Selenium and Mercury Interactions with Emphasis on Fish Tissue

Abstract

This review addresses the effects of mercury (Hg) in fish as it relates to the health of the fish themselves as well as potential risks of toxicity in wildlife and humans that consume fish. In particular, it addresses selenium (Se) as a bioindicator of susceptibility to harmful effects of Hg exposures and evaluates how Se moderates the toxic effects of Hg in a variety of test animals, emphasizing the importance of these potential effects in fish. A major conclusion of this review is that Hg toxicity risks to animal life cannot be accurately assessed without considering the moderating effects of Se. Therefore, Se:Hg molar ratios and their mathematical inverse are important factors that need to be considered when assessing risks from Hg exposures because exposures are related directly to toxicity outcome. In addition, actual measurement of both beneficial nutrients (e.g., Se, omega-3 fatty acids) and contaminants (e.g., Hg, polychlorinated biphenyls [PCB]) in fish tissue, rather than gross associations between the amounts of fish tissue consumed and changes in child IQ, motor skills, and verbal skill scores, has been recommended by human health effects researchers. This integrated approach will improve accuracy and reliability of environmental risk assessments for fish and fish consumers.

Keywords:

• mercury
• selenium
• toxicity
• Se–Hg interaction
• fish
• humans

Acknowledgments

The information in this document has been funded wholly (or in part) by EPA as part of the Environmental Monitoring and Assessment Program (EMAP). It has been subjected to review by the National Health and Environmental Effects Research Laboratory's Western Ecology Division and approved for publication. Approval does not signify that the contents reflect the views of the Agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use. Spencer Peterson is an employee of EPA, ORD, NHEERL, WED and an affiliate professor of animal science at Oregon State University. Nicholas Ralston was supported by EPA Grant CR830929-01 and by the National Oceanic and Atmospheric Administration, U.S. Department of Commerce Grant Award NA08NMF4520492, to the University of North Dakota Energy & Environmental Research Center. Phil Whanger, Jim Oldfield, and Wayne Mosher are all professors emeritus of Oregon State University, with long histories of research on Se and animal nutrition, who contributed their time freely to this paper. We thank Tony Olsen for assistance in interpreting the findings of Choi et al. (2007). Dave Peck assisted with references. In addition, we thank Dennis Lemly, Dixon Landers, Bob Ozretich, and Anne Fairbrother who offered very useful suggestions on an early draft of the basic information contained in this review. We also thank Julian Preston, Rita Schoney, and three anonymous journal reviewers for offering constructive recommendations for finalizing the paper.