Octanethioic acid, S-[3-(triethoxysilyl)propyl] ester, reaction products with 2-methyl-1,3-propanediol and 3-(triethoxysilyl)-1-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

Study period:

20 Mar 2007 (Initiation Date) - 10 Jul 2007 (Study Completion Date)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: Commission Directive 88/302/EEC: "Activated Sludge Respiration Inhibition Test" (1988).

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Version / remarks:

adopted April 04, 1984

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Vehicle:

not specified

Test organisms (species):

activated sludge

Details on inoculum:

Activated sludge supplied by sewage plant Darmstadt, Germany

Test type:

other: aerobic

Total exposure duration:

3 h

Test temperature:

20-23°C (room temperature)
19-21°C (temperature in test vessels)

pH:

pH: 7.9 (activated sludge)

Nominal and measured concentrations:

nominal test concentrations: 10, 32, 100, 320 and 1000 mg/L (test item)
nominal test concentrations: 3.2, 10 and 32 mg/L (positive control)

Reference substance (positive control):

yes

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/L

Details on results:

In comparison to the inoculum controls the respiration rate of the activated sludge was slightly inhibited in the range of -11.4% to 8.9% at the tested concentrations of nominal 10, 32, 100, 320 and 1000mg/L.
Based on measured inhibition rates, the 3-hour EC20 and EC50 could not be quantified because up to the highest nominal test concentration of 1000 mg/L less than 20% inhibition was noted after three hours incubation. No dose response could be observed. The maximum deviation in respiration rates was -11% at test item concentration of 1000 mg/L. The 3-hour EC20 and EC50 are clearly higher than 1000 mg/L under the present test conditions.

Results with reference substance (positive control):

The nominal concentrations of the positive control (3.2, 10 and 32 mg/L) were tested on the same activated sludge and under identical conditions as the test item. In comparison to the controls the respiration rate of the activated sludge was moderately inhibited by 31.6 % at the lowest nominal concentration of 3.2 mg/L. At the nominal concentration of 10 and 32 mg/L, the respiration rate was inhibited by 62.0 and 84.8%.
The 3-hour EC50 of the positive control was calculated to be 6.5 mg/L. Based on the measured data, the 95% confidence limits were 4.2 mg/L to 9.3 mg/L.

Validity criteria fulfilled:

yes

Conclusions:

The 3-hour EC20 and EC50 are clearly higher than 1000 mg/L under the test conditions. Even though the test was not designed for a NOEC determination, the NOEC of the test item can be established at 1000 mg/L.

Toxicity of 3,5-Dichlorophenol:
The 3-hour EC50 for the positive control 3,5-Dichlorophenol, which was tested in the same way as the test item, was found to be 6.5 mg/L and is within the range of 5-30 mg/L recommended by the test guidelines.

Description of key information

Although the available test was not designed for a NOEC determination, the data indicate that the NOEC of the test item is 1000 mg/L.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L