There is no single limit for heavy metals in herbs. The limit depends on the country you sell in and on whether the herb is sold as a food, a herbal tea, a food supplement or a medicine.
So the right question is not "what is the limit" but "which rule applies to my product". Once you know that, the numbers are published and you can write them into your spec.
Who sets the limits
- EU: the EU contaminants regulation sets maximum levels for lead, cadmium and mercury in certain foods, including some spices and food supplements. Check the current text on the European Commission's food safety pages.
- EU and UK medicines: the European Pharmacopoeia and the British Pharmacopoeia set heavy metal requirements for herbal drugs used in medicines.
- US: the FDA has no single federal limit for metals in most herbs and supplements. Many brands use USP chapters on elemental contaminants as a benchmark.
- California: Proposition 65 requires warnings above set daily exposure levels for lead and other listed chemicals, which drives many US buyers' specs.
- Other markets: Gulf countries, Australia, Canada and others have their own food and therapeutic goods rules. Codex and WHO guidance are often used as reference points.
- Your customer: retailers and supplement brands often set tighter internal limits than the law.
Why the numbers differ
Food limits are set per kg of the food as eaten. Supplement and medicine limits are often worked out from a daily dose. A herb taken in small capsules may be allowed a higher concentration than a herb eaten in larger amounts, or the reverse, depending on how the rule is written.
Some rules set limits on total arsenic. Others focus on inorganic arsenic, the more toxic form. Rice and seaweed rules are a common example of the second kind. Make sure your test reports the same form your rule uses.
Limits also change. The EU has revised its contaminant levels several times, and US states have moved on lead in foods. Check the current rule each year rather than relying on an old spec.
How to turn the rule into a spec
Start with the rule for your market and product category. Then check your customer's requirement and take the tighter of the two. Write each metal as a maximum in mg/kg, with the test method and the basis stated.
Ask the supplier for heavy metal results from their last several lots of the same herb. If their typical results sit close to your limit, there is little room for crop variation. That supplier may pass some lots and fail others.
Roots, barks and powders usually carry more risk than clean leaf, because soil clings to them. Our guide on how heavy metals are tested explains why acid-insoluble ash is worth adding to the same spec.
Mistakes to avoid
- Accepting "complies with WHO limits" on a certificate without knowing which limit is meant.
- Using a food limit for a product you sell as a supplement, or the reverse.
- Relying on a test from the supplier's own lab with no accreditation for metals.
- Forgetting that a blend inherits the risk of its worst ingredient.
Where we come in
We help you pin down the limits your market and customer require, write them into the spec, and screen suppliers on their past results before you sample. Each lot can then be tested at an NABL-accredited lab before it ships. Start with a free sourcing review.