3-(triethoxysilyl)propanethiol

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: EG-Nr. L 133/118 from 30.5.1988

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Direct addition

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Marl-Ost municipal sewage treatment plant.

- Preparation of inoculum for exposure: Centrifuged.

- Suspended solids: 3.6 g/l; (1.44 g/l when used in test).

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Post exposure observation period:

Oxygen consumption evaluated over a time period of at most 10 minutes.

Test temperature:

19.0 - 20.7°C

Nominal and measured concentrations:

Nominal:207.6 mg/l; 157.4 mg/l; 101 mg/l; 51.2 mg/l; 20 mg/l

Details on test conditions:

TEST SYSTEM
- Material, size, headspace, fill volume: 500 ml

- Type (delete if not applicable): closed

- Aeration: Yes

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

463 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Key result

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

32.6 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Results with reference substance (positive control):

EC50 6.9 mg/l

Table 1: Controls, reference substance (3, 5-dichlorophenol) and test substance: oxygen consumption and percentage inhibition of the respiration rate.

Flask	Nominal concentration (mg/l)	Oxygen consumption rate (mg O2/l/hour)	% Inhibition respiration rate
Inoculum control	-	23.93	-
Inoculum control	-	24.23	-
Test substance	207.6	14.84	38.4
Test substance	157.4	16.47	31.6
Test substance	101	19.73	18.1
Test substance	51.2	21.04	12.6
Test substance	20	22.50	6.6
Reference substance	5	13.92	42.4
Reference substance	7	11.94	50.4
Reference substance	10	9.98	58.6

 

Validity criteria fulfilled:

yes

Conclusions:

A 3-hour ASRI EC50 value of 463 mg/l and EC10 value of 32.6 mg/l were determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.

Description of key information

Toxicity to microorganisms: 3-hour ASRI EC₅₀ 463 mg/l and EC₁₀ 32.6 mg/l (EC guideline 118/133 (1988)) based on read-across from an analogous substance.

Key value for chemical safety assessment

EC50 for microorganisms:

463 mg/L

EC10 or NOEC for microorganisms:

32.6 mg/L

Additional information

There are no microorganism toxicity data available for 3-(triethoxysilyl)propanethiol, therefore good quality data for the structurally-related substance 3-(trimethoxysilyl)propane-1-thiol (CAS 4420-74-0), have been read across. Both substances undergo hydrolysis to form the same silanol hydrolysis product, 3-(trihydroxysilyl)propanethiol. The other hydrolysis products for both substances are ethanol and methanol respectively. Both substances are expected to undergo minimal hydrolysis in the time-frame of an ASRI test.

Ethanol and methanol do not have adverse effects on microorganisms (OECD 2004a and OECD 2004b).

3-(Triethoxysilyl)propanethiol and 3-(trimethoxysilyl)propane-1-thiol are within a wider group of substances within which in general, there is some evidence of toxicity to sewage microorganisms. This group consists of substances that are structurally similar substances and have thiol functionality in the hydrocarbon side-chain.

Table 7.4.2 presents microorganism toxicity data available for substances relevant to 3-(triethoxysilyl)propanethiol. It is considered valid to read-across the results for 3-(trimethoxysilyl)propane-1-thiol (CAS 4420-74-0) to fill the data gap for the registered substance since the source and target substances generate the same silanol hydrolysis product.

Additional information is given in a supporting report (PFA, 2013n) attached in IUCLID Section 13.

Table 7.4.2: Microorganism toxicity data for relevant substances

CAS	Name	Result: E(I)C50 (mg/l)	Result: NOEC (or EC10/ EC20) (mg/l)	Guideline Number	Test method	Species	Duration (hours)	Reliability
4420-74-0	3-(Trimethoxysilyl)propane-1-thiol	463	EC10 = 32.6	EG guideline 118/133 (1988)	ASRI		3	1

In the study with 3-(trimethoxysilyl)propane-1-thiol, a 3-hour ASRI EC₅₀ value of 463 mg/l and EC₁₀ value of 32.6 mg/l were determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.

Reference:

PFA (2013n). Peter Fisk Associates, Toxicity to sewage treatment plant microorganisms: III-20 analogue group, PFA.300.003.009