Lawrence, J.; Loreal, H.; Toyofuku, H.; Hess, P.; Karunasagar, I.; Ababouch, L.
Assessment and management of biotoxin risks in bivalve molluscs..
FAO Fisheries and Aquaculture Technical Paper No. 551. Rome, FAO. 2011. 337 pp.
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, 26–30 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 organized 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
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;
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
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
• Appendix 1 presents the concepts of marker compounds and relative response
factors (RRFs). In this discussion paper, the definitions, practicality and
limitations in use of marker compounds and RRFs are examined in the context
of analysis for marine biotoxins in shellfish.
• Appendixes 2 and 3 present more detailed considerations about the marine
biotoxin action plan and the role and design of phytoplankton monitoring
in harmful algal bloom (HAB) programmes, from the documents collated by
Working Group 3 of the Expert Consultation in 2004.
Part III illustrates how the Codex Alimentarius handled and used the expert
recommendations for the management of the risk of biotoxins in bivalve molluscs.
Three documents are provided:
• Report of the Working Group on assessing advice from the ad hoc expert
consultation on biotoxins in bivalve molluscs;
• Codex Code of Practice for Processing Live and Raw Bivalve Molluscs;
• Codex Standard for Live and Raw Bivalve Molluscs.