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

(ARN-1117-827247) Site-specific, regional, or national metals criteria? — A case study with copper in San Francisco Bay.

Arnold, W¹, Warren-Hicks, W², ¹ Copper Development Association Inc., New York, NY, USA² EcoStat, Inc., Mebane, NC, USA

ABSTRACT- A large number of scientific and regulatory issues underlay the methods and procedures for determining and implementing metals criteria. In this presentation, we will explore the issues surrounding the geographic scale defining metals criteria. Should metals criteria be site-specific, regional, or national? How is the optimal geographic scale defined for a specific metal? What are the analytic processes that guide such decisions? What are the key issues that industry and government should consider in making these decisions? These questions will be explored through examination of approaches used to establish copper criteria in San Francisco Bay. For example, the national chronic criterion for copper in saltwater (salinities >1 g/L) is 3.1 g Cu/L. However, the US EPA allows for the development of site-specific criteria. One method commonly used to develop site-specific criteria is the water-effect ratios (WER) method. The site-specific criteria are equal to the national criteria multiplied by the WER (EC50 of copper in site water/ EC50 of copper in laboratory water). Representatives of non-government organizations, regional water quality authorities, consultants, publicly owned treatment works and industry worked together using the WER method to establish two site-specific copper acute and chronic criteria for the Bay. In recent work, Arnold and Warren-Hicks (in review) have developed and applied probabilistic approaches for estimating site-specific copper criteria in San Francisco Bay that account for both temporal and spatial variability of site-specific water chemistry. This method makes use of low cost and often readily available historical water quality information. The results of using the probabilistic methods raises concern over the appropriateness of applying the WER approach when using limited spatial and temporal data. This presentation will compare and contrast the scientific merits of site-specific, regional, and national criteria. Illustrations from San Francisco Bay will be used to support the discussion.

Key words: copper criteria, site-specific, probabilistic, San Francisco Bay