TBI (Traumatic Brain Injury) can come from many causes: falls, vehicle accidents, bullets, shrapnel, etc. In recent years, researchers have begun to understand that the primary blast pressure wave from explosions can also damage the brain, although the specific mechanism of injury from blast pressure is poorly understood.

Most concerning, emerging evidence suggests that service members may be exposed to significant levels of blast overpressure when firing heavy weapons, such as recoilless rifles, even in training.

Recent Defense Department studies have found that blast exposure from firing heavy weapons in training, such as the Carl Gustaf recoilless rifle, is associated with short-term cognitive deficits.

Even when used within currently approved firing limits, DoD studies have demonstrated that some service members may experience short-term deficits in delayed verbal memory, visual-spatial memory, and executive function after firing heavy
weapons.

Service member cognitive deficits following a single day of heavy weapons firing in training took 72 to 96 hours to resolve to a level at which they were not statistically significant.

Other DoD studies have found higher rates of concussion and post-concussion associated symptoms among individuals with a history of prolonged low-level blast exposure from breaching and shoulder-fired weapons.

The study’s authors concluded that the findings “support the hypothesis that there is a positive relation between the amount of blast exposure and reported symptoms.”   They noted that those repeatedly exposed to low-level blasts from breaching or shoulder-fired weapons could face “a potential occupational medicine concern.”

Animal studies have also provided evidence of the cumulative effects of repeat, low level blast exposures.

In large animals (such as a pig), three exposures in a day can result in a 30 percent to 40 percent greater physiological change than a single exposure, meaning more exposures lowered the threshold for injury. Additionally, these studies showed 24 hours was insufficient to recover from blast-related effects.

However, research in this area is still nascent, and scientists understand very little about the injury mechanism — how blast exposure directly translates to these cognitive deficits and symptoms. Scientists need more data to better understand the effect of blasts on the brain.

This gap in data led to a previous deployment of blast gauges worn on soldiers to quantify the exposure, including overseas in combat, but this Army program ended last fall. The DoD is currently studying blast pressure exposure in training when firing heavy weapons.

Enemy-initiated blast events have different pressure signatures, however, making it critical to record data on combat blast events when they occur.

As with other occupational hazards that service members face in the service of their country, the effects of blast exposure will take years to understand.

Vietnam veterans were exposed to the defoliant Agent Orange, which is linked to at least a dozen health problems — including multiple types of cancer.

Veterans suffering from Gulf War Syndrome, which is linked to unexplained illnesses, including chronic fatigue and fibromyalgia, have struggled to get approval from the Department of Veterans Affairs (VA) for claims. The VA is conducting a follow-up study to better understand Gulf War veterans’ health.

Soldiers in Iraq and Afghanistan were harmed in burn pits, which burned all types of trash, including human waste. Studies are ongoing into the long-term effects of this exposure, and the VA is considering compensation on a case-by-case basis.

Unfortunately, in all of these cases, it has taken years for the DoD and VA medical community to fully understand these occupational hazards. In many cases, veterans still struggle to receive the care they require and deserve.  The 2018 National Defense Authorization Act (NDAA) requires a longitudinal study of service member exposure to blast pressure during training and combat.