DRAFT NCEA - W - 1395 

DO NOT CITE OR QUOTE EPA/600/P-2/002A 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
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. 

DRAFT--DO NOT QUOTE OR CITE i October 2002 
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 PM2.5 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 μg/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 = 1⁄2 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. 

DRAFT--DO NOT QUOTE OR CITE iii October 2002 
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 μg/m3

) measured at preexisting 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 <one millionth of pollutant 

concentration at WTC source). 

Figure 6. Satellite photograph of the WTC plume lofting from Ground Zero at 11:43 am EDT 

on September 12, 2001. Note the very concentrated vertical convection of dust/smoke particles 

upwards and the flow in a well-defined plume towards the S/SE. (Source: Mandatory Credit: 

“spaceimaging.com”). 

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 the WTC buildings. (PM2.5 data provided courtesy of NYSDEC). 

Figure 8. ORD-modeled WTC plume dispersion for September 13, 2001 at 9:00 am. Note the 

increased hourly PM2.5 concentrations depicted in red for PS 64 (166 μg/m3) and PS 199 (100 

μg/m3

) NYSDEC monitoring stations, consistent with the E/NE direction of the modeled plume 

dispersion and likely touchdown of the plume at those and intervening sites but not at sites 

further E, SE, or to the N. 

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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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 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. 

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 μg/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 μg/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 μg/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, Cl, 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 (μg/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

cubic centimeters 

Cd cadmium 

CDC Centers for Disease Control and Prevention 

Cl 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 

μg microgram 

μm 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 

DRAFT--DO NOT QUOTE OR CITE vii October 2002 

cc 
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-observed-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 μm and less than 10 μm 

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

DRAFT--DO NOT QUOTE OR CITE ix October 2002 
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 

Section I. Overall Purpose and Scope of Assessment 

Section II. Exposure Assessment and Risk 

Characterization Approach 

Section III. Environmental Monitoring 

Section IV. Evaluation 

IV.a. Particulate Matter 

IV.b.1. Lead

IV.b.2. Chromium and Nickel

IV.c. Polychlorinated Biphenyls

IV.d. Dioxins

IV.e. Asbestos

IV.f. Volatile Organic Compounds

Herman Gibb 

Matthew Lorber 

Linda Tuxen 

Herman Gibb 

Matthew Lorber 

John Schaum 

Matthew Lorber 

Herman Gibb 

Nancy B. Beck 

Herman Gibb 

Matthew Lorber 

Lester Grant 

Joseph Pinto 

Lester Grant 

Joseph Pinto 

Nancy B. Beck 

David Cleverly 

Matthew Lorber 

Matthew Lorber 

Aparna Koppikar 

Paul White 

Nancy B. Beck 

Matthew Lorber 

V. Comment on the First Several Days After September 11 Matthew Lorber 

DRAFT--DO NOT QUOTE OR CITE xi October 2002 
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, ATSDR

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

DRAFT--DO NOT QUOTE OR CITE xii October 2002 
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 

DRAFT--DO NOT QUOTE OR CITE 1 October 2002 
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 preSeptember 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 

DRAFT--DO NOT QUOTE OR CITE 2 October 2002 
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 PM2.5 NAAQS (65 μg/m3

, 24-hr); and PM2.5 

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concentrations at some other nearby lower Manhattan sites exceeded EPA’s 40 micrograms per

cubic meter (μg/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 μm in diameter, PM2.5) values at some new

sites set up by EPA or New York State exceeded 40 μg/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 μg/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 μg/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.
DRAFT--DO NOT QUOTE OR CITE 5 October 2002

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 μg/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 μg/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 μg/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 μg/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 μg/m3, with few

even exceeding 0.5 μg/m3.

Lead concentrations in bulk dust samples taken close to the WTC within days after

September 11 ranged up to 625 μg/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 evaluated for 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 VI particulates of 1.0 μg/m3. On the basis of the samples

evaluated, exposures to chromium were not likely to cause any adverse health effects.
DRAFT--DO NOT QUOTE OR CITE 6 October 2002

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 μg/m3 were measured for about a month

month after September 11, to then drop to more typical urban backgrounds less than 0.10

μg/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 NIOSH REL 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
DRAFT--DO NOT QUOTE OR CITE 7 October 2002

orders of magnitude below the OSHA PEL of 5*105 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. 
DRAFT--DO NOT QUOTE OR CITE 8 October 2002

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 of 2001 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. 
DRAFT--DO NOT QUOTE OR CITE 9 October 2002

 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 μm in length), and

8,872 of these were also measured by transmission electronic microscopy (TEM; used to

identify structures less than 0.5 μm 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
DRAFT--DO NOT QUOTE OR CITE 10 October 2002

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, chloromethane, 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 sustained for 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.
DRAFT--DO NOT QUOTE OR CITE 11 October 2002

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.
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 

DRAFT--DO NOT QUOTE OR CITE 12 October 2002 
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 highvolume 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 

DRAFT--DO NOT QUOTE OR CITE 13 October 2002 
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. 

DRAFT--DO NOT QUOTE OR CITE 14 October 2002 
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 nonWTC 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. 

DRAFT--DO NOT QUOTE OR CITE 15 October 2002 
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. 

DRAFT--DO NOT QUOTE OR CITE 16 October 2002 
Table 1. Inhalation health risk screening benchmarks used in this assessment. 

Agency Screening Benchmark Definition 

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. 

ATSDR 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. 

ATSDR Intermediate inhalation 

Minimal Risk Level 

(MRL) 

An intermediate MRL protects against exposures that 

may last 15 - 364 days. 

EPASTSC Provisional Subchronic 

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. 

ACGIH 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. 

DRAFT--DO NOT QUOTE OR CITE 17 October 2002 
Table 1 (cont’d). 

Agency Screening Benchmark Definition 

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. Shortterm (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. 

DRAFT--DO NOT QUOTE OR CITE 18 October 2002 
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] 

DRAFT--DO NOT QUOTE OR CITE 19 October 2002 
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 MultiAgency 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). 

DRAFT--DO NOT QUOTE OR CITE 20 October 2002 
• Historical concentrations of metals, VOCs, PM, dioxin, PCBs, carbon monoxide 

(CO), nitrogen dioxide (NO2), and sulfur dioxide (SO2) 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 

DRAFT--DO NOT QUOTE OR CITE 21 October 2002 
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. 

DRAFT--DO NOT QUOTE OR CITE 22 October 2002 
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 

DRAFT--DO NOT QUOTE OR CITE 23 October 2002 
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 exposurerelated 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 μm diameter) and 

larger, or coarse, particles (ranging from ~2.5 μm to 50 μm 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 

DRAFT--DO NOT QUOTE OR CITE 24 October 2002 
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 μg/m3, 24-hour average, and 50 μg/m3, annual average, averaged over 3 years) to protect 

against health risks associated with inhalable particles (mainly those < 10 μm diameter) that can 

deposit in lower (thoracic) portions of the human respiratory tract. These health-related PM10 

particles include both fine particles < 2.5 μm diameter (PM2.5) and a subset of coarse particles 

larger than 2.5 μm but less than < 10 μm diameter (PM10-2.5). 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 μg/m3, annual average, averaged over 3 years) to protect against both shortand long-term exposures and a supplemental 24-hour average PM2.5 NAAQS (set at 65 μg/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 μg/m3. The AQI is meant to provide reference points for judging 

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 

μg/m3. 

IV.a.1. 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. 

DRAFT--DO NOT QUOTE OR CITE 25 October 2002 
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.com/products/studies/1.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 μg/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 

DRAFT--DO NOT QUOTE OR CITE 26 October 2002 
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 PM2.5 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 Zerogenerated plumes, based on prevailing meteorological conditions (e.g., wind speed and 

direction). This includes: (a) initially, classical Gaussian plume modeling, providing regionalscale 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 

DRAFT--DO NOT QUOTE OR CITE 27 October 2002 
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 μm 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 μm 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 

DRAFT--DO NOT QUOTE OR CITE 28 October 2002 
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 μm diameter (~ 51-64% of 

total mass) and 10-53 μm (~ 35-45% of total mass), followed by lesser percentages for 

2.5-10 μm (0.3-0.4% of total mass), and < 2.5 μm (~ 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 μm) and fine particles (< 2.5 μm) 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 (μg/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 μg/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 

DRAFT--DO NOT QUOTE OR CITE 29 October 2002 
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 μg/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 μg/m3) to perhaps hundreds of milligrams per cubic 

meter (> 100,000 μg/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 μg/m3

 during most of September 11 and 12. However, hourly PM2.5 concentrations did 

increase to the 50-100 μg/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 eastnortheast 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 PM2.5 

levels at PS 64 and PS 199 (reaching 166 and 100 μg/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 μg/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 μg/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 μg/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 

DRAFT--DO NOT QUOTE OR CITE 30 October 2002 
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 PM2.5 NAAQS 

level (65 μg/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 AQI LOC of 40 μg/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 μg/m3

 (daily PM2.5 NAAQS level) only once, on October 4; and the 24-h AQI LOC (40 

μg/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 μg/m3 on October 3-4, but 24-hour PM2.5 values dropped off to 90 μg/m3 at the 

290 Broadway site several blocks northeast of WTC and to 53 μg/m3 at PS 64 about 1.5 km 

further to the northeast of WTC Ground Zero and only reached 60 μg/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 μg/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 

DRAFT--DO NOT QUOTE OR CITE 31 October 2002 
the 40 μg/m3

 AQI LOC value; many of the 24-hour PM2.5 levels for such sites were below 20 

μg/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 μg/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 μg/m3

 at some sites in early October to 

generally less than 50 μg/m3 in November (except for ~114-135 μg/m3 on October 25-26 for 

Park Row and 55-75 μg/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 μg/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 μg/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 μm. 

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 

DRAFT--DO NOT QUOTE OR CITE 32 October 2002 
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 

DRAFT--DO NOT QUOTE OR CITE 33 October 2002 
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 PM2.5 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 SO2 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 

DRAFT--DO NOT QUOTE OR CITE 34 October 2002 
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 (41X), 

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 μm on the morning of October 3, as shown in Figure 19. This very brief excursion 

DRAFT--DO NOT QUOTE OR CITE 35 October 2002 
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 μg/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 μm) and, possibly, inferred ultrafine (< 0.01 μm) PM size ranges (silicon 

otherwise typically being mainly associated with coarse fraction particles > 2.5 μm). 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. 

DRAFT--DO NOT QUOTE OR CITE 36 October 2002 
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 μg/m3), for both fine (PM < 2.5 μm 

diameter) and coarse (PM > 2.5 μm) 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 μm) 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) 

DRAFT--DO NOT QUOTE OR CITE 37 October 2002 
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 μg/m3

 at PS 64 

on 9/13) and in Queens (100 μg/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 AQI 40 μg/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 

DRAFT--DO NOT QUOTE OR CITE 38 October 2002 
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 SO2. 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 μg/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 μg/m3 (sometimes reaching hourly peaks of 

6000 μg/m3 or more) on 3 to 5 consecutive days in the presence of 1000-4000 μg/m3 of SO2. 

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 μg/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 μg/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 PM2.5 values ranged from 35.4 to 43.3 

μg/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 μg/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 μg/m3 during October and mostly 

below 50 μg/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 μg/m3

 and from 51-121 μg/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 

DRAFT--DO NOT QUOTE OR CITE 39 October 2002 
network, concentrations of PM2.5 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 PM2.5 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 

DRAFT--DO NOT QUOTE OR CITE 40 October 2002 
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 WTCderived 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 μg/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 μg/m3

. However, a 

dose equivalent to a human exposure of 130 μg/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). 

DRAFT--DO NOT QUOTE OR CITE 41 October 2002 
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. 

DRAFT--DO NOT QUOTE OR CITE 42 October 2002 
Table 2. Concentrations (maximum and Sept-Oct average) of PM2.5 and Component Elements Measured at the E

World Trade Center Perimeter Sites and at Four Other Sites in the Northeast U.S. (PM2.5 concentrations in μg/m3

components in ng/m3). 

WTC Max. (Site, Date) WTC Average Sept-Oct1 NYU Med. Ctr.2 Bronx, NY3 Boston, 

A C K Aug '76 Feb-June '00 Feb-Jun

PM2.5 400 (A, 10/4) 85 34 50 81.74 12.5 10.7 

Na 870 (A, 10/4) 273 157 169 570 72 178 

Mg 490 (K, 11/13) 101 67 79 103 4.8 16 

Al 670 (A, 10/20) 198 74 113 187 9.2 25 

Si 20000 (A, 10/4) 943 224 333 75 92 S 23000 (A, 10/3) 4796 1808 2524 6820 1200 933 

Cl 45000 (A, 10/4) 7247 540 845 119 9.8 68 

K 5600 (A, 9/22) 988 147 260 194 38 38 

Ca 4900 (A, 10/11) 1304 345 749 38 50 Cr 34 (C, 11/19) 5 4 3 28 0.3 0.5 

Fe 9400 (K, 12/12) 1745 904 975 400 91 76 

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 Cu 2800 (A, 9/22) 435 59 92 2.8 2.2 

Zn 10000 (A,10/4) 1526 164 307 224 21 9.7 

As 1100 (K, 11/14) 9 bdl bdl 3 1.1 0.9 Br 5700 (A, 9/20) 800 82 124 133 2.5 2.5 

Pd 900 (A, 10/4) 132 2 7 

Cd 150 (A, 9/22 & 10/4) 33 9 9 7.7 1.7 1.7 

Sb 350(A, 9/22) 50 2 1 11 3.6 2.4 Pb 5500 (A, 9/22) 791 83 167 1170 4.2 3.4 

1A 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 measDRAFT--DO NOT QUOTE OR CITE 43 October 2002 
 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 th

dates of the measurements are shown in parenthesis. Nearly all elevated measurements were seen in Site A, and in late September, ear

below detection limit and n.a. = data not available. 2NY Summer Aerosol Study, 1976. 3Coutant et al., 2001. 4PM2.0 0.9 * PM2.5 (estim

DRAFT--DO NOT QUOTE OR CITE 44 October 2002 
A 

K C

PS 64 

• 

DOE 

• 

Key LetA = 

W

C = 

T

K = 

(as 

Figure 2. Particulate matter monitoring sites, including ORD surface sites (A, C, K) on the WTC perimeter, the 

Broadway, and NYSDEC sites located elsewhere.. 

DRAFT--DO NOT QUOTE OR CITE 45 October 2002 
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. 

DRAFT--DO NOT QUOTE OR CITE 46 October 2002 
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 μg/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 < one millionth of pollutant 

concentration at WTC source. 

Figure 6. Satellite photograph of the WTC plume lofting from Ground Zero at 11:43 a.m. EDT 

on September 12, 2001. Note the very concentrated vertical convection of dust/smoke particles 

upwards and the flow in a well-defined plume towards the S/SE. (Source: Mandatory credit: 

“spaceimaging.com”.) 

DRAFT--DO NOT QUOTE OR CITE 47 October 2002 
Figure 7. Increased hourly PM2.5 concentrations measured on September 12 and/or 13 at PS 64, PS 199, Maspe

274 to the E/SE of WTC, reflecting dispersal of newly formed fine particles from WTC fires and/or fine particles 

settled dust from initial collapse of WTC buildings. (PM2.5 data provided courtesy of NYSDEC). 

DRAFT--DO NOT QUOTE OR CITE 48 October 2002 
Figure 8. ORD-modeled WTC plume dispersion for September 13, 2001 at 9:00 a.m. Note the 

increased hourly PM2.5 concentrations depicted in red for PS 64 (166 μg/m3) and PS 199 (100 

μg/m3

) NYSDEC monitoring stations, consistent with the E/NE direction of the modeled plume 

dispersion and likely touchdown of the plume at those and intervening sites but not at sites 

further E, SE, or to the N. 

Figure 9. ORD-modeled WTC plume dispersion on September 14, 2001 at 12 noon, indicative 

of plume flow mainly out over New York Harbor. 

DRAFT--DO NOT QUOTE OR CITE 49 October 2002 
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”.) 

DRAFT--DO NOT QUOTE OR CITE 50 October 2002 
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. 

DRAFT--DO NOT QUOTE OR CITE 51 October 2002 
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 μg/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. 

DRAFT--DO NOT QUOTE OR CITE 52 October 2002 
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 μg/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 μg/m3) being evaluated for data quality are included in 

24-hr average calculation. 

DRAFT--DO NOT QUOTE OR CITE 53 October 2002 
 

Figure 14. ORD measurement of PM2.5 elemental constituents Ca, Si, and K at Ground Zero 

perimeter sites and 290 Broadway site. 

DRAFT--DO NOT QUOTE OR CITE 54 October 2002 
Figure 15. ORD measurements of PM2.5 elemental composition for S, Cl, and Br at Ground 

Zero perimeter sites and 290 Broadway site. 

DRAFT--DO NOT QUOTE OR CITE 55 October 2002 
Figure 16. ORD measurements of PM2.5 elemental constituents Pb, Cu, and Zn at Ground Zero 

perimeter sites and 290 Broadway site. 

DRAFT--DO NOT QUOTE OR CITE 56 October 2002 
Figure 17. ORD measurements of PM2.5 elemental constituents As, Pd, and Sb at Ground Zero 

perimeter sites and 290 Broadway site. 

DRAFT--DO NOT QUOTE OR CITE 57 October 2002 
Figure 18. ORD measurements of PM2.5 elemental constituents Ni, Cd, and Cr at Ground Zero 

perimeter sites and 290 Broadway site. 

DRAFT--DO NOT QUOTE OR CITE 58 October 2002 
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. 

DRAFT--DO NOT QUOTE OR CITE 59 October 2002 
IV.b. Metals 

IV.b.1. 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 μg/m3

 (90-day average). This level was 

set to reduce the risk of occurrence of lead intoxication impacts associated with prolonged lowlevel 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 μg/m3 or more 

were often detected in U.S. urban areas such as NYC. Currently, 24-hour ambient air lead levels 

below 0.5 μg/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 μg/m3 for a Manhattan (Madison Ave.) curbside sampling site 

(maximum daily value = 0.34 μg/m3) and (b) arithmetic mean annual-average values ranging 

from 0.02 to 0.09 μg/m3

 for three Brooklyn/Staten Island sites (maximum daily value = 

0.63 μg/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 μg/g (ppm) in residential 

areas of NYC and Philadelphia and from 900 to 13,000 μg/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 μg/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 

DRAFT--DO NOT QUOTE OR CITE 60 October 2002 
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 μg/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 μg/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 μg/m3

; in 

fact, with very few exceptions, nearly all were below 0.5 μg/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 

μg/m3, 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 μg/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 μg/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/nycdisaster/map.html) do indicate that high air lead levels were detected on September 22 (69.3 

μg/m3, averaged over 4.5 hr) and September 23 (18.1 μg/m3, 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, torchcutter/burner) exceeded the OSHA Lead PEL (50 μg/m3

, 8-hr average) during late 

DRAFT--DO NOT QUOTE OR CITE 61 October 2002 
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 

μg/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 μg/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 μg/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. 

DRAFT--DO NOT QUOTE OR CITE 62 October 2002 
Figure 20. Ambient air lead concentrations (μg/m3

) at sites within Ground Zero or in lower 

Manhattan locations in immediate vicinity of the WTC. 

Source: EPA Region 2 

DRAFT--DO NOT QUOTE OR CITE 63 October 2002 
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 μg/m3 

(ATSDR, 2000c), and nickel concentrations in urban air range from 0.001 to 0.328 μg/m3 

(ATSDR, 1997b). 

To evaluate chromium and nickel, the OSHA PELs (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 μg/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 μg/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 μg/m3

), except for one 

higher reading at 0.22 μg/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 

DRAFT--DO NOT QUOTE OR CITE 64 October 2002 
in sampling. Measurements were mostly non-detects in within Ground Zero and in all locations 

measuring nickel, with sporadic measurements all less 0.1 μg/m3

. 

DRAFT--DO NOT QUOTE OR CITE 65 October 2002 
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.1. 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 

DRAFT--DO NOT QUOTE OR CITE 66 October 2002 
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 

Aroclors1260, 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 

DRAFT--DO NOT QUOTE OR CITE 67 October 2002 
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 [μg/m3]

-1 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 (μg/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 μg/m3] * [30 days/ 

(70 years*365 d/yr)] * [1*10-4 (μg/m3)

-1] ). 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 x103 ng/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 

DRAFT--DO NOT QUOTE OR CITE 68 October 2002 
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 longterm 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. 

DRAFT--DO NOT QUOTE OR CITE 69 October 2002 
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 

DRAFT--DO NOT QUOTE OR CITE 70 October 2002 
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 

DRAFT--DO NOT QUOTE OR CITE 71 October 2002 
7 

10 

9 

8 6 

5 

12 4 

3 

2 

11 

1 

KEY 

(1) EPA Taga Lab 

(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 

Figure 21. Location of PCB monitoring stations. 

DRAFT--DO NOT QUOTE OR CITE 72 October 2002 
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 (Ci

) 

times its toxicity equivalency factor, or TEFi. 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, E(TEFi*Ci). 

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 

DRAFT--DO NOT QUOTE OR CITE 73 October 2002 
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.1. 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 onehalf the detection limit. 

DRAFT--DO NOT QUOTE OR CITE 74 October 2002 
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 = 1⁄2 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 = 1⁄2 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 = 1⁄2 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 

DRAFT--DO NOT QUOTE OR CITE 75 October 2002 
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. 

DRAFT--DO NOT QUOTE OR CITE 76 October 2002 
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: 

DRAFT--DO NOT QUOTE OR CITE 77 October 2002 
 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 

DRAFT--DO NOT QUOTE OR CITE 78 October 2002 
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 (EPA, 1997). 

3) 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/kgday]-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 wholeweight-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 

DRAFT--DO NOT QUOTE OR CITE 79 October 2002 
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. 

DRAFT--DO NOT QUOTE OR CITE 80 October 2002 
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 

DRAFT--DO NOT QUOTE OR CITE 81 October 2002 
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. 

DRAFT--DO NOT QUOTE OR CITE 82 October 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 = 1⁄2 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 

11/15b 5.4 (1.6) 11/15 3.4 (1.6) 11/22 1.30 

11/21b 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 = 1⁄2 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 = 1⁄2 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. 

DRAFT--DO NOT QUOTE OR CITE 83 October 2002 
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 % 

1

This dissipation rate corresponds to a 7.1 year half-life in the body. 

DRAFT--DO NOT QUOTE OR CITE 84 October 2002 
2 

1 3 

4 

6 

7 

8 

5 

10 

12N 

11N 

9N 

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. 

DRAFT--DO NOT QUOTE OR CITE 85 October 2002 
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 μm. 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 μm. 

Fibers exceeding the diameter of 3 μm 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 exposureresponse 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.” 

DRAFT--DO NOT QUOTE OR CITE 86 October 2002 
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.1. 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 μm and has a magnification range of 100 - 400X. 

Fibrous structures are defined as particles exhibiting a length of > 5 μm 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 μm, 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 

DRAFT--DO NOT QUOTE OR CITE 87 October 2002 
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 μm with length >5 μm 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 CFR Part 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 

μm. 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 

DRAFT--DO NOT QUOTE OR CITE 88 October 2002 
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 

DRAFT--DO NOT QUOTE OR CITE 89 October 2002 
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*10-5 to 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 μm 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 μm 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, 

DRAFT--DO NOT QUOTE OR CITE 90 October 2002 
respectively. A few more stations were set up in public schools (Manhattan - PS143, Queens -

PS199, Brooklyn - PS274, Bronx - PS154, 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 

DRAFT--DO NOT QUOTE OR CITE 91 October 2002 
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 μm) 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 

DRAFT--DO NOT QUOTE OR CITE 92 October 2002 
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 shortand long-term health impacts were minimal during the unloading of debris at the site. 

DRAFT--DO NOT QUOTE OR CITE 93 October 2002 
Table 6. Locations and concentrations of asbestos exceeding the AHERA level of 70 S/mm2

. 

Location Date Concentration Date Conc 

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 (supply tent) Oct 20 72 Nov 9 80 

II. Lower Manhattan Locations 

250 South End Avenuea Sep 18 548 

Location A - Barclay St & West 

Broadway 

Sep 15 128 Sep 15 160 

Location B - Church St & Dey St Feb 11 213.33 

Location C - Liberty St & Trinity St Feb 5 88 

Location D - Albany St & Greenwich 

St 

Sep 27 97.78 Dec 27 204.44 

Sep 30 88.88 

Location E - Liberty St & South End 

Ave 

Sep 16 90 Sep 30 80 

Location F - Vesey St & West St Sep 27 71.11 

DRAFT--DO NOT QUOTE OR CITE 94 October 2002
Table 6. Locations and concentrations of asbestos exceeding the AHERA level of 70 S/mm2 (cont’d). 

Description Date Conc Date Conc 

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. 

DRAFT--DO NOT QUOTE OR CITE 95 October 2002 
Figure 23. Location of asbestos monitoring stations in Lower Manhattan. 

DRAFT--DO NOT QUOTE OR CITE 96 October 2002 
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). 

DRAFT--DO NOT QUOTE OR CITE 97 October 2002 
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) 

DRAFT--DO NOT QUOTE OR CITE 98 October 2002 
Figure 27. NorthwestSoutheast directional 

analysis for asbestos TEM 

weekly maximums (taken 

from EPA, 2002a). 

Figure 28. NortheastSouthwest directional 

analysis for asbestos TEM 

weekly maximums (taken 

from EPA, 2002a). 

DRAFT--DO NOT QUOTE OR CITE 99 October 2002 
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) 

DRAFT--DO NOT QUOTE OR CITE 100 October 2002 
Figure 31. Northwest-Southeast 

directional analysis for asbestos 

TEM weekly maximums (taken 

from EPA, 2002a). 

Figure 32. NortheastSouthwest directional analysis 

for asbestos TEM weekly 

maximums (taken from EPA, 

2002a). 

DRAFT--DO NOT QUOTE OR CITE 101 October 2002 
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. Freon22 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.1. 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 

DRAFT--DO NOT QUOTE OR CITE 102 October 2002 
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 

DRAFT--DO NOT QUOTE OR CITE 103 October 2002 
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 byproduct 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 

DRAFT--DO NOT QUOTE OR CITE 104 October 2002 
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 

DRAFT--DO NOT QUOTE OR CITE 105 October 2002 
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 

DRAFT--DO NOT QUOTE OR CITE 106 October 2002 
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). 

DRAFT--DO NOT QUOTE OR CITE 107 October 2002 
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). 

DRAFT--DO NOT QUOTE OR CITE 108 October 2002 
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 shortterm 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 EPASTSC 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 

DRAFT--DO NOT QUOTE OR CITE 109 October 2002 
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. 

DRAFT--DO NOT QUOTE OR CITE 110 October 2002 
Table 7. VOC sampling locations outside of Ground Zero. 

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 Site C’ 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 Sept 12-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 Sept 16-Sept 27 2 

Loc K Albany & West Sept 23-Sept 25 2 

Loc N Pier 25 (southside) Oct 13 1 

Loc P Albany & South End Sept 27 1 

Number of 

Samples Taken 

Sampling Dates 

for Benzene 

Site Name Street Location 

DRAFT--DO NOT QUOTE OR CITE 111 October 2002 
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 Pl & 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 Pl (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 

DRAFT--DO NOT QUOTE OR CITE 112 October 2002 
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 

DRAFT--DO NOT QUOTE OR CITE 113 October 2002 
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 

ATSDR 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 

1

NIOSH (2002) 

2

ATSDR (1994) 

DRAFT--DO NOT QUOTE OR CITE 114 October 2002 
Table 10. Benzene grab sample exceedences and 24-hour sample monitoring summary. 

OSHA PEL 1 ppm1 

OSHA STEL 5 ppm1 

11 ppm 

19 ppm 

49 ppm 

1.3 ppm 

Liberty and Trinity Sept 26 

Greenwich and Liberty Sept 28 

Greenwich and Liberty Sept 28 

Greenwich and Liberty Oct 1 

Yes 

Yes 

Yes 

Yes 

ATSDR Acute MRL 

0.05 ppm2 

0.1 ppm Greenwich and Liberty Sept 27 

samples noted above also exceed 

the ATSDR acute MRL 

Yes 

ATSDR Intermediate 

MRL 0.004 ppm2 

0.011 ppm 

0.024 ppm 

0.026 ppm 

0.007 ppm 

0.012 ppm 

0.008 ppm 

0.016 ppm 

0.008 ppm 

0.005 ppm 

0.007 ppm 

0.0043 ppm 

0.005 ppm 

0.021 ppm 

0.007 ppm 

0.024 ppm 

0.008 ppm 

0.008 ppm 

W. Broadway and Park Pl. Sept 22 

W. Broadway and Park Pl. Sept 25 

W. Broadway and Park Pl. Oct 3 

W. Broadway and Park Pl. Oct 9 

W. Broadway and Park Pl. Oct 19 

W. Broadway and Park Pl. Oct 20 

W. Broadway and Park Pl. Oct 21 

W. Broadway and Park Pl. Oct 24 

290 Broadway Sept 25 

290 Broadway, Sept 26 

290 Broadway, Sept 27 

290 Broadway Oct 11 

Broadway and Liberty Sept 23 

Broadway and Liberty Oct 8 

Albany and West Sept 30 

Albany and West Oct 1 

Albany and West Oct 20 

Yes 

Yes 

Border 

Border 

Border 

Border 

Border 

Border 

No 

No 

No 

No 

Yes 

Yes 

Yes 

Yes 

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 

DRAFT--DO NOT QUOTE OR CITE 115 October 2002 

I. Grab Samples 

Exceedence Location and Date 

Exceedence 

Concentration 

Benzene 

Screening 

Benchmarks 

Restricted 

Zone 
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 

<0.0007 

<0.0007 

0.0007 

0.0007 

Sep 27 

Sep 27 

Dec 3 

Dec 10 

Dec 17 

1

NIOSH (2002) 

2

ATSDR (1997) 

DRAFT--DO NOT QUOTE OR CITE 116 October 2002 
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 

1

NIOSH (2002) 

DRAFT--DO NOT QUOTE OR CITE 117 October 2002 
Table 12. Chloromethane grab sample exceedences monitoring summary. 

EPA (1998) 

Chloromethane 

Screening 

Benchmarks 

Exceedence 

Concentration Exceedence Location and 

Date 

Restricted 

Zone 

OSHA PEL 100 ppm1 None 

ATSDR 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 

Subchronic RfC 0.14 

ppm3 

same as above 

1

NIOSH (2002) 

2

ATSDR (1998) 

3

DRAFT--DO NOT QUOTE OR CITE 118 October 2002 
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 

1

NIOSH (2002) 

2

ATSDR (1999) 

3

EPA (1999a) 

DRAFT--DO NOT QUOTE OR CITE 119 October 2002 
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 

ATSDR 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 

Subchronic 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 

1

NIOSH (2002) 

2

ATSDR (2002b) 

3

EPA (1999b) 

DRAFT--DO NOT QUOTE OR CITE 120 October 2002 
13 = Albany & South End 

14 = Liberty & South End 

15 = Vessey & West 

16 = 130 West (Verizon bldg) 

17 = Murray St (between 

West & North End) 

18 = Rockefeller Park 

19 = EPA Taga Bus 

20 = Barclay & West Broadway 

21 = Pier 25 

22 = Murray & West Broadway 

23 = 75 Park Place & Greenwich 

24 = Church & Vessey 

25 = Park Row & Spruce 

26 = Park Row 

27 = 290 Broadway 

28 = West Broadway and Park Place 

13 = Albany & South End 

14 = Liberty & South End 

15 = Vessey & West 

16 = 130 West (Verizon bldg) 

17 = Murray St (between 

West & North End) 

18 = Rockefeller Park 

19 = EPA Taga Bus 

20 = Barclay & West Broadway 

21 = Pier 25 

22 = Murray & West Broadway 

23 = 75 Park Place & Greenwich 

24 = Church & Vessey 

25 = Park Row & Spruce 

26 = Park Row 

27 = 290 Broadway 

28 = West Broadway and Park Place 

1 

3 

6 7 

8 

9 10 

14 

12 

2 

15 16 

19 

17 

20 

13 

18 

25 

21 

22 

27 

26 

4 

5 

11 

23 

24 28 

Key 

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 y & West 

11 

12 = Rector & South End 

= Libert

= 225 Rector Place 

Figure 33. Location of VOC monitoring stations outside Ground Zero. 

Key 

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 

DRAFT--DO NOT QUOTE OR CITE 121 October 2002 
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 dioxinlike 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 

DRAFT--DO NOT QUOTE OR CITE 122 October 2002 
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. 

DRAFT--DO NOT QUOTE OR CITE 123 October 2002 
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/mm2 

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/mm2 

. 

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/mm2

 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/mm2

, but no measurements after 9/30 

above 50 S/mm2 

Asbestosa , 

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 Fultonc 9/15 

0.030 Fultonc 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, μg/m3 4.3 Barclay/W. Broadway 9/23 

2.8 Barclay/W. Broadway 9/27 

One sample > 1.0 μg/m3

 on 10/4, otherwise, all samples < 

0.6 μg/m3

; samples through 2/5/02 

1.9 Church/Dey 9/18 

1.7 Church/Dey 9/23 

all other < 0.7 μg/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.

DRAFT--DO NOT QUOTE OR CITE 124 October 2002 
 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. 

VI.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. 

VI.a.1. 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 

DRAFT--DO NOT QUOTE OR CITE 125 October 2002 
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. NIOSH Data 

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, FreonTM-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 

DRAFT--DO NOT QUOTE OR CITE 126 October 2002 
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.” 

V1.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 

DRAFT--DO NOT QUOTE OR CITE 127 October 2002 
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. 

VI.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. 

VI.b.1. 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 < 

DRAFT--DO NOT QUOTE OR CITE 128 October 2002 
.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 (79%) 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 

μg/m3

J], calcite [ND-14 μg/m3J], and portlandite [ND-95 μg/m3J]) and mineral components of 

building wallboard (gypsum [4-15 μg/m3J] and mica [ND-43 μg/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 μg/m3

J, calcite up to 6 μg/m3J, 

portlandite up to 30 μg/m3

J, gypsum up to 6 μg/m3J, and mica up to 17 μg/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 31%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 

DRAFT--DO NOT QUOTE OR CITE 129 October 2002 
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 

DRAFT--DO NOT QUOTE OR CITE 130 October 2002 
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/ATSDR, 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; 

DRAFT--DO NOT QUOTE OR CITE 131 October 2002 
• 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 byproducts, 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. 

DRAFT--DO NOT QUOTE OR CITE 132 October 2002 
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 μm) and also by 

PCME (fibers >5 μm). 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 μm 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 μm. 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 μm. 

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. 

DRAFT--DO NOT QUOTE OR CITE 133 October 2002 
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 μg/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 

μg/m3

) but few exceeded the 24 hour standard of 65 μg/m3. 

DRAFT--DO NOT QUOTE OR CITE 134 October 2002 
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 

DRAFT--DO NOT QUOTE OR CITE 135 October 2002 
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 μg/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. 

DRAFT--DO NOT QUOTE OR CITE 136 October 2002 
• 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. 

DRAFT--DO NOT QUOTE OR CITE 137 October 2002 
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ATSDR (2000a). Toxicological Profile for Polychlorinated Biphenyls (PCBs). Agency for 

Toxic Substances and Disease Registry, U.S. Department of Health and Human Services, 

Atlanta, Georgia. 

ATSDR (2000b). Toxicological Profile for Toluene. Agency for Toxic Substances and Disease 

Registry U.S. Department of Health and Human Services, Atlanta, Georgia. 

ATSDR (2000c). Toxicological Profiles for Chromium. Agency for Toxic Substances and 

Disease Registry, U.S. Department of Health and Human Services, Atlanta, Georgia. 

ATSDR (1999) Toxicological Profile for Ethylbenzene. Agency for Toxic Substances and 

Disease Registry, U.S. Department of Health and Human Services, Atlanta, Georgia. 

ATSDR (1998). Toxicological Profile for Chloromethane. Agency for Toxic Substances and 

Disease Registry, U.S. Department of Health and Human Services, Atlanta, Georgia. 

ATSDR (1997a) Toxicological Profile for Benzene. Agency for Toxic Substances and Disease 

Registry, U.S. Department of Health and Human Services, Atlanta, Georgia. 

ATSDR (1997b) Toxicological Profile for Nickel. Agency for Toxic Substances and Disease 

Registry, U.S. Department of Health and Human Services, Atlanta, Georgia. 

ATSDR (1994). Toxicological Profile for Acetone. Agency for Toxic Substances and Disease 

Registry, U.S. Department of Health and Human Services, Atlanta, Georgia. 

ATSDR (1993). Toxicological Profile for 1,3-Butadiene. Agency for Toxic Substances and 

Disease Registry, U.S. Department of Health and Human Services, Atlanta, Georgia. 

Bernstein, D. M.; Rahn, K. A. (1979) New York Summer Aerosol Study: trace element 

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Brown DP, Dement JM, Okun A. (1994) Mortality patterns among female and male chrysotile 

asbestos textile workers. J Occup Med 36:882-888. 

Cahill, T. A.; Cliff, S. S.; Jimenez-Cruz, M.; Shackelford, J. F.; Dunlap, M.; Kelly, P.; Riddle, 

S.; Selco, J.; Bench, G.; Grant, P.; Ueda, D.; Perry, K. D.; Leifer, R. Z. (2002) Analysis of 

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dust/smoke aerosol that settled east of the World Trade Center (WTC) in lower Manhattan after 

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of Health and Human Services, Atlanta, GA. 

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Pacific Grove, CA, 502 pp. 

US EPA (2002a). Environmental Data Trend Report World Trade Center Disaster. Final 

Update - Trends for Data Collected from 9/11/01 to 4/24/02 from Lower Manhattan. Prepared 

by, Quality Assurance Technical Support Laboratory, IT Corporation, 2700 Chandler Avenue, 

Las Vegas, Nevada 89120. May 1, 2002. Contract Number: 68-W-01-010. Prepared for, Office 

of Emergency and Remedial Response, U.S. Environmental Protection Agency, Washington, 

D.C. 20460. 

US EPA (2002b). Personal communication, Region 2 to National Center for Environmental 

Assessment, Office of Research and Development, US EPA, in January 2002. Spreadsheet 

titled, “Background Conc kf 02 12-20-01" displaying background concentrations for several 

contaminants of interest, and minimal information on references for said concentrations - date(s) 

and general location measured only. 

US EPA (2002c). Toxicological effects of fine particulate matter derived from the destruction of 

the World Trade Center. United States Environmental Protection Agency, Office of Research 

and Development, National Health and Environmental Effects Research Laboratory, Research 

Triangle Park, NC. September, 2002. EPA/600/R-02/028. 

US EPA (2000). Exposure and Human Health Reassessment of 2,3,7,8-Tetrachlorodibenzo-pDioxin (TCDD) and Related Compounds. United States Environmental Protection Agency, 

Office of Research and Development, National Center for Environmental Assessment. Review 

Draft. September, 2000. EPA/600/P-00/001B(a-f). Available at, http://www.epa.gov/ncea. 

US EPA (1999a). EPA Superfund Technical Support Center Risk Assessment Issue Paper for: 

Derivation of a Subchronic RfC for Ethylbenzene Draft, 99-011/10-12-99. 

US EPA (1999b). EPA Superfund Technical Support Center Risk Assessment Issue Paper for: 

Deriving a Provisional Subchronic Inhalations RfC for Toluene, Draft. 98-031/07-19-99. 

US EPA (1998). EPA Superfund Technical Support Center Risk Assessment Issue Paper for: 

Derivation of the Inhalations Toxicity and an Evaluation of the Oral Toxicity of Chloromethane 

Draft, 98-022/6-14-99. 

DRAFT--DO NOT QUOTE OR CITE 141 October 2002 
US EPA (1997a) Exposure Factors Handbook. United States Environmental Protection 

Agency. National Center for Environmental Assessment, Office of Research and Development, 

US Environmental Protection Agency. 1997. EPA/600/P-95/002F(a-c). 

US EPA. (1997b). Region III. Hazard Evaluation Handbook. A Guide to Removal Actions. 

EPA 903/B-97-006. 

US EPA. (1996) Urban soil lead abatement demonstration project. Volume I: EPA integrated 

report. Research Triangle Park, NC: Office of Research and Development, National Center for 

Environmental Assessment; report no. EPA/600/P-93/001aF. Available from: NTIS, Springfield, 

VA; PB96-168356. 

US EPA. (1989) Interim procedures for estimating risks associated with exposures to mixtures 

of chlorinated dibenzo-p-dioxins and -dibenzofurans (CDDs and CDFs) and 1989 update. 

United States Environmental Protection Agency, Washington, DC. Risk Assessment Forum. 

EPA/625/3-89/016. 

US EPA. (1987) Asbestos-Containing Materials in Schools; Final Rule and Notice. 40 CFR Part 

763. Federal Register, Vol 52 (210): 41826-41905. October 30, 1987. 

US EPA. (1986a) Second addendum to air quality for particulate matter and sulfur oxides 

(1982): assessment of newly available health effects information. Research Triangle Park, NC: 

Office of Health and Environmental Assessment, Environmental Criteria and Assessment Office; 

EPA report no. EPA-600/8-86-020F. Available from: NTIS, Springfield, VA; PB87-176574. 

US EPA. (1986b) Air quality criteria for lead: volume II. Research Triangle Park, NC: Office of 

Health and Environmental Assessment, Environmental Criteria and Assessment Office; report 

no. EPA-600/8-83/028bF. Available from: NTIS, Springfield, VA; PB87-142394. 

US EPA (1986c) Airborne asbestos health assessment update. United States Environmental 

Protection Agency, Office of Health and Environmental Assessment. EPA/600/8-84/003F. 

US EPA. (1984) Risk Analysis of TCDD Contaminated Soil. U.S. Environmental Protection 

Agency, Office of Health and Environmental Assessment. EPA-600/8-84-031. 

US EPA. (1982) Air quality criteria for particulate matter and sulfur oxides. Research Triangle 

Park, NC: Office of Health and Environmental Assessment, Environmental Criteria and 

Assessment Office; EPA report no. EPA-600/8-82-029aF-cF. 3v. Available from: NTIS, 

Springfield, VA; PB84-156777. 

USGS. 2002. U. S. Geological Survey Open File Report OFR-01-0429. Environmental Studies 

of the World Trade Center area after the September 11, 2001 attack. Denver, CO: U. S. 

Geological Survey. Available: http://geology.cr.usgs.gov/pub/open-file-reports/ofr-01-0429/ 

[accessed 6 July 2002]. 

DRAFT--DO NOT QUOTE OR CITE 142 October 2002 
Van den Berg ML, Birnbaum L, Bosveld ATC, Brunstrom B, Cook P, Feeley M, Giesy JP, 

Hanberg A, Hasegawa R, Kennedy SW, Kubiak T, Larsen JC, van Leeuwen FXR, Liem AKD, 

Nolt C, Peterson RE, Poellinger L, Safe S, Schrenk D, Tillitt D, Tysklind M, Younes M, Warn 

F, Zacharewski T. Toxic Equivalency Factors (TEFs) for PCBs, PCDDs, PCDFs for Humans 

and Wildlife. Environmental Health Perspectives, 1998; 106: 775. 

Vette, A.; Landis, M.; Williams, R.; Webb, L.; Ellestad, T.; Vallero, D. (2002) Concentrations 

and composition of PM at Ground Zero and lower Manhattan after September 11, 2001. In 

preparation. 

Walker Y, Lorber M, Wang V, Gillooly P. 2002. Impacts of dioxin emissions from the 

Shinkapo Incinerator to the United States Naval Air Facility at Atsugi, Japan. Part 2: Air 

impacts. Organohalogen Compounds 56:481-484. 

WHO 1998. Chrysotile asbestos: Environmental Health Criteria. Geneva: Switzerland: World 

Health Organization. 

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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

DRAFT--DO NOT QUOTE OR CITE A-1 October 2002 
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 μg/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 

DRAFT--DO NOT QUOTE OR CITE A-2 October 2002 
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 μg/m3 .2 μg/m3 (9) 

3 μg/m3 (5) 

Chromium (4) 100 μg/m3 .6 μg/m3 (5) 

Lead 50 μg/m3 1.5 μg/m3 (7) 

Manganese 5 mg/m3 .5 μg/m3 (6) 

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Contaminant Site Worker (1) Resident (2) 

Sulfur Dioxide 5 ppm .14 ppm (7) 

Particulates 

Total 15,000 μg/m3 NA 

Respirable 5,000 μg/m3 NA 

PM2.5 NA 40 μg/m3 (8) 

65 μg/m3 (7) 

PM10 NA 150 μg/m3 (7,8) 

Semivolatiles 

Dioxin/Furans (TEQ) NA .162 ng/m3 (5) 

PCBs 1,000 μg/m3 .73 μg/m3 (6) 

9 μg/m3 (5) 

PAHs (16) NA 6 μg/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 methylstyrene 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 μm length) per cubic centimeter of air

S/mm2 = structures (>.5 μm length) per square millimeter of filter paper

ppm = parts per million in air

μg/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 

DRAFT--DO NOT QUOTE OR CITE A-5 October 2002 
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) 

DRAFT--DO NOT QUOTE OR CITE A-6 October 2002 
APPENDIX B - TABLE OF MONITORING LOCATIONS

DRAFT--DO NOT QUOTE OR CITE B-1 October 2002 
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 

L

I. EPA’s Environmental Response Team Lettered Sites Location A Barclay St & West 

Broadway 

Asbestos 2 - 12 hour samples daily 

Dioxins (2)/PCBs, PAHs, 

Metals, Silica 

8 hour sample twice per week 

Particulates, VOCs 24 hr. sample daily; grab (VOC) 

Location B Church St and Dey St Asbestos 2 - 12 hour samples daily 

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 

Dioxins (2)/PCBs, PAHs, 

Metals, Silica 

8 hour sample twice per week 

Particulates, VOCs 24 hr. sample daily; grab (VOC) 

Location C1 

(note: station C 

and C1 are 

“alternate” stations; see footnote 1) 

Broadway and Liberty 

St 

Asbestos 2 - 12 hour samples daily 

Dioxins (2)/PCBs, PAHs, 

Metals, Silica 

8 hour sample twice per week 

Particulates 24 hr. sample every 3rd day 

Location D Albany St & 

Greenwich St 

Asbestos 2 - 12 hour samples daily 

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 

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

I. EPA’s Environmental Response Team Lettered Sites (cont’d).

Location F Vesey St & West St Asbestos 2 - 12 hour samples daily Contract

Dioxins (2)/PCBs, 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
Table 1. Overview of monitoring locations and responsible parties (cont’d). 

Site Name Site Location Pollutants Measured Sampling Frequency 

L

I. EPA’s Environmental Response Team Lettered Sites (cont’d). Location S Rector Pl & South End 

Ave 

Asbestos 2 - 12 hour samples daily 

Dioxins (2)/PCBs, PAHs 

Metals, Silica 

8 hour sample twice per week 

Location T Pier 6 Heliport Asbestos 2 - 12 hour samples daily Location U Pier 6, Exit 2 Asbestos 2 - 12 hour samples daily Location V Pier 6, Bus Sign Asbestos 2 - 12 hour samples daily Location W Wash Tent, West Street 

& Murray 

Asbestos 2 - 12 hour samples daily 

WTC -Building 5 SW 

AKA, Location 3A Dioxins (2)/PCBs, PAHs, 

Metals, Silica 

8 hour sample twice per week 

WTC -Church & Vesey (alternate for WTC; see footnote 1) 

AKA, Location 3B Dioxins (2)/PCBs, PAHs, 

Metals, Silica 

8 hour sample twice per week 

S.I. Landfill 

Sites 

17 Landfill Sites + 3 

offsite locations 

Asbestos 1 - 12 hour sample daily 

5 Landfill Sites Total particulates 12 hour sample daily when temp. 

& humidity specs are met. 

On

2 Landfill Sites + 3 

Offsite Locations 

Metals 1 - 12 hour sample weekly 

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Table 1. Overview of monitoring locations and responsible parties (cont’d). 

Site Name Site Location Pollutants Measured Sampling Frequency 

L

II. Extended Monitoring Network- NYSDEC Numbered Air Monitoring Stations 

1 Park Row & Spruce 

Street, NY, NY 

Asbestos 12 hour sample daily 

Dioxin (1) 72 hour sample every 3 days 

VOC's 24 hr. sample every 3rd day 

Aldehydes 24 hr. sample every 3rd day 

PM Speciation 24 hr. sample every 3rd day 

PM Sizing continuous-by NYSDEC 

PM10, PM2.5 continuous- by NYSDEC PM 

P

2 Chambers St.& West 

St., 

NY, NY 

Asbestos 12 hour sample daily 

Dioxin (1) 72 hour sample every 3 days 

VOC's 24 hr. sample every 3rd day 

Aldehydes 24 hr. sample every 3rd day 

PM Speciation 24 hr. sample every 3rd day 

PM Sizing continuous-by NYSDEC 

PM10,PM2.5,PM continuous- by NYSDEC PM 

P

3 U.S. Coast Guard, 

1 South Street, 

NY, NY (Battery Pk) 

Asbestos 12 hour sample daily 

PM10, PM2.5 continuous- by NYSDEC PM 2

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Table 1. Overview of monitoring locations and responsible parties (cont’d). 

Site Name Site Location Pollutants Measured Sampling Frequency 

L

II. 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 

PM10, PM2.5 24 hour sample dailyby NYSDEC PM 2

5 PS 154, 333 East 35th 

Street, Bronx, NY 

10454 

PM2.5 continuous-by NYSDEC PM 

Asbestos 12 hour sample daily 

6 IS 143, 511 West 

182nd Street 

NY, NY 10033 

PM2.5 continuous-by NYSDEC PM 

Asbestos 12 hour sample daily 

7 PS 274, 800 Bushwick 

Ave, Brooklyn, NY 

11221 

PM2.5 continuous-by NYSDEC PM 

P

Asbestos 12 hour sample daily 

8 PS 44, 80 Maple 

Parkway, Staten Island, 

NY 10303 

PM2.5 continuous-by NYSDEC PM 

Asbestos 12 hour sample daily 

9 PS 199, 39-20 48th 

Ave, Long Island City, 

NY 11104 

PM2.5 continuous-by NYSDEC PM 

Asbestos 12 hour sample daily 

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Table 1. Overview of monitoring locations and responsible parties (cont’d). 

Site Name Site Location Pollutants Measured Sampling Frequency 

L

III. Extended Monitoring Network- NJDEP Air Monitoring Stations 

NJ-Shell West Avenue, Sewaren, 

NJ 

Asbestos 1 - 12 hour sample on Mon. and 

Thurs. 

NJ-Citgo Tremly Point Road, 

Linden, NJ 

Asbestos 1 - 12 hour sample on Mon. and 

Thurs. 

NJ-FMC Roosevelt Blvd., 

Cartaret, NJ 

Asbestos 1 - 12 hour sample on Mon. and 

Thurs. 

NJ-Liberty Liberty State Park, @ 

WTC Disaster Family 

Center 

Asbestos 1 - 12 hour sample on Mon. and 

Thurs. 

IV. Extended Monitoring Network- EPA/ORD Numbered Air Monitoring Stations 

14 Albany & West St 

NY, NY 

Dioxin (1) 72 hour sample every 3rd days 

PM Speciation 24 hr. sample every 3rd day 

PM Sizing continuous-by NYSDEC 

PM10, PM2.5 continuous-by NYSDEC PM 

P

VOCs 24 hr sample every 3rd day 

15 23 Wall Street, NY, 

NY 

PM10, PM2.5 continuous-by NYSDEC PM 

P

Aldehydes 24 hr. sample every 3rd day 

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Table 1. Overview of monitoring locations and responsible parties (cont’d). 

Site Name Site Location Pollutants Measured Sampling Frequency 

L

IV. Extended Monitoring Network- EPA/ORD Numbered Air Monitoring Stations (cont’d) 

16 290 Broadway 

NY, NY 

PAHs & SVOCs 12 & 23 hour samples 

Particulates continuous 

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 Environmental Response Team and are included here. - The New Jersey Department of Environmental Protection (NJDEP) site names were designated by NJD- Locations C (Liberty & Trinity) and C1 (Liberty and Broadway), and 3 (WTC Building 5) and 3A (Chu“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, 20was 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 (D

personnel and analyzed by Region 7. 

- Dioxin (2) = 8-hr samples collected by EPA Emergency and Remedial Response Division (ERRD) Reganalyzed 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 Resear

(NERL), in Research Triangle Park, North Carolina. 

- Region 7 = Regional Laboratory Branch, in the Environmental Services Division (ESD) in Region 7, K

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