Presentation on theme: "Dioxins (PCDD/Fs) in San Francisco Estuary Mike Connor, Donald Yee, Jay Davis, Christine Werme RMP Annual Meeting May 2004."— Presentation transcript:
Dioxins (PCDD/Fs) in San Francisco Estuary Mike Connor, Donald Yee, Jay Davis, Christine Werme RMP Annual Meeting May 2004
Dioxins- Background Polychlorinated dibenzo dioxins and furans (PCDD/Fs) –Toxic compounds w/ 4 (TCDD/F) to 8 (OCDD/F) chlorines –2,3,7,8 TCDD toxicity equivalent factors (TEQs) –Toxicity TCDD/F >> OCDD/F –Concentrations TCDD/F << OCDD/F –Concentrations often near detection limits –Data less abundant than other pollutants PCBs w/ TEQs addressed in PCB conceptual model
Dioxins- Available Data Analytical Issues Concentrations not detected (water, sediment) –ND = 0 (optimist) or ND = MDL (pessimist) –TCDD/F and other more toxic dioxins less abundant –NDs = (possible large) impact on TEQs Temporal and spatial variability –NOAA-EMAP sediment site replicates > 10x differences –Refinery effluent 10xincrease sample size – 2x decrease in average concentration and variability (RSD%)
Dioxins- Sources Combustion by-products –Yard waste, wood, vehicle fuel, municipal and medical incineration Chlorine process by-products –Pesticides, wood pulp bleaching, PVC Dioxins have legacy component, but also Ongoing point/disperse sources (USEPA national inventory) –1987: Incineration > smelting > yard burning > pulp bleaching –2002: Yard burning > home fireplace ~coal burning ~ sludge (land) > diesel ~ 2,4-D (land)
Dioxins- Information Gaps Better quantitative data –Improvements in analyses and extent of data Prioritizing (given high analytical costs) –Monitoring biological receptors Most direct relationship to impacts Spatial and time integrators –Largest loads and reservoirs Rivers and tributaries (conveying current and legacy deposits) Sediment deposit profiles (history and distribution)
Dioxins- Management Options, Long Term Prospects Easier steps taken possible even w/o further information (addressing other issues): –Fish consumption advisories (PCBs, Hg) –Restrictions on yard burning (general air quality) –Wood-burning advisories, construction/remodel restrictions Harder steps (needing better information to prioritize) –Addressing watershed and in-bay legacy –Have past and current changes had impact?