Notice2026-18900
World Trade Center Health Program; Petitions 048 and 051a-Stroke; Finding of Insufficient Evidence
Primary source
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Published
September 15, 2026
Issuing agencies
Health and Human Services DepartmentCenters for Disease Control and Prevention
Abstract
The Administrator of the World Trade Center (WTC) Health Program has received two petitions (Petitions 048 and 051a) to add "stroke" to the List of WTC-Related Health Conditions. Upon reviewing the scientific and medical literature, including information provided by the petitioners, the Administrator has determined that there is insufficient evidence available to support taking further action regarding stroke at this time. The Administrator also finds that insufficient evidence exists to request a recommendation of the WTC Health Program Scientific/Technical Advisory Committee, publish a proposed rule, or publish a determination not to publish a proposed rule.
Full Text
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<title>Federal Register, Volume 91 Issue 177 (Tuesday, September 15, 2026)</title>
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[Federal Register Volume 91, Number 177 (Tuesday, September 15, 2026)]
[Notices]
[Pages 58447-58452]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-18900]
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DEPARTMENT OF HEALTH AND HUMAN SERVICES
Centers for Disease Control and Prevention
[NIOSH Docket 094]
World Trade Center Health Program; Petitions 048 and 051a--
Stroke; Finding of Insufficient Evidence
AGENCY: Centers for Disease Control and Prevention, Department of
Health and Human Services.
ACTION: Denial of petition for addition of a health condition.
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SUMMARY: The Administrator of the World Trade Center (WTC) Health
Program has received two petitions (Petitions 048 and 051a) to add
``stroke'' to the List of WTC-Related Health Conditions. Upon reviewing
the scientific and medical literature, including information provided
by the petitioners, the Administrator has determined that there is
insufficient evidence available to support taking further action
regarding stroke at this time. The Administrator also finds that
insufficient evidence exists to request a recommendation of the WTC
Health Program Scientific/Technical Advisory Committee, publish a
proposed rule, or publish a determination not to publish a proposed
rule.
DATES: The Administrator of the WTC Health Program is denying these
petitions for the addition of a health condition as of September 15,
2026.
ADDRESSES: Visit the WTC Health Program website at <a href="https://www.cdc.gov/wtc/received.html">https://www.cdc.gov/wtc/received.html</a> to review Petitions 048 and 051a.
FOR FURTHER INFORMATION CONTACT: Rachel Weiss, Program Analyst, 1090
Tusculum Avenue, MS: C-48, Cincinnati, OH 45226; telephone (404) 498-
2500 (this is not a toll-free number); email <a href="/cdn-cgi/l/email-protection#67292e28342f150200142704030449000811"><span class="__cf_email__" data-cfemail="cd8384829e85bfa8aabe8daea9aee3aaa2bb">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION:
Table of Contents
A. WTC Health Program Statutory Authority
B. Procedures for Evaluating a Petition
C. Petitions 048 and 051a
D. Evaluation of Scientific Evidence: Findings and Conclusion
E. Administrator's Final Decision on Whether To Propose the Addition
of Stroke to the List
F. Approval To Submit Document to the Office of the Federal Register
A. WTC Health Program Statutory Authority
Title I of the James Zadroga 9/11 Health and Compensation Act of
2010 (Pub. L. 111-347, as amended by Pub. L. 114-113, Pub. L. 116-59,
Pub. L. 117-328, Pub. L. 118-31, and Pub. L. 119-75), added Title
XXXIII to the Public Health Service (PHS) Act,\1\ establishing the WTC
Health Program within the Department of Health and Human Services
(HHS). The WTC Health Program provides medical monitoring and treatment
benefits for health conditions on the List of WTC-Related Health
Conditions (List) \2\ to eligible firefighters and related personnel,
law enforcement officers, and rescue, recovery, and cleanup workers who
responded to the September 11, 2001, terrorist attacks in New York
City, at the Pentagon, and in Shanksville, Pennsylvania (responders).
The Program also provides benefits to eligible persons who were present
in the dust or dust cloud on September 11, 2001, or who worked,
resided, or attended school, childcare, or adult daycare in the New
York City disaster area \3\ (survivors).
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\1\ Title XXXIII of the PHS Act is codified at 42 U.S.C. 300mm
to 300mm-64. Those portions of the James Zadroga 9/11 Health and
Compensation Act of 2010 found in Titles II and III of Public Law
111-347 do not pertain to the WTC Health Program and are codified
elsewhere.
\2\ The List of WTC-Related Health Conditions is established in
42 U.S.C. 300mm-22(a)(3)-(4) and 300mm-32(b); additional conditions
may be added through rulemaking, and the complete list is provided
in WTC Health Program regulations at 42 CFR 88.15.
\3\ See 42 U.S.C. 300mm-5(8); 42 CFR 88.1.
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All references to the Administrator of the WTC Health Program
(Administrator) in this document mean the Director of the National
Institute for Occupational Safety and Health (NIOSH) or his designee.
In accordance with section 3312(a)(6)(B) of the PHS Act, interested
parties may petition the Administrator to add a health condition to the
List in 42 CFR 88.15. Within 90 days after receipt of a valid petition
to add a condition to the List, the Administrator must take one of the
following four actions described in section 3312(a)(6)(B) of the PHS
Act and Sec. 88.16(a)(2) of the WTC Health Program regulations: (1)
Request a recommendation of the WTC Health Program Scientific/Technical
Advisory Committee (STAC); (2) publish a proposed rule in the Federal
Register to add such health condition; (3) publish in the Federal
Register the Administrator's determination not to publish such a
proposed rule and the basis for such determination; or (4) publish in
the Federal Register a determination that insufficient evidence exists
to take action under (1) through (3) above.
[[Page 58448]]
More information about the WTC Health Program, including the List
and the petition process, is available at <a href="http://www.cdc.gov/wtc/">www.cdc.gov/wtc/</a>.
B. Procedures for Evaluating a Petition
In addition to the regulatory provisions, the WTC Health Program
has developed policies to guide the review of submissions and
petitions,\4\ as well as the analysis of evidence supporting the
potential addition of a non-cancer health condition to the List.\5\
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\4\ See WTC Health Program [2026], Policy and Procedures for
Handling Submissions and Petitions to Add a Health Condition to the
List of WTC-Related Health Conditions, January 22, 2026, <a href="https://www.cdc.gov/wtc/pdfs/policies/PNP_SubmissionsPetitions%20_20260122-508.pdf">https://www.cdc.gov/wtc/pdfs/policies/PNP_SubmissionsPetitions%20_20260122-508.pdf</a>.
\5\ See WTC Health Program [2026], Policy and Procedures for
Adding Non-Cancer Conditions to the List of WTC-Related Health
Conditions, May 14, 2026, <a href="https://www.cdc.gov/wtc/pdfs/policies/WTCHP_PP_Adding_NonCancer_Health_Conditions_20260514.pdf">https://www.cdc.gov/wtc/pdfs/policies/WTCHP_PP_Adding_NonCancer_Health_Conditions_20260514.pdf</a>.
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A valid petition must include sufficient medical basis for the
association between the September 11, 2001, terrorist attacks and the
health condition to be added. In accordance with WTC Health Program
Policy and Procedures for Handling Submissions and Petitions to Add a
Health Condition to the List of WTC-Related Health Conditions,\6\
reference to a peer-reviewed, published, epidemiologic study about the
health condition among 9/11-exposed populations or clinical case
reports of health conditions in WTC responders or survivors may
demonstrate the required medical basis.\7\ Studies linking 9/11 agents
or hazards \8\ to the petitioned health condition may also provide
sufficient medical basis for a valid petition.\9\ In accordance with 42
CFR 88.16(a)(5), the Administrator is required to consider a new
petition for a previously evaluated health condition determined not to
qualify for addition to the List only if the new petition presents a
new medical basis for the association between 9/11 exposures and the
condition to be added. A new medical basis is evidence not previously
reviewed by the Administrator.
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\6\ Supra note 4.
\7\ Id. at 7.
\8\ 9/11 agents are chemical, physical, biological, or other
hazards reported in a published, peer-reviewed exposure assessment
study of responders, recovery workers, or survivors who were present
in the New York City disaster area, or at the Pentagon site, or the
Shanksville, Pennsylvania site, as those locations are defined in 42
CFR 88.1, as well as those hazards not identified in a published,
peer-reviewed exposure assessment study, but which are reasonably
assumed to have been present at any of the three sites. See WTC
Health Program [2018], Development of the Inventory of 9/11 Agents,
July 17, 2018, <a href="https://www.cdc.gov/wtc/pdfs/policies/Development_of_the_Inventory_of_9-11_Agents_20180717.pdf">https://www.cdc.gov/wtc/pdfs/policies/Development_of_the_Inventory_of_9-11_Agents_20180717.pdf</a>.
\9\ Supra note 4 at 7.
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After the Program has determined that a petition is valid, and in
accordance with the Policy and Procedures for Adding Non-Cancer
Conditions to the List of WTC-Related Health Conditions (Policy and
Procedures), the Administrator directs the WTC Health Program Science
Team (Science Team) to conduct a review of the scientific literature.
The literature review includes a keyword search of relevant scientific
databases intended to identify peer-reviewed, published, epidemiologic
studies about the health condition among 9/11-exposed populations.
The Science Team evaluates the scientific quality of each peer-
reviewed, published, epidemiologic study of the health condition
identified in the literature search using validity indicators described
in the Policy and Procedures.\10\ Studies exhibiting sufficient
validity indicators have the potential to provide a basis for deciding
whether to propose adding the health condition to the List and are
considered ``high-quality'' studies. The Science Team then evaluates
the identified high-quality studies, individually and together, to
characterize the evidence of a causal association between 9/11
exposures and the health condition. As part of this evaluation, the
Science Team considers the Bradford Hill weight of evidence
criteria,\11\ study limitations, and whether the studies are
representative of the 9/11-exposed population of responders and
survivors. After evaluating the totality of the evidence, the Science
Team assesses the degree to which the evidence supports a causal
association between 9/11 exposures and the health condition and assigns
the evidence to one of the following five categories:
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\10\ Supra note 5 at 7-8.
\11\ Hill AB [1965], The Environment and Disease: Association or
Causation? Proc R Soc Med 58(5):295-300.
According to the Policy and Procedures, the Bradford Hill
criteria are a leading weight of evidence framework ``which
comprises nine aspects of association. These aspects comprise
strength of association, consistency, specificity, temporality,
biological gradient, plausibility, coherence, experiment, and
analogy.'' See supra note 5 at 9-10 and footnotes 21-30, discussion
of Bradford Hill analysis.
Category I Evidence supports substantial likelihood of causal
association
Category II Evidence supports high likelihood of causal association
Category III Evidence supports limited likelihood of causal association
Category IV Evidence does not support causal association
Category V Evidence is inadequate to determine the likelihood of causal
association.
The Science Team provides the outcome of its evaluation to the
Administrator. A health condition may be added to the List if peer-
reviewed, published, epidemiologic studies provide support that there
is a substantial likelihood of a causal association between the health
condition and 9/11 exposures (Category I).\12\ If the evaluation of
evidence provided in peer-reviewed, published, epidemiologic studies of
the health condition in 9/11 populations shows a high, but not
substantial, likelihood of a causal association between the 9/11
exposures and the health condition (Category II),\13\ then the
Administrator may consider additional highly relevant scientific
evidence regarding exposures to 9/11 agents in non-9/11 exposure
scenarios. If that additional assessment establishes that there is now
sufficient evidence to support the conclusion that a causal association
between the 9/11 exposures and the health condition is substantially
likely among 9/11-exposed populations (Category I), then the
Administrator may propose the addition of the health condition to the
List.
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\12\ Substantial likelihood of causal association means that the
association is strongly supported by evidence from high-quality,
peer-reviewed, published epidemiologic studies of the health
condition in 9/11-exposed populations and there is high confidence
that the association cannot be explained by chance, bias,
confounding, or any other alternative explanation. See supra note 5
at 12.
\13\ High likelihood of causal association means that the
scientific evidence, taken as a whole, demonstrates that the
likelihood of a causal association is less than substantial, but
definitively more than limited. Therefore, there is some meaningful
likelihood that the association can be explained by chance, bias,
confounding, or another alternative explanation. See supra note 5 at
12.
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C. Petitions 048 and 051a
On September 3, 2023, the Administrator received a submission
(Petition 048) requesting the addition of several cardiovascular
conditions, including ``stroke'' to the List.\14\ The
[[Page 58449]]
petition's validity was established by references to 10 peer-reviewed,
published, epidemiologic studies that provided a medical basis for the
association between 9/11 exposures and stroke. The referenced studies
establishing a medical basis are as follows:
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\14\ See Petition 048, WTC Health Program: Petitions Received,
<a href="http://www.cdc.gov/wtc/received.html">http://www.cdc.gov/wtc/received.html</a>. The submission received on
September 3, 2023, requested the addition of three discrete health
condition groupings: (1) ``myocardial infraction (sic), unstable
angina, obstructive coronary artery disease, ischemic
cardiomyopathy, ischemic congestive heart failure, arrythmias (due
to any of the above);'' (2) ``stroke;'' and (3) ``peripheral
vascular disease.'' Because the submission was found to be valid for
each group of health conditions, the Administrator exercised his
discretion to separate the conditions into three separate petitions
and evaluations. Group (1) health conditions were evaluated as
``ischemic heart disease'' under Petition 047, addressed in a
Federal Register notice published on June 30, 2026 (91 FR 39616).
The second condition, stroke, is assessed in the current evaluation
under a new ordinal number as Petition 048. The third condition,
peripheral vascular disease (commonly referred to as peripheral
artery disease, PAD), has been evaluated separately under a new
ordinal number Petition 048a, and is addressed in a Federal Register
notice published in this issue.
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<bullet<ls-thn-eq> Particulate Matter Air Pollution and
Cardiovascular Disease: An Update to the Scientific Statement from the
American Heart Association, by Brook et al. [2010],\15\ an updated
scientific statement concluding that the available evidence supports a
causal relationship between exposure to particulate matter (PM) <2.5
micrometers ([micro]m) in diameter (PM<INF>2.5</INF>) and increased
stroke morbidity and mortality. The paper also briefly discussed other
9/11 agents such as nitrogen oxide and dioxide (NO<INF>X</INF>), carbon
monoxide (CO), and ozone (O<INF>3</INF>), associated with
cardiovascular diseases (CVD), including ischemic stroke.
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\15\ Brook RD, Rajagopalan S, Pope CA, Brook JR, Bhatnagar A,
Diez-Roux AV, Holguin F, Hong Y, Luepker RV, Mittleman MA, Peters A,
Siscovick D, Smith SC, Whitsel L, Kaufman JD, and on behalf of the
American Heart Association Council on Epidemiology and Prevention,
Council on the Kidney in Cardiovascular Disease, and Council on
Nutrition, Physical Activity and Metabolism [2010], Particulate
Matter Air Pollution and Cardiovascular Disease: An Update to the
Scientific Statement from the American Heart Association,
Circulation 121(21):2331-2378.
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<bullet<ls-thn-eq> Expert Position Paper on Air Pollution and
Cardiovascular Disease, by Newby et al. [2015],\16\ a scientific review
and consensus document that evaluated the evidence linking air
pollution (comprising the 9/11 agents PM<INF>2.5</INF> and PM <=10
[micro]m (PM<INF>10</INF>), ozone, nitrogen dioxide (NO<INF>2</INF>),
volatile organic compounds (including benzene), carbon monoxide (CO),
and sulfur dioxide (SO<INF>2</INF>)) to stroke and other types of CVD.
The authors concluded that air pollution increases the risk of stroke
morbidity and mortality, outlined potential biological mechanisms
underlying this relationship and determined that air pollution should
be considered a modifiable risk factor for CVD, including stroke.
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\16\ Newby DE, Mannucci PM, Tell GS, Baccarelli AA, Brook RD,
Donaldson K, Forastiere F, Franchini M, Franco OH, Graham I, Hoek G,
Hoffmann B, Hoylaerts MF, K[uuml]nzli N, Mills N, Pekkanen J, Peters
A, Piepoli MF, Rajagopalan S, Storey RF, on behalf of ESC Working
Group on Thrombosis, European Association for Cardiovascular
Prevention and Rehabilitation and ESC Heart Failure Association
[2014], Expert Position Paper on Air Pollution and Cardiovascular
Disease, Eur Heart J 36(2):83-93.
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<bullet<ls-thn-eq> Estimates and 25-Year Trends of the Global
Burden of Disease Attributable to Ambient Air Pollution: An Analysis of
Data from the Global Burden of Diseases Study 2015, by Cohen et al.
[2017],\17\ which examined trends in morbidity and mortality, including
increased stroke, related to ambient air pollution (PM<INF>2.5</INF>)
from 1990 to 2015. The authors found that ambient PM<INF>2.5</INF> was
the fifth-ranked risk factor for global deaths in 2015, with CVD,
including stroke, accounting for most of those deaths.
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\17\ Cohen AJ, Brauer M, Burnett R, Anderson R, Frostad J, Estep
K, Balakrishnan K, Brunekreef B, Dandona L, Dandona R, Feigin V,
Freedman G, Hubbell B, Jobling A, Kan H, Knibbs L, Liu Y, Martin R,
Morawska L, Pope A, FOrouzanfar MH [2017], Estimates and 25-Year
Trends of the Global Burden of Disease Attributable to Ambient Air
Pollution: An Analysis of Data from the Global Burden of Diseases
Study 2015, The Lancet 389(10082):1907-1918.
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<bullet<ls-thn-eq> A Joint ERS/ATS Policy Statement: What
Constitutes an Adverse Health Effect of Air Pollution? An Analytical
Framework, by Thurston et al. [2017],\18\ a joint European Respiratory
Society/American Thoracic Society policy statement on what constitutes
an adverse health effect of air pollution. It provides an analytical
framework for interpreting scientific evidence on the health effects of
air pollution for risk management purposes. The statement defines
ischemic stroke as an adverse effect of air pollution. It also provides
references to papers that describe increased risks for stroke from
PM<INF>2.5</INF> exposure.
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\18\ Thurston GD, Kipen H, Annesi-Maesano I, Balmes J, Brook RD,
Cromar K, DeMatteis S, Forastiere F, Forsberg B, Frampton MW, Grigg
J, Heederik D, Kelly FJ, Kuenzli N, Laumbach R, Peters A,
Rajagopalan ST, Rich D, Ritz B, Samet JM, Sandstrom T, Sigsgaard T,
Sunyer J, Brunekreef B [2017], A Joint ERS/ATS Policy Statement:
What Constitutes an Adverse Health Effect of Air Pollution? An
Analytical Framework, Eur Respir J 49(1):1600419.
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<bullet<ls-thn-eq> Ambient Air Quality and Cardiovascular Health:
Translation of Environmental Research for Public Health and Clinical
Care, by Cascio and Long [2018],\19\ a non-systematic review on CVD
outcomes, including stroke, associated with air pollution. The review
reported that PM<INF>2.5</INF> is associated with increased
cerebrovascular events.
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\19\ Cascio WE, Long TC [2018], Ambient Air Quality and
Cardiovascular Health: Translation of Environmental Research for
Public Health and Clinical Care, NC Med J 79(5):306-312.
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<bullet<ls-thn-eq> Long-Term Cardiovascular Disease Risk among
Firefighters after the World Trade Center Disaster, by Cohen et al.
[2019],\20\ a peer-reviewed, published longitudinal cohort study
designed to assess whether 9/11 exposures were associated with elevated
CVD risk, including stroke, in Fire Department of New York (FDNY)
firefighters. The study found that positive associations were observed
between CVD and 9/11 exposures related to time of arrival and length of
response.
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\20\ Cohen HW, Zeig-Owens R, Joe C, Hall CB, Webber MP, Weiden
MD, Cleven KL, Jaber N, Skerker M, Yip J, Schwartz T, Prezant DJ
[2019], Long-Term Cardiovascular Disease Risk among Firefighters
after the World Trade Center Disaster, JAMA Netw Open 2(9):e199775.
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<bullet<ls-thn-eq> Integrated Science Assessment (ISA) for
Particulate Matter, by EPA's Center for Public Health and Environmental
Assessment [2019],\21\ a detailed integrated science assessment that
examined the impact of PM, including PM<INF>2.5</INF>, on CVD outcomes
including stroke. The assessment concluded that there is some evidence
that long-term (one month to years) exposure to PM<INF>2.5</INF>
increases stroke risk.
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\21\ EPA [2019], Integrated Science Assessment (ISA) for
Particulate Matter (Final Report, Dec 2019), EPA/600/R-19/188.
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<bullet<ls-thn-eq> Cardiopulmonary Impact of Particulate Air
Pollution in High-Risk Populations: JACC State-of-the-Art Review, by
Newman et al. [2020], a Journal of the American College of Cardiology
(JACC) state-of-the-art review of the cardiopulmonary impact of PM in
high-risk populations. It recognized that air pollution, including
PM<INF>2.5</INF>, poses ischemic stroke and other CVD risks.
<bullet<ls-thn-eq> Cardiovascular Disease in the World Trade Center
Health Program General Responder Cohort, by Sloan et al. [2021],\22\ a
peer-reviewed, published prospective cohort study designed to examine
the annual and cumulative incidence of CVD, including stroke, among the
WTC Health Program general responder cohort (GRC). The study reported
increased CVD risk in males and females exposed to the WTC dust cloud
compared to those who were not exposed to the dust cloud (i.e., arrived
on or after September 12, 2021).
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\22\ Sloan NL, Shapiro MZ, Sabra A, Dasaro CR, Crane MA,
Harrison DJ, Luft BJ, Moline JM, Udasin IG, Todd AC, Teitelbaum SL
[2021], Cardiovascular Disease in the World Trade Center Health
Program General Responder Cohort, Am J Ind Med 64:97-107.
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<bullet<ls-thn-eq> Stroke Hospitalizations, Posttraumatic Stress
Disorder, and 9/11-Related Dust Exposure: Results from the World Trade
Center Health Registry, by Yu et al. [2021],\23\ a longitudinal study
that examined the risk of stroke among WTC Health Registry enrollees.
The
[[Page 58450]]
study found that WTC dust exposure is a possible risk factor for
ischemic stroke but not for hemorrhagic strokes.
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\23\ Yu S, Alper HE, Nguyen A-M, Maqsood J, Brackbill RM [2021],
Stroke Hospitalizations, Posttraumatic Stress Disorder, and 9/11-
Related Dust Exposure: Results from the World Trade Center Health
Registry, Am J Ind Med 64(10):827-836.
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These studies suggest a potential association between exposure to
9/11 agents and stroke and thus provided sufficient medical basis to
consider the submission a valid petition.
On November 1, 2023, the Administrator received a submission
(Petition 051a) requesting the addition of cardiovascular diseases,
including, among other conditions, ``stroke'' to the List.\24\ The
petition's validity was established by reference to two peer-reviewed,
published, epidemiologic studies that provided a medical basis for the
association between 9/11 exposures and stroke. The referenced studies
(Cohen et al. [2019] and Sloan et al. [2021]) each individually
establish a medical basis and are described above. These two studies
suggest a potential association between exposure to 9/11 agents and
stroke and thus provided sufficient medical basis to consider the
submission a valid petition.
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\24\ See Petition 051a, WTC Health Program: Petitions Received,
<a href="http://www.cdc.gov/wtc/received.html">http://www.cdc.gov/wtc/received.html</a>. The submission received on
November 1, 2023, was found to be valid for both cardiovascular
diseases and stroke. The Administrator exercised his discretion to
separate the health conditions into two petitions and evaluations.
Cardiovascular diseases were evaluated as ``ischemic heart disease''
under Petition 051, addressed Federal Register notice published on
June 30, 2026 (91 FR 39616). Stroke is assessed in the current
evaluation under a new ordinal number Petition 051a.
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Together, the two petitions requested the addition of stroke,
including both ischemic and hemorrhagic types. Of the 10 studies that
provided sufficient medical basis, 4 distinguish between the two types
of stroke and provide sufficient medical basis for both ischemic and
hemorrhagic stroke [Brook et al. 2010; Newby et al. 2015; EPA 2019; Yu
et al. 2021]. The other six studies do not distinguish between the two
types of stroke [Cohen et al. 2017; Thurston et al. 2017; Casio and
Long 2018, Cohen et al. 2019; Newman et al. 2020; Sloan et al. 2021].
The Administrator determined that the evaluation of scientific evidence
should address both ischemic and hemorrhagic stroke.
D. Evaluation of Scientific Evidence: Findings and Conclusion
In response to Petitions 048 and 051a and pursuant to the Policy
and Procedures, the Administrator of the WTC Health Program directed
the Science Team to conduct a systematic search of the scientific
literature to identify all peer-reviewed, published, epidemiologic
studies of stroke among 9/11-exposed populations. Identified studies
were assessed for quality; those studies determined to be high-quality
were then evaluated to determine if they provide evidence to support a
likelihood of a causal association between 9/11 exposure and the health
condition under consideration. The Science Team provided the
Administrator with a paper describing its findings, Evaluation of
Scientific Evidence Supporting the Addition of Ischemic and Hemorrhagic
Stroke to the List of WTC-Related Health Conditions. This paper, which
builds on previous evaluations of atherosclerosis and stroke conducted
in response to Petitions 012 and 020, respectively, is available in the
docket for this activity \25\ and on the Program's website.\26\
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\25\ <a href="https://www.cdc.gov/niosh/docket/archive/docket094.html">https://www.cdc.gov/niosh/docket/archive/docket094.html</a>.
\26\ <a href="https://www.cdc.gov/wtc/received.html">https://www.cdc.gov/wtc/received.html</a>.
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The literature search conducted by the WTC Health Program
identified 18 peer-reviewed, published, epidemiologic studies of stroke
in 9/11-exposed populations. Of those, nine studies were found not to
demonstrate sufficient validity indicators to be considered high-
quality studies and were not evaluated further.\27\ The remaining nine
studies were determined to have sufficient validity indicators to be
considered high-quality studies eligible for further evaluation in
accordance with the Program's Policy and Procedures.\28\ Three of the
high-quality studies were previously evaluated in the Program's
response to Petition 020:
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\27\ Brackbill RM, Thorpe LE, DiGrande L, Perrin M, Sapp JH, Wu
D, Campolucci S, Walker DJ, Cone J, Pulliam P, Thalji L, Farfel MR,
Thomas P [2006], Surveillance for World Trade Center Disaster Health
Effects Among Survivors of Collapsed and Damaged Buildings, MMWR
Surveill Summ 55(2):1-18; Jordan HT, Brackbill RM, Cone JE,
Debchoudhury I, Farfel MR, Greene CM, Hadler JL, Kennedy J, Li J,
Liff J, Stayner L, Stellman SD [2011a], Mortality Among Survivors of
the Sept 11, 2001, World Trade Center Disaster: Results from the
World Trade Center Health Registry Cohort, Lancet 378(9794):879-887;
Mani V, Wong SK, Sawitt ST, Calcagno C, Maceda C, Ramachandran S,
Fayad ZA, Moline J, McLaughlin MA [2013], Relationship Between
Particulate Matter Exposure and Atherogenic Profile in ``Ground
Zero'' Workers as Shown by Dynamic Contrast Enhanced MR Imaging, Int
J Cardiovasc Imaging 29:827-833; Stein CR, Wallenstein S, Shapiro M,
Hashim D, Moline JM, Udasin I, Crane MA, Luft BJ, Lucchini RG,
Holden WL [2016], Mortality Among World Trade Center Rescue and
Recovery Workers, 2002-2011, Am J Ind Med 59(2):87-95; Wilkenfeld M,
Fazzari M, Segelnick J, Stecker M [2016], Neuropathic Symptoms in
World Trade Center Disaster Survivors and Responders, J Occup
Environ Med 58(1):83-86; Jordan HT, Stein CR, Li J, Cone JE, Stayner
L, Hadler JL, Brackbill RM, Farfel MR [2018], Mortality Among Rescue
and Recovery Workers and Community Members Exposed to the September
11, 2001 World Trade Center Terrorist Attacks, 2003-2014, Environ
Res 163:270-279; Li J, Hall CB, Yung J, Kehm RD, Zeig-Owens R, Singh
A, Cone JE, Brackbill RM, Farfel MR, Qiao B, Schymura MJ, Shapiro
MZ, Dasaro CR, Todd AC, Prezant DJ, Boffetta P [2023], A 15-Year
Follow-Up Study of Mortality in a Pooled Cohort of World Trade
Center Rescue and Recovery Workers, Environ Res 219:115116; Singh A,
Zeig-Owens R, Cannon M, Webber MP, Goldfarb DG, Daniels RD, Prezant
DJ, Boffetta P, Hall CB [2023], All-Cause and Cause-Specific
Mortality in a Cohort of WTC-Exposed and Non-WTC-Exposed
Firefighters, Occup Environ Med 80(6):297-303; Parvin A, Kehm RD,
Qiao B, Cone JE, Farfel MR, Zeig-Owens R, Goldfarb DG, Shapiro MZ,
Todd AC, Insaf T, Hall CB, Boffetta P, Li J [2026], Effect of World
Trade Center Health Program on Mortality Among 9/11 Responders, Ann
Epidemiol 115:8-14.
\28\ See supra note 5 at 7-8.
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<bullet> Jordan HT, Stellman SD, Morabia A, Miller-Archie SA, Alper
H, Laskaris Z, Brackbill RM, Cone JE [2013], Cardiovascular Disease
Hospitalizations in Relation to Exposure to the September 11, 2001
World Trade Center Disaster and Posttraumatic Stress Disorder, J Am
Heart Assoc 2(5):e000431.
<bullet> Yu S, Alper HE, Nguyen AM, Brackbill RM [2018], Risk of
Stroke Among Survivors of the September 11, 2001, World Trade Center
Disaster, J Occup Environ Med 60(8):e371-e376.
<bullet> Remch M, Laskaris Z, Flory J, Mora-McLaughlin C, Morabia A
[2018], Post-Traumatic Stress Disorder and Cardiovascular Diseases: A
Cohort Study of Men and Women Involved in Cleaning the Debris of the
World Trade Center Complex, Circ Cardiovasc Qual Outcomes
11(7):e004572.
The six newly-identified high-quality studies were:
<bullet> Cohen HW, Zeig-Owens R, Joe C, Hall CB, Webber MP, Weiden
MD, Cleven KL, Jaber N, Skerker M, Yip J, Schwartz T, Prezant DJ
[2019], Long-Term Cardiovascular Disease Risk Among Firefighters After
the World Trade Center Disaster, JAMA Netw Open 2(9):e199775.
<bullet> Colbeth HL, Zeig-Owens R, Hall CB, Webber MP, Schwartz TM,
Prezant DJ [2020], Mortality Among Fire Department of the City of New
York Rescue and Recovery Workers Exposed to the World Trade Center
Disaster, 2001-2017, Int J Environ Res Public Health 17(17):6266.
<bullet> Sloan NL, Shapiro MZ, Sabra A, Dasaro CR, Crane MA,
Harrison DJ, Luft BJ, Moline JM, Udasin IG, Todd AC, Teitelbaum SL
[2021], Cardiovascular Disease in the World Trade Center Health Program
General Responder Cohort, Am J Ind Med 64(2):97-107.
<bullet> Yu S, Alper HE, Nguyen A-M, Maqsood J, Brackbill RM
[2021], Stroke Hospitalizations, Posttraumatic Stress Disorder, and 9/
11-Related Dust Exposure: Results from the World Trade Center Health
Registry, Am J Ind Med 64(10):827-836.
[[Page 58451]]
<bullet> Alper HE, Brite J, Cone JE, Brackbill RM [2021],
Comparison of Prevalence and Exposure-Disease Associations Using Self-
Report and Hospitalization Data Among Enrollees of the World Trade
Center Health Registry, BMC Med Res Methodol 21(162).
<bullet> Mueller AK, Cohen H, Singh A, Webber MP, Hall CB, Prezant
DJ, Zeig-Owens R [2024], Self-Reported Cardiovascular Disease in Career
Firefighters With and Without World Trade Center Exposure, J Occup
Environ Med 66(2):135-140.
The Science Team conducted an evaluation, separately and together,
of the nine studies to determine the likelihood of a causal association
between 9/11 exposures and the petitioned health condition. The
systematic literature search, the Science Team's evaluation and
synthesis of the available literature, and the Science Team's
conclusions regarding the association between 9/11 exposure and stroke
are described in full in the Science Team's Evaluation of Scientific
Evidence Supporting the Addition of Ischemic and Hemorrhagic Stroke to
the List of WTC-Related Health Conditions.
In accordance with the Policy and Procedures,\29\ the WTC Health
Program uses the following Bradford Hill criteria to evaluate studies
of 9/11-exposed populations: strength of association,\30\ precision of
the risk estimate,\31\ consistency of associations,\32\
temporality,\33\ biological gradient,\34\ and biological
plausibility,\35\ coherence,\36\ and analogy.\37\ The Science Team also
considered the limitations of the evaluated evidence and whether the
evidence is representative of the complete 9/11-exposed population of
responder and survivors, including those exposed in the New York City
disaster area as well as the Pentagon and Shanksville, Pennsylvania
sites. The nine high-quality studies are discussed in full in the
Science Team's Evaluation; a summary of the evidence synthesis is found
in Table 11, reproduced here:
---------------------------------------------------------------------------
\29\ Supra note 5 at 9-10.
\30\ It is generally thought that strong associations are more
likely to be causal than weak associations; however, a weak
association does not rule out a causal relationship.
\31\ Precision of the risk estimate describes the uncertainty
inherent in estimating the strength of association (the effect size)
between exposure and health effect from observational data. It is
expressed as a confidence interval illustrating a range of values
that contains the true effect size. A narrow confidence interval
indicates a more precise measure of the effect size, and a wider
interval indicates greater uncertainty. While precision is not a
Bradford Hill criterion, the Science Team takes it into
consideration to evaluate the existence of random error in a study.
\32\ Consistent findings are demonstrated when they have been
repeatedly reported by multiple studies.
\33\ Temporality is the condition that the 9/11 exposure must
precede the health condition of interest and is typically assessed
when considering aspects of exposure in the study design.
\34\ Studies establish an exposure-response relationship by
demonstrating that increases in exposure (i.e., exposures of greater
intensity and/or longer duration) are associated with a greater
incidence of disease. A thorough evaluation of exposure-response
requires analysis of multiple levels of exposure such that the
investigator can demonstrate that the risk increases with increasing
levels of exposure.
\35\ Study findings demonstrate a basis in scientific theory
that supports the relationship between the exposure and the health
effect and do not conflict with known facts about the biology of the
health condition.
\36\ Coherence implies that the interpretation of a causal
association agrees with known disease etiology.
\37\ Analogy is used to inform on biological plausibility and
coherence by contrasting the evidence on the suspected causal
association with that from an established association between
similar (analogous) causes or effects.
------------------------------------------------------------------------
Aspect of associative causal
inference Evaluation findings
------------------------------------------------------------------------
Strength of the Association Modest positive associations were evident
(and estimate of precision). in some studies that were suggestive of
a causal association. One earlier study
of self-reported stroke reported a
modest but statistically significant
association with WTC-dust exposure [Yu
et al. 2018]. However, statistically
significant estimates of exposure-
related stroke were not reported by any
study published since the evaluation for
Petition 020 was published. Two studies
of responders reported significant
positive associations between 9/11
exposure and a composite outcome in
which cerebrovascular disease was a
minor contributor [Cohen et al. 2019;
Sloan et al. 2021]. Objective measures
of stroke events and stroke risk were
limited to three studies published since
the previous evaluation [Alper et al.
2021; Yu et al. 2021; Mueller et al.
2024], and none of those studies found
significant risk elevations in those
objective stroke measures from 9/11
exposures.
Consistency of Associations.. Findings among studies were inconsistent,
ranging from strong deficits in
mortality [Colbeth et al. 2020] to
modest, but statistically significant
increases in incidence in four studies
[Yu et al. 2018; Cohen et el. 2019;
Alper et al. 2021; Sloan et al. 2021].
In general, the inconsistency may be
attributable to large differences in
outcome definition and study designs.
For example, large differences in risk
estimates were observed in one study
using both self-reported stroke and
stroke ascertained from medical records
[Mueller et al. 2024]. In another study
using both self-reported stroke and
stroke ascertained from medical records,
risk estimates were statistically
significant only for self-reported
stroke [Alper et al. 2021]. Only one
study differentiated between ischemic
and hemorrhagic stroke subtypes [Yu et
al. 2021]. That study reported a modest
but imprecise estimate of an association
between 9/11 exposure and ischemic
stroke, and no evidence of an
association with hemorrhagic stroke.
Despite ischemic and hemorrhagic stroke
having similar risk factors, Yu et al.
[2021] did not report findings for all
types of stroke combined.
Temporality.................. Longitudinal study designs reduced the
potential for errors from preexisting
conditions. Researchers attempted to
exclude persons with previous stroke.
However, given potentially long latency,
stroke and related health conditions may
have manifested prior to 9/11. Analyses
examining temporal effects (e.g.,
latency and persistence) were not
conducted.
Biological Gradient.......... Mueller et al. [2024] was the only study
that used a specific stroke outcome and
also examined biological gradient. It
found evidence suggestive of modestly
increasing stroke risk across increasing
categories of 9/11 exposure, but the
trend was not statistically significant.
Plausibility, Coherence, and An association between WTC dust exposure
Analogy. and stroke is coherent with the
available evidence. There is large
uncertainty in an analogy comparing a
proposed causal association between WTC
dust exposure and stroke and the
possible relationship between PM2.5 in
air pollution and stroke. The latter is
supported by evidence linking long-term
exposure to ambient air pollution to
increased stroke risk. Chronic exposure
to PM2.5 in air pollution and acute
exposure to WTC dusts are largely
dissimilar. There is sparse evidence
available on the relevant etiologic
period for late cardiovascular effects
from PM2.5 exposure; therefore, the
biological plausibility of these effects
remains largely uncertain.
Representativeness........... There was representation of all groups of
9/11-exposed populations.
------------------------------------------------------------------------
[[Page 58452]]
Upon review of the evidence available in high-quality studies
regarding stroke among 9/11-exposed populations, the Science Team found
that the current evidence is insufficient to support a finding of
substantial or high likelihood of a causal association. Based on weight
of evidence, the Science Team has concluded that: (1) the available
evidence of a causal association between 9/11 exposures and ischemic
stroke is limited (Category III); \38\ and (2) the available evidence
of a causal association between 9/11 exposures and hemorrhagic stroke
or a transient ischemic attack is inadequate (Category V).\39\
---------------------------------------------------------------------------
\38\ See Policy and Procedures supra note 5 at Section V.C.
Category III--Evidence Supports Limited Likelihood of Causal
Association.
\39\ See Policy and Procedures supra note 5 at Section V.E.
Category V--Evidence is Inadequate to Determine a Causal
Association.
---------------------------------------------------------------------------
E. Administrator's Final Decision on Whether To Propose the Addition of
Stroke to the List
Pursuant to the PHS Act, sec. 3312(a)(6)(B)(iv) and 42 CFR
88.16(a)(2)(iv), and in accordance with Sec. VIII.B. of the Policy and
Procedures, the Administrator has determined that insufficient evidence
is available to take further action at this time, including proposing
the addition of stroke to the List (pursuant to the PHS Act, sec.
3312(a)(6)(B)(ii) and 42 CFR 88.16(a)(2)(ii)) or publishing a
determination not to publish a proposed rule in the Federal Register
(pursuant to the PHS Act, sec. 3312(a)(6)(B)(iii) and 42 CFR
88.16(a)(2)(iii)). The Administrator has also determined that
requesting a recommendation from the STAC (pursuant to the PHS Act,
sec. 3312(a)(6)(B)(i) and 42 CFR 88.16(a)(2)(i)) is unwarranted.
For the reasons discussed above, the request in Petitions 048 and
051a to add stroke to the List of WTC-Related Health Conditions is
denied.
F. Approval To Submit Document to the Office of the Federal Register
The Secretary, HHS, or his designee, the Director, Centers for
Disease Control and Prevention (CDC) and Administrator, Agency for
Toxic Substances and Disease Registry (ATSDR), authorized the
undersigned, the Administrator of the WTC Health Program, to sign and
submit the document to the Office of the Federal Register for
publication as an official document of the WTC Health Program. Erica
Schwartz, MD, MPH, JD, RADM, USPHS (ret), Director, CDC, and
Administrator, ATSDR, approved this document for publication on
September 8, 2026.
John J. Howard,
Administrator, World Trade Center Health Program and Director, National
Institute for Occupational Safety and Health, Centers for Disease
Control and Prevention, Department of Health and Human Services.
[FR Doc. 2026-18900 Filed 9-14-26; 8:45 am]
BILLING CODE 4163-18-P
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