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Revised Guidance Document 150 on Standardised Test Guidelines for Evaluating Chemicals for Endocrine Disruption

image of 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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Reproduction/Developmental Toxicity Screening Test (OECD TG 421) and Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test (OECD TG 422)

TG421/422 are OECD validated methods for evaluting effects of a test chemical on male and female reproductive performance. The TG is designed to be used with the rat and has been updated with endocrine disruptor endpoints, in particular measure of anogenital distance and male nipple retention in pups and thyroid examination. Males are dosed for a minimum of four weeks and females should be dosed throughout the study (~ 63 d). At least three test groups and a control group should be used, and each group should be started with >10 animals of each sex. Dose levels may be based on information from acute toxicity tests or on results from repeated dose studies. The test substance is administered orally and daily. The results of this study include clinical observations, body weight and food/water consumption, oestrous cycle monitoring, offspring parameters observation/measurement, thyroid hormone measurement, as well as gross necropsy and histopathology. The findings of this toxicity study should be evaluated in terms of the observed effects, necropsy and microscopic findings. Because of the short period of treatment of the male, the histopathology of the testis and epididymus should be considered along with the fertility data, when assessing male reproductive effects.

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