How limits are set
The standard for each analyte is the strictest maximum level set by any credible government regulator, among them the European Union, Codex Alimentarius, the US FDA, Australia/New Zealand, the Gulf states (GSO), and the national authorities of every jurisdiction that regulates the product, converted into Fermentation-derived / single-cell protein ingredients (precision-fermented, cultured, yeast-biomass proteins)’s own as-sold basis. It is a lookup of sovereign law, carrying at most one disclosed basis conversion where the law is written in another basis, and an explicit read-across where no government regulates the exact product. A certified product sits at or below every applicable sovereign limit at once.
Where no government regulates the exact product for an analyte, the standard does not go blank or invent a number: the limit is read across from the nearest government value for an analogous product, so a certified product still sits at or below a real sovereign limit. The ratchet tightens these after publication as surveillance warrants.
Master Limit Table
All values in ppb (µg/kg), as-sold basis. 9 of 11 analytes carry a firm ceiling; the remaining 2 are toxic species bounded by their parent totals (species ≤ total, measured on every lot), so every analyte carries an enforceable ceiling. A brand meeting every value on a like-for-like basis qualifies for the mark.
| Analyte | Tier | HMTc limit | Binding basis |
|---|---|---|---|
| Lead (Pb) | Tier 1 | 20 | government read-across (Hong Kong) |
| Cadmium (Cd) | Tier 1 | 40 | government read-across (EU) |
| Total arsenic (tAs) | Tier 2 | 100 | government read-across (Paraguay) |
| Inorganic arsenic (iAs) | Tier 1 | 100 | government read-across (Israel) |
| Mercury, total (tHg) | Tier 1 | 20 | government read-across (Hong Kong) |
| Methylmercury (MeHg) | Tier 1 | bounded | ≤ total tHg, measured every lot (see note) |
| Nickel (Ni) | Tier 2 | 800 | government read-across (EU) |
| Tin (Sn) | Tier 2 | 250000 | government read-across (Singapore) |
| Aluminium (Al) | Tier 2 | 100000 | government read-across (China) |
| Total chromium (Cr) | Tier 2 | 500 | government read-across (Hong Kong) |
| Hexavalent chromium (Cr-VI) | Tier 2 | bounded | ≤ total Cr, measured 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. Pet food is legally feed; HMTc voluntarily certifies each analyte to the strictest human-food sovereign maximum for the nearest analog, with the laxer feed-law floor disclosed for contrast. Inorganic arsenic and hexavalent chromium are reflex-speciation screens bounded by total arsenic and total chromium; methylmercury is bounded by total mercury. Nickel, tin and aluminium carry disclosed read-across limits where no government sets a general pet-food maximum.
Derivation
The full derivation for Fermentation-derived / single-cell protein ingredients (precision-fermented, cultured, yeast-biomass proteins). Each row lists every government maximum level in force worldwide, converted to the as-sold basis; the HMTc limit is the strictest of them, and the last column names which sovereign law binds. A blank cell means that government sets no limit for this analyte in this product.
| Analyte | EU | AU/NZ | GSO | China | India | Mercosur | Israel | Morocco | Panama | Philippines | Paraguay | Singapore | Thailand | Vietnam | Hong Kong | CU | CO | HMTc | Binds |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Lead (Pb) | 100 | 200 | 100 | — | 100 | 100 | 100 | 900 | 100 | 100 | 100 | — | 100 | 100 | 20 | 100 | 200 | 20² | read-across |
| Cadmium (Cd) | 40 | 100 | 100 | 200 | 100 | 100 | 100 | 100 | — | 100 | 100 | — | 100 | 100 | 100 | 100 | 100 | 40² | read-across |
| Total arsenic (tAs) | — | 1000 | — | — | — | 100 | 1000 | — | — | — | 100 | — | — | — | 500 | — | — | 100² | read-across |
| Inorganic arsenic (iAs) | 150 | — | 200 | — | — | — | 100 | — | — | 200 | — | 200 | 200 | — | 200 | — | — | 100² | read-across |
| Mercury, total (tHg) | — | — | 1000 | — | — | — | 30 | — | — | — | — | — | — | — | 20 | — | — | 20² | read-across |
| Methylmercury (MeHg) | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | bounded&sup5; | species ≤ tHg |
| Nickel (Ni) | 800 | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 800² | read-across |
| Tin (Sn) | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 250000² | read-across |
| Aluminium (Al) | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 100000² | read-across |
| Total chromium (Cr) | — | — | — | 1000 | — | — | — | — | — | — | — | — | — | — | 500 | — | — | 500² | read-across |
| Hexavalent chromium (Cr-VI) | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | bounded&sup5; | species ≤ Cr |
All values µg/kg (ppb), as-sold basis. ² no government regulates this analyte for this exact product form: the value is a disclosed read-across from the nearest applicable government maximum, and the derivation names the instrument it comes from. It is never taken from occurrence data. After publication the standards ratchet may tighten it, using certified-lot results only. ³ not material in this matrix: measured but with no standalone number, controlled by packaging control or by the total-metal screen, not an invented value. &sup5; a toxic species governed by and bounded by its parent total (for example inorganic arsenic ≤ total arsenic): the species can never exceed the total, so the total ceiling is the species ceiling. The total metal is measured on every lot and the species is established at baseline; no separate species ceiling is published. On ongoing lots the species is speciated whenever the total exceeds its limit.
Risk Flag
Where certification is demanding for this subcategory, and why. The load here is set by process inputs rather than a market background, so it is controllable but real. A product is not disqualified by this: only its own tested result decides certification, and a well-sourced lot can sit well below the market.
A process that concentrates metals from its inputs
A precision-fermented single-cell protein carries no lifetime environmental accumulation, so its heavy-metal load is set entirely by its inputs: a control lever, not a guarantee of cleanliness. The yeast biomass actively concentrates metals from its growth medium: cell-wall biosorption pulls in lead, cadmium, and nickel, and inorganic arsenic is imported through the phosphate-uptake pathway, so a phosphate-fed fermentation can enrich it. The mineral and nutrient premix is itself a recognised metal vector. The finished protein is only as clean as its sourced-and-tested feedstock and premix: a controllable, input-dependent risk rather than an intrinsic ceiling, which is why every certified lot is assayed against the full panel instead of presumed clean by process. Inorganic arsenic and cadmium are the analytes to watch.
This flag is a mechanism-based caution, not a market survey, and carries no compliance weight. See the cross-category summary.
Cite this standard
Pendergrass, K. “Fermentation-derived / single-cell protein ingredients (precision-fermented, cultured, yeast-biomass proteins).” In Heavy Metal Tested & Certified (HMTc) Pet Foods standard, version 1.0. 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.