N-(2-chloroethyl)-4-[(2,6-dichloro-4-nitrophenyl)azo]-N-ethyl-m-toluidine

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

The batch of Disperse Brown 27 (4852-1501) tested was a brown powder with a purity of 99.7 %

Analytical monitoring:

yes

Details on sampling:

2mL samples were taken at t=0, t=24h and t=72h

Vehicle:

yes

Details on test solutions:

The batch of Disperse Brown 27 tested was a brown powder with a purity of 99.7 % and the item was not completely soluble in test medium at the concentrations tested. No correction was made for the purity/composition of the test item.
Preparation of test solutions started with a loading rate of 100 mg/L applying a 3- day period of magnetic stirring to ensure maximum dissolution of the test item in medium. The obtained mixture was filtered through a 0.45 μm membrane filter (RC55, Whatman). The resulting SS was used as the highest test concentration. Lower test concentrations for the range-finding test were prepared by subsequent dilutions of the SS in test medium. All test solutions were clear and colorless at the end of the preparation procedure. After preparation, volumes of 50 mL were added to each replicate of the respective test concentration. Subsequently, 1 mLof an algal suspension was added to each replicate providing a cell density of 104 cells/mL.

Test organisms (species):

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

Details on test organisms:

strain: NIVA CHL 1
Source: In-house laboratory culture.
This system is a unicellular algal species sensitive to toxic items in the aquatic ecosystem and has been selected as an internationally accepted species.

Test type:

static

Water media type:

other:

Remarks:

Milli-RO water

Limit test:

yes

Total exposure duration:

72 h

Hardness:

0.24 mmol/L (24 mg CaCO3/L)

Test temperature:

22-23 °C (21-24 °C constant within 2 °C, as outlined in study plan)

pH:

8.1 ± 0.2, pH recorded at the beginning and the end of the test. The pH was generally within the limits prescribed by the study plan (6.0-9.0, preferably not varying by more than 1.5 unit).

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.085 µg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

> 0.085 µg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC20

Effect conc.:

> 0.085 µg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 0.085 µg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.085 µg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

cell number

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

> 0.085 µg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

cell number

Duration:

72 h

Dose descriptor:

EC20

Effect conc.:

> 0.085 µg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

cell number

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 0.085 µg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

cell number

Details on results:

The EC50 for growth rate (72h-ERC50) and yield inhibition (72h-EYC50) was beyond the range tested, i.e. exceeded a TWA concentration of 0.085 μg/L. The 72h-NOEC for both growth rate and yield inhibition was 0.085 μg/L. Due to the very low solubility of Disperse Brown 27 in water, concentration levels that might be toxic for algae could not be reached.
No significant differences were recorded between the values for growth rate or yield at the limit concentration when compared to the control group.
Microscopic observations at the end of the test revealed a normal and healthy appearance of the algal cells exposed to the limit concentration when compared to the control.

Validity criteria fulfilled:

yes

Conclusions:

In conclusion, under the conditions of the present study with Pseudokirchneriella subcapitata, no inhibition of growth rate or inhibition of yield was recorded at any of the concentrations of Disperse Brown 27 tested. The EC50 for growth rate (72h-ERC50) and yield inhibition (72h-EYC50) was beyond the range tested, i.e. exceeded a TWA concentration of 0.085 μg/L. The 72h-NOEC for both growth rate and yield inhibition was 0.085 μg/L. Due to the very low solubility of Disperse Brown 27 in water, concentration levels that might be toxic for algae could not be reached.

Executive summary:

The batch of Disperse Brown 27 tested was a brown powder with a purity of 99.7 % and the item was not completely soluble in test medium at the concentrations tested. A Saturated Solution (SS) was prepared at a loading rate of 100 mg/L and used as the highest concentration. Lower concentrations were prepared by diluting the highest concentration in test medium.

A final test was performed as a limit test, based on the results of a preceding combined limit/range-finding test. Six exponentially growing algal cultures were exposed to an untreated control and to the undiluted SS. The initial algal cell density was 104 cells/mL. The total exposure period was 72 hours and samples for analytical confirmation of actual exposure concentrations were taken at the start, after 24 and 72 hours of exposure.

Analysis of the samples taken from the limit concentration at the start of the test showed an actual concentration was 0.203 μg/L. The measured concentration decreased below the limit of detection of the analytical method at the end of the test. The calculated Time Weight Average concentration (TWA) was 0.085 μg/L.

The study met the acceptability criteria prescribed by the study plan and was consideredvalid.

The effect parameters obtained in this study are as follows. Growth rate and yield NOEC (0.085 µg/L), EC10 (>0.085* µg/L), EC20 (>0.085* µg/L), EC50 (>0.085* µg/L). Note * states 95% confidence intervals could not be calculated.

Due to the very low solubility of Disperse Brown 27 in water, concentration levels that might be toxic for algae could not be reached.

Description of key information

In conclusion, under the conditions of the present study with Pseudokirchneriella subcapitata, no inhibition of growth rate or inhibition of yield was recorded at any of the concentrations of Disperse Brown 27 tested. The EC50 for growth rate (72h-ERC50) and yield inhibition (72h-EYC50) was beyond the range tested, i.e. exceeded a TWA concentration of 0.085 μg/L. The 72h-NOEC for both growth rate and yield inhibition was 0.085 μg/L. Due to the very low solubility of Disperse Brown 27 in water, concentration levels that might be toxic for algae could not be reached.

Additional information

In conclusion, under the conditions of the present study with Pseudokirchneriella subcapitata, no inhibition of growth rate or inhibition of yield was recorded at any of the concentrations of Disperse Brown 27 tested. The EC50 for growth rate (72h-ERC50) and yield inhibition (72h-EYC50) was beyond the range tested, i.e. exceeded a TWA concentration of 0.085 μg/L. The 72h-NOEC for both growth rate and yield inhibition was 0.085 μg/L. Due to the very low solubility of Disperse Brown 27 in water, concentration levels that might be toxic for algae could not be reached.