Dibenzylbenzene, ar-methyl derivative

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:

1995-02-06 to 1995-02-07

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study well documented, meets generally accepted scientific principles, acceptable for assessment

Guideline:

other: O2 consumption test (Huels method)

Principles of method if other than guideline:

The "Oxygen Consumption Test" offers the possibility of measuring chronic toxicity effects in bacteria with difficult substances e.g. those which are sparingly soluble, coloured, emulsifying or dispersive, even slightly volatile products can be tested.
Principle of the test: Glass vessels (e.g. 100 ml BOD-flasks) with known volume will be completely filled with culture solution, bacterial suspension and test substance in different concentrations (emulsified if insoluble in water), bubble-free sealed with glass stoppers and incubated for 5 to 6 hours at 25 ± 2°C on a shaking machine. Test vessels without bacterial suspension and vessels without test substance serve as controls. The differences between the oxygen content in the vessels at the beginning and the end of the incubation time is a measurement for the bacterial oxygen consumption.

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: 2.0 g of the test substance was weighed in 20 mL emulsifier and emulsified in a shaking incubator at 25 °C for 19 h at 200 rpm. 1 mL of this test solution was given into the test vessel (100 mL) for the highest test concentration (1000 mg/L). For further test concentrations the test solution was adequately diluted with emulsifying solution (dilution 1:10 each).
- Controls: yes
- Chemical name of vehicle (emulsifier): Nonylphenol, 10 EO, 5 PO
- Concentration of vehicle in test medium (stock solution and final test solution(s) including control(s)): 1 mL/100 mL
- Evidence of undissolved material (e.g. precipitate, surface film, etc): not mentioned

Test organisms (species):

Pseudomonas putida

Details on inoculum:

- Laboratory culture: yes
- Method of cultivation: not described
- Preparation of inoculum for exposure: approx. 19 h incubation of liquid culture of test organism
- Pretreatment: 200 mL stock solution I and II each were filled in an sterile 5 L-flask, containing 3520 mL deionized water and a magnetic stirrer bar, the solution were stirred for 30 min. and aerated. Thereafter 80 mL pre-culture were added and additionally 5 min stirred and areated.
- Initial biomass concentration: approx. 10 x 10E5 bacteria/mL, adjusted with sterile NaCl solution by photometrical measurement at 436 nm (extinction 0.301)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

4.92 h

Remarks on exposure duration:

the minor deviation of the incubation time (5 - 6 h) did not influence the O2 consumption (4.41 mg O2/L)

Post exposure observation period:

none

Hardness:

not mentioned

Test temperature:

Preculture: 24.7 .- 24.9 °C
Incubation: 24.7 - 25.3 °C

pH:

not mentioned

Dissolved oxygen:

not mentioned

Salinity:

see "Details on test conditions"

Nominal and measured concentrations:

1, 10, 100 and 1000 mg/L (nominal concentrations)

Details on test conditions:

INOCULUM/TEST ORGANISM
- Species/strain: Pseudomonas putida migula
- Source: Dr. Reinhard Kanne, Bayer AG, Leverkusen, Germany
- Method of cultivation: not described
- Preparation of inoculum: approx. 19 h incubation of liquid culture of test organism
- Pretreatment: 200 mL stock solution I and II each were filled in an sterile 5 L-flask, containing 3520 mL deionized water and a magnetic stirrer bar, the solution were stirred for 30 min. and aerated. Thereafter 80 mL pre-culture were added and additionally 5 min stirred and areated.
- Cell concentration of the inoculum: approx. 10 x 10E5 bacteria/mL, adjusted with sterile NaCl solution by photometrical measurement at 436 nm (extinction 0.301)
TEST SYSTEM
- Number of culture flasks:
a) 4 flasks per concentration with test substance, 2 of this flasks were used for determination of autooxidation of the test substance by adding of 1 mL HgCl2 solution, final concentration in the flasks approx. 3 mg/L
b) 4 flasks without test substance but with HgCl2 addition for determination of the oxygen content at the beginning of the test
c) 5 flasks without test substance, without HgCl2 for determination of the uninfluenced bacterial oxygen consumption. 1 flask of these was used to measure the oxygen contents after 4.5 h to determine the end of incubation. This value was not used for evaluation.
- Measuring equipment: oxygen electrode
- Termination of test: 1 mL HgCl2 solution (final concentration approx. 3 mg HgCl2/L) were added to each test vessel to stop the reaction.
TEST SUBSTANCE CONCENTRATIONS: 1, 10, 100 and 1000 mg/L
- Preparation of test substance solutions: 2.0 g of the test substance was weighed in 20 mL emulsifying solution (Nonylphenol, 10 EO, 5 PO) and emulsified in a shaking incubator at 25 °C for 19 h at 200 rpm. 1 mL of this test solution was given into the test vessel (100 mL) for the highest test concentration (1000 mg/L). For further test concentrations the test solution was adequately diluted with emulsifying solution (dilution 1:10 each).
DURATION OF THE TEST: 4.92 h
ANALYTICAL PARAMETER: O2 consumption
TEST CONDITIONS
- Composition of solutions:
a) Trace element solution (autoclaved), per 500 mL distilled water:
0.0275 g Al2(SO4)3 x n H2O
0.014 g KJ
0.014 g KBr
0.0275 g TiO2
0.014 g SnCl2 x 2 H2O
0.014 g LiCl
0.1945 g MnCl2 x 4 H2O
0.307 g H3BO3
0.0275 g ZnSO4 x 7 H2O
0.0275 g CuSO4 x 5 H2O
0.0295 g NiSO4 x 6 H2O
0.0275 g Co(NO3)2 x 6 H2O
b) Stock solution I (sterilized):
20 g D(+)Glucose
4.24 g Na NO3
2.40 g K2HPO4
1.20 g KH2PO4
30 mL Trace element solution (a)
1000 mL distilled water
c) Stock solution II (steril filtrated):
0.200 g FeSO3 x 7 H2O
3.71 g MgSO4 x 6 H2O
made up to 1 L with distilled water
d) NaCl solution (autoclaved):
0.500 g NaCl made up to 1 L distilled water

Reference substance (positive control):

no

Key result

Duration:

4.92 h

Dose descriptor:

EC10

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

The test substance did not affect the bacterial respiration in the tested concentration range:
EC10 > 1 g/L
EC50 > 1 g/L

- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: none
- Effect concentrations exceeding solubility of substance in test medium: none

Results with reference substance (positive control):

No reference substance tested

Reported statistics and error estimates:

No statistics performed

Validity criteria fulfilled:

yes

Conclusions:

The test substance did not affect the bacterial respiration in the tested concentration range:
EC10 > 1 g/L
EC50 > 1 g/L

Executive summary:

A test on bacterial toxicity on Pseudomonas putida was performed following a method developped by the laboratory. The exposure concentrations were 1, 10, 100 and 1000 mg/L (nominal concentrations). The exposure period was around 5h. The test substance did not affect the bacterial respiration in the tested concentration range. Therefore, the EC10 and EC50 are both above 1 g/L.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L

Additional information

In an oxygen consumption test using Pseudomonas putida, no significant effects to respiration were observed at concentrations greatly exceeding the level of water solubility. The calculated 4.92 h EC10 was >1000 mg/L.