Project PHOENIX is an observational clinical research study designed to characterize molecular, genomic, cellular, and functional features in blood specimens from former U.S. Service Members with prior burn pit exposure and from matched unexposed controls. Participants will complete screening, informed consent, health and exposure questionnaires, and a one-time blood collection. Blood-derived specimens may undergo genomic, epigenomic, transcriptomic, proteomic, metabolomic, immunophenotyping, and cellular functional analyses. Participants may also agree to optional future re-contact for health updates and possible repeat blood collection. The goal is to identify biologic signatures associated with prior deployment-related burn pit exposure and to support future biomarker discovery and translational research in veteran health.

Open-air burn pits used during military operations in Southwest Asia and other deployment settings have been associated with complex airborne exposures and long-term health concerns, including respiratory, cardiovascular, neurologic, immune, and oncologic sequelae. Prior studies have relied largely on self-report, clinical symptoms, or limited physiologic testing, and there remains a need for objective biologic markers of exposure-associated effects. Project PHOENIX is intended to generate a standardized, high-dimensional biospecimen and data resource that can support biomarker discovery, mechanistic modeling, and future translational research.

Participants will enroll remotely. Screening, consent, and questionnaire completion will occur electronically through a secure eConsent platform. After consent, participants will complete a baseline study visit that includes eligibility confirmation, collection of demographic and exposure history and venipuncture.

The exposed cohort will include former U.S. Service Members with prior deployment to locations with known burn pit operations. The control cohort will include comparable U.S. Service Members/Veterans without known burn pit deployment exposure. Planned analyses include between-group comparisons across multi-omic and cellular-function domains, assessment of exposure intensity/duration relationships, and development of integrated predictive models using statistical and machine-learning methods. Optional annual re-contact for up to 5 years may be used to update health status and obtain additional blood specimens.

Inclusion Criteria:

• Age 18 years or older at the time of consent
• Former or current U.S. Service Member, including Active Duty, Reserve, National Guard, or Veteran status
• For exposed cohort: prior deployment to a location with known burn pit operations, based on participant report and available confirmation when feasible
• For control cohort: no known deployment to burn pit locations
• Able and willing to provide informed consent and HIPAA authorization
• Willing to complete study questionnaires and donate venous blood sample
• Able to complete study procedures in English or with approved translation support
• Available for one baseline visit and optional future re-contact, if applicable

Exclusion Criteria:

• Active serious illness or infection that, in the investigator's judgment, would compromise participation or specimen integrity
• Receipt of systemic chemotherapy, immunotherapy, or radiation therapy within the past 6 months
• High-dose systemic immunosuppression, defined as more than 20 mg prednisone equivalent daily for more than 14 days within the past 3 months
• Pregnant or currently breast-feeding
• Hemoglobin less than 10 g/dL, known bleeding disorder, or platelet count less than 100 × 10^9/L, if known
• Severe psychiatric illness or other condition that impairs ability to provide informed consent
• Prisoner or institutionalized individual
• Prior participation in this or a related Project PHOENIX protocol
• Any other condition that, in the investigator's judgment, may increase risk or interfere with study conduct or data integrity

Former U.S. Service Members and Veterans in the United States, including individuals with prior deployment-related burn pit exposure and comparable unexposed controls. Enrollment will occur through remote screening and consent followed by approved mobile phlebotomy.

De-identified data and associated metadata may be shared in the future with qualified investigators under sponsor governance, applicable IRB approval, and data use agreements, consistent with participant consent and applicable privacy requirements.