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Recently, a new procedure was developed to estimate total body residues (TBRs) in biota after exposure to complex mixtures of organic chemicals in water. The procedure is based on a simulation of bioconcentration using a hydrophobic phase and on the measurement of total molar concentrations on this hydrophobic phase via vapor pressure osmometry and gas chromatography-mass spectrometry. In this paper, the results of the application of this procedure to effluents and surface water are presented. Estimated TBRs (TBRests) give informationon the potential total bioaccumulation of complex mixtures. Moreover, using these estimated total body burdens, baseline toxicity effectscan be predicted, including the contributions of chemicals with specific modes of action to the overall baseline toxicity. The advantage of the parameter TBRest is that it determines total molar concentrations of organic chemicals, including those chemicals that are usually not measured because they cannot be identified or because their concentrations are below the detection limits of individual compounds. [ABSTRACT FROM AUTHOR]

A highly sensitive and quantitative group parameter to determine total molar concentrations of organic micropollutants that can bioaccumulate in the lipid phase of aquatic organisms from effluents, surface water, and drinking water has been developed. C18 empore disk was used as a surrogate lipid phase. The partition process between water and C18 empore disk was employed to simulate the bioaccumulation process. After partition extraction of the water sample, the empore disk was extracted with cyclohexane, and total molar concentrations were determined in these extracts using vapor pressure osmometry (VPO) and gas chromatography/mass spectrometry (GC/MS), respectively. Total molar concentrations bioaccumulated in aquatic biota were estimated from the cyclohexane concentrations. Good accuracy for the total molar determination was obtained using VPO, due to the practically constant molar response factors (43.1 +/- 1.7 V/M) for a wide compound range and to excellent additivity of individual compound responses. Satisfying reproducibility (0-8.3%) of VPO was obtained for sample extracts. The detection limit of VPO in cyclohexane extracts corresponded to 0.60 mM in the lipid phase of aquatic biota. A minimal separation GC/MS system was developed, which enabled highly sensitive and sufficiently accurate total molar determinations. The reproducibility of the GC/MS determination for samples ranged from 0.7 to 22%. The detection limit of GC/MS in cyclohexane extracts corresponded to 0.044 mM in the lipid phase. The determined total molar concentrations in the lipid phase of aquatic biota were in the range of 0.139-168 mM for effluents, 0.26-1.34 mM for surface water systems, and < 0.044 mM for drinking water.