1,1,1,3,5,5,5-heptamethyl-3-[(trimethylsilyl)oxy]trisiloxane

Toxicity to microorganisms

Description of key information

Toxicity to microorganisms: 3hr EC50 >1000 mg/l; NOEC >=1000 mg/l (OECD 209), read-across from Silsesquioxanes, Phenyl (CAS 070131-69-0).

Additional information

There are no microorganism toxicity data available for M3T

A category approach is applied to this endpoint and is detailed in the Siloxane Category report (PFA, 2017a). 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 Silsesquioxanes, Phenyl (CAS 070131-69-0), have been read across to M3T.

M3T and Silsesquioxanes, Phenyl are members of the Reconsile Siloxanes Category within which, in general, the substances exhibit no evidence of significant toxicity to microorganisms.

Table 7.1.6 presents microorganism toxicity data available for substances within the Siloxanes Category.

Table7.1.6 Microorganism toxicity data available for substances within the Siloxanes Category

CAS	Name	Result: E(I)C50(mg/l)	Result: NOEC (or EC10/ EC20) (mg/l)	Guideline Number	Test method	Duration	Reliability
000540-97-6	Dodecamethylcyclohexasiloxane	>100 mg/l		OECD 209	ASRI	3hr	1a
000541-05-9	Hexamethylcyclotrisiloxane	>100 mg/l	>100 mg/l	OECD 209	ASRI	3hr	1a
000541-02-6	Decamethylcyclopentasiloxane	>2000 mg/l		C11	ASRI	3hr	1a
000107-46-0	Hexamethyldisiloxane	>>100	≥100	OECD 209	ASRI	3h	1a
000141-62-8	Decamethyltetrasiloxane	>100 mg/l		OECD 209	ASRI	3hr	1a
352230-22-9	Siloxanes and Silicones, di-Ph, Ph (trimethylsilyl)oxy	>1000 mg/l	≥1000 mg/l	OECD 209	ASRI	3hr	1a
002627-95-4	1,1,3,3-tetramethyl-1,3-divinyldisiloxane	>1000 mg/l	≥1000 mg/l	OECD 209	ASRI	3hr	1a
002554-06-5	2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane	>1000 mg/l	≥1000 mg/l	OECD 209	ASRI	3hr	1a
070131-69-0	Silsesquioxanes, Phenyl	>1000	≥1000	OECD 209	ASRI	3 h	1a
099363-37-8	dimethyl, methyl(3-aminopropyl) siloxane, trimethylsiloxy-terminated	> water soluble fraction	≥ water soluble fraction	OECD 209	ASRI	3hr	1a
071750-79-3	dimethyl, (aminoethylaminopropyl)methyl siloxane, trimethylsiloxy-terminated	> water soluble fraction	≥ water soluble fraction	OECD 209	ASRI	3hr	1a

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

Under the conditions of this present test Silsequioxanes, phenyl was not toxic to waste water (activated sludge) bacteria up to and including a loading rate of 1000 mg/l (NOEC).