By: Dana Sackett
Recent debates on fish selenium toxicity due to mining operations in southern Idaho have brought to light selenium’s toxic effects on fish populations and the various views on selenium policy from different environmental constituents (e.g., industry, Environmental Protection Agency (EPA), Fish and Wildlife Service (USFWS), Forest Service, Idaho Department of Environmental Quality, trout fishermen, and conservation groups.). This debate was highlighted in the NY Times in February of this year. Below I summarize some of the article and provide some more information on selenium.
|Picture of a phosphate mine in Florida. Source: http://inhabitat.com/land-values-increase-580-when-old-florida-phosphate-ore-transformed-into-energy-park/|
Selenium is naturally occurring and an essential nutrient at very low concentrations. Many selenium essential enzymes have oxidoreductase functions (enzymes that catalyze the transfer of electrons from one molecule to another; a fundamental biological process) among others. However, toxicity, particularly for fish and wildlife (which are generally more sensitive to selenium toxicity than humans) can occur when Se exceeds the concentrations required for metabolic functions (still a relatively low level; on the order of parts per million; ppm). Ecological impacts from selenium toxicity for fish are usually associated with early life stages because of the maternal transfer of Se to eggs. Fish are, therefore, particularly vulnerable when eggs are being formed.
|Brown trout fry deformed from selenium contamination. Source: greateryellowstone.org|
Toxic effects on fish and wildlife are commonly associated with mining, farming, and coal-burning. One of the first known cases of selenium toxicity on wildlife occurred in the 1980s. Lethal deformities in waterfowl (e.g. missing eyes and feet, deformed beaks, legs, wings and brains) were associated with excessive selenium in agricultural runoff in California. In West Virginia, Tennessee and others, mountain top coal-mining has been a large source of selenium contamination and in both North Carolina and Tennessee selenium contaminated fly ash from coal-fired power plants has caused fish kills, reproductive failure, and population declines.
|Snake River Canyon in southern Idaho. A trout stream connected to the Smokey Canyon phosphate mine where trout deformities have been reported. Source: http://www.treehugger.com/corporate-responsibility/selenium-contamination-two-headed-trout-near-phosphate-mine-idaho.html|
The debate over the mining operation in Idaho started because the Smokey Canyon phosphate mine, owned by the J.R. Simplot Company, conducted research and provided a report concluding that it would be safe to allow the current levels of selenium contamination, which were above permitted regulatory guidelines, to remain high. The Fish and Wildlife Service reviewed the report and found it “biased”, “highly questionable”, and though the report did not provide raw data, a FWS scientist was able to estimate that reported rates of trout fry deformities were underestimated by approximately 50%.
|Pictures of deformed trout fry from the Simplot report. Source: http://www.flyrodreel.com/blogs/tedwilliams/2012/february/selenium-causes-trout-deformities|
Worrisome to conservation groups and some political officials, the trout data from the Smokey Canyon study has already been included in the national database used to help establish national standards on selenium contamination. These standards seem to already be a point of contention as the EPA and FWS disagree on a safe level to protect aquatic populations (EPA 7.9 ppm, FWS ~4 or 5ppm).
|Effects of selenium toxicity on two species of fish. Source: pnas.org|
The Simplot company is responsible for the cleanup of the resultant contamination under Superfund law. In accordance with this law, Simplot has spent millions of dollars in an effort to clean-up the contamination; however, the concentrations of Se in the water still exceed the federal limit by 14 times and more work is needed.
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