Antoon Opperhuizen

Bioaccumulation of super‐lipophilic chemicals in fish

The influence of increasing molecular size and hydrophobicity on bioaccumulation kinetics in guppies (Poecilia reticulata) was investigated for a series of polychlorinated biphenyls (PCBs) in comparison with other halogenated aromatic compounds. Extremely low clearance rates were characteristic of the higher chlorinated biphenyls and resulted in a linear accumulation in fish. For these compounds, in contrast to more soluble chemicals, direct uptake from water appeared to be less efficient than uptake from contaminated food. Hexabromobenzene, octachlorodibenzo‐p‐dioxin and tetradecachloroterphenyl were not accumulated by living fish. The importance of food‐chain accumulation (biomagnification) versus direct bio‐concentration is discussed in relation to molecular structure and physico‐chemical properties of organic chemicals.

Polychlorinated biphenyl congeners in sediments, plankton, molluscs, crustaceans, and eel in a freshwater lake: Implications of using reference chemicals and indicator organisms in bioaccumulation studies

The concentrations of six polychlorobiphenyl (PCB) congeners in sediments and four classes of biotic species of the aquatic food chain were investigated in a freshwater lake near Amsterdam. Despite the low concentrations of the contaminants in the sediment, significant amounts of PCBs were found in plankton, macro-invertebrates and fish. The composition of the PCB mixtures found in the various organisms cannot be explained in terms of simple partitioning of the PCB congeners between sediment, water, and organisms. In addition to bioconcentration, it is likely that biomagnification via consumption of contaminated food also contributed significantly to the total PCB concentrations. This is most pronounced for the higher trophic food-chain organisms. Studying bioaccumulation processes by monitoring just one type of organism is probably not very suitable, due to the pronounced differences in accumulation patterns demonstrated for the different organisms. In addition, significant differences were found in the accumulation of the six PCBs in the various biotic samples. This indicates that the fate of mixtures of PCBs is determined by the fate of the individual congeners and therefore cannot be monitored in terms of total PCBs concentrations.

Thermodynamics of fish/water and octan-1-ol/water partitioning of some chlorinated benzenes.

The thermodynamic properties of the partitioning of chlorobenzenes between fish and water have been investigated. It is shown that bioconcentration by fish of polychlorobenzenes is accompanied by positive enthalpy and entropy changes. The free energy of this transfer process at room temperature is dominated strongly by the favorable entropy contribution. In contrast, the partitioning of these compounds between octan-1-01 and water is accompanied by negative enthalpy and by small negative or positive entropy changes. These results demonstrate that octan-1-01 is a poor model of the fish lipids and that generally octan-1-ol/water partition coefficients will not give reliable predictions of bioconcentration factors. In particular, the slopes of plots of octan-1-ol/water partition coefficients against bioconcentration factors will not be the same for different compounds. In addition, preliminary results are presented on the extrathermodynamic relationships between molecular structure and enthalpy, entropy, and free energy changes during both accumulation in fish and octan-1-ol/water partitioning of chlorobenzenes.

Differences between retentions of various classes of aromatic hydrocarbons in reversed-phase high-performance liquid chromatography: implications of using retention data for characterizing hydrophobicity

Capacity factors of a series of alkylbenzenes (C1-C10), 12 chlorobenzenes, 9 chlorotoluenes, 17 chloronaphthalenes and 65 chlorobiphenyls have been measured on an octadecylsilica column. Aqueous methanol of four different compositions (80-95% methanol) was used as eluent. Logarithms of capacity factors of all eluites are linearly related to the amount of organic modifier in the eluent. In addition, linear relationships between the solvent strength and the logarithms of capacity factors extrapolated to zero methanol have been revealed. The proportionality factors are dependent on the structures of the eluites. Thermodynamic consideration of the retention processes shows that, within each type of eluite, enthalpy-entropy compensation is found. The compensation temperatures are not significantly different for the various types of eluite. Furthermore, it is shown that the compensation temperatures increase with increasing water content of the eluent. Since the intercepts of the delta G0-delta H0 plots are not equal for the various types of eluite, it was concluded that the distribution processes causing retention of benzene, naphthalene and biphenyl are different. When only the free energies of retention (i.e. the capacity factors) of different types of eluite are compared, no accurate information on the hydrophobicity of the eluites can be obtained if aqueous methanol is used as eluent. Therefore the possibilities for relating or predicting other physico-chemical parameters of the test compounds, such as octan-1-ol-water partition coefficients with isocratic retention data, will be limited.

Biotransformation, bioaccumulation and lethality of 2,8-dichlorodibenzo-p-dioxin: a proposal to explain the biotic fate and toxicity of PCDD's and PCDF's

Abstract 2,8-Dichlorodibenzo-p-dioxin (DCDD) in combination with an inhibitor of metabolism caused lethalithy in Goldfish. DCDD alone was eliminated very rapidly from fish, not treated with the inhibitor, piperonylbutoxide. The latter did not cause toxic effects in a control experiment. It was shown that metabolism decreased the amount of DCDD in Goldfish and prevented DCDD becoming lethal at the concentration used. DCDD, when not metabolized, appeared to be 60 times less toxic than TCDD. A scheme is proposed to explain the biotic fate of PCDDs and structurally related compounds.

Absorption and retention of polydimethylsiloxanes (silicones) in fish: Preliminary experiments†

Hydrophobicity and bioaccumulation potential of linear and cyclic polydimethylsiloxane (PDMS) oligomers were estimated by reversed‐phase liquid chromatography and feeding experiments with guppies (Poecilia reticulata). PDMS concentrations in fish were determined by capillary column gas chromatography and gas chromatography‐mass spectrometry. In contrast to polychlorinated biphenyls (PCBs), only very small amounts of PDMS were retained by the fish after six weeks feeding.

Influence of contaminated particles on the bioaccumulation of hydrophobic organic micropollutants in fish

The influence of contaminated particles on the bioconcentration of hydrophobic chemicals by fish is dependent on the hydrophobicity of the chemicals. This has been shown for polychlorinated benzenes and biphenyls (ranging over three orders of magnitude in octan-1-ol/water partition coefficient) which are sorbed on very low organic carbon content particles. For chemicals with low to moderate hydrophobicity, the amount of the chemical which is sorbed, relative to the amount which is dissolved, determines the influence that contaminated particles have on the uptake of the chemicals by fish. In this present experiment, for lower chlorinated benzenes and biphenyls, the amount dissolved in water are high compared with the amounts which are present in the sorbed state, and the influence of contaminated particles on their uptake by fish is negligible. For more hydrophobic chemicals, which have lower aqueous solubilities, such as penta and hexachlorobenzene, and tri and tetrachlorobiphenyls, contaminated particles can have a much greater influence on the uptake by fish. If the number of contaminated particles is sufficiently high, the low aqueous solubilities, in combination with relatively high rates of desorption or dissolution, enable the particles to act as a source of the hydrophobic chemicals. For extremely hydrophobic chemicals, the rates of dissolution or desorption determine the rates of uptake of the chemical by the fish. Hence, during relatively short periods of exposure, there is no influence of contaminated particles on the bioaccumulation.

Uptake and elimination of polychlorinated arokatic ethers by fish: chloroanisoles

Abstract Uptake rate constants of 10 chloroanisoles by fish are comparable to those of other hydrophobic chemicals. Since fast elimination is found for all congeners the resulting bioconcentration factors are lower than those predicted from their hydrophobicities. Elimination is mainly due to metabolism at the ether bond and the rate constants are independent of hydrophobicity. The presence of the ether bonds does not influence the octan-1-ol/water partition coefficient of the chlorinated aromatic hydrocarbons significantly.

Multi-criteria analysis and risk assessment

Abstract ELECTRE or Concordance Analysis is a French system of multicriteria analysis which is used in economics. The application of ELECTRE for hazard evaluation and risk assessment of chemical substances is suggested, and a first attempt in adapting it for this purpose is presented.

Bioconcentration kinetics of 2,4,5- tri- and 3,3′,4,4′-tetrachlorobiphenyl and 2,4,5- tri- and 3,3′,4,4′-tetrachlorodiphenylether in fish

Abstract The rates of uptake and elimination of 2,4,5 tri- and 3,3′,4,4′-tetrachlorodiphenylether in fish after aqueous exposure are comparable to those of similarly substituted chlorobiphenyls. Mass balance data suggest that 2,4,5- trichlorobiphenyl and 2,4,5- trichlorodiphenylether are metabolized with rates approximately twice as high as the rates of elimination of the parent compounds. The bioconcentration factors of the 3,3′,4,4′-tetrachloro- biphenyl and 3,3′,4,4′- tetrachlorodiphenyl ether are only determined by the hydrophobic nature of these chemicals and are not influenced by metabolism. Congener specific uptake and elimination processes as have been reported for chlorinated dibenzo-p-dioxins and dibenzofurans does not seem to be important for chlorinated biphenyls and diphenylethers.