maryland perspectives on mercury in fish tissue & advisory issues
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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
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