Registration Dossier
Registration Dossier
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EC number: 237-224-5 | CAS number: 13701-64-9
Endpoint summary
Administrative data
Description of key information
In the environment the transformation/hydrolysis of boron compounds is complex and is dependent on environmental factors; however, under typical environmental conditions it is expected that boric acid will be the most common and dominant species in the aquatic environment, soil and sediment and it is also not expected to degrade further due to the high energy required to break the B – O bond (523 kJ/mol). Therefore, a read-across approach is considered appropriate to use the source substance, boric acid, rather than the target compound (calcium metaborate).
Stability - hydrolysis:
A review of the structure of the test item has indicated that it consists of infinite (polymeric) chains of B2O42- units plus the Ca2+ counterions, and therefore, will be extremely insoluble in water. Therefore, it has been concluded that any test item that appears to have dissolved in aqueous solutions will actually exist in the solutions as the fully hydrolysed (i.e., polymeric B2O42- chains into borate) and fully dissociated species, i.e. as separate calcium cations and borate (boric acid) anions, depending on the pH of the aqueous solution. Based on the dissociation constant of boric acid, i.e. 9.14 it can be concluded that hydrolysis and therefore apparent solubility of the test item at pH 9 will be slow and minimised. Hydrolysis and apparent solubility at pH 7 will be fairly rapid. Hydrolysis and apparent solubility at pH 4 will be very rapid and maximised. Based on the extreme insolubility of the (parent) test item in water and the hydrolysis issues discussed above, it was concluded that hydrolysis testing of the (parent) test item was not feasible.
Biodegradation - biodegradation in water:
The ready biodegradability of the test item in water does not need to be conducted because the substance is inorganic.
Transport and distribution - adsorption / desorption:
Based on adsorption-desorption studies in soil, freshwater and marine sediments the adsorption of the source substance, boric acid, to soil and sediment is expected to be low.
Additional information
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