User Guide to Thresholds and Classification - Environmental ...

114User Guide for Thresholds and Classifications9. Introduction to Toxicity – Class 69.1. IntroductionThe eight subclasses under the toxicity property in the Hazardous Substances and New Organisms Act 1996(HSNO Act) are:subclass 6.1 – substances that are acutely toxic (see Chapter 10 below)subclass 6.3 – substances that are skin irritants (see Chapter 11 below)subclass 6.4 – substances that are eye irritants (see Chapter 12 below)subclass 6.5 – substances that are sensitisers (see Chapter 13 below)subclass 6.6 – substances that are mutagenic (see Chapter 14 below)subclass 6.7 – substances that are carcinogenic (see Chapter 15 below)subclass 6.8 – substances that are reproductive or developmental toxicants (see Chapter 16 below)and subclass 6.9 – substances that are specific target organ toxicants (see Chapter 17 belowNote that class 6.2 (infectious substances) is not included in the above list as those substances are notcaptured under the HSNO Act.Two subclasses (relevant to toxicity) are also defined under the corrosive property in the HSNO Act. Theyare:subclass 8.2 – substances that are corrosive to skin (see Chapter 11 below);and subclass 8.3 – substances that are corrosive to eyes (see Chapter 12 below).9.2. Classification of substancesIn each of the following sections, guidance is provided on how to classify a substance for each of the 10subclasses. Each section outlines the key considerations required to assign a classification to a substanceand acceptable test methods for deriving data for classification purposes. Additional guidance is providedwhere there may be difficulties in interpretation of the regulations or more complex types of data.9.3. Classification of mixtures: generic guidanceOnce a substance triggers a threshold, it is then classified. While this is relatively straightforward for singlesubstances, substances as mixtures are more complex.The general process for classification of toxicity hazards is as follows.When toxicity test data are available for the complete substance (or mixture) then classification is basedon the test results.When test data are not available for the mixture itself, then bridging principles should be considered tosee whether they permit classification of the mixture.January 2012 EPA0109