1. Human Health 2 Establishing Thresholds

3. Establishing Water Quality Thresholds (Q1) Process Persistence (Fate and Transport) Occurrence Data (inc. degradates) Analytical Methods Toxicology Studies Exposure Assessment Epi Studies THRESHOLD (Health Reference Level) Uncertainty Temporal Risk Communication

4. Thresholds Depend Upon Exposure (Q2) Indirect Potable Reuse - Groundwater IPR - Surface Water Augmentation Surface Water Discharge –Downstream Drinking Water –Bioaccumulation Non-potable Reuse Ocean Desalination b

5. What Process For Establishing Water Quality Thresholds DLRHRL (PHG) DLR<PHG Set PHG DLR<PHG Set DLR Communicate RIsk b

6. Thresholds Depend Upon Exposure (Q2) Indirect Potable Reuse - Groundwater IPR - Surface Water Augmentation Surface Water Discharge –Downstream Drinking Water –Bioaccumulation Non-potable Reuse Ocean Desalination b

7. Temporal Issues (Q2&Q3) Acute Exposure vs. Chronic Exposure – compound specific May have acute and chronic criteria Acute criteria will drive monitoring frequency b

8. Ongoing Projects Doing This Already WRF/WRF Toxicological Relevance (05-005) WRF Research Needs (Cotruvo/Bull) WRF IEUA Health Based (Nellor) Intertox Tox Relevance (WRF) NRC Panel

9. There are Known Knowns and Unknown Knowns Uncertainty & Conservatism = f(lack of information)

10. Uncertainty Drives Threshold Conservatism (Q4) b Standard EPA Uncertainty Factors Can be Applied to Balance Lack of Data

11. Risk Communication Uncertainty is Reality Other Routes of Exposure? Open Discussion with the Public Work to Fix Problem …try to avoid these issues through intermediate monitoring

12. What if You Exceed HRL? Retest, split samples, document outlier or repeated event. Running averages to document risk –acute versus chronic