Some weapons used by the U.S. military are so powerful they can pose a threat to the people who fire them. When weapons are fired, an invisible blast wave travels through the brains of anyone nearby. Exposure to lots of these blasts over time – even low-level ones – has been shown to cause brain health problems for service members.
Think of it like football: Scientists still see signs of brain damage in players who don't typically get knocked unconscious but take regular, less severe blows to the head. In the military, scientists have measured something called overpressure, essentially the force of a blast. They've seen that it isn't just bombs causing overpressure — it's also the blasts from firing weapons.
These blasts can cause inflammation and damage blood vessels. In 2023, the Department of Defense created a fact sheet for service members that lists symptoms like headaches, memory problems and decreased hand-eye coordination. While the military has adopted a threshold for how much overpressure is considered safe — about four pounds per square inch, which is the level at which overpressure can burst an eardrum — nobody knows yet what that level means for the brain.
In the meantime, the military is working to reduce the risk for service members in training by doing cognitive testing to track brain changes and putting blast gauges on members who fire heavy weapons in training to better understand how much exposure occurs.
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This episode was produced by Rachel Carlson and edited by our showrunner, Rebecca Ramirez. Jon Hamilton checked the facts. The audio engineer was Kwesi Lee.
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