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PUBLIC HEALTH ASSESSMENT

LOWER DUWAMISH WATERWAY
SEATTLE, KING COUNTY, WASHINGTON


APPENDIX C: EXPOSURE ASSUMPTIONS

This section provides calculated exposure doses and assumptions used for each completed exposure pathway. The dose estimates for each pathway are discussed under the Pathways Analysis/Public Health Implications section. The following exposure parameters and dose equations were used to estimate exposure from fish consumption and direct contact with sediments at the LDW site.

Fish Consumption

Average and upper-bound exposure scenarios were evaluated for consumption of fish from the LDW site. Because site-specific consumption rates for fish caught from the LDW study area were lacking, surrogate rates were taken from a recent survey of the Suquamish Tribe using data gathered from fish consumers only, and a study of recreational anglers in urban embayments of Puget Sound. Exposure assumptions given in Table C1 below were used with Equations C1 and C2 to estimate contaminant doses associated with fish consumption.

Dose sub non-cancer (mg/kg day) equals C times CF sub 1 times IR times CF sub 2 times EF times ED divided by AT sub non-cancer

Dose sub cancer (mg/kg day) equals C times CF sub 1 times IR times CF sub 2 times EF times ED divided by AT sub cancer

Table C1.

Exposure assumptions used to estimate contaminant doses from consumption of fish from the Lower Duwamish Waterway, Seattle, Washington
Parameter Value Units Comments
Average High-end
Concentration (C) Species specific ug/kg See Table C2. Below.
Conversion Factor1 (CF1) 0.001 0.001 mg/ug Converts concentration from
Ingestion Rate (IR) - English Sole 0.08 a 0.201 g/kg/day a = Recreational rates from Landolt et al assuming fishing season of 120 days for salmon and 183 days for other species. Remaining average ingestion rates based on median rates from the Suquamish Tribe.

High-end based on 90th percentile rates from the Suquamish Tribe fish consumers.

Ingestion Rate (IR) - Coho 0.15 a 0.584
Ingestion Rate (IR) - Chinook 0.25 a 0.581
Ingestion Rate (IR) - All rockfish 0.12a 0.728
Ingestion Rate (IR) - Red Rock Crab 0.012 0.117
Ingestion Rate (IR) - Dungeness Crab 0.071 0.425
Ingestion Rate (IR) - Mussels 0.015 0.155
Ingestion Rate (IR) - Perch 0.26 a 0.014
Conversion Factor (CF2) 0.001 0.001 kg/g Converts mass of fish from grams (g) to kilograms (kg)
Exposure Frequency (EF) 365 365 days/year Assumes daily exposure consistent with units of ingestion rate given in g/kg/day.
Exposure Duration (ED) 30 55 years Estimates of residence time.
Averaging Timenon-cancer (AT) 10950 20075 days Residence time in years
Averaging Timecancer (AT) 25550 25550 days 70 year lifetime

a = consumption rates from Landolt et al were reported as g/day during the fishing season. A body weight of 72 kg was used to convert the units to g/kg/day.

Contaminant concentrations used to estimate exposure to contaminants in Duwamish River fish are given below in Table C2. These concentrations are based on data compiled from various sources as part of the scoping-phase risk assessment in preparation for the Remedial Investigation. For finfish, only data generated from analysis of fillets without skin were used. Crab data included analytical results from muscle tissue only.

A majority of the finfish samples were analyzed as composite samples meaning that several fish were collected and blended together in order to obtain an approximation of the mean contaminant concentration in a group of fish. This method reduces the cost of environmental analyses, but decreases the knowledge about the variability of contaminant levels in a fish population. This health assessment relied on both composite and individual samples. As a result, a weighting method was used to calculate mean contaminant concentrations in finfish. Estimates of variance around the mean were also calculated in order to estimate confidence intervals around the mean. The equations and examples are shown below.

Weighted mean (grouped mean)

mathematical equation

The weighted mean is equal to the sum of composite sample concentration times the number of fish per composite divided by the sum of fish per composite in all samples.

For example:

The weighted mean concentration of the following data set is shown below.

The weighted mean concentration of the following data set is shown below.
Sample Fish per composite Concentration
1 2 100
2 8 52
3 10 48

Weighted mean concentration
= ( 2*100 + 8*52 + 10*48) / 20
= 54.8

Grouped Variance

mathematical equation

Using the above example

Grouped variance ={ (2*(100)2 + 8*(52)2 + 10*(48)2) - (((2*100)2 + (8*52)2 + (10*48)2 )/20)}/19

The 95 UCL was calculated for groups of composited fish samples using the weighted mean and the grouped variance. In general, composite sampling is designed to get a better approximation of the mean, therefore, the 95 UCL was not much greater than the weighted mean.

Table C2.

Contaminant concentrations used to estimate exposure from consumption of fish from the Lower Duwamish Waterway, Seattle, Washington
Fish Species Arsenic a
(mg/kg)
Cadmium
(mg/kg)
Chlordane
(ug/kg)
cPAHs
(ug/kg)
DDE
(ug/kg)
Mercury c
(ug/kg)
Total PCBs
b(ug/kg)
Mean 95 UCL n Mean 95 UCL n Mean 95 UCL n Mean 95 UCL n Mean 95 UCL n Mean 95 UCL n Mean 95 UCL n
English sole 10 12 9 0.02 0.05 3 1.1 1.3 9 26 41 6 2.7 5.9 9 54 61 24 267 312 21
Coho 0.8 0.9 18 NA NA NA 0.9 1.1 57 42 45 16 8.3 9 57 32 37 16 39 45 45
Chinook 1 1.2 18 NA NA NA 1.2 1.3 83 41 44 19 19 22 83 102 124 18 55 64 65
Quillback rockfish NA NA NA NA NA NA NA NA NA NA NA NA 0.04 0.04 1 408 438 8 292 336 5
Red Rock Crab NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 63 88 9 110 152 9
Dungeness Crab f 9.9 12.5 f 2 0.02 0.02 2 NA NA NA 40 40 2 NA NA NA 90 110 3 130 177 3
Mussels 0.8 0.9 63 0.43 0.47 63 3.4 27 42 43 62 0.7 0.7 27 11 15 62 29 34 60
Perch g 1.3 1.4 f 3 NA NA NA NA NA NA NA NA NA NA NA NA 15 20 9 111 140 9

a = Arsenic concentrations are given as total arsenic. Ten percent of this value was used in dose calculations to represent the amount of inorganic arsenic to be consistent with EPA's RfD and cancer slope factor both of which are based on exposure to inorganic arsenic.
b = Sum of Aroclors. The predominant Aroclors detected in Puget Sound fish are Aroclor 1254 and Arolcor-1260
c = Mercury concentrations are given as total mercury. All measured mercury is assumed to in the methylmercury form for comparison with EPA's RfD for methylmercury.
f = Represents maximum value detected.
g = striped perch


Table C3.

Noncancer dose calculations for consumption of fish from the Lower Duwamish Waterway, Seattle, Washington
Receptor Population Fish Species Contaminant Concentration Estimated Dose (mg/kg-day) RfD
(mg/kg-day)
Hazard Quotient
Average High-end Average High-end Average High-end
Fish Consumers English Sole Arsenic 10 12 8e-05 2e-04 3e-04 0.3 0.8
Cadmium 0.02 0.05 2e-09 1e-08 1e-03 2e-06 1e-05
Chlordane 1.1 1.3 9e-08 3e-07 5e-04 2e-04 5e-04
Total PCBs 267 312 2e-05 6e-05 2e-05 1.1 3.1
Mercury 54 61 4e-06 1e-05 1e-04 0.04 0.1

Hazard Index

1.4 4.1
Chinook Salmon (King) Arsenic 1 1.2 3e-05 7e-05 3e-04 0.1 0.2
Cadmium NA NA NA NA 1e-03 NA NA
Chlordane 1.2 1.3 3e-07 8e-07 5e-04 6e-04 2e-03
Total PCBs 55 64 1e-05 4e-05 2e-05 0.7 1.9
Mercury 102 124 3e-05 7e-05 1e-04 0.3 0.7

Hazard Index1

1.0 2.8
Coho Salmon Arsenic 0.8 0.9 1e-05 5e-05 3e-04 0.04 0.2
Cadmium NA NA NA NA 1e-03 NA NA
Chlordane 1.1 1.3 1e-07 6e-07 5e-04 3e-04 1e-03
Total PCBs 39 45 6e-06 3e-05 2e-05 0.3 1.3
Mercury 32 37 5e-06 2e-05 1e-04 0.05 0.2

Hazard Index

0.4 1.7
Rockfish Arsenic NA NA NA NA 3e-04 NA NA
Cadmium NA NA NA NA 1e-03 NA NA
Chlordane NA NA NA NA 5e-04 NA NA
Total PCBs 292 336 4e-05 2e-04 2e-05 1.8 12.2
Mercury 408 438 5e-05 3e-04 1e-04 0.5 3.2

Hazard Index

2.3 15.4
Red Rock Crab Arsenic NA NA NA NA 3e-04 NA NA
Cadmium NA NA NA NA 1e-03 NA NA
Chlordane NA NA NA NA 5e-04 NA NA
Total PCBs 110 152 1e-06 2e-05 2e-05 0.1 0.9
Mercury 63 88 8e-07 1e-05 1e-04 1e-02 0.1

Hazard Index

0.1 1.0
Dungeness Crab Arsenic 9.9 12.5 7e-05 5e-04 3e-04 0.2 1.8
Cadmium 0.02 0.02 1e-09 9e-09 1e-03 1e-06 1e-05
Chlordane NA NA NA NA 5e-04 NA NA
Total PCBs 130 177 9e-06 7e-05 2e-05 0.5 3.8
Mercury 90 110 6e-06 5e-05 1e-04 0.1 0.5

Hazard Index

0.8 6.0
Mussels Arsenic 0.8 0.9 1e-06 1e-05 3e-04 4e-03 0.04
Cadmium 0.43 0.47 7e-09 7e-08 1e-03 1e-05 7e-05
Chlordane 3.4 3.4 5e-08 5e-07 5e-04 1e-04 1e-03
Total PCBs 29 34 4e-07 5e-06 2e-05 0.02 0.3
Mercury 11 15 2e-07 2e-06 1e-04 2e-03 0.02
Hazard Index 0.03 0.3
Perch Arsenic 1.3 1.4 3e-05 2e-06 3e-04 0.1 0.01
Cadmium NA NA NA NA 1e-03 NA NA
Chlordane NA NA NA NA 5e-04 NA NA
Total PCBs 111 140 3e-05 2e-06 2e-05 1.4 0.1
Mercury 15 20 4e-06 3e-07 1e-04 0.04 3e-03

Hazard Index

1.6

0.1

Note: Rounding of hazard quotients could impact the hazard index. Doses are reported in scientific notation format. For example, 1e-02 is the same as 1 x 10-2 or 0.01.


Table C4.

Cancer risk calculations for consumption of fish from the Lower Duwamish Waterway, Seattle, Washington
Receptor Population Fish Species Contaminant Concentration a Estimated Dose (mg/kg-day) Cancer Slope Factor
(mg/kg-day)-1
Cancer Risk
Average High-end Average High-end Average High-end
Fish Consumers English Sole Arsenic 10 12 3e-05 2e-04 1.5 5e-05 3e-04
cPAHs 26 41 9e-07 7e-06 7.3 7e-06 5e-05
Chlordane 1.1 1.3 4e-08 2e-07 0.35 1e-08 7e-08
DDE 2.7 5.9 9e-08 9e-07 0.34 3e-08 3e-07
Total PCBs 267 312 9e-06 5e-05 2 2e-05 1e-04
Sum of Cancer Risks 8e-05 4e-04
Chinook Salmon (King) Arsenic 1 1.2 1e-05 6e-05 1.5 2e-05 8e-05
cPAHs 41 44 4e-06 2e-05 7.3 3e-05 1e-04
Chlordane 1.2 1.3 1e-07 6e-07 0.35 5e-08 2e-07
DDE 19 22 4e-06 2e-05 0.34 2e-06 7e-06
Total PCBs 55 64 6e-06 3e-05 2 1e-05 6e-05
Sum of Cancer Risks 6e-05 3e-04
Coho Salmon Arsenic 0.8 0.9 5e-06 4e-05 1.5 7e-06 6e-05
cPAHs 42 45 3e-06 2e-05 7.3 2e-05 2e-04
Chlordane 0.9 1.1 6e-08 5e-07 0.35 2e-08 2e-07
DDE 8.3 9 5e-07 4e-06 0.34 2e-07 1e-06
Total PCBs 39 45 2e-06 2e-05 2 5e-06 4e-05
Sum of Cancer Risks 3e-05 3e-04
Rockfish Arsenic NA NA NA NA 1.5 NA NA
cPAHs NA NA NA NA 7.3 NA NA
Chlordane NA NA NA NA 0.35 NA NA
DDE 0.04 0.04 2e-09 2e-08 0.34 7e-10 8e-09
Total PCBs 292 336 2e-05 2e-04 2 3e-05 4e-04
Sum of Cancer Risks 3e-05 4e-04
Red Rock Crab Arsenic NA NA NA NA 1.5 NA NA
cPAHs NA NA NA NA 7.3 NA NA
Chlordane NA NA NA NA 0.35 NA NA
DDE NA NA NA NA 0.34 NA NA
Total PCBs 110 152 6e-07 1e-05 2 1e-06 3e-05
Sum of Cancer Risks 1e-06 3e-05
Dungeness Crab Arsenic 10 12.5 3e-05 4e-04 1.5 5e-05 6e-04
cPAHs 40 40 1e-06 1e-05 7.3 9e-06 1e-04
Chlordane NA NA NA NA 0.35 NA NA
DDE NA NA NA NA 0.34 NA NA
Total PCBs 130 177 4e-06 6e-05 2 8e-06 1e-04
Sum of Cancer Risks 6e-05 8e-04
Mussels Arsenic 0.8 0.9 5e-07 1e-05 1.5 8e-07 2e-05
cPAHs 42 43 3e-07 5e-06 7.3 2e-06 4e-05
Chlordane 3.4 3.4 2e-08 4e-07 0.35 8e-09 1e-07
DDE 0.7 0.7 5e-09 9e-08 0.34 2e-09 3e-08
Total PCBs 29 34 2e-07 4e-06 2 4e-07 8e-06
3e-06 6e-05
Perch Arsenic 1.3 1.4 1e-05 2e-06 1.5 2e-05 2e-06
cPAHs NA NA NA NA 7.3 NA NA
Chlordane NA NA NA NA 0.35 NA NA
DDE NA NA NA NA 0.34 NA NA
Total PCBs 111 140 1e-05 2e-06 2 2e-05 3e-06
5e-05 5e-06

a = Arsenic concentrations are given in units of mg/kg while PCB values are in ug/kg.
Note - Cancer risks are reported in scientific notation format. For example, 1e-02 is the same as 1 x 10-2 or 0.01.


Table C5.

Exposure assumptions used to estimate contaminant doses from consumption of fish groups from the Lower Duwamish Waterway, Seattle, Washington
Parameter Value Units Comments
Average API High-end
Concentration (C) Species specific ug/kg See Table C6. Below.
Conversion Factor1 (CF1) 0.001 0.001 0.001 mg/ug Converts concentration from
Ingestion Rate (IR) - Anadromous 0.35 0.509 1.68 g/kg/day Median and 90th percentile rates from the Suquamish Tribe and 90th percentile rates from Asian Pacific Islander Seafood Consumption Study
Ingestion Rate (IR) - Benthic 0.042 0.272 0.392
Ingestion Rate (IR) - Pelagic 0.068 0.829 0.403
Ingestion Rate (IR) - Shellfish 0.75 1.73 4.58
Conversion Factor (CF2) 0.001 0.001 0.001 kg/g Converts mass of fish from grams (g) to kilograms (kg)
Exposure Frequency (EF) 365 365 365 days/year Assumes daily exposure consistent with units of ingestion rate given in g/kg/day.
Exposure Duration (ED) 30 30 55 years Estimates of residence time.
Averaging Timenon-cancer (AT) 10950 10950 20075 days Residence time in days
Averaging Timecancer (AT) 25550 25550 25550 days 70 years


Table C6.

Noncancer dose calculations for consumption of fish groups from the Lower Duwamish Waterway, Seattle, Washington
Receptor Population Fish Group Contaminant Concentration Estimated Dose
(mg/kg-day)
RfD
(mg/kg-day)
Hazard Quotient
Average API High-end Average API High-end Average API High-end
Fish Consumers All Salmon Arsenic 1 1.2 1.2 4e-05 6e-05 2e-04 3e-04 0.1 0.2 0.7
Cadmium NA NA NA NA NA NA 1e-03 NA NA NA
Chlordane 1.2 1.3 1.3 4e-07 7e-07 2e-06 5e-04 8e-04 1e-03 4e-03
Total PCBs 55 64 64 2e-05 3e-05 1e-04 2e-05 1.0 1.6 5.4
Mercury 102 124 124 4e-05 6e-05 2e-04 1e-04 0.4 0.6 1.9

Hazard Index

1.4 2.4 8.0
Pelagic Arsenic 1.3 1.4 1.4 9e-06 1e-04 6e-05 3e-04 0.03 0.4 0.2
Cadmium NA NA NA NA NA NA 1e-03 NA NA NA
Chlordane NA NA NA NA NA NA 5e-04 NA NA NA
Total PCBs 111 140 140 8e-06 1e-04 6e-05 2e-05 0.4 5.8 2.8
Mercury 15 20 20 1e-06 2e-05 8e-06 1e-04 0.01 0.2 0.08

Hazard Index

0.4 6.4 3.1
Benthic Arsenic 10 12 12 4e-05 3e-04 5e-04 3e-04 0.1 0.9 1.6
Cadmium 0.02 0.05 0.05 8e-10 5e-09 2e-08 1e-03 1e-06 5e-06 2e-05
Chlordane 1.1 1.3 1.3 5e-08 3e-07 5e-07 5e-04 1e-04 6e-04 1e-03
Total PCBs 267 312 312 1e-05 9e-05 1e-04 2e-05 0.6 4.2 6.1
Mercury 54 61 61 2e-06 2e-05 2e-05 1e-04 0.02 0.15 0.2

Hazard Index

0.7 5.3 7.9
Shellfish Arsenic 0.8 0.9 0.9 6e-05 1e-04 4e-04 3e-04 0.2 0.5 1.3
Cadmium 0.43 0.47 0.47 3e-06 6e-06 2e-05 1e-03 5e-03 0.01 0.03
Chlordane 3.4 3.4 3.4 6e-05 1e-04 4e-04 5e-04 0.2 0.5 1.3
Total PCBs 29 34 34 2e-05 6e-05 2e-04 2e-05 1.1 2.9 7.8
Mercury 11 15 15 8e-06 3e-05 7e-05 1e-04 0.08 0.3 0.7

Hazard Index

1.4 3.7 9.8

Note - Doses are reported in scientific notation format. For example, 1e-02 is the same as 1 x 10-2 or 0.01.



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