Human Health Risks of Selenium-Contaminated Fish: A Case Study for Risk Assessment of Essential Elements

ABSTRACT

A screening level human health risk assessment (HHRA) was applied to evaluate the human health implications of consuming selenium found in fish tissues collected downstream of coal mines in southeastern British Columbia, Canada. The study evaluated the potential for adverse human health effects associated with selenium, and considered known and potential benefits of selenium and fish ingestion. The results indicated that risks of selenosis due to consumption of selenium-contaminated fish in the region are negligible. Conclusions were strengthened by consideration of the potential benefits of selenium to human health, including: selenium essentiality for maintenance of good health; potential cancer prevention properties due to its role as an antioxidant; potential benefits for cardiovascular health; and other positive health benefits. The findings indicated that some aspects of the traditional framework for HHRA (e.g., application of safety factors to “err on the side of safety”) are inappropriate for the assessment of selenium-contaminated fish. Due to both deficiency and toxicity in the selenium dose-response relationship, application of compounding conservatism in risk assessment may lead to recommended intakes of fish that are contrary to the public health interest. The need for balancing risk types, for incorporating positive responses in risk assessments, and the linkage to the precautionary principle, are discussed.

Key Words:

• selenium
• human health
• risk assessment
• essential elements
• fish

ACKNOWLEDGMENTS

We thank Elk Valley Coal Corporation (EVCC), Calgary, AB, Canada, for funding and particularly Roger Berdusco (EVCC) for the impetus to publish this study. We also thank Audrey Wagenaar for review of the draft manuscript, which was improved by comments from three anonymous referees.

Notes

¹Denotes upstream reference locations within the watershed.

²Denotes exposed locations subject to selenium enrichment from mining operations.

³95% upper confidence limit about the arithmetic mean concentration.

¹Exposure Scenarios:

²Exposure calculations based on upper bound of selenium tissue concentration distribution (90th percentile).

³Relative bioavailability of selenium in fish set to 70% (all other sources 100%) relative to bioavailability in human epidemiology studies; background ingestion of 224 g/day assumed.

¹Moderate conservatism means that the value is more likely to overstate risks than understate risks. High conservatism means that the assumption will necessarily overstate risks, and introduces a significant margin of safety into the overall risk calculation.