Registration Dossier

Diss Factsheets

Ecotoxicological information

Toxicity to microorganisms

Currently viewing:

Administrative data

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:
09 February 2012 - 09 February 2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
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 Amino Functional Alkoxysilanes (tested as received), a clear light yellow liquid, was a mixture including reactants and species consistent with the various reaction products obtained by combining aminopropyltriethoxysilane, glycidoxypropyl-trimethoxysilane and methyltrimethoxysilane (information obtained by the sponsor). Since Amino Functional Alkoxysilanes may have the potential to be volatile (information obtained by the sponsor), the test substance was pipetted below the surface of Milli-RO-water (200 ml, tap water purified by reverse osmosis) and stirred briefly to mix (5 minutes) in closed dark brown bottles. The initial loading rates were 2.5 times the final loading rate. Subsequently, 16 ml synthetic medium, 250 ml sludge and Milli-RO water up to 500 ml were added resulting in the required loading rates. Optimal contact between the test substance and test organisms was ensured applying continuous aeration and stirring.
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 7.4 on the day of testing. The batch of sludge was used one day after collection; therefore 50 ml of synthetic medium 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:
yes
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.
Test temperature:
Between 18.1 and 20.3°C
pH:
Before addition of sludge: 7.6 - 8.5.
After the 3 hour exposure period: 7.7 - 8.3.

Dissolved oxygen:
The oxygen concentration at the start of measurements was at least 7.5 mg O2/l

Oxygen consumption:
Controls: 48 mg O2/l h (mean value)
Amino Functional Alkoxysilanes 10 mg/l: 53 mg O2/l h
Amino Functional Alkoxysilanes 100 mg/l: 45 mg O2/l h
Amino Functional Alkoxysilanes 1000 mg/l: 51 mg O2/l h (mean value)
Nominal and measured concentrations:
Nominal loading rates: 10, 100 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): 1 for 10 and 100 mg/l and 3 for 1000 mg/l

- No. of vessels per control (replicates): 2

- 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/l/hr, was calculated from the linear part of the respiration curve, which was generally between 2 and 7 mg O2/l.

TEST CONCENTRATIONS

- Test concentrations: limit study at 10, 100 and 1000 mg/l
Key result
Duration:
3 h
Dose descriptor:
NOEC
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
Key result
Duration:
3 h
Dose descriptor:
EC50
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:
In the combined limit/range-finding test no inhibition of the respiration rate of the sludge was recorded at a loading rate of 1000 mg Amino Functional Alkoxysilanes per litre.

There was no significant oxygen uptake from abiotic processes and the results at 1000 mg/l with a nitrification inhibitor showed no heterotrophic inhibition of the respiration rate.
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 (4.0 mg/l).
Reported statistics and error estimates:
ECx
For the reference substance the percentage inhibition was plotted against the logarithm of the concentrations and the EC50 was determined using linear regression analysis.

For Amino Functional Alkoxysilanes no EC50 could be calculated because the test substance proved to be non-toxic (EC50 > a loading rate of 1000 mg/l).

NOEC estimation
No statistical analysis of the data was performed as no inhibition of the respiration rate of the sludge was recorded at a loading rate of 1000 mg Amino Functional Alkoxysilanes per litre.
Validity criteria fulfilled:
yes
Conclusions:
Under the conditions of this present test Amino Functional Alkoxysilanes was not toxic to waste water (activated sludge) bacteria up to and including a loading rate of 1000 mg/l (NOEC).

The EC50 exceeded a loading rate of 1000 mg/l.

Description of key information

Toxicity to microorganisms (whole substance): 3 hour ASRI EC50 >1000 mg/L; NOEC ≥1000 mg/L (OECD 209)

Constituents A: ASRI 3 hr EC10>100 mg/L (loading rate) (OECD 209)

Constituents B and C: 3 hour NOEC 220 mg/L (OECD 209, activated sludge respiration inhibition) read-across from an analogous substance

Constituents D: 5.75 hour EC10 13 mg/L (respiration inhibition test)

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
1 000 mg/L

Additional information

Under the conditions of this present test, Amino Functional Alkoxysilanes was not toxic to wastewater (activated sludge) bacteria up to and including a loading rate of 1000 mg/L (NOEC).

The EC50 exceeded a loading rate of 1000 mg/L.

The constituents of amino functional alkoxysilanes are expected to hydrolyse to some extent within the timescale of the test to silanol hydrolysis products and methanol and ethanol.

The submission substance is a complex multi-constituent substance containing four constituent groups. Therefore, in addition to the data on the whole substance, available data on the constituents and/or analogue substance(s) are also reported.

For Constituents A, an activated sludge respiration inhibition 3 hour EC10value of >100 mg/L (loading rate) was determined for trimethoxy(methyl)silane (CAS 1185-55-3) in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP. In a secondary source to which reliability could not be assigned, an IC50value of >10000 mg/L was reported for trimethoxy(methyl)silane.

For Constituents D, a respiration inhibition test in a single bacterial strain is available for 3-aminopropyl(triethoxy)silane (CAS 919-30-2). In this study, a Pseudomonas putida respiration inhibition 5.75 hour EC50 of 43 mg/L and EC10 of 13 mg/L were determined this constituent. The study was reliable and conducted in accordance with generally accepted scientific standards and described in sufficient detail and in compliance with GLP with acceptable restrictions. The restrictions were that a reference substance was not used to check the sensitivity of the microorganisms.

To support this result for CAS 919-30-2, a second study with an analogous substance, triethoxy(3-isocyanatopropyl)silane (CAS 24801-88-5), is read across. Both substances hydrolyse rapidly and share the same silanol hydrolysis product, (3-aminopropyl)silanetriol. The isocyanate in the read-across substance, triethoxy(3-isocyanatatopropyl)silane will undergoes vey rapid hydrolysis (half-life of about 5 minutes) to form 3-aminopropyl(triethoxy)silane, CAS 919-30-2 and carbon dioxide. 3-Aminopropyl(triethoxy)silane then undergoes rapid hydrolysis to form (3-aminopropyl)silanetriol and ethanol. This study reports anactivated sludge respiration inhibition 3 hour NOEC value of 10 mg/L and EC10 of 17 mg/L. An IC50 >5000 mg/L was reported in secondary literature (handbook). The original reference was not available for review and no further information is available. The reliability of this result is not assignable.

There are no reliable study of respiration inhibition of activated sludge for the Constituents B and C of the submission substance. Therefore, good quality data for the constituents have been read-across from a structural analogous substance. 

Data from bis(trimethoxysilylpropyl)amine (CAS 82985-35-1) is read-across to Constituents B and Constituents C.

The influence of bis(trimethoxysilylpropyl)amine (CAS 82985-35-1) on the respiration rate of activated sludge was investigated according to OECD 209 and GLP (NOTOX B.V., 2012). The nominal test concentrations were 10, 22, 46, 100, 200, 460 and 1000 mg/L. No inhibition in respiration rate of the sludge was recorded up to 220 mg/L. Hence, the NOEC for bis(trimethoxysilylpropyl)amine (CAS 82985-35-1) is 220 mg/l. The EC50 is 1000 mg/L. This results are read-across to Constituents 2 and 3 of the submission substance.

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

Carbon dioxide which is the by-product of the isocyanate hydrolysis, is exempt from registration under REACH Article 2(7) (a) because it is a substance with sufficiently known information and it is considered to cause minimum risk due to its intrinsic properties. Carbon dioxide is therefore not assessed further.

References:

OECD (2004a): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 18-20 October 2004, Methanol, CAS 67-56-1.

OECD (2004b): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 19-22 October 2004, Ethanol, CAS 64-17-5.

Categories Display