Correlation of Bioconcentration Factors of Chemicals in Aquatic and Terrestrial 0rganisms.with Their Physical and Chemical Properties Eugene E. Kenaga Health and Environmental Sciences, The Dow Chemical Company, Midland, Mich. 48640
Bioconcentration factors (BCFs) in fat tissues derived from dietary feeding studies in cattle for 23 chemicals and in swine for 7 chemicals were compared with BCFs derived from these chemicals in fish and found to be highly correlated, even though the BCFs were often several orders of magnitude lower in beef fat and swine. The difference in orders of magnitude of BCFs between fish and terrestrial mammals is due to the necessary use of different denominators to calculate BCFs. In spite of this difference in BCF values, absolute residue values in cattle, swine, and fish are similar in magnitude. BCFs in beef fat are negatively correlated with water solubility, and are positively cbrrelated with l-octanol-water partition coefficients and soil organic carbon adsorption ratios as they are in fish. Regression equations were derived which are useful for prediction of any one value from another. BCF values for seven chemicals in cattle and swine were found to be similar in magnitude. Much has been written about the bioconcentration factors (BCFs) of chemicals and their correlation with physical and chemical properties such as water solubilities (WS) ( I , 2 ) , l-octanol-water partition coefficients (Kow)(3-5), and organic carbon soil adsqrption (KoJ (6). This correlation work and derived regression equations have been summarized by Kenaga and Goring (6). The bioconcentration factors in these references are based on aquatic organisms in which the amount of chemical in the fish or parts of fish, or D a p h n i a , snail, mosquito, or other organisms, is divided by the amount in water, presumably under equilibrium conditions. Low water solubility and high lipid solubility can result in BCF numbers for aquatic organisms of over a million in some cases. T h e maximum amount of a chemical in water (aside from t h a t on sediments) is governed by the water solubility of the chemical, which can be very low. For example, 1 lb per acre of DDT in 1 f t of water would not exceed its water solubility of 0.0017 ppm, even though the calculated amount for this depth would be about 0.37 ppm. Water concentrations may appear considerably higher if suspended sediments with absorbed test compounds are present, but scientists seeking a true BCF are careful to exclude such particles or nonsoluble forms of the chemical in their analytical procedures. In soil the situation is quite different. No saturation limit is imposed by solubility. Distribution of chemicals in soil from use application, as in the case of pesticides, is rarely uniform. If applied to soil surfaces, the first few inches usually contain the majority of the compound and the measured concentration depends on the depth of the soil sampled for analysis. Thus, if 1 lb per acre of a chemical such as DDT is uniformly distributed in soil 1, 3, or 12 in. deep, the concentration would be, respectively, 2.20, 0.73, or 0.18 ppm by weight ( 7 ) . Thus, bioconcentration factors for terrestrial animals on treated soil do not have the same basis for a denominator as for aquatic animals in treated water. Because of the difficulty in determining and deciding on a uniform soil residue denominator for BCF, very little data comparable to aquatic organisms are available for terrestrial organisms. I t is recognized that the principal mode of entry of a chemical in water into a fish is mainly through the gills. The comparison of this mode of entry of a chemical with that in the diet of cattle and swine may not seem related. However, the actual absolute 0013-936X/80/0914-0553$01 .OO/O
@ 1980 American Chemical Society
residue concentration values of DDT in aquatic animals (23-194 ppm) are very similar to those reported for terrestrial animals (40-126 ppm) (8) and are shown in this paper to be within an order of magnitude of each other. In order to obtain a more accurately measured denominator for calculation of BCF tests in terrestrial organisms, the data base for dietary feeding studies with large mammals was examined. In the course of setting residue tolerances for EPA registration of pesticide uses on food crops, residue values in the fat of cattle and swine were determined. BCFs from these data were determined by dividing the amount of chemical in the fat tissues by the amount in the diet. The BCFs in fat of cattle (beef fat) were then used for correlation with the same factors used by Kenaga and Goring (6) (BCFs for aquatic organisms in flowing water and terrestrial-aquatic ecosystems, Koc’s,Kow’s,and water solubility).
D a t a Base for B C F s in Cattle a n d Swine Claborn et al. (9) summarized dietary feeding studies with some chlorinated hydrocarbon insecticides, reporting the residue levels in fat tissues of cattle for different periods of exposure (see Table I). Claborn (IO) summarized dietary feeding studies with some chlorinated hydrocarbon insecticides in swine, reporting the residue levels in fat tissues and a t different periods of exposure (see Table 11).These data were used to determine if there was a difference in magnitude in BCFs due to the metabolism represented by cattle (with a rumen) and by swine (without a rumen). In most cases 28 days of feeding on chemically treated diets resulted in a reasonable plateau level of residues in fat in cattle and swine, and was the exposure period chosen as the basis of comparison of BCFs between chemicals. Since the above chemicals represent a limited basis of chemical structure, the data base of the herbicides, acaricides, coccidiostats, and pesticide metabolites from The Dow Chemical Company and other sources was also obtained and used to expand the variety of chemical structures. They are shown under miscellaneous chemicals as the basis for correlation studies in Table I. Correlation o f BCFs in Terrestrial and Aquatic Organisms a n d KUiL’s, K,,’s, a n d W a t e r Solubility By use of the water solubility, K,,,, KO,, and two types of hquatic bioconcentration factor data (BCF(f), flowing water-fish, and BCF(t), terrestrial-aquatic-fish test systems), a data base of 22 chemicals was used for comparison with BCFs in beef fat, all of which are shown in Table 111. On the basis of the above data, there are 30 possible binary regression equations. Of these equations only those from BCFs in beef fat are new. The other equations from these data are similar to those in Kenaga and Goring (6) and so are not given here. Correlations between BCFs in beef fat, aquatic organisms, and the other variables are shown in Table IV and include regression equations, 95% confidence limits of the equations, and the correlation coefficients ( r ) . Results The accumulation of chemicals in the fat of cattle, as shown in Table I, results in residues of chlorinated hydrocarbons Volume
14, Number 5, May 1980
553
Table 1. Accumulation of Chemicals in Fat of Cattle from Dietary Feeding chemical
dietary concn, pprn
aldrin chlordane DDT dieldrin endrin heptachlor methoxychlor lindane
6-chloropicolinic acid clopidol chlorpyrifos
chlorpyrifos-methyl
cyhexatin 2,4-D
dalapon 3,6-dichloropicolinic acid picloram (K salt) ronnel silvex
2,4,5-T
TCDD triclopyr 3,5,6-trichloropyridinol
a
Kidney tissues were over four times that of fat.
aldrin
chlordane DDT dieldrin
endrin heptachlor methoxychlor
554
dietary concn, pprn
ppm in fat (28 days)
BCF (swine fat/diet)
Chlorinated Hydrocarbons 25 60 2.4 10 38 3.8 5 7 1.4 25 8 0.32 10 9 0.9 25 10 0.4 25 44 1.76 10 8 0.8 2.5 6.7 2.68 1.o 1.8 1.8 5 1.5 0.3 2.5 3.2 1.28 10 5.5 0.55 2.5 1.o 0.4 25 0 0
Environmental Science & Technology
BCF (cattle fal/diet)
2.0 3.5 0.5 0.1 0.9 3.0 1.6 0.3
ret
9 9 9 9
9
0.5 0.4
9
0.6 0 0.7 0.4
