Registration Dossier
Registration Dossier
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EC number: 910-245-3 | CAS number: -
PBT assessment
Administrative data
PBT assessment: overall result
- PBT status:
- the substance is not PBT / vPvB
- Justification:
Sodium hydroxide and Soluble silicates are not PBT or vPvB candidate substances.
PBT/vPvB criteria and justification
A persistence assessment is not applicable, since the substance is inorganic.
Compounds of silicon and oxygen are ubiquitous in the environment; they are present in inorganic matter, like minerals and soils as well as in organic matter, like plants, animals and man. Silicon is an essential trace element participating in the normal metabolism of higher animals. It is required in bone, cartilage and connective tissue formation as well as participating in other important metabolic processes (HERA 2005).
Toxicokinetic data on vertebrates revealed a low potential for bioaccumulation. Ingested silicates are excreted via urine and to a lesser extent via the faeces. Markedly increased and rapid urinary excretion of silica was observed when soluble sodium silicates were administered to rats (Benke & Osborn 1979), dogs (King et al. 1933), cats (King & McGeorge 1938) and guinea pigs (Sauer et al. 1959). The urinary silicon excretion half-life after administration of sodium silicate to rats via stomach tube was 24 h (Benke & Osborn 1979).
Based on these considerations no bioaccumulation is to be expected.
The toxicity criterion is not fulfilled for ecotoxicity for soluble silicates with no ecologically relevant NOECs less than 0.01 mg/L (lowest NOEC: 35 mg/L, algae). The substance is not classified as carcinogenic, mutagenic or toxic for reproduction nor is there any evidence of chronic toxicity, as identified by the classifications: T, R48, or Xn, R48 according to Directive 67/548/EEC.
NaOH:
Persistence
NaOH will rapidly dissolve and dissociate in water. Therefore, NaOH does not fulfil the P criterion.
Bioaccumulation
Bioaccumulation is not relevant for NaOH, therefore, NaOH does not meet the B criterion of the PBT criteria.
Toxicity
The lowest LC50 for freshwater and marine organisms were found to be 40 and 33 mg/l, respectively. This is clearly above the cut-off value of 0.1 mg/l. Therefore, NaOH does not meet the T criterion in the PBT assessment.
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