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Toxicity to microorganisms

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Description of key information

Toxicity to microorganisms: EC50 >100 mg/l (ASRI), read-across from a structurally-related substance.

Key value for chemical safety assessment

Additional information

There are no reliable microorganism toxicity data available for L6, therefore good quality data for the structurally-related substance, decamethyltetrasiloxane, L4, (CAS 141 -62 -8), have been read across. L6 and L4 are structurally-similar substances, both are linear siloxanes.

L4 is a linear siloxane chain with four silicon atoms, connected by three oxygen atoms. All silicon atoms present are fully substituted with methyl groups. L6 is a structurally related linear siloxane, with six silicon atoms and five oxygen atoms.

L6 and L4 are within an analogue group of siloxane substances within which, in general, there is no evidence of significant toxicity to microorganisms.

The table below presents microorganism toxicity data for substances within the analogue group (I-3) of siloxanes (alkyl, vinyl, aryl or hydrogen substituted).

It is therefore considered valid to read-across the results for L4 to fill the data gap for the registered substance.Additional information is given in a supporting report (PFA, 2015i) attached in Section 13.

Table: Microorganism toxicity data for substances within the siloxane analogue group (I-3) of chemicals

CAS

Name

Result: E(I)C50

Result: NOEC (or EC10/ EC20)

Guideline Number

Duration

Reliability

540-97-6

Dodecamethylcyclohexasiloxane

>100 mg/l

 

OECD 209

3hr

1

541-05-9

Hexamethylcyclotrisiloxane

>100 mg/l

>100 mg/l

OECD 209

3hr

1

541-02-6

Decamethylcyclopentasiloxane

>2000 mg/l

 

C11

3hr

1

556-67-2

Octamethylcyclotetrasiloxane

>10 000 mg/l

 

ISO 8192 (Test for Inhibition of Oxygen Consumption by Activated Sludge)

3hr

4 (WoE)

556-67-2

Octamethylcyclotetrasiloxane

little or no toxicity (24 h): 0.1 g/g solution test mat. based on: reduction in number of viable bacteria

 

Toxicity toEscherichia coliandStaphylococcus aureusat 37°C for 24 hours

24hr

4 (WoE)

107-46-0

Hexamethyldisiloxane

>100 mg/l

≥100 mg/l

OECD 209

3hr

1

141-62-8

Decamethyltetrasiloxane

>100 mg/l

 

OECD 209

3hr

1

352230-22-9

Siloxanes and Silicones, di-Ph, Ph (trimethylsilyl)oxy

>1000 mg/l

≥1000 mg/l

OECD 209

3hr

1

2627-95-4

1,1,3,3-tetramethyl-1,3-divinyldisiloxane

>1000 mg/l

≥1000 mg/l

Nitrification control indicated no heterotrophic inhibition of respiration rate

OECD 209

3hr

1

2554-06-5

2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane

>1000 mg/l

≥1000 mg/l

Nitrification control indicated no heterotrophic inhibition of respiration rate

OECD 209

3hr

1

70131-69-0

Silsesquioxanes, Phenyl

>1000 mg/l

≥1000 mg/l

Nitrification control indicated no heterotrophic inhibition of respiration rate

OECD 209

3 h

1

99363-37-8

dimethyl, methyl(3-aminopropyl) siloxane, trimethylsiloxy-terminated

> water soluble fraction

≥ water soluble fraction

OECD 209

3hr

1

71750-79-3

dimethyl, (aminoethylaminopropyl)methyl siloxane, trimethylsiloxy-terminated

> water soluble fraction

≥ water soluble fraction

OECD 209

3hr

1

WoE = Weight of evidence

In the study with L4,an activated sludge respiration inhibition 3 hour EC50value of >100 mg/l was reported.

Reference:

Peter Fisk Associates (2015i), Peter Fisk Associates. Siloxane analogue report. PFA.404.005.008.R2