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Toxicity to microorganisms

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Description of key information

Toxicity to microorganisms: ASRI 3 hours EC10 >100 mg/L (loading rate) (OECD 209), read-across from a structurally-related substance.

Key value for chemical safety assessment

Additional information

There are no reliable microorganism toxicity data available for trimethoxy(vinyl)silane (CAS No. 2768-02-7), therefore good quality data for the structurally-related substance, trichloro(vinyl)silane (CAS No. 75-94-5), have been read across. Both substances share the same silanol hydrolysis product, vinylsilanetriol. The other hydrolysis products are methanol and hydrogen chloride/chloride salts respectively.

Methanol does not have adverse effects on microorganisms (OECD 2004).

Hydrogen chloride is not expected to have adverse effects on microorganisms in a sewage treatment plant, where the pH is maintained within a favourable range.

Trimethoxy(vinyl)silane (CAS No. 2768-02-7) and trichloro(vinyl)silane (CAS No. 75-94-5) are within an analogue group of substances within which, in general, there is no evidence of significant toxicity to microorganisms.

This analogue group for the toxicity to microorganisms endpoint consists of a number of sub-classes of substances with different main codes. However, read-across is carried out between substances with the same main code in most cases. In this case read-across from a different sub-class is used, from

the sub-class I-2-T-C (Trichlorosilanes) to the sub-class I-2-T-Me-H (Trimethoxysilanes hydrolysing rapidly at pH 7). This is because the I-2 -T-Me-H sub-class does not contain any substances with a vinyl side-chain, and it was thought important to cover this structural feature. The two substances have a very rapid rate of hydrolysis in common.

It is therefore considered valid to read-across the results for trichloro(vinyl)silane (CAS No. 75-94-5) to fill the data gap for the registered substance. Additional information is given in a supporting report (PFA, 2013j) attached in Section 13.

The table below presents microorganism toxicity data available for substances within the sub-classes I-2 -T-C and I-2 -T-Me-H.

Table 7.3.2: Microorganism toxicity data available for substances within the relevant sub-classes I-2-T-Me-H and I-2-T-C of chemicals

CAS No.

Chemical Name (CAS Name)

Main code

Guideline Number

Test method

PFA Klimisch code

Year

Duration (hours)

Result: E(I)C50 (mg/L)

Result: NOEC (Or EC10/EC20) (mg/L)

Study ID Code[1]

5894-60-0

Trichloro(hexadecyl)silane

I-2-T-C

OECD 209

ASRI

1

 

3

>1000

=1000

6.1.7.075

75-94-5

Trichloro(vinyl)silane

I-2-T-C

OECD 209

ASRI

1

2009

3

>100

 

6.1.7.043

87135-01-1

1,6-Bis(trimethoxysilyl)hexane

I-2-T-Me-H

OECD 209

ASRI

1

2009

3

>1000

 

6.1.7.062

16415-12-6

Hexadecyltrimethoxysilane

I-2-T-Me-H

OECD 209

ASRI

1

 

3

>1000

 

6.1.7.077


[1]This is a unique internal ID code which can be used to identify the reference for the study.

In the study with trichloro(vinyl)silane (CAS No. 75 -94-5), an activated sludge respiration inhibition 3h EC10value of >100 mg/L was reported.

A supporting study for the registration substance is available. An EC10 1.1 ml/L (Oxygen consumption test (Huls method)) was determined in an oxygen consumption test with Pseudomonas putida. The test was conducted in accordance with generally accepted scientific standards and described in sufficient detail and in compliance with GLP, with acceptable restrictions. The restrictions were that a reference substance was not used to check the sensitivity of the microorganisms, and an emulsifier was used which could have affected the results. In view of these factors, the study is unsuitable for PNEC derivation.

Two other results are available, the reliability of which are not assignable as they are reported in secondary literaure. The results are NOEC >=1000 mg/L (Bement 2001) and IC50 >2500 mg/L (Chandra 1997).

Reference:

PFA, 2013j, Peter Fisk Associates, STP Microorganism toxicity Main Analogue Group report, PFA.300.003.006