T4 AM Endangered Species and Environmental Contaminants: Status of the Science (Part 1)
Tuesday, 15 November 2005: 8:00 AM - 11:40 AM in Ballroom 4

(LUO-1117-288680) Uncertainties in managing Se contamination: Need for a new direction.

Luoma, S¹, Presser, T¹, ¹ US Geological Survey, Menlo Park, CA, USA

ABSTRACT- Disarray can be the outcome when contradictions occur between simplified approaches to managing chemicals, and the realities of how those chemicals exert their effects in nature. The hazard and risk of Se are best appreciated when the full state of knowledge is incorporated. Dissolved speciation of Se is variable among environments. Speciation controls phase transformation from dissolved to particulate or primary producer. Exposure of animals occurs exclusively via diet. Phase transformation thus controls consumer bioaccumulation. Differences in consumer physiology adds to the variability of bioaccumulation among invertebrates. This variability is propagated up food webs by efficient trophic transfer. Therefore, the greatest threats occur to some species at the highest trophic levels (exposure defines vulnerability); and threats to endangered species are common. It follows from the state of the science, that the inherent hazard of Se is underestimated by traditional approaches: BCFs are variable and underestimate bioaccumulation; dissolved toxicity has little to do with how toxicity is manifested in nature. Information on Se toxicity to wildlife via diet is relatively reliable. But it is problematic to characterize risk by tying wildlife tissue criteria back to a dissolved concentration without considering the intervening processes. Failure to include diet in traditional Se toxicity tests usually will lead to under-protection. But failure to consider other processes that affect the tie between concentration and toxicity usually will lead to overprotection. The latter is problematic because remediating Se contamination is difficult, and can make things worse. Thus, differing views of the precautionary principle add heat to the Se dialogue. We propose here a holistic protocol for site specific, watershed-based evaluations/predictions of risk from Se. We further suggest that dialogue about how to improve such approaches, rather than advocacy debates, will be most constructive in managing chemicals where traditional approaches have marginal relevance, especially to endangered species.

Key words: selenium, San Francisco Bay, Water Quality Criteria, Toxicity tests