Registration Dossier
Registration Dossier
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EC number: 231-132-9 | CAS number: 7440-23-5
Endpoint summary
Administrative data
Description of key information
Additional information
Sodium, in contact with water is quasi-instantaneously decomposed (weight of evidence). According to annex XI.2 and OECD guidance document on aquatic toxicity testing of difficult substances and mixtures (OECD 2000*), if the substance is likely to be unstable, a decision to test the parent substance and/or its degradation products, if identified, should be based on a consideration of its half-life under test and real-world conditions. The following decision criteria are suggested in the OECD guidance (OECD, 2000*) document only as a guide for static and semi-static tests with medium renewal times of 24 hours:
- Half-life > 3 days: test parent substance;
- Half-life < 3 days and >1 hour: consider on a case-by-case basis, and include possible testing of degradation products;
- Half life < 1 hour: test degradation products.
Testing of both parent compound and/or degradation products will depend on the physico-chemical properties of the substance, the objectives and regulatory requirements.
In the present case, sodium is considered as a flammable substance on contact with water, which is quasi-instantaneously decomposed (weight of evidence):
Na + H20 -> NaOH + ½ H2
Considering the high reactivity with water of the parent substance (half life of Na < 1 hour), the sodium can be considered as a hydrolytically unstable substance justifying a non-testing decision for the evaluation of its toxicity to aquatic organisms.
Hence, the toxicity of the substance needs to be estimated by taking into account the indirect toxicity of its degradation products, which is beyond the scope of this report.
The environmental risk assessment is to be performed using the toxicity data of sodium degradation product (NaOH) which is considered in its relative registration dossier. Considering the nature of the degradation product, sufficient data related to ecotoxicological is generated for this substance (European RAR available). The results of the chemical safety assessment clearly indicates that there is no need to investigate further the effects of the substance and/or the relevant degradation products.
* OECD, 2000. Guidance document on aquatic toxicity testing of difficult substances and mixtures. OECD Series on testing and assessment. Number 23, OECD.
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