Bioaccumulation water/fish partitioning

Thin-layer radiochromatography (radio-TLC) is widely applied for a variety of environmental studies involving radiolabeled pesticides, such as plant uptake from soil, bioaccumulation in fish, dissipation from soil, metabolism in soil, plants, and fish, and environmental fate. The determination of the lipophiUdty of pesticides is important because their bioaccumulation and tendency for degradation and biotransformation are related to lipid solubility. TLC has advantages for lipohilicity studies compared to traditional partition coefficient measurement in an octanol-water system. 

If there is a known adverse effect associated with a chemical, and there is also a potential for widespread exposure, then new information indicating pro-noimced bioaccumulation is reportable. Bioaccumulation in fish beyond five thousand times water concentration, or an n-octanol/water partition coefficient of greater than twenty-five thousand are measures and indications of pronoimced bioaccumulation. 

An especially valuable physicochemical property for chemical assessment is the octanol/water partition coefficient, usually expressed on a logarithmic scale (log Kow). This property correlates with partitioning from water to soil and sediment, as well as bioaccumulation in fish and other aquatic organisms. The ability to estimate log Kow from chemical structure provides a powerful tool to developers of new chemicals to model environmental partitioning and bioaccumulation prior to manufacture or even chemical synthesis (18). Log Kow... 

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 major route for bioaccumulation of hydrophobic organic compounds in aquatic animals is passive diffusion over cell membranes. In fish, the gill epithelia are the predominant port of entry, with less than 40% of uptake across the skin [181]. Since permeability of the membrane is a direct function of the membrane-water partition coefficient and the diffusion coefficient across the membrane interior [182], the bioconcentration factor (logBCF) can be directly correlated with log K0Vl. or log Km%v for compounds with intermediate hydro-phobicity [183,184],... 

Anliker, R. and Moser, P. The limits of bioaccumulation of organic pigments in fish their relation to the partition coefficient and the solubility in water and octanol, Ecotoxicol. Environ. Sal, 13(l) 43-52, 1987. 

Food Chain Bioaccumulation. 3,3 -Dichlorobenzidine is bioconcentrated by aquatic organisms imder experimental eonditions. Whole-fish BCFs of around 500, with equilibration occurring in 96-168 hours, have been published (Appleton and Sikka 1980). In view of the -octanol/water partition coeffieient for... 

The partition coefficient Kq of an organic compound in the 1-octanol/water system is used to assess the bioaccumulation potential and the distribution pattern of drugs and pollutants. The partition coefficient of imidazole and ILs strongly depends on the hydrogen bond formed by these molecules and is less than one due to the high solubility in water. The low value of the 1-octanol/water partition coefficient is required for new substances, solvents, insecticides to avoid bioaccumulation. Kqw is an extremely important quantity because it is the basis of correlations to calculate bioaccumulation, toxicity, and sorption to soils and sediments. Computing the activity of a chemical in human, fish, or animal lipid, which is where pollutants that are hydrophobic will appear, is a difficult task. Thus, it is simpler to measure the 1-octanol/water partition coefficient. This parameter is used as the primary parameter characterizing hydrophobisity. 

Thus, structure-activity relationships developed to estimate levels in biological media based on the partitioning properties of a chemical may not provide accurate information for isophorone. Furthermore, only one bioaccumulation study was available. In this study, which indicated a low potential for bioaccumulation, fish were exposed to isophorone in water rather than in food. From these data, it appears that food chain bioaccumulation may be occurring, and a clearer understanding of the potential for this would aid in determining how levels in the environment affect the food chain and potentially impact on human exposure levels. 

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). 

A considerable data set is available for TCPM, but the number of TCPMe data is limited. The results vary from < 1 pg/kg on a lipid weight basis in some fish samples to 54 mg/kg in white-tailed sea eagles, which shows that TCPM and TCPMe are highly bioaccumulative. A considerable bio concentration of TCPM and TCPMe is also expected on the basis of the octanol-water partition coef-... 

Little data exist on the effects of vinylidene chloride in the aquatic and terrestrial environments. Bioaccumulation is expected to be low based on the low octanol/water partition coefficient and low water solubility. A bioconcentration factor of 4 and a bioaccumulation factor of 6.9 were reported for fish, and a bioaccumulation factor of less than 13 reported for common carp. Because of the rapid volatilization of the chemical from the aquatic and terrestrial environments and the low concentrations found in surface water (microgram per liter range), no significant risk is expected. 

The bioaccumulation potentials of the major components of gasoline range from low to high. Some higher molecular weight components (e.g., naphthalene and substituted naphthalenes) may be taken up by fish and domestic animals and bioconcentrated if they persist in environmental media (Air Force 1989). Alkenes have low log octanol/water partition coefficients (K°w) of about 1 and estimated bioconcentration factors (BCF) of about 10 aromatics have intermediate values (log K° values of 2-3 and BCF values of 20- 200), while O and greater alkanes have fairly high values (log K°w values of about 3-4.5 and BCF values of 100-1,500) (NESCAUM 1989). 

FIGURE 2-29 Schematic representation of a physiologically based kinetic model for bioaccumulation of a chemical that is absorbed through the gills, transported by blood flow, stored in various body tissues, and metabolized by the liver. Such a model requires much more detailed information on the fish than does a partitioning model however, it may be necessary to use this more complex approach for chemicals that are metabolized or excreted by the fish more rapidly than they are exchanged with the water [adapted from Barron (1990). Reprinted with permission. 1990 American Chemical Society]. 

Based on thermodynamic arguments, it has been suggested that octanol does not accurately represents fish lipids [81]. Lipid solubility has been proposed as an additional parameter based on the argument that lipids are more structured than octanol [82]. Partition coefficients with other solvents (triolein-water) and membrane vesicles are measured and related to as well as to BCF [32, 83, 84]. In general, these latter partition coefficients fairly correlate with Kq with systematic lower values at high These differences may lead to an apparently lower BCR The consequences are that overestimates bioaccumulation for very hydrophobic compounds. 

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