Heavy metal testing

Heavy metal testing quantifies toxic metal contaminants in cannabis, focused on the "Big Four" — lead, cadmium, arsenic, and mercury — classified as FDA Class 1 elemental impurities and regulated under USP General Chapters <232>/<233> for pharmaceuticals. Cannabis sativa is a bioaccumulator and hyperaccumulator, used deliberately for phytoremediation of contaminated soil; metals enter the plant through roots from soil, irrigation water, fertilizers (especially phosphate-based), contaminated growing media, or finished-product processing equipment (solder, brass vape cartridge fittings). The standard analytical method is Inductively Coupled Plasma–Mass Spectrometry (ICP-MS) following microwave-assisted acid digestion (typically nitric acid plus hydrochloric acid at 200°C), achieving sub-ppb sensitivity. AOAC First Action 2021.03 validated microwave-digestion/ICP-MS for these four metals in cannabis. California's inhalable-product action limits are mercury 0.1 μg/g, arsenic 0.2, cadmium 0.2, and lead 0.5. Health effects are severe: lead causes neurological and developmental damage; cadmium is a known carcinogen and nephrotoxin; arsenic is carcinogenic to lungs, skin, and bladder; mercury is a potent neurotoxin. SC Labs found 11% of rolling papers alone would fail heavy-metal testing. → See also: Testing lab, COA, Pesticide testing