ARI SHAPIRO, HOST:
The U.S. military is speaking publicly for the first time about the potential health risks of firing certain heavy weapons. These shoulder-fired large guns produce a powerful explosion just inches from the shooter's head. As NPR's Jon Hamilton reports, the military is investigating whether just pulling the trigger can injure the brain.
JON HAMILTON, BYLINE: In Iraq and Afghanistan, the military learned a lot about what a big explosion can do to the brain.
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HAMILTON: Roadside bombs were the major threat, says Tracie Lattimore, who directs the Army's traumatic brain injury program.
TRACIE LATTIMORE: We were totally concerned about the enemy weapon and the impact of the enemy weapon on our soldiers.
HAMILTON: But Lattimore says now military officials are turning their attention to explosions from the weapons fired by U.S. forces, weapons like the Carl Gustaf, a gun so powerful it can blow up a tank.
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LATTIMORE: We also now recognize for the first time maybe we should be also looking at our weapons.
HAMILTON: The blast from firing some of these weapons contains as much energy as a small bomb. Gunners say it feels like a punch to the face. And studies by the military show that service members who fire these weapons a lot can experience headaches, temporary memory loss and other symptoms like those of a concussion. Military officials have been reluctant to speak publicly about the risks. But in an interview with NPR, Lattimore says they are concerned.
LATTIMORE: We are leaning in and trying to do everything in our power to protect soldiers and service members while they continue to get their job done.
HAMILTON: Lattimore, who works in the office of the Army surgeon general, says that means getting answers to some basic questions about firing heavy weapons.
LATTIMORE: Is blast exposure hurting service members or soldiers? And if it is, what are those thresholds, and how can we hone in on those? And then how can we modify our equipment or the way we operate to prevent injury?
HAMILTON: The risk comes from the invisible pressure wave generated by an explosion. If this wave is strong enough, it can travel through the skull and damage brain tissue. David Brody is a neurologist at the Uniformed Services University in Bethesda where the military trains its health professionals and scientists. He says there's no doubt that the blast wave from a roadside bomb can damage the brain. But he's not so sure about the blast wave from a heavy weapon.
DAVID BRODY: There is no consensus. There is not a real solid understanding of what these blast exposures do, if anything.
HAMILTON: Brody says there is reason to suspect that lots of relatively small blasts from firing an antitank weapon might have the same effect on the brain as one big blast from a bomb. The model is football players. Studies have shown that thousands of relatively minor head impacts during a player's career can cause the same sort of long-term brain problems associated with full-blown concussion. To find out how much blast exposure troops are getting from heavy weapons, the military is using a device known as a blast gauge.
They first tried them in 2011 in Afghanistan. Wearable gauges placed on thousands of troops recorded the intensity of blasts from roadside bombs. And surprisingly, the gauges also detected strong blast waves reaching the heads of some soldiers who fired antitank weapons. The Army says it was hard to collect useful data in the chaotic environment of the battlefield, but Brody says weapons training offers a more controlled setting.
BRODY: That's the scientific program going forward, is to get blast gauges on these service members and measure their lifetime history of blast exposures.
HAMILTON: The Army's Tracie Lattimore says the military plans to use a new version of the gauges as part of a major study of blast exposure that was ordered by Congress late last year. And she says military researchers are already using the devices to help troops avoid excessive blast exposure during weapons training.
LATTIMORE: So if our researchers are out on a range and they see a reading that is higher than what we anticipated, they can pause the training.
HAMILTON: To figure out why and fix the problem. Lattimore says the military's view of the risk from blast waves has changed a lot.
LATTIMORE: We are in a different place now than we were five years ago or 10 years ago.
HAMILTON: But she says the military's mission hasn't.
LATTIMORE: And so there's these pressures between being maximally protective as we can. But the military has a job to do in terms of preparing for war and go into war. And that is an inherently risky business.
HAMILTON: Lattimore says when it comes to firing heavy weapons, the question now is, how risky? Jon Hamilton, NPR News.
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