Tetramethylsilane

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

Study period:

1998-07-07 to 1998-07-08

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods

Qualifier:

according to guideline

Guideline:

DIN 38412-8 (Pseudomonas Zellvermehrungshemmtest)

Principles of method if other than guideline:

Modified for the testing of tetramethylsilane

GLP compliance:

yes

Test organisms (species):

Pseudomonas putida

Details on inoculum:

DSM number 50026 from the German Collection of Microorganisms

Total exposure duration:

17 h

Post exposure observation period:

Growth inhibition measured via photometric analysis of the turbidity. Wavelength 436 nm. The % inhibition was calculated via Excel programs MIGULA and evaluate.msk.

Test temperature:

Incubation of test solutions: 21.5-21.7°C

Details on test conditions:

For this test substance the investigational procedure was modified (teflon coated vessels, with gas-tight aluminium caps, of total volume approx. 120 ml).
Vessels were autoclaved at 120°C for 30 minutes, and pre-ventilated.

Key result

Duration:

17 h

Dose descriptor:

EC10

Effect conc.:

17.1 other: mg/1000mg

Conc. based on:

test mat.

Remarks:

measured by GC headspace analysis

Basis for effect:

growth inhibition

Remarks on result:

other: calculated with linear regression analysis

Key result

Duration:

17 h

Dose descriptor:

EC50

Effect conc.:

3 342 other: mg/1000mg

Conc. based on:

test mat.

Remarks:

measured by GC headspace analysis

Basis for effect:

growth inhibition

Remarks on result:

other: EC50 not achieved in the test but was calculated

Amount test substance added (µL)	Measured concentration mg/1000 mg	% inhibition
100	3.5	4.3
200	8.0	6.1
300	17.5	7.8
400	72.0	15.9
500	80.0	20.5
600	-	43.7

Validity criteria fulfilled:

yes

Conclusions:

A 17 hour growth inhibition EC10 of 17.1 g/L and EC50 of 3342 g/L for toxicity to Pseudomonas putida were determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP. The test method was modified to take into account the volatility of the substance (teflon-coated vessels, with gas-tight aluminum caps, of total volume approx. 120 mL were used). Concentrations were measured based on headspace GC analysis. Due to the volatility of the substance, it is likely that the dissolved concentrations were much less. The substance did show some toxicity to microorganisms under the closed conditions of the test; however, it is considered unlikely that sufficient concentrations for toxicity would be reached in a standard sewage treatment plant.

Description of key information

Toxicity to microorganisms: 17-hour EC₁₀ 17.1 g/L (DIN 38412-8, Pseudomonas putida).

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

17.1 g/L

Additional information

A 17-hour growth inhibition study with Pseudomonas putida gave an EC₁₀ of 17.1 g/l and an EC₅₀ of 3342 g/l (Diefenbach, 1998). The study was conducted in accordance with test method DIN 38412, Pseudomonas putida, and in compliance with GLP. The test method was modified to take into account the volatility of the substance (teflon-coated vessels, with gas-tight aluminium caps, of total volume approx. 120 ml were used). Concentrations were measured based on headspace GC analysis. Due to the volatility of the substance, it is likely that the dissolved concentrations were much less. It is likely that the limit of solubility would have been reached. The substance did show some toxicity to microorganisms at very high concentrations under the closed conditions of the test; however, it is considered unlikely that sufficient concentrations for toxicity would be reached in a standard sewage treatment plant.