W7 PM Metals in the Environment: Regulatory and Risk Concerns
Wednesday, 16 November 2005: 1:50 PM - 5:30 PM in 327-329

(DEF-1117-751459) Uncertainties in estimating whole body selenium concentrations in fish from other tissues and implications for tissue-based criteria.

DeForest, D¹, Robinson, S¹, ¹ Parametrix, Bellevue, WA, USA

ABSTRACT- The USEPA has released a draft selenium criterion of 7.91 mg/kg dry wt. in whole body fish tissue. Although it is generally agreed that a fish tissue-based selenium criterion is more appropriate than a water-based selenium criterion, and that whole body tissue is the most practical tissue for implementing such a criterion, there are potentially significant uncertainties associated with a whole body selenium criterion. The draft criterion is based on the combined effects of selenium and cold temperatures (winter stress syndrome) on juvenile bluegill sunfish survival. However, because this species and endpoint may not be applicable to water bodies nation-wide, it is possible that alternative tissue-based standards may be developed on a site-specific basis. Not considering winter stress syndrome, reproductive effects (embryo-larval deformities and mortality) has generally been observed to be the most sensitive endpoint. Although whole body selenium has generally been shown to be a reasonable predictor of reproductive toxicity in fish, whole body selenium toxicity data are relatively limited and the USEPA relied on regression relationships to estimate whole body selenium toxicity thresholds from muscle, ovary, and liver selenium data to expand the toxicity data set for deriving a criterion. However, these data do not always correlate well with the toxicity endpoint evaluated. For example, in one reproductive study, the whole body selenium concentration in rainbow trout was estimated to be 5.79 mg/kg based on muscle selenium data and 15.6 mg/kg if estimated from egg selenium. In this poster, differences in selenium bioaccumulation patterns between tissues and fish species are reviewed and the potential implications for development of tissue-based criteria are discussed.

Key words: selenium, fish tissue, criteria