Registration Dossier

Diss Factsheets

Ecotoxicological information

Toxicity to microorganisms

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

Toxicity to microorganisms: ASRI 3hr EC50 >10 000 mg/l (ISO 8192 (Test for Inhibition of Oxygen Consumption by Activated Sludge))

Key value for chemical safety assessment

Additional information

A study conducted according to a standard guideline (ISO 8192 (Test for Inhibition of Oxygen Consumption by Activated Sludge)) reported in a MSDS (GE Bayer 4/8/1998) gives an ASRI 3hr EC50 value of >10 000 mg/l. No further information is available and the reliability of the study cannot be determined.

A second study is available which investigates the toxicity to Escherichia coli and Staphylococcus aureus in aqueous solution. This study reports that after 24 hrs incubation at 37ºC D4 showed little or no toxicity (i.e., reduction in number of viable bacteria) compared to the controls at concentrations as high as 10% (0.1 g/g solution).

The study did not meet current guideline requirements for toxicity to microorganisms. It does, however, add weight of evidence for toxicity to microorganisms. Single species tests with Escherichia coli should be considered of low relevance for STPs. The tests cannot be used for determination of the PNECstp as they use glucose as a substrate (nor is E. coli a bacterium that will tend to multiply in an activated sludge environment). The information from such single-species screening tests may eventually be considered together with other existing data in a Weight of Evidence approach.

The lines of evidence discussed above are supported by the category hypothesis detailed in the Reconsile Siloxane Category report (PFA, 2017at), 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.

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

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

Test method

Duration (h)

Reliability

540-97-6

Dodecamethylcyclohexasiloxane

>100

 

OECD 209

ASRI

3

1

541-05-9

Hexamethylcyclotrisiloxane

>100

>100

OECD 209

ASRI

3

1

541-02-6

Decamethylcyclopentasiloxane

>2000

 

C11

ASRI

3

1

107-46-0

Hexamethyldisiloxane

>>100

≥100

OECD 209

ASRI

3

1

141-62-8

Decamethyltetrasiloxane

>100

 

OECD 209

ASRI

3

1

352230-22-9

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

>1000

≥1000

OECD 209

ASRI

3

1

2627-95-4

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

>1000

≥1000

OECD 209

ASRI

3

1

2554-06-5

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

>1000

≥1000

OECD 209

ASRI

3

1

N/A (EC 939-487-8)

Phenyl silsesquioxanes

>1000

≥1000

OECD 209

ASRI

3

1

99363-37-8

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

> water soluble fraction

≥ water soluble fraction

OECD 209

ASRI

3

1

71750-79-3

dimethyl, (aminoethylaminopropyl)methyl siloxane, trimethylsiloxy-terminated

> water soluble fraction

≥ water soluble fraction

OECD 209

ASRI

3

1

Categories Display