Arsenic in Fresh-Water Fish M. M. ELLIS, B. A. WESTFALL, AND M. D. ELLIS Medical School, University of Missouri, and U. S. Fisheries Laboratories, Columbia, Mo.
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total weight of the individual fish since it shows the arsenic that would be included in fish meals and other products utilizing the entire fish. The summarized data in Table I indicate the average arsenic content of these fresh-water fish to be about 0.75 p. p. m. as arsenic trioxide on the basis of total wet weight, or 3.54 p. p. m. total dry weight. The average arsenic content of these fresh-water fish i s therefore below that of the marine fishes which have been reported. Holmes and Remington (4) and White (11) list the arsenic content of cod, eels, and mackerel as ranging from 1.5 to 4.1 p. p. m. wet weight; Bhtenberg (10) found that European marine cod contain 26.25 p. p. m. arsenic, dry weight. However, on the basis of total wet weight, our fresh-water fish averaged from one t o five times more arsenic than the common vegetables and fruits (4,8) and from ten to twenty times more arsenic than cows' milk, as determined by Hove, Elvehjem, and Hart (6). The arsenic content of the eviscerated fish-i. e., the portion usually consumed by man as pan fish-was determined separately for 156 fish. The average arsenic found in the eviscerated fish of this group of nine species, including bass, buffalo, carp, suckers, and sunfish, was 0.48 p. p. m., with a maximum of 2.55 p. p. m. wet weight, or 1.85 p. p. m. average and 11.89 p. p. m. maximum, dry weight. These values show the eviscerated portion of these fresh-water fish as definitely richer in arsenic than the common foodstuffs of vegetable origin, and as lower than but approaching marine fish and shellfish in arsenic content.
H E relatively high arsenic content of many marine fishery products has been established by various investigations. A summary of these by Holmes and Remington (4) shows that marine fish contain approximately ten times and marine crustaceans one hundred times the amount of arsenic carried by nonmarine agricultural foodstuffs. I n view of the growing interest in fresh-water fish oils and the general use of fresh-water fish as food for both man and domestic animals, quantitative findings on the arsenic content of 681 fresh-water fish representing fifteen species taken from fifteen inland waters in Florida, Georgia, Alabama, and Texas are presented. Wet weights were obtained in the field within a few minutes after the fish were caught. The several portions of the fish were removed immediately and preserved separately in arsenic-free ethanol, all parts of each fish being used in every case. The alimentary canal was freed of contained material as far as possible before parts were preserved. The smaller fishes were pooled to give approximately 50-gram samples. Usually fish weighing 18 grams or more were assayed individually, the general size range being 75 to 500 grams. All samples were subsequently desiccated a t 95' C. in electric ovens, and constant weights were obtained at 105' C. After fractionation with dry sulfuric ether in standard Soxhlet extractors, both oils and remainders were subjected to the sulfuric-nitric-perchloric wet combustion as recommended by Cassi1 (1) in electrically controlled units with extreme care to keep all operations below 200' C. I n the
IN WHOLE FISH TABLIO I. ARSENICAS ARSENICTRIOXIDE xo, Total Wet Weight, Total D r y Weight, Total
,
Fish Long-nosed a r Gizzard s h a g Small-mouthed buffalo SDotted sucker aernian carp Horned dace Golden shiner Sucker-mouthed pinnow Black bullhead Pickerel T o p minnows Brook silversides .Bluegill Large-mouthed black bass White bass Summary, all individual@ 4
Different Localities Represented"
1
5 9 2 1 10 1 15
of Fish 2 124 5
1 1 3 42 3 1 42 292 28 1 136 1 681
P. P. M. Min. Av. Max. 0.46 0.49 0.53 0.17 0.86 1.94 0.05 0.94 2.78 0.28 0.68 0:56 0.77 0:87 0.72 1.30 2.57 0.36 0 30 o:i7 0:34 o:ie 0.19 0.55 1.65 0.41 0.73 1.08 0.69 0:02 0.53 2:48 0.64 0.02 0.71 2.78
..
..
..
..
..
..
P. P. M.
Min. 1.36 0.64 0.20
..
2181 3.32
..
'o:is
0.78 2.22
0:67
..
0.07
Av.
Max. 1.57 1.78 5.14 11.59 4.05 14.20 1.24 3 13 ... 3160 4.00 5.66 10.43 1.54 1.41 1.50 i:0g 2.59 7.99 3.67 7.98 2.68 4.13 li:k3 2.59 3.54 14.20
...
...
...
Dry-Ether-
Extd., P. P. M. Av. Max.' 1.36 1.48 1.61 0.58 5.11 11.39 0.19 2.61 5.42 0.94 3 39 1:52 1:59 1.74 3.37 5.s5 10.80 1.33 1 44 O:f4 1:lO i:i0 0.65 1.92 6.61 2.00 2.96 5.84 2.60 o:i9 3.44 ii:ii 1.76 0.19 3.04 11.39 Min.
..
... ...
..
...
..
...
Total i n Oil,
P. P. M.
Av. Max. 1.64 2.20 2.86 0.17 0.07 17.96 0.27 26.88 124.98 19.29 1.14 33:63 60.10 73:33 2.18 4.23 5.83 6.31 1.20 0 : i s 11.51 kilo7 1.13 8.66 33.85 7.33 12.03 26.12 4.26 i:i3 24.49 i615:ii 24.84 0.17 11.80 160.71 Min.
...
....
...
....
...
....
Total number of localities from which each species was obtained.
arsenic determinations the apparatus and method as described by Cassil and Wichmann (a) were used, except the substitution of a larger flask carrying 300 cc. of the digest and the lengthening of the ebullition time routinely to 20 minutes, during which period the flask was kept hot with an electric plate. The arsenic values are reported in parts per million as arsenic trioxide. I n the major comparisons, arsenic is given in terms of the
Considering the entire fish, the ether-soluble portion referred to here as the oil was usually much richer in arsenic than the extraction remainder (Table I), the total oil carrying an average of 11.80 p. p. m. and ranging as high as 160.71 p. p. m. (as AszOa). Since Sadolin (9) suggested from his work on cod and herring that the arsenic in these marine fish is largely in the oil, the partition of arsenic was determined in our fresh-water fish. Averaging the entire lot of 681 fish 1331
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INDUSTRIAL AND ENGINEERING CHEMISTRY
regardless of species, the total oil was found to constitute only 2.49 per cent of the total wet weight; and in spite of the high average arsenic content of this oil (11.80 p. p. m.), the oil fraction actually carried only 22.8 per cent of the total arsenic in the fish. I n this group of fresh-water fish, therefore, about one fourth of the total arsenic was either in the oil or was ether soluble and came away with the oil, and three fourths of the arsenic was insoluble in ether and remained in the tissues.
TABLE
11. DISTRIBUTION O F ARSENICA S ARSENICTRIOXIDE IN FOURTEEN LARGE-h1OUTHED BLACKBASS^ Part of Arsenio Content Body, Av. Total Wet A ~ , .total Parts per Million Weight, % 70 Min. Av. Max.
Total fish Wet weight D r y weight Ether-extd. remainder Oil
100.00 28.45 23.52 5.03
100.00 100.00 76.08 23.91
0.56 1.60 1.40 2.53
0.66 2.32 2.14 3.13
1.22 4.20 4.42 15.53
Eviscerated fish Wet weight D r y weight Ether-extd. remainder Oil
92.64 25.84 22.40 3.44
70.88 70.88 58.96 11.92
0.35 1.28 1.45 0.90
0.50 1.81 1.74 2.29
0.88 3.09 3.48 12.96
Total visoera Wet weight D r y weight Ether-extd. remainder Oil
7.35 2.61 1.01 1.59
29.11 29.11 17.11 11.99
1.80 3.90 6.30 3.10
2.61 7.36 11.15 4.98
6.58 22.99 17.44 14.65
?.So
0.48 2.34 1.o.t
21.13 21.13 12.55 8.58
1.37 2.94 5.03 2.35
2.15 5.94 10.29 4.37
5.62 28.86 17.41 7.48
0.86 0.26 0.20 0.05
7.97 7.97 4.66 3.40
2.95 9.63 10.27 9.70
6.06 20.00 14.51 40.51
14.15 36.06 17.61 101.73
Tisoera without liver Wet weight Dry weight Ether-extd. remainder Oil Liver only Wet weight Dry weight Ether-extd. remainder Oil
Average live weight (parts of body pooled in four sets for analyses), 80 grams; taken from natural spring-fed ponds a t Welaka, Fla.
.
Where feasible, the liver masses of the larger fish were assayed separately. I n Table I1 data from fourteen largemouthed black bass chosen because they were visibly “fat” are presented. The total oil of these bass averaged 5 per cent of the total wet weight. The body oil-i. e., the oil from the eviscerated portion-was lowest in arsenic averaging 2.29 p. p. m. The oil from the viscera without the liver averaged 4.37 p. p. m., and the total visceral oil, 4.95 p. p. m. I n the liver oil, however, 40.51 p. p. m. of arsenic were found, and the contribution of the liver to the arsenic content of the total oil which carried 3.13 p. p. m. is obvious. The high arsenic content of the liver oil of these fresh-water bass, with an average of 40.51 p. p. m. and a maximum of 101.73 p. p. m., stands out in contrast against an average of 2.16 p. p. m. and a maximum of 5.1 p. p. m. reported by Holmes and Remington (4)in their samples of American cod liver oil from codfish taken in the north Atlantic region. Because of individual variations the averages of arsenic content in this series of fourteen fresh-water bass are less significant than averages for cod liver oil, as the commercial extraction process has nullified by pooling large numbers of cod livers any variation in arsenic content of individual cod. It is also true that cod liver oil is not extracted commercially with ether, and that the ether might have removed more arsenic from the bass livers than is removed from the cod livers in commercial extractions. However, the high arsenic content of these bass
Vol. 33, No. 10
livers is still evident, for even after removal of the ethersoluble portion, the extracted liver remainder carried an average of 14.51 p. p. m. arsenic, dry weight. Although arsenic was found in all of the fish analyzed, considerable variation in arsenic content between individual fish was noted. These differences in quantity of arsenic were correlated with physiological and ecological factors, but as the species represented by large numbers of individuals showed essentially the same variations in total arsenic (Table I), these factors need not be discussed in this presentation of the range of arsenic content. Individually, however, the quantity of arsenic in the livers and viscera of many of these fresh-water fish approaches or exceeds the arsenic content of marine shrimps which, among the natural foodstuffs reported, are very rich in arsenic (average 15.4 p. p. m., maximum, 30.7 p. p. m. wet weight, 3 ) . I n view of these findings fresh-water fish and particularly their livers and oils must be regarded as potential sources of arsenic in foods and other commercial products utilizing fresh-water fish material. The form in which the arsenic occurs in these fish was not determined. It has been shown that arsenic as found in shrimps is less toxic than arsenic trioxide ( 3 ) ; however, as no biological tests have been made with arsenic as found in fresh-water fish, the toxicity of the arsenic in these fish cannot be evaluated from the data presented here. Since the arsenic content of the oils from these fresh-water fish is consistently higher than the values reported for marine fish oil extracted either experimentally or commercially (4,9 ) , the differences between the oils of marine and freshwater fish noted by Lovern (6) may be significant. This author states that fresh-water fish oils have increased proportions of oleic and linoleic acids, and also palmitoleic, and reduced amounts of the acids of the C ~ and O Czz series as compared with the oils of marine fish; and ( 7 ) that the oils of fresh-water and marine crustacean plankton have the same chemical groupings as the oils of fresh-water and marine fish, respectively. I n addition he showed (7) that fats ingested by fish in their food are deposited largely unchanged. As plankton crustacea and other crustaceans comprise either directly or indirectly a considerable portion of fish food, it would seem that the oils of these animals might be a major source of the arsenic in the fish oils. Arsenic analyses made by us on mass lots of fresh-water amphipods, isopods, and crayfish showed, respectively, 3.25, 4.16, and 5.46 p. p. m. total dry weight; 3.15, 2.77, and 5.49 p, p. m. in the etherextracted remainders; and 4.61, 4.55, and 25.47 p. p. m. in the total oils of these animals. There is, therefore, ample arsenic in these crustaceans which are regularly eaten by fresh-water fish to supply the arsenic found in the fish oils. Whether the difference in chemical grouping in the oils of fresh-water animals would favor greater storage of arsenic in the fresh-water fish livers is not known. Literature Cited (1) Cassil, C. C., J . Assoc. Oficial Aor. Chern., 20, 121-8 (1937). (2) Cassil, C. C., and U’ichmann, H. J., Ibid., 22, 436-45 (1939). (3) Coulson, E. J., Remington, R . E., and Lynch, K. >I., J . Nutrztion, 10, 255-70 (1935). (4) Holmes, A. D., and Remington, R. E.. IND. ENG.CHEM.,26, 573-4 11934). (5) Hove, E., Elvehjem, C. A,, and Hart, E. B., Am. J . Physiol., 124, 205-12 (1938). (6) Lovern, J. A., Biochern. J . , 26, 1978-84 (1932). (7) I b i d . , 29, 847-9 (1935). (8) Myers, C. N., Thorne, B., Gustafson, F., and Kingsbury, J., IND.ENG. CHIM., 25, 624-8 (1933). (9) Sadolin, E., Biochem. Z . , 201, 323-31 (1928). (10) Shtenberg, A. I., Voprosy Pitaniya, 8, 61-74 (1939). (11) White, W. B., IND.ENG.CHEM.,25, 621-3 (1933). \
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