4-[[2-methoxy-4-[(4-nitrophenyl)azo]phenyl]azo]phenol

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2016-11-21 to 2016-11-25

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Range-finding study, not conducted under GLP

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

GLP compliance:

no

Remarks:

The study is a range-finder

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

A saturated solution with a nominal concentration of 100 mg/L was prepared once 24 ± 1 hour prior to the start of the exposure. An appropriate amount of the test item was weighed out. The test item was applied onto a glass slide. The glass slide with the test item was inserted into a glass bottle with an appropriate amount of dilution water (acc. to OECD201). The saturated solution was stirred for 24 hours (1100 rpm) with a magnetic stirrer. Undissolved particles were removed by membrane filtration (membrane filter 0.45 μm, RC, MACHEREY-NAGEL). The filter was saturated in order to avoid adsorption during the filtration. The first 25 mL of the filtrate were discarded. The filtration was interrupted for 10 minutes to allow adsorption and saturation of the filter material with dissolved test item. Thereafter, the filtration was continued. The next 25 mL was discarded. The following filtrate, i.e. the saturated solution, was used in the test. During filtration, the filter was always kept covered. The saturated solution was checked via laser beam (Tyndall effect). No Tyndall effect was observed.

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

21-24°C

Details on test conditions:

Light intensity: 4440 - 8880 Lux
Light regime: 24 h/d light

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

> 9.48 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 94.8 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Concentration (% saturated solution)	Growth rate inhibition (%)	Yield inhibition (%)
100	14	56
10	3	17
1	1	9

Validity criteria fulfilled:

not applicable

Conclusions:

Under the study conditions, the nominal 72 h ErC10 was >10 mg/L (equivalent to >9.48 mg a.i./L) and the nominal 72 h ErC50 was >100 mg/L (equivalent to >94.8 mg a.i./L).

Executive summary:

A range-finding study was conducted to determine the toxicity of the test substance (in the form of a dark brown powder of 94.8% purity) to green algae (Pseudokirchneriella subcapitata) according to OECD Guideline 201 and EU Method C3. A saturated solution at a nominal concentration of 100 mg/L was prepared once 24 ± 1 h prior to the start of exposure. An appropriate amount of the test substance was weighed out. The test substance was applied onto a glass slide. The glass slide was inserted into a glass bottle with an appropriate amount of dilution water. The saturated solution was stirred for 24 h (1100 rpm) with a magnetic stirrer. Undissolved particles were removed by membrane filtration (membrane filter 0.45 μm). The filter was saturated in order to avoid adsorption during the filtration. The first 25 mL of the filtrate were discarded. The filtration was interrupted for 10 min to allow adsorption and saturation of the filter material with dissolved test substance. Thereafter, the filtration was continued. The next 25 mL were discarded. The following filtrate, i.e. the saturated solution, was used in the test. During filtration, the filter was always kept covered. The saturated solution was checked via laser beam (Tyndall effect). No Tyndall effect was observed. Three concentrations were tested in a geometrical series with a dilution factor of 10: 1, 10 and 100 mg/L. Four replicates were tested for the control and two replicates per concentration. Under the study conditions, the nominal 72 h ErC10 was >10 mg/L (equivalent to >9.48 mg a.i./L) and the nominal 72 h ErC50 was >100 mg/L (equivalent to >94.8 mg a.i./L) (Klix, 2016).

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1990

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Qualifier:

according to guideline

Guideline:

other: Method DIN 38412, Part 9

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Common name: Scenedesmus subspicatus
- Strain: DSM 86.81

Test type:

static

Water media type:

freshwater

Remarks:

aerated

Limit test:

no

Total exposure duration:

72 h

Test temperature:

20 +/- 2°C

pH:

8.1 - 9.0

Nominal and measured concentrations:

Nominal: 1.56, 3.12, 6.25, 12.5, 25, 50 and 100 mg a.i./L

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 ml Erlenmeyers
- Type (delete if not applicable): open
- Fill volume: 100 ml
- No. of organisms per vessel: 10000 cells/ml

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Light intensity and quality: 120 uE/m*m*s

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: fluorimeter, measurement at 685 nm at 0, 24, 48 and 72 h

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

< 1.5 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC90

Effect conc.:

47 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

biomass

Conclusions:

Under the study conditions, the 72 h EC 10, 50 and 90 of the test substance to green algae (Scenedesmus subspicatus) were determined to be <1.5, 10 and 47 mg a.i./L (nominal).

Executive summary:

A study was conducted to determine the toxicity of the test substance (in the form of a 200 mg a.i./L dispersion) to green algae (Scenedesmus subspicatus) according to DIN Method 38412, Part 9. The algae were exposed to nominal concentrations of 1.56, 3.12, 6.25, 12.5, 25, 50 and 100 mg a.i./L for 72 h under static conditions. Biomass was measured as in vivo chlorophyll fluorescence at 685 nm after 24, 48 and 72h. No analytical validation of test concentrations was conducted. Under the study conditions, the 72 h EC 10, 50 and 90 were determined to be <1.5, 10 and 47 mg a.i./L (nominal) (Siebel-Sauer, 1990).

Description of key information

Key value for chemical safety assessment:

EC50/LC50 for freshwater algae: >94.8 mg a.i./L

EC10 for freshwater algae: >9.48 mg a.i./L

Additional information

A range-finding study was conducted to determine the toxicity of the test substance (in the form of a dark brown powder of 94.8% purity) to green algae (Pseudokirchneriella subcapitata) according to OECD Guideline 201 and EU Method C3. A saturated solution at a nominal concentration of 100 mg/L was prepared once 24 ± 1 h prior to the start of exposure. An appropriate amount of the test substance was weighed out. The test substance was applied onto a glass slide. The glass slide was inserted into a glass bottle with an appropriate amount of dilution water. The saturated solution was stirred for 24 h (1100 rpm) with a magnetic stirrer. Undissolved particles were removed by membrane filtration (membrane filter 0.45 μm). The filter was saturated in order to avoid adsorption during the filtration. The first 25 mL of the filtrate were discarded. The filtration was interrupted for 10 min to allow adsorption and saturation of the filter material with dissolved test substance. Thereafter, the filtration was continued. The next 25 mL were discarded. The following filtrate, i.e. the saturated solution, was used in the test. During filtration, the filter was always kept covered. The saturated solution was checked via laser beam (Tyndall effect). No Tyndall effect was observed. Three concentrations were tested in a geometrical series with a dilution factor of 10: 1, 10 and 100 mg/L. Four replicates were tested for the control and two replicates per concentration. Under the study conditions, the nominal 72 h ErC10 was >10 mg/L (equivalent to >9.48 mg a.i./L) and the nominal 72 h ErC50 was >100 mg/L (equivalent to >94.8 mg a.i./L) (Klix, 2016).

A study was conducted to determine the toxicity of the test substance (in the form of a 200 mg/L dispersion) to green algae (Scenedesmus subspicatus) according to DIN Method 38412, Part 9. The algae were exposed to nominal concentrations of 1.56, 3.12, 6.25, 12.5, 25, 50 and 100 mg a.i./L for 72 h under static conditions. Biomass was measured as in vivo chlorophyll fluorescence at 685 nm after 24, 48 and 72h. No analytical validation of test concentrations was conducted. Under the study conditions, the 72 h EC10, 50 and 90 were determined to be <1.5, 10 and 47 mg a.i./L (nominal) (Siebel-Sauer, 1990).

The more recent range finding study shows that the effects determined in the older study from 1990 most likely came from the colouration of the test solutions. Algae are known to be very sensitive to water colouration as it highly obstructs light absorption, leading to reduced photosynthesis and growth rate. In the study from 1990, 100 mg/L dispersant were used so that the test solutions were intensely coloured. The new study was performed without dispersant and the stock solution was filtrated additionally. Apparently, there is no effect on algal growth if no colouration happens. For risk assessment purposes, the results of the recent range finder are therefore used.