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Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
02-05-2017 - 05-05-2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
Experimental test result performed using standard test guidelines
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
no
Analytical monitoring:
not specified
Vehicle:
yes
Details on test solutions:
The stock solution (10 mg/L) was prepared by dissolving yellow powder in OECD growth medium. The solution was kept in ultrasonic bath for 20 min. Test solutions of required concentration were prepared by mixing the stock solution of the test sample with OECD growth medium and inoculum culture.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: -
- Strain: 86.81 SAG
- Source (laboratory, culture collection): Institute of botany of the ASCR
- Initial biomass concentration: 5x10(3) cells /ml
- Method of cultivation: No data available

ACCLIMATION - No data available
- 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
Remarks on exposure duration:
±1 hour
Test temperature:
23 ± 2°C
pH:
Without adjustment
The sample at concentration 0.80 mg/L did not change during the tests
Control: pH= 8.0 changed to pH 7.4 during the test
Nominal and measured concentrations:
0, 0.5, 0.10, 0.20, 0.40 and 0.80 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 50 ml Glass vessel
- Type (delete if not applicable): closed (with air permeable stopper)
- Sample volume: 15 ml
- Initial cells density: 5x10(3) cells/ml
- No. of vessels per concentration (replicates): 3

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Photoperiod: Continuous
- Light intensity and quality: 6000-8000 lx

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: microscope with counting chamber Cyrus I or electronic particle counter.
- Other: ErC50 was calculated using non-linear regression by the software Prism 4.0
Reference substance (positive control):
yes
Remarks:
Potassium dichromate (K2Cr2O7)
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.17 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 0.16 - 0.19 mg/L
Results with reference substance (positive control):
Results with reference substance valid
- EC50: 0.75 mg/L
Validity criteria fulfilled:
not specified
Conclusions:
The median effective concentration (EC50) for the test substance, 4-(phenylazo)benzene-1,3-diamine, in Desmodesmus subspicatus was determined to be 0.17 mg/L on the basis of effects on growth rate in a 72 hour study.
Executive summary:

Freshwater algal growth inhibition test was carried out on Desmodesmus subspicatus with the substance 4-(phenylazo)benzene-1,3-diamine according to OECD Guideline 201.

The test substance was dissolved in OECD growth medium and tested at the concentrations 0, 0.5, 0.10, 0.20, 0.40 and 0.80 mg/L. Effects on the growth rate of the organism were studied.

The median effective concentration (EC50) for the test substance, 4-(phenylazo)benzene-1,3-diamine, in Desmodesmus subspicatus was determined to be 0.17 mg/L.

This value indicates that the substance is likely to be hazardous to aquatic algae and can be classified as Aquatic acute category 1 as per the CLP criteria.

Description of key information

The median effective concentration (EC50) for the test substance, 4-(phenylazo)benzene-1,3-diamine, in Desmodesmus subspicatus was determined to be 0.17 mg/L on the basis of effects on growth rate in a 72 hour study.

Key value for chemical safety assessment

EC50 for freshwater algae:
0.17 mg/L

Additional information

Different studies, experimental and predicted, of the substance4-(phenylazo)benzene-1,3-diamine were reviewed for Short term toxicity to aquatic algae and cyanobacteria endpoint and are summarised as follows:

Freshwater algal growth inhibition test was carried out on Desmodesmus subspicatus with the substance 4-(phenylazo)benzene-1,3-diamineaccording to OECD Guideline 201. The test substance was dissolved in OECD growth medium and tested at the concentrations0, 0.5, 0.10, 0.20, 0.40 and 0.80 mg/L. Effects on the growth rate of the organism were studied. The median effective concentration (EC50) for the test substance,4-(phenylazo)benzene-1,3-diamine, in Desmodesmus subspicatus was determined to be 0.17 mg/L.

Supporting data from other lab indicates, the effect of test item 4-(phenylazo)benzene-1,3-diamine, CAS No. 495-54-5 was studied on the growth of fresh water green alga Chlorella vulgaris. The study was conducted following OECD guideline 201- Alga, growth inhibition test. The test concentration chosen for the study were 0.9 mg/L,2.7 mg/L,8.1 mg/L,24.3 mg/L,72.9 mg/L,218.7 mg/L. The test concentrations were prepared using stock solution of the test item using mineral media. The green alga was exposed to the test concentration for a period of 72 hours to observe average specific growth rate and % growth inhibition under the effect of the test item. EC50 calculated graphically through probit analysis was observed to be 10.07mg/L.

Further supporting data is based on the QSAR prediction done using the EPI Suite ECOSAR version 1.11, the 72 hours EC50 was estimated to be 0.653 mg/L on algae for substance 4-(Phenylazo)benzene-1,3-diamine with growth inhibition effects.

Thus considering the key and supporting values, the EC50 value is observed to be in the range 0.17 - 10.07 mg/L. But considering the harmonised classification of the substance and for the purpose of classification and chemical safety assessment the substance 4-(phenylazo)benzene-1,3 -diamine is considered to classified as Aquatic acute 1 and aquatic chronic 1 category.