Contaminant Trends in Sport Fish from Lake Roosevelt

and the Upper Columbia River, Washington, 1994 to 1998

By Mark D. Munn

ABSTRACT

Fish from Lake Roosevelt were first reported to contain elevated concentrations of contaminants in the early 1980’s, with mercury, dioxins

and furans, and polychlorinated biphenyls (PCBs)

identified as being of most concern to human

health. Over the following years there were a

series of studies by United States and Canadian

agencies addressing contaminants in fish from

both a human and environmental perspective. In

the early 1990’s, industrial discharges to the

Columbia River above the international boundary

decreased. The dominant changes in industrial

practices included a reduction in slag and effluent

discharges from a lead-zinc smelter, and a reduction in dioxins and furans due to processing

changes at a Canadian pulp mill. It is believed that

these two alterations in industrial practices may

have greatly reduced the loading of selected

contaminants to the Columbia River system. In

response to these recent changes, the U.S. Geological Survey initiated this present study for the

purpose of determining the present concentrations

of mercury, dioxins and furans, and PCBs in fish,

and, if possible, to determine if concentrations

have changed since the 1994 studies. All contaminant analysis was done on fish fillets in order to

address human health concerns.

Our study concluded that the concentrations

of contaminants in fish that were identified as a

potential threat to human health have either not

changed since the 1994 studies, or have decreased.

PCBs, as determined by Aroclor 1254, do not

appear to have changed between 1994 and 1998;

sources of PCBs are presently unknown. In

contrast, dioxins and furans, as indicated by

2,3,7,8-TCDF, did show a significant decrease 

rainbow trout fillets from 1994 to 1998. Howev

there was no apparent change in the average

2,3,7,8-TCDF concentrations in mountain whi

fish, with the reason uncertain at this time.

Average concentrations of 2,3,7,8-TCDF were

higher in mountain whitefish than in rainbow tro

Toxicity equivalence concentrations (TEC) are

determined by summing the relative toxicity of

individual congeners of dioxins, furans, and to

“dioxin-like” PCB congeners in individual fish

Rainbow trout from the upper reach have highe

TECs than rainbow trout from the lower reach

with trout from the upper reach having a highe

percentage of the toxicity from toxic ”dioxin-lik

PCBs than dioxin and furan compounds. In

relation to mercury, the concentrations of total

mercury in walleye have significantly decrease

by about 50 percent from 1994 to 1998.

INTRODUCTION

The upper Columbia River, including Lake

Roosevelt, is of great regional importance due to it

extensive recreational use and fishery resources (fig

Studies in the 1980’s reported that concentrations o

specific contaminants in sport fish were high enoug

to pose a potential threat to human health. Contam

nants of most concern were mercury and several

organochlorine compounds, including dioxins and

furans and PCBs. In response to concerns about th

potential threat of these contaminants to the enviro

ment and human health, the Lake Roosevelt Water
2

Quality Council (LRWQC) was organized in 1990

consisting of local citizen groups, the Colville Confederated and Spokane Tribes, and various government

agencies. The LRWQC, in cooperation with the

U.S. Environmental Protection Agency (USEPA),

Washington Department of Ecology (WDOE), and

U.S. Geological Survey (USGS), have investigated

contaminants in Lake Roosevelt fish. In the late

1980’s, Canadian scientists reported elevated concentrations of dioxins and furans in Lake Roosevelt whitefish collected from the upper Columbia River (Mah and

others, 1989), resulting in Health and Welfare Canada

issuing a health advisory. In response to this, the

WDOE determined that dioxins and furans were

present in sport fish collected from Lake Roosevelt

(Johnson and others, 1991). This was followed up by a

number of additional studies dealing with different

species and locations. The most recent study of

organochlorine compounds in fish tissue was the 1994

USEPA study (EVS Consultants, 1998) that analyzed

dioxins, furans, and PCBs in sport fish tissu

purpose of investigating human health conce

of the more important findings of the 1994 s

that concentrations of dioxins and furans had 

in fish over time. The most recent mercury s

by the USGS in 1994 resulted in the Washin

Department of Health (DOH) issuing a fish 

tion advisory (Erwin and Munn, 1997).

In the early 1990’s, industrial discharg

Columbia River above the international bou

decreased. Slag and effluent discharge from 

Cominco lead-zinc smelter upstream in Trai

Columbia (B.C.) were reduced. In addition, 

bleaching and wastewater treatment process

pulp mill in Canada have improved the quali

ent discharged to the Columbia River (Serda

others, 1994). It is believed that these two c

industrial practices have reduced the loading 

mercury, dioxins, and furans to the Columbi

system. In response to these recent changes 

0 10 20 30 40 MILES

0 10 30 40 KILOMETERS 20 

OR

ID

Map location

WA

Spokane

Trail

Northport

Kettle Falls

Castlegar

Grand Coulee Dam

Figure 1. Lake Roosevelt in the upper Columbia River, including the upper sampling reach 

between Northport and Kettle Falls, and the lower sampling reach from the Spokane River 

to Grand Coulee Dam,Washington.

CANADA

UNITED STATES

IDAHO

WASHINGTON

49°

48°

119° 117°

Lower Reach

Upper Reach

International boundary

State boundary

Sanpoil River

Lake Roosevelt 

Colville River

Spokane River

Priest

Lake

Kootenay

River

Pend Oreille

River

Pend

Oreille

Lake

Coeur d'Alene

Lake

Hangman

Creek

Little Spokane River

Columbia River

Kettle River
industrial discharges, the LRWQC requested that the

USGS initiate this follow-up fish tissue study. The

objective of this study was to determine the present

concentrations of mercury, dioxins and furans, and

PCBs, and, if possible, determine if concentrations

have changed since the 1994 studies.

Acknowledgments

This study could not have been completed without the assistance of many individuals and organizations. I thank the Spokane Tribe along with Brett Smith

and Ray Smith of the USGS for collecting the fish.

Dorene MacCoy provided technical assistance throughout the report. Dennis Helsel, Robert Black, and Frank

Ossiander provided statistical assistance. I also thank

Bernie Bonn, Gil Bortelson, Sharon Fitzgerald, Patty

Stone, and Glenn Patrick for technical reviews. This

report was produced by Connie Dean (Illustrator),

Ginger Renslow (Publication Editor), and John

Clemens (Technical Editor) of the Washington District

Technical Communication Section. This study was

funded by the Lake Roosevelt Water Quality Council

and administrated by the Colville Confederated Tribes.

OVERVIEW OF CONTAMINANTS

The purpose of this section is to provide an overview of the contaminants presented in this study and

therefore present basic information on PCB Aroclors,

dioxins and furans, toxic “dioxin-like” PCB congeners,

and mercury. Also presented is an overview of the

calculation of toxicity equivalence concentrations

(TECs) that are used to determine total combined

toxicity of dioxins, furans, and toxic “dioxin-like”

PCB congeners.

PCBs

Polychlorinated biphenyls (PCBs) are a class of

209 individual organic chemical compounds. The basic

PCB structure is shown in figure 2. Individual PCBs,

called congeners, differ from one another in the number

of chlorine atoms that they contain (1 to 10) and in the

relative positions of those atoms within the molecule.

PCBs are chemically and physically stable, and they

have excellent insulating properties that made them

popular for use in transformers and other electrical

equipment. In addition, PCBs were used in inks, paint,

plastics, as pesticide extenders, and for other appli

tions. At their peak production in 1970, 38,600 ton

PCBs were produced in the United States (Smith a

others, 1988). No known natural sources of PCBs

exist. Because of their chemical stability, they are

long-lived in the environment. PCBs are structural

similar to the pesticide DDT and cause some of the

same abnormalities in wildlife, including eggshell t

ning in birds and decreased reproduction of aquatic

species. In humans, PCBs have been linked to abn

malities of the immune, reproductive, nervous, and

endocrine systems (EVS Consultants, 1998). Som

PCB congeners are thought to act by the same biochemical mechanism as dioxins and furans and are

called toxic “dioxin-like” PCBs. USEPA has classi

all PCBs as probable human carcinogens. Because 

their toxicity and environmental persistence, manu

facture of PCBs in the United States ceased in 197

WDOE has set a screening value for total PCBs in

edible fish tissue of 1.4 μg/kg (micrograms per kilo

gram) (Johnson and others, 1994). This value was

developed using USEPA risk assessment guideline

and is based on an increased risk level of 1 cancer 

1 million (USEPA, 1995). When they were being 

duced, PCBs were marketed as mixtures of congen

under the trade name Aroclor. Because of this, stud

have historically analyzed for PCB mixtures, rathe

than individual congeners. In addition, congenerspecific analysis of PCBs is difficult because of the

large number of congeners. Previous studies of La

Roosevelt and the upper Columbia River analyzed 

three Aroclor mixtures (1242, 1254, and 1260) and 

analyses for individual, toxic “dioxin-like” PCB co

geners in Lake Roosevelt fish have been reported p

to this study.

5 6 6' 5'

5

4 4'

6 6' 5'

PCB

Figure 2. Schematic of polychlorinated biphenyl

(PCB). The numbers indicate the position of the

chlorine atoms; 6, chlorine atom in the 6 position

6', chlorine atom in the 6 prime position.

th

th
4

Dioxins and Furans

Dioxins (polychlorinated dibenzo-p-dioxins

(PCDDs)) and furans (polychlorinated dibenzofurans

(PCDFs)) are formed as by-products of industrial

chemical processes and during combustion of chlorinated organic compounds, incineration of municipal

waste, and chlorine bleaching of wood pulp (fig. 3).

They have no commercial or domestic applications and

are not produced intentionally. There are 75 different

types of dioxins, of which 2,3,7,8-tetrachlorodibenzop-dioxin (2,3,7,8-TCDD) is the most toxic and therefore widely studied. PCDFs are chemically similar to

PCDDs and occur in 135 forms. Most significant of the

PCDFs detected in Columbia River fish is 2,3,7,8-tetrachlorodibenzofuran (2,3,7,8-TCDF) because of its pervasiveness in fish from the vicinity of bleached-kraft

pulp mills (Mah and others, 1989; Johnson and others,

1991). Since these compounds are present in the

environment at low concentrations, they are usually

reported in picograms per gram (pg/g) or parts per trillion in fish tissue. The U.S. Environmental Protection

Agency (1993) considers dioxins and furans to be

carcinogens. However, the full effects of dioxins and

furans on human and environmental health are not fully

understood, and therefore making conclusive statements about their effects at specific concentrations is

not yet possible.

Toxicity Equivalence Concentratio

PCDDs and PCDFs with chlorine atom

at the 2,3,7, and 8 positions (fig. 3) are consi

most toxic. There are 7 PCDDs and 10 PCDF

substitution pattern. To assess the toxicity o

PCDF mixtures in fish, a set of toxicity equi

factors (TEFs) are used to convert toxicity o

congener to that of 2,3,7,8-TCDD, called tox

equivalent concentrations (TECs). Similar T

TECs have been calculated for the toxic “dio

PCBs. An example of TEC calculations and 

tion of total toxicity for some dioxin congene

in table 1. The TEC values presented in this 

used for between site comparisons only and 

human health risk evaluation.

Table 1. An example table of toxicity equivalen

tration (TEC) calculations for some dioxin conge

[pg/g, picograms per gram]

___________________________________________

Measured Toxicity T

concen- equivalence e

tration factor c

Dioxin congeners (pg/g) (TEF) (T

___________________________________________

2,3,7,8-TCDD 0.05 1 

1,2,3,7,8-PeCDD 0.08 0.5 

1,2,3,4,7,8-HxCDD 0.03 0.1 

1,2,3,4,6,7,8-HpCDD 0.08 0.01 

OCDD 1.05 0.001 

___________________________________________

Total 

___________________________________________

Mercury

Mercury can enter the atmosphere fro

sources (oceans and volcanoes) and human s

(burning waste and coal). Mercury can ente

aquatic environment through the atmosphere 

itation, from the weathering of rock, or from 

discharged from mines, smelters, and wastew

ment plants. Some pesticides also contain me

can be washed into streams from urban and a

applications. Inorganic mercury that occurs 

and in small quantities is not of human and e

mental health concern. However, when mer

present in an aquatic or sediment environme

PCDD

PCDF

6 4

9 1

3

2

7

8

6 4

9 1

3

2

7

8

Figure 3. Polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated

dibenzofuran (PCDF) schematic. The numbers indicate the position of

the chlorine atoms around an aromatic ring structure of carbon atoms; 6, 

chlorine atom in the 6 position. th
anaerobic (without oxygen) conditions, sediment bacteria can change inorganic mercury into the more toxic

organic forms of mercury. Organic forms of mercury

are readily taken up in the tissue of aquatic organisms.

These forms of mercury have toxic effects on aquatic

organisms as well as fish-eating wildlife and can bioaccumulate up the food chain (Eisler, 1987). Mercury

can therefore accumulate in the muscle tissue (fillet) of

fish to levels that may pose a threat to human health

(Erwin and Munn, 1997).

Previous studies of mercury in sediment

(Bortleson and others, 1994) and fish tissue (Serdar,

1993) concluded that mercury in Lake Roosevelt was

higher than background concentrations. Serdar (1993)

reported that mercury concentrations were higher in

walleye than in other species in the lake and that

concentrations were elevated to levels that could pose a

threat to human health. In 1997, the DOH released a

health advisory based upon mercury data collected by

the USGS (Erwin and Munn, 1997).

METHODS

This study was designed to permit a compari

of present concentrations of contaminants to those

reported in the 1994 USEPA study (EVS Consultan

1998) and 1994 USGS study (Munn and others, 199

therefore decisions on fish species, sample location

and chemical analysis were based on previous data

Fish were collected from two major reaches of Lak

Roosevelt and the upper Columbia River (fig. 1). T

upper reach extends from Kettle Falls to Northport

which includes both free-flowing river and the upp

reservoir. The lower reach is exclusively reservoir 

extends from the Spokane River down to Grand Cou

Dam. Fish collected included walleye (Stizostedio

vitreum), wild and net-pen rainbow trout (Oncorhy

chus mykiss), and mountain whitefish (Prosopium

williamsoni). Rainbow trout collected from the low

reach in 1994 (EVS Consultants, 1998) were not se

rated into wild and net-pen; therefore, 1994 lower r

bow trout are referred to as mixed. Number of fish 

location and analysis are presented in table 2. All fi

were collected during the summer and fall of 1998 

Table 2. Summary of study by contaminant group, data source, species, and location

[Samples were collected from the upper reach (Northport to Kettle Falls) and lower reach (Spokane River to Grand Coul

Dam) of Lake Roosevelt. The 1994 mercury study was done by the U.S. Geological Survey and the 1994 dioxin and fur

and PCB study was done by EVS Consultants (1998). The U.S. Geological Survey did all contaminant groups in 1998.

Samples with the same letter were compared statistically; --, data not collected]

_________________________________________________________________________________________________

 Net-pen Mountain

 Walleye Wild rainbow trout rainbow trout Whitefish

 (13-16 inches) (14-23 inches) (13-23 inches) (17-21 inche

Contaminant Data ______________ ________________ ____________ __________

group source Upper Lower Upper Lower Lower Upper

_________________________________________________________________________________________________

PCB 1254 EPA 1994 -- -- 23a -- 7b* --

USGS 1998 -- -- 8a 8b 8b --

Dioxins/ EPA 1994 -- -- 23c -- 7d* 8e

 furans USGS 1998 -- -- 8c 8d 8d 5e

Toxic “Dioxin USGS 1998 -- -- 2 2 4 --

 like” PCB

 congeners

Mercury USGS 1994 8f 8g -- -- -- --

USGS 1998 8f 8g -- -- -- --

_________________________________________________________________________________________________

 * The 1994 USEPA (EVS Consultants, 1998) study did not separate net-pen and wild rainbow trout, therefore,

concentrations presented in this report may reflect a combination of both groups.
6

the Spokane Tribe using a combination of an electroshock boat and gill nets. Fish were processed in a

similar fashion with minor differences outlined below.

Upon collection, fish were sacrificed, placed in a

labeled plastic bag if used for mercury analysis and in

foil if used for organic analyses. Samples were frozen

on dry ice and shipped to the laboratory for processing.

The first processing step was to collect basic

physical information on each fish: total length, from

the most anterior part of the fish to the tip of the longest

caudal fin ray, in centimeters; and total weight, in

grams. Processing equipment was made of glass or

stainless steel. Strict guidelines were followed in the

cleaning of all equipment that came into contact with

samples, and equipment was cleaned between each fish

sampling. Cleaning procedures included washing

equipment with phosphate-free laboratory detergent

solution and rinsing in Type I reagent-grade water

(Munn and others, 1995).

Individual fillet samples were removed in

accordance with procedures in USEPA (1995), which

include the belly flap. For the mercury portion of this

study, skin was removed on the individual walleye

fillets; whereas, for the other contaminants and species,

the skin was left on. Once a fillet was removed it was

frozen and shipped on dry ice to the appropriate

laboratory for analysis.

Rainbow trout and mountain whitefish were

analyzed for dioxins and furans using USEPA Method

1613B (U.S. Environmental Protection Agency, 1994),

which analyzed for 17 dioxin and furan congeners.

Also, rainbow trout samples were analyzed for PCB

Aroclors using USEPA method 8082 (U.S. Environmental Protection Agency, 1998) along with a small

subset of samples analyzed for 13 individual toxic

“dioxin-like” PCB congeners using USEPA Method

1668 (U.S. Environmental Protection Agency, 1995b).

All fish tissue contaminant values are reported as wet

weight. Standard quality assurance and quality control

procedures were used for all laboratory analysis and

resulted in all data meeting quality criteria. Samples

were analyzed for PCBs, dioxins, and furans, by Axys

Analytical in Victoria, B.C.

Walleye samples were shipped to the USGS

trace-element laboratory in Atlanta, Georgia, where

they were analyzed for total mercury using a cold vapor

atomic absorption method (Elrick and Horowitz,

1986). Concentrations of mercury are presented as

mg/kg, wet weight.

Statistical analysis was performed usi

cator contaminant for each contaminant gro

PCB, Aroclor 1254 was used to compare betw

and 1998; whereas for dioxin and furans the 

congener 2,3,7,8-TCDF was used. These we

because they were detected in all samples and 

prevented statistical problems associated wi

detections. Because sample sizes were small 

fore distributions uncertain, the non-parame

Kruskal-Wallis or the Mann-Whitney U tests 

to determine if concentrations had changed f

to 1998. Tests were considered to be signifi

P<0.05; if a statistical test was found to be n

ficant, then a statistical power (1-β) was calc

Tukey’s LSD test was used as the multicomp

on ranked data (Helsel and Hirsch, 1992).

RESULTS

Concentrations of contaminants in fish 

identified as a potential threat to human hea

either not changed since the 1994 studies, or 

decreased. Presented and discussed below a

of analyses for PCBs, dioxins and furans, to

equivalent concentrations, and mercury. Da

concentrations of contaminants summarized 

report can be obtained from the Washington 

web site at

 http://wa.water.usgs.gov/LakeRoosevelt/

PCBs

Median concentrations of PCB Aro

in 1994 rainbow trout were similar to 1998 

trout.

Historically, all PCB studies on Lake 

and the upper Columbia River have focused 

Aroclors 1242, 1254, and 1260. While this 

examined all three PCB Aroclors, we relied 

1254 concentrations for statistical comparis

median concentrations of Aroclor 1254 in ra

trout collected in 1998 were 24 μg/kg (16-4

for upper reach wild rainbow trout, 15.5 μg/

(8.8-49 μg/kg) for lower reach wild rainbow 

5.7 μg/kg (3.3-35 μg/kg) for lower reach ne

bow trout. For the upper reach, no significa

ence was found in the concentration of Aroc
Individual Sample 

Median

1254 AROCLOR CONCENTRATIONS,

IN MICROGRAMS PER KILOGRAM (

μg/kg) WET WEIGHT

LOWER REACH UPPER REACH

1994 1994 1998 1998 1998

MIXED* WILD WILD WILD NET-PEN

*Wild and net-pen not distinguished in study

0

20

40

60

80

100

110

between 1994 (median=21.6 μg/kg) and 1998

(median=24 μg/kg) rainbow trout (Mann-Whitney U

Test = 91, P=0.96). However, additional analysis determined that there was insufficient power (1-β = 0.05) to

detect a difference among the 2 years due to the high

variability. The high variability could be due to several

reasons: uneven sample size (23 in 1994 and 8 in

1998), naturally high variability due to the distribution

of PCBs in the system, and differences in the processing and laboratory analysis between the 2 years.

In the lower reach, a significant difference was

found among the three trout groups (Kruskal-Wallis

test, P<0.05). Multiple comparison tests (Tukey’s LSD

on ranked data) determined that there was no significant difference between the 1994 mixed rainbow trout

(median=15.6 ppb) and the 1998 wild rainbow trout

(median=15.5 ppb), but that the concentration of 1254

in 1998 net-pen rainbow trout (median=5.7 ppb) was

significantly lower (fig. 4).

Dioxins and Furans

Dioxins and furans are still present in Lak

Roosevelt sport fish, and concentrations of 2,3,7

TCDF did decrease from 1994 to 1998 in rainbo

trout. However, there was no apparent change i

the 2,3,7,8-TCDF concentrations in mountain

whitefish. Median concentrations of 2,3,7,8-TC

were higher in mountain whitefish than in rainb

trout.

This 1998 USGS study found dioxins (PCDD

and furans (PCDFs) present in all fish samples collected including wild and net-pen rainbow trout an

whitefish. Total concentrations of PCDDs+PCDFs

ranged from 1.1 pg/g in net-pen rainbow trout to

6.0 pg/g in whitefish from the upper reach, with PC

making up over 70 percent of the total in most samp

(fig. 5). Median concentrations of 2,3,7,8-TCDF w

about the same in wild rainbow trout collected from 

upper (0.74 pg/g) and lower (0.68 pg/g) reaches, bu

Figure 4. Concentrations of 1254 Aroclor from 1994 (EVS Consultants, 1998) and 1998 studies.

Individual rainbow trout fillet samples from upper and lower reaches of Lake Roosevelt, Washington.
8

1998 USGS STUDY

0

1

2

3

4

5

6

7

2,3,7,8-TCDD 2,3,7,8-TCDF Total

PCDD/PCDF

Wild, upper reach rainbow trout

Wild, lower reach rainbow trout

Net-pen, lower reach rainbow trout

Upper reach mountain whitefish

Figure 5. Median concentrations of dioxins and furans in rainbow trout and mountain 

whitefish from the upper and lower reaches of Lake Roosevelt, Washington, 1998. CONCENTRATION, IN PICOGRAMS PER GRAM (pg/g) WET WEIGHT

8

0

2

4

6

8

10

Figure 6. Concentrations of 2,3,7,8-TCDF in rainbow trout and mountain whitefish fillet 

samples from the upper and lower reaches of Lake Roosevelt, Washington.

1994 1994 1998 1998 1998

MIXED* WILD WILD

1994

WILD WILD

1998

NET-PEN WILD

LOWER REACH UPPER REACH

2,3,7,8-TCDF CONCENTRATION, 

IN PICOGRAMS PER GRAM (pg/g) WET WEIGHT

RAINBOW TROUT WHITEFISH

*Wild and net-pen not distinguished in study

Individual Sample 

Median
concentrations were slightly lower in net-pen rainbow

trout (0.42 pg/g) collected in the lower reach. In contrast, 2,3,7,8-TCDF in whitefish collected from the

upper reach had a median concentration of 4.61 pg/g.

Although dioxins and furans are present in

all fish tissue sampled, the concentrations of 2,3,7,8-

TCDF in rainbow trout have decreased, but there is no

apparent change in concentrations of 2,3,7,8-TCDF in

mountain whitefish (fig. 6). Three statistical comparisons were made for 2,3,7,8-TCDF concentrations.

First, 2,3,7,8-TCDF concentrations in wild rainbow

trout from the upper reach have significantly decreased

(Mann-Whitney U-test, P<0.05) from 1994 to 1998.

The median concentration in 1994 was 1.5 pg/g,

decreasing to 0.74 pg/g in 1998. Second, concentrations of 2,3,7,8-TCDF were significantly different

among the three rainbow trout groups (1994 mixed

rainbow trout, 1998 net-pen rainbow trout, and 1998

wild rainbow trout) in the lower reach (Kruskal-Wallis

test, P<0.05). Tukey’s multiple comparison test on

ranked data determined that of the three groups,

2,3,7,8-TCDF concentrations in 1994 mixed rainbow

trout were significantly higher (median=1.5 pg/g,

P<0.05) than concentrations in either 1998 wild rainbow trout (median=0.68) or net-pen rainbow trout

(median=0.42), with the 1998 groups not different

from each other (P>0.05). Third, in contrast to the

rainbow trout, there was no significant difference

(Mann-Whitney U test, P>0.05) in the concentration of

2,3,7,8-TCDF in mountain whitefish collected from the

upper reach between 1994 and 1998. However, it is

important to note that as in the PCB statistics, there was

high variability in 2,3,7,8-TCDF concentrations for

both years along with a small sample size in both 1994

(n=8) and 1998 (n=5). This resulted in a low statistical

power (1-β = 0.10) for distinguishing differences

between years.

The decrease in 2,3,7,8-TCDF in rainbow trout

between 1994 and 1998 likely reflects the changes in

pulp mill processing upstream and substantiates earlier

studies that dioxins and furans are decreasing over time

(EVS Consultants, 1998). However, although there is

a decrease in dioxins and furans in rainbow trout,

concentrations of 2,3,7,8-TCDF in mountain whitefish

remained elevated for unknown reasons. The issue of

higher concentrations of 2,3,7,8-TCDF may reflect the

trophic position of whitefish compared with rainbow

trout. Rainbow trout in the Columbia River/Lake

Roosevelt system feed heavily on plankton and benthic

invertebrates at particular times or locations.

In contrast, mountain whitefish in the upper system

are primarily benthic feeders, so they would tend to

consume food that is in more direct contact with

contaminated sediments.

Toxicity Equivalence Concentrations

Rainbow trout from the upper reach have

higher toxicity equivalent concentrations (TECs

than rainbow trout from the lower reach, with

trout from the upper reach having a higher percentage of the toxicity from toxic ”dioxin-like”

PCBs than dioxin and furan compounds.

For the PCDD and PCDF congeners and the

toxic “dioxin-like” PCBs in 1998 rainbow trout, TE

were calculated to give relative toxicity values for 

upper and lower reaches. The results of this analys

provide a preliminary screening of the combined to

city of these organochlorine compounds in Lake

Roosevelt sport fish. Figure 7 summarizes the TEC

for rainbow trout. The total TEC for all dioxin-like

compounds was highest in the upper reach rainbow

trout, with an overall average (PCDD, PCDF, and PC

TEC of 0.9 pg/g. The average TECs for the lower re

net-pen rainbow trout (0.3 pg/g) were similar to the

lower reach wild rainbow trout (0.4 pg/g). For both 

upper and lower reaches the “dioxin-like” PCBs co

posed the largest portion of the total toxicity, especia

in the upper reach, where the “dioxin-like” PCBs

accounted for more than 70 percent of the total toxic

Further studies are needed to determine the source 

well as the human and wildlife health effects of the

toxic “dioxin-like” PCBs in Lake Roosevelt.

Mercury

The concentrations of total mercury in

walleye have decreased by about 50 percent from

1994 to 1998.

This study found that total mercury in walley

fillets decreased (Mann-Whitney U test, P<0.05)

between 1994 and 1998 (fig. 8). Median concentra

tions of mercury in 13- to 16-inch walleye collecte

from the upper reach decreased significantly from

0.18 mg/kg to 0.11 mg/kg and decreased from 0.26

to 0.15 mg/kg in the lower reach.

Two possible explanations can be given for t

decrease in mercury concentrations in walleye tissu
10

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Figure 7. Toxicity equivalent concentrations (TECs) for 1998, dioxins and furans, 

and PCB congener values in rainbow trout from the upper and lower reaches of 

Lake Roosevelt, Washington.

NET-PEN WILD WILD

LOWER REACH UPPER REACH

2,3,7,8-TCDF

2,3,7,8-TCDD

Other PCDDs/PCDFs

PCB Congeners

1998 USGS STUDY

TOXICITY EQUIVALENTS,

 IN PICOGRAMS PER GRAM (pg/g) WET WEIGHT

10

0

0.05

0.10

0.15

0.20

0.25

0.30

0.35

Figure 8. Concentrations of total mercury in walleye fillet tissue from the upper and 

lower reaches of Lake Roosevelt, Washington, 1994 and 1998.

 MERCURY, IN MILLIGRAMS PER KILOGRAM (mg/kg) WET WEIGHT

1994 1998 1994 1998

LOWER REACH UPPER REACH

Individual Sample 

Median
One explanation may be related to the decrease in

discharge from industrial sources. Although mercury

can originate from both natural and human processes, a

major source of mercury to the upper Columbia River

system was believed to be the Cominco lead-zinc

smelter in Trail, B.C., 10 miles north of the international border. The smelter has recently reduced its

overall discharge of effluent, which may be a major

reason for the reduction of mercury in the upper reach

(Serdar and others, 1994). There are other potential

sources of mercury to the lower reach of Lake

Roosevelt from the Spokane River that drains the

Coeur d’Alene Basin. Although the Coeur d’Alene

Basin and Spokane River have been studied extensively

for metals (Johnson and others, 1994), mercury input to

the Spokane arm of Lake Roosevelt has not been well

documented.

 Another explanation of reduced mercury concentrations in walleye may be the substantial change in

flow management in Lake Roosevelt since 1994. In

1994, the retention time of water in the reservoir was

approximately 40 days. Over the last few years the

retention time has decreased somewhat due to flow

requirements downstream. Because the reduction in

retention time probably does not allow the lake sediments to become anoxic, which is required for the

production of organic forms of mercury, the potential

for mercury bioaccumulation is reduced. Although

mercury sources have been documented, the spatial and

temporal trends in mercury concentrations in Lake

Roosevelt fish tissue are not fully understood. While

industrial input has been reduced and flow management has changed in Lake Roosevelt, it is important to

note that mercury does not leave a system rapidly and

may persist in the bed sediments as well as fish tissue.

CONCLUSIONS

Contaminants examined in this study are either

decreasing in fish tissue, or remaining the same,

depending on the contaminant and fish species. Concentrations of PCBs in rainbow trout remain elevated

and do not appear to be decreasing. Although dioxins

and furans are still present in sport fish, concentrations

of 2,3,7,8-TCDF have decreased in rainbow trout, but

not in whitefish. It is presently unknown why concentrations of 2,3,7,8-TCDF in whitefish are higher than

rainbow trout or why concentrations have not changed.

Total mercury decreased in walleye from 1994 to 1998.

The decrease in some of the contaminants found in

sport fish is thought to be a function of reductions 

industrial loadings to the Columbia River, but coul

also be partially due to changes in reservoir manag

ment practices. It is unknown whether reservoir

management practices in the future will affect the

concentrations or distribution of contaminants in

Lake Roosevelt.

REFERENCES CITED

Bortleson, G.C., Cox, S.E., Munn, M.D., Schumaker, R

and Block, E.K., 1994, Sediment-quality assessmen

Franklin D. Roosevelt Lake and the upstream reach 

the Columbia River, Washington, 1992: U.S. Geol

cal Survey Open-File Report 94-315, 130 p., 1 pl.

Eisler, R., 1987, Mercury hazards to fish, wildlife, and

invertebrates--a synoptic review: U.S. Fish and

Wildlife Service, Biological Report 85 (1.10), 90 p

Elrick, K.A., and Horowitz, A.J., 1986, Analysis of rock

and sediments for mercury, by wet digestion and fla

less cold vapor atomic absorption: U.S. Geologica

Survey Open-File Report 86-596, 12 p.

Erwin, M.L., and Munn, M.D., 1997, Are walleye from L

Roosevelt contaminated with mercury? U.S. Geolo

gical Survey Fact Sheet 102-97, 4 p.

EVS Consultants, 1998, Assessment of dioxins, furans, 

PCBs in fish tissue from Lake Roosevelt, Washingt

1994: Seattle, Washington, U.S. Environmental Pro

tion Agency, 53 p.

Helsel, D.R., and Hirsch, R.M., 1992, Statistical method

water resources: New York, Elsevier Pub., Studies 

Environmental Science 49, 522 p.

Johnson, A., Serdar, D., and Davis, D., 1994, Results of 1

screening survey on PCBs and metals in the Spoka

River: Olympia, Wash., Washington State Departm

of Ecology, 21 p.

Johnson, A., Serdar, D., and Magoon, S., 1991, Polychl

nated dioxins and furans in Lake Roosevelt (Colum

River) sportfish, 1990: Olympia, Wash., Washingt

State Department of Ecology, Publication no. 91-4

47 p.

Mah, F.T.S., MacDonald, D.D., Sheehas, S.W., Tuomine

T.M., and Valiela, D., 1989, Dioxins and furans in

sediment and fish from the vicinity of ten inland pu

mills in British Columbia: North Vancouver, B.C.,

Water Quality Branch, Inland Waters Directorate,

Environment Canada, 77 p.

Munn, M.D., Cox, S.E., and Dean, C.J., 1995, Concent

tions of mercury and other trace elements in walley

smallmouth bass, and rainbow trout in Franklin D.

Roosevelt Lake and the upper Columbia River,

Washington, 1994: U.S. Geological Survey Open-

Report 95-195, 35 p.
12

Serdar, D., 1993, Retrospective analysis of toxic contaminants in Lake Roosevelt, Draft No. 2: Olympia, Wash.,

Evergreen State College, 89 p.

Serdar, D., Yake, B., and Cubbage, James, 1994, Contaminant trends in Lake Roosevelt: Olympia, Wash.,

Washington State Department of Ecology, Publication

no. 94-185, 32 p.

Smith, J.A., Witkowski, P.J., and Fusillo, T.V., 1988,

Manmade organic compounds in surface waters of the

United States--a review of current understanding: U.S.

Geological Survey Circular 1007, 92 p.

U.S. Environmental Protection Agency, 1993, Interim report

on data and methods for assessment of 2,3,7,8-tetrachlorodibenzo-p-dioxin risks to aquatic life and associated wildlife: Washington, D.C., U.S. Environmental

Protection Agency, EPA/600/R-93/055, [variously

paged].

———1994, Method 1613--revision B, tetra-thr

octa-chlorinated dioxins and furans by isoto

HRGC/HRMS: U.S. Environmental Protec

Agency, Office of Water, Washington, D.C.

———1995a, Guidelines for assessing chemica

nant data for use in fish advisories, v. 1, fish 

and analysis: Washington, D.C., Environm

Protection Agency report 823-R-93-002, 28

———1995b, Toxic polychlorinated biphenyls b

dilution high resolution gas chromatograph

resolution mass spectrometry: U.S. Enviro

Protection Agency, Office of Water, Washin

D.C., 66 p.

———1998, EPA Method 8082A--polychlorina

nyls (PCBs) by gas chromatography, revisio

test methods for evaluating solid wastes, ph

chemical methods: SW-846, 48 p.
UPDATE FROM THE

WASHINGTON STATE

DEPARTMENT OF HEALTH REGARDING

CONSUMPTION OF LAKE ROOSEVELT

CAUGHT FISH

In 1994, the U.S. Geological Survey (USGS)

conducted a study on Lake Roosevelt to assess mercury

concentrations in walleye. The results of this study

were summarized in the USGS fact sheet "Are walleye

from Lake Roosevelt contaminated with mercury?"

Recent studies have provided improved information

regarding present concentrations of contaminants in

Lake Roosevelt fish, the toxicity of mercury, and the

consumption of fish by Lake Roosevelt anglers. DOH

used this information in a human health assessment and

is providing the following updated recommendations

regarding the consumption of fish from Lake

Roosevelt.

Mercury

A recently completed study by DOH concludes

that mercury in fish may be slightly more toxic than

previously thought. DOH has proposed a tolerable

daily intake (TDI) developed to protect children from

impaired neurological development and other longterm effects resulting from prenatal exposure to methylmercury. This TDI, defined as an amount that can be

consumed daily that is not expected to have any

adverse health impacts, ranges from 0.035 - 0.08

micrograms of mercury per kilogram bodyweight per

day μg/kg/day). This TDI incorporates the findings of

recently published studies and is more protective than

the Environmental Protection Agency's value of

0.1 μg/kg/day.

In 1994 and 1995, DOH in cooperation with the

Spokane Tribe of Indians surveyed anglers on Lake

Roosevelt, primarily at recreational boat launch facilities, to determine how much and how often locally

caught fish are consumed. Based on these results and

results from the recent USGS study, which found

decreasing mercury concentrations in fish, we do not

expect individuals to experience any adverse health

effects from consuming fish with the reported mercury

concentrations. This includes the populations of greatest concern, which consist of women of child bearing

age and their offspring.

PCBs and Dioxins

While scientists and health professionals wo

wide acknowledge that exposure to PCBs and diox

should be minimized, there is currently no agreeme

on what level of exposure is deemed to not result in

adverse health effects. Presently, DOH is unable to

provide specific recommendations regarding the

consumption of fish from Lake Roosevelt, which

contain trace amounts of these compounds.

DOH recommendations for reducing yo

exposure to contaminants in fish:

Fish are an important part of a healthy diet. T

are an excellent source of protein, are low in satura

fats, and contain beneficial oils such as omega-3 po

unsaturated fatty acids, which are thought to help

reduce cholesterol levels, high blood pressure, and 

risk of coronary heart disease. (The American Hea

Association recommends people eat two to three me

of fish per week.)

Based on the most recent data, DOH does no

expect anglers to experience any adverse health effe

from eating fish taken from Lake Roosevelt due to

mercury contamination. To reduce your exposure 

other contaminants found in fish, the following gene

recommendations are provided.

1. Consume younger and therefore smaller fish (wit

legal limits) since they generally contain lower c

centrations of contaminants than older, larger fi

2. Avoid eating bottom fish such as catfish, carp, or

sucker, which feed on the bottom and are likely 

contain higher levels of chemical contaminatio

3. When you clean the fish, remove the skin, fat, an

internal organs before you cook the fish, as the

tissues commonly contain higher concentration

environmental contaminants.

4. Cook the fish so that the fat is allowed to drip of

Recommended cooking methods include: grilli

baking, or broiling.

5. Remember that with any fresh meat, always foll

proper food handling and storage techniques. T

prevent the growth of bacteria, keep freshly cau

fish on ice and out of direct sunlight.

For more information, contact DOH at 1-877-485-7

or your local health department. Visit the DOH we

page at: http://www.doh.wa.gov/