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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Two-Generation Reproduction Toxicity Study (OECD TG 416)
TG 416 is an OECD validated two-generation reproduction test designed to provide general information concerning the effects of a test substance on the integrity and performance of the male and female reproductive systems, and on the growth and development of the offspring. The test substance is administered daily in graduated doses to several groups of males and females. Males and females of the Parent generation (5-9 weeks old) should be dosed during growth, during their mating, during the resulting pregnancies, and through the weaning of their first generation offspring. The administration of the substance is continued to first generation offspring during their growth into adulthood, mating and production of a second generation (until the weaning). The rat is the preferred species for testing. Each test and control group should contain a sufficient number of animals to yield preferably not less than 20 pregnant females at or near parturition. At least three dose levels and a concurrent control shall be used. It is recommended that the test substance be administered orally (by diet, drinking water or gavage). 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, sperm parameters, oestrus cycle parameters and offspring parameters), clinical daily observations, as well as gross necropsy and histopathology. The findings of this two-generation reproduction toxicity study should be evaluated in terms of the observed effects including necropsy and microscopic findings. A properly conducted reproductive toxicity test should provide a satisfactory estimation of a no-effect level and an understanding of adverse effects on reproduction, parturition, lactation, postnatal development including growth and sexual development.
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