Registration Dossier

Administrative data

Description of key information

Oral : 1300 mg/kg bw (RTECS). 
Dermal: No data available
Inhalation: LCLo50 = 2270 ppm/4h (RTECS)

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
LD50
1 300 mg/kg bw
Quality of whole database:
No data available

Acute toxicity: via inhalation route

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
discriminating conc.
Quality of whole database:
Value 2270 ppm/4 h. No data available.

Acute toxicity: via dermal route

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Acute toxicity: oral

In a study performed with the read accross substance (chloromethyl)triethoxysilane CAS RN 15267-95-5 the test item was investigated for acute oral toxicity according to the OECD TG 420, and in compliance with GLP. To determine the dose level for the main study, two sighting studies were conducted with one female Wistar rat each. The two animals were treated sequentially with the undiluted test item at the dose levels of 300 or 2000 mg/kg bw, respectively, by single oral gavage administration. All animals were examined for mortality and clinical signs before treatment, within the first 30 minutes and approximately 1, 2, 3 and 5 hours after treatment on test day 1 and once daily during test days 2-15. Body weights were recorded on test day 1 (prior to administration) and on test days 8 and 15. All animals were necropsied and macroscopically examined.

Since no mortality occurred during the sighting study up to 2000 mg/kg, additional four females were treated at this dose level in the main study. One animal treated at 2000 mg/kg was found dead on day 2 of the main study. All other animals survived the scheduled treatment and observation periods. In the animal treated at 300 mg/kg during sighting study, decreased activity, hunched posture and ruffled fur were noted on test day 1. Thereafter, the animal was free of clinical signs up to the end of the observation period. In the animals treated at 2000 mg/kg, dragging of limbs, decreased activity, hunched posture, ruffled fur and/or swaying gait were noted on test day 1 and persisted up to test day 3 at the latest. Thereafter, no clinical signs were noted up to study termination on day 15. The body weight of the animals was within the range commonly recorded for this strain and age. In the animal that died spontaneously, distended stomach was recorded at necropsy. No abnormal macroscopic findings were recorded in the remaining animals at scheduled necropsy.

Read-across justification

 

There is one measured data available for (Chloromethyl)diethoxymethylsilane (CAS 2212-10-4) for acute toxicity. However, as the result is sourced from secondary literature (RTECS) only, without access to the original reference for review and no further information is available the reliability of the study is not assignable. This document describes the analogue approach for fulfilling this endpoint by read-across from a source substance (Chloromethyl)triethoxysilane (CAS 15267-95-5), according to the Read-across Assessment Framework (RAAF)[1].

Read-across is proposed in accordance with RAAF Scenario 2: “This scenario covers the analogue approach for which the read-across hypothesis is based on different compounds which have 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.” The read-across justification is presented (Table 5.6.4) according to RAAF scenario 2 assessment elements (AE) as outlined in Table B1 of the RAAF1:

 

Table 1: RAAF scenario 2 assessment elements (AE) as given in Appendix B (Table B1) of the RAAF1

AE A.1

Characterisation of source substance

AE A.2

Link of structural similarity and differences with the proposed Prediction

AE A.3

Reliability and adequacy of the source study

AE 2.1

Compounds the test organism is exposed to

AE 2.2

Common underlying mechanism, qualitative aspects

AE 2.3

Common underlying mechanism, quantitative aspects

AE 2.4

Exposure to other compounds than to those linked to the prediction

AE 2.5

Occurrence of other effects than covered by the hypothesis and Justification

AE A.4

Bias that influences the prediction

 

1. AE A.1 Identity and characterisation of the source substance

 

The source substance, (Chloromethyl)triethoxysilane (CAS 15267-95-5) contains a chloromethyl silane group in addition with an ethoxy moiety. (Chloromethyl)triethoxysilane hydrolyses rapidly to form (chloromethyl)silanetriol (1 moles) and ethanol (3 moles) under conditions relevant in the environment or in vivo, with a half-life of 2.5 h. A half-life value of approximately 2.5 h at 20-25°C and pH 7 was obtained using an accepted validated QSAR method.

At pH 2 (the known pH of the stomach), the calculated hydrolysis rate is approximately 5 seconds.

The source substance has log Kow of 2.5 at 20°C (QSAR), water solubility of 1.1E+03 mg/l at 20°C (QSAR) and vapour pressure of 6.5 Pa at 25°C (QSAR).

 

2. AE A.2 Link of structural similarities and differences with the proposed prediction

The registration substance, (Chloromethyl)diethoxymethylsilane (CAS 2212-10-4), and the read-across substance, (Chloromethyl)triethoxysilane (CAS 15267-95-5), are structurally similar. (Chloromethyl)triethoxysilane (CAS 15267-95-5) contains a chloromethyl silane group in addition to three ethoxy-groups attached to the Si atom, while in (Chloromethyl)diethoxymethylsilane (CAS 2212-10-4) only two ethoxy-groups are attached to the Si atom of the chloromethyl silane group and the third ethoxy group is substituted by a methyl group.

This structural difference remains in the Si-containing hydrolysis product for the target and source substance. The Si hydrolysis product for the target substance is (chloromethyl)methylsilanediol while the Si hydrolysis product for the source substance is chloromethylsilanetriol.

 

Table 2: Physico-chemical properties

 

Property

 

Target substance

 

Source substance

 

Substance name

 

(Chloromethyl)diethoxymethylsilane

 

(Chloromethyl)triethoxysilane

 

CAS number

 

2212-10-4

 

15267-95-5

 

Hydrolysis half-life at pH 4 and 20 - 25°C

 

1.1 – 24 min (QSAR)

 

12 min (QSAR)

 

Silanol hydrolysis product

 

(chloromethyl)methylsilanediol

 

chloromethylsilanetriol

 

Non-Si hydrolysis product

 

Ethanol

 

Ethanol

 

LogKow Value

 

1,82 at 25°C (QSAR)

 

2.5 at 20°C (QSAR)

 

Vapour pressure

 

25.2 hPa at 25°C (measured)

 

6.5 Pa at 25°C (QSAR)

 

Water solubility

 

1487 mg/L at 25°C (QSAR)

 

1.1E+03 mg/l at 20°C (QSAR)

 

 

 

3. AE A.3 Reliability and adequacy of the source study

 

In the available weight of evidence study (Harlan, 2012) the test item was investigated for acute oral toxicity according to the OECD TG 420, and in compliance with GLP.

One animal treated at 2000 mg/kg was found dead on day 2 of the main study. All other animals survived the scheduled treatment and observation periods. In the animal treated at 300 mg/kg during sighting study, decreased activity, hunched posture and ruffled fur were noted on test day 1. Thereafter, the animal was free of clinical signs up to the end of the observation period. In the animals treated at 2000 mg/kg, dragging of limbs, decreased activity, hunched posture, ruffled fur and/or swaying gait were noted on test day 1 and persisted up to test day 3 at the latest. Thereafter, no clinical signs were noted up to study termination on day 15. The body weight of the animals was within the range commonly recorded for this strain and age. In the animal that died spontaneously, distended stomach was recorded at necropsy. No abnormal macroscopic findings were recorded in the remaining animals at scheduled necropsy.

 

4. AE A.4 Bias that influences the prediction

 

Data on the source substance (Chloromethyl)triethoxysilane (CAS 15267-95-5) were read-across to the registered (target) substance (Chloromethyl)diethoxymethylsilane (CAS 2212-10-4). The source substance and the target substance have similar chemical structure and physico-chemical properties. Both substances hydrolyse at similar rate to a similar Si-containing hydrolysis product, chloromethylsilanetriol resp. (chloromethyl)methylsilanediol. The non-silanol hydrolysis product is the same, ethanol. Due to that, their toxicological properties are expected to be similar, with similar acute toxicity. No other data for relevant substances were available. This substance is the closest structural analogue to the target substance available.

 

5. AE A.2.1 Compounds the test organism is exposed to

 

Both substances hydrolyse rapidly in contact with water under conditions relevant for oral exposure. Therefore, the test organism is mainly exposed to their hydrolysis products, (chloromethyl)methylsilanediol, resp. chloromethylsilanetriol. The source and target substances have been profiled using the OECD QSAR Toolbox v. 4.1. The two substances and their silanol hydrolysis products show similar profiles for all toxicological endpoints. No alert for acute toxicity was detected by OECD QSAR Toolbox v.4.1. No classification for acute oral toxicity has been assigned to the substance.

 

6. AE A.2.2 and A.2.3 Common underlying mechanism, qualitative and quantitative aspects

 

No toxicity data are available for the target substance Chloromethyl)diethoxymethylsilane (CAS 2212-10-4), therefore data are read-across from the structurally analogous substance (Chloromethyl)triethoxysilane (CAS 15267-95-5). Both substances hydrolyse at similar rate to a similar Si-containing hydrolysis product, chloromethylsilanetriol resp. (chloromethyl)methylsilanediol. The non-silanol hydrolysis product, ethanol, is not expected to be relevant for this endpoint. Moreover, they have similar physico-chemical properties. Thus, both substances are expected to have similar toxicity profiles.

 

7. AE 2.4 Exposure to other compounds than to those linked to the prediction

 

The target substance, Chloromethyl)diethoxymethylsilane (CAS 2212-10-4), does not have any impurities of toxicological concern. The source substance, (Chloromethyl)triethoxysilane (CAS 15267-95-5), has a named impurity of approx. 1% is Ethanol (CAS 64-17-5). It is not expected that the ethanol impurity will contribute to the acute toxicity of the source substance. The test substance in the study with the source substance, (Chloromethyl)triethoxysilane (CAS 15267-95-5), has a purity of 97.3%.

 

8. AE 2.5 Occurrence of Other Effects than Covered by the Hypothesis and Justification

 

Not relevant.

 

[1] European Chemicals Agency (ECHA) (2015) Read-across Assessment Framework. Appendix B, Scenario 2.

In a RTECS data entry for Silane, chloromethylmethyldiethoxy- a LD 50 of 1300 mg/kg bw was recorded. Although no further details are available this value is taken into account as a worst case approach for classification and labelling.

Acute toxicity: dermal

No data available.

Acute toxicity: inhalation

In a RTECS data entry (reliability score 4) for Silane, chloromethylmethyldiethoxy- a LCLo of 2270 ppm/4h was recorded. No further details are available.


Justification for selection of acute toxicity – oral endpoint
The RTECS entry data was selected for assessment as this is the more senistive study result and performed with the test item.

Justification for selection of acute toxicity – inhalation endpoint

Reliable data is available for the oral route.


Justification for selection of acute toxicity – dermal endpoint
Reliable data is available for the oral route.

Justification for classification or non-classification

The available data are reliable and suitable for classification. Based on these data, classification for acute toxicity according to EC/1272/2008 is warranted according for actue oral toxicity category 4, H302.