Bioconcentration factor determination

Several years ago we demonstrated (Sabijic and Protic 1982b) that the second-order valence molecular connectivity index ( x ) quantitatively correlates with bioconcentration factors (BCFs) of chlorinated hydrocarbons in fish. This result was recently confirmed by two other laboratories (Goverset al. 1984 Koch 1983). The following relationship was established between the index and bioconcentration factors determined by the flow-through method for 20 chlorinated benzenes, biphenyls, diphenyloxides, and similar compounds ... 

Bioconcentration, Bio accumulation and Biomagnification. These aspects are determined by the physicochemical properties of a chemical, an organism s ability to excrete the chemical, the organism s lipid content and its trophic level. Bioconcentration relates to the difference between the environmental concentration and that of the body tissues. A high bioconcentration factor (BCF) predisposes to bioaccnmulation. The upper limit of bioaccnmulation is determined by lipid levels in the organism s tissues. Whether the resultant body burden causes biomagnification in the food chain depends upon the metabolic capabilities of the exposed organism. 

Experimentally measured bioconcentration factors (BCFs), which provide an indication of the tendency of a chemical to partition to the fatty tissue of organisms, have been found to range between 10 and 100 for trichloroethylene in fish (Kawasaki 1980 Kenaga 1980 Neely et al. 1974 Veith et al. 1980). Barrows et al. (1980) estimated a value of 17 for bluegill sunfish. Somewhat lower BCFs were determined by Saisho et al. (1994) for blue mussel (4.52) and killifish (2.71). These numbers are suggestive of a low tendency to bioaccumulate. 

Bioconcentration factors (BCF) were determined in fish samples collected in the field as well as in experimentally exposed fish in a survey conducted in the UK [12]. The experimental BCF of NP was between 90 and 125, suggesting a moderate accumulation in rainbow trout muscle. Environmental BCF values for NP in fish muscle (for gudgeon, roach and chub) were between 10 and 50. For A9PEOi+2, a maximum BCF of475 in chub liver was determined. A series of North Sea fish samples taken offshore contained no detectable APEO metabolites in liver or muscle tissue. 

The determination of the bioconcentration factor (BCF) can be performed in two different ways computationally with quantitative structure activity relationship (QSAR) methods, or from experimental measurements [2], The QSAR methods estimate BCF from the structural or physicochemical properties of the compound, whereas the experimental methods use measured values of uptake and elimination rate constants or concentrations in the steady state. 

Chloroform does not appear to bioconcentrate in higher aquatic organisms, based upon measured bioconcentration factors (BCF) of 6 and 8 for bluegill sunfish (Lepomis macrochirus) (Barrows et al. 1980 Veith et al. 1980). Information from EPA s ASTER (1996) database document a calculated BCF for the fathead miimow of 14, a low value suggesting little potential for bioconcentration in fish. A BCF of 690 experimentally determined for the bioconcentration of chloroform in the green algae Selenastrum capricomutum suggests that the compound has a moderate tendency to concentrate in nonvascular aquatic... 

Dichlorobenzene is expected to bioconcentrate in aquatic organisms. The high octanol-water partition coefficient (K, ) value of 2,455 (Leo et al. 1971) also suggests that 1,4-dichlorobenzene has a moderate to high potential for bioaccumulation. A calculated bioconcentration factor (BCF) of 267 was reported for the fathead minnow (Pimephales promelas) (ASTER 1995). Measured mean BCF values of 370 and 720 were experimentally determined for rainbow trout exposed to water concentrations of... 

In rainbow trout the bioconcentration factor (BCF) was dependent on water concentration (Oliver and Niimi 1983). At low concentrations of 0.10 ng/L a BCF of 5,800 was obtained, compared to a value of 17,000 obtained with higher water concentrations of 3.4 ng/L. Hexachlorobutadiene preferentially accumulates in the liver offish (Pearson and McConnell 1975). In mussels, the BCF was determined to be between 900 and 2,000 (Pearson and McConnell 1975). However, lower values were obtained for algae, crayfish, and bass (160, 60, and 29, respectively) (ERA 1976). The ERA is reviewing new BCF data and has recommended a value of 392 (EPA 1989a). 

Food Chain Bioaccumulation. Bioconcentration factors have been determined for algae, shellfish, and fish and exhibit a wide range (29-17,000) (ERA 1976 Oliver and Niimi 1983 Pearson and McConnell 1975). This wide range may be explained in part by species differences in metabolism or differences in concentrations tested. Studies also indicate that hexachlorobutadiene preferentially accumulates in the livers of fish. Further studies which might explain the wide range of BCF values would be helpful. No information was located regarding the bioaccumulation of hexachlorobutadiene in plants or aquatic organisms. More information is needed to determine the importance of terrestrial/aquatic food chain bioaccumulation as a potential human exposure pathway. 

Exposure Levels in Environmental Media. Environmental monitoring data are not available for soil and air, and the data available for water, sediments, and biota are not sufficient to determine ambient concentrations. These data would be helpful in determining the ambient concentrations of isophorone so that exposure estimates of the general population and the bioconcentration factor of this chemical in aquatic organisms can be made. 

PBBs may also be transported from water to aquatic organisms where bioconcentration may take place. Data on the bioconcentration of PBBs in fish, which were generated in different laboratories, show wide variation. The experimentally determined bioconcentration factor ([BCF] = concentration in fish over concentration in water) for hcxabromobi phenyl (mixtures of unspecified congeners) in the whole body of fathead minnows (Pimephales promelas) was 18,100 in a 32-day exposure (Veith et al. 1979). In fillet of fathead minnow, the estimated BCF was >10,000 (Hesse and Powers 1978). The lipid weight-based BCF values of 4,4 -dibromobiphenyl, 2,4,6-tribromobiphenyl, 2,2, 5,5 -tetrabromobiphenyl, and... 

The ability to predict the behavior of a chemical substance in a biological or environmental system largely depends on knowledge of the physical-chemical properties and reactivity of that compound or closely related compounds. Chemical properties frequently used in environmental assessment include melting/boiling temperature, vapor pressure, various partition coefficients, water solubility, Henry s Law constant, sorption coefficient, bioconcentration factor, and diffusion properties. Reactivities by processes such as biodegradation, hydrolysis, photolysis, and oxidation/reduction are also critical determinants of environmental fate and such information may be needed for modeling. Unfortunately, measured values often are not available and, even if they are, the reported values may be inconsistent or of doubtful validity. In this situation it may be appropriate or even essential to use estimation methods. 

The bioconcentration factor (BCF) is an expensive and difficult test and can be replaced by an estimation of relative lipophilicity of the material, the partition coefficient (log P). This physico-chemical parameter (log P) is determined by measuring the distribution ratio of the material between octanol and water (Droy, 1993 McKim et al., 1985). The logarithm of this ratio is the partition coefficient (log P) however, materials with a log P of <1 or > 6 or 7 are not expected to bioconcentrate. Graphic representation of the relationship between the octanol-water partition coefficient, log P, and predicted bioconcentration, log BCF, has the... 

For regulatory purposes, bioconcentration factors are often used to assess the uptake of both new and existing chemicals by organisms Japan is probably the only country to require experimental determination of bioconcentration by the basic trophic level. Nevertheless, it is sometimes necessary to measure BCFs, and so a brief resume is given here. 

In contrast to log BCF- (bioconcentration factor) log Kow correlations (Meylan et al., 1999), no falloff in log Koc values appears to be observed for highly hydrophobic chemicals, and no biphasic QSARs based on log Kow appear to have been published. This suggests that equilibrium, or at least quasi-equilibrium, is generally achieved within the timescale of the determination of Koc. In addition,... 

The bioconcentration factor can be estimated by exposing fish or other aquatic organisms, for an appropriate time period, to a constant chemical concentration in water by using a flow-through system until a steady-state concentration in the organism is reached. However, for many chemicals - especially very hydrophobic chemicals - a steady-state cannot be reached in an appropriate time. Therefore, the kinetic approach is the only method which can be used for the determination of a real BCF value. 

The real bio concentration factor on a lipid basis (BCFl) of a chemical should be independent of its concentration in the water. In all cases, however, where bioconcentration factors differ by some orders of magnitude for the same chemical, although they have been determined under nearly equal experimental conditions with fish of the same species, strain, sex, age, body weight, and lipid content, it has to be questioned whether a true bioconcentration factor was found. Consequently, all other experimental conditions have to be reexamined. 

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