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Barbara Baginska San Francisco Bay Regional Water Quality Control Board

Advisory Committee Meeting #3 September 16, 2008 North San Francisco Bay Selenium TMDL Draft Numeric Target. Barbara Baginska San Francisco Bay Regional Water Quality Control Board. Presentation Overview. Background: Numeric targets in TMDL context Problem in North SFB

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Barbara Baginska San Francisco Bay Regional Water Quality Control Board

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  1. Advisory CommitteeMeeting #3September 16, 2008North San Francisco BaySelenium TMDLDraft Numeric Target Barbara Baginska San Francisco Bay Regional Water Quality Control Board

  2. Presentation Overview • Background: • Numeric targets in TMDL context • Problem in North SFB • Exposure types and bioaccumulation • Target Development • Species at risk in North SFB • Toxicity thresholds for local ducks and fish (exposure levels, local data, mitigating conditions) • Fish tissue-based target: why and how? • Proposed target and rationale

  3. Numeric Target - Definition Numeric targets are specific goals for TMDLs that ensure protection of designated beneficial uses of waters and provide basis for data analysis and allocations

  4. Numeric Target - Selection • A numeric target can be: • numeric water quality objective • numeric interpretation of narrative objective; or • numeric measure of some other parameter necessary to meet water quality standards • Usually expressed as specific water column, sediment and/or tissue indicator • Will demonstrate attainment of water quality standards • Easy to monitor

  5. Water Quality Criteria • San Francisco Bay and Delta Freshwater numeric criteria apply: • Acute-Criterion Maximum Concentration : 20 µg Se/L • Chronic-Criterion Continuous Concentration : 5 µg Se/L • California Saltwater numeric criteria: • Acute -Criterion Maximum Concentration : 290 µg Se/L • Chronic-Criterion Continuous Concentration : 71 µg Se/L Selenium does NOT exceed the CTR chronic criteria of 5 µg/L in North SFB

  6. Problem to Solve • 303(d) listing: • Affected use is one branch of the food chain most sensitive indicator is hatchability in nesting diving birds • exotic species may have made food chain more susceptible to accumulation of selenium • health consumption advisory in effect for scaup and scoter (diving ducks) • Se concentrations in benthic invertebrate, fish, and bird tissue collected from the Bay have been measured at concentrations known to cause reproductive and toxicological effects in some species

  7. Harmful versus Beneficial Adapted from NRC 2005

  8. Where Does Se Come From? • Volcanic deposits • Mining (copper, phosphate, coal) • Oil production and refining • By-product of coal burning power plants • Food (plant foods, grains, cereals and nuts) National Institutes of Health 2004

  9. Water versus Dietary Exposure • Water column Se has marginal impact on toxicity to higher level aquatic organisms • Observed selenium toxicity in fish results predominantly from dietary intake • Type of diet contributes to exposure and vulnerability • Filter-feeding benthic organisms ingest and assimilate particulate selenium to high concentrations • Bioaccumulation by invertebrates (zooplankton and bivalves) is critical to fish and birds

  10. It’s better to be a shrimp! Not All Food Webs Are Equal Terri Reeder, Selenium Game , San Diego 2005

  11. Clams Have Lower Loss Rates Than Crustaceans

  12. What Do They Have in Common?

  13. Target Development Approach • Review of fish and avian selenium toxicity • 80 fish toxicity studies (1987 -2007) • 46 avian toxicity studies • Identify species of concern in North SFB • Establish species-specific toxicity thresholds • Consider mitigating factors (diet, length of exposure, sulfate content, loss rates) • Compare with known effect levels

  14. Toxicity Thresholds in Birds • No direct toxicity information for birds in North SFB • Most data for chickens and mallards • Sensitive endpoint: -reproductive success • egg hatchability • egg fertility • chick survival

  15. Diving Ducks Exposure in NSFB • Feeding pattern - benthic mollusks, shellfish, crustaceans • Clams in scoter diet (SB = 100%, SPB = 25%) • Spend winter in SFB • Breed in Alaska and Canada • Rapid elimination rates – background levels after 70 days • New data: Se in eggs of scoters from NSFB below levels of concern for sensitive species • No reproductive effects for muscle tissue concentrations (2.1 – 5.7µg/g-ww, Lemly 1998)

  16. Toxicity Thresholds in Fish

  17. White Sturgeon • Identified as likely the most affected species in NSFB • Feeding pattern - benthic organisms • Clam eater (77% of stomach volume) • Present year-round in NSFB • Reproductive biology may contribute to bioaccumulation • Highly variable bioaccumulation rates • Toxicity data available • Tissue concentrations exceed known thresholds After W. Beckon, pers. com

  18. Sacramento Splittail • Potentially affected fish in North SFB • Feeding patterns - benthic organisms • Clam eater (34% of stomach volume) • Spawns in the upper Estuary • Can cope with high-level short-term exposure • Rapid elimination rates • Tissue concentrations below known thresholds and indicative of background level diet

  19. Fish Exposure in NSFB

  20. Fish-Tissue Target – Why & How? • 2004 EPA draft aquatic life criteria – fish tissue • Fish considered to be the most sensitive to chronic selenium exposure • Accounts for protection of wildlife from the harmful effects of selenium • Expressed as whole-body tissue concentration on a dry weight basis • Offers direct link to chronic endpoints and • Integrates many site-specific factors (chemical speciation, rates of transformation, temporal variations) • Easy to sample

  21. Numeric Target Derivation • Toxicity thresholds • For sensitive environments numeric target should be more protective than EC10 • Geometric mean of boundary concentrations

  22. Numeric Target Rationale Fish-tissue – 6 µg/g whole body dry weight • Proposed numeric target: • Established for species most at risk in North SFB and based on local data • Waterfowl depurates Se quickly after leaving the Bay • Se concentrations in bird eggs at background levels • Clam-eating bottom feeders - white sturgeon - most at risk • Within range of known thresholds protective of aquatic wildlife • Conservative and considers mitigating conditions in North SFB • Protective of human health (fish consumption)

  23. Human Health • Fish Contaminant Goal (OEHHA 2008) Tissue Concentration (ppb) = [(RfD * Body Weight)–BDL]/CR = 7.4 ppm ww (29.6 ppm dw) • Allowable duck tissue consumption • Original health advisory still in place • Scaup and scoter tissue concentrations < 6ppm ww

  24. QUESTIONS

  25. Screening of Available Studies • NOAEL and/or LOAEL reported • chronic exposure tested • selenium exposure was the only treatment • tissue data reported • laboratory experiments under controlled conditions • dietary exposure scenario used

  26. How our Numeric Target Compares with Known Thresholds? a – Compiled from Presser and Luoma, 2006 (Table 13, 14 and 15) b – Lemly (1998) (Table 1), values represent measured concentrations showing whether adverse effects are likely to occur c – Values in parenthesis indicate concentrations typical for uncontaminated aquatic systems

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