Prop 65 vs USP: Why “Passing” Doesn’t Always Mean the Same Thing

When a product says it has “passed heavy-metal testing,” that statement often lacks context. The meaning of “passing” depends entirely on which regulatory benchmark is being applied.

California’s Proposition 65 (Prop 65) establishes exposure limits based on long-term risk models, particularly cancer and reproductive toxicity. These limits are expressed as micrograms per day and are designed to reduce lifetime risk across a broad population. Prop 65 is exposure-based—meaning it considers how much of a substance a person might consume daily over time.

USP (United States Pharmacopeia), on the other hand, sets elemental impurity limits primarily for pharmaceuticals and dietary supplements. USP standards are also expressed as daily intake limits, but they are derived within a different regulatory framework and may vary from Prop 65 thresholds.

Both systems rely on toxicological research. Both aim to protect public health. But they are not identical—and that distinction matters.

Two products can both meet compliance requirements while referencing different benchmarks. Without transparency about which standard was used, consumers are left with incomplete information.

At hMAP, we advocate for clear disclosure of the testing method, reporting format, and regulatory framework used to evaluate heavy-metal levels. Transparency does not require alarm. It requires clarity.