Quick answer
Heavy metal limits are mostly set as a maximum daily intake in micrograms, not a concentration. ICH Q3D gives drug products an oral PDE of 5 µg/day for lead, California's Prop 65 sets a 0.5 µg/day lead level that triggers a warning, and FDA uses interim reference levels and baby-food action levels for lead in food.
What are the heavy metal limits for lead, cadmium, arsenic and mercury?
Most heavy metal limits are written as a maximum amount taken in per day, in micrograms (µg/day). The table puts the drug-product limits from ICH Q3D next to California's Proposition 65 safe harbor levels for the same four elements.
Daily limits in µg/day. Sources: ICH Q3D(R2) Table A.2.1 (oral PDE); OEHHA safe harbor list and Title 27, California Code of Regulations, sections 25705, 25709 and 25805 (Prop 65).
| Element | ICH Q3D(R2) oral PDE, drug products | Prop 65 NSRL (cancer) | Prop 65 MADL (reproductive harm) |
|---|---|---|---|
| Lead | 5 | 15 (oral) | 0.5 |
| Cadmium | 5 | 0.05 (inhalation) | 4.1 (oral) |
| Arsenic | 15 (assessment based on inorganic arsenic) | Inorganic arsenic compounds: 10 (except inhalation); 0.06 (inhalation) | None established |
| Mercury | 30 (inorganic mercury; does not apply to organic mercury) | None established | None established |
Figures checked against the sources below on 3 November 2026; rules change, so confirm the current version before relying on them.
USP <2232> (dietary supplements) and USP <232> (drugs): the numeric tables in these chapters sit in the subscription USP-NF. Check the current chapter before quoting a figure.
What does ICH Q3D allow in drug products, and how does USP 232 relate?
ICH Q3D(R2), adopted on 26 April 2022, sets permitted daily exposures (PDEs) for elemental impurities in new drug products, by route of administration. Lead, cadmium, arsenic and mercury are Class 1, the elements a Q3D risk assessment considers for every route. For products taken at 10 grams a day or less, Option 1 converts each PDE into a single concentration that every component can meet.
ICH Q3D(R2) Class 1 elements. PDEs from Table A.2.1 (µg/day); Option 1 concentrations from Table A.2.2 (µg/g, daily dose of not more than 10 g).
| Element | Oral PDE (µg/day) | Parenteral PDE (µg/day) | Inhalation PDE (µg/day) | Option 1 oral concentration (µg/g) |
|---|---|---|---|---|
| Cadmium | 5 | 2 | 3 | 0.5 |
| Lead | 5 | 5 | 5 | 0.5 |
| Arsenic | 15 | 15 | 2 | 1.5 |
| Mercury | 30 | 3 | 1 | 3 |
Figures checked against the sources below on 3 November 2026; rules change, so confirm the current version before relying on them.
Q3D covers new drug products (it also excludes herbal medicinal products), so it is not a supplement rule. FDA's 2018 guidance on elemental impurities says USP worked with ICH to align <232> with Q3D, that the aligned <232> became official on 1 August 2017, and that <232> and <233> replaced the old <231> Heavy Metals test. Since 1 January 2018, General Notices 5.60.30 has applied <232> to all drug products with USP monographs, except those it excludes. USP <233> holds the test procedures.
What are Prop 65 safe harbor levels, and do they ban a product?
California's Proposition 65 uses two kinds of safe harbor level, both in µg/day:
- NSRL (No Significant Risk Level): for chemicals listed as causing cancer. It is set at the exposure calculated to cause one excess case of cancer in 100,000 people over a lifetime.
- MADL (Maximum Allowable Dose Level): for chemicals listed as causing reproductive harm. Exposure at 1,000 times the MADL is expected to have no observable effect.
Prop 65 levels trigger warnings, not bans. A product can still be sold in California above a safe harbor level, but the business must give a clear and reasonable warning unless it can show the exposure is at or below the level. For lead, the 0.5 µg/day MADL is the number most products have to meet, since it is far lower than the 15 µg/day NSRL.
Two gaps matter. Arsenic's level covers inorganic arsenic, so a total arsenic result is a conservative stand-in. Mercury and methylmercury are on the Prop 65 list, but no NSRL or MADL appears in the safe harbor table, so a business must justify an exposure level some other way or warn. See Prop 65 testing for how warnings and exposure assessments work.
What limits has FDA set for lead in food?
FDA uses two different tools for lead in food. Interim reference levels (IRLs) are benchmarks for daily lead intake from food: 2.2 µg/day for children and 8.8 µg/day for females of childbearing age. They are not limits for a single product. Action levels are concentrations at which FDA may regard a food as adulterated. Under its Closer to Zero work, FDA issued final action levels for processed food intended for babies and young children (under two years old) in January 2025:
FDA action levels for lead in processed food intended for babies and young children. Source: FDA Guidance for Industry, January 2025.
| Food category | Lead action level |
|---|---|
| Fruits, vegetables (excluding single-ingredient root vegetables), mixtures (including grain- and meat-based mixtures), yogurts, custards/puddings, single-ingredient meats | 10 ppb |
| Single-ingredient root vegetables | 20 ppb |
| Dry infant cereals | 20 ppb |
Figures checked against the sources below on 3 November 2026; rules change, so confirm the current version before relying on them.
An action level is a concentration in the food (ppb), so it is compared directly with the CoA result, with no serving-size math. FDA guidance is not legally binding, but FDA says it will consider these levels when deciding on enforcement.
How do you convert a CoA result in ppm to µg/day?
A CoA reports a concentration. One ppm is one microgram per gram (µg/g), so:
µg/day = result (ppm) × grams per serving × servings per day
Worked example with made-up numbers: a botanical capsule with 0.75 g of fill, 2 capsules per serving, up to 2 servings per day on the label. That is 0.75 × 2 × 2 = 3.0 g of product per day.
Worked example (made-up results). Daily intake = ppm × 3.0 g/day, compared with the Prop 65 levels in the first table.
| Element | CoA result (ppm) | Daily intake (µg/day) | Prop 65 level (µg/day) | Under the level? |
|---|---|---|---|---|
| Lead | 0.15 | 0.45 | 0.5 (MADL) | Yes, at 90% of it |
| Cadmium | 0.30 | 0.90 | 4.1 (MADL, oral) | Yes |
| Arsenic (total) | 0.40 | 1.2 | 10 (NSRL, inorganic, except inhalation) | Yes, even if all of it were inorganic |
| Mercury (total) | 0.02 | 0.06 | None established | No Prop 65 safe harbor level to compare |
To work backward, divide the daily limit by the grams per day: 0.5 ÷ 3.0 gives a maximum of about 0.17 ppm lead for this product. If the label allowed 3 servings (4.5 g per day), the same 0.15 ppm result would give 0.675 µg/day, above the lead MADL. Prop 65 exposure is calculated for the average user of the product, so the label maximum is the conservative case.
Why can a product pass one limit and fail another?
The limits answer different questions. ICH Q3D sets what a drug product may contain, with Option 1 built on a 10 g daily dose: 0.5 µg/g of lead × 10 g gives the 5 µg/day PDE. Prop 65 sets when a warning is needed in California, and its lead MADL is one tenth of the Q3D oral PDE. FDA action levels are concentrations for specific baby foods, and FDA IRLs describe total intake from the whole diet.
So a capsule at 0.3 ppm lead taken at 3 g a day (0.9 µg/day) sits well under the Q3D oral PDE but above the Prop 65 MADL. The same ppm in a 1 g daily serving (0.3 µg/day) is under both. Serving size, not only concentration, decides the outcome.
How do you use these limits with your Certificate of Analysis?
- Decide which rules apply: drug or supplement, sold in California or not, intended for babies or not, and any buyer specification.
- Put the serving size and the maximum servings per day from the label next to each ppm result.
- Check that the limit of quantitation is low enough. At 10 g a day, a 0.5 µg/day limit equals 0.05 ppm, so the method has to report below that.
- For arsenic and mercury, see whether the result is total or speciated, and whether your limit is for inorganic arsenic or methylmercury.
When you send a sample to Verified Analytical Laboratory for heavy metals testing, include the serving size and servings per day so VAL can report per-serving results on the CoA. We confirm the method and sample amount with your quote. For reading each field of the report, see how to read a CoA.
Questions about this page
What is the Prop 65 limit for lead in a supplement?
What is the ICH Q3D limit for lead?
Does Prop 65 have a safe harbor level for mercury?
Do USP 2232 limits apply to every dietary supplement?
Are FDA interim reference levels a limit for my product?
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