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Toxicity to microorganisms

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Description of key information

Toxicity to microorganisms: 3 hour 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 L5.

A category approach is applied to this endpoint and is detailed in the Siloxane Category report (PFA, 2017). The hypothesis for read-across is that siloxane substances exhibit no evidence of significant toxicity to sewage treatment plant microorganisms. This is consistent with a non-polar narcosis mode of action. Therefore, good quality data for the structurally-related substance, decamethyltetrasiloxane, L4, (CAS 141-62-8), have been read across to L5.

L5 and L4 are members of the Reconsile Siloxanes Category within which, in general, the substances exhibit no evidence of significant toxicity to microorganisms.

The table below presents microorganism toxicity data available for substances within the Siloxanes Category.

 Additional information is given in a supporting report (PFA, 2017) attached in Section 13 of the IUCLID 6 dossier.

Table: Microorganism toxicity data for substances within the Siloxane Category

CAS

Name

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

Result: NOEC (or EC10/ EC20) (mg/l)

Guideline Number

Duration

Reliability

540-97-6

Dodecamethylcyclohexasiloxane

>100 mg/l

 

OECD 209

3hr

1a

541-05-9

Hexamethylcyclotrisiloxane

>100 mg/l

>100 mg/l

OECD 209

3hr

1a

541-02-6

Decamethylcyclopentasiloxane

>2000 mg/l

 

C11

3hr

1a

556-67-2

Octamethylcyclotetrasiloxane

>10 000 mg/l

 

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

3hr

4e (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

4e (WOE)

107-46-0

Hexamethyldisiloxane

>100

≥100

OECD 209

3hr

1a

141-62-8

Decamethyltetrasiloxane

>100 mg/l

 

OECD 209

3hr

1a

352230-22-9

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

>1000 mg/l

≥1000 mg/l

OECD 209

3hr

1a

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

1a

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

1a

70131-69-0

Silsesquioxanes, Phenyl

>1000

≥1000

Nitrification control indicated no heterotrophic inhibition of respiration rate

OECD 209

3 h

1a

99363-37-8

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

> water soluble fraction

≥ water soluble fraction

OECD 209

3hr

1a

71750-79-3

dimethyl, (aminoethylaminopropyl)methyl siloxane, trimethylsiloxy-terminated

> water soluble fraction

≥ water soluble fraction

OECD 209

3hr

1a

In the study with L4, an activated sludge respiration inhibition 3 hour EC50 value of >100 mg/l was reported.