1. Chronic Estuarine & Marine Silver Toxicity: Water Quality Parameters as Modifying Factors T.J. Ward, R.L. Boeri T.R. Wilbury Laboratories C. Hogstrand King’s College London J.R. Kramer McMaster University S.M. Lussier U.S. EPA W.A. Stubblefield ENSR Corporation J.W. Gorsuch Eastman Kodak Company

2. Development of Chronic Toxicity Data Current Silver Water Quality Criteria  Freshwater Acute Toxicity 3.43 µg/L  Saltwater Acute Toxicity 1.92 µg/L  Freshwater Chronic Toxicity none  Saltwater Chronic Toxicity none

3. Development of Chronic Toxicity Data Water Quality Parameters as Modifiers  Chloride  Critical importance in estuarine/marine systems  Dissolved organic matter and sulfides  Natural organic matter from freshwater source  Sulfides may only be important near POTW outfalls in the mixing zone (salinity <10 ppt)

4. Survival of Mysids, Americamysis bahia, Exposed to Silver Nitrate for 96 Hours

5. Effect of Salinity on the Acute Toxicity of Silver to Americamysis bahia

6. Project Goals Estuarine/Marine Toxicity  develop chronic toxicity data  examine the effect of water quality parameters on toxicity  determine free ionic silver concentrations  direct measurement  calculation using chloride and dissolved silver

7. Chronic Toxicity Testing Standard 28-day mysid chronic toxicity test  Mysid, Americamysis bahia  Survival, growth, and reproduction endpoints  Stable water quality: salinity, temperature, pH  Low dissolved organic matter  Minimized loss of silver to container walls

8. Chronic Toxicity Testing 7-day mysid chronic estimation toxicity test  Mysid, Americamysis bahia  Initiated with 7-day old mysids  survival, growth, and reproduction endpoints  Initiated with <24-hour old mysids  survival and growth endpoints

9. Chronic Toxicity Test Results Salinity during this test was 20 ppt.

10. 28-Day Chronic Toxicity Test Results Salinity during this test was 20 ppt.

11. Conclusions 7-day chronic estimation toxicity tests with mysids and silver accurately predict 28-day chronic toxicity based on the most sensitive endpoint in each test Direct measurement of free ionic silver is possible during laboratory toxicity tests in seawater.

12. Conclusions NOEC determined from the chronic mysid toxicity test performed in seawater adjusted to a salinity of 20 ppt was 36 ug/L, based on dissolved silver concentrations.  Dissolved silver concentrations in coastal waters are reportedly below 0.0039 ug/L Acute silver toxicity decreases significantly as salinity increases during mysid toxicity tests

13. Future Research Verify the ability of 7-day chronic estimation toxicity tests with Menidia beryllina, an estuarine/marine fish, to accurately predict chronic (early life stage) toxicity Conduct 7-day toxicity tests with mysids and fish in water over a range of salinity and dissolved organic matter combinations Measure free ionic silver in all toxicity tests