Bio-Accumulation Factor

Chemicals, which are persistent, toxic and liable to bioaccumulation, are called PTBs. They have primarily local effects. Persistence is the evidence that the substances half-life is greater than two months in water and greater than sue months in soil or sediment. Toxicity is the potential to adversely affect human health and/or the environment. Bioaccumulation is the evidence that the Bio-Accumulation Factor (BAF) is greater than 5000. Up to 1995, there was no clear definition of which products belong to this class [394]. Heavy metals, such as mercury and POPs fall into this category. 

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. 

Guppies exposed to TPhTCl died as soon as a body burden 20 10 nM was reached. Accumulation of TPhTCl can be predicted using kinetic parameters41. The bio-concentration factors of both TBTC1 and TPhTCl via gill intake of goldfishes reached a plateau after 21 days of exposure42. 

KEYWORDS heavy metal, physicochemical factors, soil, rice, bio-accumulation coefficient, Zhejiang... 

BCF Bio concentration Factor sediment-to-fish has accumulation factor 4 NOEC biota to construct SSD in Figure 5... 

A recent study by Vetter et al. [225] showed that 11 polychlorinated bornanes were abundant in different seal species. The most important persistent 7 polychlorinated bornanes with their lUPAC name, different abbreviations, chemical structure, molecular formula, n-octanol/water partition coefficient (log Kqw) and predicted bio concentration factors (BCF and BCFl) in fish are compiled in Table 13. The predicted BCFl values of hepta-, octa- and nonachlorobornanes are between 600,000 and 71,000,000, and the predicted BCF values of these congeners in fish with 5 % lipid range from ca. 32,000 to 3,500,000. Furthermore, in Table 13 the BCF and BCFl values of two polychlorinated bornane congeners (Parlar No. 26 and No. 50) are included, which were calculated by the authors from the measured concentrations in zooplankton and different fish species and the water of a Canadian fresh water lake [226]. It is obvious that the BCF values of the chlorinated bornanes calculated from concentrations in aquatic organisms and water from the environment are by a factor between 1 and ca. 70 greater than the BCFs predicted from the log values. This can be explained in part by bio accumulation. 

The lipid content of the organism is a critical controlling factor of body residues of organic chemicals. Bio concentration studies often provide lipid-corrected results to compensate for this. Therefore, the lipid content of organisms used in bioassays should be reported routinely in all aquatic bioassays, such as bio concentration, bio accumulation, biomagnification, and toxicity studies with organic chemicals. 

Water solubility is one of the major parameters which affect the fate and distribution in the environment. Hydrophobic compounds with high octanol-water partition coefficients tend to bio accumulate. Opperhuizen and Voors [63] have shown that hydrophobicity of PCDEs determines the bio concentration factor of PCDEs and that bioconcentration kinetics of PCDEs resemble those of PCBs. 

Biomagnification of PCDEs in food chains has not been studied much. Their food-chain bio accumulation potential, however, is high because their n-octa-nol-water coefficients are high [59]. Log K(1W values of PCDEs 29 and 77 determined by Opperhuizen and Voors [63] were 5.44 and 5.78, respectively. The bio-concentration factors (ml g1) were 1.5 x 104 and 3.2 x 10 respectively, being similar to those of corresponding PCBs. 

Analogous to the steady-state bioconcentration factor (BCF) and the bio-magnification factor (BMP), the biota-to-sediment-accumulation factor (BSAFsed) and the biota-to-soil-accumulation factor (BSAFsoii) are defined as ... 

To describe bio accumulation, physiological properties of the organism need to be included in addition to a chemical property, such as Ko . Furthermore, many chemicals are known to bioconcentrate to a lesser extent. There is some evidence that this reduced bioaccumulation is due to a size or shape cut-off effect in membrane permeation but an exact value is difficult to set. Other reasons for lower bioconcentration factors are related to biotransformation. It is not possible yet to apply discrete equations for these kind of deviating compounds. Other descriptors will have to be developed and applied that describe the underlying processes for the deviating behaviour. Parameters which relate the size of the molecule, and also parameters that represent differences in potency for biotransformation, will be important. 

Equations (20) - (23) include bio accumulation kinetics, and thus enable us to predict when organisms will attain lethal body burdens. The most important bioaccumulation parameters, and the relationships between the bioaccumulation parameters and physical-chemical and physiological factors, which are required can either be found in the literature or need to be studied. The equations can thus be used to predict if organisms are at risk and will experience adverse effect at a given external exposure concentration. Time will thus be a variable, whereas the external exposure concentration in either water or food will be the given input parameters in this exercise. The equations can also be used to estimate the external concentration which will lead to adverse effects at a given exposure time. Then, external exposure concentration will be a variable, whereas the time required for eliciting effects will be a constant. 

BIO ACCUMULATION when released to water, will bioconcentrate in aquatic organisms which cannot metabolize Oysters (Crassostrea virginica) from oil treated enclosure 2 days exposure, oysters concentration 0.36 pg/g, water concentration 1.9 pg/L, accumulation factor (oysters/water) 190 8 days exposure oysters concentration 0.30 pg/g, water concentration 0.1 pg/L, accumulation factor (oysters/water) 3,000... 

The most persistent nonionic surfactants are based on alkylphenol ethoxy-lates. These ethoxylates are only moderately accumulated by marine fauna. The bio concentration factors in common mussels Mytilus edulis) decreased from 350 to 50 from nonylphenol to nonylphenol tri-ethoxylate [150]. 

Sinclair and Boxall [7] focused their screening method on identifying transformation products of pesticides that were more toxic than their parent. They concluded that the majority of transformation products are less toxic than their parent compound. Exceptions are products that are more hydrophobic and thus more bio accumulative than their precursor, or those with a more potent mode of action. The latter can be explained as follows (1) by the presence of a toxicophore that is formed during transformation of a propesticide into its active product, (2) the pesticide toxicophore remains intact during transformation but hydrophobicity increases, or (3) a different toxicophore is formed during the transformation. On the basis of these rules they developed a flow chart to select appropriate assessment factors that relate the toxicity of the parent compound to the predicted toxicity of the transformation product. This approach is valuable for preliminary hazard assessment and prioritization of further testing but cannot give a quantitative account of the risk associated with transformation products. 

There is now a considerable effort going into studying the factors involved in the variation of mercury concentration in freshwater fish in remote areas (6,24). Such studies will require an examination of often quite small differences in the many factors which contribute to the bio-accumulation of methyl mercury in fish. This will involve the determination of mercury and its forms and other species involved in the transport of mercury through to its uptake as methyl mercury in fish. Clearly, the sampling and analytical techniques, used in studying differences in background areas require to be much more refined than for a comparison of mercury levels in sediments, upstream and downstream from a point source. For instance, the concentration of mercury in water is measured in units of ng/liter (ppt), units one millionth the size of ppm, the units normally used for expressing concentration of mercury in fish and water. 

Bio concentration factor (BCF) The biological accumulation factor associated with direct uptake of a substance from the water in the absence of at r possible intake through the food chaim... 

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