Maryland Perspectives on Mercury in Fish Tissue & Advisory Issues

CBP

Toxics Subcommittee

01/14/05

                                                 

Outline• Sampling Stations

• Overview of Tissue Concentrations

• Overview of Risk Assessment/Advisory

• Discussion

FRESHWATER

Piney Run Reservoir

Lake Lariat

Spring Gap

Total Mercury in Largemouth Bass and Bluegill

• Trophic Level 4 (Large and Smallmouth Bass)

• Found in freshwater impoundments, larger freshwater stream segments, and tidal fresh portions of Bay tributaries

• Samples consist of individual and composite samples that are legal size

Methylmercury Levels in Bass and Bluegill From Western Maryland Lakes

0

250

500

750

1000

FrostburgReservoir

Savage R.Reservoir

PotomacRiver Dam

#4

Big Pool(Potomac

River)

Deep,CreekLake

BroadfordLake

LakeHabeeb

Lake/Reservoir

Mer

cury

Co

nce

ntr

atio

n (

pp

b)

Large/Smallmouth Bass

Bluegill

EPA Fish Tissu e Criterion = 300 ppb

MDE Hg Advisory Screening Level = 32 ppb

Methylmercury Levels in Bass and Bluegill From Central Maryland Lakes

0

250

500

750

1000

Prettyboy LochRaven

Liberty Duckett Clopper Tridelphia Piney Run

Lake/Reservoir

Mer

cury

Con

cent

ratio

n (p

pb)

Largemouth

Bluegill

Methylmercury Levels in Bass and Bluegills in Coastal Plain Lakes

0

250

500

750

1000

Lake Lariet St Marys Lake Tuckahoe Lake Johnsons Pond Conowingo Dam

Lake/Reservoir

Me

rcu

ry C

on

ce

ntr

ati

on

(p

pb

)

Largemouth Bass

Bluegill

Black Bass (Freshwater): Summary• Summary Statistics

– Total # of analytical samples 255• DNR = 255• MDE = 0

– Overall Average = 305 ± 255 ppb– Average Statewide Advisory Lakes = 242 ± 151 ppb– Average High Mercury Lakes = 688 ± 391 ppb– MDE Data Only (2002, 2003) = 106 ± 82 ppb

• Concentration Range – Statewide Advisory Lakes (31-656 ppb)– High Mercury Lakes (174-2076 ppb)

• Advisory Levels– Total # samples > FDA Action Level = 3– SA Total # samples > EPA Tissue Criterion = 45/255 (17.6%)– HM Total # samples > EPA Tissue Criterion = 27/30 (90%)

Freshwater Species Management Implications based on Mercury

• Statewide Consumption Advisory was necessary– Tier 1 Statewide

• General Population = 4 meals per month• Women of Child-bearing age = 4 meals per month• Children 0-6 = 2 Meals per month

– Tier 2 =High Mercury Lakes• General Population = 1 meal per month• Women of Child-bearing age = 1meal per month• Children 0-6 = No consumption

• TMDLs have been developed for 9 impoundments– Models available during development indicated > 90 reduction

from air sources– TMDLs may be refined as more data and better models

become available – EPA requirement for review every 5 years

Chesapeake Bay and Tributaries

White Perch• Trophic Level 3

gamefish• Semi-anadromous –

tributary fidelity – representative of local conditions (PCBs – King et.al. 2004)

• Samples consist of composites of fish of harvestable size (BPJ – since no legal slot limit exists)

White Perch Sample LocationsChesapeake Bay Tributaries

BayTributaries

SampledSassafrass R.

Chester R.Choptank R. Nanticoke R.Pocomoke R.Patapsco R. Severn R.

Rhode/West R.

White Perch Summary• Summary Statistics

– Total # of analytical samples 19 composites (94 fish)– Average = 30 ± 20 ppb

• Concentration Range – Overall (5 ppb [Elk R.] – 84 ppb [Patapsco R.])

• Advisory Levels– 7/19 Composites exceeded minimal screening

threshold (32 ppb – lower threshold for children 0-6 @ 8 meals per month), BUT

– No advisories exist for white perch due to mercury since all tributaries are impacted by PCBs (risk driver)

Striped Bass (Rockfish)

• Trophic Level 4 (top predator)

• Migratory (resident until about age 7); sometimes males do not join Coastal migratory cohort

• Samples consist of individuals of appropriate slot limit based on DNR regulations

= Core Station= Core Station > Screening Values

= Intensive Survey Station= Intensive Survey Station > Screening Values

S

N

EW

3.13 Sample Station Locations Chesapeake Bay Mainstem Area (02-13-99)

0 10 20 30 40 Miles

#

#

##

#

#S

#SXGF3973

XFE1292

XFF2584

#

XHG0819

#

XHG9820#

XIG4260#

XIG7926

Chesapeake Bay Mainstem

#S#S

%

%

#S

#S

#S

#S

#S#S #S

#XEA1130

XDA8825

#XEA6596

XDC1706

XDA6140

XDA1177

XDB3321

XDB3499

XCC6634

XBE9541

XBF3534

Potomac RiverSt-Mary's River

Wicomico River

Mattawoman Creek

Port Tobbaco River

S

N

EW

3.14 Sample Station Locations Lower Potomac River Basin Area (02-14-01)

= Core Station= Core Station > Screening Values

= Intensive Survey Station= Intensive Survey Station > Screening Values

0 4 8 12 16 Miles

Mean Total Hg in Rockfish Chesapeake Bay & Potomac River

239

182

66

158

221

79

144112

39 50

155

0

100

200

300

400

500

Me

rcu

ry C

on

cen

trat

ion

(pp

b)

EPA (MD) Fish Tissue Criteria for Mercury = 300 ppb

MDE Lower threshold for 1 meal per month = 469 ppb (children = 269 ppb)

Striped Bass: Individual Hg Tissue Concentrations

0

100

200

300

400

500

600

700

800

900

1000

0 200 400 600 800

Mer

cury

Con

cent

ratio

n (p

pb)

Potomac R. S1. 2002

Potomac R.S2 2002

Potomac R. S2 2003

Bay Zone 1 1994

Bay Zone 1 2002

Bay Zone 2 1992

Bay Zone 2 2002

Bay Zone 2 2003

Bay Zone 3 S1 2003

Bay Zone 3 S2 2003

FDA Action Level = 1000 ppb (Above)EPA Tissue Criterion = 300 ppb (Below)

Striped Bass: Summary• Summary Statistics

– Total # of analytical samples 129• DNR ANSERC = 42• MDE = 87

– Overall Average MDE & DNR samples combined = 137 ± 109 ppb

– MDE Data Only (2002, 2003) = 106 ± 82 ppb

• Concentration Range – Overall (15-607 ppb)– MDE Data Only –2002 & 2003 = (15-429)

• Advisory Levels– Total # samples > FDA Action Level = 0– Total # samples > EPA Tissue Criterion = 8/129– Number of pre-2000 samples > EPA Tissue Criterion = 6– Number of 2002-03 samples > EPA Tissue Criterion = 2

Risk Assessment Equation

• [Fish Tissue] = RfD x BW x T MS X NM

Recommended Consumption Allowance MD Freshwater Fish

•   

0

1

2

4

8

Unlimited

Allowable Meals per Month

Population Exposure Designation

Children 0-6Women (15-45)General AdultHg Range Hg Range Hg Range

> 939 ppb > 858 ppb > 518 ppb

469 - 939 ppb 429 - 858 ppb 259 - 518 ppb

234 - 469 ppb 214 - 429 ppb 130 - 259 ppb

118 - 234 ppb 107 - 214 ppb 65 - 130 ppb

59 - 118 ppb 53 - 107 ppb 32 - 65 ppb

< 59 ppb < 53 ppb < 32 ppb

Striped Bass Management Implications Based on Mercury

• No advisory for mercury in rockfish, since current risk driver for striped bass advisory is PCBs

• If PCBs were not present, the following advisory scenario would apply based on an average of 106 ppb:– General Population (8 oz meal): 8 meals/month

– Women of Child Bearing Age (6 oz meal): 8 meals/month

– Children ages 0-6 (3 oz meal): 4 meals/month

• Also, since the average mercury concentration is below 300 ppb (mean = 106 ppb), the Chesapeake Bay is not required to be listed for mercury as an impairing substance under Section 303(d) CWA.

Questions??

Data Summary: All Lakes

• Largemouth Bass MeHg Concentration (By Length)– N = 204 Geometric Mean 12” (305 mm) = 148 ppb

– 12” – 14” (306- 350 mm) = 175 ppb

– 14-16” (351- 400 mm) = 218 ppb

– 16-18” (401- 450 mm) = 288 ppb 18” (451 – 541 mm) = 608 ppb

Data Summary: Tier 1 Lakes

• Largemouth Bass MeHg Concentration (By Length)– N = 171 Geometric Mean 12” (305 mm) = 75 ppb

– 12” – 14” (306- 350 mm) = 147 ppb

– 14-16” (351- 400 mm) = 187 ppb

– 16-18” (401- 450 mm) = 261 ppb 18” (451 – 506 mm) = 421 ppb

NOTE: Relationship does not persist for high Hg lakes

Largemouth Bass Length vs [MeHg]Tier I Lakes

200

300

400

500

600

0 100 200 300 400 500 600 700 800 900 1000

Tissue MeHg (ppb)

Fis

h L

en

gth

(m

m)

y = .1570x + 337

r2 = 0.526N = 231

Data Summary: Tier 2 Lakes

• Largemouth Bass MeHg Concentration (By Length)– N = 30 Geometric Mean 12” (305 mm) = 360 ppb (n = 3)

– 12” – 14” (306- 350 mm) = 433 ppb (n = 9)

– 14-16” (351- 400 mm) = 719 ppb (n = 9)

– 16-18” (401- 450 mm) = 564 ppb (n = 6) 18” (451 – 541 mm) = 1191 ppb (n = 4)

Largemouth Bass Length vs [MeHg]Tier II (High Hg) Lakes

100

200

300

400

500

600

700

0 250 500 750 1000 1250 1500 1750 2000 2250

MeHg (ppb)

Fish

Len

gth

(mm

)

y = 0.1426 + 277

r2 = 0.724N = 54