(Illustration via Pixabay by Mickey Mikolas) field_54b3f951675b3

SHORTLY BEFORE Halloween, Robert Card, a grenade and firearm instructor, walked into Just-in-Time Recreation armed with a semi-automatic rifle, opened fire, and plunged the local community of Lewiston, Maine, into chaos and uncertainty for days.

While the community mourned, researchers at Boston University presented a possible cause: the shooter had CTE, or chronic traumatic encephalopathy, from persistent low-level blasts experienced during his time at the range. However, this theory overlooks a more compelling exposure, with comparable risks, identical symptoms, and a clearer link to violence: Lead.

Symptoms of acute lead exposure run the gamut of cognitive problems; exposures have been linked to feeling confused, more prone to anger and hostility, and issues with thinking straight. It’s been known to significantly impair judgement, impulse control, and critical thinking. Many exposed individuals report feeling anxious and depressed.

Similarly, individuals suffering from CTEs experience confusion, mood swings, paranoia, and, on occasion, increased hostility and violence. Boston University researchers eventually determined Card did not have CTE, but did have symptoms consistent with traumatic brain injuries– a precursor to CTE.

So, where does lead fit into this open-and-shut case? And how does it relate to the Lewiston shooter?

To start, lead has left an indelible mark on the world – as a durable metal, it’s been used in paint, batteries, gasoline, and jet fuel. A well-regarded theory has linked global violence to lead, with substantial reductions after the phase-out of leaded gasoline (otherwise known as “the lead-violence hypothesis.”)

And Card was at great risk of exposure. As an active-duty reservist, his role was petroleum supply specialist. This means he may have come into close contact with lead-containing fuel (e.g, jet fuel is still leaded). This is an incredible exposure source for adults and possibly impacted his daily functioning.

Even more concerning: he spent a considerable amount of time at shooting ranges and grenade courts, exposing him to persistent firearm use.

Firearm use is amongst the most underappreciated sources of lead in the United States, as shooters use lead ammunition and primers almost exclusively. When a gun is fired, that lead dust explodes into the air. This is a major risk factor for shooters, who inhale the dust, exposing them directly. Similarly troubling is when it settles on their clothes and personal effects, which may then travel with the shooter, continually exposing them or their loved ones. In fact, my team recently published a paper indicating that household firearm use may be one of the strongest associated factors in cases of elevated child blood lead levels across the United States. Prior to this discovery, we had found this relationship consistent at the city, town, and state level, alongside evidence of its association with suicide.

To be sure, not everyone exposed to lead will become a mass shooter. The United States is full of hobbyists who enjoy using firearms responsibly and are safety oriented. There are a host of reasons why the shooter did what he did, and exposure to firearms, lead, and his traumatic brain injuries are not the sole causes.

However, the undeniable links between lead exposure, firearm use, and violent injury are concerning, and we should be considering chronic lead exposure (which we can detect easily via portable bone scans and blood tests) in these instances, alongside CTE.

Moreover, it’s of critical importance that individuals who use firearms regularly ensure that they take every precaution available to avoid lead exposure. Make sure to change your clothes immediately after use, especially before going into a dwelling or vehicle. Wash these clothes separately through the washer and make sure to run the washer again afterwards to clean it. Limit the opportunities for this dust to impact your children by restricting cleaning to certain locations. And take the setting of your shooting seriously – if you are indoors, make certain it is well ventilated. Given that lead can linger indefinitely in the environment, it’s of critical importance that communities ensure safe use is prioritized.

Christian Hoover is co-investigator of the Firearm Exposure Research Team at the Harvard Injury Control Research Center. He is also a doctoral student in epidemiology at Brown University School of Public Health.