Bioconcentration potential factor

The logarithm of the n-octanol/water partition coefficient (log Kow is a useful preliminary indicator of the bioconcentration potential of a compound. The calculated log K values for 1,3-DNB and 1,3,5-TNB are 1.52 and 1.18 (Deneer et al. 1987), respectively, suggesting a low potential for bioaccumulation. An experimental bioconcentration factor (BCF) of 1,3-DNB for the guppy, Poecilia reticulata, was reported to be 74.13 (Deneer et al. 1987). This BCF indicates that bioaccumulation in aquatic organisms is not an important fate process. BCF data were not located for 1,3,5-TNB. 

Table III shows the levels of aminocarb present in mayfly nymphs sampled from Portage Brook following the 1st application. Aminocarb concentrations found in insects were not high and no breakdown products of the insecticides were found. The peak concentration detected is only 20 ppb (1 h post-application) exposed to a maximum of 2.26 ppb aminocarb in water, representing a concentration factor of oa 9. Residues declined to below detection limits ( < 20 ppb) rapidly afterwards coinciding with the disappearance of residues in stream water indicating that the uptake and bioconcentration potential by the insects for aminocarb were not high. Further work is necessary to confirm this observation since Penny (16) reported that the other insecticide, fenitrothion, is readily bioaccumulated by aquatic insects yielding a concentration factor of about 60.

No experimental data regarding the bioconcentration potential of DNOC in aquatic organisms were located. Based on an estimated bioconcentration factor (BCF) of 40 (Kenaga 1980), the bioconcentration of DNOC in aquatic organisms may not be significant however, based on an estimated log octanol/water partition coefficient [log(K°w)j value of 2.85, DNOC may bioaccumulate in aquatic organisms (Loehr and Krishnamoorthy 1988). Given that DNOC exists predominantly in ionic forms in most natural waters (pH 5-9) and that the compound is markedly toxic to fish, bioconcentration is not expected to be important (EPA 1979). 

Table 13. Chemical name, chemical structure, molecular formula, molecular mass, n-octanol/water partition coefficient (log Kow)> predicted bioconcentration factors (BCFs) of 7 persistent Polychlorinated Bornanes (Toxaphene Components) with high bioconcentration potential, and measured BCFs of Hexachloronorbornadiene, Heptachloronorbornene and of Bromocyclen... 

Spehar et al. [231] investigated the bioconcentration potential of hexachloro-norbornadiene and heptachloronorbornene using 30-day flow-through test with early juvenile fathead minnows Pimephales promelas) with a body weight of 0.12 g and 4% lipid content. The measured mean concentrations of hexa-chloronorbornadiene (HCND) in water was 20.0 3.9 pg and the water concentration of heptachloronorbornene (HepCNB) was 25.9 3.4 pg b. The bioconcentration factors on a wet weight basis after 30 days in this fish species were 6,400 and 11,200, respectively. The bio concentration factors on a lipid basis (BCFl) of HCND and HepCNB after 30 days were 160,000 and 280,000, respectively (see Table 13). 

The mussels bioconcentrated ivermectin from water at 6.9 pg 1 for 6 days under semi-static conditions by a factor on a wet weight basis (BCF ) of 750 (confidence limits 720-790). The lipid content of Mytilus edulis is between 1 and 2 %. The bioconcentration factor an a lipid basis (BCFl) of ivermectin in mussels is therefore between 37,500 and 75,000. That means that the bioconcentration potential of ivermectin is very high and that ivermectin Bj and ivermectin Bib are able to cross membranes of gill-breathing organisms although the cross-section is much bigger than 9.5 A. 

A9.5.1.3 Data on bioconcentration properties of a substance may be available from standardized tests or may be estimated from the structure of the molecule. The interpretation of such bioconcentration data for classification purposes often requires detailed evaluation of test data. In order to facilitate this evaluation two additional appendixes are enclosed. These appendixes describe available methods (Appendix III of Annex 9) and factors influencing the bioconcentration potential (Appendix IV of Annex 9). Finally, a list of standardized experimental methods for determination of bioconcentration and Kow are attached (Appendix V of Annex 9) together with a list of references (Appendix VI of Annex 9). 

Influence of external and internal factors on the bioconcentration potential of organic substances... 

In summary, all of these results illustrate the care that must be exercised in predicting the concentrations of xenobiotics in natural biota from values of bioconcentration factors assuming that uptake takes place exclusively from the water mass. The various factors that may seriously compromise the interpretation of measurements of bioconcentration potential are as follows ... 

BCFs were estimated using EPI Suite s BCFWin program (http //www.epa.gov/oppt/exposure/docs/episuitedl.htm). BCFs were estimated from the log octanol-water partition coefficient (log KoW) and a series of structural correction factors (Meylan et al., 1999). The ITC uses BCFs of >1,000 and > 5,000 to screen chemicals for bioconcentration potential. Chemicals with 1000 < BCF < 5,000 are assigned a medium (M) bioconcentration potential. Chemicals with BCF > 5,000 are assigned a high (H) bioconcentration potential (cf. Table 1). 

The bioaccumulation of a substance into an organism is not an adverse effect hazard in itself. Bioconcentration and bioaccumulation may lead to an increase in body burden which may cause toxic effects due to direct and/or indirect exposure. Bioaccumulative substances characterized by high persistence and toxicity, negligible metabolism and a log ATow between 5 and 8 may represent a concern when widely dispersed in the environment. The potential of a substance to bioaccumulate is primarily related to its lipophilicity. A surrogate measure of this quality is the n-octanol - water partition coefficient (/fow), which is correlated with bioconcentration potential. Therefore, /fow values are normally used as predictors in quantitative structure - activity relationships (QSARs) for bioconcentration factors (BCFs) of organic non-polar substances. 

The estimation of BCF values from log is founded on a relatively profound theoretical basis. However, the predictive power of the respective QSARs should not be overestimated and their limitations must be realized. Principally, QSAR predictions of BCF values correspond to the average accumulation observed with the class of compounds under investigation. The assessment of the potential worst case requires a model that reflects the highest accumulation potential associated with the assumed lipophilicity. The respective bilinear QSAR (Table 4.15) formalizes the empirical rules for estimating log BCF (adjusted for the lipid content of the fish) from log P the bioconcentration potential corresponds to log P. Compounds of high lipophilicity with log P > 6-7 reveal no further increase in BCF. Factors resulting in less bioconcentration are neglected, as the various contributions are not systematically accountable. This procedure is recommended as a conservative approach to a realistic worst-case assessment of the bioaccumulation potential. 

Correlations between the bioaccumulation tendency of organic chemicals in aquatic organisms and 1-octanol/water partition coefficients show a loss of linearity for very hydrophobic compounds. In order to establish the possible cause(s) of this phenomenon, the roles of metabolism, exposure time, membrane permeation, lipid solubility, and bioavailability on the bioconcentration potential of chemicals, are discussed. Data are presented showing their relative importance. It is concluded that, although insufficient experimental data presently exist which can conclusively establish the cause(s), reduced lipid solubility and reduced bioavailability are the most likely factors contributing to the loss of linear correlation for non-metabolizing chemicals. 

BCF factors in fish ranging from 1.08 to 1.85, indicating that bioconcentration of methyl parathion is not an important fate process (Crossland and Bennett 1984). In another study, methyl parathion was added to the water of a carp-rearing pond and the concentration of methyl parathion was measured in water, soil, macrophytes, and carp over a 35-day period. Results showed that methyl parathion accumulated in macrophytes for 1 day and in carp for 3 days following exposure, and then dissipated. The concentrations of methyl parathion decreased in macrophytes by 94% by day 35 and by 98% in carp tissue by day 28 (Sabharwal and Belsare 1986). These data indicate the potential for biomagnification in the food chain is likely to be low because methyl parathion appears to be metabolized in aquatic organisms. 

The bioconcentration factor, although usually related to fish is actually an estimate of the bioaccumulation potential for biota in general. Different organisms may bioconcentrate a given chemical to a lesser or greater degree, however with different chemicals, the relative ranking with respect to bioconcentration will be essentially the same for all species. 

Laskowski [1] has thoroughly reviewed the physico-chemical properties of the SPs, and these are summarized briefly below. SPs are typically of low water solubility (in the low microgram per liter range) and are highly nonpolar (logarithmic octanol water partition coefficients of around 6-7), indicating potential for bioaccumulation. Fish bioconcentration factors (BCF) of several hundred to several thousand are reported however metabolism limits the amount of bioaccumulation,... 

The dominant transport process from water is volatilization. Based on mathematical models developed by the EPA, the half-life for M-hexane in bodies of water with any degree of turbulent mixing (e.g., rivers) would be less than 3 hours. For standing bodies of water (e.g., small ponds), a half-life no longer than one week (6.8 days) is estimated (ASTER 1995 EPA 1987a). Based on the log octanol/water partition coefficient (i.e., log[Kow]) and the estimated log sorption coefficient (i.e., log[Koc]) (see Table 3-2), ii-hexane is not expected to become concentrated in biota (Swann et al. 1983). A calculated bioconcentration factor (BCF) of 453 for a fathead minnow (ASTER 1995) further suggests a low potential for -hcxanc to bioconcentrate or bioaccumulate in trophic food chains. 

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... 

Since the publication of the third edition, additional data have been critically reviewed. New or additional data included in this edition are bioconcentration factors, aquatic mammalian toxicity values, degradation rates, corresponding half-lives in various environmental compartments, ionization potentials, aqueous solubility of miscellaneous compounds, Henry s law constants, biological, chemical, and theoretical oxygen demand values for various organic compounds. Five additional tables have been added Test Method Number Index, Dielectric Values of Earth Materials and Fluids, Lowest Odor Threshold Concentrations of Organic Compoimds in Water, and Lowest Threshold Concentrations of Organic Compounds in Water. 

Potential for bioaccumulation Due to their high Log values and high fat blood partition coefficient, the cyclic siloxanes are likely to be stored into the lipid tissue. However, bioaccumulation is not dependent just on the lipophilicity of the compound, but also in how fast it leaves the contaminated organism. Other indicators of bioaccumulation are the bioconcentration factor (BCF) and bioaccumulation factor (BAF). Values over 5,000 are usually characteristic for the bioaccumulative compounds. D4 has a BCF of 12,400 L/kg [293], D5 of 7,060 L/kg [279], and D6 of 1,160 L/kg [280], values calculated for fish. 

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... 

A bioconcentration factor (BCF) relates the concentration of a chemical in plants or animals to the concentration of that chemical in the medium in which they live. A BCF of about 7 was calculated for 2-hexanone (Lande et al. 1976) using the empirical regression of Neely et al. (1974). This low BCF indicates that bioconcentration is probably not an important fate mechanism for 2-hexanone released into the environment. Biomagnification of 2-hexanone is also not expected to occur to any great extent (Lande et al. 1976). However, no experimental data on the biomagnification potential of 2-hexanone were located to corroborate these assumptions. 

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. 

Experimental bioconcentration factors (BCFs) of 14.1 for o-cresol (Sabljic 1987) and 19.9 for m-cresol (Freitag et al. 1982) indicate that the isomers of cresol will not bioconcentrate in fish and aquatic organisms to any significant extent. Also, cresols are not likely to bioconcentrate in humans. Similar to their behavior in soil, the isomeric cresols are not expected to adsorb to sediment and suspended organic matter, although the potential for this process exists. 

The potential for 2,3-benzofuran to be bioconcentrated by aquatic organisms is likely to be moderate. A bioconcentration factor (BCE) is the ratio of the concentration of a chemical in the tissues of aquatic animals to the concentration of the chemical in the water in which they live. No experimentally measured value for the BCF of 2,3-benzofuran was located, but the octanol-water partition coefficient (K ) of 2,3-benzofuran has been measured as 468 (Leo et al. 1971). The empirical regressions of Neeley et al. (1974) relate the values of and BCF for other compounds, and can be used to estimate that the BCF of 2,3-benzofuran is approximately 40. If this estimate is correct, substantial bioconcentration of 2,3-benzofuran by aquatic organisms would not be expected. 

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