US Department of Defense
Advancing Blast Injury Research to Protect and Heal Those Who Serve

Impact of Repeated Blast Exposure on Lung Function, Pathology, and Behavioral Changes

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Service members exposed to blast may experience devastating health consequences, including organ injury and long-term disabilities. Blast exposures can result from a single sudden event such as contact with an improvised explosive device, or more subtly over time through repeated blast overpressure (BOP) exposures associated with heavy weapon systems or breaching operations in training. At present, the military does not have set guidelines for exposure limits to repeated blasts for Service members. While several past and current studies investigate the impact of blast exposure on the brain, the extent of research on blast-induced lung damage has been less comprehensive.

To address this need, researchers at the Walter Reed Army Institute of Research1 conducted a study to develop pulmonary injury risk curves and assess both the pathophysiology of the lung and behavioral outcomes associated with repeated low-level blast exposures. Using an advanced blast simulator, rodents were exposed to BOP once or repeatedly and either frontally or from the side at varying peak overpressure levels (8.5-19 psi). Results showed the following:

  • Behavior Function: An open field assessment showed that 24-hours after their final BOP exposure, rodents exhibited a significant reduction in exploratory behavior after exposure to repeated BOP at the highest overpressure level; however, no changes were observed after repeated BOP exposures ranging from 8.5-16 psi, nor after any single BOP exposure.
  • Lung Impact: Single and repeated BOP exposures at or above 13 psi caused lung injury, with contusions and hemorrhage being more apparent with side orientation blast exposures. Repeated, lower-level exposures did not cause comparable damage.
  • Pathology: Hematoxylin and eosin staining were performed to ascertain cell morphology and inflammatory changes. Significant changes were observed at or more than 10 psi and orientation effects were seen at blast exposure levels higher than 13 psi.

Data modeling indicates that the injury threshold may be defined at 50 exposures at 8 psi for frontal exposures to blast and at 6.5 psi for side exposures, as illustrated in Figure 1. This study will need to be further validated with large animal experimental data and by assessing varying blast overpressure waveforms. Exposure guidelines have been codified for the impact of noise on hearing and auditory functioning; however, it will be appreciably and additionally beneficial to further establish exposure thresholds based upon blast injury, in addition to lung injury, to the brain and other sensory systems, as addressed in these ongoing experiments, to protect and preserve the health of Service members.

Boundary curves between not injured and injured
Figure 1. Graphs show boundary curves between not injured and injured based on number of BOP exposures
and peak pressure (A) frontal (head-on) orientation (B) lateral (side) orientation.

This work was supported/funded by work unit number 602115HP.3720.001.A1317 as part of the Exposure Standards for Repeated Blast program which is funded by the Defense Health Program and managed by Joint Program Committee-5.


1 Sajja, V.S., Statz, J.K., Walker, L.P.B. et al. Pulmonary injury risk curves and behavioral changes from blast overpressure exposures of varying frequency and intensity in rats. Sci Rep 10, 16644 (2020). doi: 10.1038/s41598-020-73643-7.

Last modified: 14-Dec-2020