# Decision Following the Formal Evaluation on the Relationship Between Exposure to Fine Particulate Matter and Certain Blood Conditions
**AGENCY:**
Department of Veterans Affairs.
**ACTION:**
Notice.
**SUMMARY:**
The Department of Veterans Affairs (VA) is issuing notice of the Secretary's determination under title 38 United States Code (U.S.C.) 1174(a)(2) that a presumption of service connection is not warranted for polycythemia vera, essential thrombocythemia, histiocytosis, mastocytosis, and chronic myeloproliferative disease for veterans exposed to fine particulate matter (PM <sub>2.5</sub> ) while serving in the Southwest Asia Theater of Operations or Somalia on or after August 2, 1990, or in Afghanistan, Egypt, Jordan, Lebanon, Syria, Yemen, Djibouti, or Uzbekistan on or after September 11, 2001.
**FOR FURTHER INFORMATION CONTACT:**
Dr. Erin Dursa, Veterans Health Administration, 202-461-7297.
**SUPPLEMENTARY INFORMATION:**
38 U.S.C. 1171-74 details the process for determining presumptions of service connection based on toxic exposures. On November 20, 2024, the Secretary of Veterans Affairs directed a formal evaluation [^1] of five blood conditions, including polycythemia vera, essential thrombocythemia, histiocytosis, mastocytosis, and chronic myeloproliferative disease for veterans exposed to PM <sub>2.5</sub> while serving in the Southwest Asia theater of operations or Somalia on or after August 2, 1990, or in Afghanistan, Egypt, Jordan, Lebanon, Syria, Yemen, Djibouti, or Uzbekistan on or after September 11, 2001.
[^1] Report to The Secretary of Veterans Affairs on the Formal Evaluation on The Relationship Between Exposure to Fine Particulate Matter (PM <sub>2.5</sub> ) in the Southwest Theater of Operations or Somalia on or after August 2, 1990, or in Afghanistan, Egypt, Jordan, Lebanon, Syria, Yemen, Djibouti, or Uzbekistan on or after September 11, 2001, and Polycythemia Vera, Essential Thrombocythemia, Histiocytosis, Mastocytosis, and Chronic Myeloproliferative Disease, May 2025 (hereafter “Formal Evaluation Report”) is available at *www.regulations.gov.*
VA conducted a formal evaluation between November 2024 and March 2025 that considered available medical evidence, Veterans Health Administration (VHA) health care data, Veterans Benefits Administration (VBA) claims data, and other factors, as required by 38 U.S.C. 1173. A structured literature search did not yield any papers that were directly relevant to assessing the relationship between exposure to PM <sub>2.5</sub> and polycythemia vera, essential thrombocythemia, histiocytosis, mastocytosis, and chronic myeloproliferative disease.
Additionally, the formal evaluation analyzed VHA electronic medical record data for the five conditions of interest between Calendar Year (CY) 2016 and CY24. The results indicate that the nine-year prevalence of these conditions among post-9/11 veterans who served in the Southwest Asia theater of operations who use VHA health care was lower than the prevalence in the general population. The nine-year prevalence of these conditions among the 1990-1991 Gulf War Era veteran population utilizing VHA health care was higher than the general population, except for mastocytosis; this was observed in both veterans who deployed to Southwest Asia and those who served during the time period of the war but did not deploy. This is likely due to this veteran population's older age distribution.
The formal evaluation also analyzed VBA claims data for polycythemia vera, essential thrombocythemia, histiocytosis, mastocytosis, and chronic myeloproliferative disease across four Gulf War Era cohorts, encompassing a total of 11,022,410 veterans. Between 2005 and 2025, 3,507 of those veterans filed claims for these conditions. The claim filing rate for these blood conditions varied minimally across cohorts, ranging from 0.01% to 0.06%. Among the claims, 1,777 veterans were granted service connection. The grant rate across the four cohorts was 50.67%. The service connection prevalence rate was low and consistent across cohorts.
The formal evaluation report was reviewed by hematologists/oncologists at the National Oncology Program Office.
Based on the findings from the formal evaluation, including a literature search and the analysis of VHA and VBA data, the Secretary has determined that a presumption of service connection is not warranted for polycythemia vera, essential thrombocythemia, histiocytosis, mastocytosis, or chronic myeloproliferative disease for veterans exposed to fine particulate matter (PM <sub>2.5</sub> ) while serving in the Southwest Asia Theater of Operations or Somalia on or after August 2, 1990, or in Afghanistan, Egypt, Jordan, Lebanon, Syria, Yemen, Djibouti, or Uzbekistan on or after September 11, 2001. Currently available evidence is not sufficient to conclude, or is not sufficient to make a scientifically informed judgment, that a positive association as likely as not exists between these blood conditions and exposure to PM <sub>2.5.</sub> This determination that presumptions of service connection are not warranted at this time does not in any way preclude VA from granting service connection based on the evidence in a particular case for any disease, including those specifically discussed in this notice, nor does it change any existing rights or procedures.
**Signing Authority**
Douglas A. Collins, Secretary of Veterans Affairs, approved this document on October 24, 2025, and authorized the undersigned to sign and submit the document to the Office of the Federal Register for publication electronically as an official document of the Department of Veterans Affairs.
Joseph Montanye,
Alternate Federal Register Liaison Officer, Department of Veterans Affairs.