Heavy metal limits in botanical ingredients: analytical data

The gap often comes down to how a limit is expressed: USP <2232> sets permitted daily exposures for dietary supplements, while EU contaminant rules establish maximum levels for specified food categories. Neither framework creates one universal parts-per-million threshold for every botanical raw material.

For manufacturers, the practical question is how a test result translates into the intended product, daily intake and destination market. That calculation becomes more demanding when processing concentrates or dilutes naturally occurring contaminants, or when a regulation does not list a specific maximum for the ingredient matrix. A certificate of analysis is a starting point; it is not, by itself, a compliance determination.

USP <2232>: daily exposure, not a universal raw-material limit

USP General Chapter <2232> expresses elemental contaminant limits for dietary supplements as Permitted Daily Exposure (PDE), in micrograms per day. The limits are:

These figures describe an exposure budget, not a stand-alone concentration limit for a drum of extract. To assess an ingredient against a PDE, the manufacturer has to connect concentration with the amount consumed each day. If a supplement contains several ingredient components, their contributions also need to be considered against the finished-product exposure.

USP provides individual component limits based on an assumed daily intake of 10 g: 0.5 µg/g for lead, 0.5 µg/g for cadmium, 1.5 µg/g for inorganic arsenic and 1.5 µg/g for total mercury. Those concentration figures follow from the stated intake assumption. They should not be transferred unchanged to a product with a different daily serving or used as a universal specification for all botanical materials.

The distinction matters in supplier qualification. A buyer comparing two extracts by ppm alone may miss the effect of different recommended serving sizes, extract ratios or inclusion rates. Conversely, a raw material that passes an internal limit may contribute too much of an element when combined with other components in the finished formulation.

A PDE is an exposure limit. Turning it into a raw-material specification requires the intended daily intake and the ingredient’s contribution to the finished product.

Commercial botanical CoAs commonly use release benchmarks of lead ≤2.0 ppm, cadmium ≤1.0 ppm, mercury ≤0.1 ppm and arsenic ≤1.5 ppm. These are useful screening values in trade, but they are not a harmonized global legal standard. They should not be represented as such, and they do not replace the manufacturer’s product-specific assessment.

The arsenic comparison also requires care. The USP PDE in the table applies to inorganic arsenic, while a routine laboratory result may report total arsenic unless speciation has been requested. A total result alone does not establish the inorganic fraction. The specification and test report therefore need to identify what was measured, particularly when the risk assessment depends on the inorganic arsenic threshold.

EU Regulation 2023/915: the matrix and processing history matter

Commission Regulation (EU) 2023/915 establishes legally binding maximum contaminant levels for food and food supplements and replaced Regulation (EC) No 1881/2006. The regulation’s limits apply to specified product categories and contaminants; they should not be treated as a single numerical table that covers every raw botanical extract in the same way.

For an ingredient buyer, the first task is to identify the relevant legal product category and the form in which the material will be placed on the market or used. A dried plant, a processed extract and a compound botanical ingredient can have different processing histories and concentrations. The assessment must follow the applicable category and account for those differences.

Article 3 and Article 20 are particularly relevant where processed, dried or compound botanical ingredients do not have an individual maximum level specified. Food business operators must be able to provide experimental processing, concentration or dilution factors to establish compliance. That shifts the file beyond a supplier’s final ppm result: the operator may need records showing how the material changed during manufacture and how the relevant contaminant level should be interpreted in the resulting product.

EU rules also prohibit using non-compliant raw materials or chemically detoxifying ingredients to bring them within regulatory thresholds. A corrective action that alters the contaminant burden chemically cannot be treated as a route to compliance. Procurement controls, suitable sourcing, process documentation and rejection of non-compliant lots therefore carry more weight than post hoc remediation.

A practical EU assessment should connect four records:

• the raw-material identity and its processing state;
• the analytical result, including the element and species measured where relevant;
• the processing or concentration factor used to interpret the result;
• the intended food or supplement category and its applicable maximum level.

If one of these pieces is missing, the operator may have a result without a defensible compliance position. That weakness can surface during customer qualification, regulatory review or an investigation of a finished product.

Translating concentration into product exposure

A concentration result in ppm is generally expressed as a mass fraction, but the regulatory question may be framed as daily exposure or as a maximum level for a product category. The conversion depends on the amount of ingredient in the daily serving and the product’s processing history.

For a supplement assessed against a PDE, the basic relationship is:

daily contribution = contaminant concentration in the ingredient × ingredient intake per day

Units must be consistent. For example, a result in µg/g multiplied by a daily ingredient intake in grams gives the contaminant contribution in µg/day. The calculation should use the actual or maximum intended daily use, not a convenient default that understates exposure.

For an extract, the raw botanical and finished ingredient can differ substantially in concentration because extraction removes or concentrates portions of the original matrix. A supplier’s extraction ratio may help describe the process, but it does not by itself establish the contaminant concentration factor. Where the EU framework requires experimental factors, the supporting evidence needs to reflect the actual processing operation and material.

The formulation also affects the assessment. If several botanical ingredients contribute the same contaminant, the total daily exposure is the sum of their contributions. A specification designed for each ingredient in isolation can therefore be inadequate for the finished supplement. Manufacturers should link raw-material limits to the formulation’s daily serving and retain the calculation with the product’s compliance documentation.

This is where apparently tidy supplier benchmarks can create false reassurance. A Pb result below a commercial CoA target does not automatically prove that a finished product meets a PDE under every use scenario. Equally, exceeding a buyer’s internal release target does not, on its own, establish that a legal maximum has been exceeded. The relevant limit, product category and intake basis have to be stated before the result can be interpreted.

Analytical verification: method, sample and reporting

USP <233> describes elemental contaminant testing based on microwave-assisted closed-vessel acid digestion followed by ICP-MS or ICP-OES. The digestion step prepares the sample for instrumental analysis; the instrument then measures elemental concentrations. For botanical matrices, the method and sample preparation should be appropriate to the material, since pigments, oils, fibres and extraction residues can affect how a sample behaves during digestion and measurement.

ICP-MS is commonly used for low-level elemental analysis, while ICP-OES is also identified in the USP chapter as an analytical option. The choice should follow the required reporting limits, target elements, sample matrix and laboratory method validation. A certificate that names an instrument but omits the test basis, units or analytical scope leaves the buyer with less usable evidence than the label suggests.

When reviewing a result, manufacturers should establish:

• whether the sample represents the delivered lot and how it was taken;
• whether the report gives results on an as-received, dry-weight or other basis;
• whether arsenic is reported as total arsenic or inorganic arsenic;
• whether mercury reporting distinguishes total mercury from methylmercury where the assessment requires it;
• whether the method’s reporting limit is low enough to assess the applicable specification;
• whether the laboratory’s method covers the ingredient matrix and the requested elements.

Sampling deserves particular attention. Botanical lots can vary by plant part, origin, harvest conditions and processing, and a precise instrument result cannot correct an unrepresentative sample. Manufacturers should define lot sampling and retesting rules in the supplier quality agreement, then preserve the link between the sample identity, lot number, CoA and production records.

The test result should also retain its context through procurement and formulation. If a supplier changes the extraction process, source material or manufacturing site, prior analytical data may no longer describe the incoming ingredient. Change notification and traceability provisions are therefore part of heavy-metal control, not administrative extras.

Nickel limits: implementation dates require category-level review

Commission Regulation (EU) 2024/1987 introduces maximum levels for nickel in food items. Enforcement begins on 1 July 2025 for relevant categories, with an extended date of 1 July 2026 for specified complex cereal products. Those dates do not create a single nickel limit for all botanical ingredients. Applicability depends on the product category covered by the regulation.

For botanical suppliers and manufacturers, the near-term task is to map affected products and materials to the regulation’s categories, then determine whether the ingredient is tested directly, assessed as part of a compound product or controlled through finished-product testing. A broad statement that a botanical ingredient is “EU compliant” is not enough if the relevant nickel category and implementation date are unclear.

The change also has a supply-chain dimension. If nickel testing is added to incoming controls, laboratories need a suitable method and reporting scope, suppliers need to provide lot-specific data where required, and product teams need enough lead time to resolve failures before production. Procurement should confirm whether existing specifications cover nickel and whether supplier agreements require advance notice of results that exceed the applicable limit.

What manufacturers should do now

Build the compliance assessment around the product’s market and use conditions rather than adopting one ppm table for all botanical inputs. For each ingredient, identify the relevant framework, intended daily intake, product category and processing factors. Keep USP PDE calculations separate from EU maximum-level assessments, because the underlying units and legal logic differ.

Then align supplier documentation with the decision the manufacturer needs to make. A workable file includes a representative lot CoA, a method and reporting basis, processing information, traceability to the delivered batch and a documented calculation where exposure or concentration factors are relevant. For EU materials without a specific individual maximum, obtain the experimental processing, concentration or dilution evidence needed to support the operator’s assessment.

Finally, review nickel applicability against the 2025 and 2026 dates and update raw-material specifications, laboratory scopes and supplier change controls where needed. The operational risk sits in the handoff between a supplier’s analytical result and the manufacturer’s legal conclusion. Close that gap before the ingredient is released to production.