3-trimethoxysilylpropane-1-thiol

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)). The EC₅₀ and EC₁₀ are equivalent to 364 mg/l and 26 mg/l when expressed in terms of the silanol hydrolysis product.

Key value for chemical safety assessment

EC50 for microorganisms:

364 mg/L

EC10 or NOEC for microorganisms:

26 mg/L

Additional information

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 (Diefenbach 1995). The results may be expressed in terms of concentration of the hydrolysis product, 3-(trihydroxysilyl)propanethiol, by applying a molecular weight correction: (MW of silanol = 154.26 / MW of parent = 196.34) * EC₅₀ 463 and EC₁₀ 32.6 = EC₅₀ 364 mg/l and EC₁₀ 26 mg/l.

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