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Mechanistic modelling of toxicokinetic processess within Mytiophyllum
Heine, S. ; Schmitt, W. ; Schaffer, A. ; Gorlitz, G. ; Buresova, H. ; Arts, G. ; Preuss, T.G. - \ 2015
Chemosphere 120 (2015). - ISSN 0045-6535 - p. 292 - 298.
partition-coefficients - cuticular membranes - risk-assessment - aquatic macrophytes - water permeability - plant cuticles - sensitivity - diffusion - chemicals - linuron
Effects of chemicals are, in most cases, caused by internal concentrations within organisms which rely on uptake and elimination kinetics. These processes might be key components for assessing the effects of time-variable exposure of chemicals which regularly occur in aquatic systems. However, the knowledge of toxicokinetic patterns caused by time-variable exposure is limited, and gaining such information is complex. In this work, a previously developed mechanistic growth model of Myriophyllum spicatum is coupled with a newly developed toxicokinetic part, providing a model that is able to predict uptake and elimination of chemicals, as well as distribution processes between plant compartments (leaves, stems, roots) of M. spicatum. It is shown, that toxicokinetic patterns, at least for most of the investigated chemicals, can be calculated in agreement with experimental observations, by only calibrating two chemical- specific parameters, the cuticular permeability and a plant/water partition coefficient. Through the model-based determination of the cuticular permeabilities of Isoproturon, Iofensulfuron, Fluridone, Imazamox and Penoxsulam, their toxicokinetic pattern can be described with the model approach. For the use of the model for predicting toxicokinetics of other chemicals, where experimental data is not available, equations are presented that are based on the log (Poct/wat) of a chemical and estimate parameters that are necessary to run the model. In general, a method is presented to analyze time-variable exposure of chemicals more in detail without conducting time and labour intensive experiments.
Equilibrium and kinetic modeling of contaminant immobilization by activated carbon amended to sediments in the field
Rakowska, M.I. ; Kupryianchyk, D. ; Koelmans, A.A. ; Grotenhuis, J.T.C. ; Rijnaarts, H.H.M. - \ 2014
Water Research 67 (2014). - ISSN 0043-1354 - p. 96 - 104.
waterbodems - verontreinigde sedimenten - actieve kool - polycyclische koolwaterstoffen - water bottoms - contaminated sediments - activated carbon - polycyclic hydrocarbons - polycyclic aromatic-hydrocarbons - polychlorinated biphenyl sorption - dissolved organic-matter - marine sediment - partition-coefficients - aqueous solubilities - black carbon - amendment - polyoxymethylene - remediation
Addition of activated carbons (AC) to polluted sediments and soils is an attractive remediation technique aiming at reducing pore water concentrations of hydrophobic organic contaminants (HOCs). In this study, we present (pseudo-)equilibrium as well as kinetic parameters for sorption of a series of PAHs and PCBs to powdered and granular activated carbons (AC) after three different sediment treatments: sediment mixed with powdered AC (PAC), sediment mixed with granular AC (GAC), and addition of GAC followed by 2 d mixing and subsequent removal ('sediment stripping'). Remediation efficiency was assessed by quantifying fluxes of PAHs towards SPME passive samplers inserted in the sediment top layer, which showed that the efficiency decreased in the order of PAC > GAC stripping > GAC addition. Sorption was very strong to PAC, with Log KAC (L/kg) values up to 10.5. Log KAC values for GAC ranged from 6.3-7.1 and 4.8-6.2 for PAHs and PCBs, respectively. Log KAC values for GAC in the stripped sediment were 7.4-8.6 and 5.8-7.7 for PAH and PCB. Apparent first order adsorption rate constants for GAC (kGAC) in the stripping scenario were calculated with a first-order kinetic model and ranged from 1.6 × 10-2 (PHE) to 1.7 × 10-5 d-1 (InP). Sorption affinity parameters did not change within 9 months post treatment, confirming the longer term effectiveness of AC in field applications for PAC and GAC.
A possible simplification of the Goss-modified Abraham solvation equation
Noort, P.C.M. van - \ 2013
Chemosphere 93 (2013)9. - ISSN 0045-6535 - p. 1742 - 1746.
partition-coefficients - organic-compounds - gas-phase - water - thermodynamics - temperature - equilibrium - descriptors - solutes - model
Abraham solvation equations find widespread use in environmental chemistry and pharmaco-chemistry. Recently Goss proposed a modified Abraham solvation equation. For various partitioning processes, the present study investigates the consequences for the fit when the Abraham solvation parameter V is left out of this modified solvation equation. For air-organic solvent partition, the Abraham solvation parameter V can be omitted from the Goss-modified Abraham solvation equation without any loss of statistical quality. For air–water partitioning, organic biphasic system partitioning, as well as water-organic solvent partitioning, omitting the V parameter from the Goss-modified Abraham solvation equation leads to only a small deterioration of statistic quality.
Estimation of abraham solvation equation coefficients for hydrogen bond formation from abraham solvation parameters for solute activity and basicity
Noort, P.C.M. van - \ 2013
Chemosphere 90 (2013)2. - ISSN 0045-6535 - p. 344 - 348.
free-energy relationship - 298 k - partition-coefficients - organic-compounds - ionic liquids - lfer analysis - solubility - vapors - gases - water
Abraham solvation equations find widespread use in environmental chemistry and pharmaco-chemistry. The coefficients in these equations, which are solvent (system) descriptors, are usually determined by fitting experimental data. To simplify the determination of these coefficients in Abraham solvation equations, this study derives equations, based on Abraham solvation parameters for hydrogen acidity and basicity of the solvents involved, to estimate the value of the coefficients for hydrogen bond formation. These equations were applied to calculate Abraham solvation parameters for hydrogen acidity and basicity for polyoxymethylene, polyacrylate, sodium dodecylsulfate, some ionic liquids, alkanoyl phosphatidyl cholines, and lipids for which fitted values for Abraham coefficients for hydrogen bond formation were available
In situ sorption of hydrophobic organic compounds to sediment amended with activated carbon
Kupryianchyk, D. ; Rakowska, M.I. ; Grotenhuis, J.T.C. ; Koelmans, A.A. - \ 2012
Environmental Pollution 161 (2012)2. - ISSN 0269-7491 - p. 23 - 29.
polycyclic aromatic-hydrocarbons - polychlorinated biphenyl sorption - environmental black carbon - contaminated sediments - partition-coefficients - marine-sediments - phenanthrene sorption - aqueous solubilities - accumulation factors - native pahs
Contaminated sediments can be remediated by adding carbonaceous materials (CM), e.g. activated carbons (AC). Here, we analyze published datasets from AC amendment trials to identify variation in the effectiveness of AC in reducing porewater concentrations of hydrophobic organic contaminants (HOCs). The analysis uses a model that separates the contribution of HOC sorption to AC by parameterzing the sorption contributions by amorphous organic matter and black carbon (BC). It appears that sorption to BC increased with LogKOW, whereas sorption to AC showed a relatively narrow range of affinity properties with a median Freundlich LogKF,AC value of 7.2 (µg/kgAC)/(µg/L)n (IQR = 7.0–7.5) for polychlorinated biphenyls (PCBs) and 8.6 (IQR = 8.3–8.8) for polycyclic aromatic hydrocarbons (PAHs). Estimated Freundlich exponents were nF,AC = 0.74 for PCBs and 0.82 for PAH. Sorption to AC was stronger than to BC for chemicals below LogKOW = 6.3–6.6. For HOC risk reduction this is favorable, because chemicals with low KOW show generally higher bioavailable concentrations.
Tutorial on physiologically based kinetic modeling in molecular nutrition and food research
Rietjens, I. ; Louisse, J. ; Punt, A. - \ 2011
Molecular Nutrition & Food Research 55 (2011)6. - ISSN 1613-4125 - p. 941 - 956.
naturally-occurring alkenylbenzenes - post-labeling analysis - vitro toxicity data - in-vitro - risk-assessment - dna-adducts - pharmacokinetic models - partition-coefficients - pbpk model - pharmacokinetic/pharmacodynamic model
Studies in the field of molecular nutrition and food research often aim at identifying effects of bioactive ingredients on living organisms. When data from human studies are difficult to obtain, effects are often studied in relevant animal or cellular in vitro models. This poses the need for adequate extrapolation from the in vitro to the in vivo situation, from high-dose levels to realistic low-dose levels and from experimental animals to humans. Furthermore, effects of genetic polymorphisms or lifestyle factors may have to be taken into account. Physiologically based kinetic (PBK) modeling provides a means to support these kinds of extrapolations. The present paper illustrates the basic concepts of PBK modeling. PBK modeling includes six steps: (i) definition of the conceptual model, (ii) translation into a mathematical model, (iii) defining parameter values, (iv) solving the equations, (v) evaluation of model performance and (vi) making predictions. The paper provides an overview of these basic steps and presents examples to illustrate how PBK modeling can be applied. This reveals that PBK modeling provides an important tool in the field of the 3Rs aiming at Replacement, Reduction and Refinement of animal studies and may also be a useful tool for risk assessment
Evaluation of research activities and research needs to increase the impact and applicability of alternative testing strategies in risk assessment practice
Punt, A. ; Schiffelers, M.J.W.A. ; Horbach, J. ; Sandt, J.J.M. van de; Groothuis, G.M.M. ; Rietjens, I. ; Blaauboer, B.J. - \ 2011
Regulatory Toxicology and Pharmacology 61 (2011)1. - ISSN 0273-2300 - p. 105 - 114.
vitro toxicity data - biokinetic pbbk model - eu reach legislation - stem-cell test - in-vitro - pharmacokinetic models - estragole bioactivation - developmental toxicity - partition-coefficients - reproductive toxicity
The present paper aims at identifying strategies to increase the impact and applicability of alternative testing strategies in risk assessment. To this end, a quantitative and qualitative literature evaluation was performed on (a) current research efforts in the development of in vitro methods aiming for alternatives to animal testing, (b) the possibilities and limitations of in vitro methods for regulatory purposes and (c) the potential of physiologically-based kinetic (PBK) modeling to improve the impact and applicability of in vitro methods in risk assessment practice. Overall, the evaluation showed that the focus of state-of-the-art research activities does not seem to be optimally directed at developing in vitro alternatives for those endpoints that are most animal-demanding, such as reproductive and developmental toxicity, and carcinogenicity. A key limitation in the application of in vitro alternatives to such systemic endpoints is that in vitro methods do not provide so-called points of departure, necessary for regulators to set safe exposure limits. PBK-modeling could contribute to overcoming this limitation by providing a method that allows extrapolation of in vitro concentration-response curves to in vivo dose-response curves. However, more proofs of principle are required.
Toxicokinetic variation in 15 freshwater arthropod species exposed to the insecticide chlorpyrifos
Rubach, M.N. ; Ashauer, R. ; Maund, S.J. ; Baird, D.J. ; Brink, P.J. van den - \ 2010
Environmental Toxicology and Chemistry 29 (2010)10. - ISSN 0730-7268 - p. 2225 - 2234.
partition-coefficients - aquatic ecosystems - pulsed exposure - gammarus-pulex - lipid-content - bioconcentration - sensitivity - substances - elimination - pesticides
Recent advances in modeling the processes of the toxicity of chemicals—toxicokinetics (TK) and toxicodynamics (TD)—are improving environmental risk assessment (ERA) through prediction of effects from time-varying exposure. This has been achieved by linking chemical fate and toxicological effects mechanistically, based on internal concentrations, through the tissue residue approach. However, certain questions remain: for example, how do TK and TD differ among species and how does this relate to differences in species sensitivity? In a series of experiments, we studied the TK of [14C]chlorpyrifos in 15 freshwater arthropod species, two of which were studied in juvenile and adult life stages. Uptake (kin) and elimination (kout) rate constants were fitted using a one-compartment single first-order kinetic model. The application of two complementary parameter estimation methods facilitated the calculation of bioconcentration factors (BCF) with prediction intervals and 95% depuration times (t95) for all tested species. Extremely slow elimination was observed in some species as well as high overall variation in kin, kout, BCF, and t95 across the tested aquatic arthropod species. This variation has implications for the development of TKTD approaches in ERA, including assessing fluctuating exposure concentrations and the interpretation of observed toxicity responses in the laboratory and in the field.
Health monitoring of plants by their emitted volatiles: A model to predict the effect of Botrytis cinerea on the concentration of volatiles in a large-scale greenhouse
Jansen, R.M.C. ; Hofstee, J.W. ; Wildt, J. ; Vanthoor, B.H.E. ; Verstappen, F.W.A. ; Takayama, K. ; Bouwmeester, H.J. ; Henten, E.J. van - \ 2010
Biosystems Engineering 106 (2010)1. - ISSN 1537-5110 - p. 37 - 47.
semivolatile organic-compounds - partition-coefficients - voc emissions - monoterpenes - temperature - dependence - indicator - sorption - stress - system
This paper describes a model to calculate the concentrations of (Z)-3-hexenol, a-pinene, a-terpinene, ß-caryophyllene, and methyl salicylate in a greenhouse on the basis of their source and sink behaviour. The model was used to determine whether these volatile organic compounds (VOCs) can be used to indicate Botrytis cinerea infection in a large-scale tomato production greenhouse with a volume of 5 × 104 m3 containing 2.2 × 104 plants. Seven experiments were done to parameterise the model for these VOCs. Based on model predictions, the B. cinerea-induced increase in concentration of methyl salicylate is detectable in a large-scale tomato production greenhouse when: (a) windows are fully opened, and (b) the increase continues for at least 1 h, and (c) 5% of the plants are infected. The B. cinerea-induced increase in concentration of methyl salicylate is also detectable when: (a) windows are closed, and (b) the increase continues for at least 6 h, and (c) 5% of the plants are infected. The B. cinerea-induced increase in concentration of (Z)-3-hexenol is detectable under all conditions studied. However, it is expected that besides infected plants, many additional sources of (Z)-3-hexenol exist including plant debris and nearby field crops especially upon harvest or stress. The B. cinerea-induced increases in concentration of a-pinene, a-terpinene and ß-caryophyllene are probably undetectable in a large-scale tomato production greenhouse. Therefore, it is recommended to focus on the detection of methyl salicylate to indicate B. cinerea infections in large-scale tomato production greenhouses.
In silico methods for physiologically based biokinetic models describing bioactivation and detoxification of coumarin and estragole: Implications for risk assessment
Rietjens, I. ; Punt, A. ; Schilter, B. ; Scholz, G. ; Delatour, T. ; Bladeren, P.J. van - \ 2010
Molecular Nutrition & Food Research 54 (2010)2. - ISSN 1613-4125 - p. 195 - 207.
human liver-microsomes - variant cyp2a6 alleles - pharmacokinetic models - partition-coefficients - species-differences - safety assessment - cytochrome-p450 cyp2a6 - 7-hydroxylase activity - metabolism - rats
In chemical safety assessment, information on adverse effects after chronic exposure to low levels of hazardous compounds is essential for estimating human risks. Results from in vitro studies are often not directly applicable to the in vivo situation, and in vivo animal studies often have to be performed at unrealistic high levels of exposure. Physiologically based biokinetic (PBBK) modeling can be used as a platform for integrating in vitro metabolic data to predict dose- and species-dependent in vivo effects on biokinetics, and can provide a method to obtain a better mechanistic basis for extrapolations of data obtained in experimental animal studies to the human situation. Recently, we have developed PBBK models for the bioactivation of the alkenylbenzene estragole to its DNA binding ultimate carcinogenic metabolite 1-sulfooxyestragole in both rat and human, as well as rat and human PBBK models for the bioactivation of coumarin to its hepatotoxic o-hydroxyphenylacetaldehyde metabolite. This article presents an overview of the results obtained so far with these in silico methods for PBBK modeling, focusing on the possible implications for risk assessment, and some additional considerations and future perspectives.
Dynamic speciation analysis of atrazine in aqueous latex nanoparticle dispersions using solid phase microextraction (SPME)
Benhabib, K. ; Town, R.M. ; Leeuwen, H.P. van - \ 2009
Langmuir 25 (2009)6. - ISSN 0743-7463 - p. 3381 - 3386.
polycyclic aromatic-hydrocarbons - partition-coefficients - bioavailable concentrations - organic-matter - humic acids - kinetics - complexes - sediment - sorption - contaminants
Solid phase microextraction (SPME) is applied in the dynamic speciation analysis of the pesticide atrazine in an aqueous medium containing sorbing latex nanoparticles. It is found that the overall rate of extraction of the analyte is faster than in the absence of nanoparticles and governed by the coupled diffusion of free and particle-bound atrazine toward the solid/sample solution interface. In the eventual equilibrium the total atrazine concentration in the solid phase is dictated by the solid phase/water partition coefficient (Ksw) and the concentration of the free atrazine in the sample solution. These observations demonstrate that the nanoparticles do not enter the solid phase. The experimental data show that the rate of release of sorbed atrazine from the latex particles is fast on the effective time scale of the microextraction process. A lability criterion is derived to quantitatively describe the relative rates of these two processes. All together, the results indicate that SPME has a strong potential for dynamic speciation analysis of organic compounds in media containing sorbing nanoparticles
Promises and pitfalls of Quantitative Structure-Activity Relationship approaches for predicting metabolism and toxicity
Zvinavashe, E. ; Murk, A.J. ; Rietjens, I.M.C.M. - \ 2008
Chemical Research in Toxicology 21 (2008)12. - ISSN 0893-228X - p. 2229 - 2236.
structure-property relationships - aquatic toxicity - qsar models - applicability domain - cytochromes p450 - environmental-pollutants - tetrahymena-pyriformis - partition-coefficients - industrial pollutants - pimephales-promelas
The description of quantitative structure¿activity relationship (QSAR) models has been a topic for scientific research for more than 40 years and a topic within the regulatory framework for more than 20 years. At present, efforts on QSAR development are increasing because of their promise for supporting reduction, refinement, and/or replacement of animal toxicity experiments. However, their acceptance in risk assessment seems to require a more standardized and scientific underpinning of QSAR technology to avoid possible pitfalls. For this reason, guidelines for QSAR model development recently proposed by the Organization for Economic Cooperation and Development (OECD) [ Organization for Economic Cooperation and Development (OECD) (2007) Guidance document on the validation of (quantitative) structure¿activity relationships [(Q)SAR] models. OECD Environment Health and Safety Publications: Series on Testing and Assessment No. 69, Paris] are expected to help increase the acceptability of QSAR models for regulatory purposes. The guidelines recommend that QSAR models should be associated with (i) a defined end point, (ii) an unambiguous algorithm, (iii) a defined domain of applicability, (iv) appropriate measures of goodness-of-fit, robustness, and predictivity, and (v) a mechanistic interpretation, if possible [ Organization for Economic Cooperation and Development (OECD) (2007) Guidance document on the validation of (quantitative) structure¿activity relationships [(Q)SAR] models. The present perspective provides an overview of these guidelines for QSAR model development and their rationale, as well as the promises and pitfalls of using QSAR approaches and these guidelines for predicting metabolism and toxicity of new and existing chemicals.
Quantum chemistry based QSAR prediction and priority setting for toxicity of nitrobenzenes on EINECS list
Zvinavashe, E. ; Murk, A.J. ; Vervoort, J.J.M. ; Soffers, A.E.M.F. ; Freidig, A. ; Rietjens, I.M.C.M. - \ 2006
Environmental Toxicology and Chemistry 25 (2006)9. - ISSN 0730-7268 - p. 2313 - 2321.
nitrobenzene derivatives - partition-coefficients - qsar - prediction - information - validation - pollutants - indexes
Fifteen experimental literature data sets on the acute toxicity of substituted nitrobenzenes to algae (Scenedesmus obliquus, Chlorella pyrenoidosa, C. vulgaris), daphnids (Daphnia magna, D. carinata), fish (Cyprinus carpio, Poecilia reticulata), protozoa (Tetrahymena pyriformis), bacteria (Phosphobacterium phosphoreum), and yeast (Saccharomyces cerevisiae) were used to establish quantum chemistry based quantitative structure¿activity relationships (QSARs). The logarithm of the octanol/water partition coefficient, log Kow, and the energy of the lowest unoccupied molecular orbital, Elumo, were used as descriptors. Suitable QSAR models (0.65 <r2 <0.98) to predict acute toxicity of substituted mononitrobenzenes to protozoa, fish, daphnids, yeast, and algae have been derived. The log Kow was a sufficient descriptor for all cases, with the additional Elumo descriptor being required only for algae. The QSARs were found to be valid for neutral substituted mononitrobenzenes with no -OH, -COOH, or -CN substituents attached directly to the ring. From the 100,196 European Inventory of Existing Commercial Substances (EINECS), 497 chemicals were identified that fit the selection criteria for the established QSARs. Based on these results, an advisory tool has been developed that directs users to the appropriate QSAR model to apply for various types of organisms within specified log Kow ranges. Using this tool, it is possible to obtain a good indication of the toxicity of a large set of EINECS chemicals and newly developed substituted mononitrobenzenes to five different organisms without the need for additional experimental testing
Modelling maximum adsorption capacities of soot and soot-like materials for PAHs and PCBs
Noort, P.C.M. van; Jonker, M.T.O. ; Koelmans, A.A. - \ 2004
Environmental Science and Technology 38 (2004)12. - ISSN 0013-936X - p. 3305 - 3309.
aromatische koolwaterstoffen - polycyclische koolwaterstoffen - adsorptie - sorbaten - hydrofobiciteit - organische verbindingen - monitoring - waterkwaliteit - waterbodems - aromatic hydrocarbons - polycyclic hydrocarbons - adsorption - sorbates - hydrophobicity - organic compounds - water quality - water bottoms - polycyclic aromatic-hydrocarbons - hydrophobic organic-chemicals - partition-coefficients - aqueous solubilities - black carbon - sorption - water - sediment - extraction - biphenyls
Recent studies have shown that not partitioning but adsorption is the main mechanism for sorption of hydrophobic organic compounds to soot and soot-like materials. For compounds that adsorb by van der Waals forces only, variation in soot-water distribution coefficients will result from differences in these forces for adsorption, as well as the maximum number of accessible sites. This maximum number of accessible sites may a priori be expected to vary due to differences in both sorbent characteristics and sorbate dimensions. In this modeling study, variation in maximum adsorption capacities is explained from sorbent and sorbate properties. Maximum adsorption capacities were calculated using (a) literature values for soot-water distribution coefficients for polycyclic aromatic hydrocarbons and polycholorobiphenyls on 10 different soot and soot-like materials and (b) Langmuir affinities for adsorption at a carbonaceous surface estimated using a recently reported method
Recent studies have shown that not partitioning but adsorption is the main mechanism for sorption of hydrophobic organic compounds to soot and soot-like materials. For compounds that adsorb by van der Waals forces only, variation in soot-water distribution coefficients will result from differences in these forces for adsorption, as well as the maximum number of accessible sites. This maximum number of accessible sites may a priori be expected to vary due to differences in both sorbent characteristics and sorbate dimensions. In this modeling study, variation in maximum adsorption capacities is explained from sorbent and sorbate properties. Maximum adsorption capacities were calculated using (a) literature values for soot-water distribution coefficients for polycyclic aromatic hydrocarbons and polychlorobiphenyls on 10 different soot and soot-like materials and (b) Langmuir affinities for adsorption at a carbonaceous surface estimated using a recently reported method. The variation in maximum adsorption capacities could be explained by the variation in sorbent specific surface area, sorbent organic carbon content, and the sorbent-sorbate contact area. Furthermore, increasing sorbate thickness was related to a decrease in maximum adsorption capacities, which points to adsorption in micropores. Maximum adsorption capacities decreased by 1-2 orders of magnitude as the contact area increased by 50%. This points to adsorption sites being hardly larger than sorbates.
Baseline toxicity of a chlorobenzene mixture and total body residues measured and estimated with solid-phase microextraction
Leslie, H.A. ; Hermens, J.L. ; Kraak, M.H.S. - \ 2004
Environmental Toxicology and Chemistry 23 (2004)8. - ISSN 0730-7268 - p. 2017 - 2021.
hydrophobic organic-chemicals - lumbriculus-variegatus - pore-water - partition-coefficients - aquatic toxicity - fathead minnow - sediment - bioconcentration - pollutants - burdens
Body residues of compounds with a narcotic mode of action that exceed critical levels result in baseline toxicity in organisms. Previous studies have shown that internal concentrations in organisms also can be estimated by way of passive sampling. In this experiment, solid-phase microextraction (SPME) fibers were used as a too] to estimate the body residues, which were then compared to measured levels. Past application of SPME fibers in the assessment of toxicity risk of samples has focused on separate exposure of fibers and organisms, often necessitated by the amount of agitation needed in order to achieve steady state in the fibers within a convenient time period. Uptake kinetic studies have shown that in SPME fibers with thin coatings, equilibrium concentrations can be reached without agitation within the time frame of a toxicity test. In contrast to toxicity experiments to date, the SPME fibers in the current study were exposed concomitantly to the test water with the organisms, ensuring an exposure under the exact same conditions. Fibers and two aquatic invertebrate species were exposed to a mixture of four chlorobenzenes with a narcotic mode of action. The total body residue of these compounds in the organisms was determined, as was the acute toxicity resulting from the accumulation. The total body residues of both species were correlated to the total concentrations in SPME fibers. It was concluded that toxicity could be predicted based on total body residue (TBR) estimates from fiber concentrations.