SOURCE ATTRIBUTION OF MERCURY EXPOSURE FOR U.S. SEAFOOD

CONSUMERS: IMPLICATIONS FOR POLICY

Noelle Eckley SelinJoint 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)

20% 16%

Atmosphere[GEOS-Chem, Selin and Jacob, 2008]

Watershed/Water body

[Knightes et al., in press]

3. Local exposure 4. Population-wide exposure5. Economic

implications[MIT EPPA model, Paltsev et al. 2006]

Marine pathwayFreshwater pathway

HOW DO POLICIES AFFECT EXPOSURE?

Ocean dynamics[Sunderland and

Mason, 2007]2. Policy and Timescale Analysis

1. Deposition and source attribution

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 sourcesInternational anthropogenic sources

Historical anthropogenic sources (“Legacy” mercury revolatilized from surface reservoirs)

1/3

1/3

1/3

MODELS(2):WATERSHED/WATER BODY

[Knightes et al., in press]

SERAFM: Lake model WASP7: River modelWCS (MLM): Watershed loading BASS: Aquatic food web

Models available from EPA (Athens)

MODELS (3): OCEAN DYNAMICS

EVASIONATMOSPHERIC DEPOSITION

RIVERS

LATERAL OCEAN FLOW

RESERVOIR Mw = CwVw

MARINE BOUNDARY LAYERCair

DEEP WATER FORMATION

PARTICLESETTLING

kv

kO1

kO2

kp

[Sunderland and Mason, 2007]

14 ocean basins (North Atlantic, Surface Atlantic, Mediterranean, North Pacific, etc.)

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

InternationalAnthropogenic

N. AmericanAnthropogenic

11%

23%

66%

59%

9%

32%

Two freshwater deposition scenarios: “Northeast” and “Southeast” U.S.

2. POLICY & TIMESCALE ANALYSIS (FRESHWATER)F

ish

MeH

g (p

pm)

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?

3. LOCAL EXPOSURE (FRESHWATER)2 x 100 g fish meals/week (60 kg person) @ t=40 y

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Stratified Seepage Stratified Seepage

MeHg intake (ug/kg/day)

Northeast Deposition Southeast Deposition

6.4

WHO intake threshold

EPA Reference Dose

North American anthropogenic

Historical+NaturalInternational anthropogenic

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

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

00.5

11.5

22.5

33.5

44.5

5

2000 2020 2040 2060 2080 2100

Cost ($billion)

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)