试验321：Hyalella Azteca生物浓缩试验（HYBIT）

OECD/OCDEYou are free to use this material subject to the terms and conditions available athttp://www.oecd.org/termsandconditions/1OECD GUIDELINE FORTHETESTING OF CHEMICALSHyalella azteca Bioconcentration Test (HYBIT)1. TheHyalella aztecaBioconcentration Test (HYBIT) provides a non-vertebrate test for bioconcentration2. HYBIT has been developed in such a way that it is as close as possible to the concept described in the3. Inaddition to the established flow-through regime commonly applied in bioconcentration studies, semi-static regimes are permissible as options in studies carried out according to this Guideline. Both regimeshave been validated as part of an international ring trial (2).4. The aqueous exposure test is most applicable to organic chemicals with logKOWvalues between 1.5 and6.0, but may still be used with highly hydrophobic chemicals (having logKOW>6.0), if a stable and fullydissolved concentration of the test chemical in water can be demonstrated (3,4). The log Kowis based on the steady-state thermodynamics of solutes, and so the log Kowcharacterise bioaccumulation of chemicals, such as PFAS and other chemicalswith surfactant properties,values may be difficult or even impossible to determine because other processes arerate-limiting instead of thermodynamic partitioning.5. The bioconcentration test is generally based on measuring the bioaccumulation of parent test chemical.Radiolabelled test chemicals can enable a sensitive analysis of water and tissue samples. Separationprocedures e.g. TLC or HPLC should be employed prior to radio-detection to enable quantitative analysisof the parent testchemical and transformation products. Peaks associated with the parent test chemical andtransformation products should be verified using non-labelled certified reference standards. In addition,the bound residue (non-extractable fraction) of radiolabelled test chemical in the tissue homogenate shouldbe quantified when a radiolabelled test chemical is used. When separation techniques are applied, a BCFdetermination for the parent test chemical should be based upon the concentration of the parent testchemical inH. aztecaand not upon total radioactive residues. If total radioactive residues (TRR) aredetermined (e.g. by combustion or tissue solubilisation), the radioactivity and therefore the BCF is basedon the total radioactivity associated with parenttest chemical, retained metabolites and assimilated carbon.BCF values based on TRR may be overly conservative and not directly comparable to a BCF derived wherean extraction method has been employed followed by specific chemical analysis of the parent test chemical6. The decision on whether to conduct a flow-through or semi-static exposure experiment should be basedon the feasibility to maintain stable exposure concentrations in the water phase during the uptake phasethat are within ±20% of themean of the measured values [cf. paragraph 17(c)]. Important factors that may ©OECD, (2024)INTRODUCTIONin aquatic environments.OECD TG 305 part I (1).measurementtest may not be suitable tofor which log Kowonly. OECD/OCDE2influence application choice are,e.g.the test chemical’s potential for adsorption to test vessels andapparatus, its stability in aqueous solution, etc. Information on such practical aspects may be availablefrom other aquatic toxicity tests. If no information is available, a pre-test may be conducted to confirm thesuitability of the selected exposure regime (5).7. It should be verified that the aqueous exposure concentration to be applied is within the aqueoussolubility range of the test chemical in the test media [cf.paragraph 17(d); paragraph 14(b)]. Differentmethods for maintaining stable concentrations of the dissolved test chemical can be used, such as the useof stock solutions or passive dosing systems (e.g.column elution method) (6). It should be demonstratedby regular measurements that stable concentrations can be maintained.8. The test consists of two phases: the exposure (uptake) and post-exposure (depuration) phases. Duringthe uptake phase, a group ofH. azteca(ca. 1200-1500 male amphipods) is exposed to the test chemical atone or more chosen concentrations, depending on the properties of the test chemical (cf.paragraphs 14 and38). They are then transferred to a medium free of the test chemical forthe depuration phase. Theconcentration of the test chemical in the analysedH. aztecais followed through both phases of the test.Parameters which characterise the bioaccumulation potential include the uptake rate constant (k1),the steady-state bioconcentration factor(BCFSS). In addition to the exposed group, a procedural water control should beincluded which is held under identical conditions (including sampling), to relate possible adverse effectsobserved in the bioconcentration test to a matching control group. If the use of solvent is required (cf.paragraph 23), one control containing the solvent, instead of the procedural water control, should be runin