CNN investigated the vaping black market and independently hired a lab to test vaping cartridges for contaminants, including heavy metals and pesticides.

CNN obtained five THC cartridges from an illegal vape shop and had their contents tested at BelCosta Labs, one of California’s certified labs that approves cannabis products for consumer use. The results showed that the cartridges all contained a variety of pesticides that exceed the legal amount.

“When you concentrate the THC, you concentrate everything along with it,” said Myron Ronay, who runs BelCosta Labs. “So every pesticide that could’ve been in that plant material — if it went from, let’s just say 20% THC, and now you’ve concentrated it to 80% THC — you’ve also concentrated the pesticides that same amount.”