A POSITION PAPER ON SELENIUM IN ECOTOXICOLOGY - A PROCEDURE FOR DERIVING SITE-SPECIFIC WATER-QUALITY CRITERIA

This paper describes a method for deriving site-specific water quality criteria for selenium using a two-step process: (1) gather informatio n on selenium residues and biological effects at the site and in down- gradient systems and (2) examine criteria based on the degree of bioac cumulation, the relationship between measured residues and threshold c oncentrations for reproductive effects in fish and wildlife, and any o bserved reproductive impacts, Several outcomes are possible-criteria c an be left unmodified, adjusted upward by a fixed amount (50%), or adj usted downward by one of three amounts (25, 50, or 75%), A criterion ( existing or proposed) is lowered or raised by an amount that is propor tional to the magnitude of bioaccumulation and toxic effects present-i .e., the degree of biological hazard, Criteria can be modified under t wo circumstances: (1) diagnostic residues and toxic effects must be co upled (present) in order to lower a criterion or (2) diagnostic residu es and toxic effects must be coupled (absent) in order to raise a crit erion, Coupling residues and effects makes the procedure sensitive to the natural inter-and intraspecific variation in bioaccumulation and t oxic responses exhibited by fish and wildlife in aquatic ecosystems, T he goal is to establish criteria that keep food-chain bioaccumulation below levels that result in toxicity to fish and wildlife. Precautions are given for those attempting to apply the generic EPA model for imp lementing national water quality criteria to a site-specific selenium criterion. (C) 1998 Academic Press.