User Guide to Thresholds and Classification - Environmental ...

309User Guide for Thresholds and ClassificationsAppendix 19D: Globally Harmonized System of Classificationand Labelling – additional guidance on aquatic hazard datainterpretation19D.1 IntroductionThis appendix is largely the same as the Globally Harmonized System of Classification and Labelling ofChemicals (GHS) Annex 9 guidance on aquatic hazard classification (United Nations, 2007). Changes havebeen made where necessary to refer to the Hazardous Substances and New Organisms Act 1996 (HSNOAct) aquatic classification criteria as these sometimes differ from the GHS.19D.2 Aquatic toxicityIntroductionThe basis for the identification of hazard to the aquatic environment for a substance is the aquatic toxicity ofthat substance. Classification is predicated on having toxicity data for fish, crustacea, and algae/aquatic plantavailable. These taxa are generally accepted as representative of aquatic fauna and flora for hazardidentification. Data on these particular taxa are more likely to be found because of this general acceptanceby regulatory authorities and the chemical industry. Other information on the degradation andbioaccumulation behaviour is used to better delineate the aquatic hazard. This section describes theappropriate tests for ecotoxicity, provides some basic concepts in evaluating the data and usingcombinations of testing results for classification, summarises approaches for dealing with difficultsubstances, and includes a brief discussion on interpretation of data quality.Description of testsFor classifying substances in the harmonised system, freshwater and marine species toxicity data can beconsidered as equivalent data. It should be noted that some types of substances, for example, ionisableorganic chemicals or organometallic substances may express different toxicities in freshwater and marineenvironments. Since the purpose of classification is to characterise hazard in the aquatic environment, theresult showing the highest toxicity should be chosen.The GHS criteria for determining health and environmental hazards should be test method neutral, allowingdifferent approaches as long as they are scientifically sound and validated according to internationalprocedures and criteria already referred to in existing systems for the endpoints of concern and producemutually acceptable data. According to the GHS system:Acute toxicity would normally be determined using a fish 96-hour LC50 (OECD Test Guideline 203 orequivalent), a crustacea species 48-hour EC50 (OECD Test Guideline 202 or equivalent) and/or analgal species 72- or 96-hour EC50 (OECD Test Guideline 201 or equivalent). These species areconsidered as surrogate for all aquatic organisms and data on other species such as the duckweedLemna may also be considered if the test methodology is suitable.January 2012 EPA0109