Last year, a study by the U.S. Armed Forces revealed firing heavy weapons can cause memory and learning problems, but signs indicate it may also increase the risk of brain injury for soldiers across New Mexico and the United States. Per NPR, much of the concern centers around a military weapon known as the Carl Gustaf, which releases an explosive stream of hot gas out its back after shooting at a speed of more than 500 mph.

Concerns about the weapon’s effects on those firing it first began to circulate after the wars in Iraq and Afghanistan, prompting members of Congress to take action. They did so by equipping soldiers with sensors known as blast gauges. Though the gauges were originally intended to assess how soldiers were affected by roadside bombs, they ultimately revealed troubling findings about the possible risk between repeated use of heavy weapons and brain injury.

The sensors are no longer broadly used, however. Despite congressional disapproval, they were taken out of wide circulation after the military felt the results they produced were inconclusive. A possible explanation for the lack of clear results is the fact that there are so many variables that must be taken into account on a battlefield, making it hard to determine exact causation. For example, soldiers who fire heavy weapons close to buildings may feel more effects from doing so than a soldier firing the same weapon without structures around to reflect its waves.

If soldiers are putting themselves at risk of brain injury by firing heavy artillery such as the Carl Gustaf, they risk serious injury and even death. The Brain Injury Association of American reports that 19 percent of brain injuries in America are currently caused by unknown means, but that 280,000 people are hospitalized and 52,000 people die from them each year.