The federally recommended chronic criterion for selenium to protect aquatic life in fresh water is 5.0 parts per billion (ppb or μg/l). The current recommended chronic criterion of 5 ppb was developed in 1987 in the wake of selenium poisoning to fish at Lake Belews in North Carolina. Most aquatic criteria for metals or salts are developed based on the exposure of aquatic life to the dissolved component of the metal or salt. For selenium, though, the primary pathway of harm to fish is through diet and accumulation in fish tissue. Over the past two decades, scientists have learned that selenium accumulates in fish tissue at different rates depending on algae uptake, and that the 5 ppb water column concentration can be unnecessarily overprotective—especially in faster-flowing waters.
Accordingly, in 2004, USEPA proposed to change its chronic criterion to a standard based on selenium concentrations in fish tissue rather than in the water. USEPA, however, has long delayed finalizing its proposed fish tissue-based criterion. Many believe the delays have less to do with the need for additional scientific review than with pressure applied by anti-mining groups seeking to retain a punitive and easy to apply 5 ppb water column concentration. In the meantime, the coal industry has been forced to accept an increasing number of NPDES permits with selenium limits set to keep in-stream concentrations below 5 ppb—arguably a needlessly protective standard that is costing the industry millions of dollars.
In May 2013, Kentucky submitted to USEPA a proposal to change both Kentucky’s chronic and acute selenium standards to protect aquatic life. Its proposed chronic standard was a tissue-based standard similar to the one being reviewed by USEPA: either 8.6 μg/g (parts per million) dry weight of whole fish or 19.2 μg/g dry weight of fish egg/ovary. Its proposed acute standard was still a water column-based value of 258 μg/l.
• If the NPDES permit writer determines there is a “reasonable potential” that a discharge will cause in-stream concentrations to exceed 5.0 ppb, then water monitoring will be required.
• If the “average effluent selenium concentration” exceeds 5 ppb as reported in the Discharge Monitoring Report, then the permit holder will be required to collect and analyze fish tissue. If the tissue levels exceed the tissue standards, then the permittee will have violated its permit.
• If fish tissue samples cannot be obtained in accordance with a protocol Kentucky is developing, then the in-stream standard will default to 5 ppb rather than to a fish tissue standard.
This article was authored by Robert McLusky, Jackson Kelly, PLLC. For more information on the author, see here.
 USEPA’s current recommended criteria do not include an acute standard. USEPA adopted an acute standard of 20 μg/l for the Great Lakes, but withdrew it in response to a lawsuit challenging the application of a single value to two different forms of selenium: selenite and selenate. See 69 Fed. Reg. 75541, 75543 (Dec. 17, 2004); AISI v. Envtl. Protection Agency, 115 F.3d 979 (D.C. Cir. 1997).
Today, USEPA’s recommended acute criteria include a footnote setting out a formula for the criteria maximum concentration based on the relative proportions of selenate and selenite comprising the selenium (recognizing the more toxic nature of selenite). According to USEPA, that formula was proposed in 2004, but never adopted. The note continues, though, stating that “[h]however, based on findings from a February 2009 SETAC . . . workshop . . . diet is the primary pathway of selenium exposure to aquatic life and traditional methods for predicting toxicity on the basis of exposure to dissolved concentrations is not appropriate for selenium.”
 The proposed standard provided that if the concentration of sulfate in the water was less than 44 mg/l, then an alternate standard could be obtained by using a formula which relied on the proportions of selenate and selenite.
 The approval appears to be subject to a final Endangered Species Consultation with the USF&WS.
 It is unclear whether the use of the word “effluent” is a mistake. The level which should trigger fish tissue collection and analysis should be the effluent concentration which causes the in-stream concentration of selenium to exceed 5 ppb. That concentration in the effluent could be substantially higher than 5 ppb without causing in-stream levels to exceed 5 ppb.
 The letter to USEPA provides that the State has developed draft tissue collection procedures which rely on collection of fish in “successive stream segments” below a discharge point. It also provides, though, that where sufficient fish tissue samples cannot be collected, then the criterion will be 5.0 ppb in the water column.