Characteristics of Participants During the First Three Years of the National Firefighter Registry for Cancer, United States, January 2023–December 2025

BACKGROUND: Firefighting is a known human carcinogen, but knowledge gaps remain regarding cancer burden and risk factors among U.S. firefighters. The Firefighter Cancer Registry Act of 2018 directed the development of the National Firefighter Registry (NFR) for Cancer, a voluntary exposure registry managed by the National Institute for Occupational Safety and Health. This manuscript describes participation during the first three years of NFR enrollment (January 2023-December 2025). METHODS: We descriptively calculated frequencies and percentages of participants across demographic and occupational characteristics and stratified by enrollment completion status, work status, and method of recruitment. RESULTS: There were 39,058 firefighters from all 50 states and several territories who participated in the NFR, including 4019 reporting a history of cancer. Participants were predominantly male (91%), White (83%), actively serving full time (75%), and reported various firefighting assignments. Overall, 72% of participants submitted the enrollment questionnaire, 24% did not submit the questionnaire but provided enough information to include in state cancer registry linkages, and 4% had incomplete enrollment. The largest attrition occurred at the work history section of the questionnaire, but completion rates were generally similar by demographic and occupational characteristics. A department roster-based recruitment method resulted in a slightly lower self-reported cancer prevalence through exploratory analyses, suggesting possible reduction of selection bias by cancer status. CONCLUSIONS: Findings demonstrate national engagement and high completion rates in a large, voluntary occupational registry. Continued recruitment, particularly among volunteer firefighters and other underrepresented groups, will strengthen the NFR's utility for analyzing cancer and cancer risk factors among U.S. firefighters.