2,2'-azobis[4-methoxy-2,4-dimethylvaleronitrile]

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

06.03.-09.03.18

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

yes

Remarks:

, but uncritical

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Vehicle:

no

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Common name: Desmodesmus subspicatus
- Strain: 86.81
- Source (laboratory, culture collection): MBM Sciencebridge GmbH (Institut für Pflanzenphysiologie of Universität Göttingen) (2016)
- Age of inoculum (at test initiation):
- Method of cultivation:

ACCLIMATION
- Acclimation period:
- Culturing media and conditions (same as test or not):
- Any deformed or abnormal cells observed:

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

20.8 – 24.0 °C

pH:

7.3 - 7.9

Nominal and measured concentrations:

nominal: 1.0 / 3.2 / 10 / 32 / 100 mg/L
measured (geomtr mean): 0.7 / 2.0 / 6.0 / 35.8 / 55.7 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel:glass flasks total volume 65 mL
- Type (delete if not applicable): -
- Material, size, headspace, fill volume: 45 ± 1 mL
- Aeration:
- Type of flow-through (e.g. peristaltic or proportional diluter):
- Renewal rate of test solution (frequency/flow rate):
- Initial cells density: 2.6 *10^3 cells/mL
- Control end cells density: 8.6*10^4 cells/mL
- No. of organisms per vessel:
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6
- No. of vessels per vehicle control (replicates): -

GROWTH MEDIUM
- Standard medium used: yes
- Detailed composition if non-standard medium was used:

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water:
- Total organic carbon:
- Particulate matter:
- Metals:
- Pesticides:
- Chlorine:
- Alkalinity:
- Ca/mg ratio:
- Conductivity:
- Culture medium different from test medium:
- Intervals of water quality measurement:

OTHER TEST CONDITIONS
- Sterile test conditions: yes/no
- Adjustment of pH:
- Photoperiod:
- Light intensity and quality: 5000 lux
- Salinity (for marine algae):

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: [counting chamber; electronic particle counter; fluorimeter; spectrophotometer; colorimeter]
- Chlorophyll measurement:
- Other:

TEST CONCENTRATIONS
- Spacing factor for test concentrations:
- Justification for using less concentrations than requested by guideline:
- Range finding study
- Test concentrations:
- Results used to determine the conditions for the definitive study:

Reference substance (positive control):

yes

Remarks:

potassium dichromate (CAS# 7778-50-9)

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

18.64 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

2.71 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

2 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Results with reference substance (positive control):

The 72h-EC50s of potassium dichromate (K2Cr2O7, CAS No. 7778-50-9) were determined in a separate reference test. The values lay within the range of the laboratory (growth rate 0.73 - 1.10 mg/L, yield 0.21 – 0.66 mg/L).

Validity criteria fulfilled:

yes

Conclusions:

The test item shows a moderate acute and chronic toxicity to algae in the presented study.

Executive summary:

Three experiments were performed. In the 1^stexperiment two of the validity criteria were not met. Therefore, the experiment was repeated in the same way. The results of the 1^stexperiment are not detailed stated in the report, but will be kept together with the other raw data in the GLP archive of the test facility.

In the second experiment, all validity criteria were met and inhibition of algal growth was in the same range as in the first invalid experiment. However, because of erroneous sample preparation, analytical evaluation of the second experiment was partly not usable.

Therefore, a third experiment was performed in the same way. Determination of the biological results was based only on the result of the third experiment.

 

The study was performed using 5 concentrations ranging from 1.0 to 100 mg/L. Incubation time (test system Desmodesmus subspicatus) was 72 hours. The cell concentration of each replicate was determined by measuring the cell numbers every 24 hours with an electronic particle counter. Growth rate µ and the yield[1]were determined from the cell number at the respective observation times.

 

At the start and at the end of the test, the content of the test item in the test solutions item with and without algae was determined using HPLC.

In the third experiment the measured concentrations in the solution with and without algae were in a similar range. At the beginning of the third experiment the measured concentrations were in a range of 65 % - 133 % of the nominal concentration in the solutions with algae and 62 % - 128 % in the solutions without algae. At the end of the third experiment, the measured concentrations were in a range of 47 % - 94 % in the solutions with algae and 46 % - 91 % in the solutions without algae.

 

Therefore, the results were based on the geometric mean of the measured concentrations in the solution with algae.

 

The 72h-EC50s of potassium dichromate (K₂Cr₂O₇, CAS No. 7778-50-9) were determined in a separate reference test. The values lay within the range of the laboratory (growth rate 0.73 - 1.10 mg/L, yield 0.21 – 0.66 mg/L).

The following results for the test item 2,2'-Azobis (4-methoxy-2,4-dimethyl valeronitrile) were determined:

Table 3‑a         Results of the test item

Endpoint	NOEC	LOEC	EC10	EC50
Growth Rate	2.00 mg/L	6.00 mg/L	2.71 mg/L	18.64 mg/L
Yield	0.70 mg/L	2.00 mg/L	2.54 mg/L	5.27 mg/L

 

Description of key information

The toxicity of the test substance to algae is examined in an OECD 201 guideline study. The substance showed a moderate acute and chronic toxicity in the test. The thresholds are used as key values.

Key value for chemical safety assessment

EC50 for freshwater algae:

18.64 mg/L

EC10 or NOEC for freshwater algae:

2.71 mg/L