Seafood Choices Balancing Benefits and Risks (2007) / Chapter Skim
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4 Health Risks Associated with Seafood Consumption
4 Health Risks Associated with Seafood Consumption
Pages 121-194
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From page 121... ...
The chapter concludes with a discussion of the interaction between nutrients and contaminants -- in particular, selenium and methylmercury -- in seafood, and measures that consumers can take to reduce exposure to contaminants that may be present in seafood. ENVIRONMENTAL CHEMICALS Consumers seeking the health benefits associated with the consumption of seafood are concerned about potential health risks associated with the presence of chemical contaminants, both those occurring naturally and those resulting from human activities, in seafood.
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The form of mercury of greatest concern with regard to seafood consumption is methylmercury (MeHg)
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. The mean blood mercury level in this group of men was 3.1 ppm, with a range up to 44 ppm, but the contribution of fish consumption to blood mercury levels is unknown because data were not collected on fish intake.
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had blood mercury levels greater than 5 µg/L, ranging up to 89 µg/L (Hightower and Moore, 2003)
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. No cases of Congenital Minamata Disease have been reported in the United States, where the primary concern has been whether chronic exposure to MeHg, as the result of seafood consumption among the general population, is associated with subtle adverse health outcomes.
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summarized these three cohorts in reviews. Seychelles Child Development Study The Seychelles Child Development Study (SCDS)
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hEALTh RISKS ASSOCIATED WITh SEAFOOD CONSUMPTION 1022 consecutive singleton births from 1986–1987. The objective of this study was to investigate possible neurobehavioral effects of prenatal exposure to neurotoxicants, such as methylmercury.
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, reliance on different biomarkers of exposure (cord blood mercury vs. maternal hair mercury)
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Ryan (2005) conducted an analysis of data from the three previously described studies using maximum likelihood and Bayesian hierarchical models to derive an estimate of the slope of the dose-response relationship between children's neurodevelopment and their prenatal methylmercury exposure.
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From page 130... ...
Part of the challenge in characterizing the health risks associated with increased MeHg exposure in seafood is related to the fact that this source also provides nutrients that might have health effects which mitigate those of MeHg. Thus, studies tend not to provide a "pure" estimate of MeHg toxicity but an estimate that represents the balance between the putative harm caused by the contaminant and the putative benefits provided by the
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From page 131... ...
This issue is critical, however, because the goal in giving advice regarding seafood consumption should be to enable people to obtain the greatest benefit for the least risk. An illustration of the delicacy of this balance is provided by a study of 135 mother-infant pairs in Boston (Oken et al., 2005)
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From page 132... ...
Most of the benefit appeared to be associated with any fish consumption, compared to none, as maternal consumption of fish more than one to three times per week did not seem to confer additional benefits, at least with regard to the child development outcomes assessed. Higher mercury concentration in umbilical tissue, for which the median was 0.01 µg/g wet weight, was not associated with adverse developmental outcomes in children, although cord tissue mercury is not a well-established biomarker of exposure.
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of death from coronary heart disease (CHD) (Salonen et al., 1995)
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(2002) study, increased toenail mercury was associated with increased risk of coronary heart disease.
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From page 135... ...
. A similar shift in the balance of the risks of methylmercury and the benefits of omega-3 fatty acids was found in a study of blood mercury level and blood pressure among US women (NHANES 1999–2000; Vupputuri et al., 2005)
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. Reference Dose calculations are sensitive to the assumptions made about factors such as the ratio of cord blood Hg:maternal blood Hg.
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The Faroe Islands and New Zealand studies are regarded as providing evidence that children prenatally exposed to methylmercury as the result of maternal seafood consumption during pregnancy are at increased risk of manifesting subtle neurodevelopmental
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From page 138... ...
Other Metals Metal contaminants other than mercury, including lead, manganese, chromium, cadmium, and arsenic may be present in seafood, although on a population basis, seafood consumption does not appear to be a major route of exposure to these metals. In analyses of farmed Atlantic and wild salmon, Foran et al.
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From page 139... ...
The POPs initially targeted by the agreement, informally called the "dirty dozen" (Table 4-2) , include: • Certain insecticides, such as DDT and chlordane, once commonly used to control pests in agriculture and building materials; • Polychlorinated biphenyls, used in electrical, heat transfer, and hydraulic equipment and as plasticizers in paints, plastics, and rubber products; • Certain chemical byproducts, such as dioxins and furans, which are produced unintentionally from most forms of combustion, including municipal and medical waste incinerators, open barrel burning, and industrial processing.
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From page 140... ...
. WHO recommends a tolerable daily intake of DLCs and PCBs of 1–4 pg/TEQ/kg/day (IOM, 2003)
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Adverse health effects associated with exposure to dioxins have been identified in populations exposed through unintended industrial releases. One of the largest population exposures to TCDD occurred from an unintended industrial release in Seveso, Italy.
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. Fish oils that are used for supplements tend to have lower levels of dioxins, DLCs, and PCBs than fatty or oily fish as a result of processing methods
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The results of these epidemiological studies are generally congruent with those using animal models, although, as in most areas of observational research in humans, results are not always consistent across studies or consistent over time in a particular study. Higher prenatal exposures have been associated with deficits in various functional domains including intelligence, attention, response inhibition, activity, and play behaviors (Jacobson and Jacobson, 1996; Patandin et al., 1999; Walkowiak et al., 2001; Vreugdenhil et al., 2002a,b; 2004; Jacobson and Jacobson, 2003; Stewart et al., 2003)
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From page 144... ...
and will require further research to understand. As PCB exposure levels continue to decline subsequent to federal laws banning PCB production, it may be difficult to characterize adverse health effects from low-level exposure (WHO Consultation on Risk Assessment of Non-Dioxin-Like PCBs, 2001; Ross, 2004)
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: • Structural relationships between congeners; • Binding to the AhR; • Toxic responses mediated through AhR activation; and • Persistence and bioaccumulation. The TEF value expresses the activity or toxicity of a specific congener relative to the toxicity of reference congeners, 2,3,7,8-TCDD; it is assigned a TEF of 1 and the toxicity of other congeners is expressed relative to TCDD (Van den Berg et al., 1998; IOM, 2003; SACN, 2004)
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. These risks are described later for analyzing benefits and risks associated with consuming farmed salmon (Foran et al., 2005b)
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. Polybrominated Diphenyl Ethers Polybrominated diphenyl ethers (PBDEs)
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. Limited data are available, however, on the association between seafood consumption and PBDE levels in human tissues.
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Given the substantial regional differences found in PCB levels, however, these analyses demonstrated the importance for the consumer of knowing whether a fish was farmed or wild-caught and also its region of origin. In a subsequent paper, the same group of investigators reported a quantitative analysis of competing risks and benefits associated with consuming farmed Atlantic and wild-caught Pacific salmon, for both cancer and noncancer end points (Foran et al., 2005b)
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assumed. These analyses represent a "worst case" scenario in that it is assumed that consumption of salmon would be the sole source of omega-3 fatty acids.
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combined. The purpose of the CDC national biomonitoring programs is to determine which environmental chemicals are absorbed, measure exposure levels, assess health impacts of exposure on population groups (e.g., pregnant women and children)
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Epidemiological studies have been conducted on the exposure of humans to mercury through consumption of fish and marine mammals in different geographical areas including Seychelles, the Canadian North, the Amazon, Faroe Islands, Papua New Guinea, and Sweden. There are inconsistencies among these studies in the toxic dose, which may be due to differences in dietary patterns between the populations studied, e.g., more whale meat is consumed in Faroe Islands and more fish in Seychelles (Chapman and Chan, 2000)
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. RISKS ASSOCIATED WITH MORE ACUTE SEAFOODBORNE HAZARDS Microbiological Hazards The best measures of seafood safety in the United States are based on illness reports compiled by the CDC (Source: http://cdc.gov/foodnet/)
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(1999) included cases and outbreaks involving Vibrios, which frequently implicate seafood, particularly raw molluscan shellfish, as a likely vehicle.
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With the exception of concerns for Vibrio and Norovirus infections, in general, the CDC report (2005a) does not reflect an increase in seafoodborne illnesses, particularly of microbial origin (most commonly associated with consumption of raw molluscan shellfish)
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HAV and NLV rare Allergies Host specific Host specific; Seafood ranked in top can be mild to four food allergies; severe could increase for pre formulated, value-added products NOTE: PSP = paralytic shellfish poisoning; NSP = neurotoxic poisoning; DSP = diarrhetic shellfish poisoning; ASP = amnesic shellfish poisoning; HAV = hepatitis A virus; NLV = Norwalk-like viruses (Noroviruses)
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cAt-riskconsumers include consumers with pre-existing health conditions, e.g., immunocompromised, that place the consumer in a predisposed category for seafoodborne illnesses. SOURCE: Revised from IOM, 1991.
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10 Bacillus cereus 2 Clostridium botulinum Salmonella typhi Vibrio cholerae, toxigenic Vibrio ulnificus SOURCES: Derived from Mead et al., 1999; 2006. TABLE 4-6 Seafoodborne Diseases Traced to "Molluscan Shellfish" in the United States from 1990 to 1998, and Outbreaks and Cases for Which the Etiological Agent Has Been Identified Outbreaks Cases Agent Total Percent Total Percent 18 27 733 22 V
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. California, Florida, Louisiana, and Texas represent "core states" des ignated in a V management plan designed by FDA through cooperation with the Interstate Shellfish Sanitation Conference (ISSC, 2002)
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Rainosek, National Oceanographic and Atmospheric Administration Fisheries, National Seafood Inspection Laboratory, Pascagoula, MS, July 2005 (Data prepared for the Interstate Shellfish Sanitation Conference)
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also reported a decline in "risky food consumption." This survey response showed a decline of one-third in the number of individuals who reported consuming foods, including raw oysters, associated with a higher risk for foodborne disease. Flattery and Bashin (2003)
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From page 162... ...
Infections in the United States are more sporadic and have involved crabs, shrimp, and crayfish, with cross-contamination of raw and previously cooked product as a contributing factor, although raw oysters remain the primary vehicle for Vp infections. Vp elicited little response from the National Shellfish Sanitation Program (NSSP)
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From page 163... ...
Studies suggesting that it is a gastrointestinal pathogen have not implicated seafood as a risk factor for illness.
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. Federal regulation prohibits the sale of any raw or cooked seafood products contaminated with any Salmonella, or cooked, ready-to-eat seafood products contaminated with any L
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They currently pose no unique trend in occurrences that suggest increased exposure risk through seafood consumption. Viruses There are a large number of seafoodborne illnesses of unknown etiology generally classified as norovirusal.
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From page 166... ...
estimated TABLE 4-10 Parasites and Products Involved in Documented Incidences of Parasitic Infection Fishborne parasites involved Some raw and undercooked seafood dishes involved in in human infections resulting parasitic infections for products and recipes that are not from consumptiona previously frozenb • Tapeworms (Cestodes) • Cold-smoked fish (low-temperature smoked fish)
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Nevertheless, seafoodborne parasitic infections are not common in the United States. The guidelines for seafood processing and handling that accompanied the FDA mandate for HACCP regulations introduced additional specific controls to further prevent seafoodborne parasitic infections (FDA, 2001a)
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. Given the widespread adoption of HACCP and infrequent incidence of reported infections, concern about parasitic infection may not be deterring consumers from raw seafood consumption.
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Absence of testable material, errant recall, and consumer misnaming can confuse species identification in reported illnesses. Despite product claims for utility, there are no reliable test kits to screen for ciguatera due to limited specificity for the toxins (Hungerford, 2005)
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The incidences of illness could increase as more supply of affected species is imported and the illegal sale of recreational fish is not addressed with pertinent enforcement. Shellfish Toxins Naturally occurring toxins that have been associated with illnesses resulting from the consumption of certain molluscan shellfish such as oysters, clams, and mussels harvested from locations with specific environmental conditions include: • Paralytic Shellfish Poisoning (PSP)
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The resultant food safety concerns, as for land-based agriculture, include possible toxic residue in the edible portions, contributions to potential antibiotic-resistant diseases (for both animals and consumers) , and concomitant issues involving environmental contamination.
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. The actual food safety risk resulting from the use of chemotherapeutants in aquaculture has been difficult to assess for lack of surveillance for the types and extent of use, and uncertainty about the hazards (FAO/NACA/ WHO Study Group, 1999; Caprioli, 2000; Hanekamp, 2003)
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. Since exposure is the mediating factor, occurrence tends to be more prevalent near coastal regions and will likely increase as per capita seafood consumption increases (Lehrer, 1993; O'Neil et al., 1993; O'Neil and Lehrer, 1995)
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requiring appropriate hazard analysis to identify any potential food sensitivity risks controlled through proper cleaning, product segregation, or product identification in order to prevent a potential hazard. Adverse Effects Associated with Omega-3 Supplementation While there is extensive research suggesting health benefits from the consumption of EPA/DHA found in fish oils, there are also data that indicate that overconsumption of fish oils could have adverse consequences.
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and lack of compliance with food safety guidelines (e.g., eating raw molluscan shellfish) persist, reviews of reported seafoodborne illnesses indicate that more acute seafood safety hazards are not
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From page 176... ...
; the new labeling requirements providing educational support; and specific management plans implemented by regulatory and industry partnerships to address the more serious illnesses associated with consumption of raw molluscan shellfish. However, the potential for misuse of chemotherapeutants in domestic and imported aquaculture products is a source for concern about the presence of toxins and increased antimicrobial resistance in seafood, particularly in light of increasing dependence on aquacultured products.
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8. Considerable uncertainties are associated with estimates of the health risks to the general population from exposures to MeHg and POPs at levels present in commercially obtained seafood.
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12. Reported seafoodborne illnesses indicate acute hazards are not increasing, but certain hazards associated with specific species and consumer preference (e.g., eating raw molluscan shellfish)
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2003. International trade and seafood safety.
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2000. Blood mercury levels and fish consumption in Louisiana.
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2000. Letter Regarding Dietary Sup plement health Claim for Omega- Fatty Acids and Coronary heart Disease.
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2001. Polybrominated diphenyl ethers: Occurrence, dietary exposure, and toxicology.
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1984. Prenatal exposure to polychlorinated biphenyls: Effects on birth size and gestational age.
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2004. Polybrominated diphenyl ethers in the environment and in people: A meta analysis of concentrations.
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2002. Exponential increases of the brominated flame retardants, polybrominated diphenyl ethers, in the Canadian Arctic from 1981 to 2000.
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2005. Differential effects of commercial polybrominated diphenyl ether and polychlorinated biphenyl mixtures on intracellular signaling in rat brain in vitro.
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2004. Polybrominated diphenyl ethers (PBDE)
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2005. Body burdens of polybrominated diphenyl ethers among urban anglers.
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1999. Effects of environmental exposure to polychlorinated biphenyls and dioxins on cognitive abilities in Dutch children at 42 months of age.
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2000. Fish oil-derived fatty acids, docosahexenoic acid and docosapentaenoic acid, and the risk of acute coronary events -- The Kuopio Ischaemic Heart Disease Risk Factor Study.
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2004. Polybrominated diphenyl ethers contamination of United States food.
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2003. Neonatal exposure to polybrominated diphenyl ether (PBDE 153)
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From page 193... ...
2005. Mercury, fish oils, and risk of acute coronary events and cardiovascular disease, coronary heart disease, and all-cause mor tality in men in eastern Finland.
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2002. Mercury and the risk of coronary heart disease in men.
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