Heavy metals, pesticides, and solvents: the tests that decide clearance

Why botanicals carry more contaminant risk

Botanical raw materials are agricultural products. They are grown in soil, dried outdoors or in sheds, and concentrated into a powder. That concentration step also concentrates any heavy metals or pesticide residues present in the herb, which is why an extract can fail a limit that the raw herb would have passed.

The risk profile differs by plant part and origin. Roots and rhizomes pick up soil-borne metals; leafy herbs carry more pesticide exposure; gums and resins have different microbial profiles. A generic contaminant panel is a starting point, not a finished specification.

Heavy metals

Test lead, arsenic, cadmium, and mercury individually by ICP-MS. A combined "heavy metals" result is less useful because the individual elements have different limits and different toxicological significance.

Limits depend on the destination and the product category. Many supplement buyers apply lead at 1–3 ppm, cadmium around 1 ppm, arsenic at 1–2 ppm, and mercury at 0.1 ppm, but the legal limit for your market and product form takes precedence. Write the agreed limits into the specification and test against them batch by batch.

Pesticide residues

A multi-residue panel of several hundred compounds is standard for exports to the EU and is increasingly requested elsewhere. The panel should be appropriate to the herb: some botanicals are prone to specific actives that a generic panel may miss.

Ask for the panel size, the reporting limit, and whether the laboratory is accredited for the method. A report that says "none detected" without a reporting limit cannot be compared with a regulatory maximum residue level.

Residual solvents

The extraction solvent determines the solvent risk. Ethanol and water are low-risk; hexane, ethyl acetate, and methanol require tighter controls. The COA should test the solvents the process could actually leave behind, against the limits in the destination market or the applicable ICH guidance.

Carriers matter too. If the extract is spray-dried on maltodextrin, the carrier is part of the specification and should be declared, not inferred from the assay difference.

Microbiology and emerging tests

Total plate count, yeast and mold, E. coli, and Salmonella are the baseline. Some buyers add Staphylococcus aureus and Listeria depending on the matrix and the market.

Two tests are increasingly requested for botanicals: ethylene oxide, after high-profile recalls in the EU, and pyrrolizidine alkaloids for herbs that can be contaminated with those plants. Neither belongs on every specification, but both belong in the conversation for the relevant botanicals and destinations.

How to verify rather than trust

Use a laboratory accredited to ISO/IEC 17025 for the method, and ask for the report to name the batch. Third-party verification of a supplier's own COA is a reasonable first-order cost, especially for a new supplier or a high-value botanical.

Keep a retained sample from each lot. If a customer audit or a stability failure raises a question later, the retained sample is the only way to reconstruct what actually shipped.

• Is the laboratory accredited for the specific method?
• Does the report reference the lot number?
• Are reporting limits stated for pesticide and solvent results?
• Is a retained sample kept, and for how long?