Josh Swider runs the licensed licensed pot lab InfiniteCal. He’s been testing street-market THC cartridges for several years. InfiniteCal has consistently found high levels of metals and pesticides in them.

Last autumn, InfiniteCal tested 30 THC carts obtained from the illicit street market in a buyback program ran by Mankind dispensary in San Diego. The results: 79% of the carts failed California testing standards. Every street cart contained vitamin E acetate—from trace amounts up to 20%. More than 60% of street carts failed for pesticides. One cart had 87 times the allowable limit for lead.