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Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1994-04-19 to 1994-04-20
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The test procedure was described in sufficient detail and was in accordance with generally accepted scientific standards, with acceptable restrictions. The restrictions were that a reference substance was not used to check the sensitivity of the microorganisms. The study was conducted in compliance with GLP.
Principles of method if other than guideline:
Method: Oxygen consumption test (Huls method)
GLP compliance:
yes
Vehicle:
no
Details on test solutions:
Test substance was dissolved in water to give a stock solution of 50 mg/ml. This was pipetted in graded concentrations directly in the test flasks.
Test organisms (species):
Pseudomonas putida
Details on inoculum:
The bacterial culture was originally from the Institute for Water, Soil, and Air Hygiene of the BGA (Berlin).
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
5.75 h
Test temperature:
24.5-26.1 °C
Nominal and measured concentrations:
12.5, 25, 37.5 and 50 mg/l
Details on test conditions:
TEST SYSTEM
- Test vessel: 100 ml BOD bottles

- Type (delete if not applicable): closed

- No. of vessels per concentration (replicates): 4 with test substance (2 sterilised with HgCl2).

- No. of vessels per control (replicates): 4 without test substance and sterilised with HgCl2. 5 flasks without test substance or HgCl2.

- Biomass loading rate: 10 E+05 bacteria count/ml

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Oxygen concentration measured at end of test.

TEST CONCENTRATIONS
- Range finding study was used to determine the concentrations used in the main study
Reference substance (positive control):
no
Key result
Duration:
5.75 h
Dose descriptor:
EC10
Effect conc.:
13 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Key result
Duration:
5.75 h
Dose descriptor:
EC50
Effect conc.:
43 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):
A positive control was not included.
Reported statistics and error estimates:
Regression analysis performed on results

Table 1Effect of test substance on oxygen consumption

 

Conditions

Concentration of test substance (mg/ml)

0

12.5

25

37.5

50

Test substance with HgCl2

Initial value*

8.24

8.28

8.22

8.14

8.17

Difference**

 

-0.04

0.02

0.11

0.08

Test substance without HgCl2

Final value*

4.25

4.60

5.52

6.01

6.30

Oxygen consumption after incubation

 

3.99

3.69

2.7

2.15

1.86

Absolute difference after incubation

 

 

0.30

 

1.29

1.84

2.31

% effect

 

 

7.6

32.3

46.1

53.5

* Average of 2 (or four for control) cultures

** Difference between control and test values

Linear regression after Probit transformation

Measure value mg/ml

% effect

log 10

Probit

Expected Probit

12.5

7.6

1.0969

3.6245

3.7

25

32.3

1.3979

4.5442

4.4

37.5

46.1

1.6740

4.9024

4.9

50

53.5

1.6990

5.0876

5.2

 

Regression analysis: Log Concentration = a; Probit = y; y=a+bx

a = 0.98

b= 2.47

n= 4

r =0.9898

Conclusions:
A pseudomonas putida respiration inhibition 5.75 hour EC50 of 43 mg/l and EC10 of 13 mg/l were determined in a reliable study described in sufficient detail and conducted in accordance with generally accepted scientific standards, with acceptable restrictions. The restrictions were that a reference substance was not used to check the sensitivity of the microorganisms. The study was conducted in compliance with GLP.

Description of key information

Toxicity to microorganisms: 5.75 hour EC10 13 mg/L (respiration inhibition test) read-across from an analogous substance

Key value for chemical safety assessment

EC50 for microorganisms:
43 mg/L
EC10 or NOEC for microorganisms:
13 mg/L

Additional information

No reliable study of respiration inhibition of activated sludge is available for the submission substance, 3-(trimethoxysilyl)propylamine (CAS No. 13822-56-5), therefore good quality data for an analogous substance, (3-aminopropyl)triethoxysilane (CAS No. 919-30-2) have been read-across. Both substances hydrolyse rapidly and share the same silanol hydrolysis product, 3-aminopropylsilanetriol. The other hydrolysis products are methanol and ethanol respectively.

 

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

 

In a respiration inhibition test in a single bacteria strain (Pseudomonas putida) study conducted on (3-aminopropyl)triethoxysilane, 5.75 h EC50 of 43 mg/L and EC10 of 13 mg/L were determined. The study was considered to be 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 triethoxy(3-isocyanatopropyl)silane (CAS No. 24801-88-5), an activated sludge respiration inhibition 3 h NOEC value of 10 mg/L was reported in accordance with OECD 209.

 

3-(Trimethoxysilyl)propylamine (CAS No. 13822-56-5) and (3-aminopropyl)triethoxysilane (CAS No. 919-30-2) are within an analogue group of substances within which in general, there is some evidence of toxicity to microorganisms i.e. an effect concentration (EC) could be derived and was <1000 mg/L.

 

The table below presents microorganism toxicity data available for substances within the analogue group III-8 of chlorosilanes, siloxanes, silanes and alkoxysilanes etc. with amino group(s) in side chain after any very rapid hydrolysis has been accounted for. 3-(Trimethoxysilyl)propylamine (CAS No. 13822-56-5) and 3-aminopropyltriethoxysilane (CAS No. 919-30-2) are members of this analogue group.

It is therefore considered valid to read-across the results for (3-aminopropyl)triethoxysilane (CAS No. 919-30-2) to fill the data gap for the registered substance. Additional information is given in a supporting report (PFA 2013l) attached in Section 13.

Table: Microorganism toxicity data available for substances within the relevant analogue group III-8 of chemicals

CAS

Chemical Name (CAS Name)

Guideline Number

Test method

Species

Duration

Result: E(I)C50 (mg/l)

Result: NOEC (Or EC10/EC20) (mg/l)

Klimisch code

27445-54-1

Cyclohexanamine,N-[(diethoxymethylsilyl)methyl]-

OECD 209

ASRI

 

3hr - but stirred 24hr

624.2 mg/l    (EC20 240.2 mg/l)

 

1

3068-78-8

N-[3-(trimethoxysilyl)propylcyclohexylamine]

OECD 209

ASRI

 

3 h

>1000

EC20 = 203 mg/l

1

157923-74-5

2,2-dimethyl-4-(trimethoxysilyl)butylamine

OECD 209

ASRI

 

3 h

>1000

EC15 869. 17.5% inhibition at 1000 mg/l.

1

227085-51-0

N-ethyl-3-trimethoxysilyl-2-methylpropanamine

OECD 209

ASRI

 

3 h

>1000

1

919-30-2

3-aminopropyltriethoxysilane

Huls AG method

oxygen consumption

P. putida

5.75 h

43 mg/l

EC10 13 mg/l

2

82985-35-1

Bis(trimethoxysilylpropyl)amine

OECD 209

ASRI

 

3 h

estimated value, approximately 1000

220

Nitrification control indicated that heterotrophic inhibition of respiration rate was lower than the total inhibition.

1

1760-24-3

N-(3-(trimethoxysilyl)propyl)ethylenediamine

DIN 38 412, Part 8 (Pseudomonas cell multiplication inhibition test)

growth inhibition test

P. putida

16 h

67 mg/l

EC10 25 mg/l

1

[N,N-Bis(trimethylsilyl)aminopropyl]methyldiethoxysilane

OECD 209

ASRI

3 h

>100

1

None19

reaction mix (reaction mass of 6 benzylated amine silanes)

OECD 209; EC C.11

ASRI

3 h

569

130; EC20 172

1

An IC50 value of 3400 mg/L for 3-(trimethoxysilyl)propylamine (CAS No. 13822 -56 -5) 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.

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.

PFA (2013l). Peter Fisk Associates, STP Microorganism toxicity III-8 Analogue Group report, PFA.300.003.008