Reaction mass of 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane and 4,4,14,14-tetraethoxy-3,15-dioxa-8,9,10-trithia-4,14-disilaheptadecane

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.7 mg/L

Assessment factor:

1 000

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

7 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.07 mg/L

Assessment factor:

10 000

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

10 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

91 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

9.1 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

29 mg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

PNEC oral

PNEC value:

6.7 mg/kg food

Assessment factor:

300

Additional information

The registered substance, reaction mass of 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane (S2) (CAS 56706-10-6) and 4,4,14,14-tetraethoxy-3,15-dioxa-8,9,10-trithia-4,14-disilaheptadecane (S3) (CAS 56706-11-7), referred to as reaction mass of S2 and S3, is composed of 50-65% S2, 30-40% S3 (both considered constituents) and 5-15% S4 (considered as an impurity).

The predicted water solubility of the constituents of the substance is low (≤1 mg/l) and the predicted log K_ow is high (5.2).

The hydrolysis half-lives of the constituents of the reaction mass of S2 and S3 are predicted to be 40-90 h at pH 7, 20-25°C for S2 and 40-110 h at pH 7, 20-25°C for S3. The registration substance will hydrolyse in contact with water and atmospheric moisture to (3-{[3-(trihydroxysilyl)propyl]disulfanyl}propyl)silanetriol for S2 and (3-{[3-(trihydroxysilyl)propyl]trisulfanyl}propyl)silanetriol for S3. The non-silanol hydrolysis product of both constituents is ethanol.

 

No ecotoxicity studies are available for the registration substance itself. However, data are available for substances that make up the constituents of the reaction mass of S2 and S3.

 

It is likely that under the conditions of the tests reported in Section 6.1 (Section 7.1 of the CSR), the test organisms would have been exposed to a mixture of the parent and hydrolysis products of the constituents of the test materials. However, test results suggest that, although the substances themselves appear to be non-toxic at the solubility limit, the hydrolysis products have non-classifiable effects which, under the conditions of the test, may have been exacerbated by or caused mainly by physical effects of undissolved or precipitated test materials or by-products.

 

In light of the properties of the registration substance, it is possible that short-term studies may have under-estimated the potential for toxicity. Therefore, although there is no clear evidence of effects attributable to the parent substance, it is appropriate to derive PNECs and conduct risk characterisation to ensure risks are appropriately managed.

 

Exposure assessment and risk characterisation will be based on the properties of the parent substance. Since there is significant uncertainty on the half-life range, exposure and risk for the soil and sediment protection targets will also be conducted using the properties of the hydrolysis product for comparison. As described in Section 4.8 (Section 1.3 of the CSR), the silanol hydrolysis products may be susceptible to condensation reactions.

 

READ-ACROSS JUSTIFICATION

In order to reduce animal testing read-across is proposed to fulfil REACH Annex IX requirements for the registration substance from substances that have similar structure and physicochemical properties. Ecotoxicological studies are conducted in aquatic medium or in moist environments; therefore the hydrolysis rate of the substance is particularly important, because after hydrolysis occurs the resulting product has different structural features, physicochemical properties and behaviour.

 

The registration substance and the substances used as surrogate for read-across are part of a class of low-functionality compounds acting via a non-polar narcosis mechanism of toxicity. The group of organosilicon substances in this group contain alkyl, aryl, alkoxy or hydroxy groups attached to the silicon atom when present in aqueous solution. Secondary features may be present in the alkyl chain (e.g. halogen, nitrile, unsaturated bonds) that do not affect the toxicity of the substances. The silanol hydrolysis products may be susceptible to condensation reactions, see Section 4.8 (Section 1.3 of the CSR).

 

Additional information is given in a supporting report (PFA 2016y) attached in Section 13 of the IUCLID dossier.

 

No short-term aquatic toxicity data are available for the registration substance, therefore these endpoints are addressed using a weight of evidence approach from data for two related substances: 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane (S2, CAS 56706-10-6) and polysulfides, bis[3-(triethoxysilyl)propyl] (CAS 211519-85-6). These substances can be reliably used to read across to the S2 and S3 reaction mass because they are structural analogues: CAS 56706-10-6 is equivalent to the S2 constituent of the S2 and S3 reaction mass; while CAS 211519-85-6 is a reaction mass containing principally the S2, S3 and S4 constituents, thus sharing the S2 and S3 constituents with the registration substance. 

 

The analogue approach for fulfilling the data requirement by read-across is discussed below, according to the Read-across Assessment Framework (RAAF).

The registered substance (target substance), reaction mass of 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane and 4,4,14,14-tetraethoxy-3,15-dioxa-8,9,10-trithia-4,14-disilaheptadecane (reaction mass of S2 and S3 (CAS 56706-10-6 and 56706-11-7, respectively)); herein referred to as reaction mass of S2 and S3, and the following substances used as surrogate for read-across (source substances), polysulfides, bis[3-(triethoxysilyl)propyl] (CAS 211519-85-6); herein referred to as Polysulfides, and from 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane (CAS 56706-10-6); herein referred to as S2, are part of a group of sulfidosilane substances which are essentially made up of the same substances, but present in different compositions. They hydrolyse to produce structurally similar silanol hydrolysis products and another non-Si hydrolysis product.

 

In the context of the RAAF, the basis of the read-across hypothesis for this substance is “Different compounds have the same type of effect(s)”; Scenario 2 applies. Both the source and target substance hydrolyse to compounds with qualitatively similar properties. The non-common hydrolysis products will not have an impact on the prediction of the ecotoxicological property. 

 

 

Read-across from 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane (S2) (CAS 56706-10-6) to reaction mass of 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane and 4,4,14,14-tetraethoxy-3,15-dioxa-8,9,10-trithia-4,14-disilaheptadecane (reaction mass of S2 and S3 (CAS 56706-10-6 and 56706-11-7, respectively)):

 

This scenario covers the analogue approach for which the hypothesis is based on different compounds with the same type of effect(s). For the REACH information requirement under consideration, the effects obtained in a study conducted with one source substance are used to predict the effects that would be observed in a study with the target substance if it were to be conducted. The same type of effect(s) or absence of effect is predicted. The predicted strength of the effects may be similar or based on a worst-case approach.

 

AE A.1 Characterisation of source and target substances

The substances are members of a group substances for registration, the sulfidosilanes. The target substance is a reaction mass of 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane (S2) and 4,4,14,14-tetraethoxy-3,15-dioxa-8,9,10-trithia-4,14-disilaheptadecane (S3), comprising of approximately 50-65% of the S2 constituent and 30-40% of the S3 constituent. 4,4,15,15 -Tetraethoxy-3,16-dioxa-8,9,10,11-tetrathia-4,15-disilaoctadecane (S4) is present as an impurity at 5-15%. Both S2, S3 and S4 are bis[3-(triethoxysilyl)propyl]- structures with the two (triethoxysilyl)propyl groups linked by a di-, tri- or tetrasulfide group.

The source substance is the monoconstituent substance S2 (CAS 56706-10-6). S2 is one of the constituents of the registered substance and includes S3 as an impurity.

The constituents of the target substance and the constituents of the source substance are structurally very similar; each has two common functional groups (3-(triethoxysilyl)propyl) and a linking sulfide group with two or three sulfur atoms.

The substances are susceptible to hydrolysis. Predicted hydrolysis half-lives were determined for the constituents of the target substance using a validated QSAR estimation method: approximately 40 – 90 h at pH 7 (20-25°C) for S2 and approximately 40 – 110 h at pH 7 for S3. The half-life for S2 as part of the target reaction mass is directly comparable to S2 as the monoconstituent source substance.

S2 hydrolyses to produce (3-{[3-(trihydroxysilyl)propyl]disulfanyl}propyl)silanetriol and ethanol; S3 hydrolyses to produce (3-{[3-(trihydroxysilyl)propyl]trisulfanyl}propyl)silanetriol and ethanol.

 

The target substance, reaction mass of S2 and S3, and the source substance, S2, share similar physicochemical properties: high log K_ow (both 5.2), low water solubility (<1 mg/l and 1 mg/l, respectively) and high molecular weight (MW 474.8-506.9 and 474.8 g mol-1, respectively).

During the tests with the source substance, test organisms are expected to have been exposed to a mixture of the parent substance, undissolved tests material, the hydrolysis products of the test substance and aggregated hydrolysis product.

 

AE A.2 Link of structural similarities and structural differences with the proposed prediction (presence of hypothesis)

The target and source substances are composed of varying proportions of bis-[3-(triethoxysilyl)propyl]sulfides with a varying number of sulfur atoms in the sulfide bridge. Constituents of the substances have 2-3 sulfur atoms; impurities may be present with 1 or >4 sulfur atoms.

The constituents and major impurities of the target and source substances have two functional groups in common:

·        The triethoxysilane, Si(OEt)₃, group (there are two of these per molecule, therefore each molecule has six reactive ethoxy groups).

·        The (poly)sulfide, CH₂S_nCH₂(n = 1-4), group.

None of the substances contain functional groups that are not present in the other substances. The only difference between the constituents/major impurities is the number of sulfur atoms in the sulfide bridge.

The hydrolysis products are bothbis(3-(trihydroxysilyl)propylsulfides with a variation in the number of sulfur atoms (two or three).

Due the very similar chemical structures, the substances and constituents as well as the hydrolysis products are predicted to have near identical physicochemical properties, with high log K_ow, low water solubility and low vapour pressure (see Table 7.0.1 below).

 

Consideration of the non-Si hydrolysis product ethanol:

Ethanol, produced upon hydrolysis of the both the source substance and target substance, is well characterised in the public domain literature and is not hazardous at the concentrations relevant to the studies; the short-term EC₅₀ and LC₅₀ are in excess of 1000 mg/l (OECD 2004b - SIDS for ethanol, CAS 64-17-5). 

 

AE A.3 Impact of impurities on the prediction

The target substance, reaction mass of S2 and S3, is composed of 50-65% S2, 30-40% S3 both considered constituents, and 5-15% S4, considered as an impurity. It also contains higher sulphide impurities (Sn n>4) at 0-5%.

The source substance, S2, is composed of 80-90% S2 considered as a constituent, and 10-20% S3, 0-5% S4 and <1% higher sulfides, considered as impurities.

The other impurities present at >1% in the submission substance are alkoxysilanes (0-5% of the substance in total). They are also present in the read-across substance S2. The structures cannot be specified here to preserve confidentiality within the Reconsile Consortium. However, the compositions of the various companies’ products have been reviewed by an external expert. The profile of non-sulfide impurities in each product is compatible with read-across. These impurities are present at very low levels (<3% in total of the substance).

It is therefore concluded that the source and target substances do not contain impurities at concentrations that would influence the effects observed in the available tests with the source substance. 

 

AE A.4 Consistency of properties in the data matrix

Short-term toxicity to fish, invertebrates and algae data are read across from S2:

Short-term toxicity to fish: 96 h LC₅₀ >1000 mg/l (highest concentration tested), Danio rerio.

Short-term toxicity to aquatic invertebrates: 48 h EC₅₀ <1 mg/l (lowest concentration tested), Daphnia magna and 48 h EC₅₀ 4 mg/l Daphnia magna.

Toxicity to aquatic algae: 72 h EC₅₀ >500 mg/l; EC₁₀ 280 mg/l and NOEC 32 mg/l, Desmodesmus subspicatus.

 

There are no other reliable short-term toxicity data available with S2.

No long-term toxicity data are available with S2.

The aquatic toxicity data for the target substance indicates that it is not acutely toxic to aquatic organisms at the limit of solubility, although physical effects occur when the solubility limit is exceeded and when cross-linking of the silanols can occur.

 

AE A.5 Reliability and adequacy of the source data

All key data included in the chemical safety assessment have been reviewed and assigned Klimisch scores of 1 or 2.

 

AE A.6 Bias that influences the prediction

Data with the source substance, S2, were selected because it is the same substance as the main constituent of the target substance.

Short-term toxicity to aquatic organisms data available with another substance in the sulfidosilane group have also been included in the chemical safety assessment and are discussed below. 

 

 

Read-across from polysulfides, bis[3-(triethoxysilyl)propyl] (CAS 211519-85-6) to reaction mass of 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane and 4,4,14,14-tetraethoxy-3,15-dioxa-8,9,10-trithia-4,14-disilaheptadecane (reaction mass of S2 and S3 (CAS 56706-10-6 and 56706-11-7, respectively)):

This scenario covers the analogue approach for which the hypothesis is based on different compounds with the same type of effect(s). For the REACH information requirement under consideration, the effects obtained in a study conducted with one source substance are used to predict the effects that would be observed in a study with the target substance if it were to be conducted. The same type of effect(s) or absence of effect is predicted. The predicted strength of the effects may be similar or based on a worst-case approach.

 

AE A.1 Characterisation of source and target substances

The substances are members of a group substances for registration, the sulfidosilanes. The target substance is a reaction mass of 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane (S2) and 4,4,14,14-tetraethoxy-3,15-dioxa-8,9,10-trithia-4,14-disilaheptadecane (S3), comprising of approximately 50-65% of the S2 constituent and 30-40% of the S3 constituent. 4,4,15,15 -Tetraethoxy-3,16-dioxa-8,9,10,11-tetrathia-4,15-disilaoctadecane (S4) is present as an impurity at 5-15%. Both S2, S3 and S4 are bis[3-(triethoxysilyl)propyl]- structures with the two (triethoxysilyl)propyl groups linked by a di-, tri- or tetrasulfide group.

The source substance is the multi-constituent substance Polysulfides (CAS 211519-85-6). The constituents of the target substance are found in the multiconstituent read-across substance, Polysulfides, which is a reaction mass of S2, S3 and S4.

The constituents of the target substance and the constituents of the source substances are essentially the same substances but in different proportions and are structurally very similar; each has two common functional groups (3-(triethoxysilyl)propyl) and a linking sulfide group with two, three or four sulfur atoms.

The substances are susceptible to hydrolysis. Predicted hydrolysis half-lives were determined for the constituents of the target substance using a validated QSAR estimation method: approximately 40 – 90 h at pH 7 (20-25°C) for S2 and approximately 40 – 110 h at pH 7 for S3.

The three constituents of the source substance polysulfides, bis[3-(triethoxysilyl)propyl] have predicted hydrolysis half-lives of 40-90 h at pH 7, 20-25°C for S2, 40-110 h at pH 7, 20-25°C for S3 and 40-130 h at pH 7, 20-25°C for S4. All hydrolyse to silanetriol analogues and ethanol: S2 hydrolyses to produce (3-{[3-(trihydroxysilyl)propyl]disulfanyl}propyl)silanetriol and ethanol; S3 hydrolyses to produce (3-{[3-(trihydroxysilyl)propyl]trisulfanyl}propyl)silanetriol and ethanol, and S4 hydrolyses to [3-({[3-(trihydroxysilyl)propyl]disulfanyl}disulfanyl)propyl]silanetriol and ethanol.

 

The target substance, reaction mass of S2 and S3, and the source substance, polysulfides, share similar physicochemical properties: high log K_ow (5.2 for each constituent), low water solubility (both <1 mg/l) and high molecular weight (MW 474.8-506.9 and 474.8 to 538.9 g mol-1, respectively).

During the tests with the source substance, test organisms are expected to have been exposed to a mixture of the parent substance, undissolved tests material, the hydrolysis products of the test substance and aggregated hydrolysis product.

 

AE A.2 Link of structural similarities and structural differences with the proposed prediction (presence of hypothesis)

The target and source substances are composed of varying proportions of bis-[3-(triethoxysilyl)propyl]sulfides with a varying number of sulfur atoms in the sulfide bridge. Constituents of the substances have 2-4 sulfur atoms; impurities may be present with 1 or >4 sulfur atoms.

The constituents and major impurities of the target and source substances have two functional groups in common:

·        The triethoxysilane, Si(OEt)₃, group (there are two of these per molecule, therefore each molecule has six reactive ethoxy groups).

·        The (poly)sulfide, CH₂S_nCH₂(n = 1-4), group.

None of the substances contain functional groups that are not present in the other substances. The only difference between the constituents/major impurities is the number of sulfur atoms in the sulfide bridge.

The hydrolysis products are allbis(3-(trihydroxysilyl)propylsulfides with a variation in the number of sulfur atoms (two or three).

Due the very similar chemical structures, the substances and constituents as well as the hydrolysis products are predicted to have near identical physicochemical properties, with high log K_ow, low water solubility and low vapour pressure (see Table 7.0.1 below).

 

Consideration of the non-Si hydrolysis product ethanol:

Ethanol, produced upon hydrolysis of the both the source substance and target substance, is well characterised in the public domain literature and is not hazardous at the concentrations relevant to the studies; the short-term EC₅₀ and LC₅₀ are in excess of 1000 mg/l (OECD 2004b - SIDS for ethanol, CAS 64-17-5). 

 

AE A.3 Impact of impurities on the prediction

The target substance, reaction mass of S2 and S3, is composed of 50-65% S2, 30-40% S3 both considered constituents, and 5-15% S4, considered as an impurity. It also contains higher sulphide impurities (Sn n>4) at 0-5%.

The source substance, polysulfides, is composed of ≥15 to ≤25% S2, ≥25 to ≤35 % S3 and ≥20 to ≤30 S4, all considered as constituents, and 5-20% S5 (4,4,16,16-tetraethoxy-3,17-dioxa-8,9,10,11,12-pentathia-4,16-disilaoctadecane) considered as an impurity. The other impurities include other bis[3-triethoxysilyl)propyl]sulfides, sulfur, trialkoxysilanes and ethanol.

The other impurities present at >1% in the submission substance are alkoxysilanes (0-5% of the substance in total). The structures cannot be specified here to preserve confidentiality within the Reconsile Consortium. However, the compositions of the various companies’ products have been reviewed by an external expert. The profile of non-sulfide impurities in each product is compatible with read-across. These impurities are present at very low levels (<3% in total of the substance).

It is therefore concluded that the source and target substances do not contain impurities at concentrations that would influence the effects observed in the available tests with the source substance. 

 

AE A.4 Consistency of properties in the data matrix

Short-term toxicity to fish, invertebrates and algae data are read across from polysulfides:

Short-term toxicity to fish: 96 h LC₅₀ >10000 mg/l (highest concentration tested), Danio rerio.

Short-term toxicity to aquatic invertebrates: 48 h EC₅₀ >10 mg/l (highest concentration tested), Daphnia magna.

Toxicity to aquatic algae: 96 h EC₅₀ 700 mg/l; EC₁₀ 60 mg/l and NOELR 1000 mg/l, Desmodesmus subspicatus.

 

There are no other reliable short-term toxicity data available with polysulfides.

No long-term toxicity data are available with polysulfides.

The aquatic toxicity data for the target substance indicates that it is not acutely toxic to aquatic organisms at the limit of solubility, although physical effects occur when the solubility limit is exceeded and when cross-linking of the silanols can occur.

 

AE A.5 Reliability and adequacy of the source data

All key data included in the chemical safety assessment have been reviewed and assigned Klimisch scores of 1 or 2.

 

AE A.6 Bias that influences the prediction

Data with the source substance, polysulfides, were selected because it contains the same substances as the main constituents of the target substance.

Short-term toxicity to aquatic organisms data available with another substance in the sulfidosilane group have also been included in the chemical safety assessment and are discussed above.

 

Table 7.0.1 Physicochemical properties of the S2, S3 and S4 constituents

Property	S2	S3	S4
Name	4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane	4,4,14,14-tetraethoxy-3,15-dioxa-8,9,10-trithia-4,14-disilaheptadecane	4,4,15,15-tetraethoxy-3,16-dioxa-8,9,10,11-tetrathia-4,15-disilaoctadecane
CAS Number	56706-10-6	56706-11-7	40372-72-3
Hydrolysis product	(3-{[3-(trihydroxysilyl)propyl]disulfanyl}propyl)silanetriol	(3-{[3-(trihydroxysilyl)propyl]trisulfanyl}propyl)silanetriol	[3-({[3-(trihydroxysilyl)propyl]disulfanyl}disulfanyl)propyl]silanetriol
Molecular weight	474.8 g mol‑1	506.9 g mol-1	538.9 g mol-1
log Kow (parent)	5.2 (predicted)	5.2 (predicted)	5.2 (predicted)
log Kow (silanol hydrolysis product)	-3.0 (predicted)	-3.0 (predicted)	-3.0 (predicted)
Water solubility (parent)	1 mg/l (measured) 0.01 mg/l (predicted)	< 1 mg/l (read across from S2 and S2/S3/S4 reaction mass)  0.01 mg/l (predicted)	< 1 mg/l (read across from S2 and S2/S3/S4 reaction mass)  0.01 mg/l (predicted)
Water solubility (silanol hydrolysis product)	1,000,000 mg/l (predicted) (will be limited by formation of condensation products)	1,000,000 mg/l (predicted)  (will be limited by formation of condensation products)	1,000,000 mg/l (predicted)  (will be limited by formation of condensation products)
Vapour pressure (parent)	9 Pa (measured)  20°C 0.46 Pa (predicted)	9 Pa (read across from S2)  20°C 0.44 Pa (predicted)	9 Pa (read across from S2)  20°C
Vapour pressure (hydrolysis product)	2.9E-05 Pa (predicted) 25°C	2.9E-05 Pa (predicted) 25°C	2.9E-05 Pa (predicted) 25°C
Hydrolysis t1/2 at pH 7 and 25°C	40-90 h(predicted)	40-110 h (predicted)	40-130 h (predicted)

 

Table 7.0.2 Ecotoxicological data available for substances in the sufidosilanes analogue group

CAS Number	56706-10-6	211519-85-6
Chemical Name	4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane	Reaction mass of 4,4,15,15-tetraethoxy-3,16-dioxa-8,9,10,11-tetrathia-4,15-disilaoctadecane and 4,4,14,14-tetraethoxy-3,15-dioxa-8,9,10-trithia-4,14-disilaheptadecane and 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane
Short-name	S2	Polysulfides, S2, S3, S4
Short-term toxicity to fish (LL50)	>1000 mg/l	>10000 mg/l
Short-term toxicity to aquatic invertebrates (EL50)	<1 mg/l* and 4 mg/l*	>10 mg/l
Algal inhibition (EL50 and NOELR)	EL50: >500 mg/l and NOELR: 32 mg/l	EL50: 700 mg/l and EL10: 60 mg/l

 * It is not possible to determine whether the effects observed in this study are due to the presence of undissolved test material or to the toxicity of the substance.

Conclusion on classification

The substance has reliable short-term E(L)C₅₀ values of >1000 mg/l in fish, >10 mg/l in invertebrates and 700 mg/l in algae, based on read-across from structural analogues. It has a reliable NOEC of 60 mg/l in algae also based on read-across from a structural analogue. The available short- and long-term aquatic toxicity data indicate that there are no effects on aquatic organisms at the limit of solubility of the substance in water.

The substance is slightly soluble, hydrolyses moderately to slowly in water, it is not readily biodegradable and has a high predicted log K_ow of 5.2. The silanol hydrolysis products are highly soluble and have low log K_ow.

These data are consistent with the following classification under Regulation (EC) No 1272/2008 (as amended) (CLP):

Acute toxicity: Not classified.

Chronic toxicity: Not classified.