Harris Ma

Haws Lc

LL Ferriby

CiteSeerX

COMPARING POLYCHLORINATED BIPHENYLS IN FARM-RAISED AND WILD-
CAUGHT CATFISH FROM SOUTHERN MISSISSIPPI 
 
Ferriby, LL1; Williams, ES1; Luksemburg, WJ2; Paustenbach, DJ3; Haws LC4; Birnbaum, LS5; and Harris, MA1  
 
1ChemRisk, Houston, TX; 2Vista Analytical Laboratory, El Dorado Hills, CA; 3ChemRisk, San Francisco, CA; 
4ChemRisk, Austin, TX ; 5U.S. Environmental Protection Agency, Research Triangle Park, NC  
 
Introduction 
Polychlorinated biphenyls (PCBs) are among the most thermally stable organic chemicals known.  This characteristic 
has historically made them useful in a wide array of applications including use in electrical transformers and capacitors, 
varnishes, waxes, synthetic resins, epoxy and marine paints, coatings, cutting oils, heat transfer fluids, hydraulic fluids, 
and flame retardants.1 As a result of their widespread use and their stability, these compounds are ubiquitous in the 
environment, and have been detected in media such as soils, sediment, and biota.  Further, the lipophilic nature of these 
compounds has resulted in bioaccumulation of them in the food chain.  As a result, intake of PCBs has been shown to 
occur primarily through the consumption of food and food products, especially meat, fish and dairy products.2 In fact, 
exposure to PCBs via the ingestion of meat, fish and dairy products accounts for 63-100% of the total dietary intake of 
these compounds in humans with fish being the major contributor.2 
 
While there is a substantial amount of data concerning the levels of dioxin-like compounds in fish,3-13 little data exist for 
PCBs in both wild-caught and farm-raised fish in the U.S.  Additionally, little data exists concerning the levels of all 
209 PCB congeners in fish, thereby limiting the ability to establish current background exposures resulting from the 
consumption of this particular food. 
 
Given the relatively high consumption rates of catfish in the U.S., especially the Southern States, it is believed that 
catfish could contribute appreciably to the dietary intake of PCBs.  For example, research conducted at Mississippi State 
University estimated the total consumption of catfish to be 281 million pounds and 136 million pounds per year for the 
U.S. and south central populations, respectively.14  With states such as Arkansas and Mississippi leading the U.S. in 
average per capita consumption of catfish at 5.95 and 4.61 pounds per person per year, respectively, there is a clear need 
to characterize the levels of PCBs in catfish, particularly in the south central states.14  In this study, we quantified the 
PCB levels for all 209 congeners in tissue from a number of wild-caught and farm-raised catfish collected throughout 
Southern Mississippi and this appears to represent the most substantial assessment conducted to date. 
 
Materials and Methods 
Sixty-one wild-caught and farm-raised catfish samples from Southern Mississippi were collected in March 2006.  Wild 
catfish (n=33) were caught by local fisherman along the Mississippi, Pearl, and Leaf Rivers.  Samples were collected in 
one location along the Mississippi River (MR), two locations along the Pearl River (PR and the Ross Barnett Spillway 
or RBS), and two locations along the Leaf River (LR1 and LR2). Immediately after the fish were caught they were 
measured for length, weighed and then filleted using clean knives and glass plates. Final filet weights were also 
recorded prior to packaging.  Farm-raised catfish samples (n=28) were purchased either directly from a Mississippi farm 
or from local seafood markets and/or grocery stores (seven stores visited) that obtain catfish from farms in 
Mississippi. All samples were wrapped individually in aluminum foil (shiny side out), placed in labeled plastic bags and 
frozen on dry ice in uncontaminated coolers.  Samples were kept frozen until analysis. 
 
Fish tissue samples were analyzed by Vista Analytical Laboratory (El Dorado Hills, CA) for the 209 PCB congeners 
using high resolution gas chromatography-mass spectrometry according to EPA Method 1668.  Multiple PCBs co-
eluted resulting in data for 168 PCB congeners/congener pairs for each tissue sample.  Samples with concentrations 
below the limit of detection (LOD) were assumed to have a concentration equal to the LOD divided by the square root 
of two.  All data analyses were conducted using Microsoft Excel.  The mean, median, and 25th and 75th percentile PCB 
concentrations were characterized by fish type (wild-caught and farm-raised), sample type (fillet, whole, dressed, and 
nugget) and collection site.  Ninety-five percent confidence intervals for the mean PCB levels were also calculated 
using Microsoft Excel.  All PCB concentrations are presented as wet weight unless otherwise noted.      
  
Results and Discussion 
A total of 17 blue, 3 appaloosa, and 1 willow catfish (all wild-caught) were filleted for tissue analysis.  Average fish 
weights and lengths ranged from 2.56 to 18.63 ounces and from 8.94 to 16.04 inches, respectively, as previously 
described.15  As demonstrated in Figure 1, farm-raised catfish fillets were larger than wild-caught fillets and had a 
Organohalogen Compounds Vol 68 (2006)
Late Papers
2527
higher average lipid fraction.  Interestingly, though, dressed catfish had a much lower fraction of lipids than other types 
of farm-raised samples.    
 
Figure 1: Mean percent lipid and mean tissue weight by fish type and sample type. 
 
 
 
Table 1 shows the mean, range and various percentiles of total PCB concentrations in wild-caught and farm-raised 
catfish.  Concentrations ranged from 1,052 to 72,525 pg/g wet wt for wild-caught fish and from 689 to 2297 pg/g wet wt 
for farm-raised fish, with average values of 15,626 and 1,376 pg/g wet wt and median values of 9,297 and 1,354 pg/g 
wet wt, respectively.  As expected, there was a statistically significant difference between the mean concentration for 
wild-caught and farm-raised catfish fillets (p<0.000).  Although not significantly different (p=0.30), whole wild-caught 
fish had a slightly higher mean concentration than wild-caught fillets even though the whole fish were appreciably 
smaller in size than the fish from which the fillets were taken (Figure 1).   Further examination of the relationships 
between total PCB concentration and the length and weight of the individual fish indicated that, in this study, neither 
fish weight (p=0.66) nor fish length (p=0.51) were good predictors of total PCB concentration.  Of course, more 
comprehensive analyses will be needed to determine specifically what characteristics impact PCB concentrations in 
catfish from this region of the country.  
 
Table 1: Concentration summary statistics for the 209 PCB congeners by fish type and sample type. 
 
 Concentration (pg/g wet wt)                 
 N Mean 95% CI 25
th 
Percentile Median 
75th 
Percentile Range 
All Samples 61   9085.05 5621.87 - 12548.23 1296.35 2297.13   9645.75   689.05 - 72524.93 
Wild-Caught 33 15625.69  10115.70 - 21135.68 4577.61 9296.75 20239.46 1051.65 - 72524.93 
 Fillet 24 15209.36 8561.53 - 21857.19 4243.88 9471.25 18198.39 1051.65 - 72524.93 
 Whole 9 16735.91 6457.38 - 27014.44 6915.18 8830.53 21271.36 4251.37 - 29613.03 
Farm-Raised 28 1376.44    1206.10 - 1546.78   972.73 1354.41   1729.90 689.05 - 2297.13 
 Fillet 23 1379.26    1193.49 - 1565.04   928.30 1454.16   1732.91 689.05 - 2096.33 
 Dressed 2 1260.41    1189.98 - 1330.85 1242.44 1260.41   1278.38 1224.47 - 1296.35 
 Nuggets 3 1432.16  583.37 - 2280.95   999.68 1038.48   1667.81 960.87 - 2297.13 
 
Figure 2 shows the mean total concentration and 95% confidence intervals for the wild-caught catfish by collection site.  
As demonstrated, fish caught in the Mississippi River had the highest mean total PCB concentration followed by those 
caught at the second site on the Leaf River (LR2).  Interestingly, the fish collected at the second site on the Leaf River 
were some of the smallest captured.  In contrast, the first site for the Leaf River (LR1) had the lowest mean total PCB 
concentration and the smallest sample variability.  Evaluation of the concentrations in fish at LR1 and LR2 
demonstrated a significant difference in the mean total PCB concentrations (p=0.02) indicating a potential source 
between these two sites.  For the Ross Barnett Spillway (RBS), which is part of the Pearl River (PR) just to the 
northeast of Jackson, wild-caught fish had some of the lowest tissue concentrations next to LR1 while fish collected 
from the Pearl River near Picayune were slightly higher.  However, only a moderate statistical difference in mean PCB 
concentration was detected for samples from RBS and PR (p=0.06).   
 
Organohalogen Compounds Vol 68 (2006)
Late Papers
2528
Figure 2: Mean total PCB concentration by site. 
0
10000
20000
30000
40000
50000
60000
MR PR RBS LR1 LR2M
ea
n 
To
ta
l P
CB
 C
on
ce
nt
ra
tio
n
 (p
g/
g)
 
 
The percent contribution of each of the top ten congeners contributing most to the total concentration ranged from 2.44 
– 8.29 for farm-raised catfish and 1.59 – 12.91 for wild-caught catfish (Figure 3).  Of the ten congeners in Figure 3, half 
of them contributed relatively more to total levels in wild-caught fish.  For those congeners that contributed more to the 
total concentrations in farm-raised fish (PCB-43/49, PCB-90/101, PCB-99, PCB-110, PCB-139/149), the differences in 
relative contribution between wild-caught and farm-raised were appreciably smaller than for the other five congeners.  
Interestingly, both PCB-153 and PCB-138/163/164 contributed the most of all congeners to the total PCB concentration 
for wild-caught and farm-raised catfish, while PCB-81 contributed the least to the total PCB concentration (data not 
shown) for wild-caught and farm-raised fish demonstrating somewhat consistent congener patterns between the two fish 
types.   
 
Figure 3: Percent contribution of select PCBs to total PCB concentration by fish type. 
0
2
4
6
8
10
12
14
PC
B-
43
/49
 
PC
B-
90
/10
1 
PC
B-
99
 
PC
B-
10
6/1
18
 
PC
B-
11
0
PC
B-
13
8/1
63
/16
4 
PC
B-
13
9/1
49
 
PC
B-
15
3
PC
B-
18
1 
PC
B-
18
2/1
87
 
C
on
tr
ib
ut
io
n 
to
 T
ot
al
 
C
on
ce
nt
ra
tio
n 
(%
) Wild-Caught
Farm-Raised
 
 
Figure 4: Percent contribution of select PCBs to total PCB concentration by collection site. 
0
5
10
15
20
PC
B-
43
/49
 
PC
B-
52
/69
PC
B-
76
/66
PC
B-
90
/10
1 
PC
B-
99
 
PC
B-
10
6/1
18
 
PC
B-
11
0
PC
B-
13
8/1
63
/16
4 
PC
B-
13
9/1
49
 
PC
B-
15
3
PC
B-
18
0
PC
B-
18
2/1
87
 
C
on
tr
ib
ut
io
n 
to
 T
ot
al
 
C
on
ce
nt
ra
tio
n 
(%
) MR
PR
RBS
LR1
LR2
 
Organohalogen Compounds Vol 68 (2006)
Late Papers
2529
Figure 4 illustrates the percent contribution of select PCBs to total PCB concentration by collection site.  As with fish 
type, PCB-153 and PCB-138/163/164 contributed the most at all sites demonstrating that levels of these PCBs in fish 
tissue have a regional rather than local pattern.  This is further supported by the observation that PCB-81 also 
contributed the least to the total PCB concentrations in fish tissue collected at four of the five sites: PR, RBS, LR1, and 
LR2 (data not shown).  Taken together, the congener patterns by fish type (Figure 3) and collection site (Figure 4) may 
be useful in identifying potential point sources of these chemicals for wild-caught fish and understanding why 
differences exist between farm-raised and wild-caught catfish.  These results reveal significant differences in total PCB 
concentrations exist for farm-raised and wild-caught fillets and that there are moderate to significant differences in total 
PCB concentrations between some of the collection sites.  Overall, congener patterns between wild and farm-raised fish 
and among fish captured at different sites were similar. 
 
Compared with PCB levels in catfish sampled from a primarily urbanized area,16 the PCB levels in catfish from rural 
Southern Mississippi are characterized by a much narrower range of concentrations (257,000 – 534,000 and 1,052 – 
72,524 pg/g wet wt, respectively), and a lower average (15,626 vs. 417,000 pg/g wet wt reported by Crimmins et al.16) 
and median concentration (9,297 vs. 460,000 pg/g wet wt reported by Crimmins et al.16).  This strongly suggests that for 
PCBs, notable differences exist between urban and rural areas.  Compared to the U.S. Food and Drug Administration’s 
tolerance level for PCBs in fish, which is two parts per million for edible portions of a fish (U.S. Code of Federal 
Regulations, Title 21, Part 109.3), the PCB concentrations in all fish samples collected in this study were relatively low.  
These results provide valuable information concerning the current background levels of PCBs in catfish in the 
Southeastern United States.  This information will be useful for the determination of intake of these chemicals from this 
particular food source.   
 
Acknowledgements and Disclaimer 
We would like to thank the local fishermen and women of southern Mississippi for their efforts in helping us obtain 
catfish for this study.  Special thanks are also extended to Ken Unice for his statistical insight and help with data quality 
verification.  Funding for the analyses described in this paper was provided in part by Joslyn Manufacturing, Inc and 
Liberty Mutual who are currently involved in litigation associated with dioxins and furans.  Substantial, additional 
funding was provided by ChemRisk, Inc and Vista Analytical Laboratory.  The contents of this paper reflect the opinions 
and views of the authors and do not represent the official views of the USEPA.  The mention of trade names or 
commercial products does not constitute endorsement or recommendation for use. 
 
References 
1. United Nations (UN). (1999). Guidelines for the identification of PCBs and materials containing PCBs. 
2. Agency for Toxic Substances and Disease Registry (ATSDR). (2000) Toxicological profile for polychlorinated biphenyls 
(PCBs). Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service. 
3. Cooper KR, Fiedler H, Bergek S, Andersson R, Hjelt M, Rappe C. (1995) Organohalogen Comp, 26:51-57. 
4. Cooper K, Bergek S, Fiedler H, Hjelt M, Bonner M, Howell F, Rappe C. (1997) Organohalogen Comp, 28:197-202. 
5. Fiedler H, Cooper KR, Bergek S, et al. (1997) Chemosphere, 34:1411-1419. 
6. Fiedler H, Cooper K, Bergek S, et al. (1998) Chemosphere, 37:1645-1656. 
7. Jensen E, Canady R, Bolger PM. (2000) Organohalogen Comp, 47:318-321. 
8. Jensen E, Bolger PM. (2001) Food Addit Contam, 18:395-403. 
9. Schecter A, Päpke O, Ball M, Startin JR, Wright C, Kelly M. Organohalogen Comp 1993; 13:97-100. 
10. Schecter A, Cramer P, Boggess K, Stanley J, Olson JR. Chemosphere 1997; 34:1437-1447. 
11. Schecter A, Cramer P, Boggess K, Stanley J, Päpke O, Olson J, Silver A, Schmitz M. J Toxicol Environ Health, Part A 
2001; 63:1-18. 
12. U.S. Environmental Protection Agency (USEPA). (1992) National study of chemical residues in fish. Washington, D.C.: 
Office of Science and Technology. EPA/823-R-02-008. 
13. U.S. Environmental Protection Agency (USEPA). (2003) Draft exposure and human health risk assessment of 2,3,7,8-
tetrachlorodibenzo-p-dioxin (TCDD) and related compounds, Parts I, II and III.  Washington, D.C.: U.S. Environmental 
Protection Agency, Office of Research and Development, National Center for Environmental Assessment, Exposure 
Assessment and Risk Characterization Group. 
14. Dean S, Hanson T, Murray S.  (2003) Economic Impact of the Mississippi farm-raised catfish industry at the year 2003. 
Publication 2317: Mississippi State University Extension Service, Starkville, MS. 
15. Ferriby LL, Williams ES, Luksemburg WJ, Paustenbauch DJ, Haws LC, Birnbaum LS, Harris MA. (2006) 
Organohalogen Comp, submitted. 
16. Crimmins BS, Doelling Brown P, Kelso DP, Foster GD. (2002) Environ Contam Toxicol, 42:396-404. 
Organohalogen Compounds Vol 68 (2006)
Late Papers
2530


COMPARING POLYCHLORINATED BIPHENYLS IN FARM-RAISED AND WILD- CAUGHT CATFISH FROM SOUTHERN MISSISSIPPI

http://citeseerx.ist.psu.edu/viewdoc/download;jsessionid=8116A0D1247EE43E8B97C4D7431D4563?doi=10.1.1.1074.6020&rep=rep1&type=pdf

COMPARING POLYCHLORINATED BIPHENYLS IN FARM-RAISED AND WILD- CAUGHT CATFISH FROM SOUTHERN MISSISSIPPI

Abstract

Similar works

Full text

Available Versions

CiteSeerX