美国国家公共电台 NPR Do U.S. Troops Risk Brain Injury When They Fire Heavy Weapons?（在线收听）

RACHEL MARTIN, HOST:

Battlefield weapons have been getting smaller and more powerful as technology has improved. But now the military is trying to figure out whether some modern weapons actually pose a danger to troops. NPR's Jon Hamilton reports that these portable weapons are so powerful that just being near one of them when it's fired can rattle the brain.

JON HAMILTON, BYLINE: The Army is about to expand its use of a Swedish weapon called the Carl Gustaf. It looks like a bazooka. It can be carried by a single soldier.

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UNIDENTIFIED MAN: All right. Ready to fire.

HAMILTON: And as this military training video shows, it can blow up a tank.

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UNIDENTIFIED MAN: Backblast area clear?

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HAMILTON: A single round for the Carl Gustaf can weigh nearly 10 pounds. The shell leaves the barrel at more than 500 miles per hour. And as it fires, the weapon directs an explosive burst of hot gases out the back of the barrel. Troops take positions to the side of the weapon for safety. Even so, they get hit by powerful blast waves. In a video made by the military, here's how one Army gunner in Afghanistan described the experience.

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UNIDENTIFIED SOLDIER: Whenever you shoot it and it goes off, it feels like you get punched in your whole body. Like, the blast bounces off the ground, and it overwhelms you.

HAMILTON: During the wars in Iraq and Afghanistan, the military realized that the blast wave from a roadside bomb could injure the brain without leaving a scratch. And they began to wonder whether repeated blasts from a weapon like the Carl Gustaf might do the same thing. Louise Slaughter, a congresswoman from upstate New York, is a member of the Congressional Brain Injury Task Force.

LOUISE SLAUGHTER: With the use of the Carl Gustaf, I was told that one soldier that used it - his ears bled. Obviously, we have to know what kind of damage is that doing to their soldiers in training and in the battlefield.

HAMILTON: The military says it also wants to know whether firing a weapon could injure a service member's brain. They've already found hints that it might. In Afghanistan, the Army equipped thousands of troops with coin-sized sensors worn on the head and shoulders. These blast gauges, made by a company in Slaughter's district, were designed to measure the intensity of a blast from a roadside bomb. But they also revealed worrisome levels of blast exposure among troops who were merely firing certain heavy weapons.

Last year, the military pulled the blast gauges from wide use, saying they hadn't helped detect brain injuries. Slaughter thinks that was a mistake.

SLAUGHTER: I don't understand the Pentagon's circular argument that they aren't using the gauges that they have already purchased because they don't have the data to prove how effective they are. But it doesn't take a great brain to understand you will not get the data if you don't use the gauges.

HAMILTON: The military declined several requests for an interview about the blast gauge program and the risks from firing weapons. But an Army spokesperson did respond to questions in an email. She said that the Department of Defense is still using blast gauges in research studies, including some that look at exposure from firing weapons.

Laila Zai is a scientist at Applied Research Associates, a private company hired by the military to help figure out the link between blast exposure and traumatic brain injury. She says some service members have reported concussion-like symptoms after repeatedly firing heavy weapons.

LAILA ZAI: The reason that these studies are being done is because at some point someone has said, I don't feel quite right.

HAMILTON: But it's really tricky to turn these anecdotes into usable data. Even results of the Army's own blast gauge program in Afghanistan are hard to interpret because there were so many variables on the battlefield, so Zai has been working with a researcher from the Navy.

ZAI: What he's doing is he's putting sensors on people undergoing shoulder-mounted weapons training.

HAMILTON: The sensors measure the force of a blast, known as overpressure.

ZAI: And he's looking to see if the overpressure generated by various training scenarios ever overwhelms the threshold of safety.

HAMILTON: It's all part of a five-year, $30 million effort run by the Office of Naval Research. The goal is to help the military figure out how much blast exposure is too much. Last year, a different military study showed that firing heavy weapons could temporarily impair learning and memory. Congresswoman Slaughter says now the military needs to find out whether these short-term effects can lead to long-term injuries for service members.

SLAUGHTER: And if we can save them from a lifetime of brain damage, for heaven's sakes, it's our obligation to do it.

HAMILTON: Sweden, the home of the Carl Gustaf, isn't waiting for definitive science. Troops there who train with the weapon have a strict limit on the number of rounds they can fire each day. Jon Hamilton, NPR News.