Traumatic brain injury (TBI) is the signature wound of today’s wars, with nearly 380,000 servicemembers diagnosed since 2000. TBI can come from falls, bullets shrapnel, or the blast pressure wave that comes from explosions, such as from enemy improvised explosive devices (IEDs). New research has also shown that servicemembers may experience cognitive deficits after firing heavy weapons, such as shoulder-fired recoilless rifles, even in training.
Recent Department of Defense (DoD) studies have demonstrated that some servicemembers experience cognitive deficits in memory and executive function after firing heavy weapons in training, even within allowable firing limits. After 96 hours, cognitive functioning returned to baseline, but the long-term effect of repeat exposure is unknown. There is cause for concern.
{mosads}Another DoD study found higher rates of concussion-associated symptoms among individuals with a history of prolonged exposure to low-level blasts from breaching and shoulder-fired weapons.
In other areas, such as sports, scientists are learning more about the harmful effects of repeated, low-level impacts on the brain. DoD animal studies have confirmed this relationship for blast waves, showing cumulative effects from repeated blast exposures over consecutive days. The authors of one DoD study concluded that repeated, low-level blast exposures was “a potential occupational medicine concern.”
The DoD must urgently take steps to mitigate any potentially harmful effects from blast exposure. Congress recently mandated that DoD launch a longitudinal medical study to better understand the effects of blast exposure on the brain. This study is vitally important, but it will likely take years before scientists fully understand precisely how blast waves affect the brain. In the meantime, there are a number of steps that DoD can take today.
The DoD must immediately institute improved safety standards for firing heavy weapons, including lowering firing limits below the threshold for causing negative cognitive effects. Additionally, current firing limits only apply to the maximum number of shots in a 24-hour period. Firing limits should be changed to cover exposures over a longer-time period, to account for the up to 96 hours it can take for servicemembers to reset to baseline. The DoD should also establish an annual and lifetime limit for blast exposure, both for breaching and shoulder-fired weapons.
Even with these adjusted limits, given the risk that servicemembers may develop symptoms years later, DoD should establish a blast exposure record for individual servicemembers.
DoD has developed wearable blast gauges that measure the overpressure levels servicemembers are exposed to when a blast wave hits them. These gauges can be used to create a quantitative record of exposures, which will be vitally important for servicemembers to receive medical care if they develop symptoms later. Congress should pass legislation establishing a comprehensive blast surveillance program to monitor, record, and maintain data on any soldier who is likely to be exposed to blasts in training or in combat.
Given what we now know about the negative cognitive effects of blast exposure on servicemembers’ brains, it would be negligent for DoD to subject servicemembers to these blasts and not record this exposure.
Finally, DoD should establish a design requirement for combat helmets to protect against blast waves. Computer models have shown that improved helmet designs, such as with full-face shields, can reduce the amount of pressure transmitted to the brain by up to 80 percent. Full-face helmets have other tradeoffs, including added weight and reduced visibility, so DoD should conduct a tradespace study to evaluate these tradeoffs and then establish a minimum protection level.
Currently, combat helmets have design requirements for protecting against bullets, shrapnel, and injury from impacts, but not blast pressure. This protection gap means that combat helmets are not designed to mitigate blast pressure waves, an unacceptable shortcoming given emerging knowledge about the harmful effects of blast overpressure.
Military service is inherently dangerous, but the nation owes its servicemembers the best possible protection. Servicemembers should not be placed in harm’s way unless necessary, and when they do suffer injuries, the country owes them appropriate care afterward. The DoD is not meeting these standards today when it comes to protecting warfighters from blast-induced brain injury.
This is not the first time that servicemembers have been exposed to occupational hazards that were later found to cause negative health effects. In past episodes, such as Agent Orange in Vietnam, Gulf War Syndrome, and burn pits in Iraq and Afghanistan, the DoD and VA have been slow to react, leaving servicemembers and veterans to fight for appropriate care. The DoD must do better this time.
Paul Scharre and Lauren Fish are researchers at the Center for a New American Security (CNAS). They are the authors of the recent CNAS report, “Protecting Warfighters from Blast Injury,” part of the Super Soldiers series.