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March 31, 2012

John Howard, M.D.

Administrator, World Trade Center Health Program

Centers for Disease Control and Prevention (CDC)

National Institute for Occupational Safety and Health (NIOSH)

395 E. St, S.W.

Suite 9200, Patriots Plaza

Washington, D.C. 20201

Dear Dr. Howard:

We are writing in response to your letter of October 5, 2011 requesting advice from the World 

Trade Center (WTC) Health Program Scientific/Technical Advisory Committee (STAC) on whether to add 

cancer, or a certain type of cancer, to the List of World Trade Center (WTC)-Related Health Conditions in 

the James Zadroga Act (“List”).

The STAC has reviewed available information on cancer outcomes that may be associated with 

the exposures resulting from the September 11, 2001 terrorist attacks, and believes that exposures 

resulting from the collapse of the buildings and high-temperature fires are likely to increase the 

probability of developing some cancers. This conclusion is based primarily on the presence of 

approximately 70 known and potential carcinogens in the smoke, dust, volatile and semi-volatile 

contaminants identified at the World Trade Center site (Table 1). Fifteen of these substances are 

classified by the International Agency for Research on Cancer (IARC) as known to cause cancer in 

humans, and 37 are classified by the National Toxicology Program (NTP) as reasonably anticipated to 

cause cancer in humans; others are classified by IARC as probable and possible carcinogens. Many of 

these carcinogens are genotoxic and it is therefore assumed that any level of exposure carries some risk.

Exposure data are extremely limited. No data were collected in the first 4 days after the attacks, 

when the highest levels of air contaminants occured, and the variety of samples taken on or after 

September 16, 2001 are insufficient to provide quantitative estimates of exposure on an individual or 

area level. However, the committee considers that the high prevalence of acute symptoms and chronic 

conditions observed in large numbers of rescue, recovery, clean up and restoration workers and 

survivors, as well as qualitative descriptions of exposure conditions in downtown Manhattan, represent 

highly credible evidence that significant toxic exposures occurred. Furthermore, the salient biological 

reaction that underlies many currently recognized WTC health conditions—persistent inflammation—is 

now believed to be an important mechanism underlying cancer through generating DNA-reactive 

substances, increasing cell turnover, and releasing biologically active substances that promote tumor 
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growth, invasion and metastasis. Given that cancer latencies for solid tumors average 20 years or more, 

it is noteworthy that the published FDNY study of fire fighters showed a statistically significant excess in 

all-site cancer with only 7 years of follow-up.

The committee deliberated on whether to designate all cancers as WTC-related conditions or to 

list only cancers with the strongest evidence. Some members proposed to include all cancers based on 

the incomplete and limited epidemiological data available to identify specific cancers, and others argued 

for the alternative of listing specific cancers based on best available evidence. The committee agreed to

proceed by generating a list of cancers potentially related to WTC exposures based on evidence from 

three sources described below:

(1) cancers with limited or sufficient evidence in humans based on the International Agency for 

Research (IARC) Monographs reviews for carcinogens present at the WTC site (Table 2); 

(2) cancers arising in regions of the respiratory and digestive tracts where WTC-related 

inflammatory conditions have been documented (Table 3); and 

(3) cancers for which epidemiologic studies have found some evidence of increased risk in WTC 

responder and survivor populations (Table 4).

The organ sites identified from any of the three sources are listed in Table 4. The committee 

reviewed the evidence summarized for each organ site or site grouping in Table 4 to develop its 

recommendation on which sites should be listed as WTC-related conditions. In addition, the committee 

considered the evidence for inclusion of several sites that were not identified from Table 4.

The committee recommends listing the following site groupings and sites as WTC-related 

conditions based on the strength of the evidence summarized in Table 4 and/or additional information 

provided below. 

 The committee recommends that malignant neoplasms of the respiratory system (including nose, 

nasal cavity and middle ear (ICD-O-3 site codes C300-C301, C310-319), larynx C320-C329), lung and 

bronchus (CC340-C349), pleura (C384), trachea, mediastinum and other respiratory organs (C339, 

C381-C383, C388, C390, C398, C399)) be listed as WTC-related conditions. These cancers are 

associated with exposure to many carcinogenic agents of concern at the WTC, including arsenic, 

asbestos, beryllium, cadmium, chromium, nickel, silica dust and soot. The respiratory tract is also

the major site for acute and chronic toxicity resulting from WTC-exposures, including chronic

nasopharyngitis, upper airway hyperreactivity, chronic laryngitis, interstitial lung disease, “chronic 

respiratory disorder – fumes/vapors”, reactive airways disease syndrome (RADS) and chronic cough 

syndrome. Although the Zeig-Owens study1did not find evidence for an increased risk of lung or 
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other respiratory cancers among FDNY firefighters, both internal and external comparisons may 

have been affected by greater declines in smoking among WTC-exposed firefighters (due in part to 

their respiratory symptoms) than unexposed firefighters or the general public. Commendably, in 

2002 a joint labor-management initiative offered a comprehensive voluntary smoking cessation 

program free of charge to FDNY smokers and family members2. Smoking cessation reduces lung 

cancer rates within 5–10 years after quitting. Thus, any increased risk of lung cancer associated 

with WTC exposures may have been obscured by lower rates of smoking-related lung cancer. 

 The committee recommends that certain cancers of the digestive system, including esophagus

(C150-C159), stomach (CC160-C169), colon and rectum (C180-189, C260, C199, C209), liver and 

intrahepatic bile duct (C220-CC221), retroperitoneum, peritoneum, omentum and mesentery 

(C480-C482, C488) be listed as WTC-related conditions. Esophageal cancer is associated with 

tetrachloroethylene, stomach cancer is associated with asbestos and inorganic lead compounds,

and colorectal cancer is associated with asbestos (Table 4). Cancer of the liver has been associated 

with vinyl chloride, arsenic and inorganic arsenic compounds, polychlorinated biphenyls, and 

trichloroethylene (Table 4). Gastrointestinal reflux disease (GERD) is associated with cancer of the 

esophagus, especially if it progresses to Barrett esophagus. Since cancer of the distal esophagus,

gastroesophageal junction and gastric cardia share common risk factors, Table 4 shows GERD as a 

WTC-related condition for stomach as well as esophageal cancer. The Zeig-Owens study1found 

evidence of an increased risk of stomach (including gastro-esophageal junction) and colorectal 

cancer among FDNY firefighters.

 The committee recommends that cancers of the oral cavity and pharynx, including lip (C000-C009), 

tongue (C019-C029), salivary gland (C079-C089), floor of mouth (C040-C049), gum and other mouth 

(C030-C039, C050-C059, C060-C069), nasopharynx (C110-C119), tonsil (C090-C099), oropharynx 

(C100-C109), hypopharynx (C129, C130-C139) and other oral cavity and pharynx (C140-C148) be 

listed as WTC-related conditions. IARC has found limited evidence that asbestos causes pharyngeal 

cancer in humans and sufficient evidence that formaldehyde causes cancer of the nasopharynx. The 

lip, oral cavity and pharynx are areas with high potential for direct exposure to toxic materials 

through hand-to-mouth contact. 

 The committee recommends that soft tissue sarcomas (C380, C470-C479, C490-C499) be listed as 

WTC-related conditions. IARC has found limited evidence for increased risk of soft tissue sarcoma 

associated with exposure to polychorophenols and their sodium salts and 2,3,7,8-TCDD. Soft tissue 
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sarcoma rates are very low in the general population (age-adjusted incidence rate approximately 3 

per 100,000) and therefore excesses are difficult to detect in epidemiologic studies.

 The committee recommends that melanoma (C440-449) and non-melanoma skin cancers (C440-

C449), including scrotal cancer (C632), be listed as WTC-related conditions. According to IARC, skin 

cancer is associated with exposure to arsenic and inorganic arsenic compounds and soot (Table 4).

The Zeig-Owens study1found a statistically significant increase in melanoma among exposed 

firefighters compared to the general population; the Standardized Incidence Ratio (SIR) was slightly 

larger but not significant when compared to non-exposed firefighters. No adjustment for 

surveillance bias was reported for malignant melanoma, although early detection through medical 

surveillance is likely.

 The committee recommends that mesothelioma (ICD-O-3 histology 9050-9055) be listed as WTCrelated conditions. Asbestos exposure is the only known cause of mesothelioma, and 

mesotheliomas have been documented in association with very low levels of community or 

household contact with asbestos. Mesothelioma rates are very low in the general population (ageadjusted incidence rate approximately 1 per 100,000), and may have exceptionally long latency—

perhaps as much as 40 years—making excesses difficult to detect in epidemiologic studies.

 The committee recommends that cancer of the ovary (C569) be listed as a WTC-related condition.

IARC has found sufficient evidence that asbestos exposure causes ovarian cancer. The incidence of 

ovarian cancer is relatively low (age-adjusted incidence rate approximately 6 per 100,000 women) 

and therefore difficult to detect in epidemiologic studies.

 The committee recommends that cancers of the urinary tract, including urinary bladder (C670-679), 

kidney and renal pelvis (C649, C659), ureter (C669), and other urinary organs (C680-C689), be listed 

as WTC-related conditions. IARC found limited evidence that exposure to “arsenic and inorganic 

arsenic compounds” and “cadmium and cadmium compounds” causes kidney cancer, sufficient 

evidence that arsenic and inorganic arsenic compounds” cause cancer of the urinary bladder, and 

limited evidence that diesel engine exhaust and soot cause cancer of the urinary bladder.

Transitional cell cancers of the renal pelvis, ureter and urinary bladder have been associated with a 

number of occupational and environmental exposures.

 The committee recommends that cancer of the eye and orbit (C690-C699) be listed as a WTCrelated condition. Eye injuries were among the top three conditions treated formally in the first 

few days after 9/113and, including informal, ad hoc eye irrigations on-site, eye irritation by foreign 

bodies were by far the most common acute treatments. Including cancer of the eye and orbit is 
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consistent with including lip, skin and respiratory and digestive tract sites with direct dust and fume 

contact and irritation/inflammation related to WTC exposures. 

 The committee recommends that thyroid cancer (C739) be listed as a WTC-related condition. 

Thyroid cancer has not been associated with any of the agents known to be present at the WTC,

and the primary evidence for an excess in risk comes from the Zeig-Owens study1. In that study, 17 

thyroid cancers were observed and 6 expected based on national rates, yielding a statistically 

significant SIR of 3.07. The SIR was 5.21 and statistically significant compared with unexposed 

firefighters, and was 2.17 and significant after a two-year lag was applied. The magnitude of the SIR 

for thyroid cancer was relatively large, although the significance of this finding is tempered by the 

possibility that a 2-year lag may not fully account for medical surveillance bias.

 The committee recommends that lymphoma, leukemia and myeloma (see following link for ICDO-3 

site and histology codes: http://seer.cancer.gov/siterecode/icdo3_d01272003/) be listed as WTCrelated conditions. All lymphatic and hematopoietic cancers (LHC’s) are combined in this document 

because of variation in how these cancers have been classified and grouped in epidemiologic 

studies, inaccuracy of death certificate diagnosis for these cancers, and changes in clinical 

nomenclature over time. Various LHC’s have been associated in humans with exposure to benzene, 

1,3-butadiene, formaldehyde, polychlorophenols or their sodium salts (combined exposures), 

styrene and 2,3,7,8-tetrachlorodibenzo-para-dioxin (Table 4). In addition, the Zeig-Owens study 

found a statistically significant increase in non-Hodgkin lymphoma which was only modestly 

attenuated when adjusted for surveillance bias. Case–series reports have noted that a potential 

excess of multiple myeloma among WTC responders4. LHC’s are associated with a variety of 

carcinogenic exposures; elevated rates of some LHC’s have been observed in atomic bomb 

survivors as well as cancer patients treated with radiation and some forms of chemotherapy. The 

average latency for LHC’s after radiation or chemical exposure is generally shorter (< 10 years) than 

for solid tumors (≥ 20 years). Many leukemogens, including benzene, radiation and chemotherapy 

agents are associated with bone marrow toxicity at high doses. Some LHC’s are associated with 

immunosuppression (such as AIDS-related lymphomas) while others appear to be related to 

immune stimulation, including inflammation5. It is increasingly recognized that many LHC’s have 

pre-clinical phases, and the STAC recommends that the pre-malignant and myelodysplastic diseases 

be included as WTC-related conditions as well. 

 The committee recommends that childhood cancers (all cancers diagnosed in persons less than 20

years old) be listed as WTC-related conditions. The unique vulnerability of children to synthetic 
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chemicals commonly found in the environment has been documented in the landmark 1993 US 

National Academy of Sciences report6. Children drink more water, breathe more air and eat more 

food per pound, and have higher exposures than adults7,8. In addition, childhood cancers are rare 

(total incidence of 15 per 100,000 children age 0-19) and excess risks are not likely to be detectable 

in the small number of children being followed in epidemiologic studies.

 The committee recommends that rare cancers be listed as WTC-related conditions. There is no 

uniform definition of a rare cancer, and the committee recommends that definitions be based on 

age-specific incidence rates by gender, decade of age, site and histology. Site/histology 

combinations to be considered as unique cancers should be determined a priori in consultation 

with appropriate experts.

 The committee recommends that breast cancer (C500-509) be added to the list of covered 

conditions. There is evidence of PCB exposures to WTC responders and survivors based on air 

samples9, window film samples10 and one biomonitoring study11. Studies have linked total and 

congener-specific PCB levels in serum and adipose tissue with breast cancer, although evidence has 

been conflicting12-17. PCBs and some other substances at the WTC site are endocrine disruptors.

Breast cancer risks are highly related to hormonal factors, including endogenous and exogenous 

estrogens, and could plausibly be affected by endocrine disruptors. A recent study found that PCBS 

enhanced the metastatic properties of breast cancer cells by activating rho-associated kinase18.

Shiftwork involving circadian rhythm disruption has been classified by IARC as probably 

carcinogenic to humans, based in part on epidemiologic studies associating shiftwork with 

increased risks of breast cancer19. Both shiftwork and long shifts were common for workers 

involved in rescue, recovery, clean up, restoration and other activities at the WTC site. Finally, the 

Committee recognizes that the main source of data used to identify sites of cancer that might be 

associated with WTC exposures is studies of industrial workers, which have often been limited to 

men because so few women worked in these occupations. Thus, the opportunity to find evidence 

for associations between occupational and environmental exposures and female breast cancer has 

been very limited. 

The Committee recognizes that additional epidemiologic studies will soon become available, and 

recommends that as they do become available, their findings be reviewed and modifications made to 

the list as appropriate.

The Committee also recommends that, in addition to treatment for the listed cancer sites, the 

WTC Health Program provides funding and guidelines for medical screening and early detection based 
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on a review of evidence regarding the risks and benefits of the relevant screening and early detection 

modalities and appropriate counseling for individuals offered such screening.

With respect to the use of the IARC data to identify potential cancer sites in humans, the 

committee wishes to emphasize that the body of evidence regarding carcinogenicity of substances 

present in WTC dusts and smoke is not limited to those considered by IARC to have sufficient or limited 

evidence of carcinogenicity in humans. Many substances present in WTC dusts and smoke have been 

classified by IARC as known, probable or possible carcinogens based on animal studies and mechanistic 

data, and the committee believes that such evidence is highly predictive for human carcinogenicity. 

However, because there is limited concordance between specific cancer sites affected in humans and in 

animals, only those substances classified based on human data are informative regarding organ sites of 

carcinogenicity in humans. 

In addition to the evidence considered by the committee to identify potential WTC-related 

cancers, arguments in favor of listing cancer as a WTC-related condition include the presence of multiple 

exposures and mixtures with the potential to act synergistically and to produce unexpected health 

effects, the major gaps in the data with respect to the range and levels of carcinogens, the potential for 

heterogeneous exposures and hot spots representing exceptionally high or unique exposures both on 

the WTC site and in surrounding communities, the potential for bioaccumulation of some of the 

compounds, limitations of testing for carcinogenicity of many of the 287 agents and chemical groups 

cited in the first NIOSH Periodic Review, and the large volume of toxic materials present in the WTC 

towers. Although acknowledging some lack of certainty in the evidence for targeting specific organs or 

organ site groupings as WTC-related, the majority of the committee agreed that recommending the

specified cancer sites and site groupings was based on a sound scientific rationale and the best evidence 

available to date.

We appreciate the opportunity to consider this important issue and would be happy to provide 

clarification or respond to any questions you may have.

Sincerely,

Elizabeth M. Ward, PhD

Chair, World Trade Center Scientific Advisory 

Committee
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Supporting documentation for the Committee’s recommendation

Table of Contents

1) Evidence regarding carcinogenic exposures pg. 10

a) Asbestos pg. 12

b) Polycyclic aromatic hydrocarbons pg. 14

c) Polychlorinated biphenyls, dioxins, furans pg. 16

d) Particulates pg 17

e) Carcinogenic Metals pg. 19

f) Volatile organic compounds (VOCs) pg. 19

2) Mechanisms of carcinogenesis and role of inflammation pg. 20

a) Overview of carcinogenesis pg. 20

b) Mechanistic data on chemical carcinogenesis pg. 21

c) Mechanisms of specific WTC human carcinogens pg. 21

d) WTC-related respiratory conditions and inflammation pg. 23

3) Evidence regarding cancer from incidence studies pg. 24

4) Inclusion of rare cancers pg. 26

5) Inclusion of childhood cancers pg. 27
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1. Evidence regarding carcinogenic exposures

The collapse of the World Trade Center produced a dense dust and smoke cloud containing gypsum 

from wallboard, plastics, cement, fibrous glass, asbestos insulation, metals, and volatile and semivolatile organic compounds and other products of high-temperature combustion from burning jet fuel, 

heating oil, transformer oil and gasoline 20,21. Individuals caught in the dust cloud on 9/11 and working 

on or near the site in the days immediately following the attack experienced intense acute exposures to 

a mixture of substances whose concentration and composition was not measured and will never be fully 

known. However, it is known that the dust was highly alkaline, due to pulverized cement and other 

construction materials, and contained numerous particles, fibers and glass shards, resulting in acute eye,

nose and throat irritation, leading rapidly to what came to be known as WTC cough. Smoke from fires

that persisted into December 2011 contained polycyclic aromatic hydrocarbons, metals, organic 

chemicals and many other known or potential carcinogens. Heavy equipment and trucks contributed 

diesel emissions, and there was repeated resuspension of sediment and dust during the subsequent 10-

month demolition and cleanup process. Although levels of airborne contaminants were not measured in 

the first four days, the high prevalence of acute and chronic respiratory conditions in rescue, recovery, 

clean-up and restoration workers provides evidence for significant exposure levels and toxicity22.

Although some of the dust and smoke was carried away into higher levels of the atmosphere, significant 

amounts settled in surrounding streets, residences and office buildings. Dusts entered buildings through 

broken windows, open windows, and air intakes, and highly respirable particles entered through closed 

windows. Many residents returned to homes that were highly contaminated and/or not adequately 

remediated. Area residents and workers exposed to WTC dust have also been affected by chronic 

respiratory diseases, including newly diagnosed asthma and asthma exacerbation23.

Members of the STAC and individuals providing public comments have noted that exposures 

resulting from collapse of the World Trade Center were unlike any other exposures in intensity and 

variety in history. We believe that to be the case, both because of the enormous forces that pulverized 

the buildings and their contents and the combustion products generated by the high-temperature fires. 

Compounding the uniqueness of the exposures is the absence of any data on air contaminant levels or 

the composition of the dust and fumes in the first four days after the attack, and the presence of 

multiple and complex exposures. However, while acknowledging these unknown and unknowable 

factors, we believe that it is possible to make some judgments about the potential increased risks of 

developing some cancers based on the substances known to have been present. This information can be 
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gleaned from a variety of sources, including peer-reviewed literature, government reports and 

unpublished reports from private laboratories and contractors.

Based on these reports, the committee believes that both responder populations and area 

residents and workers had potential for significant exposures to toxic and carcinogenic components of 

WTC dust and smoke. Factors that influence the intensity of exposures among individuals engaged in 

rescue, recovery, demolition, debris cleanup and/or other related services include the time and date of 

arrival at the WTC site and other areas where WTC materials were transported or stored, total days and 

hours worked, specific jobs performed, breathing rates, work locations, particularly work in areas of 

smoldering fires, and availability and use of personal protective equipment and other controls. 

Especially in the early period of rescue and recovery, many individuals worked long shifts without 

adequate respiratory protection and in clothing saturated with dust from the debris, likely experiencing 

significant exposures through inhalation, ingestion, and skin absorption. Although these exposures may 

be considered relatively brief compared to longer exposures typically associated with occupational 

cancer, many individuals had high-intensity exposures, especially in the early weeks, and many 

continued to work in the area for weeks and months. Numerous animal studies provide evidence that 

brief exposures to carcinogens can cause cancer. Evaluation of the Single-Exposure Carcinogen Database 

containing 5576 studies involving 800 chemicals from 2000 articles showed that in 4271 of the studies, a 

single dose of an agent administered by multiple routes of exposure caused tumors to develop in many 

different animal models. In addition to PAHs, many of the tested chemicals are environmentally relevant 

and are on various pollutant lists, including the IARC and NTP lists. In support of the relevance of the 

single-exposure carcinogen concept to human cancer, Calabrese and Blain24 identified published 

occupational studies on benzene, beryllium, aromatic amines including benzidine, and arsenic in which 

exposures for less than a year were implicated as the causal factor in the development of cancer. In 

addition, studies of second or higher order tumors among cancer survivors have shown that both 

radiation therapy and some forms of chemotherapy increase risk for subsequent cancers, often with 

shorter latency periods than observed for lower-dose, longer-duration occupational and environmental 

exposures 25. Recent in vivo and in vitro studies using biomarkers of gene expression are consistent with 

potential increased cancer risks following relatively brief exposures to carcinogenic agents. The results 

of these studies indicate that the multistep process of chemical carcinogenesis can begin following 

exposures that range in duration from 1 to 90 days. In addition, some of the chemicals, dusts, fibers, 

metals and other materials with long half-lives may be retained in the lung and other body 

compartments for long periods after an environmental exposure.
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Exposures among community residents and those working and attending school in the area also 

have the potential to be significant, although in many ways they may be even more difficult to 

categorize than those of responders. Some residents were not evacuated; some individuals returned 

within days of the disaster to grossly dust-contaminated homes that they cleaned themselves; others 

returned to homes with less visible contamination that were later found to contain high levels of 

asbestos and other toxic substances26. Many government offices are housed in buildings below Canal 

Street, and many workers were required to return before any decontamination or cleaning took place 

and without personal protective equipment. Others worked, attended school or lived near sites where 

debris was transported or transferred in processes that continued to generate dusts. Still others 

volunteered in support activities near the site as well as residing in the community. Residential, office 

and school building exposures have the potential to be of longer duration than those among workers at 

the site if the buildings and occupied spaces were not properly remediated. Longer, lower-level 

exposures may be a particular issue for individuals with preexisting asthma and allergies and those who 

are already sensitized to dust contaminants such as nickel and hexavalent chromium. Children in 

contaminated homes, daycare settings and schools have greater exposure potential than adults due to 

crawling on floors, hand-to-mouth activities and higher respiratory rates, and may also be more 

susceptible to mutagens and carcinogens due to growth and rapid cell turnover.

In discussing the potential that exposures to WTC dust and smoke may cause cancer, the 

committee focused on classes of exposure known to be present in substantial quantities in WTC dust 

and smoke which also have substantial evidence regarding cancer in animals and humans. These include 

asbestos, polycyclic aromatic hydrocarbons (PAH’s), polychlorinated biphenyls, dioxins and furans, 

metals and volatile and semi volatile organic compounds (VOC’s). In addition, we considered some 

contaminants present in lower quantities due to potential toxicity and/or biological persistence

(polychlorinated biphenyls, dioxins and furans).

a. Asbestos

As presented by committee member Dr. John Dement, asbestos is designated as a known human 

carcinogen by IARC, with sufficient evidence for cancer of the larynx, lung, mesothelioma and ovary and 

limited evidence for cancer of the colorectum, pharynx and stomach. Bulk samples of outdoor dusts 

collected on September 16, 2001 on Cortland Street, Cherry Avenue, and Market Street, outside the 

perimeter of the WTC site, had 0.8 to 3% asbestos by weight 27. Air concentrations of dust were 

estimated to be in excess of 100,000 μg/m3 21 , and persons exposed to the dust cloud may have 
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experienced the equivalent of a lifetime of urban air particulate exposures 28. The main source of 

asbestos was the chrysotile used to insulate the lower half of the first tower. Chrysotile fibers in the 

WTC dust were predominantly shorter than 5 μm and/or less than 0.3 μm in diameter, and therefore 

not measured in the Phase Contrast Microscopy (PCM) method used by NIOSH and OSHA for 

determining compliance with OSHA Permissible Exposure Limits (PELS). Dr. Dement noted that fibers < 5 

μm in length also predominate in occupational settings 29 and represent the predominant exposures to 

workers used for cancer risk assessments. Fibers < 5 μm in length represent 90% or more of the total 

airborne fiber exposures in South Carolina and North Carolina asbestos textile plants, where excess risks 

of lung cancer and mesothelioma have been well-documented 30,31. Selection of the PCM sampling 

method that did not count fibers < 5 um in length was historically based on sampling reproducibility and 

feasibility, and not strong data demonstrating lack of toxicity of shorter fibers. Animal studies have 

suggested that longer fibers are more effective in producing lung cancer and mesothelioma than shorter 

ones, but this has not been addressed extensively in human studies which always involve mixed length 

fibers. Recent studies of asbestos textile workers in which size-specific exposures to chrysotile were 

estimated by transmission electron microscopy found all that exposures to all fiber lengths were 

strongly predictive of lung cancer risk with a higher risk for longer and thinner fibers 29,32.

All forms of asbestos are carcinogenic, although it appears that amphibole asbestos has the highest 

potency for inducing mesothelioma. Amphibole asbestos does not appear to have been present in 

significant quantities at the WTC site. Numerous risk assessments have been done for asbestos based on 

data from occupational cohorts, and there has been no documented threshold below which cancer does 

not occur. Additionally, the exposure metric used for occupational risk assessments is cumulative 

exposure, expressed as the product of exposure level by PCM and exposure duration (fiber-years), and 

short-term exposures to high airborne concentrations have been associated with increased cancer risk.

Inhaled asbestos fibers are retained in the lung for periods of months to years and are able to migrate 

into the pleural and peritoneal cavity, where they induce pleural plaques and mesothelioma. The 

relative risk of lung cancer from exposure to asbestos and other lung carcinogens, such as tobacco

smoke, is between additive and multiplicative. Case-control studies of mesothelioma have documented 

odds ratios in the range of 4–8 for asbestos exposures below 1 fiber years 33,34. The risk assessment that 

OSHA used to set the PEL of 0.1 fibers > 5 μm in length per cm3as an 8-hour time-weighted average 

exposure found that exposures to 0.1 f/cc over a working lifetime is associated with an excess risk of 3.4 

cancers per 1,000 workers. 
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b. Polycyclic Aromatic Hydrocarbons

As presented by committee member Dr. Glenn Talaska, carcinogenic polycyclic aromatic 

hydrocarbons (PAHs) are among the earliest recognized human and animal carcinogens. Carcinogenic 

PAHs were largely responsible for the excess of scrotal cancer observed by Dr. Percival Pott among 

chimney sweeps, and were subsequently documented to cause cancer when painted on the skin or 

lavaged into the lungs of experimental animals. PAHs are produced by combustion of wood, coal and 

any other carbonaceous material. PAH are important causes of occupational lung cancer among tobacco 

smokers, coke oven workers, aluminum workers and other occupational groups. Because PAHs are 

formed from combustion, they always occur in occupational and environmental settings in combination 

as complex mixtures and it is therefore not possible to isolate the effect of a single compound in 

epidemiologic studies. The carcinogenicity of specific PAHs has been evaluated by IARC based on 

evidence in animals and mechanistic considerations. Benzo(a)pyrene is listed by IARC in Group 1 

(carcinogenic), Dibenz[a,h]anthracene is listed in Group 2A (probably carcinogenic), and 

Benz[a]anthracene, Benzo[b]fluoranthene and Benzo[k]fluorenthene are listed in 2B (possibly 

carcinogenic). PAHs are absorbed by the body and metabolized to compounds that can bind to DNA. The 

major metabolites of PAHs excreted in urine are the monohydroxy PAHs, which typically have relatively

short biological half-lives (4.4 to 35 hours) 35. Sources of PAH’s at the WTC included the burning of about 

90,000 liters of jet fuel, 500,000 liters of transformer oil, 380,000 liters of fuel oil and approximately the 

same amount of gasoline plus any and all burning items. Heavy machinery and power tool brought to 

the site added to particulate and PAH exposures.

Sampling data regarding PAH’s are extremely limited; area samples were collected at the fence 

line beginning 9/16/2001. It was reported that PAH levels from the fires after 9/11 were among the 

highest ever reported from an outdoor sources36. Unfortunately, the samples were stationary area 

samples designed not to estimate exposures of workers on the pile, but the levels at or near ground 

level at the periphery to capture what might be leaving the site. It is documented that when area 

samples are not designed to capture the worst exposure case, they can underestimate personal worker 

exposure by from 3- to 40-fold37,38. The vertical velocity of the smoke from the fires at the site would be 

the major reason that samples anywhere from 4–6 blocks from the pile itself would be lower than the 

personal exposures of the workers on the pile. As the authors state in their paper, “...workers engaged 

in the cleanup efforts could have been exposed to much higher levels of PAHs than those in our samples 

and, thus, could bear higher cancer risks”

36 Indeed, another set of samples taken 13 blocks from the pile 

were approximately 50% lower than the average of the 3 sites at the fence line. Pliel et al.

36 also did not 
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report whether there were any consistent differences in PAH levels between the 3 fence line sites,

which would have occurred if there were spatial differences consistent with wind patterns or absolute 

distance from the pile.

The analysis of PAH levels by Pliel et al.36 in PM2.5 was also retrospective and opportunistic.

Analysis was limited completely to PAH remaining in the particulate phase captured on filters and not 

intended specifically for PAH analysis. Thus, any PAH in the vapor phase would not have been included 

in the analysis. Burstyn et al. (2002)39 reported that the PAH in the vapor and particulate phases 

contributed equally to total PAH exposure in other workers.

Pliel et al. used non-linear regression to estimate the levels of PAH exposure on September 11, 

2001 from the sampling data that was collected beginning September 16, 2001. They estimate that 

maximal exposure would have been 35 ng/m

3 36

. Butt et al. (2004)

10 measured the PAH levels in window 

films from buildings that varied in distances and orientation from the ground zero pile. They reported 

that upwind sites greater than 2 km from the pile had levels of 6000 ng/m

3

. This could be considered 

background. In contrast, those sites that were within 1km averaged 77,100 ng/m3, and those within 1 

km and downwind from the site averaged 130,000 ng/m3. While these data cannot be used for exposure 

estimates they do give an indication of the variation due to proximity and whether or not an window 

was in the overall plume.

Thus, it would appear that the PAH exposure estimates taken from the area samples probably 

underestimated the exposure of worker s on the pile. The magnitude of the underestimation is 

impossible to estimate, but indications are that it could be an order of magnitude or greater.

When done appropriately, biological monitoring can be a very useful in estimating exposure.

Biomonitoring integrates exposure by all routes, including the use or misuse of personal protective 

equipment. Biomonitoring can also be used to reconstruct exposures, provided the half-life of the 

biomarker and the time since the last exposure are documented. The half-life for the most widely used 

PAH biomarker, 1-hydroxypyrene (1HP), is effectively ~24 hours for persons without chronic exposure 

40,41. This means that 1HP largely represents the exposure of only the last 24 hours. Biological samples 

for PAH were also taken for exposure analysis42. Unfortunately these samples were obtained for 365 

firefighters 22–24 days after 9/11/01. Assuming that the shape of the exposure curve estimated by Pliel 

et al.36 are correct (however, as discussed above, the absolute values are likely underestimated for 

workers on the pile), then the 1HP levels measured are estimates of exposures that were much, much 

lower than the peaks that occurred 9/11–9/14. Nonetheless, the 1HP levels remained significantly 

increased over what was seen in firefighters who were not at the WTC site. Since more than 99.99% of 
15

the 1HP resulting from exposures immediately after 9/11 would have been eliminated well before the 

samples were collected, the Edelman data cannot be used to estimate exposure for that time. Rather 

they will reflect the exposure during the previous 24-hour period. The other shortcoming of the 

Edelman paper was that there was no indication of when the samples were taken relative to the 

person’s last exposure. In addition, there is no indication of the distribution of the data within the 

groups, and only the mean data are given without an idea of the variance. The important questions—

namely, were there some individuals with higher exposure in the previous 24 hours and what tasks did 

they perform—cannot be addressed either, since this information is not provided.

There are also concerns that PAH may have been adsorbed unto particulates and form large 

masses in the lung from which the PAH would only be slowly absorbed into the body 43. Unfortunately 

the biomonitoring data provided by Edelman et al.42 cannot be used to determine if this possibility was 

in fact real, since only one sample was collected from each worker.

c. Polychlorinated biphenyls, dioxins, furans

Polychlorinated biphenyls (PCBs) were present in the transformer oil in the electrical power 

substation that was located in the World Trade Center. In the area air sampling results reported by 

Lorber et al.9, a large number of chemically different congeners, which contain different amounts of 

chlorine substituted at different places in the biphenyl rings, are treated as the same material. These 

samples were taken to characterize outdoor inhalation exposures incurred by the “general population” 

defined as individuals living and working in neighborhoods surrounding GZ, and specifically did not 

address exposures that could have occurred to workers on the site or in indoor environments. Among 

the hundreds of samples analyzed for PCBs, only one sample was above 100 ng/m3, and only three were 

greater than 50 ng/m3 9. Air levels around GZ were said to be reduced fairly quickly to “normal” ambient 

urban levels of 1–8 ng/m3. This might be expected since PCBs have an extremely low vapor pressure and 

dermal absorption of PCB’s from contaminated surfaces is thought to be a significant route of exposure.

Once absorbed, PCBs have a fairly long half-life in the body, so biological monitoring should capture the 

exposure. Edelman et al. 42 sampled for 31 PCB congeners 21 days after 9/11 and found that there was 

not a statistically significant difference between any of the mean values of firefighters on or who never 

entered the GZ site. On the other hand, Dalgren et al.11 saw that certain PCB levels were markedly 

elevated in the sera of seven first responders compared to general population norms. For example, all 

seven were above the median value found in the CDC NHANES study, three were above the 75th

percentile, two above the 90th and one above the 95thpercentile. For several measured congeners the 2 
16

highest firefighters had levels above the NHANES detection limit, where 95% of the unexposed 

population was below it. These data indicate that PCB levels in the sera of at least some first responders 

were elevated relative to the general population. Dioxin-like compounds were present at elevated levels 

in the air immediately after 9/11/01. These compounds are formed when chlorinated plastics like PVC 

are burned under certain conditions of temperature, oxygen and pressure. The levels of dioxin and 

dioxin-like compounds (furans and various congeners) were markedly elevated in initial area samples 

taken at the periphery of the WTC site (Ground Zero, GZ) 9. (Please see the discussion of PAH for the 

limitations of these samples to estimate exposure for those at GZ itself.) At least 6 samples taken in late 

September or early October yielded levels of total TCDD equivalents greater than 100 pg TEQ/m3, with 

the highest levels measured being 170 pg TEQ/m3. These were the highest ambient levels ever recorded

9

. In comparison, typical urban ambient measurements or approximately 0.1 pgTEQ/m3and levels

reported downwind from incinerators are on the order 1-5 pgTEQ/m3. This would indicate substantial 

exposure to dioxin-like compounds. The USEPA did not find elevated levels of TCDD in house dusts. 

However, analyses of window films obtained from buildings at various distances from the WTC found 

that concentrations of 2,3,7,8-TCDD were 400 times higher in a sample from Church and Warren Street 

than samples taken at New York University and in Brooklyn 44.

Dioxins have relatively long half-lives in the human body; for TCDD half-life is estimated to be 7 

years (MMWR, 1988). Edelman et al. (2004)

42 measured 15 dioxin-like compounds in the sera of ~350 

firefighters. Only one congener was higher in the exposed firefighters compared to those who did not 

enter the site. The mean values were 27.8 ppt for all on site firefighters, 30.1 ppt for those present at 

the collapse, 26.2 ppt for those arriving after the collapse (day 1 and 2) and 30.6 ppt for those in Special 

Operations Command. Firefighters not at the site had an average level of 19.2 ppt. There was no 

increase in TCDD levels compared to controls (please see PAH discussion for the limitations of the data 

presented in Edelman et al., 2004). In contrast, the average levels reported in blood samples drawn 

approximately ten years after exposure for military personnel involved in spraying Agent Orange was 49 

ppt and ranged to 313 ppt. This work reported that 20 ppt was the highest level generally seen in the 

general population. Again, no significant increase in TCDD levels were reported by Edelman, et al.

2004.42,45

d. Particulates

Particulates include non-fibrous and fibrous inorganic particles. The non-fibrous are silica, coal mine 

dust, and a variety of metallic and non-metallic crustal silicates. Silica (quartz) is an IARC Group 1 
17

carcinogen based on sufficient evidence for cancer of the lung in humans and also causes silicosis, a nonmalignant lung disease characterized by scarring and inflammation. The fibrous particles include the 

commercial types of asbestos, which are all known carcinogens (chrysotile, amosite, crocidlite, 

anthophyllite). These are all hydrated magnesium silicates, and the main non-asbestos fiber that is a 

known carcinogen is the fibrous zeolite erionite. Erionite is a fibrous aluminum silicate. Other fibers may 

contaminate commercial products and be a cause of cancer, including tremolite and possibly other 

fibers in vermiculite. Man-made vitreous fibers, rock wool, fibrous glass, glass shards, and other fiberlike fragments were also present in significant quantities. Man-made vitreous fibers, refractory ceramic 

fibers and special-purpose glass fibers are classified by IARC as Group 2B, possibly carcinogenic to 

humans. Glass wool, rock wool, and slag wool are classified as Group 3, not classifiable as to their 

carcinogenicity in humans46. The NTP classifies ceramic fibers (respirable) and glass wool fibers 

(inhalable) as reasonably anticipated to be human carcinogens47. It is recognized that some of the glass 

fibers present in WTC dust were subjected to tremendous heat and are degraded from their fibrous 

form. In addition, many of the particles have been burned and some are coated with other materials.

Changes resulting from high-temperature fires have the potential to either exacerbate or reduce the 

toxicity of particles and fibers.

 

Air pollution epidemiological studies have shown that PM less than 2.5 microns is associated 

with increased mortality for lung cancer in studies of the cohort formed by the American Cancer 

Society48 and studied using time-series in Metropolitan Statistical Areas with PM measurements over 

time, and corroborated by the Harvard six-cities study49 followed prospectively. In addition, biomass 

indoor air pollution from poorly ventilated cooking stoves has been noted to increase lung cancer in 

women50. Diesel exhaust has been implicated as a cause of lung cancer in large mortality studies of 

railroad workers 51and recently in non-metallic underground miners52. This latter cohort of more than 

10,000 miners exposed to high diesel exhaust concentrations without confounding by radon had more 

than a 25% increase in lung cancer mortality. A subsequent case–control study corroborated this 

increase and differentiated the risk from cigarette smoking45. A small body of evidence exists on lung 

particulate burden based on sputum, bronchoalveolar lavage and tissue analysis, primarily from 

symptomatic WTC-responders. A bronchoalveolar lavage study of a firefighter who developed 

eosinophilic pneumonia after worked on the pile for the first two weeks after 9/11 found 305 fibers per 

million alveolar macrophages, including chrysotile and amosite asbestos fibers, chromium, degraded 

glass fibers, fly ash and many silicates53,54. Sputum samples obtained from 39 WTC-exposed FDNY 
18

firefighters ten months after 9/11 found a higher proportion of large and irregularly shaped particles 

and many more metallic elements compared to firefighters from Tel Aviv55. Minerologic analyses of 

biopsy samples from lungs of seven symptomatic responders who were exposed to WTC dust on 9/11 

and 9/12 found variable amounts of sheets of aluminum and magnesium silicates, chrysotile asbestos, 

calcium phosphate and calcium sulfate, small shards of glass and carbon nanotubes of various sizes and 

lengths56. A study of twelve WTC-exposed patients local workers, residents and clean up workers) found 

opaque and bi refringent particles within macrophages, with particles containing silica, aluminum 

silicates, titanium dioxide, talc and metals undergoing lung biopsy57.

e. Carcinogenic metals 

As noted in Table 1 and 2, five metals measured in ETC dust and air samples are listed as known 

human carcinogens by IARC; all increase risk for lung cancer with other cancer sites of sufficient or 

limited evidence in humans varying by metal. As with other WTC exposures, varying exposure levels 

have been reported and monitoring was limited9,58. In general, however, the concentration of 

carcinogenic metals in settled dust and smoke samples was low compared to concentrations of noncarcinogenic metallic elements. For example, in dust samples collected at Cortland, Cherry and Market 

Street, concentrations of titanium and zinc were over 40 times the concentration of nickel, the most 

common of the carcinogenic metals measured27. Cahill and colleagues developed the “incinerator 

hypothesis” to explain the presence several carcinogenic metals in aerosol plumes in October 2011, 

apparently liberated from burning debris at temperatures at which they would not normally volatilize59.

Groups at risk for metal exposures include workers at the WTC site (plume lofting was thought 

to protect wider areas of NYC) and responders and survivors with short-term exposure to the initial dust 

cloud and those with longer-term exposure to dusts in homes, schools and offices or during cleanup60.

Some metals, such as cadmium, bioaccumulate in the body, resulting in persistent exposure from 

endogenous sources. Further factors raising concern for metals include the potentially large load 

deposited in the lungs of those in the initial WTC collapse, with uncertain impact on half-life and 

interaction with high dust pH. 

f. Volatile organic compounds (VOCs)

As noted in Table 1, three VOCs, benzene, 1,3 butadiene and formaldehyde, are listed as known 

human carcinogens by IARC; all increase risk for lymphatic and hematopoietic cancer. Formaldehyde 

also increases risk for nasopharyngeal cancer with limited evidence for nasal cavity and paranasal sinus 
19

cancer. Hematopoetic cancers, such as leukemia, have the shortest latency of the chemically-related 

cancers, so it is biologically plausible that leukemias diagnosed to date in exposed WTC populations are 

related to 9/11. Other VOCs, such as tetrachloroethylene and trichloroethylene, are considered group 

2A probable human carcinogens that impact the hematopoetic system.

Benzene, 1,3 butadiene and formaldehyde are common exposures present in combustion products.

Groups with potential for exposure to these VOCs include workers on the pile and those exposed to 

diesel exhaust. VOCs are not persistent in environment and do not accumulate in the body.

As with other WTC exposures, varying exposure levels have been reported and monitoring was 

limited9,27,61. Benzene and 1,3-butadiene were among the 11 VOCs monitored in and near GZ to 

determine if the area was safe for entry by rescue workers and firefighters 9. These samples were mainly 

4-minute samples, with a few 24-hour samples. Of the VOCs monitored, benzene levels were noted to 

be measureable the greatest distance from GZ, with levels approaching the ATSDR Intermediate (>14–

364 days) MRL, although for a duration likely less than 45 days9. Descriptions of air in lower Manhattan 

and diesel exhaust62 suggest that more frequent air monitoring would have indicated higher levels. 

2. Mechanisms of carcinogenesis and role of inflammation

a. Overview of Carcinogenesis

As presented by Committee member Dr. Elizabeth Ward and elaborated on by Dr. Julia Quint, 

carcinogenesis is characterized by four stages: initiation, promotion, malignant transformation, and 

tumor progression. Initiation occurs when a carcinogen interacts with DNA, most often by forming a 

DNA adduct (a specific type of chemical bond) between the chemical carcinogen or one of its functional 

groups and a nucleotide in DNA, or by producing a strand break. If the cell divides before the damage is 

repaired, an alteration can become permanently fixed as a heritable error that will be passed on to 

daughter cells. Such heritable changes in DNA structure are called mutations. Many mutations have no 

apparent effect on gene function. However, when mutations occur in critical areas of genes that 

regulate cell growth, cell death, or DNA repair, they may predispose clonal expansion and accumulation 

of further genetic damage. Promoters are substances or processes that contribute to clonal expansion 

by stimulating initiated cells to replicate, forming benign tumors or hyperplastic lesions. Promotion is 

thought to be completely reversible. The process of promotion does not cause heritable alterations or 

mutations. It stimulates cell turnover, so that mutated cells can exploit their selective growth advantage 

and proliferate, increasing the probability that a cell will acquire additional mutations and become 

malignant. Unlike promotion, the end result of malignant transformation is irreversible. Tumor 
20

progression involves the further steps of local invasion and/or metastasis. 

b. Mechanistic Data on Chemical Carcinogenesis and Current Uses of the Data

Advances in the scientific understanding of cancer biology and the use of bioanalytical approaches 

(transcriptomics, proteomics, metabolomics, and toxicogenomics) have significantly improved research 

on the mechanisms of chemical carcinogenesis. In addition to using established short-term tests to 

determine whether chemicals damage DNA or cause genotoxic effects, scientists are now determining 

the effects of chemicals on epigenetic mechanisms such as DNA methylation, apoptotic response, and 

cell signaling pathways. This is an important advancement because altered DNA methylation in key 

regulatory genes may be an early and significant event in the development of human cancer63,64. 

Cancer mechanistic data and information are currently used to predict carcinogenicity, to inform 

the hazard identification process of cancer risk assessments, and to identify and classify agents that 

cause cancer. Gene expression biomarkers can distinguish between carcinogens and non-carcinogens in 

acute and subchronic in vivo and in vitro studies, and can predict carcinogenicity with high degrees of 

specificity and sensitivity65-69. Tests based on toxicogenomic and classification methods eventually may 

replace the two-year rodent cancer bioassays that currently are used to identify chemical carcinogens.

In its Guidelines for Carcinogen Risk Assessment 70(US EPA, 2005), the US EPA emphasizes the use of 

mechanistic data in evaluating the modes of actions of chemicals. IARC relies on mechanistic and other 

relevant data, in addition to epidemiological studies and cancer bioassays, in assessing carcinogenicity.

An agent is identified as carcinogenic to humans if there is sufficient evidence in animal bioassays and 

“strong evidence in exposed humans that the agent acts through a relevant mechanism of 

carcinogenicity”71. The NTP, US EPA, and Germany have adopted IARC’s approach of using information 

on mechanisms of carcinogenicity47,70. Information obtained from mechanistic studies also may be used 

to classify cancer and predict its clinical course69,72 and to identify new cancer therapies72).

c. Mechanisms of Specific WTC Human Carcinogens and the Role of Inflammation

Table 5 shows established mechanistic events related to causing human cancer for seven WTC 

human carcinogens 73. The data support the view that chemicals agents act through multiple 

mechanisms or modes of action to induce cancer. Based on the strength of existing evidence, arsenic, 

chromium VI compounds, nickel compounds and asbestos induce cancer through both genotoxic and 

epigenetic modes of action. Beryllium acts through genotoxic modes of action, and cadmium and silica 

act through epigenetic modes of action. Chromium VI compounds, nickel compounds, beryllium, and 
21

asbestos can damage DNA through direct interactions, whereas arsenic increases oxidative DNA damage 

and does not interact directly with DNA. 

Inflammation is an established mechanism of asbestos and silica-induced cancer in humans 

(Table 5). Based on several lines of evidence, inflammation also is postulated as a mechanism for human 

cancers caused by exposures to arsenic, nickel compounds, chromium VI, and beryllium (IARC, 2011).

Inflammation can accelerate multiple stages of carcinogenesis and is thought to be an important factor 

in the development of cancer. It is a normal physiologic process in response to tissue damage resulting 

from chemical irritation and/or wounding. Inflammation usually is a self-limited process that results in 

repair of damaged tissue. However, when inflammatory processes become chronic they may lead to 

persistent tissue damage that can predispose to cancer development. Critical evidence for the role of

inflammation in carcinogenesis comes from clinical conditions that involve both inflammation and 

increased cancer risk. Examples include the inflammatory diseases, ulcerative colitis and Crohn’s 

disease, and predisposition to cancer of the large bowel; and chemical injury caused by chronic reflux of 

gastric acid and bile into the distal esophagus, and development of Barrett’s esophagus and esophageal 

adenocarcinoma 74,75. Extensive experimental data on several WTC human carcinogenic agents also 

provide evidence for the role of inflammation in carcinogenesis.

Studies in animals show that asbestos fibers induce macrophage activation and persistent 

inflammation that contribute to tissue injury and cell proliferation. In a similar manner, rats exposed to 

crystalline silica develop a severe, prolonged inflammatory response that is characterized by elevated 

neutrophils, proliferation of epithelial cells, and lung tumors. Consistent with the effects of silica in 

rodents, a recent study showed significant, dose-related secretion of cytokines and alterations in gene 

expression by human lung epithelial cells exposed for 24 hours to crystalline silica, but not to amorphous 

silica76. 

Arsenic-induced increases in inflammation have been reported in numerous studies77. The 

inflammatory process involves arsenic activation of the transcription factor, NF-kB78. In mice, low levels 

of arsenic promote progressive inflammatory angiogenesis, which provides a blood supply to tumors77.

The NF-kB inflammatory signaling pathway is activated in infants born to mothers exposed to high levels 

of arsenic in drinking water 79. A single exposure to particulate chromium VI results in inflammation of 

lung tissue in mice that persists for up to 21 days. Repetitive exposure induces chronic lung injury and an 

inflammatory microenvironment that is consistent with the promotion of chromium VI-induced lung 

cancer80. Evidence that inflammation may contribute to nickel-induced carcinogenesis is based on 

studies which show that nickel compounds cause significant increases in oxidative DNA damage with 
22

concomitant inflammation in the lungs of rats81. In a review of the available studies on berylliuminduced cancer, IARC concluded that “the inflammatory processes associated with the development of 

acute or chronic beryllium disease could plausibly contribute to the development of lung cancer by 

elevating the rate of cell turnover, by enhancing oxidative stress, and by altering several signaling 

pathways involved in cell replication”73.

d. WTC-Related Respiratory Conditions and WTC Dust—Evidence of Inflammatory Processes

A number of studies have documented the role of inflammatory processes in WTC-related respiratory 

conditions. A bronchoalveolar lavage (BAL) study recovered significant quantities of fly ash, degraded 

fibrous glass, and asbestos fibers along with evidence for a significant inflammatory response (70% 

eosinophils and increased levels of interleukin-5) in one FDNY firefighter hospitalized with acute 

eosinophilic pneumonitis several weeks after WTC exposure53. Fireman et al.55, studied induced sputum 

samples obtained 10 months after the attack from 39 highly exposed firefighters and found evidence for 

higher percentages of eosinophils and neutrophils (compared to controls) that increased with exposure 

intensity. A study conducted in a cohort of 801 never-smokers with normal pre-9/11 FEV(1) found that 

elevated serum granulocyte macrophage stimulating factor( GM-CSF) and macrophage-derived 

chemokine (MDC) factor soon after WTC exposure were associated with increased risk of airflow 

obstruction in subsequent years. Surgical lung biopsies of twelve symptomatic WTC-exposed local 

workers, residents, and cleanup workers enrolled in a treatment program found interstitial fibrosis, 

emphysematous change, and small airway abnormalities were seen. All cases had opaque and 

birefringent particles within macrophages, and examined particles contained silica, aluminum silicates, 

titanium dioxide, talc, and metals59. Elevated prevalence of sarcoid-like granulomatous disease has also 

been observed among firefighters and other first responders82. Granulomatous diseases arise from 

inflammatory processes including infection (tuberculosis) and beryllium exposure (chronic beryllium 

disease) 82.

Studies of the effects of WTC dust particles on mice and on cultured human cells provide 

mechanistic evidence for the role of inflammatory processes in WTC-related respiratory conditions.

Gavett et al. found significant neutrophilic inflammation in the lungs of mice and an increase in airway 

hyper-responsiveness to methacholine challenge following exposure to a single oropharyngeal 

aspiration of fine WTC dust (mass-median aerodynamic diameter of less than 2.5 μm or PM2.5)

83

.

Exposure of human primary alveolar marcrophages and type II epithelial cells, key lung cell populations, 

to WTC dust particles (WTC PM2.5) caused time- and dose-related increases in the formation/release of 
23

pro-inflammatory cytokines/chemokines that contribute to inflammation and airway remodeling 

processes84. A recent study of WTC PM2.5 exposure in lung epithelial cells demonstrated that activation 

of mitogen-activated protein kinase signaling pathway(s) likely played an important role in the dosedependent increase of cytokine formation by the cells85

. The authors postulate that WTC-induced 

cytokine induction at low doses (0-200 μg/mL) and short time intervals (5 hr) in their study compared to 

the Payne et al. study (500–2000 μg/mL and 24 hr)84 may help to explain why the incidence of asthma 

and other inflammation-associated diseases were increased both in First Responders as well as among 

metropolitan area residents 20–30 miles away from Ground Zero.

Many exposures that cause cancer in the upper and lower respiratory tracts also cause nonmalignant respiratory diseases. Examples include tobacco smoking, silica, asbestos, beryllium, 

particulate air pollution, and indoor exposures to the burning of biomass fuels.

3. Evidence regarding cancer from completed incidence studies

One study has been published regarding cancer outcomes among 9,853 men who were employed as 

firefighters as of January 1, 1996, and were or would have been less than 60 years of age on 9/11/2001.1

Of these, 8927 were WTC-exposed. Cancers (excluding basal cell skin cancers) diagnosed between 1996 

and 2008 were identified from five state cancer registries and from self-reports on questionnaires 

administered during routine mandatory FDNY wellness evaluations performed every 12–18 months and 

subsequently verified by review of medical records.

Risks of cancer were compared by calculating expected numbers of cancers during non-exposed 

person-years (never-exposed firefighters and period before 9/11 for exposed firefighters) and postexposure person years, based on sex, age, race, and ethnicity-specific cancer rates in the SEER-13 

registries. WTC-exposed and non-exposed SIR’s were calculated for the exposed and non-exposed 

groups based on the ratios of observed and expected cancers in the general population each group. In 

addition, because firefighters constitute an unusually fit and healthy population who might be expected 

to have lower age-adjusted cancer rates than the general population, SIR Ratios were calculated to 

assess differences in cancer rates between the two groups. Among a number of secondary analyses 

reported, the one considered the most relevant was an adjustment for early diagnosis (surveillance bias) 

through lagging the diagnosis dates for two years for all cancers potentially identified by WTC-related 

medical screening in the FDNY medical surveillance program.

Strengths of the study included probably near-complete case-finding, reliable (albeit crude) 

exposure information, lack of selection bias, and inclusion of a control population with equivalent non-
24

WTC environmental and occupational exposures. Limitations include lack of representativeness for 

women, children, and elderly persons; insufficient power to detect differences in most specific cancer 

types; insufficient exposure data and insufficient variability in exposure to evaluate for a dose-response 

effect; and short follow-up time relative to cancer latency.

A total of 263 cancers were documented in 61,884 person-years after WTC exposure, where 238 

would have been expected from SEER-13 data, yielding a Standardized incidence ratio (SIR) of 1.10, with 

95% confidence interval spanning 0.98 to 1.25—just missing statistical significance. For the 60,761 

unexposed person-years, however, the SIR estimate was 0.84 (0.71 to 0.99), indicating that, absent WTC 

exposure, firefighters have a lower than predicted cancer incidence (an example of the healthy worker 

effect). Comparing exposed to unexposed, the estimated SIR ratio was 1.32, with confidence intervals 

1.07 to 1.62, demonstrating that WTC exposure increased risk of cancer approximately 32% over that 

expected in this worker population.

After introducing an artificial 2-year lag time in cancer diagnosis for thyroid, lung, and prostate 

cancers and for lymphoma (to “correct” for possible surveillance bias), the total number of diagnosed 

cancers in the exposed population would have been 242 and the estimated SIR ratio would have been 

1.21, with confidence interval spanning 0.98 to 1.49, again just missing statistical significance, but still 

far more likely than not reflecting a small excess of cancers among exposed firefighters. Arguing against 

a more severe surveillance bias is that cancer staging did not demonstrate an earlier stage of diagnosis 

in the exposed as compared to the unexposed.

For each individual type of cancer, too few cases were expected to have statistical power to 

detect moderate increases (or decreases) in cancer risk. However, for thyroid cancer, melanoma, and 

non-Hodgkin Lymphoma, SIRs were substantially higher than 1.0 and approached statistical significance. 

Regarding prostate cancer, consistent with prior studies86, even the unexposed firefighters had slightly 

and statistically significantly higher incidence than predicted, with SIR 1.35. The WTC-exposed FDNY 

group did not show an increased risk over the unexposed, with estimated SIR ratio 0.90 (after correction 

for possible surveillance bias). Therefore, despite the statistically significant SIR for prostate cancer in 

WTC-exposed firefighters compared to the general population, the overall results do not support an 

increased risk of prostate cancer associated with WTC exposures. Data from the Zeig-Owens study are 

presented in Table 4 for cancer sites with some evidence of increased risk. Some of the cancer sites with 

excess risk in this study have been observed in prior studies of firefighters86.

Additional post-WTC cancer incidence results are expected to come from the non-FDNY WTC Responder 

Consortium, the WTC registry cohorts, and the FDNY EMS cohort in the near future. The STAC has not 
25

had access to those studies and therefore has not based current recommendations on them. Given the 

paucity of epidemiological studies to date, additional studies can be expected to inform the body of 

knowledge on the issue of WTC and cancer risk, though the limitations of surveillance bias, sample size, 

selection bias, limited follow-up and others are likely to persist.

4. Inclusion of rare cancers

Excesses in rare cancers are difficult to detect in epidemiologic studies. Even large studies may 

have very low numbers of expected cases of rare cancers, and thus very low statistical power to detect 

any but very large effects. In addition, most cancer studies analyze data by organ site, and not by site 

and histology. This can result in inability to detect rare site and histology combinations, such as 

angiosarcoma of the liver, associated with vinyl chloride monomer exposure,87 and small cell carcinoma 

of the lung, associated with bis chloromethyl ether88. Cancers can also be defined as rare based on the 

patient’s gender (male breast cancer), age (prostate cancer in men under 40) or race (melanoma in 

African Americans). Since customary study methods are unlikely to identify increased risks for rare 

cancers among WTC-exposed populations unless they occur in sizable clusters. Nonetheless, given the 

sizable number of carcinogens (and related cancer sites) present in WTC smoke and dust, it is reasonable 

to consider the possibility that an increased risk of specific rare cancers may occur or that the incidence 

of common cancers would be increased at younger ages in WTC-exposed populations. One approach 

that has been used is to consider rare cancers as cancers with age-adjusted incidence rates less than 15 

per 100,000, which would result in defining 25% of all adult cancers in the US as rare89. Additional 

definitions— 10 cases per million per year, or 1 case per million per year— have also been examined89.

For the purposes of defining rare cancers for the WTC Health Program, one approach would be 

construct a matrix of on age-specific incidence rates by gender, decade of age, site and histology and to 

consider as rare any cancer with an incidence rate of < 5 or <10 per 100,000 in the appropriate gender 

age stratum for the site/histology combination. If this approach is adopted, site/histology combinations 

to be considered as unique cancers should be determined a priori in consultation with appropriate 

experts. However, it is clear that there are many reasonable approaches that could be used to define 

rare cancers and the STAC is not endorsing a specific approach at this time.

5. Inclusion of childhood cancers

The unique vulnerability of children to synthetic chemicals commonly found in the environment 

has been documented in the landmark 1993 US National Academy of Sciences report.6Children drink 
26

more water, breathe more air and eat more food per pound, and have higher exposures than adults.7,8

Their developing organ systems are also more vulnerable to many chemicals, and are less well able to 

detoxify or eliminate them.

90,91 Together, these aspects of early life development increase the likelihood 

of lifelong organ system impairment following exposure to environmental chemicals.92 Children also 

have more years of life in which chronic conditions can occur as a result of early life exposures.93

Epidemiologic studies have associated exposure to benzene94,95, certain pesticides96,97, polychlorinated 

biphenyls98,99, and 1,3-butadiene with increases in childhood malignancies.

Children who attended schools and lived near the World Trade Center site experienced exposures in the 

range of responder populations 87. Given the baseline relative infrequency in which cancer occurs in 

children, and the limited statistical power of even a study of all 14,000 children who lived south of 14th

Street on September 11, 2001, no negative study will eliminate the possibility of causation. Indeed, this 

is an area of need for research, yet such research should not preclude a measure of caution taken in 

including coverage for all cancers incident before age 21 insofar as a health care provider confirms 

substantial likelihood of association with World Trade Center exposures. 
27
28

I. Summary of Cancer Classifications for COPC and Select 

Other Agents 

IARC Group 1—Carcinogenic to Humans

This category is used when there is sufficient evidence of carcinogenicity in humans. 

Exceptionally, an agent may be placed in this category when evidence of carcinogenicity in 

humans is less than sufficient but there is sufficient evidence of carcinogenicity in experimental 

animals and strong evidence in exposed humans that the agent acts through a relevant 

mechanism of carcinogenicity.

Agent

Category

IARC NTP

Arsenic 1 A

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Arsenic.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol84/mono84-6E.pdf

Asbestos 1 A

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Asbestos.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/suppl7/Suppl7-20.pdf

Benzene 1 A

NTP hyperlink: http://monographs.iarc.fr/ENG/Monographs/suppl7/Suppl7-24.pdf

IARC hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Benzene.pdf

Benzo[a]pyrene 

(PAHs)

1 B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/PolycyclicAromaticHydrocarbons.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol92/mono92-10.pdf

Beryllium 1 A

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Beryllium.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol58/mono58-6.pdf
29

Agent

Category

IARC NTP

1,3-Butadiene 1 A

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Butadiene.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol97/mono97.pdf

Cadmium and 

compounds

1 A

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Cadmium.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol58/mono58-7E.pdf

Chromium VI 1 A

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/ChromiumHexavalentCompounds.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol49/mono49-6.pdf

Formaldehyde 1 A

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Formaldehyde.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol88/mono88-6.pdf

Nickel compounds 1 A

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Nickel.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol49/mono49-7.pdf

Quartz 1 A

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Silica.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol68/mono68-6.pdf

Soot1

1 B

NTP hyperlink http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Soots.pdf

IARC hyperlink http://monographs.iarc.fr/ENG/Monographs/vol35/volume35.pdf

Sulfuric Acid 1 A

 

1

As found in occupational exposure of chimney sweeps.
30

Agent

Category

IARC NTP

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/StrongInorganicAcidMists.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol54/mono54-6.pdf

Vinyl chloride 1 A

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/VinylHalides.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol97/mono97-8.pdf
31

IARC Group 2A—Probably Carcinogenic to Humans

This category is used when there is limited evidence of carcinogenicity in humans and sufficient 

evidence of carcinogenicity in experimental animals. In some cases, an agent may be classified 

in this category when there is inadequate evidence of carcinogenicity in humans and sufficient 

evidence of carcinogenicity in experimental animals and strong evidence that the carcinogenesis 

is mediated by a mechanism that also operates in humans. Exceptionally, an agent may be 

classified in this category solely on the basis of limited evidence of carcinogenicity in humans. 

An agent may be assigned to this category if it clearly belongs, based on mechanistic 

considerations, to a class of agents for which one of more members have been classified in 

Group 1 or in Group 2A.

Agent

Category 

IARC NTP2

Benzyl Chloride 2A NL

NTP hyperlink: Not applicable

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol71/mono71-19.pdf

Biomass fuel 

(primarily wood, indoor 

emissions from 

household combustion)

2A NL

NTP hyperlink Not applicable

IARC hyperlink http://monographs.iarc.fr/ENG/Monographs/vol95/mono95-6A.pdf

Dibenz[a,h]anthracene 2A B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/PolycyclicAromaticHydrocarbons.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol92/mono92-10.pdf

Engine Exhaust, diesel 2A B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/DieselExhaustParticulates.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol46/volume46.pdf

 

2

NL = not listed
32

Agent

Category 

IARC NTP2

Ethylene Dibromide 2A B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Dibromoethane.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol71/mono71-28.pdf

Lead (inorganic) 2A B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Lead.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol87/index.php

Nitrate ion (ingested) 2A NL

NTP hyperlink: Not applicable

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol94/mono94-6F.pdf

Polychlorinated 

Biphenyls

2A B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/PolychlorinatedBiphenyls.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/suppl7/suppl7.pdf

Tetrachloroethylene 2A B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Tetrachloroethylene.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol63/volume63.pdf

Trichloroethylene 2A B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Trichloroethylene.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol63/mono63-6.pdf
33

IARC Group 2B—Possibly Carcinogenic to Humans

This category is used for agents for which there is limited evidence of carcinogenicity in humans 

and less than sufficient evidence of carcinogenicity in experimental animals. It may also be used 

when there is inadequate evidence of carcinogenicity in experimental animals. In some instances, 

an agent for which there is inadequate evidence of carcinogenicity in humans and less than 

sufficient evidence of carcinogenicity in experimental animals, together with supporting 

evidence from mechanistic and other relevant data, may be placed in this group. An agent may 

be classified in this category solely on the basis of strong evidence from mechanistic and other 

relevant data.

Agent

Category 

IARC NTP3

Acrylonitrile 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Acrylonitrile.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol71/mono71-7.pdf

Antimony trioxide 2B NL

NTP hyperlink: Not applicable

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol47/volume47.pdf

Benzene Hexachloride 

(syn: lindane)

2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Lindane.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/suppl7/Suppl7-88.pdf 

Benz[a]anthracene 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/PolycyclicAromaticHydrocarbons.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol92/mono92-10.pdf

Benzo[b]fluoranthene 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/PolycyclicAromaticHydrocarbons.pdf

 

3

NL = not listed
34

Agent

Category 

IARC NTP3

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol92/mono92-10.pdf

Benzo[k]fluoranthene 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/PolycyclicAromaticHydrocarbons.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol92/mono92-10.pdf

Bromodichloromethane 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Bromodichloromethane.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol71/mono71-73.pdf

Carbon tetrachloride 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/CarbonTetrachloride.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol71/volume71.pdf

Cobalt sulfate and soluble cobalt 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/CobaltSulfate.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol86/mono86-6E.pdf 

Chlordane 2B NL

NTP hyperlink: Not applicable

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol79/mono79-17.pdf

4-Chloroaniline 2B NL

NTP hyperlink: Not applicable

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol57/mono57-21.pdf

Chloroform 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Chloroform.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol73/mono73-10.pdf

Chrysene 2B NL
35

Agent

Category 

IARC NTP3

NTP hyperlink: Not applicable

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol92/mono92-10.pdf

DDT 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Dichlorodiphenyltrichloroethane.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol53/mono53-9.pdf

1,4-Dichlorobenzene 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Dichlorobenzene.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol73/mono73-13.pdf

3,3'-Dichlorobenzidine 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Dichlorobenzidine.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol99/mono99-10.pdf

p,p'-Dichlorodiphenyl-dichloroethane

(TDE)

2B NL

NTP hyperlink: Not applicable

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol53/mono53-9.pdf

p,p'-Dichlorodiphenyl-dichloroethylene 

(DDE)

2B NL

NTP hyperlink:

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol53/mono53-9.pdf

1,2-Dichloroethane

(syn: Ethylene dichloride)

2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Dichloroethane.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol71/mono71-21.pdf

2,4-Dinitrotoluene 2B NL

NTP hyperlink: Not applicable
36

Agent

Category 

IARC NTP3

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol65/mono65-9.pdf

2,6-Dinitrotoluene 2B NL

NTP hyperlink: Not applicable

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol65/volume65.pdf

1,4-Dioxane 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Dioxane.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol71/mono71-25.pdf

Ethylbenzene 2B NL

NTP hyperlink: Not applicable

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol77/mono77-10.pdf

Heptachlor 2B NL

NTP hyperlink: Not applicable

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol79/mono79-17.pdf

Hexachlorobenzene 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Hexachlorobenzene.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol79/mono79-18.pdf

Hexachloroethane 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Hexachloroethane.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol73/mono73-15.pdf

Indeno[1,2,3-cd]pyrene 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/PolycyclicAromaticHydrocarbons.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol32/volume32.pdf

Methylene chloride 2B B
37

Agent

Category 

IARC NTP3

(syn: dichloromethane)

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Dichloromethane.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol32/volume32.pdf

Mirex 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Mirex.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol20/volume20.pdf

Naphthalene 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Naphthalene.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol82/mono82-8.pdf

Nickel metallic 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Nickel.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol49/mono49-7.pdf

Nitrobenzene 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Nitrobenzene.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol65/mono65-11.pdf

N-Nitroso-Di-n-propylamine 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Nitrosamines.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol17/volume17.pdf

Pentachlorophenol 2B NL

NTP hyperlink: Not applicable

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol71/mono71-34.pdf

Styrene 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Styrene.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol82/mono82-9.pdf
38

Agent

Category 

IARC NTP3

Titanium Dioxide 2B NL

NTP hyperlink: Not applicable

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol93/mono93-7F.pdf

Toxaphene 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Toxaphene.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol79/mono79-19.pdf

2,4-Toluenediisocyanate 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/TolueneDiisocyanates.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol71/mono71-37.pdf

2,6-toluene diisocyanate 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/TolueneDiisocyanates.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol71/mono71-37.pdf

2,4,6-Trichlorophenol 2B B

NTP hyperlink: http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Trichlorophenol.pdf

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol71/mono71-34.pdf

Vanadium Pentoxide 2B NL

NTP hyperlink: Not applicable

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol86/mono86-10.pdf

Vinyl acetate 2B NL

NTP hyperlink:

IARC hyperlink: http://monographs.iarc.fr/ENG/Monographs/vol63/mono63-19.pdf
39

Table 2. Selected agents that IARC has classified as carcinogenic to humans and 

related cancer sites with sufficient or limited evidence in humans 100.

Carcinogenic agent

Cancer sites with 

sufficient evidence

in humans

Cancer sites with 

limited evidence in 

humans

Acid mists, strong inorganic

(Sulfuric acid)

Larynx Lung

Arsenic and inorganic arsenic compounds Lung

Skin

Urinary bladder

Kidney

Liver

Prostate

Asbestos (all forms) Larynx

Lung

Mesothelioma

Ovary

Colorectum

Pharynx

Stomach

Benzene Leukemia (acute 

nonlymphocytic)

Leukemia (acute 

lymphocytic, chronic 

lymphocytic, multiple 

myeloma, nonHodgkin lymphoma)

Beryllium and beryllium compounds Lung

1,3-Butadiene Hematolymphatic 

organs

Cadmium and cadmium compounds Lung Kidney

Prostate

Chromium(VI) compounds Lung Nasal cavity and 

paranasal sinus

Formaldehyde Leukemia

Nasopharynx

Nasal cavity and 

paranasal sinus

Nickel compounds Lung

Nasal cavity and 

paranasal sinus

Silica dust, crystalline (in the form of quartz 

or crystobalite)

Lung

Soot Lung

Skin

Urinary bladder

2,3,7,8-Tetrachlorodibenzo-para-dioxin All cancers combined Lung

Non-Hodgkin 

lymphoma

Soft-tissue sarcoma

Vinyl Chloride Liver (angiosarcoma, 

hepatocellular 

carcinoma)
40

Table 2. Agents that IARC has classified as probably carcinogenic or possibly 

carcinogenic to humans and cancer sites with limited evidence 100

Suspected carcinogenic agent

Cancer sites with limited 

evidence in humans

Engine exhaust, diesel Lung

Urinary bladder

Lead compounds, inorganic Stomach

Polychlorinated biphenyls Hepatobiliary tract

Polychlorophenols or their sodium salts (combined 

exposures)

Non-Hodgkin lymphoma

Soft-tissue sarcoma

Tetrachloroethylene Cervix

Non-Hodgkin Lymphoma

Esophagus

Trichloroethylene Liver and biliary tract

Non-Hodgkin Lymphoma

Table 3. WTC-related health conditions specified in the Zadroga Act that may be 

associated with cancer through chronic inflammation or irritation

Upper airway

 Chronic rhinosinusitis

 Chronic nasopharyngitis

 Chronic laryngitis

 Chronic airway hyperreactivity

 Cough

 Sleep apnea

Lower airway

 Asthma

 Chronic reactive airway dysfunction syndrome

 Chronic obstructive pulmonary disease

 Other chronic respiratory disorder due to fumes and vapors

 Interstitial lung disease

Gastrointestinal

 Gastroesophageal reflux
41

Table 4. Summary of evidence regarding potential carcinogenicity of WTC exposures by cancer site 

Cancer site Carcinogenic agents at WTC 

with sufficient or limited 

evidence in humans 100

WTC-related 

Conditions

FDNY Study

Cancers with Elevated Standardized

Incidence Ratios (SIR’s) 1. **Statistically 

significant effects

Lip, Oral Cavity, and Pharynx

Lip

Oral cavity

Salivary gland

Tonsil

Pharynx Limited: Asbestos (all forms) Chronic 

nasopharyngitis

Nasopharynx Sufficient: Formaldehyde Chronic 

nasopharyngitis

Digestive Organs

Esophagus Limited: Tetrachloroethylene GERD

Stomach Limited: Asbestos (all forms)

Limited: Lead compounds, inorganic

GERD Stomach (including gastro-esophageal junction)

Observed Expected SIR (95% CI)

Exposed 8 4 2.24 (0.98–5.25)**

Non-exposed <5 2 1.23 (0.40–3.83)

SIR ratio* 1.82 (0.44–7.49

Colon and rectum Limited: Asbestos (all forms) Colon (excluding rectum)

Observed Expected SIR (95% CI)

Exposed 21 14 1.52 (0.99–2.33

Non-exposed 9 9 1.01 (0.53–1.94)

SIR ratio* 1.50 (0.69–3.27)

Anus

Liver and bile duct Sufficient: Vinyl chloride

Limited: Arsenic and inorganic arsenic 

compounds

Limited: Polychlorinated biphenyls

Limited: Trichloroethylene

Gall bladder

Pancreas

Digestive tract, unspecified

Respiratory Organs
42

Nasal cavity and paranasal

 sinus

Sufficient: Nickel compounds

Limited: Chromium(VI) compounds

Limited: Formaldehyde

Chronic 

nasopharyngitis

Upper airway 

hyperreactivity

Larynx Sufficient: Acid mists, strong inorganic

Sufficient: Asbestos (all forms)

Chronic laryngitis

Lung Sufficient: Arsenic and inorganic arsenic 

compounds

Sufficient: Asbestos (all forms)

Sufficient: Beryllium and beryllium 

compounds

Sufficient: Cadmium and cadmium 

compounds

Sufficient: Chromium(VI) compounds

Sufficient: Nickel compounds

Sufficient: Silica dust, crystalline

Sufficient: Soot

Limited: Acid mists, strong inorganic

Limited: Engine exhaust, diesel

Limited: 2,3,7,8-Tetrachlorodibenzo-paradioxin

Limited: Welding fumes

Interstitial lung 

disease

Chronic respiratory 

disorder –

fumes/vapors

Reactive airways 

disease syndrome 

(RADS)

Chronic cough 

syndrome

Bone, skin, and mesothelial and soft tissue

Bone

Skin (melanoma) Melanoma

Observed Expected SIR (95% CI)

Exposed 33 21 1.54 (1.08–2.18)**

Non-exposed 15 16 0.95 (0.57–1.58)

SIR ratio* 1.61 (0.87–2.99
43

Skin (other malignant 

neoplasms)

Sufficient: Arsenic and inorganic arsenic 

compounds

Sufficient: Soot

Mesothelioma (pleura and 

peritoneum)

Sufficient: Asbestos (all forms)

Kaposi sarcoma

Soft tissue Limited: Polychlorophenols or their 

sodium salts (combined exposures)

Limited: 2,3,7,8-Tetrachlorodibenzo-paradioxin

Breast and Female Genital Organs

Breast

Vulva

Vagina

Uterine cervix Linited: Tetrachloroethylene

Endometrium

Ovary Sufficient: Asbestos (all forms)

Male Genital Organs

Penis

Prostate Limited: Arsenic and inorganic arsenic 

compounds

Limited: Cadmium and cadmium 

compounds

Observed Expected SIR (95%CI)

Prostate

Exposed 90 60 1.49 (1.20–1.85)**

Nonexposed45 33 1.35 (1.01–1.81)**

SIR ratio* 1.11 (0.77–1.59)

Prostate, corrected (diagnosis date lagged 2 years)

Exposed 73 60 1.21 (0.96–1.52)

Nonexposed45 33 1.35 (1.01–1.81)**

SIR ratio* 0.90 (0.62–1.30)

Testis

Urinary Tract

Kidney Limited: Arsenic and inorganic arsenic 

compounds

Limited: Cadmium and cadmium 

compounds

Renal pelvis and ureter
44

Urinary bladder Sufficient: Arsenic and inorganic arsenic 

compounds

Limited: Engine exhaust, diesel

Limited: Soot

Eye, Brain, and Central Nervous System

Eye Sufficient: Welding Extensive foreign 

body washout 

required

Brain and central nervous 

system

Endocrine Glands

Thyroid Observed Expected SIR (95%CI)

Thyroid

Exposed 17 6 3.07 (1.86-5.08)**

Unexposed ≤5 3 0.59 (0.15–2.36)

SIR ratio* 5.21 (1.19–

22.74)**

Thyroid, corrected (diagnosis date lagged 2 years)

Exposed 12 6 2.17 (1.23–3.82)**

Unexposed ≤5 3 0.59 (0.15–2.36)

SIR ratio* 3.67 (0.82–16.42)

Lymphoid, Hematopoietic, and Related Tissue

Leukemia and/or lymphoma 

and multiple myeloma*

Sufficient: Benzene

Sufficient: 1,3-Butadiene

Sufficient: Formaldehyde

Limited: Polychlorophenols or their 

sodium salts (combined exposures)

Limited: Styrene

Limited: 2,3,7,8-Tetrachlorodibenzo-paradioxin

Sarcoidosis Observed Expected SIR (95% CI)

Non-Hodgkin lymphoma

Exposed 21 13 1.58 (1.03–2.42)**

Non-exposed 9 11 0.83 (0.43–1.60)

SIR ratio* 1.90 (0.87–4.15)

NHL, corrected (diagnosis date lagged 2 years)

Exposed 20 13 1.50 (0.97–2.33)

Non-exposed 9 11 0.83 (0.43–1.60)

SIR ratio* 1.81 (0.82–3.97)

Multiple sites (unspecified)

All cancers combined Sufficient: 2,3,7,8-Tetrachlorodibenzopara-dioxin

*Studies of associations between occupational and environmental carcinogens have been complicated by inaccuracies of death certificate diagnosis 

and changes in classification of cancers of the lymphatic and hematopoietic system (LHC’s) over time. Epidemiologic and animal studies may report 

morphologically distinct hematological cancers as separate endpoints even though they may share common cellular origins. Over time, there has been growing 

recognition of close relationships and overlap of such morphologically diverse disorders as chronic lymphocytic leukemia and multiple myeloma, now 

considered sub classifications of mature B-cell neoplasms (Swerdlow et al. 2008). For this reason, LHC’s are considered as a combined category in this table.
45

Table 5. WTC Human Carcinogens with established mechanistic events for tumor sites (or types) 

for which there is sufficient evidence in humans (adapted from IARC Monograph Working Group, 

2009)

WTC Human 

Carcinogen

Tumor sites (or 

types) for which 

there is sufficient 

evidence in 

humans

Other sites 

with

limited 

evidence 

in humans

Established mechanistic events

Arsenic and 

Inorganic 

arsenic compounds

Lung, skin, urinary 

bladder

Kidney, liver, 

prostate

Oxidative DNA damage, genomic 

instability, aneuploidy, gene 

amplication, epigenetic effects, DNArepair inhibition leading to 

mutagenesis

Asbestos 

(chrysotile, 

crocidolite, amosite, 

tremolite, actinolite, 

and anthophyllite)

Lung, 

mesothelioma, 

larynx, ovary

Colorectum, 

pharynx, 

stomach

Impaired fiber clearance leading to 

macrophage activation, 

inflammation, generation of reactive 

oxygen and nitrogen species, tissue 

injury, genotoxicity, aneuploidy and 

polyploidy, epigenetic alteration, 

activation of signaling pathways, 

resistance to apoptosis 

Beryllium and 

beryllium 

compounds

Lung -- Chromosome aberrations, 

aneuploidy, DNA damage

Cadmium and 

Cadmium 

compounds

Lung Prostate, 

kidney

DNA-repair inhibition, disturbance of 

tumor-suppressor proteins leading to 

genomic stability

Chromium (VI) 

compounds

Lung Nasal cavity 

and paranasal 

sinuses

Direct DNA damage after 

intracellular reduction to Cr(III), 

mutation, genomic instability, 

aneuploidy, cell transformation

Nickel compounds Lung, nasal cavity, 

and paranasal 

-- DNA damage, chromosome 

aberrations, genomic instability, 

micronuclei, DNA-repair inhibition, 
46

sinuses alteration of DNA methylation, 

histone modification

Silica dust, 

crystalline in the 

form of quartz or 

crystobalite

Lung -- Impaired particle clearance leading 

to macrophage activation and 

persistent inflammation
47

References

1. Zeig-Owens R, Webber MP, Hall CB, et al. Early assessment of cancer outcomes in New York City 

firefighters after the 9/11 attacks: an observational cohort study. Lancet. Sep 3 

2011;378(9794):898-905.

2. Bars MP, Banauch GI, Appel D, et al. "Tobacco Free With FDNY": the New York City Fire 

Department World Trade Center Tobacco Cessation Study. Chest. Apr 2006;129(4):979-987.

3. Perritt KR, Boal WL. Injuries and illnesses treated at the World Trade Center, 14 September-20 

November 2001. Prehospital and disaster medicine. May-Jun 2005;20(3):177-183.

4. Moline JM, Herbert R, Crowley L, et al. Multiple myeloma in World Trade Center responders: a 

case series. J Occup Environ Med. Aug 2009;51(8):896-902.

5. Purdue MP, Lan Q, Bagni R, et al. Prediagnostic serum levels of cytokines and other immune 

markers and risk of non-hodgkin lymphoma. Cancer Res. Jul 15 2011;71(14):4898-4907.

6. National Research C. Pesticides in the Diets of Infants and Children. 1993.

7. Trasande L, Thurston GD. The role of air pollution in asthma and other pediatric morbidities. J 

Allergy Clin Immunol. Apr 2005;115(4):689-699.

8. Thurlbeck WM. Postnatal human lung growth. Thorax. August 1, 1982 1982;37(8):564-571.

9. Lorber M, Gibb H, Grant L, Pinto J, Pleil J, Cleverly D. Assessment of inhalation exposures and 

potential health risks to the general population that resulted from the collapse of the World 

Trade Center towers. Risk analysis : an official publication of the Society for Risk Analysis. Oct 

2007;27(5):1203-1221.

10. Butt CM, Diamond ML, Truong J, Ikonomou MG, Helm PA, Stern GA. Semivolatile organic 

compounds in window films from lower Manhattan after the September 11th World Trade 

Center attacks. Environmental science & technology. Jul 1 2004;38(13):3514-3524.

11. Dahlgren J, Cecchini M, Takhar H, Paepke O. Persistent organic pollutants in 9/11 world trade 

center rescue workers: reduction following detoxification. Chemosphere. Oct 2007;69(8):1320-

1325.

12. Demers A, Ayotte P, Brisson J, Dodin S, Robert J, Dewailly E. Plasma concentrations of 

polychlorinated biphenyls and the risk of breast cancer: a congener-specific analysis. Am J 

Epidemiol. Apr 1 2002;155(7):629-635.

13. Warner M, Eskenazi B, Mocarelli P, et al. Serum dioxin concentrations and breast cancer risk in 

the Seveso Women's Health Study. Environ Health Perspect. Jul 2002;110(7):625-628.

14. Aronson KJ, Miller AB, Woolcott CG, et al. Breast adipose tissue concentrations of 

polychlorinated biphenyls and other organochlorines and breast cancer risk. Cancer Epidemiol 

Biomarkers Prev. Jan 2000;9(1):55-63.

15. Negri E, Bosetti C, Fattore E, La Vecchia C. Environmental exposure to polychlorinated biphenyls 

(PCBs) and breast cancer: a systematic review of the epidemiological evidence. Eur J Cancer 

Prev. Dec 2003;12(6):509-516.

16. Moysich KB, Menezes RJ, Baker JA, Falkner KL. Environmental exposure to polychlorinated 

biphenyls and breast cancer risk. Reviews on environmental health. Oct-Dec 2002;17(4):263-277.

17. Holford TR, Zheng T, Mayne ST, Zahm SH, Tessari JD, Boyle P. Joint effects of nine 

polychlorinated biphenyl (PCB) congeners on breast cancer risk. Int J Epidemiol. Dec 

2000;29(6):975-982.

18. Liu S, Li S, Du Y. Polychlorinated biphenyls (PCBs) enhance metastatic properties of breast cancer 

cells by activating Rho-associated kinase (ROCK). PLoS One. 2010;5(6):e11272.

19. Straif K, Baan R, Grosse Y, et al. Carcinogenicity of shift-work, painting, and fire-fighting. Lancet 

Oncol. Dec 2007;8(12):1065-1066.
48

20. Lioy PJ, Pellizzari E, Prezant D. The World Trade Center aftermath and its effects on health: 

understanding and learning through human-exposure science. Environmental science & 

technology. Nov 15 2006;40(22):6876-6885.

21. Lioy PJ, Georgopoulos P. The anatomy of the exposures that occurred around the World Trade 

Center site: 9/11 and beyond. Ann N Y Acad Sci. Sep 2006;1076:54-79.

22. Aldrich TK, Gustave J, Hall CB, et al. Lung function in rescue workers at the World Trade Center 

after 7 years. N Engl J Med. Apr 8 2010;362(14):1263-1272.

23. Brackbill RM, Hadler JL, DiGrande L, et al. Asthma and posttraumatic stress symptoms 5 to 6 

years following exposure to the World Trade Center terrorist attack. Jama. Aug 5 

2009;302(5):502-516.

24. Calabrese EJ, Blain RB. The Single Exposure Carcinogen Database: assessing the circumstances 

under which a single exposure to a carcinogen can cause cancer. Toxicological sciences : an 

official journal of the Society of Toxicology. Aug 1999;50(2):169-185.

25. Ng AK, Travis LB. Second primary cancers: an overview. Hematology/oncology clinics of North 

America. Apr 2008;22(2):271-289, vii.

26. Lin S, Jones R, Reibman J, Bowers J, Fitzgerald EF, Hwang SA. Reported respiratory symptoms 

and adverse home conditions after 9/11 among residents living near the World Trade Center. 

The Journal of asthma : official journal of the Association for the Care of Asthma. May 

2007;44(4):325-332.

27. Lioy PJ, Weisel CP, Millette JR, et al. Characterization of the dust/smoke aerosol that settled east 

of the World Trade Center (WTC) in lower Manhattan after the collapse of the WTC 11 

September 2001. Environ Health Perspect. Jul 2002;110(7):703-714.

28. Lioy PJ, Georgopoulos P, Weisel CP. An Overview of the Environmental Conditions and Human 

Exposures that Occurred Post September 11, 2001. In: Gaffney JS, Marley NA, eds. Urban 

Aerosols and Their Impact: Lessons Learned from the World Trade Center Tregedy.: American 

Chemical Society; 2006.

29. Stayner L, Kuempel E, Gilbert S, Hein M, Dement J. An epidemiological study of the role of 

chrysotile asbestos fibre dimensions in determining respiratory disease risk in exposed workers. 

Occup Environ Med. Sep 2008;65(9):613-619.

30. Elliott L, Loomis D, Dement J, Hein MJ, Richardson D, Stayner L. Lung cancer mortality in North 

Carolina and South Carolina chrysotile asbestos textile workers. Occup Environ Med. Jan 20 

2012.

31. Loomis D, Dement JM, Wolf SH, Richardson DB. Lung cancer mortality and fibre exposures 

among North Carolina asbestos textile workers. Occup Environ Med. Aug 2009;66(8):535-542.

32. Loomis D, Dement J, Richardson D, Wolf S. Asbestos fibre dimensions and lung cancer mortality 

among workers exposed to chrysotile. Occup Environ Med. Sep 2010;67(9):580-584.

33. Iwatsubo Y, Pairon JC, Boutin C, et al. Pleural mesothelioma: dose-response relation at low 

levels of asbestos exposure in a French population-based case-control study. Am J Epidemiol. Jul 

15 1998;148(2):133-142.

34. Rodelsperger K, Jockel KH, Pohlabeln H, Romer W, Woitowitz HJ. Asbestos and man-made 

vitreous fibers as risk factors for diffuse malignant mesothelioma: results from a German 

hospital-based case-control study. Am J Ind Med. Mar 2001;39(3):262-275.

35. Li Z, Romanoff LC, Lewin MD, et al. Variability of urinary concentrations of polycyclic aromatic 

hydrocarbon metabolite in general population and comparison of spot, first-morning, and 24-h 

void sampling. Journal of exposure science & environmental epidemiology. Sep 2010;20(6):526-

535.
49

36. Pleil JD, Vette AF, Johnson BA, Rappaport SM. Air levels of carcinogenic polycyclic aromatic 

hydrocarbons after the World Trade Center disaster. Proc Natl Acad Sci U S A. Aug 10 

2004;101(32):11685-11688.

37. Astrakianakis G, Seixas N, Camp J, Smith TJ, Bartlett K, Checkoway H. Cotton dust and endotoxin 

levels in three Shanghai textile factories: a comparison of samplers. Journal of Occupational and 

Environmental Hygiene. 2006;3(8):418-427.

38. Mehta AJ, Wang XR, Eisen EA, et al. Work area measurements as predictors of personal 

exposure to endotoxin and cotton dust in the cotton textile industry. The Annals of Occupational 

Hygiene. 2008;52(1):45-54.

39. Burstyn I, Randem B, Lien JE, Langard S, Kromhout H. Bitumen, polycyclic aromatic hydrocarbons 

and vehicle exhaust: exposure levels and controls among Norwegian asphalt workers. Ann 

Occup Hyg. Jan 2002;46(1):79-87.

40. Godschalk RWL, Ostertag JU, Moonen EJC, Neumann HAM, Kleinjans JCS, van Schooten FJ. 

Aromatic DNA adducts in human white blood cells and skin after dermal application of coal tar. 

Cancer Epidemiol. Biomarkers Prev. 1998;7:767-773.

41. ACGIH. Documentation of the TLVs and BEIs. Cincinnati, OH: American Conference of 

Governmental Industrial Hygienists; 2011.

42. Edelman P, Osterloh J, Pirkle J, et al. Biomonitoring of chemical exposure among New York City 

firefighters responding to the World Trade Center fire and collapse. Environ Health Perspect. Dec 

2003;111(16):1906-1911.

43. Gerde P, Medinsky MA, Bond JA. The retention of polycyclic aromatic hydrocarbons in the 

bronchial airways and in the alveolar region- a theoretical comparison. Toxicol Appld Pharmacol. 

1991;107:239-252.

44. Rayne S, Ikonomou MG, Butt CM, Diamond ML, Truong J. Polychlorinated dioxins and furans 

from the World Trade Center attacks in exterior window films from lower Manhattan in New 

York City. Environmental science & technology. Apr 1 2005;39(7):1995-2003.

45. Silverman DT, Samanic CM, Lubin JH, et al. The Diesel Exhaust in Miners Study: A Nested CaseControl Study of Lung Cancer and Diesel Exhaust. J Natl Cancer Inst. Mar 5 2012.

46. Baan RA, Grosse Y. Man-made mineral (vitreous) fibres: evaluations of cancer hazards by the 

IARC Monographs Programme. Mutat Res. Sep 3 2004;553(1-2):43-58.

47. National Toxicology Program Report on Carcinogens, Twelfth Edition2011.

48. Pope CA, 3rd, Burnett RT, Turner MC, et al. Lung cancer and cardiovascular disease mortality 

associated with ambient air pollution and cigarette smoke: shape of the exposure-response 

relationships. Environ Health Perspect. Nov 2011;119(11):1616-1621.

49. Laden F, Schwartz J, Speizer FE, Dockery DW. Reduction in fine particulate air pollution and 

mortality: Extended follow-up of the Harvard Six Cities study. Am J Respir Crit Care Med. Mar 15 

2006;173(6):667-672.

50. Zhang J, Smith KR. Indoor air pollution: a global health concern. Br Med Bull. 2003;68:209-225.

51. Garshick E, Laden F, Hart JE, et al. Lung cancer in railroad workers exposed to diesel exhaust. 

Environ Health Perspect. Nov 2004;112(15):1539-1543.

52. Attfield MD, Schleiff PL, Lubin JH, et al. The Diesel Exhaust in Miners Study: A Cohort Mortality 

Study With Emphasis on Lung Cancer. J Natl Cancer Inst. Mar 5 2012.

53. Rom WN, Weiden M, Garcia R, et al. Acute eosinophilic pneumonia in a New York City firefighter 

exposed to World Trade Center dust. Am J Respir Crit Care Med. Sep 15 2002;166(6):797-800.

54. Rom WN, Reibman J, Rogers L, et al. Emerging exposures and respiratory health: World Trade 

Center dust. Proceedings of the American Thoracic Society. May 2010;7(2):142-145.

55. Fireman EM, Lerman Y, Ganor E, et al. Induced sputum assessment in New York City firefighters 

exposed to World Trade Center dust. Environ Health Perspect. Nov 2004;112(15):1564-1569.
50

56. Wu M, Gordon RE, Herbert R, et al. Case report: Lung disease in World Trade Center responders 

exposed to dust and smoke: carbon nanotubes found in the lungs of World Trade Center 

patients and dust samples. Environ Health Perspect. Apr 2010;118(4):499-504.

57. Caplan-Shaw CE, Yee H, Rogers L, et al. Lung pathologic findings in a local residential and 

working community exposed to World Trade Center dust, gas, and fumes. J Occup Environ Med. 

Sep 2011;53(9):981-991.

58. Lioy PJ, Gochfeld M. Lessons learned on environmental, occupational, and residential exposures 

from the attack on the World Trade Center. Am J Ind Med. Dec 2002;42(6):560-565.

59. Cahill TA, Cliff SS, Shackelford Jf, et al. Very Fine Aerosols from the World Trade Center Collapse 

Piles: Anaerobic Incineration? . In: Gaffney JS, Marley NA, eds. Urban Aerosols and Their 

Impacts: Lessons Learned from the World Trade Center Tragedy. Vol 919. Washington, D.C.: 

American Chemical Society Symposium Series; 2005.

60. Plumlee GS, Hageman PL, Lamothe PJ, al. e. Inorganic chemical composition and Chemical 

Reactivity of Settled Dust Generated by the World Trade Center Building Collapse. In: Gaffney JS, 

Marley NA, eds. Urban Aerosols and Their Impacts: Lessons Learned from the World Trade 

Center Tragedy. . Vol 919. Washington, D.C.: American Chemical Society Symposium Series; 

2005.

61. Geyh AS, Chillrud S, Williams DL, et al. Assessing truck driver exposure at the World Trade 

Center disaster site: personal and area monitoring for particulate matter and volatile organic 

compounds during October 2001 and April 2002. J Occup Environ Hyg. Mar 2005;2(3):179-193.

62. Landrigan PJ, Lioy PJ, Thurston G, et al. Health and environmental consequences of the world 

trade center disaster. Environ Health Perspect. May 2004;112(6):731-739.

63. Mulero-Navarro S, Esteller M. Epigenetic biomarkers for human cancer: the time is now. Critical 

reviews in oncology/hematology. Oct 2008;68(1):1-11.

64. Baylin SB. DNA methylation and gene silencing in cancer. Nature clinical practice. Oncology. Dec 

2005;2 Suppl 1:S4-11.

65. Tsujimura K, Asamoto M, Suzuki S, Hokaiwado N, Ogawa K, Shirai T. Prediction of carcinogenic 

potential by a toxicogenomic approach using rat hepatoma cells. Cancer science. Oct 

2006;97(10):1002-1010.

66. Nakayama K, Kawano Y, Kawakami Y, et al. Differences in gene expression profiles in the liver 

between carcinogenic and non-carcinogenic isomers of compounds given to rats in a 28-day 

repeat-dose toxicity study. Toxicology and applied pharmacology. Dec 15 2006;217(3):299-307.

67. Nie AY, McMillian M, Parker JB, et al. Predictive toxicogenomics approaches reveal underlying 

molecular mechanisms of nongenotoxic carcinogenicity. Molecular carcinogenesis. Dec 

2006;45(12):914-933.

68. Thomas RS, Pluta L, Yang L, Halsey TA. Application of genomic biomarkers to predict increased 

lung tumor incidence in 2-year rodent cancer bioassays. Toxicological sciences : an official 

journal of the Society of Toxicology. May 2007;97(1):55-64.

69. Hoffmann MJ, Schulz WA. Causes and consequences of DNA hypomethylation in human cancer. 

Biochemistry and cell biology = Biochimie et biologie cellulaire. Jun 2005;83(3):296-321.

70. US EPA Guidelines for Carcinogen Risk Assessment. Washington, DC2005.

71. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. Lyon, France: 

International Agency for Research on Cancer, World Health Organization;2006.

72. Yamamoto Y, Gaynor RB. Therapeutic potential of inhibition of the NF-kappaB pathway in the 

treatment of inflammation and cancer. The Journal of clinical investigation. Jan 

2001;107(2):135-142.

73. Straif K, Benbrahim-Tallaa L, Baan R, et al. A review of human carcinogens--part C: metals, 

arsenic, dusts, and fibres. Lancet Oncol. May 2009;10(5):453-454.
51

74. Thun MJ, Henley SJ, Gansler T. Inflammation and cancer: an epidemiological perspective. 

Novartis Foundation symposium. 2004;256:6-21; discussion 22-28, 49-52, 266-269.

75. Lu H, Ouyang W, Huang C. Inflammation, a key event in cancer development. Molecular cancer 

research : MCR. Apr 2006;4(4):221-233.

76. Perkins TN, Shukla A, Peeters PM, et al. Differences in Gene Expression and Cytokine Production 

by Crystalline vs. Amorphous Silica in Human Lung Epithelial Cells. Particle and fibre toxicology. 

Feb 2 2012;9(1):6.

77. Straub AC, Stolz DB, Vin H, et al. Low level arsenic promotes progressive inflammatory 

angiogenesis and liver blood vessel remodeling in mice. Toxicology and applied pharmacology. 

Aug 1 2007;222(3):327-336.

78. Barchowsky A, Roussel RR, Klei LR, et al. Low levels of arsenic trioxide stimulate proliferative 

signals in primary vascular cells without activating stress effector pathways. Toxicology and 

applied pharmacology. Aug 15 1999;159(1):65-75.

79. Fry RC, Navasumrit P, Valiathan C, et al. Activation of inflammation/NF-kappaB signaling in 

infants born to arsenic-exposed mothers. PLoS genetics. Nov 2007;3(11):e207.

80. Beaver LM, Stemmy EJ, Schwartz AM, et al. Lung inflammation, injury, and proliferative 

response after repetitive particulate hexavalent chromium exposure. Environ Health Perspect. 

Dec 2009;117(12):1896-1902.

81. Kawanishi S, Inoue S, Oikawa S, et al. Oxidative DNA damage in cultured cells and rat lungs by 

carcinogenic nickel compounds. Free radical biology & medicine. Jul 1 2001;31(1):108-116.

82. Crowley LE, Herbert R, Moline JM, et al. "Sarcoid like" granulomatous pulmonary disease in 

World Trade Center disaster responders. Am J Ind Med. Mar 2011;54(3):175-184.

83. Gavett SH, Haykal-Coates N, Highfill JW, et al. World Trade Center fine particulate matter causes 

respiratory tract hyperresponsiveness in mice. Environ Health Perspect. Jun 2003;111(7):981-

991.

84. Payne JP, Kemp SJ, Dewar A, et al. Effects of airborne World Trade Center dust on cytokine 

release by primary human lung cells in vitro. J Occup Environ Med. May 2004;46(5):420-427.

85. Wang S, Prophete C, Soukup JM, et al. Roles of MAPK pathway activation during cytokine 

induction in BEAS-2B cells exposed to fine World Trade Center (WTC) dust. Journal of 

immunotoxicology. Oct-Dec 2010;7(4):298-307.

86. LeMasters GK, Genaidy AM, Succop P, et al. Cancer risk among firefighters: a review and metaanalysis of 32 studies. J Occup Environ Med. Nov 2006;48(11):1189-1202.

87. Ward E, Boffetta P, Andersen A, et al. Update of the follow-up of mortality and cancer incidence 

among European workers employed in the vinyl chloride industry. Epidemiology. Nov 

2001;12(6):710-718.

88. Weiss W, Moser RL, Auerbach O. Lung cancer in chloromethyl ether workers. The American 

review of respiratory disease. Nov 1979;120(5):1031-1037.

89. Greenlee RT, Goodman MT, Lynch CF, Platz CE, Havener LA, Howe HL. The occurrence of rare 

cancers in U.S. adults, 1995-2004. Public Health Rep. Jan-Feb 2010;125(1):28-43.

90. Grandjean P, Landrigan PJ. Developmental neurotoxicity of industrial chemicals. The Lancet. 

2007;368(9553):2167-2178.

91. Ginsberg G, Hattis D, Sonawane B. Incorporating pharmacokinetic differences between children 

and adults in assessing children's risks to environmental toxicants. Toxicology and Applied 

Pharmacology. 2004;198(2):164-183.

92. Rice D, Barone Jr S. Critical periods of vulnerability for the developing nervous system: Evidence 

from humans and animal models. Environmental Health Perspectives. 2000;108(SUPPL. 3):511-

533.
52

93. Bearer CF. How are children different from adults? Environmental Health Perspectives. 

1995;103(Suppl 6):7.

94. Savitz DA, Feingold L. Association of childhood cancer with residential traffic density. Scand J 

Work Environ Health. Oct 1989;15(5):360-363.

95. Knox EG. Childhood cancers and atmospheric carcinogens. J Epidemiol Community Health. Feb 

2005;59(2):101-105.

96. Lee WJ, Cantor KP, Berzofsky JA, Zahm SH, Blair A. Non-Hodgkin's lymphoma among asthmatics 

exposed to pesticides. Int J Cancer. Aug 20 2004;111(2):298-302.

97. Rudant J, Menegaux F, Leverger G, et al. Household exposure to pesticides and risk of childhood 

hematopoietic malignancies: The ESCALE study (SFCE). Environ Health Perspect. Dec 

2007;115(12):1787-1793.

98. Ward MH, Colt JS, Metayer C, et al. Residential exposure to polychlorinated biphenyls and 

organochlorine pesticides and risk of childhood leukemia. Environ Health Perspect. Jun 

2009;117(6):1007-1013.

99. Robison LL, Buckley JD, Bunin G. Assessment of environmental and genetic factors in the 

etiology of childhood cancers: the Childrens Cancer Group epidemiology program. Environ 

Health Perspect. Sep 1995;103 Suppl 6:111-116.

100. Cogliano VJ, Baan R, Straif K, et al. Preventable exposures associated with human cancers. J Natl 

Cancer Inst. Dec 21 2011;103(24):1827-1839.