There’s a harsh downside to the boom in marijuana legalization and use on the West Coast: Illegal growers are polluting the environment to an alarming degree and threatening the health of people and rare wildlife in the process.

Mourad Gabriel, an ecologist with the Integral Ecology Research Center in northwest California, told Reuters the problem is much worse than researchers and officials previously thought. He estimates illegal marijuana sites on federal land in California—where most of these pot-growing farms are found—contain 731,000 pounds of solid fertilizer, 491,000 ounces of concentrated liquid fertilizer and 200,000 ounces of toxic pesticides. This waste is potent enough to harm law enforcement officials investigating the crops; contact with these toxic materials during raids or searches of illegal marijuana farms has sent at least five officials to the hospital for skin rashes and trouble breathing, according to Reuters.