Poster Topical Area: Maternal, Perinatal and Pediatric Nutrition

Location: Hall D

Poster Board Number: 363

P13-105 - Freshwater Fish From Selenium-Poor Regions Bioaccumulate More Mercury and May be More Toxic to Subsistence Consumer Populations Than is Generally Recognized

Sunday, Jun 10
8:00 AM – 6:00 PM

Objective

To establish a more reliable index of mercury (Hg)-exposure risks in relation to its adverse effects on selenium (Se)-dependent enzyme activities in the brain, the U.S. EPA supported development of the Health Benefit Value (HBV). This criterion is simple to calculate (HBV = ((Se – Hg)/Se) x (Se + Hg) and easy to understand, being positive when Se is present in molar excess of Hg, but negative if Hg exposure is high enough to impair Se transport and activities. The Se and Hg contents of freshwater fish are far more variable than those of ocean fish, potentially exposing subsistence fish consumers in certain regions of the world to far greater risk than current Hg guidelines predict. This study examined freshwater fish Hg, Se, and HBVs to establish criteria for protecting consumers from Hg-exposure risks.



Methods
Selenium and Hg data from >14,000 individual ocean and freshwater fish gathered by federal, state, and other organizations were used to calculate the HBV ranges of >100 fish species. Commonly consumed North American varieties: Perca flavescens (yellow perch), Sander vitreus (walleye), Esox Lucius (northern pike), Microopterus salmoides (largemouth bass), Lepomis machrochirus (bluegill), and Ictalurus punctatus (channel catfish) are included in the current analysis.



Results

Because Se is homeostatically controlled, its concentrations in fish are largely independent of fish size. In contrast Hg bioaccumulation in freshwater fish increased in direct relation with increasing body weights (p<0.001). However, it is important to note that Hg bioaccumulation was inversely related to Se availability in all species assessed (p<0.05). For walleye, northern pike, and largemouth bass, samples from low-Se areas were found to have negative HBV's.



Conclusions

The inverse relationships between Hg and Se in freshwater fish confirm findings reported by prior studies. Because Hg bioaccumulation and Hg toxicity risks both tend to increase when Se-availability is poor, there is an urgent need to assess HBVs of fish in regions where subsistence freshwater fish consumers and their children may be greater risk than would be predicted by criteria based on Hg alone. The SAMPLLE (Selenium Assessments in Mercury Polluted Lentic and Lotic Ecosystems) Program is organizing international research ream collaborations.



Funding Source: This project; "Fish Selenium-Health Benefit Values in Mercury Risk Management", was funded by EPA-G2009-STAR-B1 grant to the University of North Dakota.
Freshwater fish Hg-Se relationships

CoAuthors: Laura Raymond, Ph.D. – University of North Dakota

Nicholas VC.. Ralston

Research Scientist
University of North Dakota
Grand Forks, North Dakota