Bioconcentration of superlipophilic persistent chemicals : Octachlorodibenzo-p-dioxin (OCDD) in fish

High bioconcentration of titanium dioxide nanoparticles in Daphnia magna determined by kinetic approach

The environmental risk assessments of titanium dioxide nanoparticles (TiO2 NPs) have drawn wide attention and one of the required critical information is the bioconcentration potentials of these nanoparticles in aquatic organisms. In the present study, the bioconcentration of six commercially available TiO2 NPs with different sizes and surface properties were quantified in a freshwater cladoceran Daphnia magna using kinetic modeling approach. We first calculated the uptake rate constant (ku) and depuration rate constant (ke) of TiO2 NPs and then employed a first-order kinetic model to predict the bioconcentration factors (BCF) at different TiO2 NPs concentrations. Both the ku and ke of TiO2 NPs were significantly affected by the exposure concentration and the nanoparticle property. The predicted BCF values in D. magna of six TiO2 NPs ranged from 2.40×10(5)L/kg to 1.52×10(6)L/kg, and had no clear correlation with the exposure concentration. Large nominal size resulted in a lower BCF of TiO2 NPs at lower exposure concentration. Higher hydrophobicity and Al(OH)3 coating also resulted in a higher BCF. All the six TiO2 NPs in this study were therefore considered very bioaccumulative. More attention should be paid to bioconcentration in the environmental risk assessments of TiO2 NPs, and the physicochemical properties of TiO2 NPs should be taken into account.

Comparing laboratory and field measured bioaccumulation endpoints

An approach for comparing laboratory and field measures of bioaccumulation is presented to facilitate the interpretation of different sources of bioaccumulation data. Differences in numerical scales and units are eliminated by converting the data to dimensionless fugacity (or concentration-normalized) ratios. The approach expresses bioaccumulation metrics in terms of the equilibrium status of the chemical, with respect to a reference phase. When the fugacity ratios of the bioaccumulation metrics are plotted, the degree of variability within and across metrics is easily visualized for a given chemical because their numerical scales are the same for all endpoints. Fugacity ratios greater than 1 indicate an increase in chemical thermodynamic activity in organisms with respect to a reference phase (e.g., biomagnification). Fugacity ratios less than 1 indicate a decrease in chemical thermodynamic activity in organisms with respect to a reference phase (e.g., biodilution). This method provides a holistic, weight-of-evidence approach for assessing the biomagnification potential of individual chemicals because bioconcentration factors, bioaccumulation factors, biota-sediment accumulation factors, biomagnification factors, biota-suspended solids accumulation factors, and trophic magnification factors can be included in the evaluation. The approach is illustrated using a total 2393 measured data points from 171 reports, for 15 nonionic organic chemicals that were selected based on data availability, a range of physicochemical partitioning properties, and biotransformation rates. Laboratory and field fugacity ratios derived from the various bioaccumulation metrics were generally consistent in categorizing substances with respect to either an increased or decreased thermodynamic status in biota, i.e., biomagnification or biodilution, respectively. The proposed comparative bioaccumulation endpoint assessment method could therefore be considered for decision making in a chemicals management context.

Influence of dispersants on bioconcentration factors of seven organic compounds with different lipophilicities and structures

Seven compounds with different lipophilicities and structures--1,3,5-trichlorobenzene, pentachlorobenzene, acenaphthylene, 1,4-dimethyl-2-(1-methylphenyl)benzene, 4-ethylbiphenyl, 4,4'-dibromobiphenyl, and 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane--were subjected to bioconcentration tests in carp at concentrations below the water solubilities of the compounds in the presence or absence of a dispersant (either an organic solvent or a surfactant). The bioconcentration factors (BCFs) of the compounds were on the order of 10(2)-10(4). The BCF values remained in the range of 15-49% for all the compounds, whether or not a dispersant was present, i.e., the BCF values in the presence of an organic solvent or a surfactant at a concentration below the critical micelle concentration were not significantly smaller than the BCF values in the absence of the solvent or surfactant. This result indicates that the dispersants had no influence on the evaluation of the bioconcentration potential of these test substances.

Predicting bioconcentration factors (BCFs) of polychlorinated bornane (Toxaphene) congeners in fish and comparison with bioaccumulation factors (BAFs) in biota from the aquatic environment

Polychlorinated bornanes, the main components of Toxaphene, are bioconcentrated in aquatic organisms to a high extent. However, up to this time no bioconcentration tests with individual chlorinated bornanes in aquatic organisms have been performed. Therefore, the bioconcentration factors (BCFs) of seven selected persistent chlorinated bornane congeners which are regularly found in aquatic organisms, were predicted from their n-octanol/water partition coefficients (log Kow). Furthermore, these BCF values were compared with the measured bioaccumulation factors (BAFs) in zooplankton and different fish species from the aquatic environment.

Bioaccumulation of contaminants in fish

The term bioaccumulation is defined as uptake, storage, and accumulation of organic and inorganic contaminants by organisms from their environment. Bioaccumulation therefore results from complex interactions between various routes of uptake, excretion, passive release, and metabolization. For fish, the bioaccumulation process includes two routes of uptake: aqueous uptake of water-borne chemicals, and dietary uptake by ingestion of contaminated food particles. The contribution to bioaccumulation that results from aqueous exposure and is taken up by the gills is called bioconcentration. The contribution to bioaccumulation resulting from dietary exposure via uptake by intestinal mucosa is termed biomagnification. In both cases, important co-determinants for bioaccumulation are the various elimination mechanisms. This chapter presents a short historical survey of the problem of bioaccumulation with particular reference to fish and of the various approaches to study bioaccumulation. This is followed by an overview of our present knowledge about basic physico-chemical determinants that either increase or reduce the bioaccumulation potential of various chemicals, and about the physiological basis of gills, blood circulation and intestines, as far as they are crucial for our understanding of uptake and accumulation. Finally, selected quantitative data and modelings of bioaccumulation in fish will be discussed, with regard to such problems as the relative importance of aqueous and dietary uptake.

Effects of dissolved organic matter (DOM) on the bioconcentration of organic chemicals in aquatic organisms--a review

Current knowledge on the effects of dissolved organic matter (DOM) on the bioconcentration of organic chemicals in aquatic animals (water fleas, mussels, amphipods and fish) is summarized. A graphical representation of the available data gives an overview of the magnitude of the observed effects. Most of the studies have shown decreases in bioconcentration in the presence of DOM (2 to 98% relative to DOM-free controls). However, at low DOM levels, up to 10 mg/L, also enhancements of bioconcentration due to DOM, ranging from 2 to 303% have been reported. Generally, the change in BCFW (Bioconcentration factor on a wet weight basis) per mg/L DOC was most pronounced at low levels of DOC. The data also show that DOM from different sources with different characteristics and quality can lead to substantial variations in the bioconcentration of organic compounds at comparable levels of DOC. While decreases in bioconcentration have generally been attributed to a lack of bioavailability of DOM-bound chemical, no mechanisms have been proposed to explain increased uptake of xenobiotics caused by DOM.

Octanol/water partition coefficients for environmentally important organic compounds : Test of three RP-HPLC-methods and new experimental results

Partition coefficients PO,w ((i)) describing the distribution of a solute i onto coexisting phases of 1-octanol and water are needed in a large variety of applications. They can be measured directly by HPLC as long as log PO,w ((i))≧ 3.5. For more hydrophobic substances, several experimental procedures have been proposed in the literature. The reliability of those methods is questionable. Therefore, in the present work, PO,w ((i)) is determined experimentally by three HPLC methods using reversed-phase HPLC [1]. Results from different procedures are compared critically. The method of Braumann [2] proved to be superior over the OECD-guidelines [3]. It was therefore applied to determine octanol/water partition coefficients for 23 substances at 25 °C. For eight of those substances (4-methylindole; 9-(hydroxymethyl)anthracene; N-ethylcarbazol; ethylcyclohexane; trans-2-octene; l,l-dimethyl-(ethy])cyclohexane; heptylbenzene; 4-dodecyl-l,3-benzenediol) no experimentally determined number for PO,w ((i)) has been published before.

Modelling the accumulation of hydrophobic organic chemicals in earthworms : Application of the equilibrium partitioning theory

In this paper a method is developed which can be used to estimate the body burden of organic hydrophobic chemicals in earthworms. In contrast to the equilibrium partitioning theory, two routes of uptake are incorporated: uptake from interstitial water and dietary uptake. Although many uncertainties still remain, calculations show that for earthworms steady state body burdens are mainly determined by uptake from interstitial water. Under most circumstances, the contribution of dietary uptake is small, except for hydrophobic chemicals (log Kow > 5) in soils with a high organic matter (OM) content of ≈ 20 %. Under those conditions, estimates of the steady state body burden calculated with the equilibrium partitioning model, in which only uptake from interstitial water is taken into account, might result in a small underestimation of the real body burden of chemicals in earthworms.

Compound dependence of the relationship log K(ow) and log BCF L : A comparison between chlorobenzenes (CBs) for rainbow trout and polycyclic aromatic hydrocarbons (PAHs) forDaphnia

Linear relatinships between log bioconcentration factor (BCF) and log K(ow) for a variety of compounds have been reported many times in the literature. Analysis of the thermodynamics of the two partition processes has, however, shown that they are not analogous and that linear relationships can be expected to have different slopes for structurally unrelated compounds. In this study a set of literature lipid normalized BCF (BCFL) values of chlorbenzenes (CBs) for rainbow trout and polycyclic aromatic hydrocarbons (PAHs) forDaphnia was put together with literature Kow values. The slopes of the regression lines for log BCFL versus log Kow for the two groups of compounds proved to differ significantly in a statistical test using analysis of variance (ANOVA). The difference, which is of significance for estimates of BCFs in environmental modelling of these types of compounds, is explained by the differences in chemical structure of the two groups of compounds.