Registration Dossier
Registration Dossier
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EC number: 200-839-4 | CAS number: 75-10-5
Endpoint summary
Administrative data
Description of key information
Aquatic toxicity testing with gases often lead to invalid results because of the technical difficulties associated with the physical state of the substances.
Given the physical nature of difluoromethane and due to the difficulty to test it meaningfully, no experimental aquatic results are available. Instead, QSAR methods were used to estimate the toxicity of the substance to aquatic organisms. The effect concentrations of difluoromethane were estimated using the method described in the EU Technical Guidance Document (2003) and/or the US EPA program ECOSAR (v1.00, 2009). The measured log Kow value of 0.21 was used for the predictions using both QSARs.
Predicted values:
Fish: 96h-LC50 = 1507.037 mg/L
Daphnids: 48h-LC50 = 652.238 mg/L
Green Algae: 96h-EC50 = 142.302 mg/L
All acute toxicity calculations are reliable, validated and fall within the applicability domain of the QSARs. The environmental relevance of these estimations are reinforced with the experimental values obtained for some other members of the category that are presented as supporting studies.
A category approach was used to to support QSAR estimations and reinforce the evidence of low toxicity to aquatic organisms. Commercially available HFCs and HCFCs share common physicochemical and environmental fate. Although it is not possible to identify clear structure-related trends along the series, the common features present in the ecotoxicological profiles of these substances demonstrate that category approach is justified for these two groups of substances. The justification of the category approach is attached to each study record.
Lastly, the exposure of aquatic compartments should be very low based on the volatility of the test substance. In other words, a significant part of the test substance will quickly partition into the atmospheric compartment. In assessment based on QSAR estimations and a category approach, the most conservative values are used to fill the missing endpoints.
Additional information
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