In a squat rig fitted with a 5,000-gallon tank, Peter crisscrosses the expanse of farms and woods near the Ohio/West Virginia/Pennsylvania border, the heart of a region that produces close to one-third of America’s natural gas. He hauls a salty substance called “brine,” a naturally occurring waste product that gushes out of America’s oil-and-gas wells to the tune of nearly 1 trillion gallons a year, enough to flood Manhattan, almost shin-high, every single day. At most wells, far more brine is produced than oil or gas, as much as 10 times more. It collects in tanks, and like an oil-and-gas garbage man, Peter picks it up and hauls it off to treatment plants or injection wells, where it’s disposed of by being shot back into the earth.

One day in 2017, Peter pulled up to an injection well in Cambridge, Ohio. A worker walked around his truck with a hand-held radiation detector, he says, and told him he was carrying one of the “hottest loads” he’d ever seen. It was the first time Peter had heard any mention of the brine being radioactive.

The Earth’s crust is in fact peppered with radioactive elements that concentrate deep underground in oil-and-gas-bearing layers. This radioactivity is often pulled to the surface when oil and gas is extracted — carried largely in the brine.

In the popular imagination, radioactivity conjures images of nuclear meltdowns, but radiation is emitted from many common natural substances, usually presenting a fairly minor risk. Many industry representatives like to say the radioactivity in brine is so insignificant as to be on par with what would be found in a banana or a granite countertop, so when Peter demanded his supervisor tell him what he was being exposed to, his concerns were brushed off; the liquid in his truck was no more radioactive than “any room of your home,” he was told. But Peter wasn’t so sure.