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Seafood Safety 1 Executive Summary Overview Fish and shellfish are nutritious foods that constitute desirable components of a healthy diet. Most seafoods available to the U.S. public are wholesome and unlikely to cause illness in the consumer. Nevertheless, there are areas of risk. The major risk of acute disease is associated with the consumption of raw shellfish, particularly bivalve molluscs. For persons living in areas in which reef fish are consumed (Hawaii, Puerto Rico, the Virgin Islands), there is a risk of ciguatera; other natural toxins (paralytic shellfish poisoning, neurotoxic shellfish poisoning, etc.) have been associated with shellfish from endemic areas. Finally, there are less well-defined risks of acute and chronic disease related to environmental contamination of aquatic food animals. Dealing with such risks on a short-term basis requires improvements in the present system of regulatory control. In the long term, amelioration and eventual elimination of some hazards require strengthening and more effective application of control measures to prevent the disposal of human and industrial waste into offshore marine and fresh waters. Because of the strong public interest in seafood safety and the declared intention at the congressional level to develop a new inspection system, a clear opportunity exists to introduce innovative methodologies for control that address directly the important health issues associated with seafood consumption. This report reviews the nature and extent of public health risks associated with seafood, and examines the scope and adequacy of current seafood safety programs. The conclusions and recommendations arrived at are summarized in the following material: Most current health risks associated with seafood safety originate in the environment and should be dealt with by control of harvest or at the point of capture. With minor exceptions, risks cannot be identified by an organoleptic inspection system. Inspection at the processing level is important to maintain safety of seafoods, but there is little evidence that increased inspection activities at this level would effectively reduce the incidence of seafood-borne disease. With currently available data, it is possible to identify the source of much of the acute illness associated with seafood consumption, though the dimensions of the
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Seafood Safety problems are not always known; these data, in turn, can form the basis for national control programs. Chronic illness resulting from seafood consumption is associated primarily with environmental contamination; thus, control depends on improved understanding of the occurrence and distribution of the chemical agents involved, the exclusion of contaminated seafood from the market, and increased action to prevent additional pollution of the waters. Because well over half the nation's seafood supply is imported and environmental contamination is globally pervasive, it is important that the safety of imported seafood be ensured through equivalent control measures in exporting countries. One-fifth of the fish and shellfish eaten in the United States is derived from recreational or subsistence fishing, and these products are not subject to health-based control; there is need to improve protection for consumers of these products by regulation of harvest and by education concerning risks associated with their consumption. Because the problems are largely regional, the primary effective control – except for imports – is at the state level, and this effort should be strengthened. However, there is need for federal oversight, general rule setting, and support to ensure the effectiveness of state-based programs and to provide expert assistance and specialized facilities. There is a lack of understanding of the nature of seafood hazards in the food service sectors and by the consuming public and health professionals; a vigorous campaign for information dissemination and education in these matters is needed, particularly for high-risk consumers and high-risk products such as raw shellfish. An improved national surveillance system should be developed to provide more reliable and comprehensive information on seafood-borne disease incidence. Data will then permit meaningful risk identification and risk assessment as a basis for effective regulation of seafoods (current data on disease occurrence in seafood consumption are too fragmentary to allow reliable risk assessment of microbiological and natural toxin hazards). A summary of hazards, risks, and their control for the major groups of hazardous seafoods in shown in Table 1-1. They are arranged in order of importance. Among seafood consumers, the group at greatest risk appears to be consumers of raw molluscs because of environmental contamination and naturally occurring vibrios. Consumers of recreational and subsistence fishery products are the second largest constituency at risk, both from natural toxins and from environmental contaminants. Inhabitants of islands in the Caribbean and tropical Pacific Ocean, and to a lesser extent of the Gulf of Mexico States, are uniquely at risk from ciguatera due to consumption of fish that feed on or near tropical reefs and prey upon reef fish. Although U.S. mainland inhabitants have developed the disease from imported fish, ciguatera is a highly regional problem that greatly skews disease reporting because of its geographical concentration and its high visibility in affected regions. There is a more general risk to consumers from certain fresh and frozen fish due to a milder toxic disease, scombroid poisoning. There is generally a low risk to seafood consumers of food-borne disease due to control failures during processing or at the food service level. Fish do not normally
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Seafood Safety carry microorganisms such as Salmonella or Campylobacter, which are commonly found in land animal carcasses and are the major causes of reported food-borne disease (though fish may acquire bacteria from contaminated water). Some ethnic practices in the preparation of fish for eating, place a small number of people at high risk from botulism, but this is not a significant hazard for most consumers of fish. Thus, the health risks associated with seafood – although diverse – are identifiable and, to a significant extent, controllable by innovative measures aimed at geographically restricted or species-specific problems. Some risks, particularly those associated with environmental contamination, may be increasing; their elimination will require a major commitment on the part of both government and industry to change methods of waste disposal in our society. These and the more visible hazards mentioned can be greatly mitigated by a regulatory system specifically aimed at the causes, be they natural toxins, microorganisms, or contaminants. However, this will require something other than organoleptically based inspection systems, which may be useful for quality control and grading but are essentially worthless for detecting and controlling health risks. NATURE AND EXTENT OF PUBLIC HEALTH RISKS General The principal source of data on the incidence of seafood-borne illness in the United States is the Centers for Disease Control (CDC). Its compilations are accumulated passively from state reports of food-borne outbreaks. An outbreak is an incident involving two or more sick individuals, except for botulism and certain chemical poisonings in which one sick individual constitutes an outbreak. A case is a single ill person. Unfortunately, not all states report each of the major types of seafood-borne disease, and within states there is considerable underreporting of incidents for a variety of reasons. Thus, CDC data may not be representative of actual disease occurrence and may omit altogether important seafood-originated disease outside the reporting format. The CDC information is useful when supplemented by other data on the occurrence of pathogens, an understanding of the patterns of seafood harvest and processing, a knowledge of the mechanisms of disease development, and – where available – independent epidemiological data. The CDC data cannot be used to estimate risks from chemical contamination, because no disease outbreaks have yet been reported from this cause. Seafood-borne illness reported by CDC in the 10-year period 1978-1987 totaled 558 outbreaks involving 5,980 cases. However, fish and shellfish constitute only 10.5% of all outbreaks and 3.6% of all cases when food-borne illnesses from all foods are considered. The number of people made ill from beef (4%) and turkey (3.7%) exceeds the seafood total, whereas pork (2.7%) and chicken (2.6%) are slightly lower. If shellfish (2.3%) and fish (1.2%) are considered separately, the number of reported cases from each is lower than for any animal meat category. Nevertheless, when only muscle foods (e.g., red meat, fish, poultry) are consumed, seafood-borne illness represents 56% of all outbreaks and 21% of all cases when incidents of unknown etiology are included.
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Seafood Safety TABLE 1-1 Hazards and Risks of Seafood Consumption and Their Control Arranged According to Order of Importance Hazardous Seafooda Hazardb Severity of Hazardc Risk to Consumersd Factors Enhancing Risk Factors Reducing Risk Present Control Systemse Deficiencies of Present Systemf Proposed Corrective Measures Raw bivalve molluscs (oysters, clams, mussels) (1) Viruses, enteric bacteria; (2) Vibrio species (1-2) Mostly mild gastroenteritis; (2) Severe for susceptible hosts High for consumers of raw molluscs (1) Polluted growing waters; (1-2) Temperature abuse; (2) Host factors (1-2) Cooking; (2) Rapid cooling; (1-2) Irradiation (1) Shellfish sanitation program; (2) None (1) Unreliable indicators; (2) No indicators (1) Identify reliable indicators; (2) Rapid method for Vibrio identification; chilling molluscs; radiation; (1-2) Wam consumers of dangers of eating raw seafood Naturally toxic finfish (1) Ciguatera; (2) Scombroid poisoning Moderately severe; Mild (1) High in endemic areas; (2) High for consumption of few species (1) Recreational fishing on reefs; (2) Temperature abuse after capture —; (2) Good temperature control (1) Voluntary harvest restriction; (2) Rapid cooling; histamine testing (1) No widely available test; (2) Limited effectiveness of control (1) Regulate fisheries; develop reliable, rapid test(s); (2) Enforce temperature control through HACCP system Molluscs (3) PSP, NSP, DSP, ASP Mild to severe (3) High if harvest is uncontrolled (3) Recreational shellfish harvest (3) Informed consumers (3) State surveillance and harvest control (3) Harvest closure not always effective (3) Additional policing and stronger advisories Chemically contaminated finfish and shellfishg (fresh water species, specific marine areas species) Environmental chemicals such as mercury, lead, cadmium, PCBs, dioxin, pesticides All levels mild to severe High for subsistence recreational fishers in certain areas, pregnant women, and children Subsistence and recreational fishing in areas of high contamination; species and fish portions eaten Decreased consumption (avoid during pregnancy); avoid high-risk areas and species; trim skin and fat Local regulations and advisories; some federal tolerance and action levels Action levels too few and too permissive; inadequate harvest management and control; noncancer effects poorly evaluated; poor contaminant data bases Further reductions in discharges; harvest restriction by site and species; improve advisories and possibly label fish; improve risk assessment for cancer and noncancer effects Processed seafood (1) Clostridium perfringens; (2) Salmonella; (3) Shigella; (4) Staphylococcus aureus; (5) Vibrio parahaemolyticus; (6) HAV; (7) Clostridium botulinum (1-5) Usually mild; (7) Severe Low when adequate cooking precedes consumption Cross-contamination; temperature abuse; processor presentation errors Adequate cooking; temperature control; proper processing and food service Sanitation inspection; process control Limited inspection; ineffective inspection methods; diverse processing Inspection and control based on HACCP system; improved temperature control on shipboard and during distribution NOTE: HACCP = Hazard Analysis Critical Control Point; PSP = paralytic shellfish poisoning; NSP = neurotoxic shellfish poisoning; DSP = diarrhetic shellfish poisoning; ASP = amnesic shellfish poisoning; PCBs polychlorinated biphenyls; HAV = hepatitis A virus. a Fish or shellfish, the consumption of which can lead to disease. b An organism, substance, or condition having the potential to cause disease. c Severe: may cause disability, extended sequelae, and in some cases, death; moderate: may require medical intervention to avoid debilitating or life-threatening effect, rarely self-resolving; mild: symptoms are transitory, rarely lasting more than a few days, no sequelae, no threat to life, usually self-resolving. d Probability that a consumer will become ill from the hazard. e Mechanisms to reduce or eliminate risk form hazard(s) by government, industry, or related individual action. f Aspects of control systems that reduce their effectiveness. g Presence of significant levels of undesirable chemicals (causing acute or chronic effects) in edible fish or shellfish tissue derived from natural environment of anthropogenic origin.
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Seafood Safety Natural seafood toxins – mainly ciguatera and scombroid poisoning and, to a lesser extent, paralytic shellfish poisoning – were responsible for 62.5% of all seafood-borne outbreaks of illness, but constituted only 28% of all reported cases. Shellfish-related incidents, although responsible for only 31% of the seafood illness outbreaks, involved 66% of all seafood-borne cases. Most of these (55%) were registered as of unknown etiology but are believed to be due mainly to Norwalk, Norwalk-like, or human enteric virus infections, with a smaller proportion caused by Vibrio bacteria. Fish-borne incidents due to causes other than natural toxins were only 9% of all outbreaks and 8% of all cases. They resulted mainly from bacteria, including common food-borne disease organisms, and from unknown etiology, suspected to be primarily enteric virus or recontaminant vibrios. Botulism is a specialized but significant component of fish-borne disease. Disease due to parasites was minimal (0.4% of outbreaks and 0.6% of cases reported from seafoods). Shellfish-borne disease occurs mostly from molluscs consumed raw or lightly heated, which constitutes the largest consumer risk. Ciguatera is a highly regionalized and intense risk for inhabitants and visitors consuming certain reef-associated fish in Caribbean and tropical Pacific islands and in adjacent mainland areas. Scombroid poisoning is widely distributed geographically but is specifically associated with consumption of certain fish species, particularly tuna, mackerel, mahimahi (dolphin), and bluefish. Botulism is a hazard for native American groups in Alaska that eat traditional fermented seafoods. Other risks are typical of food-borne disease in general and result from errors in handling, storage, or processing procedures. These are no greater than for other foods of animal origin. Intolerance to eating certain types of seafood is rare and more typically associated with certain individuals in risk categories predisposed by other health complications. Seafood allergies, distinguished as immunological reactions rather than the inability to digest, appear to be more prevalent, but they are difficult to diagnose and document. Specific allergens in seafood have thus far been only grossly characterized in few studies. Seafood intolerances and allergies can be due to food additives (e.g., sulfites) that cause symptoms and confuse diagnoses. Additional investigation of the biochemical and immunological characteristics of seafood allergies and their significance seems warranted. In light of this level of information on the cause and occurrence of this somewhat limited form of seafood-borne illness, regulatory response must depend on proper labeling to distinguish (1) species or seafood type, (2) ingredients in formulated and fabricated seafoods [e.g., fish base surimi (a washed mince of the separated muscle tissue from fish to which cryoprotectants are added) formed to resemble crab], and (3) ingredients used in preservation and processing (e.g., sulfites to retard shrimp melanosis). Microorganisms and Parasites Extent of Risk Seafoods, like any food item, have the potential to cause disease from viral, bacterial, and parasitic microorganisms under certain circumstances. These agents are acquired from three sources: (1) mainly fecal pollution of the aquatic environment, (2) the natural aquatic environment, and (3) industry, retail, restaurant, or home processing
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Seafood Safety and preparation. With the exception of foods consumed raw, however, the reported incidences of seafood-related microbial diseases are low. Available data from CDC and from the Northeast Technical Support Unit (NETSU) of the Food and Drug Administration (FDA) for 1978-1987, as well as literature reports, suggest that the greatest numbers of seafood-associated illnesses are from raw molluscan shellfish harvested in waters contaminated with raw or poorly treated human sewage. The majority of these illnesses have unknown etiologies clinically suggestive of Norwalk and Norwalk-like agents that cause human viral gastroenteritis. Although these are the most common seafood-associated illnesses, they tend to be relatively mild with no associated mortality. Except for Guam, naturally occurring marine Vibrio species are responsible for fewer reported cases of infections involving the consumption of raw molluscan shellfish, but certain species such as V. vulnificus can be associated with high mortality (>50%) in persons who are immunocompromised or who have underlying liver disease. The microbiological risk associated with seafood other than raw molluscan shellfish is much lower and appears to result from recontamination or cross-contamination of cooked with raw products, or to contamination during preparation followed by time/temperature abuse (e.g., holding at warm temperature long enough for microbial growth or toxin production to occur). This occurs mainly at the food service (postprocessing) level, which is common to all foods and not specific for seafood products. Seafood-related parasitic infections are even less common than bacterial and viral infections, with anisakids and cestodes having the greatest public health significance in the United States. In general, parasitic infections are concentrated in certain ethnic groups that favor the consumption of raw or partially cooked seafoods. Thorough cooking of seafood products would virtually eliminate all microbial and parasitic pathogens. Individuals who choose to eat raw seafood should be educated about the potential risks involved and how to avoid or mitigate them. In particular, immunocompromised individuals and those with defective liver function should be warned never to eat raw shellfish. The greatest risks from the consumption of raw molluscan shellfish could be minimized by research to develop valid human enteric virus indicators for the proper classification of shellfish growing waters; by implementing and maintaining proper treatment and disposal of sewage to avoid human enteric pathogen contamination of harvest areas; by efforts to identify and limit the number of pathogenic Vibrio species in shellfish; by developing new diagnostic methods and improved processing technologies; and by applying risk-based regulatory and control measures for potential microbial pathogens in raw molluscan shellfish. Other seafood-associated risks can be reduced by proper application of a Hazard Analysis Critical Control Point (HACCP) system. This cannot be achieved by the visual or organoleptic inspection currently used for meat and poultry. Seafood inspection should be directed toward identification of microbiological risks to consumers and the effectiveness of methods to reduce or eliminate such risks. Additional studies are necessary to determine levels of particular microorganisms that constitute a risk and that can be used as a basis for microbial guidelines. This requires appropriate epidemiological research. Inspection requirements should apply to imported as well as domestic products.
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Seafood Safety Principal Conclusions Most seafood-associated illness is reported from consumers of raw bivalve molluscs, and is due to unknown etiologies but is clinically suggestive of Norwalk-like viral gastroenteritis. The majority of incidents are due to consumption of shellfish from fecally polluted water. The disease is usually mild and self-resolving. Naturally occurring marine Vibrio species are responsible for fewer reported cases of infection from the consumption of raw molluscan shellfish, but species such as V. vulnificus can be associated with high mortality in persons who are immunocompromised or who have underlying liver disease. A lesser risk of microbial disease associated with other seafoods – resulting from recontamination or cross-contamination of cooked by raw product, or to contamination from other sources – is usually associated with time/temperature abuse. The etiologic agents most commonly involved, in order of reported frequency, are V. parahaemolyticus , hepatitis A, Salmonella, Shigella, Clostridium perfringens, and C. botulinum (mostly limited to Alaskan natives). Seafood-related parasitic infections are even less common than bacterial and viral infections, with anisakids and cestodes having the greatest public health significance in the United States. In general, parasitic infections have resulted from consumption of raw or partially cooked fresh- and salt-water fish of particular species (e.g., whitefish, salmon). Principal Recommendations Consumers should be informed of the risks of eating raw seafoods, particularly molluscan shellfish. Individuals belonging to high-risk groups, such as cirrhotics, people with hemochromatosis, or immunosuppressed individuals, must not eat raw shellfish; this requires that health professionals be educated concerning hazards to high-risk individuals. Adequate and proper treatment and disposal of sewage must be implemented to avoid contamination of harvest areas by human enteric pathogens. Valid indicators for human pathogen contamination of growing waters must be developed. Seafood-borne infections by human enteric viruses in raw and improperly cooked molluscan shellfish could be decreased significantly by the development of valid growing water indicator(s) and of direct detection methodologies for enteric viruses. Effective enforcement to eliminate recreational commercial and illegal harvesting and sale of molluscan shellfish from contaminated growing areas should be developed and adequately funded. Means must be investigated and implemented to eliminate, or at least reduce, levels of potentially pathogenic Vibrio species in raw shellfish. This may necessitate restriction of harvest when water temperatures are high, rapid cool-down and continued chilling of products, and possibly irradiation of live shellstock and shucked products. Consideration should be given to monitoring Vibrio counts in molluscan shellfish during warm months. Because of the high risks associated with raw molluscan shellfish, the importation of live shellfish for raw consumption should not be permitted unless
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Seafood Safety standards for the microbial quality of harvest waters and of harvest processing in the exporting country are fully equivalent to those in the United States. Consumers should be advised to cook seafood sufficiently to destroy parasites and bacterial contaminants before consumption. Control systems for microbiological hazards must include inspection techniques, preferably HACCP based, that specifically test for the hazard itself or for some condition that enhances or reduces hazard. Valid microbiological guidelines, established with an appropriate epidemiologic data base, are needed for seafood products. Special attention should be addressed to ensure the safety of seafoods processed by newer techniques, such as sous vide and the use of controlled atmosphere packaging, that are potentially hazardous. New or improved methodologies [e.g., enzyme-linked immunoabsorbent assay (ELISA), gene probe, polymerase chain reaction] should be developed that provide for the rapid identification and quantification of indicators, seafood-associated pathogens, and microbial toxins in seafoods and harvest waters. Natural Toxins Extent of Risk Incidents of illness due to naturally occurring seafood toxins reported to CDC in 1978-1987 were limited to ciguatera, scombroid fish poisoning, paralytic shellfish poisoning (PSP), and neurotoxic (brevetoxic) shellfish poisoning (NSP). Other intoxications, including puffer fish poisoning (PFP), were reported earlier; diarrhetic shellfish poisoning (DSP) and amnesic shellfish poisoning (ASP) are possible risks that should be anticipated. Naturally, toxic fish and shellfish are not distinguishable from nontoxic animals by sensory inspection, and the toxins are not destroyed by normal cooking or processing. Except for scombroid fish poisoning, natural intoxications are both highly regional and species associated, and toxins are present in the fish or shellfish at the time of capture. Scombroid poisoning is due to histamine produced by bacteria multiplying on fish that are mishandled after capture; illnesses are widely reported from different states. Ciguatera is a sometimes severe disease caused by consuming certain species of fish from tropical waters usually associated with islands or reefs. The disease is most common (endemic) in the Caribbean and Pacific islands, with some outbreaks in southern Florida and sporadic cases in other states caused by imported fish or tourist travel to endemic areas. Ciguatera was responsible for about half of all reported outbreaks of seafood intoxication in 1978-1987. The treatment is largely supportive, but mortality is low. At present, no effective control systems are in place for the prevention of ciguatera because a test for toxic fish is not generally available. Warnings and advisories concerning the hazards of ciguatera and the risks of consuming particular species of fish from ciguatera areas are issued by various states. Active control is proposed based on regulation of fishing for dangerous species, supported by testing suspect fish at dockside or on board the fishing vessel to detect and reject ciguatoxic fish. Increased education of the consuming public, sports fishers, and health professionals on the hazards and symptoms of ciguatera is also recommended.
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Seafood Safety During the same period, scombroid poisoning reportedly caused a similar number of outbreaks as ciguatera but was much more widespread in occurrence. Tuna, mahimahi, and bluefish were implicated as the major cause of scombroid poisoning in the United States. The disease is generally mild and self-resolving, and symptoms can be ameliorated by antihistamine drugs. Because the histamine that causes scombroid poisoning is produced after the fish have been caught, as a consequence of improper temperature control, the disease can be prevented by rapidly cooling fish after capture to 10°C or lower (e.g., 0°C if kept for an extended period) and holding them at or below this temperature at all times before cooking and eating. A HACCP-based system would control this poisoning for commercially handled fish, but the education of subsistence and recreational fishers is also necessary. Paralytic shellfish poisoning was a minor cause of seafood-borne illness in 1978-1987, with only two deaths reported. This is a remarkable record in view of the annual occurrence of toxic situations among shellfish on both the East and the West coasts of the United States, which indicates that current control measures applied by coastal states are highly effective. However, the increasing occurrence of toxic dinoflagellate blooms and changing eating practices (e.g., eating whole scallops) among some sectors of the consuming public require increased surveillance and the development of more rapid and simple tests for toxic shellfish. Although none of the other natural seafood intoxications, except for a single outbreak of NSP, have been reported recently by U.S. consumers, the potential for their occurrence either from domestically produced seafoods or from imports is real. Increased vigilance concerning imported products based on a requirement for certified nontoxicity is recommended. Moreover, both state and federal laboratories should be prepared to test for these "other" toxins, and procedures to deal with outbreaks should be in place. Principal Conclusions Natural toxin risks are highly regional or species associated. Natural toxins are present in the environment and are not affected by procedures during or after harvest. The one exception is scombroid shellfish poisoning, which is due to postharvest mishandling. Reliable, rapid tests for the natural toxins are either unavailable or not fully developed. Although PSP is well controlled by state inspection systems and industry controls are in place for scombroid poisoning, there are no regulations for the control of ciguatera. Recreational and subsistence fish eaters are at particular risk from natural toxins, and there is a lack of understanding by consumers of this risk. Principal Recommendations Control for natural toxins in the food chain should be at, or prior to, harvest, either by closures or by testing at the point of harvest.
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Seafood Safety Scombroid poisoning should be controlled primarily by rapid chilling on the vessel and by maintenance of refrigeration temperatures throughout distribution. Major emphasis should be placed on the development of rapid assays for each of the other natural toxins; without this, control is very difficult. Primary regulatory authority should be at the state level, with funding, quality control, and specialized assistance from a federal seafood safety program. Imported seafoods must be certified to be free of natural toxins through equivalency arrangements or more effective memoranda of understanding (MOUs) with exporters. An MOU refers to a formal agreement between a U.S. government agency (e.g., FDA) and another government agency (federal, state, local), or an informal agreement with a foreign government or other foreign institution. Educational programs on the dangers of natural seafood toxins must be developed for recreational and subsistence fishers, and health providers must be given information to improve the identification and treatment of illness due to seafood toxins. Chemical Residues Extent of Risk Fish and shellfish accumulate chemicals from the environment in which they live, but the extent of accumulation depends on such factors as geographic location, species of fish, feeding patterns, solubility and lipophilicity of the chemicals, and their persistence in the environment. Moreover, whereas land animals used for human consumption are fed mostly food of plant origin, aquatic animals that contribute to the human diet are generally predators of other animals and, in some cases, predators of predators. Because of this, chemicals have an opportunity to become more concentrated through bioaccumulation. The most difficult area for risk evaluation is the problem of chemical residues because the health effects suspected do not take the form of obvious, distinctive, and acute illnesses. The potential risks of concern (e.g., modest changes in the overall risk of cancer; subtle impairments of neurological development in fetuses and children) are generally quite difficult to measure directly in people exposed at levels that are common for U.S. consumers. Immunoincompetence may increase cancer risk. Inferences about the potential magnitude of these problems must be based on the levels of specific chemicals present, on observations of human populations and experimental animals exposed at relatively high doses, and on reasonable theories about the likely mechanisms of action of specific toxicants and the population distributions of sensitivity and human exposure. In nearly all cases the current state of knowledge on these subjects must be regarded as quite tentative. Additionally, the number and variety of chemical residues are substantial, although a small minority constitute the bulk of the risk that can be assessed quantitatively at this time. Overall, several chemical contaminants in some species of aquatic organisms in particular locations have the potential to pose hazards to public health that are great enough to warrant additional efforts at control. Available information suggests that these risks, in the aggregate, are not generally of a magnitude comparable to the highest environmental health hazards characterized to date; nevertheless, their control would significantly improve public health. Some examples of risks that may be
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Seafood Safety significant include reproductive effects from polychlorinated biphenyls (PCBs) and methylmercury; carcinogenesis from selected congeners of PCBs, dioxins, and dibenzofurans (all of which appear to act primarily by binding to a single type of receptor); and, possibly, parkinsonism in the elderly from long-term mercury exposure. Several other metallic and pesticide residues also warrant attention. Principal Conclusions A small proportion of seafood is contaminated with appreciable concentrations of potentially hazardous organic and inorganic chemicals from both natural and human sources. Some examples of the risks that may be significant include reproductive effects from PCBs and methylmercury, and carcinogenesis from selected PCB congeners, dioxins, and chlorinated hydrocarbon pesticides. Consumption of some types of contaminated seafood poses enough risk that efforts toward evaluation, education, and control of that risk must be improved. Present quantitative risk assessment procedures used by government agencies should be improved and extended to noncancer effects. Current contaminant monitoring and surveillance programs provide an inadequate representation of the presence of contaminants in edible portions of domestic and imported seafood, resulting in serious difficulties in assessing both risks and specific opportunities for control. Due to the unevenness of contamination among species and geographic sources, it is feasible to narrowly target control efforts and still achieve meaningful reductions in exposure. The data base for evaluating the safety of certain chemicals that find their way into seafood via aquaculture and processing is too weak to support a conclusion that these products are being effectively controlled. Principal Recommendations Existing regulations to minimize chemical and biological contamination of the aquatic environment should be strengthened and enforced. Existing FDA and state regulations should be strengthened and enforced to reduce the human consumption of aquatic organisms with relatively high contaminant levels (e.g., certain species from the Great Lakes with high PCB levels, swordfish and other species with high methylmercury levels). Federal agencies should actively support research to determine actual risks from the consumption of contaminants associated with seafood and to develop specific approaches for decreasing these risks. Increased environmental monitoring should be initiated at the state level as part of an overall federal exposure management system. States should continue to be responsible for site closures, and for issuing health and contamination advisories tailored to the specific consumption habits, reproductive or other special risks, and information sources of specific groups of consumers. Public education on specific chemical contaminant hazards should be
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Seafood Safety expanded by government agencies and the health professions. For specific contaminants in particular species from high-risk domestic or foreign geographic areas, government agencies should consider the option of mandatory labeling. Additional study of potential chemical contamination risks associated with both domestic and imported aquaculture products is required. Because of different standards for drug or agricultural chemical use and water quality prevailing in other countries, imported aquaculture products should be effectively certified as meeting U.S. standards. SCOPE AND ADEQUACY OF CURRENT SEAFOOD SAFETY PROGRAMS Regulatory Guidelines, Monitoring, and Inspection The current system of governance designed to protect the U.S. seafood consumer is composed of an intricate and complementary system of programs at the federal and state levels of government. Additional programs have been instituted in the private sector that offer a measure of industry self-regulation. At the federal level the principal responsibility for setting regulatory guidelines and for the surveillance and control of seafood safety is divided among the FDA, the Environmental Protection Agency (EPA), and the National Marine Fisheries Service (NMFS). Within states, responsibility may lie with one or more of their health, environmental, fishery, or agricultural departments. States generally tend to adopt federal regulatory guidelines. A primary role for the federal government is setting regulatory guidelines designed to promote inspection and enforcement activities both within and outside formal governmental programs. Existing regulatory guidelines can be divided into (1) those designed to reduce acute risk from microbial and natural toxin contaminants, and (2) those designed to reduce long-term or chronic risk due to chemical contamination. Guidelines for microorganisms and natural toxins are determined solely by the FDA and have been set primarily on an as-needed basis, that is, in response to a reported public health problem. Properly collated and effectively presented guidelines could provide a strong basis for the production and supply of safe seafood. However, in several areas related to new processing techniques and other emerging problems, new guidelines seem both appropriate and necessary. Setting federal guidelines for residual chemical contaminants is a task shared by EPA and FDA. Their strategy has been to focus on a limited number of chemical contaminants and to set regulatory limits by means of "action levels." Results of various federal and state efforts to monitor contaminant loads in the nation's marine and freshwater environments suggest strongly that several chemicals require a more fundamental review and evaluation. In terms of assessing and managing risks, the overall posture of relevant federal agencies, particularly FDA, appears to be almost totally reactive. In the committee's judgment, there has been less effort than would be desirable to discover and quantify hazards that are not yet on the public agenda, to evaluate options for reducing risks, and to implement policies that protect both the health of consumers and the stability of commercial markets.
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Seafood Safety One of the more important activities at both the federal and the state levels is environmental monitoring. Because the majority of seafood is from wild stocks, the quality of harvesting waters is of fundamental concern. The EPA and certain state governments [primarily by way of their involvement in the National Shellfish Sanitation Program (NSSP)] have instituted programs to establish the level of contaminants in seafood harvesting waters. These efforts have led to important insights into general water quality but, for the most part, do not supply sufficient information on the question of seafood safety. Among other things, they lack (1) sufficient geographic scope, (2) a common methodological approach, and (3) sufficient focus on the edible portion of seafood in order to determine public health, as opposed to environmental health, impacts. This last point is an important one. Except for the monitoring of harvesting waters carried out as part of the NSSP, data evaluating contaminant levels in fish and shellfish do not consistently focus on the analysis of edible tissue. More often the focus is on whole fish or on liver and gallbladder analysis. These analyses, by their design, offer insufficient insight into contaminant levels in the edible portion of seafood products. Inspection efforts by FDA and various state and local public health agencies are designed to ensure safety, but are insufficient to ensure in all cases that the regulatory guidelines defined by FDA and EPA are not being exceeded. The sampling strategies employed by these various agencies are designed to focus inspection and enforcement activities on areas in which the probability of a problem appears highest. Ongoing governmental efforts to develop new inspection programs, with a focus on the public health aspects of the raw product and the environment from which these products are derived, along with continued control of seafood production and processing, could provide measurable additional benefits in seafood safety. Given many of the intrinsic attributes of seafood already discussed, it is clear that an approach recognizing the advantages of regional/local control and surveillance is essential. The question of seafood safety should continue to be one in which federal and state roles are viewed as a cooperative partnership. It is also apparent that seafood commerce is taking place within an increasingly interdependent international economy. Many of the major trading partners of the United States are developing or further refining formal regulatory programs for seafood safety. These efforts should be taken into account in designing a domestic program. Principal Conclusions Federal (mostly FDA) guidelines for microbial and natural toxin contamination should be extended and updated. Those that exist have not been adequately conveyed to the fishing industry and to interested members of the public. Federal guidelines on chemical contaminants in seafoods are limited in scope and, in some cases, questionable as to the levels set. There is an apparent lack of coordination in the development and use of data on chemicals in the aquatic environment among FDA, EPA, the National Oceanic and Atmospheric Administration (NOAA), and the states. Better recognition is required of the importance of regional factors in the occurrence of toxic fish and shellfish and of the existence of high atrisk groups (e.g., pregnant women, children, recreational and subsistence fishers).
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Seafood Safety The present federal monitoring and inspection system is too limited in frequency and direction to ensure enhanced safety of seafoods. The monitoring process depends too much on evaluation of the product, rather than on safety of raw materials, with the single notable exception of the NSSP. However, even NSSP is not providing adequate protection because molluscan shellfish appear to cause most seafood-borne disease. Recreational and subsistence fishing is largely ignored in health and safety monitoring at the federal level. Consumers of seafood from these sources can be at high risk from natural toxins and chemical pollutants in certain regions and in particular species of fish. The health risks include cancer and the subtle impairment of neurological development in fetuses and children. The present system of data collection on seafood-borne illness by CDC does not provide an adequate picture of the extent and causes of such disease. Seafood advisories warning of local or species-associated health risks are issued mostly by state authorities and vary greatly in both their content and their distribution. Nevertheless, these advisories serve a useful purpose. Because of the regional nature of much of the domestic fisheries problems, states seem the logical level at which to tackle seafood control problems. However, help and guidance from the federal level are required. State programs for monitoring, surveillance, and control of seafood safety are generally in place in coastal states that use federal guidelines and action levels where these are available. However, the quality and effectiveness of the programs vary greatly as a function of the financial and administrative support available to the responsible state units, and in accordance with the character of the resource. A greater emphasis should be placed on the development of formal arrangements with foreign producers to guarantee that imported seafood has been harvested and processed in noncontaminated environments. Present training and education of industry and regulatory personnel are too limited both in scope and in number. Insufficient attention is given to the education of physicians and other health professionals on seafood safety and the characteristics of seafood-borne disease. This is also true of the consuming public. The regulation of imported seafoods to ensure safety is largely based on end product inspection and testing, except where MOUs exist. This is ineffective because it involves a mainly reactive process. The regulation of imported seafood products is carried out largely without regard to other national or international programs. There is tremendous variance in both regulatory limits for contaminants and inspection protocols in various countries, which leads to excessive and cumbersome inspection strategies for the importing state, and may also lead to a general reduction in the number of countries engaged in international seafood trade in the future. Principal Recommendations A more concise, comprehensive, and generally available single source for all FDA guidelines relating to seafood safety should be developed and updated on a regular basis. This information should be disseminated to industry and integrated into state regulatory processes through more routine and uniform training programs.
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Seafood Safety The development of an interagency structure with a single focus on seafood safety could contribute significantly toward increasing communication within the federal regulatory system, but the responsibility for primary control should be with the state. Federal agencies should develop a set of monitoring and inspection practices focusing more strongly on environmental conditions and on contaminant levels in the edible portion of seafood at the point of capture. Strong consideration should be given to creating a marine recreational fishing license system that is linked to the distribution of information characterizing the level and scope of potential risk from eating recreationally caught fish. Strong consideration should also be given to the closure of recreational harvest areas deemed to pose a threat to human health. The CDC should develop an active and aggressive program, founded on community-based health surveys, to better determine the level and source of seafood-borne illness in the U.S. population. Consideration should be given to the development of agreements with foreign authorities and individual producers to ensure that imported products are treated in a manner consistent with and equivalent to domestic products. A more pronounced and consistently defined federal role in the risk characterizations leading to seafood health advisories should be developed. A more consistent and focused effort in determining and communicating public health risks from contaminated seafood should also be developed. As more countries require the equivalency of domestic and imported products, it is apparent that the time has come for the international community to begin a process that would minimize the differences existing among national regulatory guidelines and approaches. OPTIONS FOR REDUCING PUBLIC HEALTH RISKS Monitoring, Control, and Surveillance Measures The current system involves (1) surveillance by federal and state agencies to identify seafood-borne disease (e.g., CDC and state health departments); (2) evaluation of risk and setting of guidelines and action levels mostly by federal agencies (e.g., EPA and FDA); (3) control of risk by inspection and testing of edible fish and shellfish (e.g., states, FDA, and NMFS); and (4) action to protect consumers by embargo, detention, seizure, or recall, and by issuance of warning advisories (e.g., states and FDA). This system needs revision and strengthening to develop a truly risk-based regulatory process. The data base on which regulation depends is inadequate. The disease surveillance system of CDC suffers from inadequate resources and should be refocused to provide a more complete and balanced account of seafood-borne disease. More analytical data on contaminants are needed, which could be obtained by increasing FDA analyses and sponsoring broader integrated studies of marine and fresh waters by EPA and corresponding state agencies. Inspection and testing should focus on actual problems (as in HACCP systems), and there should be increased efforts to develop rapid, reliable test methods for dangerous microorganisms, toxins, and contaminants. This will require a restructuring
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Seafood Safety of inspectional systems to accommodate newer methodologies and to train personnel in their application. Emphasis on purely sensory evaluation should be decreased. Problems of interagency jurisdiction, unclear regulations, or poor cooperation among state and federal agencies should be addressed and rectified. This will require added resources. Characteristics of Control Requirements Control measures should be applied initially at the earliest stage of seafood production by monitoring of water quality and condition. Such measures would apply to the molluscan shellfish problem and to most natural toxins and chemical contaminants, and would permit the exclusion of potentially dangerous fish or shellfish from markets by fishing closures and use of advisories. Rapid and simple tests should be developed and used to screen potentially hazardous fish or shellfish at the point of harvest to reduce costs to the fishermen and to protect the consumer from toxins and dangerous contaminants. Postharvest control seems likely to be most readily achieved through an HACCP-based system focusing on cross-contamination, temperature control, and the effectiveness of handling and processing methods designed to inhibit or destroy microorganisms. This system must be based on safety considerations, not solely on quality. The extent of chemical contamination of seafood species is both species and region dependent. A few chemicals such as mercury have strong species associations (e.g., swordfish). The concentrations of most organic chemicals tend to be less species associated and more dependent on geographic region. Within aquatic organisms, bioaccumulation may be organ specific or related to fat concentrations (e.g., methylmercury in muscle tissues and PCBs in fatty tissues). Improvement of the total data base on chemical contamination of fish could enable regulatory agencies to target their efforts on particular species of fish in specifically defined areas and, thus, lead to considerable mitigation of individual and societal health risks with minimal economic effects. Improvement of the data base could also enable consumers, especially subsistence and sport fishers, to select the least toxic fish in their waters for consumption. Clearly, however, chemical contamination is ultimately a problem of environmental degradation due to waste dumping that can be solved only by the development of systems to reduce chemical disposal in fresh and marine waters and in the atmosphere. The improvement of environmental quality will mean safer fish. The effectiveness of current fishing controls and consumer/fisher information programs in geographic areas with greater-than-average contamination problems is uncertain. Unfortunately, contaminated areas may be pocketed within broader fishing grounds, and the precise distribution of relatively high residue levels may be difficult to determine. In areas such as the Great Lakes, steps have been taken to prevent the commercial distribution of fish that have contaminants exceeding established tolerance or action levels. However, the adequacy of some regulatory levels is open to question in light of newly available information (see Chapter 6), and the degree of protection afforded the substantial population of consumers of sport caught fish by advisories based on those tolerance/action levels is even more doubtful.
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Seafood Safety Better control is needed of imported fish products, which represent over half of the fish and shellfish consumed in the United States. Seafood imports are coming from an increasing number of countries, some of which have poor internal control systems. A significant number of supplier countries are in tropical areas where some bacteria and toxin hazards are intrinsically high. Additionally, the United States is receiving increasing numbers of fish and crustaceans from foreign aquaculture operations (see Chapters 2 and 8). In view of the often regional and species-associated nature of seafood hazards, it would be appropriate to classify suppliers into risk categories for particular species or processed seafoods. Consideration should be given to extending the scope of MOU arrangements to cover all seafoods, and unfettered import of seafood products should be permitted only from countries with whom the United States has MOUs. Testing of imports for chemical residues should be carried out systematically according to a planned program designed to provide long-term estimates of the level of contamination in particular species or in the products of different supplier countries. In view of the very complex structure of international trade in fishery products, it is desirable that a better system be established to identify the country of origin of imported seafoods. This may require international agreements. Legislative Considerations Education and Information Measures Programs should be established for training regulators and seafood industry personnel to be proficient in the regulatory programs under consideration. These programs should be well-coordinated across states, with more national guidance and increased consideration of the unique attributes of various geographic regions. States should be required to produce advisories that can be used by both commercial and recreational personnel to learn about local public health risks and protective measures. In the development of advisories for reproductive effects, due weight must be given to the persistence of different toxicants in people. A useful federal function, besides producing advisories to meet national problems, would be development–with the states–of a standardized format for written and broadcast advisories so that there will be minimum confusion due to state and local differences. Educational programs for safe preparation and service of seafoods in commercial and home settings must also be developed and delivered as a part of an integrated seafood safety program. Recommendations for Improved Inspection Strategies Inspection should continue to be based on shared responsibility between state and federal agencies. The general philosophy presented here involves the concept of a federal agency (or agencies) having responsibility for identifying and characterizing risks, establishing methodologies and acceptable or actionable levels of undesirable agents, and monitoring state inspection programs. In addition, the federal agency would continue to have primary responsibility for imported products and products in interstate shipment. The agency would establish well-equipped regional laboratories to conduct tests for the federal program and–where appropriate–for state agency
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Seafood Safety programs. States, with the financial support of federal sources, would carry out inspections and apply police powers to in-state fishing industry operations, by using methods and procedures that meet or exceed federal standards. Monitoring and certifying state programs to determine their eligibility for federal funding of such operations would be the responsibility of the federal agency. Results would include better use of state agencies and strengthening their role in inspection, rather than depending solely on a federal agency to perform nationwide inspection. The federal agency should have overall responsibility for coordinating the national program and carrying out those functions that states cannot or will not undertake, as well as ensuring the training of state personnel. Organoleptic inspection must be recognized as inadequate and of little value for seafood safety because it is unable to identify risks to humans. Where new legislation is being considered in relation to the problems of seafood safety, the following important points should be considered: (1) the need to facilitate closure of harvesting areas on the basis of human health hazards, (2) the need for a strong state role in inspection that will require federal support, (3) the desirability of regulating vessels and dock facilities in relation to human health, (4) the collation of current regulations in easily available form, and (5) the need to train state and federal regulatory personnel. POTENTIAL IMPACT OF PROPOSED OPTIONS The proposed options outlined above will have the following impact on seafood and the consumer: (1) they will improve the general health of the public by focusing on the cause of disease, thus reducing the cases of seafood-borne diseases; (2) they will produce a quicker, more effective response when the public is subjected to unacceptable risks; (3) they will promote compliance through increased and improved communication among the involved agencies and industry, and through increased public knowledge; and (4) they will require the appropriation of funds to develop a comprehensive system incorporating the above recommendations. DIRECTION FOR DATA COLLECTION AND FUTURE RESEARCH Inasmuch as accurate risk identification is the first step in risk-based control programs, stronger epidemiologic data are needed to assess the extent of public health risk in terms of incidence, severity, vehicle, and setting. The two major viable data bases for seafood-borne illnesses from CDC and NETSU are too limited in scope and have discrepancies related to methods of surveillance and reporting that prevent consistent correlation of the outbreaks of some pathogens. In addition, more basic research is necessary to understand why and how certain pathogens or toxins cause illness. For example, there are bacterial pathogens, such as Vibrio vulnificus, or non-O1 V. cholerae that are commonly isolated from shellfish, that cause only a small number of clinical cases; we need to understand why only a minority of persons become ill after exposure to these organisms. Similarly, a better understanding is required of how natural toxins and chemicals are processed by fish, so that we can better predict when and where human illness will occur. Rapid, nondestructive, and
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Seafood Safety easy-to-perform tests for toxins, microorganisms, and chemicals [e.g., stick test for ciguatera, deoxyribonucleic acid (DNA) probes for specific viruses and bacteria, and instrumental chemical analysis] must be developed. The current programs for testing water and seafoods for potentially dangerous chemicals should be broadened to provide a satisfactory data base for regulation and control.
Representative terms from entire chapter: