaldehyde, acetaldehyde, or acrolein, all of
which are irritants and might have been produced by the fires at WTC, but to date, these data
have not been evaluated. Although the press reported the fires to be out at the WTC site on
December 20, there are reports that the fires flared up on occasion in January.
From interpretation of photographs taken during the hours following the collapse of the
WTC Towers, it is speculated that some people may have been exposed to the extremely high
levels of ambient PM and its constituents were likely to be at risk for immediate acute
respiratory and other symptoms. Fine particles or metals such as chromium and nickel in the
initial dust cloud could have been irritating or sensitized individuals to further response. The
cumulative risk from so many different exposures at high concentrations may well have
produced effects that cannot be fully discerned by examination of exposure to individual
substances. The potential for multiple chemical sensitivities is of potential concern. Also, even
though data may suggest that a substance is associated with a particular effect, a quantitative
guidance value may not have been developed. Thus, simply comparing ambient concentrations
against known health guidance values may overlook some effects.
Further studies of potential health effects resulting from the WTC disaster are being
conducted by a variety of agencies and institutions. These should help in evaluating some of the
remaining uncertainties regarding exposure and human health impacts resulting from the
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collapse of the WTC buildings. Results from some of these studies are not expected for several
years, although some results should be available earlier. Studies are being conducted to evaluate
exposures and health effects in persons that were around Ground Zero on September 11 and
throughout the rescue and cleanup operations. The studies will be extremely important in getting
a more complete picture of some of the actual health effects that resulted from exposures. This
is particularly important because we have very little data regarding what people were exposed to
September 11 as they were leaving the WTC area surrounded by plumes of dust and burning
debris.
To better understand actual exposures on September 11, researchers at EPA's ORD
laboratories, in cooperation with academic institutions, are working on projects that will use
computer models to reconstruct the plume of dust and debris. The goal is to model and predict
the levels of contaminants that were present in the air immediately following the collapse of the
WTC buildings. Preliminary results from that modeling have been presented in this report.
Investigators are using meteorological data and data available from monitoring results later in
September to estimate exposures. When this research is complete, it will aid in addressing
health effects.
Studies are also being conducted to help us better understand how exposure to
contaminants measured and collected in lower Manhattan throughout this period may cause
adverse effects in laboratory tests and animal models. As cited previously, ORD NHEERL
scientists conducted several studies to examine the chemical and toxicological properties of
PM2 5 derived from bulk settled WTC dust (EPA, 2002c; McGee et al., 2002). Comparative
respiratory toxicology studies showed that a high dose of WTC PM2 5 caused mild lung
inflammation and significant respiratory tract hyperresponsiveness in mice. Ambient
concentrations which could cause comparable doses and effects in people are high but
conceivable (425 |ig/m3 over 8 hours) in the immediate aftermath of the collapse of the towers
(Gavett et al., 2002). Dust and air samples are also being evaluated by other researchers through
funding from NYSDOH.
Most importantly, many local, state and federal agencies and academic institutions have
already began or are planning studies that will monitor the health status of various groups of
people that were affected by the events of September 11. In total, EPA is aware of more that 120
studies on health effects in populations impacted by the events of September 11. Although it is
impossible to address them all, a few general categories are discussed below.
Health status, including asthma, among students is one of the many health
endpoints that will be evaluated at many schools. Respiratory symptoms,
including asthma, will be studied in pre-school children and other child
populations as well.
Longitudinal cohort studies on the impacts on pregnant women and birth
outcomes are also being conducted.
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Cohort studies looking at multiple health endpoints are beginning to evaluate
health effects in populations of workers involved in the rescue and cleanup
efforts.
Studies are under way to investigate many different mental health outcomes
including post-traumatic stress disorder, trauma to children, behavioral changes in
adolescents, changes in therapy adherence in HIV/AIDs patients, impacts in
particular NYC minority populations, and impacts in occupational groups
involved in the cleanup and rescue efforts.
While monitoring air quality is complete at the WTC site, NYSDEC will continue
its routine ambient air monitoring at a number of nearby sites and at the sites
around New York City, including a number of schools.
It is hoped that when they are completed, these studies will provide a more complete
picture of actual health outcomes. This current report can only evaluate exposures based upon
available monitoring data and results, and what these exposures could mean to human health.
When the health studies are completed, it will be very useful for EPA to go back and reassess
how well the evaluations in this report identified, or didn't identify, a human health concern.
This retrospective look will help EPA and other health agencies to do a better job assessing
health risks and outcomes in the future. In the meantime, EPA will continue to address potential
health risks as needed. EPA will provide a more thorough report, looking at additional
contaminants and conducting further evaluations as needed.
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APPENDIX A - WORLD TRADE CENTER HEALTH EFFECTS SCREENING
CRITERIA FOR AMBIENT AIR DEVELOPED BY EPA'S REGION 2
Provided by: Mark Maddaloni
US EPA, Region 2
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World Trade Center Health Effects Screening Criteria for Ambient Air
Introduction
Extensive air quality monitoring data have been collected at and around the World Trade Center
(WTC) site since 9/11/01. Table 1 (Screening Criteria) is intended to provide health protective
screening values for data evaluation. Analysis has been performed on an extensive list of
potentially WTC-related contaminants. Many of the chemicals screened have demonstrated a
consistently low (i.e., below detection limits or trace amounts) trend. Consequently, the list of
contaminants in Table 1 represents those chemicals that, because of their intrinsic toxicity and
frequency/magnitude-of -detection, pose the greatest potential hazard from exposure. This
selection process (i.e., a toxicity/concentration analysis), although qualitative, reflects the
contaminant-of-concern identification process recommended in the Risk Assessment Guidance
for Superfund. Table 1 may be expanded as additional data analysis becomes available. Two
populations have been identified for assessment: response/demolition (i.e., WTC site) workers;
and residents living in Lower Manhattan (e.g., Battery Park City, Tribeca and other residential
locations close to Ground Zero). Included in the resident category are all other workers located
in Lower Manhattan with the exception of WTC site workers.
Relevant Standards
The following paradigm has been employed to develop screening values. For each of the two
identified receptor populations (i.e., site workers and residents), existing standards are utilized
where appropriate. Occupational standards (i.e., OSHA PELs) are used for all site workers
conducting response/demolition activities covered by OSHA. Monitoring data from demolition
areas are compared to OSHA PELs. (For example, the OSHA PEL of 1 ppm for benzene is used
to evaluate benzene air samples taken directly from within the plume on the debris pile.)
Environmental standards (e.g., NAAQS, AHERA) are utilized to evaluate monitoring data from
the site perimeter and beyond where residents or non-WTC site workers may be exposed. (For
example, lead air monitoring data from perimeter stations outside of the immediate work zone
are evaluated against the NAAQS of 1.5 |ig/m3).
Risk-Based Screening Criteria
In cases where appropriate standards do not exist, risk-based screening criteria have been
developed for residential (including the non-WTC site workers) receptors. (In the absence of
OSHA standards, it is beyond the scope of EPA's mission to develop "occupational" screening
values.) The risk assessment paradigm detailed in EPA's "Hazard Evaluation Handbook: A
Guide to Removal Actions" (HEH) was employed for this initiative (except where otherwise
noted in the Table 1 footnotes). Screening levels reflect the most current toxicity criteria (Slope
Factors and RfCs) on EPA's IRIS database.
For carcinogenic compounds excess lifetime cancer risk was set at E-04 (one-in-ten thousand).
The residential exposure scenario in the HEH was modified for carcinogens from the default of
30 years (upper-bound estimate for residency in one dwelling) to 1 year (to reflect an upper
bound estimate for the length of time a resident may be potentially exposed to WTC-related
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contaminants). In cases where the screening value based on a noncancer endpoint is more
stringent, screening values for both cancer and noncancer endpoints are presented. It is also
noted that the default 30 year exposure duration (and the 1 year site-specific adjustment) reflects
an apportionment between child (20% of total exposure duration) and adult (80 % of total
exposure duration) receptors. Because children have comparatively greater (as a function of
body weight) respiration rates than adults, the screening values presented in Table 1 are
marginally more stringent than values that would otherwise be derived by direct application of
IRIS verified Unit Risk values.
For noncarcinogenic compounds, the Hazard Quotient (chronic daily intake/RfC) was set at 10.
A Hazard Quotient of 10 is employed in the HEH to account for the fact that chronic toxicity
criteria (RfDs/RfCs) are being applied to sub-chronic exposure scenarios that are not expected to
exceed 6 months - 1 year in duration. Accordingly, a Hazard Quotient of 10 was utilized for
non-carcinogens in Table 1 to reflect a similar (i.e., upper bound of 1 year) exposure duration.
It is noted that contaminants (both non-carcinogens and carcinogens, alike) can exhibit acute
effects from short-term, high-dose exposures. Because the screening values in Table 1 are based
on subchronic exposure (i.e., 1 year), acute effects from exposures that are below the screening
levels would be unlikely. Additionally, a review of California EPA's (CAL-EPA) Acute Risk
Levels demonstrates that the screening criteria in Table 1 are categorically more stringent than
the Cal-EPA's analogous acute levels.
NOTE: Individual sampling results that exceed screening values should not be interpreted to
represent the occurrence of an adverse health effect. Rather, such information indicates the need
for careful monitoring and the assessment of longer-term data trends for evaluation against
appropriate health criteria. That is, most of the screening levels have been developed to account
for continuous one year average exposure durations. Because these screening levels assume
continuous exposure for an extended duration, the average of the measured concentrations is
more appropriate for evaluating risk than an individual measurement. Consequently,
miscellaneous individual values above the screening level may not necessarily be indicative of
potential for concern.
Table 1
World Trade Center Screening Criteria
Contaminant
Site Worker (1)
Resident(2)
Inorganics
Asbestos (3)
.1 f/cc (PCM)
70 S/mm2 (TEM)
Cadmium
5 |ig/m3
.2 |ig/m3 (9)
3 |ig/m3 (5)
Chromium (4)
100 |ig/m3
.6 |ig/m3 (5)
Lead
50 |ig/m3
1.5 |ig/m3 (7)
Manganese
5 mg/m3
.5 |ig/m3 (6)
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Contaminant
Site Worker (1)
Resident(2)
Sulfur Dioxide
5 ppm
.14 ppm(7)
Particulates
Total
15,000 |ig/m3
NA
Respirable
5,000 |ig/m3
NA
pm25
NA
40 |ig/m3(8)
65 |ig/m3 (7)
PM10
NA
150 |ig/m3(7'8)
Semivolatiles
Dioxin/Furans (TEQ)
NA
.162 ng/m3 (5)
PCBs
1,000 |ig/m3
.73 |ig/m3 (6)
9 |ig/m3 (5)
PAHs (16)
NA
6 |ig/m3 (5'17)
Volatiles
Acetone
1,000 ppm
1.5 ppm (6)
Benzaldehyde
NA
860 ppm
Benzene
1 ppm
.02 ppm (9)
.21 ppm (5)
Benzonitrile
NA
NA
1,3 Butadiene
1 ppm
.01 ppm (5'15)
Chloromethane
100 ppm
.4 ppm (6)
2.6 ppm (5)
1,4 Dioxane
100 ppm
.5 ppm (5)
Ethanol
1,000 ppm
45 ppm (10)
Ethylbenzene
100 ppm
2.5 ppm (6)
Freon 22
1,000 ppm(14)
140 ppm
Propylene
LEL (13)
simple asphyxiant
Styrene
100 ppm
2.3 ppm (6)
alpha methyl styrene
100 ppm
.1 ppm (6)
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Contaminant
Site Worker (1)
Resident(2)
Tetrahydrofuran
200 ppm
.9 ppm(5)
Toluene
200 ppm
1.1 ppm (6)
Xylenes
100 ppm
1 ppm (11)
Reactive Gases
Acetaldehyde
200 ppm
.05 ppm (6)
1.3 ppm(5)
Formaldehyde
.75 ppm
.04 ppm (12)
.35 ppm(5)
Acrolein
.1 ppm
.0001 ppm (6)
Units
f/cc = fibers (>5 |im length) per cubic centimeter of air
S/mm2 = structures (>.5 |im length) per square millimeter of filter paper
ppm = parts per million in air
|ig/m3 = micrograms of contaminant per cubic meter of air
ng/m3 = nanograms of contaminant per cubic meter of air
NA - Not Applicable
Footnotes:
1.	"Site Workers" refers to all workers involved in the response/demolition of the World Trade
Center. Listed values are Occupational Safety and Health Administration (OSHA) Permissible
Exposure Limits (PELs), Time Weighted Averages (TWA) unless otherwise noted.
2.	"Residents" refers to people living in the vicinity of the World Trade Center as well as all
other potentially exposed workers not involved in the response/demolition
3.	Resident screening value is based on Asbestos Hazard Emergency Response Act (AHERA)
methodology which uses transmission electron microscopy (TEM), and because of its basis in
"background" (vs a risk basis) includes all asbestos fibers greater than 0.5 microns in length.
Worker values are based on phase contrast microscopy (PCM, - which doesn't distinguish
asbestos from other fibers) or, for results above the PCM screening value, TEM to derive a PCM
equivalence that includes all asbestos fibers greater than 5 microns in length.
4.	Screening values for chromium were based on the most toxic form (hexavalent)
5.	EPA - Hazard Evaluation Handbook (HEH) (carcinogen) > 1 year of continuous exposure
equating to an excess lifetime cancer risk of one-in ten thousand
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6.	EPA - HEH (noncarcinogen) > Hazard Quotient (HQ) =10
7.	National Ambient Air Quality Standard (NAAQS)
-	Lead is a 3 month average
-	PM2 5 is a 24 hour average
-	Sulfur Dioxide is a 24 hour average primary standard
8.	Air Quality Index (AQI)
9.	Non cancer effects based on CAL-EPA toxicity studies
10.	American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit
Value (TLV)
11.	Agency for Toxic Substances and Disease Registry (ATSDR) Inhalation minimum risk level
(MRL)x 10
12.	ATSDR acute MRL
13.	Lower Explosive Limit (2-11%)
14.	National Institute of Occupational Safety and Health (NIOSH)
15.	Proposed Reference Concentration (RfC) - HEH (noncancer) > Hazard Quotient (HQ) =10
16.	Based on Benzo(a)pyrene toxicity equivalency factor toxicity equivalency factor (TEF)
17.	EPA National Center for Environmental Assessment (NCEA) provisional inhalation Slope
Factor (3.1 E 00 mg/kg/day"1)
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APPENDIX B - TABLE OF MONITORING LOCATIONS
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Table 1. Overview of monitoring locations and responsible parties (see note at end of table for specific notes).
Site Name
Site Location
Pollutants Measured
Sampling Frequency
Analytical
Laboratory
[. EPA's Environmental Response Team Lettered Sites
Location A
Barclay St & West
Broadway
Asbestos
2-12 hour samples daily
Contract
Dioxins (2)/PCBs, PAHs,
Metals, Silica
8 hour sample twice per week
Particulates, VOCs
24 hr. sample daily; grab (VOC)
EPA/ORD
Location B
Church St and Dey St
Asbestos
2-12 hour samples daily
Contract
Dioxins (2)/PCBs, PAHs,
Metals. Silica
8 hour sample twice per week
Location C
Liberty St and Trinity
St
Asbestos
2-12 hour samples daily
Contract
Dioxins (2)/PCBs, PAHs,
Metals, Silica
8 hour sample twice per week
Particulates, VOCs
24 hr. sample daily; grab (VOC)
EPA/ORD
Location CI
(note: station C
ind CI are
'alternate"
stations; see
footnote 1)
Broadway and Liberty
St
Asbestos
2-12 hour samples daily
Contract
Dioxins (2)/PCBs, PAHs,
Metals, Silica
8 hour sample twice per week
Particulates
24 hr. sample every 3rd day
EPA/ORD
Location D
Albany St &
Greenwich St
Asbestos
2-12 hour samples daily
Contract
Dioxins (2)/PCBs, PAHs,
Metals. Silica
8 hour sample twice per week
Location E
Liberty St & South End
Ave
Asbestos
2-12 hour samples daily
Contract
Dioxins (2)/PCBs, PAHs,
Metals. Silica
8 hour sample twice per week
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Table 1. Overview of monitoring locations and responsible parties (cont'd).
Site Name
Site Location
Pollutants Measured
Sampling Frequency
Analytical
Laboratory
[. EPA's Environmental Response Team Lettered Sites (cont'd).
Location F
Vesey St & West St
Asbestos
2-12 hour samples daily
Contract
Dioxins (2VPCBs. Metals
8 hour sample twice per week
Location G
Church & Duane St
Asbestos
2-12 hour samples daily
Contract
Location H
Chase Manhattan Plaza
Asbestos
2-12 hour samples daily
Contract
Location I
Broadway & Wall St
Asbestos
2-12 hour samples daily
Contract
Location J
Warren & West St
Asbestos
2-12 hour samples daily
Contract
Location K
Albany & West St
Asbestos
2-12 hour samples daily
Contract
Particulates, VOCs
24 hr. sample daily; grab (VOC)
ORD
Metals, Silica
8 hour sample twice per week
Contract
Location L
North Side of
Stuyvesant High
Total particulates
~ 8 hours/day
Onsite Dataram
Asbestos
2-12 hour samples daily
Contract
Metals, Silica
8 hour sample twice per week
Contract
Location M
Harrison St & West St
Total particulates
~ 8 hours/day
Onsite Dataram
Asbestos
2-12 hour samples daily
Contract
Location N
Pier 25, Southside
Total particulates
~ 8 hours/day
Onsite Dataram
Asbestos
2-12 hour samples daily
Contract
Location P
Albany St & South End
Ave
Asbestos
2-12 hour samples daily
Contract
Dioxins (2)/PCBs, PAHs
Metals. Silica
8 hour sample twice per week
Location Q
Barclay St & West St
Asbestos
2-12 hour samples daily
Contract
Location R
EPA Taga Bus
Total particulates
~ 8 hours/day
Onsite Dataram
Dioxins (2)/PCBs, PAHs
Metals. Silica
8 hour sample twice per week
Contract
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Table 1. Overview of monitoring locations and responsible parties (cont'd).
Site Name
Site Location
Pollutants Measured
Sampling Frequency
Analytical
Laboratory
[. EPA's Environmental Response Team Lettered Sites (cont'd).
Location S
Rector PI & South End
Ave
Asbestos
2-12 hour samples daily
Contract
Dioxins (2)/PCBs, PAHs
Metals. Silica
8 hour sample twice per week
Location T
Pier 6 Heliport
Asbestos
2-12 hour samples daily
Contract
Location U
Pier 6, Exit 2
Asbestos
2-12 hour samples daily
Contract
Location V
Pier 6, Bus Sign
Asbestos
2-12 hour samples daily
Contract
Location W
Wash Tent, West Street
& Murray
Asbestos
2-12 hour samples daily
Contract
WTC -
Building 5
SW
AKA, Location 3 A
Dioxins (2)/PCBs, PAHs,
Metals, Silica
8 hour sample twice per week
Contract
WTC -
Church &
Vesey (alternate
for WTC; see
"ootnote It
AKA, Location 3B
Dioxins (2)/PCBs, PAHs,
Metals, Silica
8 hour sample twice per week
Contract
S.I. Landfill
Sites
17 Landfill Sites + 3
offsite locations
Asbestos
1-12 hour sample daily
Contract
5 Landfill Sites
Total particulates
12 hour sample daily when temp.
& humidity specs are met.
Onsite Dataram
2 Landfill Sites + 3
Offsite Locations
Metals
1-12 hour sample weekly
Contract
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Table 1. Overview of monitoring locations and responsible parties (cont'd).
Site Name
Site Location
Pollutants Measured
Sampling Frequency
Analytical
Laboratory
EI. Extended Monitoring Network- NYSDEC Numbered Air Monitoring Stations
1
Park Row & Spruce
Street, NY, NY
Asbestos
12 hour sample daily
Contract
Dioxin (1)
72 hour sample every 3 days
Region 7
VOC's
24 hr. sample every 3rd day
ORD
Aldehydes
24 hr. sample every 3rd day
NYSDOH
PM Speciation
24 hr. sample every 3rd day
Contract
PM Sizing
continuous-by NYSDEC
Climet
PM10, PM2.5
continuous- by NYSDEC
PM 2.5 TEOM7
PM10 Filter
2
Chambers St.& West
St.,
NY, NY
Asbestos
12 hour sample daily
Contract
Dioxin (1)
72 hour sample every 3 days
Region 7
VOC's
24 hr. sample every 3rd day
ORD
Aldehydes
24 hr. sample every 3rd day
NYSDOH
PM Speciation
24 hr. sample every 3rd day
Contract
PM Sizing
continuous-by NYSDEC
Climet
PM10,PM2.5,PM
continuous- by NYSDEC
PM 2.5 TEOM7
PM10 Filter
3
U.S. Coast Guard,
1 South Street,
NY. NY (Battery Pkt
Asbestos
12 hour sample daily
Contract
PM10, PM2.5
continuous- by NYSDEC
PM 2.5 /PM10 Filter
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Table 1. Overview of monitoring locations and responsible parties (cont'd).
Site Name
Site Location
Pollutants Measured
Sampling Frequency
Analytical
Laboratory
EI. Extended Monitoring Network- NYSDEC Numbered Air Monitoring Stations (cont'd)
4
Canal Street Post
Office, 350 Canal
Street, NY NY
Asbestos
12 hour sample daily
Contract
PM10, PM2.5
24 hour sample daily-
bv NYSDEC
PM 2.5 /PM10 Filter
5
PS 154, 333 East 35th
Street, Bronx, NY
10454
PM2.5
continuous-by NYSDEC
PM 2.5 TEOM
Asbestos
12 hour sample daily
Contract
6
IS 143, 511 West
182nd Street
nv nv inrm
PM2.5
continuous-by NYSDEC
PM 2.5 TEOM
Asbestos
12 hour sample daily
Contract
7
PS 274, 800 Bushwick
Ave, Brooklyn, NY
11221
PM2.5
continuous-by NYSDEC
PM 2.5 TEOM/
PM10 Filter
Asbestos
12 hour sample daily
Contract
8
PS 44, 80 Maple
Parkway, Staten Island,
NY 10303
PM2.5
continuous-by NYSDEC
PM 2.5 TEOM
Asbestos
12 hour sample daily
Contract
9
PS 199, 39-20 48th
Ave, Long Island City,
NY 11104
PM2.5
continuous-by NYSDEC
PM 2.5 TEOM
Asbestos
12 hour sample daily
Contract
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Table 1. Overview of monitoring locations and responsible parties (cont'd).
Site Name
Site Location
Pollutants Measured
Sampling Frequency
Analytical
Laboratory
[II. Extended Monitoring Network- NJDEP Air Monitoring Stations
NJ-Shell
West Avenue, Sewaren,
NJ
Asbestos
1-12 hour sample on Mon. and
Thurs.
Contract
NJ-Citgo
Tremly Point Road,
Linden, NJ
Asbestos
1-12 hour sample on Mon. and
Thurs.
Contract
NJ-FMC
Roosevelt Blvd.,
Cartaret, NJ
Asbestos
1-12 hour sample on Mon. and
Thurs.
Contract
NJ-Liberty
Liberty State Park, @
WTC Disaster Family
Center
Asbestos
1-12 hour sample on Mon. and
Thurs.
Contract
IV. Extended Monitoring Network- E
JA/ORD Numbered Air Monitoring Stations
14
Albany & West St
NY, NY
Dioxin (1)
72 hour sample every 3rd days
Region 7
PM Speciation
24 hr. sample every 3rd day
Contract
PM Sizing
continuous-by NYSDEC
Climet
PM10, PM2.5
continuous-by NYSDEC
PM 2.5 TEOM7
PM10 Filter
VOCs
24 hr sample every 3rd day
ORD
15
23 Wall Street, NY,
NY
PM10, PM2.5
continuous-by NYSDEC
PM 2.5 TEOM7
PM10 Filter
Aldehvdes
24 hr. sample every 3rd dav
NYSDOH
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Table 1. Overview of monitoring locations and responsible parties (cont'd).
Site Name
Site Location
Pollutants Measured
Sampling Frequency
Analytical
Laboratory
IV. Extended Monitoring Network- E
WORD Numbered Air Monitoring Stations (cont'd)
16
290 Broadway
NY, NY
PAHs & SVOCs
12 & 23 hour samples
ORD
Particulates
continuous
ORD
Notes for Table.
Column 1: Site Name
-	Though not "lettered", the WTC - Building 5 SW site and the Staten Island Landfill Sites have been run by EPA's
Environmental Response Team and are included here.
-	The New Jersey Department of Environmental Protection (NJDEP) site names were designated by NJDEP
-	Locations C (Liberty & Trinity) and CI (Liberty and Broadway), and 3 (WTC Building 5) and 3A (Church & Vesey) were
"alternate" pairs of stations, meaning that sample dates alternated between the paired sites.
-	290 Broadway was a sample site that measured several contaminants, but only on 1 date, October 10, 2001. Because there
was only one date of sampling, this site is not listed above.
Column 2: Site Location:
Column 3: Pollutants Measured:
-	Dioxin (1) = 72-hr samples collected by EPA Department of Environmental Science and Assessment (DESA) Region 2
personnel and analyzed by Region 7.
-	Dioxin (2) = 8-hr samples collected by EPA Emergency and Remedial Response Division (ERRD) Region 2 personnel and
analyzed by a contract laboratory.
Column 4: Analytical Laboratories:
-	Contract = Laboratories contracted by EPA to conduct analysis.
-	ORD = Human Exposure and Atmospheric Sciences Division (HEAS) in the National Exposure Research Laboratory
(NERL), in Research Triangle Park, North Carolina.
-	Region 7 = Regional Laboratory Branch, in the Environmental Services Division (ESD) in Region 7, Kansas City, Kansas.
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