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Sodium hypochlorite classification reviewed
The previous legislation (EU Directive 67/548/EEC) listed a specific concentration limit of 25% active chlorine, above which solutions of sodium hypochlorite were classified as "Dangerous for the Environment" and labelled N; R50, whereas solutions or mixtures containing < 25% active chlorine were not. When the new EU Regulation on Classification, Labelling and Packaging of Substances and Mixtures (EC 1272/2008) (CLP) came into force in January 2009, it introduced a change in the way that solutions of sodium hypochlorite had to be classified and labelled as "Dangerous to the Environment". The specific concentration limit has been deleted in the new regulation and replaced by a general provision, the "M-factor". The "M-factor" is a number allocated to individual highly toxic substances that is derived from the data on their acute toxicity to aquatic species. The new data is considered to be more reliable than previous data from invertebrate toxicity studies. This new result, combined with other available reliable data, shows that invertebrates and fish are equally sensitive to the toxic effects of sodium hypochlorite and allows one to conclude, based on the weight of evidence, that the acute toxicity of sodium hypochlorite to freshwater species lies in the range: 10 < L(E)C50 ≤ 100 μg/L. This means that an "M-factor" of 10 should be assigned to sodium hypochlorite which, in turn, means that if classification is based on the calculation method, solutions of ≥ 2.5% active chlorine will need to be classified as "Dangerous to the Environment (N; R50). Solutions containing < 2.5% active chlorine do not need to be classified in this way. An "M-factor" of 10 must also be applied when classifying mixtures/preparations containing hypochlorite according to the calculation method. Other results based on the testing of specific formulations may give rise to a different, specific concentration for the classification of these formulations.
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