Registration Dossier
Registration Dossier
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EC number: 442-070-9 | CAS number: 329039-38-5
PBT assessment
Administrative data
PBT assessment: overall result
- PBT status:
- the substance is not PBT / vPvB
- Justification:
The screening criteria given in the ‘Guidance on information requirements and chemical safety assessment, chapter R.11: PBT Assessment’ (ECHA, 2008) are used as surrogate information to decide whether methyldiacetoxyisopropoxysilane (CAS No. 329039-38-5) may potentially fulfil the PBT or vPvB criteria.
Persistence assessment
Data for the definitive conclusion on the potential persistence (P) status of methyldiacetoxyisopropoxysilane (CAS No. 329039-38-5) according to Regulation (EC) No. 1907/2006, Annex XIII are not available. Thus, the screening criteria given in the “Guidance on information requirements and chemical safety assessment, chapter R.11: PBT assessment” (ECHA, 2008) are used as surrogate information to decide whether the substance may be considered persistent (P). Methyldiacetoxyisopropoxysilane (CAS No. 329039-38-5) hydrolyses rapidly in water at pH 4, 7 and 9 (DT50 < 4 h, Reimer (2002) and Sargent (2001)). The main transformation products (based on its chemical structure) are expected to be acetic acid (CAS No. 64-19-7), isopropanol (67-63-0) and methylsilanetriol (CAS No. 2445-53-6). A biodegradation screening test performed with the parent compound, methyldiacetoxyisopropoxysilane (CAS No. 329039-38-5) is available (Eickhoff, 2002), according to OECD Guideline 301F. The results of this test show 59% biodegradation after 28 days. Due to its potential for hydrolysis, this result rather stands for the biodegradation of the hydrolysis products than that of the parent compound. Since acetic acid and isopropanol are known to be readily biodegradable (HSDB, (2011),OECD SIDS (1997)), methylsilanetriol is expected to be the metabolite showing low to moderate biodegradation potential.
Based on the above information, methyldiacetoxyisopropoxysilane does not meet the criteria for persistence (P or vP). The methylsilanetriol (hydrolysis product) may be persistent.
Bioaccumulation assessment
According to the criteria set in Regulation (EC) No. 1907/2006, Annex XIII, a substance fulfils the bioaccumulation criterion (B) when the bioconcentration factor (BCF, based on measured data) is > 2000 L/kg. As no experimental data evaluating bioaccumulation in biota are available, surrogate information according to “Guidance on information requirements and chemical safety assessment, chapter R.11: PBT assessment” (ECHA, 2008) is used to evaluate the bioaccumulation potential of methyldiacetoxyisopropoxysilane. This substance hydrolyses rapidly in water (< 4 hours) and therefore its bioavailability to aquatic organisms is expected to be low.Furthermore, the estimated log Pow values (2.63) of methyldiacetoxyisopropoxysilane (CAS No. 329039-38-5) and its main hydrolysis products: isopropanol, 0.05 (OECD SIDS, 1997); acetic acid, -0.71 (HSDB, 2011) and methylsilanetriol, 0.78 (Reimer, 2002) indicate that low bioaccumulation potential can be expected for these substances.
Considering the available data, methyldiacetoxyisopropoxy silane (and hydrolysis products) do not meet the bioaccumulation criteria (B or vB).
Toxicity assessment
According to Regulation (EC) No. 1907/2006, Annex XIII, a substance fulfils the toxicity criterion (T) when the long-term NOEC values for aquatic organisms are lower than 0.01 mg/L or if the substance is classified as carcinogenic, mutagenic or toxic for reproduction or there is any evidence of chronic toxicity. Chronic data from studies conducted with methyldiacetoxyisopropoxysilane on aquatic organisms (freshwater/ marine) are not available. According to the screening criteria stated in the “Guidance on information requirements and chemical safety assessment, chapter R.11: PBT assessment” (ECHA, 2008), a substance can be considered to be T if the results from acute tests performed on fish, Daphnia or algae show EC/LC50s < 0.1 mg/L. The short-term aquatic toxicity tests conducted with methyldiacetoxyisopropoxysilane (CAS No. 329039-38-5) resulted in LC50 (96 h)= 1517 mg/L (fish, nominal), EC50 (48 h) > 1000 mg/L (Daphnia, nominal) and EC50 (72 h)= 931.3 mg/L (algae, nominal), well above the trigger value of 0.1 mg/L.
Furthermore, the substance is not classified as carcinogenic, mutagenic or toxic for reproduction nor is there any evidence of chronic toxicity according to Directive 67/548/EEC and Regulation (EC) No 1272/2008.
Considering the available data, methyldiacetoxyisopropoxysilane is not considered to be toxic regarding both ecotoxicological and toxicological endpoints and therefore the substance does not meet the toxicity criterion (T).
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