How every number on this page is set
Cannabis has no uniform federal contaminant limit. Its heavy-metal ceilings are the route-split action levels of the credible sovereign cannabis programs — California (DCC 2026), Colorado (2022), Massachusetts (2020), Maryland (2025), Nevada (2020), and Israel (IMC-GMP 152, 2016). For each analyte the HMTc limit is the strictest maximum any of these governments sets for the product's administration route. The route basis is never conflated: the strict inhaled arsenic and cadmium action levels are never applied to an edible or a topical, and a permissive topical lead level is never applied to inhaled flower. It is a lookup, not a computation; occurrence never selects a value.
Four analytes bind directly to a sovereign action level — lead, cadmium, total arsenic, and total mercury. Total chromium is recorded as a screening ceiling rather than a health limit: it is dominated by benign trivalent chromium while the health-relevant species is hexavalent chromium, so the total-chromium action level is non-protective as a ceiling and any quantifiable Cr(VI) fails certification. Nickel, tin, and aluminium, which no cannabis program regulates for content, are held under mandatory analytical control; inorganic arsenic, methylmercury, and hexavalent chromium are enforced by reflex speciation against their measured total. Certification is heavy-metal safety only and does not endorse the efficacy or the legality of these products.
Master Limit Table
All values in ppb (µg/kg), as-sold basis. 4 of 11 analytes carry a firm ceiling; the remainder are governed by mandatory control or reflex-speciation screening with no standalone number, itemised in the derivation below. A brand meeting every firm value on a like-for-like basis, and passing every control, qualifies for the mark.
| Analyte | Tier | HMTc limit | Binding basis |
|---|---|---|---|
| Lead (Pb) | Tier 1 | 500 | strictest government ML (US-CA) |
| Cadmium (Cd) | Tier 1 | 200 | strictest government ML (US-CA) |
| Total arsenic (tAs) | Tier 2 | 200 | strictest government ML (US-CA) |
| Inorganic arsenic (iAs) | Tier 1 | control | mandatory control — no government ML; screened every lot (see note) |
| Mercury, total (tHg) | Tier 1 | 100 | strictest government ML (US-CA) |
| Methylmercury (MeHg) | Tier 1 | control | mandatory control — no government ML; screened every lot (see note) |
| Nickel (Ni) | Tier 2 | control | mandatory control — no government ML; screened every lot (see note) |
| Tin (Sn) | Tier 2 | control | mandatory control — no government ML; screened every lot (see note) |
| Aluminium (Al) | Tier 2 | control | mandatory control — no government ML; screened every lot (see note) |
| Total chromium (Cr) | Tier 2 | screen | screening ceiling — Cr(VI) is the binding health control (see note) |
| Hexavalent chromium (Cr-VI) | Tier 2 | control | mandatory control — no government ML; screened every lot (see note) |
Tier 1 (Pb, iAs, Hg, MeHg, Cd) are zero-tolerance toxics with no established safe threshold. Tier 2 (tAs, Ni, Sn, Al, Cr, Cr-VI) carry a 150% transitional allowance under the program’s Status A–E framework.
Derivation — the binding sovereign limit
For Cannabis flower and dried herb, each HMTc limit is the strictest maximum level any credible government sets for the product, named in the Binding column with the count of jurisdictions that concur at that value. Where no government regulates the analyte, the cell is a mandatory control or a not-material determination, never an invented number.
| Analyte | HMTc | Binding | Basis |
|---|---|---|---|
| Lead (Pb) | 500 | US-CA | direct sovereign ML |
| Cadmium (Cd) | 200 | US-CA | direct sovereign ML |
| Total arsenic (tAs) | 200 | US-CA | direct sovereign ML |
| Inorganic arsenic (iAs) | control | screened every lot | mandatory control — no government ML |
| Mercury, total (tHg) | 100 | US-CA | direct sovereign ML |
| Methylmercury (MeHg) | control | screened every lot | mandatory control — no government ML |
| Nickel (Ni) | control | screened every lot | mandatory control — no government ML |
| Tin (Sn) | control | screened every lot | mandatory control — no government ML |
| Aluminium (Al) | control | screened every lot | mandatory control — no government ML |
| Total chromium (Cr) | screen | Cr(VI) binds | screening ceiling (US-MD action level 600 µg/kg — non-protective for total Cr); any quantifiable Cr(VI) fails |
| Hexavalent chromium (Cr-VI) | control | screened every lot | mandatory control — no government ML |
Cite this standard
Pendergrass, K. “Cannabis flower and dried herb.” In Heavy Metal Tested & Certified (HMTc) Cannabis, Hemp, and CBD Products standard, version 1.1. Institute of Contaminant Standards (ICS), 2026. DOI: registration pending.
The literature baseline for every analyte is maintained independently at the Heavy Metal Index. This certification standard applies those findings; the two are kept editorially separate by design.