Bis(triethoxysilylpropyl)amine

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:

key study

Study period:

08 - 22 Dec 2011

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

The batch of Bis(trimethoxysilylpropyl)amine tested was a clear colourless liquid with a purity of 96.9%.
The test substance was pipetted below the surface of the Milli-RO-water and stirred briefly to mix (5 minutes). Subsequently, synthetic sewage feed and sludge were added and the test was initiated applying a 3 hour contact time. Preferably, the solution of the test substance in water should be pH neutral. As discussed with the sponsor the pH of a test substance solution test was not adjusted to pH 7.5 ± 0.5.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

The sludge was coarsely sieved, washed and diluted with ISO-medium. A small amount of the sludge was weighed and dried overnight at ca. 105°C to determine the amount of suspended solids (3.0 g/l of sludge, as used for the test). The pH was 7.7 on the day of testing. The batch of sludge was used one day after collection; therefore 50 ml of synthetic sewage feed was added per litre of activated sludge at the end of the collection day. The sludge was kept aerated at test temperature until use.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Post exposure observation period:

After the 3-hour contact time, the oxygen consumption was recorded for a period of approximately 10 minutes. During measurement, the sample was not aerated but continuously stirred on a magnetic stirrer.
The pH and temperature were determined in the remaining part of the reaction mixture. This procedure was repeated for all test/reference substance concentrations/loading rates and controls.

Test temperature:

Final test: between 18.1 and 22.3 °C

pH:

Final test
Controls, before addition of sludge: between the pH was between 7.4 and 7.6.
Controls, after the 3 hour exposure periode the pH was between 7.9 and 8.2.

Test concentrations, before addition of sludge: between the pH was between 7.7 and 9.1.
Test concentrations, after the 3 hour exposure periode the pH was between 7.9 and 8.4.

Discussion:
Bis(trimethoxysilylpropyl)amine has a slight increasing effect on pH (up to 9.1).
In general, lower (<5) and higher pH values (> approx. 8.5) might increase the toxic effect on micro-organisms. Thus the inhibition of the respiration rate may be caused by the intrinsic toxicity of Bis(trimethoxysilylpropyl)amine and/or the effect of the pH.
Thus, testing as is described in this report includes both effects and is thus a worse case situation.

Dissolved oxygen:

The oxygen concentration at the start of measurement was at least 8.2 mg O2/L.

Oxygen consumption=Respiration rate (mg O2/L h):
Controls: 50 mg O2/L h
Bis(trimethoxysilylpropyl)amine at 10 mg/L: 54 mg O2/L h
Bis(trimethoxysilylpropyl)amine at 22 mg/L: 52 mg O2/L h
Bis(trimethoxysilylpropyl)amine at 46 mg/L: 56 mg O2/L h
Bis(trimethoxysilylpropyl)amine at 100 mg/L: 54 mg O2/L h
Bis(trimethoxysilylpropyl)amine at 220 mg/L: 45 mg O2/L h
Bis(trimethoxysilylpropyl)amine at 460 mgLl: 36 mg O2/L h
Bis(trimethoxysilylpropyl)amine at 1000 mg/L: 27 mg O2/L h

Nominal and measured concentrations:

Nominal loading rates: 10, 22, 46, 100, 200, 460 and 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: All glass
- Aeration:During exposure with clean, oil-free air
- No. of vessels per concentration (replicates):5
- No. of vessels per control (replicates): 6
- Biomass loading rate 1.5 g/l suspended solids in final test mixture

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Tap-water purified by reverse osmosis (Milli-RO)

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : The respiration rate from each vessel, in mg O2/lLh, was calculated from the linear part of the respiration curve, which was generally between 2 and 7 mg O2/L.

TEST CONCENTRATIONS
- Test concentrations: Seven loading rates: 10, 22, 46, 100, 200, 460 and 1000 mg/L

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

220 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

loading rate

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

270 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

loading rate

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

ca. 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

loading rate

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: estimated value

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

420 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

loading rate

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

other: EC80

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

loading rate

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

No statistically significant inhibition of the respiration rate of the sludge was recorded at or below a loading rate of 220 mg Bis(trimethoxysilylpropyl)amine / L (Bonferroni t-Test: α=0.05 Toxstat). At higher loading rates the inhibitory effect of Bis(trimethoxysilylpropyl)amine on aerobic waste water (activated sludge) bacteria increased with increasing loading rate, ranging from 27% inhibition at a loading rate of 460 mg/l to 46% at a loading rate of 1000 mg/L.

Results with reference substance (positive control):

The EC50 of 3,5-dichlorophenol was in the accepted range of 2 to 25 mg/L for total respiration (8.2 in the combined limit-range-finding test and 8.1 mg/L in the final test).

Reported statistics and error estimates:

ECx
For Bis(trimethoxysilylpropyl)amine the percentage inhibition was plotted against the logarithm of the loading rates. The EC10 and EC20, for the test substance, were determined using linear regression analysis. If available, the 95% confidence limits of the EC values were given. The EC50 and EC80, were estimated.

For the reference substance the percentage inhibition was plotted against the logarithm of the concentrations and the EC50 was determined using linear regression analysis.

NOEC estimation
The NOEC was based on statistical analysis of the data. Data obtained for the test concentrations were compared with those obtained for the control using TOXSTAT Release 3.5, 1996, D.D. Gulley, A.M. Boelter, H.L. Bergman.

Validity criteria fulfilled:

yes

Conclusions:

Bis(trimethoxysilylpropyl)amine was not toxic to waste water (activated sludge) bacteria at or below a loading rate of 220 mg/L (NOEC), according to the OECD guideline 209.

Reference 2

Endpoint:

activated sludge respiration inhibition testing

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Please refer to the attached justification below and the overall justification for grouping of substances attached in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across source

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

220 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

loading rate

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

270 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

loading rate

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

420 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

loading rate

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

ca. 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

loading rate

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: estimated value

Duration:

3 h

Dose descriptor:

other: EC80

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

loading rate

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Description of key information

NOEC (3 h) = 220 mg/L ((OECD 209) based on read across from CAS No. 82985-35-1)

EC50 (3 h) = 1000 mg/L ((OECD 209) based on read across from CAS No. 82985-35 -1)

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

EC10 or NOEC for microorganisms:

220 mg/L

Additional information

No experimental data on the toxicity of 3-(triethoxysilyl)-N-[3-(triethoxysilyl)propyl]-1-propanamine (CAS No. 13497-18-2) towards sewage sludge microorganisms are available. Therefore, good quality data from the analogous substance, 3-(trimethoxysilyl)-N-[3-(trimethoxysilyl)propyl]-1-propanamine (CAS No. 82985-35-1), have been read across. Both substances share the same hydrolysis product,  3-(trihydroxysilyl)-N-[3-(hydroxysilyl)propyl]-1-propanamine. Details on read across justifications can be found in the attached justification in IUCLID Section 13.

 

The influence of the test item 3-(trimethoxysilyl)-N-[3-(trimethoxysilyl)propyl]-1-propanamine (CAS 82985-35-1) on the respiration rate of activated sludge was investigated according to the OECD guideline 209 and GLP standards (2011). The nominal test concentrations used amounted 10, 22, 46, 100, 200, 460 and 1000 mg/L. The study resulted into an NOEC (3 h) of 220 mg/L and an EC50 (3 h) of 1000 mg/L (both nominal).

 

Based on the results of the read across substance, no toxicity of 3-(triethoxysilyl)-N-[3-(triethoxysilyl)propyl]-1-propanamine (CAS No. 13497-18-2) on activated sludge microorganisms is anticipated for concentrations relevant for the sewage treatment plant.