1Five markets, two kinds of number

Parts 4 to 7 of this series answered one question per product: which metal is most likely to be over the limit. This part answers a different one. You have a result from the laboratory. Which limit do you compare it with, and does the answer change when you export?

Two systems are in use.

The EU and Great Britain set a concentration. The limit is a number of milligrams of metal per kilogram of product. A single laboratory result can be compared with it directly.

The United States, Canada and the Australian medicines route set a permitted amount per day. The limit is a number of micrograms of metal that a person may take in a day. A laboratory result in mg/kg means nothing against it until the daily dose of the product is known.

Both systems appear in the tables below. Where an instrument uses rows of a table to identify product categories, we give the row number, as in the earlier parts of this series: a "row" is one line of the table of maximum levels in Annex I of Regulation (EU) 2023/915, and each row names a food category and its limit.

The main finding of this article is short:

• No instrument in any of the five markets sets a different metal limit for a multivitamin, a protein powder, a botanical extract or a fish oil. Within a market the legal figures are the same for all four.
• The difference between those products is the daily dose, and the dose decides which market is the strict one. For a tablet the EU and the US figures are close. For a 30 g scoop of protein the US figure is roughly eighteen times tighter than the EU one.
• In the United States the number that constrains lead is not the pharmacopoeial one. It is the California Proposition 65 warning level of 0.5 µg a day.

2The legal figures, side by side

European Union

Regulation (EU) 2023/915 sets these levels for food supplements, in milligrams per kilogram:

• lead: 3.0 (row 3.1.28);
• cadmium: 1.0 (row 3.2.21.1);
• cadmium, for supplements consisting of at least 80 % dried seaweed, seaweed products or dried bivalve molluscs: 3.0 (row 3.2.21.2);
• mercury: 0.10 (row 3.3.2);
• arsenic: no row. Subsection 3.4 covers rice, infant food, juices, fish, shellfish and salt. It has no entry for food supplements.

Article 2(3) of the regulation states that the levels apply to food as placed on the market and to the edible part of the food. For a supplement this means the powder, tablet or oil as sold, not a reconstituted or dry-matter basis. Article 3, which requires drying and processing factors to be taken into account, applies only where no specific level is set for the product. A food supplement has one, so Article 3 does not enter.

Great Britain

Great Britain kept the earlier text, Regulation (EC) 1881/2006, as assimilated law. The supplement figures are the same numbers under different row numbers: lead 3.0 (3.1.22), cadmium 1.0 (3.2.21), cadmium in seaweed and bivalve supplements 3.0 (3.2.22), mercury 0.1 (3.3.3), no arsenic row for supplements. The GB table states its levels on a wet weight basis.

The two texts have diverged elsewhere, and the wording of the seaweed carve-out differs: the EU sets a threshold of 80 %, Great Britain says "exclusively or mainly".

Northern Ireland

Northern Ireland follows the EU figures. The Protocol on Ireland and Northern Ireland lists the EU contaminants framework and provides that a reference to a listed act is to be read as a reference to that act as amended or replaced. The Food Standards Agency has stated that EU changes to contaminant maximum levels are directly applicable in Northern Ireland. We found no official document that names Regulation 2023/915 for Northern Ireland, and the Northern Ireland enforcing regulations still refer to the older text. The conclusion is well supported but rests on that reading rather than on a provision that says so.

United States

There are no federal maximum levels for these metals in dietary supplements. Two other sets of numbers do the work.

USP General Chapter <2232> gives permitted daily exposures in micrograms per day: lead 5, cadmium 5, inorganic arsenic 15, total mercury 15, methylmercury 2. The chapter says a typical serving is analysed and scaled to the maximum daily intake, then compared with the figure.

California Proposition 65 gives warning thresholds, also per day: lead 0.5 (the reproductive level) and 15 (the cancer level), cadmium 4.1, inorganic arsenic 10. There is no listed level for mercury. A product above a Proposition 65 threshold is not banned. It requires a warning.

Canada

Health Canada's Quality of Natural Health Products Guide gives limits per day for an adult: lead 10, cadmium 6, total mercury 20, methylmercury 2, total arsenic 10, or inorganic arsenic 2.1 where the species is determined. The guide is administrative guidance and says so.

A draft revision published in July 2026 would replace these with the pharmacopoeial figures: lead 5, cadmium 5, inorganic arsenic 15, total mercury 15. It is a draft and is not in force. Canada's lead figure is the one most likely to change.

Australia and New Zealand

Australia splits the question by what the product legally is.

If it is a food, Schedule 19 of the Food Standards Code applies. Schedule 19 has rows for named commodities. It has no row for supplements, sports foods, protein powders, herbal extracts or edible oils. A protein powder sold as a food therefore meets no numerical metal limit there.

If it is a listed or registered medicine in tablet or capsule form, Therapeutic Goods Order 101 applies. The Order does not set its own figures for tablets and capsules. It requires the sponsor to meet either USP <2232> or the ICH Q3D guideline, at the sponsor's choice. The Q3D oral figures are lead 5, cadmium 5, arsenic 15 and mercury 30 micrograms a day. Q3D therefore allows twice the mercury that USP does, and the sponsor may choose it.

The Order does set concentrations for one dosage form, the traditional "pill": arsenic 2, cadmium 1, lead 5 and mercury 0.2 parts per million. Those figures do not apply to tablets or capsules.

New Zealand has no numbers. The Dietary Supplements Regulations were amended in December 2024 to state that the joint food standards do not apply to dietary supplements, and the former limits were revoked.

3What a per-day limit becomes on your product

A per-day limit becomes a concentration as soon as the daily dose is fixed. The arithmetic is one division:

implied concentration (mg/kg) = permitted amount per day (µg) ÷ product taken per day (g)

Micrograms per gram and milligrams per kilogram are the same number, so no further conversion is needed.

The four daily amounts below are assumptions chosen to show the arithmetic. They are not taken from any regulation. Use your own label dose.

Every figure in the three middle columns is arithmetic. It is a calculation from a per-day limit and an assumed dose. No authority has set any of those concentrations as a limit. The right-hand column is the only one that is a legal concentration.

The pattern is worth stating plainly. The larger the daily dose, the tighter a per-day limit becomes in concentration terms. A tablet is small, so a per-day limit converts into a large permitted concentration. A scoop of protein is twenty times heavier, so the same per-day limit converts into a concentration twenty times lower.

4Where the markets are not comparable

Nine differences are worth knowing before a table of numbers is used to make a decision.

The unit basis

Concentration against daily dose, as set out above. A product can meet one system and fail the other on the same analytical result.

The legal weight of the number

The EU and GB figures are binding law. USP <2232> is a pharmacopoeial standard with no federal enforcement of its own. Proposition 65 levels are warning thresholds. Health Canada's guide is guidance. Therapeutic Goods Order 101 is binding but delegates its numbers to two other documents. New Zealand has none. Four different kinds of obligation sit in the same table.

Lead in California

The Proposition 65 reproductive level for lead is 0.5 µg a day. That is ten times below the pharmacopoeial figure and twenty times below Canada's. A product can be inside every limit in this article and still require a Proposition 65 warning in California. The consequence is a warning label, not a withdrawal, but the exposure is private litigation rather than an inspector.

Arsenic species

The EU and Great Britain have no supplement row at all. USP and ICH Q3D limit inorganic arsenic. Canada limits total arsenic at 10 µg a day, or inorganic arsenic at 2.1 µg a day where the species is determined. Proposition 65 lists inorganic arsenic compounds. A routine ICP-MS result reports total arsenic and does not by itself answer the inorganic question.

Mercury

The EU and GB set 0.10 mg/kg in the product. USP sets 15 µg a day for total mercury and 2 for methylmercury. Q3D sets 30 µg a day, and an Australian sponsor may choose Q3D over USP. Canada sets 20 and 2. Proposition 65 has no level.

The seaweed carve-out

It exists only in the EU and Great Britain, and the two wordings differ: at least 80 % in the EU, "exclusively or mainly" in Great Britain.

What counts as the product

The EU and GB rows attach to the legal category "food supplement". Canada's limits attach to natural health products, the USP chapter to dietary supplements, and Australia's split depends on whether the item is a food or a therapeutic good. A protein powder falls outside both Australian sets: it is not a Schedule 19 commodity and it is not a tablet, capsule or pill.

Movement

Canada is consulting on a revision that would lower its lead figure from 10 to 5 µg a day. The EU list has 2026 amendments not yet consolidated, which on the published amendment list do not touch the metals section. Schedule 19 has a new compilation pending. Any table of this kind has a date on it, and this one is 9 September 2026.

Body weight

Only Canada and the ICH guideline express the figures per kilogram of body weight as well as per day. The EU, GB and USP figures are single values.

5One table to keep

The working rule is this. Take one laboratory result in mg/kg, put your label dose beside it, and convert once. Then compare that pair of numbers with each market you sell into, and check which of the two systems that market uses before deciding whether the result passes.

How to read the result itself, including the limit of quantification and the measurement uncertainty, is covered in Part 3.