User Guide to Thresholds and Classification - Environmental ...

176User Guide for Thresholds and Classifications12. Eye Corrosion and Irritation – Subclass 6.4 (8.3)12.1. General considerations12.1.1. Eye corrosion or irritation overviewSee section 9.6 in chapter 9 for definitions of the key terms used in this chapter.Before there is any in vivo testing for eye corrosion or eye irritation, all existing information on a substanceshould be reviewed. Preliminary decisions can often be made from existing data as to whether a substancecauses corrosive (that is, irreversible) damage to the eyes. If, based on this information, a substance can beclassified, no testing is required. A highly recommended way of evaluating information on existingsubstances or of approaching new uninvestigated substances is to use a tiered testing strategy for eyecorrosion and eye irritation.Several factors should be considered in determining the eye corrosive or irritation potential of a substancebefore testing is undertaken. Accumulated human and animal experience should be analysed first, as it givesinformation directly relevant to effects on the eye. In some cases, enough information may be available fromstructurally related compounds to classify the substance. Likewise, pH extremes (≤ 2 and ≥ 11.5), mayproduce eye corrosion, especially when associated with significant buffering capacity. Such substances areexpected to produce significant effects on the eyes. Possible skin corrosion must be evaluated before eyecorrosion or irritation is considered in order to avoid testing for local effects on eyes with skin corrosivesubstances. In vitro alternatives that have been validated and accepted may be used to make classificationdecisions.Although information might be gained from the evaluation of single parameters within a tier (for example,caustic alkalis with extreme pH should be considered as local corrosives), there is merit in considering thetotality of existing information and making an overall weight-of-evidence determination. This is especially truewhen there is information available on only some parameters. Generally, primary emphasis should be placedon expert judgement, considering human experience with the substance, followed by the outcome of skinirritation testing and well-validated alternative methods. Animal testing with corrosive substances should beavoided whenever possible.A tiered approach to the evaluation of initial information should be considered where applicable (Table 12.1),recognising that all elements may not be relevant in certain cases. The tiered testing approach providesgood guidance on how to organise existing information on a test material and to make a weight-of-evidencedecision about hazard assessment and hazard classification – ideally, without conducting new animal tests.Table 12.1: Testing and evaluation strategy for eye corrosivity and eye irritationStep Parameter Findings Conclusions1aData relating to historical humanor animal experienceEye corrosiveCategory 8.3AEye irritantCategory 6.4AJanuary 2012 EPA0109