Registration Dossier
Registration Dossier
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EC number: 200-891-8 | CAS number: 75-68-3
Endpoint summary
Administrative data
Description of key information
The acute inhalation toxicity of 1-chloro-1,1-difluoroethane is low. The recalulated 4h LC50 in rats is established to be >1877331 mg/m3.
Key value for chemical safety assessment
Additional information
In accordance with section 2 of REACH Annex XI, an acute oral and dermal toxicity study does not need to be conducted as the substance is a gas.
Three acute inhalation toxicity studies are available. The acute inhalation toxicity of the substance is low. The rat study conducted by Litton Bionetics Inc. is considered the key study as it is the most recent and a well-documented near-guideline study. In this study, a LC50 of >1640000 mg/m3 (2/10 animals died at this concentration) was established (exposure duration: 6 hours). The target organs are the lungs, with red mottling observed at gross necropsy, and the central nervous system, with anesthesia-like symptoms which were rapidly reversible after the end of exposure.
As the classification and labelling according to EU Directive 67/548/EEC should be based on 4 hours exposure, a time extrapolation is required in this case. According to Chapter R.8 of REACH Technical Guidance Document, if time extrapolation is considered valid, then the most appropriate approach is to make use of the modified Haber’s law (Cnx t = k, where ‘C’ is the concentration, ‘n’ is a regression coefficient, ‘t’ is the exposure time and ‘k’ is a constant) according to which the relationship between exposure concentration and exposure duration for a specific effect is exponential. A default value of n=3 is suggested for extrapolating from longer to shorter exposure durations. Therefore the recalculated LC50 for 4 hours exposure to 1-chloro-1,1,-difluoroethane in rats is established to be >1877331 mg/m3.
Justification for classification or non-classification
Based on the 4 hours LC50 of >1877331 mg/m3 in rats and the absence of other major significant effects, 1 -chloro-1,1 -difluoroethane does not need to be classified for acute toxicity according to EU Directive 67/548/EEC and EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.
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