Reaction mass of disodium metasilicate and sodium hydroxide

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Effect on fertility: via oral route

Endpoint conclusion:

no study available

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

For sodium silicate:

In a 4-generation study with rats, the total number of offspring born at 79 mg/kg bw/d was reduced to 67% of offspring weaned to 46% of the control, respectively (Smith et al., 1973). The NOAEL for parental animals was determined to be > 159 mg/kg bw/day. For the F1 generation no NOAEL was identified. Severe limitations of the study and inter-current deaths, including controls make it however difficult to draw any firm conclusion from this study.

In addition, in oral repeated dose toxicity studies with rats and dogs, the macroscopic and microscopic examination of reproductive organs did not reveal any treatment-related effects (Newberne and Wilson, 1970). The NOAEL for rats and dogs was > 2400 mg/kg bw/day.

Kamboj and Kar (1964) did not find testicular effects of sodium silicate injected either subcutaneously or intratesticularly in male rats. The NOAEL was determined to be > 8 mg/kg bw.

Effects on developmental toxicity

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Additional information

This substance is a multi-constituent substance consisting of sodium hydroxide (215-185-5, 1310-73-2) and disodium metasilicate (229-912-9, 6834-92-0). It is the by-product of a reaction between Zircon (EC no 239-019-6) and sodium hydroxide; after hydrolysis, this substance is the water-soluble fraction. The OECD SIDS Initial Assessment Report for SIAM 18 Paris, France 20-23 April, 2004 reported that a mixture of silicic acid, sodium salt (215-687-4) and sodium polyphosphate (OECD Guideline 475 (Mammalian Bone Marrow Chromosome Aberration Test) did not demonstrate genetic toxicity (No significant increase of chromosomal aberrations compared to negative control even at dosage levels exceeding the M.T.D. of 940 mg/kg bw.). Sodium hydroxide does not have the potential to be a genetic toxin based on the presence of only a sodium anion. The REACH text states:

8.4.2. The study does not usually need to be conducted — if adequate data from an in vivo cytogenicity test are available, or

►M3 — the substance is known to be carcinogenic category 1A or 1B or germ cell mutagenic category 1A, 1B or 2.◄

8.4.3. The study does not usually need to be conducted if adequate data from a reliable in vivo mammalian gene mutation test are available.

8.4. Appropriate in vivo mutagenicity studies shall be considered in case of a positive result in any of the genotoxicity studies in Annex VII or VIII.

Sodium Hydroxide: Source - the sodium hydroxide summary risk assessment report JRC EC 2008

No valid studies were identified regarding effects on fertility or developmental toxicity in animals after oral, dermal or inhalation exposure to NaOH. NaOH is not expected to be systemically available in the body under normal handling and use conditions and for this reason it can be stated that the substance will not reach the foetus nor reach male and female reproductive organs. Therefore, a specific study to determine the reproduction toxicity is not necessary.

Based on these data sets, no further testing is required for the reaction mass of disodium metasilicate and sodium hydroxide and no additional test is proposed.

The above should be considered as an expert statement to fulfil the REACH registration requirements under Annex VIII for endpoint 8.4.2, 8.4.3 and 8.4.4.