Fiscal Year 2018 National Defense Authorization Act, Section 734, Weapon Systems Line of Inquiry: Overview and Blast Overpressure Tool-A Module for Human Body Blast Wave Exposure for Safer Weapons Training.

INTRODUCTION: Experiences by service members in recent conflicts and training environments illuminate concerns about the possible effects of blast overpressure (BOP) exposure on brain health. Section 734 of the National Defense Authorization Act for Fiscal Year (FY) 2018 (Public Law 115-91) requires that the Secretary of Defense conducts a longitudinal medical study on blast pressure exposure of members of the Armed Forces during combat and training, and the Assistant Secretary of Defense for Health Affairs was assigned responsibility for fulfilling requirements. The study's goal is to improve DoD's understanding of the impact of BOP exposure from weapon systems on service members' brain health and inform policy for risk mitigation, unit readiness, and health care decisions. This article focuses on the activities of the Weapon Systems Line of Inquiry (LOI) and the development of a prototype BOP Tool. MATERIALS AND METHODS: The DoD established the Section 734 Workgroup, which developed a program structure with five LOIs. The Weapon Systems LOI coordinated, collated, and analyzed information on BOP resulting from heavy weapons and blast events to inform strategies, and accounted for emerging research on health effects and performance. Ongoing research was leveraged to develop a BOP Tool as a standalone module and for integration into the Range Managers Toolkit. RESULTS: The effort identified opportunities for the DoD to improve the clarity of communications about BOP exposure, risk, and safety; establish methods to leverage emerging research; and develop a prototype BOP Tool to predict exposure loads when firing heavy weapons in training. CONCLUSIONS: It is recommended that the DoD revises requirements and policy to improve and standardize safety guidance throughout research, development, testing, and evaluation; acquisition; and training. The validated BOP Tool allows users to generate a scenario to predict BOP exposure and allows service members to modify them during planning for safer training.

Acute Hearing Deficits associated with Weapons Exposure in Section 734 Blast Overpressure Study (BOS).

INTRODUCTION: This prospective, multi-site, observational study describes ongoing efforts in support of the Fiscal Year 2018 National Defense Authorization Act (NDAA) Section 734 Blast Overpressure Study (BOS) to identify the acute effects impulse and blast exposure have on hearing abilities of the Warfighter in various military training environments. MATERIALS AND METHODS: Hearing thresholds, a binaural tone detection task, and auditory symptoms were collected before and immediately following weapons exposure across nine military training environments from January 2020 to October 2022. An additional 25 non-exposed control participants also completed the behavioral test battery. A boothless audiometer was used to measure hearing ability in the field. Sound level meters were attached on-body to record the exposure environment throughout training. RESULTS: Mean threshold change for the blast-exposed group was worse than the control group. Of the 188 blast-exposed participants, 23 experienced a temporary threshold shift (TTS) acutely after exposure. A decrease in binaural tone detection performance and increased symptom severity was found when comparing blast-exposed participants with a TTS versus those without a significant change in hearing. A complex but consistent relationship between measured exposure level (LAeq8hr) and the magnitude of the resulting TTS is suggested in the available data. CONCLUSIONS: Recent discussions on Section 734 studies examining the effects of repetitive blast exposure have indicated that hearing-related issues were a critical problem that needed additional research. Study outcomes provide highly repeatable results across various weapons systems with hazardous blast exposure. This standardized set of hearing assessment tools for evaluating acute effects of noise under field conditions has been critically important in improving our understanding of TTS in prospective human subject research.