Derivation of toxicity equivalency factors for marine biotoxins associated with Bivalve Molluscs

Toxins in seafood pose an important risk to human health, and maximum permissible levels for these substances have been imposed by regulatory authorities throughout the world. Several groups of toxins are known, each of which contain many analogues of the major toxin, and regulatory limits are set on the basis of the total toxicity of all the analogues within the group. In the past, regulatory limits were set on the basis of the toxicity of an extract of the seafood to mice. This had the advantage of giving an estimate of the total toxicity of the toxins in the sample, but it is now being replaced by instrumental methods of analysis. Such analyses provide accurate quantitation of the toxin analogues in the sample, but because such analogues may have widely dissimilar toxic activities, knowledge of the relative toxicities of the analogues is required for risk assessment. The ratios between the toxicity of the analogues and that of a reference compound within the same toxin group are termed “Toxicity Equivalency Factors” (TEFs). In this document, the requirements for determining TEFs of toxin analogues are de scribed, and requirements for further research are identified. The new analytical methods, together with appropriately-derived TEFs, will provide scientifically-based regulatory limits for seafood toxins, protecting human health without unnecessarily disadvantaging the seafood industry.