Trichloro(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)silane

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1997-04-24

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Test type:

static

Water media type:

freshwater

Total exposure duration:

3 h

Test temperature:

18-22°C were hold by cooling the water in the incubation vessel with ice.

At the beginning of incubation: 18-19°C

During the determination of oxygen content: 18.8-19.9°C

Dissolved oxygen:

Control 1: 38.93 mg O2/l*h
Control 2: 39.20 mg O2/l*h

The difference between control 1 and 2 does not exceed 15% (i.e. 0.7%)

Reference substance (positive control):

yes

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 300 mg/L

Details on results:

In the tested concentration range of 67, 133, 267, 534, and 1334 mg/l there was no inhibitory dose-effect-level

Results with reference substance (positive control):

A positive control test with 3, 5-dichlorophenol yielded an EC50 of 7.3 mg/l, which is within the accepted range of 5 to 30 mg/l required by the guideline for a valid study.

Validity criteria fulfilled:

yes

Conclusions:

An activated sludge respiration inhibition 3hr EC50 value of >1300 mg/l was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP. This indicates that the test substance was not toxic to waste water (activated sludge) bacteria at a nominal concentration of 1300 mg/l.

Reference 2

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1999

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Qualifier:

according to guideline

Guideline:

other: ISO 10712. Water quality- Pseudomonas putida growth in hibition test (Pseudomonas cell multiplication inhibition test)

Deviations:

yes

Remarks:

Test was carried out with and without pH adjustment of the test media as the test substance releases hydrochloric acid in contact with water, resulting in strongly acidic test substance media

Principles of method if other than guideline:

The growth of the bacterium was determined after 17hours by measuring the increase in optical density of the culture at the wavelength 605 nm. A range finding test was conducted initially and indicated that no pH related effects after pH adjustment at the maximum concentration of 101 mg/l, a limit test was carried out

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

yes

Test organisms (species):

Pseudomonas putida

Details on inoculum:

Gram negative bacterium Pseudomonas putida. Bacterium cultivated according to the standard method described in ISO guideline 10712. Stock culture was maintained on solid agar medium and pre-culture was prepared by suspending bacteria from a 6 day old stock culture in sterile pre-culture medium. The suspension was diluted to an absorbance of approx. 0.02

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

17 h

Post exposure observation period:

After 17 hours incubation one sample was taken from each test vessel and the absorbance at 605nm was determined.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol. Purity 97 %

Key result

Duration:

17 h

Dose descriptor:

EC10

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth inhibition

Key result

Duration:

17 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth inhibition

Details on results:

The absorbance of each culture was corrected for the absorbance of the controls without bacteria. The mean value of the absorbance of two cultures at each concentration and % cell multiplication inhibition calculated. Based on the limit test, no effect on Pseudomonas putida growth was observed. The EC10 and EC50 are therefore assessed to be >100 mg/L.

Results with reference substance (positive control):

The EC50 of the reference substance was 22.5 mg/L (± 95% C.I = 13.9 – 36.5 mg/L)

Validity criteria fulfilled:

yes

Conclusions:

Based on the limit test, no effect was observed on the growth of Pseudomonas putida at the test concentration. EC10 and EC50 after 17 hours were assessed to be >100 mg/L

Description of key information

Toxicity to microorganisms, limit test: EC₁₀ and EC₅₀ values were both assessed to be >100 mg/l (worst-case value)

Additional information

There are no reliable microorganism toxicity data available for [2-(perfluorohexyl)ethyl]trichlorosilane (CAS 78560-45-9, EC 278-947-6), therefore good quality data for the analogous substances, [2-(Perfluorohexyl)ethyl]triethoxysilane (CAS 51851-37-7, EC 257-473-3) and dichloromethyl(3,3,3-trifluoropropyl)silane (CAS 675-62-7, EC 211-623-4), have been read across. The submission substance, [2-(perfluorohexyl)ethyl]trichlorosilane, hydrolyses very rapidly in contact with water to form [2-(perfluorohexyl)ethyl]silanetriol and hydrochloric acid. The read-across substance, dichloromethyl(3,3,3-trifluoropropyl)silane also hydrolyses very rapidly in contact with water to form methyl(3,3,3-trifluoropropyl)silanediol and hydrochloric acid. [2-(Perfluorohexyl)ethyl]triethoxysilane also undergoes hydrolysis to form [2-(perfluorohexyl)ethyl]silanetriol and methanol. In view of the instability of the substances in water, it is the silanol hydrolysis product that is relevant for environmental risk assessment.

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

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

[2-(Perfluorohexyl)ethyl]trichlorosilane (CAS No. 78560-45-9), [2-(Perfluorohexyl)ethyl]triethoxysilane (CAS No. 51851-37-7) and dichloromethyl(3,3,3-trifluoropropyl)silane (CAS No. 675-62-7) are within an analogue group of substances within which, in general, there is no evidence of significant toxicity to microorganisms.

It is therefore considered valid to read-across the results for [2-(Perfluorohexyl)ethyl]triethoxysilane (CAS No. 51851-37-7) and dichloromethyl(3,3,3-trifluoropropyl)silane (CAS No. 675-62-7) to fill the data gap for the registered substance. Additional information is given in a supporting report (PFA, 2013j) attached in Section 13.

Table: Microorganism toxicity data for relevant substances

CAS No	Name	Result: E(I) C50 (mg/l)	Result: NOEC (or EC10/ EC20) (mg/l)	Guideline	Test method	Species	Duration (h)	Klimisch code
675-62-7	Dichloromethyl(3,3,3-trifluoropropyl)silane	>100		DIN 38 412, Part 8 (Pseudomonas cell multiplication inhibition test)	growth inhibition test	P. putida	17	1
2374-14-3	2,4,6-trimethyl-2,4,6-tris(3,3,3-trifluoropropyl)cyclotrisiloxane	>1000	≥1000 mg/l Nitrification control indicated no heterotrophic inhibition of respiration rate	OECD 209	ASRI		3	1
51851-37-7	Triethoxy(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)silane	>1300		EU Standard 88/302	ASRI		3	1

 

In the study with [2-(Perfluorohexyl)ethyl]triethoxysilane (CAS 51851-37-7), an activated sludge respiration inhibition 3h EC₅₀ value of >1300 mg/l was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP. This indicates that the test substance was not toxic to waste water (activated sludge) bacteria at a nominal concentration of 1300 mg/l. Similarly, for dichloromethyl(3,3,3-trifluoropropyl)silane (CAS 675-62-7, EC ), there was no observed effect of growth of Pseudomonas putida at the test concentration after 17 hours, and so the EC₁₀ and EC₅₀ values were assessed to be >100 mg/l. The study was conducted to standard guideline (ISO 10712) and in compliance with GLP (Hanstvelt, 1999).

The results are used as weight of evidence that [2-(perfluorohexyl)ethyl]trichlorosilane is not expected to be toxic to microorganisms at >100 mg/l. Therefore, the EC₁₀ and EC₅₀ value of >100 mg/l was used as a worst-case approach.

References:

OECD (2004a): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 19-22 October 2004, Ethanol, CAS 64-17-5.

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