Given that natural depuration and cooking are largely ineffective, the first line of defence against phycotoxins endangering human health is the monitoring of toxin levels in seafoods and the implementation of legislation to prevent harvesting and marketing if toxin concen-trations exceed statutory limits.
Monitoring programmes exist on local, regional and national scales in countries where phycotoxins are a problem and these have been reviewed by Fern´andezet al. (2004b). A valuable reference work is that by Andersonet al. (2001), which provides details for over 20 countries of national management plans, monitoring strategies, toxin tolerance limits, cost-benefit analyses, responsible authorities and many more useful facts.
In addition to causing public health problems, toxic phytoplankton can have a signifi-cant effect on the use of coastal waters for mariculture, commercial fisheries and recreation (Premazzi and Volterra, 1993; Andersonet al., 2001). Given the need to minimize economic losses and the potential risk to the public caused by these outbreaks, two monitoring strategies have been used: screening of natural phytoplankton populations for the presence of harmful species and the regular testing of seafoods.
4.13.1 Phytoplankton monitoring
National strategies and methodologies adopted to monitor harmful algae have been reviewed in detail by Andersonet al. (2001), van Egmond et al. (2004) and in part III of Hallegraeff et al. (2004). By itself, phytoplankton monitoring does not provide sufficient protection to public health but it is often used as an early warning system on which to base intensive
sampling programmes of toxicity testing of shellfish (or finfish) tissue in an area where toxic species have been detected.
4.13.2 Monitoring of shellfish tissues for toxicity
When shellfish resources are well developed, intensive monitoring has proven cost-effective and has permitted flexible management so as to optimize the areas of shellfish open to harvesting and minimize economic loss. Tolerance limits for toxins in seafood have been established above which harvesting or marketing is prohibited and this approach is discussed in Fern´andezet al. (2004b), who also list ‘action levels’ for phycotoxins in seafood used in various countries. Table 4.7 illustrates the approach taken by the European Union which has laid down detailed regulations concerning not only the permitted concentrations in seafood but also the methods of bioassay and analysis. There is still disagreement in some countries regarding the prescribed bioassays (Anon., 2005a,b). The EU itself is committed to replacing animal bioassays: ‘Biological methods shall be replaced by alternative detection methods as soon as reference materials for detecting the toxins . . . are readily available, the methods have been validated and this Chapter has been amended accordingly’. (Chapter V of Section VI of Annex III to Regulation (EC) No. 853/2004 – see note in reference section).
4.13.3 Risk analysis
It is never going to be possible to eliminate the possibility of phycotoxins being present in seafood, hence, for example, the EU regulations to minimize the risk to public health and the trend is towards risk analysis based on sound scientific data. An example of rigorous risk analysis is that for azaspiracids carried out by the Food Standards Agency for Ireland (Anon., 2006b).
Lupin (2004) has defined risk analysis as being composed of three elements: risk assess-ment, risk management and risk communication. van Egmondet al. (2004) concluded that risk assessment of phycotoxins has not been carried out in a clear-cut fashion and has become merged to some extent with risk management, thereby complicating the process. They made a number of recommendations, including the suggestion that formal risk assessment should be carried out by international bodies, such as the World Health Organization, and this has subsequently begun to come about.
A working group (WG) of the Codex Committee on Fish and Fishery Products (CCFFP) of the FAO/WHO Codex Alimentarius Commission (Anon., 2006a) was convened to consider the recommendations of an international expert working group (Anon., 2004) and how these might be incorporated into the ‘Draft Standard for Live and Raw Molluscs and the section of the Code on Live and (Raw) Bivalve Molluscs’ of the Codex. Among the guiding principles set for the CCFFP WG were (i) The WG should recommend marine biotoxin levels in a manner consistent with the approach taken for setting levels for other naturally occurring toxicants in Codex Standard (compare this with comments made in Section 4.3) and (ii) that ‘Marine biotoxin standards should not be set where there is a lack of evidence of harm to humans, either from human clinical data, epidemiological studies or animal voluntary feeding studies’ with a footnote that ‘Before regulating, where only intraperitoneal studies exist, these must be complemented by oral studies. Among these, voluntary feeding should take priority over gavage’.
One of the recommendations of the CCFFP WG was that PTXs and YTXs should be deregulated (Table 4.7), based on the marked difference in toxicity when administered orally
Table4.7Permissibleconcentrationsoftoxinsintissueofbivalvemolluscs,echinoderms,tunicatesandmarinegastropodsandmethodsofbioassayoranalysis asprescribedbyEuropeanUnionLegislationin2006. ToxingroupSyndromePrescribedmethodofassayor analysis(1);seealsoTable4.5 Partsof shellfishsoft partstobe analysed Maximum concentrations permittedbyEU legislation Maximum concentrations recommendedby FAO/WHOCAC(3)
RelevantEClegal instruments(see referencesection forwwwURLs) Hydrophilic Saxitoxins (STXs)PSPBioassay:AOACmousebioassay (MBA).Thismaybecarriedoutin association,ifnecessary,withanother methodfordetectingSTXandanyof itsanaloguesforwhichstandardsare available.Iftheresultsarechallenged, thereferencemethodmustbethe biologicalmethod
Entirebodyorany partedible separately
800μgkg−1800μgkg−1Directive91/492/EEC Decision 2002/225/EC(5) Regulation(EC)No. 853/2004(6) Regulation(EC)No. 2074/2005(7) Domoicacid (DA)ASPHPLCmethodoranyotherrecognized method,e.g.ELISA.Iftheresultsare challenged,thereferencemethod mustbeHPLC
Entirebodyorany partedible separately
20mgkg−120mgkg−1Directive97/61/EC(4) Decision 2002/225/EC(5) Regulation(EC)No. 853/2004(6) Regulation(EC)No. 2074/2005(7) Lipophilic Okadaicacid (OA)andDino- physistoxins (DTXs)
DSPBioassay:ThreeMBAsandonerat bioassayareprescribed.Choiceof MBAdependsontheparticular lipophilictoxinsandthesolventsused forextraction. Alternativemethodsmaybeused separatelyorincombination(HPLC withfluorimetricdetection,LC-MS, ELISA,enzymeinhibition(PPA)assay) providedthattheyarenotlesseffective thanthebiologicalmethodsandthat theirimplementationprovidesan equivalentlevelofpublichealth protection(2) Wholebodyor hepatopancreas. Specifiedweights ofthesetobeused insomeMBAs
160μgkg−1of OAequivalents∗160μgkg−1ofOA equivalentsDecision 2002/225/EC(5) Regulation(EC)No. 853/2004(6) Regulation(EC)No. 2074/2005(7)
Azaspiracids (AZAs)AZPBioassaysasforOA/DTX.Alternative methods(above)mustbeableto detectAZA-1,-2and-3 Entirebodytobe usedwhensingle MBAwithacetone extractionused 160μgkg−1of AZAequivalents160μgkg−1–tobe reviewedasmore databecome available
Decision 2002/225/EC(5) Regulation(EC)No. 853/2004(6) Regulation(EC)No. 2074/2005(7) Pectenotoxins (PTXs)DSP?BioassaysasforOAandDTX. Alternativemethods(above)mustbe abletodetectPTX-1and-2
AsforOA/DTXIncludedwithOA equivalents (above∗)intotal Deregulation recommended–see Section4.13.3intext
Decision 2002/225/EC(5) Regulation(EC)No. 853/2004(6) Regulation(EC)No. 2074/2005(7) Yessotoxins (YTXs)BioassaysasforOAandDTX. Alternativemethods(above)mustbe abletodetectYTX,45OHYTX,homo YTXand45OHhomoYTX
AsforOA/DTX1.0mgkg−1YTX equivalentsDeregulation recommended–see Section4.13.3intext
Decision 2002/225/EC(5) Regulation(EC)No. 853/2004(6) Regulation(EC)No. 2074/2005(7) Notes:(1)ECRegulation(EC)No.2074/2005,AnnexIII.(2)Itisstipulated:(a)Ifnewanaloguesofpublichealthsignificancearediscovered,theyshouldbeincludedintheanalysis.(b) Standardsmustbeavailablebeforechemicalanalysisispossible.(c)Totaltoxicityshallbecalculatedusingconversionfactorsbasedonthetoxicitydataavailableforeachtoxin.(d)The performancecharacteristicsofthesemethodsshallbedefinedaftervalidationfollowinganinternationallyagreedprotocol.(3)CodexAlimentariusCommissionoftheUNFood&Agriculture OrganisationandtheWorldHealthOrganisation,JointFoodStandardsProgramme,CodexCommitteeonFishandFisheriesProducts,WorkingGroup–seeAnon.(2006a).(4)Amends AnnextoDirective91/492/EECtoincludedomoicacid.(5)LaysdowndetailedrulesforimplementationofDirective91/492EECasregardsmaximumlevelsofspecifiedbiotoxinsand methodsofanalysis.(6)Laysdownspecifichygienerules.(7)AmendsReg.853/2004:Annex3detailsrequiredtestingmethods–see(1).
as compared to i.p. (see Sections 4.10.1 and 4.10.2) and the application of risk factors, with the proviso that should data become available, the toxicological effects of PTX and YTX to humans would be reassessed.
A full account of the background to the WG and its detailed recommendations can be found in Anon. (2006a). In addition, a useful overview of the work of the FAO, WHO and IOC to provide scientific advice on marine biotoxins has been provided by Toyofuku (2006).