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Assessment and Management of Biotoxin Risks in Bivalve Molluscs

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As a response to the request for information regarding scientific advice on biotoxins in conjunction with the work for developing Standards for live and processed bivalve molluscs, the Food and Agriculture Organisation of the United Nations (FAO) and the World Health Organisation (WHO) have produced a report on the assessment and management of biotoxin risks in bivalve molluscs.

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The present document compiles the scientific information collected by the experts for the Joint FAO/IOC/WHO ad hoc Expert Consultation on biotoxins in bivalve molluscs held in Oslo, Norway, 2630 September 2004 to answer the request of scientific advice expressed by the Codex Committee for Fish and Fishery Products (CCFFP).

In order to satisfy the many requests received by FAO to disseminate the information collected over these years since 2004, the data and information available were edited and updated in 2009.

The document is organised in three main parts that present scientific and technical information necessary for risk assessment, monitoring and surveillance programmes and, in addition, illustrate how the CCFFP used international expertise to advance and finalize international standards for bivalve molluscs.

Part I is introductory and presents general information on the shellfish toxins selected for their involvement in poisoning events or their bioactivity observed in laboratory animals in combination with their repeated occurrence in shellfish, their physicochemical characteristics and their biogenetic, microalgal origins. It also provides data on bivalve mollusc production and trade and poisoning caused by bivalve molluscs. Consideration is given to the complex chemical nature of phycotoxins that results in many difficulties in obtaining sufficient quantities of all analogues and hampers the development and validation of methods for the evaluation of their toxicity and efficient control of limits. These difficulties and their impact on consumer protection and shellfish production are further discussed.

The interactions between risk evaluation and risk management as integral parts of risk analysis are outlined in the last section of Part I. While these general principles make the Codex approach very clear, it must be noted that specific risk analyses are far from trivial, in particular because of the frequent lack of data on toxin analogues, relative toxicities, exposure and epidemiology. This lack in data often makes risk assessments provisional and requires frequent review of the assessment and the management options derived.

Part II compiles the toxin group monographs prepared by the experts for the Expert Consultation and updated in 2009. The toxins were classified into eight groups based on chemical structure: the azaspiracid (AZA) group, brevetoxin (BTX) group, cyclic imines group, domoic acid (DA) group, okadaic Acid (OA) group, pectenotoxin (PTX) group, saxitoxin (STX) group, and yessotoxin (YTX) group. The reason for this was that for enforcement of Codex standards, chemical classification is more appropriate for analytical purposes than classification based on clinical symptoms. Each toxin monograph contains the following subsections:

  • background information;
  • origins and chemical data;
  • biological data;
  • analytical methods;
  • levels and patterns of contamination of bivalve molluscs;
  • dose response analysis and estimation of carcinogenic risk;
  • evaluation;
  • references.

Part II is completed by the summary of the FAO/IOC/WHO Expert Consultation. One of the conclusions of the Expert Consultation is that decisions made on the safety of shellfish can only be based on the direct measurement of toxins in shellfish flesh; however, an integrated shellfish and microalgal monitoring programme is highly recommended to provide expanded management capability and enhanced consumer protection.

The summary of the Expert Consultation also includes the replies to specific questions posed by the Codex Alimentarius and the recommendations to Member States, FAO, WHO and Codex. Three appendixes provide additional scientific information.

Further Reading

You can view the full FAO/WHO report by clicking here.
June 2012