Oyster Risk Profile

The Exposure Assessment and Trade (EAT) Team at the Food Standards Agency (FSA) was commissioned by the UK Office for Sanitary and Phytosanitary Trade Assurance (UKOSPSTA) to produce a risk profile to inform the potential risks associated with importing oysters into the United Kingdom (UK) from any trading partner. This risk profile considered the hazards that may be associated with the import of oysters into the UK that may pose a risk to public health, considering the general population. These occur naturally or through anthropogenic sources, either via introduction of the hazard into the environment and/ or during the processing (including transit and storage) of the commodity. Animal health hazards which do not pose a public health risk were not within the scope. A risk profile was developed with the following sections: hazard identification, hazard characterisation, risk mitigation and management options, legislation and control, UK consumption patterns and, international trade and production. Discussion around uncertainties and knowledge gaps were included, as well as future considerations regarding emerging hazards and a changing environment. This was intended to provide information for auditors and risk managers within the process of market access requests. Hazard identification was performed via a literature review. The seafood risk tool (SRT) for assessing and mitigating chemical and pathogen hazards in the aquaculture supply chain published in February 2022 by Stentiford et al (1), international guidance and standard documents from CODEX, the Food and Agriculture Organisation of the United Nations (FAO) and the World Health Organisation (WHO) were main sources of information. The SRT is a publication identifying hazards associated with all seafood and assessing the impact of hazards affecting the supply chain via a two-step semiquantitative schema to provide scores for severity of harm caused and likelihood of harm occurring, then multiplied to provide the in final impact score (SRT score). Three hazard categories were identified; chemical hazards (CH), defined as from natural or anthropogenic sources which may affect the health or survival of seafood, and humans consuming seafood; animal hazards (AH), defined as those which may affect the growth, performance, survival or quality of seafood; and human hazards (HH), defined as those which may affect the health and survival of human consumers of seafood. The hazard groups are broken down as follows: • Six CH groups with multiple hazards identified for each: heavy metals (CH1), persistent organic chemicals (CH2), radiological contaminants (CH3), natural biotoxins (CH4), veterinary pharmaceuticals and personal care products1 (CH5), allergens (CH6). • Five AH groups with multiple hazards identified for each: viral pathogens (AH1), bacterial pathogens (AH2), protistan pathogens (AH3), metazoan pathogens (AH4), syndromes2 (AH5). • Three HH groups with multiple hazards for each: environmental pathogens (HH1), anthropogenically derived pathogens (HH2), zoonotic pathogens (HH3). The hazard list was refined before hazard characterisation in consideration of the risk profile scope. AH hazards were not included unless also considered under HH. Allergens and physical hazards were also excluded as they do not relate specifically to import, and hence there was no requirement for characterisation. Additionally hazards identified via sources other than the SRT were also included. The refined hazards list was organised into two main categories for hazard characterisation: microbiological hazards and chemical hazards. Some microbiological hazards were removed from the list to be taken forwards for hazard characterisation when it became clear that they were not associated with oysters and/ or were more commonly associated with other routes of transmission. For microbiological hazards, eight bacterial hazard groups, four viral hazards and four parasitic hazards were characterised. For chemical hazards, seven hazard groups were characterised: heavy metals, persistent organic chemicals (POCs), radiological contaminants, veterinary pharmaceuticals and personal care products, microplastics, high production volume (HPV) chemicals and natural biotoxin hazards. Ten marine biotoxin groups were characterised under natural biotoxin hazards. In most cases, the hazards were well-defined in terms of health effects and composition. Where hazards were less well-defined it was due to limited information on severity of illness (high, medium or low severity of illness not assigned in literature), geographical prevalence of the hazard and disease prevalence. Where possible, information from the WHO on disability adjusted life years (DALYs)3 was included to indicate the global prevalence of disease caused by the hazard. This was not possible in all cases, particularly for chemical hazards and for microbiological hazards where a high, medium or low severity had not been assigned in literature. High, medium or low severity was only assigned for microbiological hazards because chemical hazards are not generally considered in terms of severity, but rather disease outcome based on the dose response relationship and toxicological concern. Severity was provided using the qualitative categories for the severity of detriments adopted by the Advisory Committee on the Microbiological Safety of Food (ACMSF) on multidimensional representation of risks (3). Where possible severity assigned by the International Commission on Microbiological Specifications for Foods (ICMSF) was used (4). In cases where this was not possible, DALYs and/ or literature sources have been used to assign severity using the ACMSF’s severity of detriments (3). The severity assigned was for the general population, not for vulnerable individuals with health conditions which may affect their immune response. SRT impact scores were also presented where possible; they were not provided in cases where hazards had been identified using sources other than the SRT. The SRT scores were derived from the SRT article where the tool was applied to a hypothetical aquaculture scenario intending to produce farmed bivalve molluscs in coastal waters of a non-European Union (EU) marine state for live export and raw consumption within the EU. Impact scores were calculated as part of the SRT for the hazards identified within the article as a multiple of “severity of harm” (part one) and “likelihood of occurrence” (part two). Scores for part one and part two were calculated using the schema, considering six phases (early life, grow out, harvest, processing, trade and consumption) and three control states (uncontrolled, control one: where control measures are applied at discrete phases of supply; control two: where the benefit of controls applied at one phase are accrued in subsequent phases of supply). An overall impact score for each control state was derived with a maximum score for each control state of 216. This was for Live Bivalve Molluscs (LBMs). Generally, SRT scores indicated where controls may reduce the impact of hazards and where these controls could have effects to reduce the impact later on in the supply chain. It is recommended that, as a tool to identify the impact of controls on hazards in seafood, the SRT is utilised to consider which hazards and/ controls should be further investigated using the impacts set out within the article to determine which may ensure safety of imports from specific countries of origin where some hazards may be of more concern. Of the 16 individual microbiological hazards characterised, there was limited information on presence of Staphylococcus aureus in oysters because these bacteria are mostly associated with contamination during processing. However, this hazard was still characterised because it could not be ruled out due to potential introduction during the processing of oysters in the supply chain. Furthermore, the POC, veterinary pharmaceutical and personal care products, and HPV chemical groups are potentially extremely large groups of chemicals which could not all be fully characterised. It should be borne in mind that these groups may continue to expand and that information around the toxicity and prevalence of the chemicals within them is likely to be dynamic and could become quickly out of date. Finally, of the marine biotoxins discussed, yessotoxin, pectenotoxin and cyclic imines were not well-defined in humans. Risk mitigation and management options have been presented (at the time of publication) via the summarisation and comparison of the SRT recommendations, the FAO Technical Guidance for the Development of the Growing Area Aspects of Bivalve Molluscs’ Sanitation Programmes and CODEX standards associated directly with LBMs, hygiene and chemical hazards. The FAO and CODEX guidance reviewed were also noted within the SRT in a Risk Mitigation Matrix (RMM) 4 applied to the LBM scenario, and EU legislation is also quoted and considered in line with this guidance. It is clear that guidance takes into account identified hazards and also the role that the physiology of LBMs takes in the presence of potential hazards. This is important to note because LBMs, and more specifically oysters, obtain food by filter feeding and so are bioaccumulators of diverse hazards from aquatic environments. Therefore, risk mitigation measures are aimed at various areas of the production process to prevent bioaccumulation where possible. This means that while there may be unknown emerging hazards or that some hazards are difficult to monitor, there are multiple steps where risks to the consumer may be mitigated by aiming to generally prevent the accumulation of chemical and microbiological hazards. Guidance for early stages of the supply chain is comprehensively provided mostly via the FAO Technical Guidance for the Development of the Growing Area Aspects of Bivalve Molluscs’ Sanitation Programmes. Additional guidance and standards set out for the latter parts of the supply chain were predominantly via CODEX standards. The conclusions drawn from the interpretation of the SRT analysis suggest that measures applied early in the supply chain, i.e., at the point of growing area selection and management, may reduce the risk in the latter phases. Therefore, in many cases, this reduces the requirement for additional control measures outside of the general hygiene measures set out in CODEX guidance. There are, however, options for when the growing area is under a classification that is not ideal for risk mitigation, such as relaying (movement to a different site) and depuration (decontamination via purging). However, the limitations of these methods should be considered, for example, depuration will not remove biotoxins. Given that EU legislation is in line with the FAO and CODEX guidance, as discussed via the SRT, UK law is also in line with this due to the current status of Retained EU Law (REUL). The guidance set out here has been used to create a proposed checklist for auditors in appendix 14.7. This is not an exhaustive list of all points to be considered by UK auditors and is not intended to replace any current checklists or programs used by UK auditors. It is intended as an additional information point to aid the efficiency of auditing when considering oysters specifically. GB import legislation has been summarised at the time of publication to illustrate controls around the import of LBMs, specifically oysters, this is currently in line with that of the EU due to REUL. Relevant domestic legislation in force at time of publication, on oyster production is also presented to demonstrate the compliance of GB with the international guidance and standards set out under risk mitigation and management options. Furthermore, international legislation, reviewed at the time of publication, is summarised for comparison with international guidance and standards, and GB legislation. It was not possible to summarise the legislation for all countries globally, therefore specific countries or states were selected based on their contributions to international guidance, noted production of oysters, presence as large world powers and available information. These countries and states include the EU, Australia, New Zealand, United States of America (USA), Canada, China and Japan. Legislation was comparable in all circumstances (except for China where information was more limited); however, it was self-reported and therefore difficult to determine exactly to what extent countries follow international guidance and standards. It is recommended that the legislation for countries seeking to import into the UK is reviewed to ascertain if it is comparable to the best practice established within FAO and CODEX guidance and standards. For UK consumption patterns, the National Diet and Nutrition Survey (NDNS) and Diet and Nutrition Survey for Infants and Young Children (DNSIYC) indicated that oysters were rarely eaten by the general population, which was supported by the FSA Food and You survey (5, 6, 7, 8, 9). Therefore, it was difficult to determine the demographic of those who may be higher consumers, how often they may eat them and what their portion sizes may be. Evidence taken from the FSA Food and You survey indicated that oysters were most commonly eaten raw and by groups in higher socio-economic classes. In regard to trade and production of oysters, generally, there are two main types of oysters used in aquaculture – the Pacific cupped oyster (Crassostrea gigas – also known more recently as Magallana gigas) and the European flat oyster (Ostrea edulis). However, there are up to 14 key species of farmed oysters. The UK generally produces the Pacific cupped oyster, at approximately 1.2 million kg per year and exports approximately 1.6 million kg per year. A percentage of UK exports include oysters landed abroad, hence the difference in production vs. export. The UK imports approximately 350,000 kg of oysters per year and where they are imported, they are more commonly processed (prepared or preserved; smoked; frozen), however there were significant imports of live oysters. The main exporters of oysters to the UK were (in the order of weight of import) the Republic of Korea, France and New Zealand between 2016 and 2022. Globally, France, China, Republic of Korea, Ireland and Canada were the highest exporters of oysters between 2016 and 2022 (in order of weight of export). Notable uncertainties associated with the UK consumption and trade data were considered. It was not possible to find comprehensive data on consumption of oysters in the UK and the specific types of oysters traded. This was not considered to detrimentally impact the risk profile as it was possible to determine that oysters were more commonly consumed raw and not as a common occurrence by the general public, and which countries were the highest producers and exporters of oysters globally. Additionally, the highest exporters to the UK were ascertained. Other notable uncertainties were those associated with legislation in other countries following international guidance and standards, it is recommended that this is investigated for specific market access requests. Furthermore, there were some uncertainties associated with hazard identification and hazard characterisation such as limited information. This is considered to be of low concern given the literature consulted and GB import controls in place, including audits for third countries. Finally, uncertainties around future considerations were key as it is clear that factors such as vulnerable population changes, emergence of hazards, climate change, globalisation of the seafood market and changing human behaviours will have an impact on risk associated with oysters, but not how this may occur and what hazards may emerge. Knowledge gaps were identified amongst the noted uncertainties. These were not considered to impact the risk profile significantly because data were generally available, and it was possible to summarise key risks and mitigation measures within the scope of the profile. However, factors noted under future considerations should continue to be reviewed through risk analysis work. Furthermore, these were not identified with a view to pose suggestions for additional research as this is not considered within the scope of the risk profile. Overall, it is clear that oysters are a high-risk product for import, particularly for certain population groups, given their physiology (i.e., filter feeding which allows the bioaccumulation of hazards) and likelihood for raw consumption, but that measures are available to mitigate risks in many cases. Risk mitigation is, however, variable, depending on the hazard of concern. Notably, there are a number of emerging chemical hazards which are less well-defined and/ or may comprise a vast hazard group which is not fully characterised and continues to expand (microplastics, POCs, veterinary pharmaceuticals and personal care products, HPV chemicals, radionuclides). Furthermore, marine biotoxin hazards cannot be controlled after accumulation within the commodity except for the removal of the commodity from the supply chain because purification techniques will not reduce their presence. Mitigation measures must be in place very early on during the supply chain, i.e., at the stage of selecting and monitoring growing areas. Information on future considerations regarding hazards associated with oysters was reviewed, including vulnerable population changes, emerging hazards, climate change and globalisation of the seafood trade. These could have a significant effect on the types and prevalence of hazards observed in oysters, but also their potential effects on the population. It is not intended to provide a comprehensive list but to summarise potential factors which may affect the hazards identified within the risk profile, and also emerging hazards. It is also not intended to predict the effects of these factors but to illustrate the necessity for continued review. It is difficult to predict future events and also to incorporate a large amount of related literature. There are likely to be knowledge gaps in these areas given they are emerging issues. However, many of the standards and guidance discussed in this risk profile are aimed at identifying changes in currently identified hazards and monitoring them, they are also owned by international organisations which monitor emerging risks and update the documents. It is recommended that these areas are monitored by risk assessors and risk managers for emerging risks, including emerging hazards, an increase in the vulnerable population and effects of climate change and globalisation on the seafood trade, as well as changes in human behaviour. Also, that the guidance and standards provided are reviewed to ensure that updates are considered. The final conclusions of this risk profile, in the context of importing into the UK were that where market access requests are made, measures in place in the country of origin should be investigated, with reference to the international guidance and standards and relevant domestic import legislation set out in the risk profile, to estimate the relative safety of the product from that specific country. Furthermore, if these initial investigations do not provide clarity, or indicate a concern, it is recommended that a full country audit and/ or full import risk assessment be considered to gather further information and/ or estimate the risk associated specifically with oysters from the country of origin in order to ensure safety of imports into the UK.