Marine products, including fresh fish and shellfish, are increasingly important exports for many developing countries. Aquaculture is developing, expanding and intensifying in almost all regions of the world to meet an increasing global population's demands for aquatic food products. As a driver for both enhanced food security and economic development for many of the world's people, the challenge is to facilitate this growth in trade whilst protecting the health of consumers.

In 2004, through a Joint FAO/IOC/WHO Ad hoc Expert Consultation on Biotoxins in Bivalve Molluscs, scientific advice was provided to the Codex Committee on Fish and Fishery Products (CCFFP) on biotoxins, in conjunction with CCFFP's work on Proposed Draft Standards for Live and Processed Bivalve Molluscs, to:

• Enable the establishment of maximum levels in shellfish for shellfish toxins (including PSP-, DSP-, ASP-, AZP- and NSP-toxins, and YTXs and PTXs),
• Provide guidance on methods of analysis for each toxin group,
• Provide guidance on monitoring of biotoxin-forming phytoplankton and bivalve molluscs (including sampling methodology),
• Provide information on geographical distribution of biotoxin-forming marine phytoplankton.

In addition, an extensive review and risk assessment of different aspects of marine biotoxins (including five shellfish poisoning syndromes, and one fish poisoning syndrome) was completed in 2004.

The toxins included in the Codex Standard for Live and Raw Bivalve Molluscs (Codex Standard 292–2008) are classified into five groups, namely, the saxitoxin (STX), okadaic acid (OA), domoicacid (DA), brevetoxin (BTX) and azaspiracid (AZA) groups. For risk assessment and management, knowledge of the amount of toxin congeners in the shellfish is not sufficient. There is also the need to know the relative toxicity of each of the congeners, so that the total toxicity of the material in the extract can be estimated. This requires the determination of Toxicity Equivalency Factors (TEFs).

The 34th Session of CCFFP requested FAO/WHO to provide scientific advice on TEFs for biotoxins included in the Codex Standard. FAO/WHO set up an Expert Group to provide scientific advice and recommendations on TEFs for biotoxins. The Expert Group developed an approach to be used for the development of TEFs for each group of biotoxins included in the Codex Standard, and in addition considered tetrodotoxin (TTX), due to its emergence in shellfish.

The Joint FAO/WHO Expert Meeting on Toxicity Equivalency Factors for Marine Biotoxins was convened in Rome on 22–24 February 2016. This report summarizes the outcomes of the meeting and identifies the TEFs for each of the six groups of toxins.