1. SOURCE ATTRIBUTION OF MERCURY EXPOSURE FOR U.S. SEAFOOD CONSUMERS: IMPLICATIONS FOR POLICY Noelle Eckley Selin Joint Program on the Science and Policy of Global Change Center for Global Change Science Massachusetts Institute of Technology AGU Fall Meeting 19 December 2008 Coauthors: E. M. Sunderland (Harvard), C. D. Knightes, (U.S. EPA), R. P. Mason (U. Conn.), S. Paltsev (MIT), J. M. Reilly (MIT), R. G. Prinn (MIT)

2. 20% 16% Atmosphere [GEOS-Chem, Selin and Jacob, 2008] Watershed/ Water body [Knightes et al., in press] 3. Local exposure 4. Population- wide exposure 5. Economic implications [MIT EPPA model, Paltsev et al. 2006] Marine pathway Freshwater pathway HOW DO POLICIES AFFECT EXPOSURE? Ocean dynamics [Sunderland and Mason, 2007] 2. Policy and Timescale Analysis 1. Deposition and source attribution

3. MODELS (1): ATMOSPHERE (GEOS-Chem) [Selin et al., 2008; Selin and Jacob, 2008] Global, 3D tropospheric chemistry model simulation, 4x5 degree resolution, assimilated meteorology [Bey et al., 2001] Provides wet and dry deposition (present-day) from: Natural sources (pre-industrial simulation) North American anthropogenic sources International anthropogenic sources Historical anthropogenic sources (“Legacy” mercury revolatilized from surface reservoirs) 1/3

4. MODELS(2):WATERSHED/WATER BODY [Knightes et al., in press] SERAFM: Lake model WASP7: River model WCS (MLM): Watershed loading BASS: Aquatic food web Models available from EPA (Athens)

5. MODELS (3): OCEAN DYNAMICS EVASION ATMOSPHERIC DEPOSITION RIVERS LATERAL OCEAN FLOW RESERVOIR M w = C w V w MARINE BOUNDARY LAYER C air DEEP WATER FORMATION PARTICLE SETTLING kvkv k O1 k O2 kpkp [Sunderland and Mason, 2007] 14 ocean basins (North Atlantic, Surface Atlantic, Mediterranean, North Pacific, etc.)

6. 1. DEPOSITION AND SOURCE ATTRIBUTION (FRESHWATER) % Deposition from North American sources [Selin and Jacob, 2008] NE Total: 24.21  g m -2 y -1 SE Total: 34.08  g m -2 y -1 Pre-industrial + Historical International Anthropogenic N. American Anthropogenic 11% 23% 66% 59% 9% 32% Two freshwater deposition scenarios: “Northeast” and “Southeast” U.S.

7. 2. POLICY & TIMESCALE ANALYSIS (FRESHWATER) Fish MeHg (ppm) Same deposition,but different ecosystem dynamics lead to very different source attributions (and concentrations) over time Regional differences in deposition sources lead to different attributions in similar ecosystems Watershed/water body models: Knightes et al., in press; source attribution, Selin et al. in prep Note difference in scale! Each ecosystem driven by present-day deposition for 40 years (10-year spin up) Policy experiment: All Hg is “historical” at t=0. How is anthropogenic signal reflected in fish, and on what timescale?

8. 3. LOCAL EXPOSURE (FRESHWATER) 2 x 100 g fish meals/week (60 kg person) @ t=40 y Northeast DepositionSoutheast Deposition 6.4 WHO intake threshold EPA Reference Dose North American anthropogenic Historical+Natural International anthropogenic

9. 4. POPULATION-WIDE EXPOSURE (MARINE) Calculate exposure from each basin from commercial market statistics Historical exposure is continuing to increase, complicating policy decision-making “current emissions” scenario 14-box model: Sunderland and Mason, 2007; exposure by basin, Sunderland et al. in prep; Source attributions/exposure index: Selin et al., in prep

10. 5. ECONOMIC IMPLICATIONS (MARINE) MIT Emissions Prediction and Policy Analysis (EPPA) model IQ deficits from mercury exposure [Axelrad, 2007] cost 2.5% of income per point lost [Salkever, 1995] Calculate additional cost of US emissions for general population (marine) exposure beginning in 2000 Methodology takes into account “indirect” costs of lost investment/savings Other estimates: $1.3b for US power plants alone (Trasande et al., 2005); $119m-4.9b (Rice et al. 2005)