Grantee Research Project Results
Final Report: Fish Selenium Health Benefit Values in Mercury Risk Management
EPA Grant Number: R834792Title: Fish Selenium Health Benefit Values in Mercury Risk Management
Investigators: Ralston, Nicholas V.C. , Raymond, Laura
Institution: University of North Dakota
EPA Project Officer: Hahn, Intaek
Project Period: April 1, 2011 through March 31, 2013 (Extended to March 31, 2015)
Project Amount: $490,089
RFA: Exploring Linkages Between Health Outcomes and Environmental Hazards, Exposures, and Interventions for Public Health Tracking and Risk Management (2009) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Human Health
Objective:
In parallel with the U.S. Environmental Protection Agency (EPA) Environmental Indicator Initiative, the goal of this project was to link a national-level indicator of methylmercury (MeHg) exposure to actual health outcomes. In accordance with this goal, the objective of this research was to further develop an accurate indicator of MeHg risk that can be used for long-term tracking and surveillance of environmental public health, which will be used for making better-informed decisions and recommendations of fish consumption, and that will aid in assessing the actual impacts of these environmental risk management resolutions. To attain the objective of this application, the following goals were pursued:
- Access, evaluate, calculate, and establish Se-Health Benefit Values (Se-HBVs) (updated to Health Benefit Values of Selenium [HBVSe]) for ocean fish, identifying and quantifying any distinctions that may exist between fish originating from the Atlantic, Pacific, or the Gulf of Mexico.
- Compile data obtained from studies of freshwater fish in order to access, evaluate, calculate, and establish Se-HBVs (updated to HBVSe) for lakes, rivers, and streams across the United States.
- Extend the computational Physiologically Oriented Interactions of Nutrients and Toxins (POINT) model to a multiple-tissue compartment that can use blood Hg and Se data to predict end point outcomes in epidemiological studies.
Summary/Accomplishments (Outputs/Outcomes):
The Hg, Se, and HBVSe results on over 13,000 ocean and freshwater fish and shellfish have been examined and reported. In summary, the majority of freshwater and ocean fish contain Se in excess of Hg. Therefore, consuming these types of fish is expected to be beneficial instead of harmful. However, human and wildlife consumers of freshwater fish that contain Hg in excess of Se may be at substantially higher risk than is currently recognized. Risks from Hg exposure are not linear but may instead be synergistically related to Hg:Se molar ratios in excess of equimolar stoichiometries. Therefore, efforts are urgently needed to identify areas with water bodies that may contain such potentially high risk fish.
With few exceptions, the majority of varieties of ocean fish and other seafoods were found to have positive Se-HBVs. Although the Se-HBVs of these varieties of fish were all found to decline as the fish grew larger and older (primarily because of Hg bioaccumulation), in most cases, the Hg:Se molar ratios in these species do not appear likely to become negative in even the largest specimens. Varieties of ocean fish with low or negative Se-HBVs tended to be top predatory species, primarily certain varieties such as mako shark. Swordfish Hg and Se concentrations tend to be nearly equal; therefore, their Se-HBVs hover around zero.
The concentrations of Hg and Se present in freshwater fish were far more variable than those observed in ocean fish. The relationships between fish Hg and Se contents were investigated in relation to weight to identify varieties and locations where accentuated risks due to Hg contents in excess of Se occur. As we had hypothesized, freshwater fish species with MeHg bioaccumulations in molar excess of Se seem to originate from regions of North America with notably Se-poor soils or areas with low pH that limit the biological availability of Se naturally present in soil and water. Therefore, the regions where accentuated risks associated with high Hg exposures associated with consumption of freshwater fish with negative SeHBVs may be somewhat predictable based on the environmental availability of Se.
The edible meats of predatory whales, certain types of shark, swordfish, and a few other seafoods have significantly negative HBVSethat indicates maternal consumption of these varieties may have adverse effects on fetal neurodevelopmental outcomes. Therefore, those types of seafoods should be avoided during pregnancy, especially by women with poor dietary Se intakes from their background diets. However, most varieties of ocean fish have positive HBVSe, indicating their consumption offers adequate Se to not just offset the MeHg, but also to improve the nutritional status of the consumer. The HBVSe criterion provides an accurate and easily understood index for assessments of seafood safety.
Conclusions:
Assessments using this criterion coincide with the 2004 and 2014 U.S. EPA-U.S. Federal Drug Agency (FDA) advisories for pregnant women regarding the four types of fish that should be avoided. Recommendations based on the HBVSe criterion are more understandable since they enable consumers to recognize that foods with a positive value are beneficial to eat during pregnancy, while those with negative values need to be avoided. Since consumption of fish with negative HBVSe poses risks to humans and piscivorous wildlife that may not be recognized when using criteria that reflect Hg only, this subject urgently requires further study. We informed organizations that assess Hg concentrations in ocean or freshwater fish that it is important for them to include Se assessments and consider employing HBVSe criterion in their future Hg risk assessments.
These results support the recent recommendation that pregnant women should consume a minimum of 8 oz of ocean fish weekly but should avoid shark, swordfish, and any other seafoods with high MeHg but poor Se contents. Because consumption of freshwater fish with negative HBVSe poses greater risks to humans and piscivorous wildlife and since poor environmental Se availability greatly increases MeHg bioaccumulation in freshwater fish, studies are needed in order to identify and more closely examine MeHg and Se contents of fish from low-Se areas. This is an especially important consideration in regions of the world that are known to have Se-poor soils. Since Hg-Se interactions are pivotal aspects of the global Hg issue, EPA can use its leadership role to assist other nations and develop remediation approaches that will most effectively protect and improve public and environmental health.
Journal Articles on this Report : 3 Displayed | Download in RIS Format
Other project views: | All 25 publications | 6 publications in selected types | All 5 journal articles |
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Gilman CL, Soon R, Sauvage L, Ralston NVC, Berry MJ. Umbilical cord blood and placental mercury, selenium and selenoprotein expression in relation to maternal fish consumption. Journal of Trace Elements in Medicine and Biology 2015;30:17-24. |
R834792 (Final) |
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Ralston NVC, Ralston CR, Raymond LJ. Selenium Health Benefit Values: Updated Criteria for Mercury Risk Assessments. Biological Trace Element Research 2016;171(2):262-269. |
R834792 (Final) |
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Ralston NVC, Raymond LJ. Mercury's neurotoxicity is characterized by its disruption of selenium biochemistry. Biochimica et Biophysica Acta (BBA)-General Subjects 2018 doi:10.1016/j.bbagen.2018.05.009 [in press]. |
R834792 (Final) |
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Supplemental Keywords:
Risk management, ecological effects, marine, estuary, bioavailability, metabolism, vulnerability, sensitive populations, dose-response, susceptibility, aquaticProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.