User Guide to Thresholds and Classification - Environmental ...

207User Guide for Thresholds and Classifications14. Mutagenicity – Subclass 6.614.1. General considerations14.1.1. Mutagenicity overviewSee section 9.6 in chapter 9 above for definitions of the key terms used in this chapter.This hazard class is primarily concerned with chemicals that may cause mutagenic effects in the germ cellsof humans that can be transmitted to the progeny. However, mutagenicity/genotoxicity tests in vitro and inmammalian somatic cells in vivo are also considered in classifying substances and mixtures within thishazard class.A mutagenic effect means a permanent change in the amount or structure of the genetic material in a cell,being a permanent change that is:manifested at the phenotypic level; oran underlying DNA modification (including specific base pair changes and chromosomal translocations).The terms ‗mutagenic‘ and ‗mutagen‘ are used for agents giving rise to an increased occurrence of mutationsin populations of cells and/or organisms.A genotoxic effect means alterations to the structure, information content, or segregation of DNA, including:DNA damage caused by interference with its normal replication processes; andtemporary non-physiological alterations to its replication.The terms ‗genotoxic‘ and ‗genotoxicity‘ refer to those agents or processes that cause a genotoxic effect.14.1.2. Weight of evidenceThe best quality data should be used as the fundamental basis for classification. Preferably, classificationshould be based on primary data sources. It is essential that test conditions be clearly and completelyarticulated.Data from internationally harmonized test methods are preferred for classification under this subclass. Datashould preferably be derived using Organisation for Economic Co-operation and Development (OECD) TestGuidelines or equivalent according to the principles of Good Laboratory Practice. When such data are notavailable, classification should be based on the best available data using a weight-of-evidence approach.See section 1.3 in chapter 1 above for information about assessing data quality.See Appendix 14A below for a detailed list of acceptable test methods for mutagenicity14.2. Mutagenicity hazard and classification criteria14.2.1. Mutagenicity threshold criteriaSchedule 4 to the Hazardous Substances (Minimum Degrees of Hazard) Regulations 2001 states:January 2012 EPA0109