Registration Dossier

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

Currently viewing:

Administrative data

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:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Vehicle:
no
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
20.4 – 22.8 °C
pH:
7.3 - 9.2
Nominal and measured concentrations:
1 / 3.2 / 10 / 32 / 100 mg/L nominal concentration
The measured concentrations lay between 94 % and 98 % of the nominal concentrations at the beginning of the test and between 99 % and 110 % of the nominal concentrations at the end of the test. Therefore, the biological results were based on the nominal concentrations.
Details on test conditions:
For each treatment, 200 mL of the respective test item solution was mixed with the neces-sary amount of algal pre-culture (0.289 mL) to achieve a cell concentration of 2.7 *103 cells/mL. For the blank control, 350 mL nutrient medium was used instead of test item so-lution and mixed with the necessary amount of algal pre-culture (0.505 mL). In this mix-ture, the pH-value was measured.
The real cell concentration at the beginning of the test was measured with an electronic particle counter in the blank control solution. This measured value was used as start cell concentration for all replicates.
The test vessels were filled with 45 ± 1 mL of the respective test solution and incubated open (covered with perforated plastic foil acting as a stopper) for 72 hours, shaken on an orbital shaker to keep the algae in suspension. Before the start of incubation and every 24 hours, the cell number was determined with an electronic particle counter. After the test the pH value in treatments and blank control was measured again.
At the end of the test, the treatments were examined microscopically in order to assess the appearance of the algae and detect abnormalities (e.g. caused by the exposure to the test item).
The concentration of the test item in the test vessels was measured at the start and at the end of the test
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
13.58 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.:
2.7 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
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.:
27.07 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number

Table 1      Cell Number/mL

Nominal Concentration in mg/L

Parameter

Cell Number/mL

0 h

24 h

48 h

72 h

Blank control

Mean

2740

7780

67377

362663

Blank control

SD

0

1020

5412

4052

1

Mean

2740

7027

51753

301813

1

SD

0

926

9474

2826

3.2

Mean

2740

6627

57860

310987

3.2

SD

0

1026

5421

26670

10

Mean

2740

5747

55527

282260

10

SD

0

696

7072

17486

32

Mean

2740

5140

25273

134967

32

SD

0

1068

532

8167

100

Mean

2740

5147

27060

94320

100

SD

0

240

3912

6463

SD = Standard Deviation

Validity criteria fulfilled:
yes
Conclusions:
Based on the test results the ErC10, 72 h can be stated to be 13.58 mg/L and the ErC50, 72 h can be stated to be > 100 mg/L, respectively.
Executive summary:

One valid experiment was performed.

The study was performed using 5 concentrations ranging from 1.0 to 100 mg/L (nominal). 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.

Significant inhibition of algal growth was observed in all tested concentrations.

 

At the start and at the end of the test, the content of the test item in the test solutions was determined using HPLC.

The measured concentrations lay between 94 % and 98 % of the nominal concentrations at the beginning of the test and between 99 % and 110 % of the nominal concentrations at the end of the test. Therefore, the biological results were based on the nominal concentrations.

For the endpoint growth rate, inhibition at the highest concentration 100 mg/L was 27.6 %. Therefore the statistics program could not calculate an EC50. Hence for the Growth rate, the EC 50 value is specified as a range.

The 72h-EC50values 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 0.65 - 1.10 mg/L, yield 0.21 – 0.66 mg/L).

The following results for the test itemL-Tyrosine, 3,5-dinitro- (wet product)were determined:

Table 2        Results of the test item

Endpoint

NOEC

LOEC

EC10

EC50

Growth Rate

≤1 mg/L

< 1 mg/L

13.58 mg/L

> 100 mg/L

Yield

≤1 mg/L

< 1 mg/L

2.70 mg/L

27.07 mg/L


[1]Yield (according to OECD Guideline 201) is defined as the biomass at the end of the exposure period minus the biomass at the start of the exposure period. Calculation see under 8.2 Growth and growth inhibition are quantified from measurements of the algal biomass as a function of time. Algal biomass is defined as the dry weight per volume, e.g. mg algae/L test solution. However, dry weight is difficult to measure and therefore surrogate parameters are used. Of these surrogates, cell counts are most often used.

Description of key information

One study was performed according to OECD 201.

Based on the test results the ErC10, 72 h can be stated to be 13.58 mg/L and the ErC50, 72 h can be stated to be > 100 mg/L, respectively.

For the discussion of the classification see summary of aquatic toxicity.

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L
EC50 for marine water algae:
100 mg/L
EC10 or NOEC for freshwater algae:
13.58 mg/L
EC10 or NOEC for marine water algae:
13.58 mg/L

Additional information