Registration Dossier
Registration Dossier
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EC number: 231-569-5 | CAS number: 7637-07-2
Endpoint summary
Administrative data
Description of key information
Additional information
When release in the atmosphere boron trifluoride (BF3) molecules in contact with atmospheric humidity form a complex: dihydrated boron trifluoride (BF3, 2H2O). On the opposite if BF3 is directly brought into contact with water, it reacts violently. That is the reason why all the assessment of environmental fate and pathways is based on the properties of the more stable dihydrate form of boron trifluoride and those of its breakdown products in water: boric acid and fluoboric acid. The latter hydrolyzes further to yield ultimately hydrofluoric acid/fluoride ions.
Measurement of fluoride ion production over a range of pH values (1.2 to 9), using both ion chromatography and an ion-selective electrode, indicated a hydrolytic half-life time of less than 30 minutes for boron trifluoride. Subsequent analysis of boric acid by titration confirmed the rapidity of the reaction.
Fluoroboric acid was determined to be hydrolytically unstable under similar conditions, reacting to form the ultimate degradation product boric acid and, predominantly, intermediate fluoroborate species. These latter components were not positively identified but, chromatographing as a very broad peak between the tetrafluoroborate and boric acid peaks, and increasing in concentration over the duration of the test, it was considered likely that these were the partially hydrolysed fluoroborate species.
The EU Risk assessment report on Hydrofluoric acid indicates for fluoride ions, which are one of the hydrolysis products, a PNEC of 0.9 mg/L (or 3.3 mg/L derived with SSD). A PNEC of 0.56 mg/L (or 1.9 mg/L derived with SSD) was estimated for boric acid. Therefore, we can assume that the toxicity of BF3 is dominated by the toxicity of H3BO3.
In order to support the aforementioned strategy for the ecotoxicological hazard assessemnt, publications describing the aquatic toxicity of tetrafluoroborate were also quoted. This publications are recorded as supportive data.
As a consequence, we use all the public data relative to boric acid and fully described in the the EU Risk assessment to evaluate BF3. That is the reason why the aquatic hazard assessment is based on the data obtained for boric acid.
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