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There is no single WHO-wide permissible limit for every heavy metal in every fish. WHO and FAO scientific advice informs Codex standards and national food-safety rules, but a limit depends on the contaminant, fish category, and jurisdiction. Before comparing a test result with a limit, check the current rule and identify its legal status, analyte, fish category, portion, units, and date.
Does WHO set permissible limits for heavy metals in fish?
WHO supports scientific advice on food and nutrition, including work with FAO that informs Codex and national food-safety standard-setting. National authorities establish the rules that apply in their jurisdictions. Codex values should therefore not automatically be described as binding domestic law or as universal “WHO limits.”
Codex distinguishes maximum levels (MLs) from guideline levels (GLs). These terms are not interchangeable: identify the document and type of value before applying or reporting a number. Codex CXS 193-1995 was listed as modified in 2025, so time-sensitive reporting should be checked against its current consolidated text.
Codex methylmercury values reported in committee documents
Codex committee documents report both broad guideline levels and species-specific maximum levels for methylmercury. The figures below are attributed to the documents that reported them; they should not be treated as a verified, complete statement of the current consolidated standard without checking CXS 193-1995 and any subsequent amendments.
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| Codex source | Fish category | Reported value | How to interpret it |
|---|---|---|---|
| FAO/WHO Codex committee document, 2014 | Fish other than predatory fish | 0.5 mg/kg methylmercury | Reported as a guideline level, not automatically a domestic legal maximum. |
| FAO/WHO Codex committee document, 2014 | Predatory fish | 1 mg/kg methylmercury | Reported as a guideline level, not automatically a domestic legal maximum. |
| FAO/WHO Codex discussion paper, 2021 | Tuna | 1.2 mg/kg methylmercury | The paper described this as a fish-specific maximum level in CXS 193-1995 at that time. |
| FAO/WHO Codex discussion paper, 2021 | Alfonso | 1.5 mg/kg methylmercury | The paper described this as a fish-specific maximum level in CXS 193-1995 at that time. |
| FAO/WHO Codex discussion paper, 2021 | Marlin | 1.7 mg/kg methylmercury | The paper described this as a fish-specific maximum level in CXS 193-1995 at that time. |
| FAO/WHO Codex discussion paper, 2021 | Shark | 1.6 mg/kg methylmercury | The paper described this as a fish-specific maximum level in CXS 193-1995 at that time. |
The 2014 committee document describes the broad guideline levels as applying to fresh or processed fish and fish products in international trade. That scope does not make them automatically binding national legal limits. For a specific product, verify the wording and category in the relevant current standard or law.
Why the authority and fish category matter
A number may come from a Codex guideline, a Codex maximum level, or a national or regional regulation. It may also apply to a particular species, class of fish, or analyzed portion. A comparison is meaningful only when those details match.
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| Comparison detail | What to check |
|---|---|
| Authority and legal status | Is the value a Codex guideline, Codex maximum level, or enforceable national or regional rule? |
| Contaminant | Does the rule cover mercury, lead, cadmium, arsenic, or another element? |
| Chemical form | For mercury, does the value concern methylmercury or total mercury? |
| Fish category | Does the rule cover general fish, predatory fish, or a named species? |
| Product and sample | What fish portion and product state does the rule cover, and how is the sample collected or calculated? |
| Units and date | Are the units aligned, and is the cited instrument current? |
What about lead, cadmium, and arsenic?
The research reviewed for this article does not establish a current, complete Codex table for lead, cadmium, arsenic, and all fish categories. Do not extrapolate a mercury value to another contaminant or turn a limit for one food category into a general finfish limit. Find the applicable current national or regional instrument and confirm that it covers the contaminant, species, portion, and product in question.
National standards are not interchangeable
National and regional rules can differ from Codex values in legal status, fish categories, analyzed portions, and calculation methods. The European Union’s Regulation (EU) 2023/915 and Australia/New Zealand Food Standards Code Schedule 19 are official instruments with fish contaminant provisions. This article does not provide numerical limits from those instruments: consult their current text and match the relevant annex or schedule entry before making a comparison.
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How to check a fish laboratory result
- Identify the jurisdiction. Determine which country or regional market’s law applies. A Codex document is not automatically binding domestic law.
- Find the current instrument. Check the consolidated standard or regulation and its amendment date.
- Confirm the contaminant and form. For mercury, establish whether the report measures methylmercury or total mercury.
- Match the fish category. Check whether the rule covers the named species, predatory fish, or another category.
- Match the sample basis. Confirm the tested portion, product state, units, sampling approach, and any calculation method required by the rule.
- Compare only after those checks. If the result appears above a limit, contact the relevant food-safety authority or a qualified laboratory rather than drawing conclusions from an unmatched value.
Sources and limits of this summary
This summary relies on WHO’s description of standards and scientific advice, FAO/WHO Codex committee documents from 2014 and 2021, the Codex standards index, European Union Regulation (EU) 2023/915, and Australia/New Zealand Food Standards Code Schedule 19. The 2014 and 2021 Codex documents support the figures attributed to them above, but the research reviewed here did not verify the complete current consolidated CXS 193-1995 fish table. Check that text and the applicable national instrument before relying on a current legal limit.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.FAQ
Are Codex limits legally binding in my country?
Not automatically. National authorities establish the rules that apply in their jurisdictions. Check the current national or regional instrument rather than assuming a Codex value has been adopted as law.
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- Versatile Use for Freshwater and Ponds: This aquarium water test kit is versatile and suitable for both freshwater and saltwater environments. It can be used in various aquariums, fish tanks, ponds, pools, and shrimp tanks, making it easy to monitor water quality and ensure your filter functions properly. Experts recommend testing your aquarium water at least twice a week to maintain optimal water quality
- Fast and Accurate Results: Get accurate results in minutes with just 3 steps: 1) Dip the test strip into water for 2 seconds for pads 1-7; dip pad 8 (Ammonia nitrogen) separately for 5 seconds. 2) Remove the strip without shaking off excess water. Hold horizontally for 30 seconds for pads 1-7, wait 180 seconds to read Pad 8 (Ammonia nitrogen). 3) Compare the colors to the chart for up to 99% accuracy and take necessary action
- Extended Shelf Life: The test strips are packaged in a well-sealed bottle to ensure they remain effective over time. This protects the strips from moisture and other environmental factors, ensuring you have reliable testing materials on hand when needed
- Convenient Use: With this kit, you can test your aquarium water at home without the need to send samples to a lab, saving you both time and money. Enjoy peace of mind knowing your aquarium water is balanced and safe without the stress or extra expense. By identifying potential issues, our fish tank testing kit helps prevent hidden water problems and ensures the safety and well-being of your fish
What is the mercury limit for tuna?
A 2021 FAO/WHO Codex discussion paper reported a methylmercury maximum level of 1.2 mg/kg for tuna in CXS 193-1995 at that time. Verify the current consolidated standard and the applicable national rule before treating that figure as current or legally binding.
Do mercury values differ for predatory fish?
A 2014 Codex committee document reported guideline levels of 0.5 mg/kg for fish other than predatory fish and 1 mg/kg for predatory fish. A separate 2021 Codex discussion paper reported species-specific maximum levels for certain fish. Check the current standard and the fish category before comparing a result.
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1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errorsCan I use a mercury value as a limit for lead or cadmium?
No. Each contaminant has its own applicable standards and categories. Find the current rule for the specific contaminant and fish product rather than borrowing a mercury value.
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