When wildlife biologist Mourad Gabriel finds a Gatorade bottle nestled among leafy green plants on public land, that’s a very bad sign. In most cases, in his line of work, it’s not just some litter. It’s a container for carbofuran, a neurotoxic insecticide you definitely should not ingest to improve your athletic performance.

These bottles are lying around national forests and parks because they’re being toted in by illegal pot farmers, who care about the environment as much as they do about the law. To protect their crops and campsites, they often rely on dozens of nasty chemicals, which are killing animals, lingering in the soil and threatening to contaminate towns’ water supplies.

Gabriel, executive director of the nonprofit Integral Ecology Research Center, never imagined his scientific work would entail taking part in federal raids with a pistol in his holster. But everything changed in 2009, explains writer Julian Smith in his profile of Gabriel for biographic.com.

That’s when the researcher examined a dead Pacific fisher – a small, carnivorous mammal – and realized it was full of a rodenticide that’s illegal to sell in the United States. As more poisoned fishers showed up, Gabriel went searching for an explanation.

It turns out that despite the legalization of pot in California, there’s still a lot of illegal stuff being grown there, and often on public lands. Law enforcement’s theory, Smith writes, is that the culprits are mostly Mexican drug cartels that “prefer to ship marijuana from state to state rather than smuggle it over the international border.”

Pinpointing and eradicating these campsites is a pretty dangerous business, both because of the potential for violence and the hazards of handling the chemicals involved. But Gabriel has made it his mission to keep at it and maintain a public profile, despite repeated threats against his family. (In 2014, someone even poisoned his dog, authorities said.)

There has to be someone out there searching for Gatorade bottles. Smith quotes Craig Thompson, a wildlife ecologist with the U.S. Forest Service, who said he is terrified about what could happen if a child stumbles across them first: “Carbofuran is pink, it looks like Pepto, like candy. Can you imagine what a 5-year-old would do with that?”