The Two Pathways

A heavy-metals standard has to answer a question every category asks differently: how clean is achievable here, today, without certifying nothing or certifying everything? HMTc answers it with two pathways. The choice between them is the single most consequential decision in setting a limit, so it is worth being explicit about both the intent and the mechanism.

Lead with the pass rate, not the percentile

The pathways are easiest to understand as pass-rate targets:

• A clean subcategory is one where good product is the norm and contamination is the exception. The standard should pass roughly the cleanest 90% of the market and exclude the dirtiest tail. The mechanism that delivers that is the 97th percentile (P97) of the subcategory’s occurrence distribution.
• A dirty subcategory is one where contamination is endemic — to the soil, the commodity, or the process — so that demanding near-zero on day one would certify almost nothing. The standard should pass roughly the cleaner 30% of the market and put the rest on notice. The mechanism is the 45th percentile (P45).

The percentile is not the goal; the pass rate is. P97 and P45 are the levers calibrated to hit ~90% and ~30% against real occurrence distributions.

Why a dirty pathway is not a loophole

A P45 limit looks permissive next to P97, and out of context it could read as the certifier lowering its standards where the data is bad. It is the opposite. In an endemic category, a P97 limit would pass nearly everything — it would certify the status quo and change nothing. A P45 limit fails the majority of current product on purpose. It is the ratchet’s first turn: it rewards the cleaner end of a dirty category, creates a commercial reason to source and process toward cleaner inputs, and tightens across editions as the category responds. The honest framing — this category is dirty, here is how dirty, here is the limit and why it sits where it does — is exactly the record that holds up when the standard is challenged.

Independent rows default to clean

A row with no within-pair partner is treated as clean by default and set at P97, with an override slot where the evidence justifies dirty treatment. Clean-versus-dirty is a category-level judgment resolved in governance review, not a per-row convenience — which is why a row whose pairing is unsettled is held at gate one rather than shipped on a guess.

After publication: ALARA and the ratchet

Neither pathway is a resting place. Once a limit publishes, an ALARA review (“as low as reasonably achievable”) and an 80th-percentile ratchet trigger drive tightening in later editions as the category’s distribution shifts cleaner. A standard that never moved would, over time, certify a market that had moved on without it.

For the breadth side of the same argument — why the panel grew from four metals to ten, and why a one-time test is weaker than a surveillance record — see Four Metals Is No Longer Enough and The Surveillance Protocol.