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- National Source Trends

1

10

100

1000

10000

100000

1987 1995 2002 2010

Year

g T

EQ

/yr

nonpoint

point

Dioxin- Fish Tissue Concentrations

Impacted Organisms

Ecosystem Transfers

??

?

?

Loss Pathways

?

?

?

??

??

Sources and Loading Pathways

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?