Revised Guidance Document 150 on Standardised Test Guidelines for Evaluating Chemicals for Endocrine Disruption
This guidance document was originally published in 2012 and updated in 2018 to reflect new and updated OECD test guidelines, as well as reflect on scientific advances in the use of test methods and assessment of the endocrine activity of chemicals. The document is intended to provide guidance for evaluating chemical using standardised test guidelines. Specific objectives include providing a description of the OECD conceptual framework for evaluating chemicals for endocrine disruption, background on the standardised test methods used, and guidance for interpreting the outcome of individual tests. The general approach taken by the document is primarily to provide guidance on how test results might be interpreted based on the outcome of standardised assays. Key questions addressed in the document concern likely mechanisms of endocrine action and any resulting apical effects that can be attributed to such action. The document is not proscriptive but provides suggestions for possible next steps in testing (if any) which might be appropriate for a regulatory authority to take, given the various data scenarios. The guidance document is focused primarily on endocrine modalities included in the conceptual framework; estrogen, androgen, and thyroid mediated endocrine disruption and chemicals that interfer with steroidogenesis.
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Prenatal Developmental Toxicity Study (OECD TG 414)
TG 414 is an OECD validated developmental toxicity test designed to provide general information concerning the effects of prenatal exposure on the pregnant test animal and on the developing organism. The test substance is normally administered to pregnant animals at least from implantation to one day prior to the day of scheduled kill, which should be as close as possible to the normal day of delivery. This Test Guideline is intended for use with rodent (rat preferably) and non-rodent (rabbit preferably). Each test and control group should contain a sufficient number of females to result in approximately 20 female animals with implantation sites at necropsy. Three concentrations, at least, should be used. The test substance or vehicle is usually administered orally by intubation. A limit test may be performed if no effects would be expected at a dose of 1000 mg/kg bw/d. The results of this study include measurements (weighing) and clinical daily observations, each day preferably at the same time. Shortly before caesarean section, the females are killed (one day prior to the expected day of delivery), the uterine contents are examined, and the foetuses are evaluated for soft tissue and skeletal changes. A number of endocrine-related measurements in the dams and in the fetuses have been added in 2018. In any study which demonstrates an absence of toxic effects, further investigation to establish absorption and bioavailability of the test substance should be considered.
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