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Ecotoxicological information

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:
19.02. - 26.03.1985
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
GLP compliance:
yes
Remarks:
The study was carried out under conditions of good laboratory practice. Within reason there have been no circumstances that might have affected the quality and integrity of the study.
Analytical monitoring:
no
Details on sampling:
Not applicable.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Two stock solutions for range-finding test: 1 and 20 g/L algal medium
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: Selenastrum capricornutum
- Strain: ATCC 22662
- Source (laboratory, culture collection): "American Type Culture Collection", Rockville, Maryland
- Preculture of algae in the exponential growth phase was prepared according to OECD 201


Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
4 d
Post exposure observation period:
not applicable
Hardness:
< 600 mmol/L (Ca+Mg)
Test temperature:
20 °C
pH:
no data
Dissolved oxygen:
no data
Salinity:
no data
Nominal and measured concentrations:
- concentration range in range-finding test : 0.06 - 200 mg/L (stock solution 1000mg/L Dicyandiamide)
- nominal concentrations in growth inhibition test: 0.1, 0.32, 0.56, 1.0, 1.8, 3.2 and 10 g/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 200 ml conical flasks
- Initial cells density: 2x10^4 cells/ml in range-finding test; 2x10^4 cells/ml in main test
- 50 ml of algal suspension was transferred to each flask and 50 ml of the test solution added
- Incubation of flasks in Gallenkamp incubator shaker below at set of fluorescence lamps (intensity +/- 5Klux) and shaken at 120 rpm
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 4
- additional single-background control series of test substance solution without algae
- range-finding test: after 4 days of incubation one sample was taken
- growth inhibition test: one sample was taken from each flask once a day on five consecutive days, and the number of algal cells per ml in the samples was determined (Coulter Counter model TAII)


TEST MEDIUM / WATER PARAMETERS
- NH4CL: 15 mg/L
- MgCL2*6H2O: 12 mg/L
- CaCl2*2H20: 18 mg/L
- MgSO4*7H2O: 15 mg/L
- KH2PO: 1.6 mg/L
- FeCl3*6H2O: 80 µg/L
- Na2EDTA*2H2O: 100 µg/L
- H3BO3: 185 µg/L
- MnCL2*4H2O: 415 µg/L
- ZnCl2: 3 µg/L
- CoCl2*6H20: 1.5 µg/L
- CuCl2*6H2O: 0.01 µg/L
- Na2MoO4*2H2O: 7 µg/L
- NaHCO3: 50 µg/L
- P < 700 µg/L
- N < 10 mg/L
- chelators < 0.8 mmol/L
- hardness (Ca+Mg) < 600 mmol/L
- Test medium was micropore filtered before use


EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: counting chamber
- Other: at the start and the end of the growth inhibition test, the morphologic form of the algae was examined microscopically


Reference substance (positive control):
no
Key result
Duration:
4 d
Dose descriptor:
EC50
Effect conc.:
2.04 g/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
Remarks on result:
other: 95 % CL: 1.95-2.13 g/L
Duration:
4 d
Dose descriptor:
NOEC
Effect conc.:
0.56 g/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
Details on results:
- Exponential growth in the control (for algal test): yes
- Range-finding test - results: effects could be expected at concentrations higher than 200 mg/L
- Observation of abnormalities (for algal test): microscopic examination of the cells at the start and the end of the incubation period revealed no morphological abnormalities in th ecells exposed to toxic concentrations of Dicyandiamide, techn. pure
Results with reference substance (positive control):
not applicable
Reported statistics and error estimates:
- the NOEC was estimated by comparison of the growth curves of the treated algal suspension with those of the blanks
- the EC50 was calculated by means of a parametric model developed by Kooijman et al. (method is more exact as method described in OECD 201)
Validity criteria fulfilled:
yes
Remarks:
Validity criteria according to OECD 201 are fulfilled.
Conclusions:
The EC50 with respect to growth rate was found to be 2.04 g/l, with a 95% confidence interval of 1.95 to 2.13 g/l.
The no-observed-effect concentration (NOEC) was estimated to be 0.56 g/l nominally.
Therefore, it can be concluded, that Dicyandiamide is not toxic to algae.
Executive summary:

In a 4 day acute toxicity study, cultures of Selenastrum capricornutum were exposed to Dicyandiamide at nominal concentrations of 0, 0.1, 0.32, 0.56, 1.0, 1.8, 3.2 and 10 g/L under static conditions in accordance with the OECD Guideline 201.

 

EC 50 (4 d) of Dicyandiamide was determined to be 2.04 g/L based on nominal concentrations.

The NOEC (4 d) was 0.56 g/L based on the nominal concentrations of Dicyandiamide.

Based on the toxicity of Dicyandiamide in this test and using the classification range given in Annex VI of the directive 67/548/EEC, Dicyandiamide is not toxic to algae.

Description of key information

In a 4 day acute toxicity study, cultures of Selenastrum capricornutum were exposed to Dicyandiamide at nominal concentrations of 0, 0.1, 0.32, 0.56, 1.0, 1.8, 3.2 and 10 g/L under static conditions in accordance with the OECD Guideline 201.

Key value for chemical safety assessment

EC50 for freshwater algae:
2 040 mg/L
EC10 or NOEC for freshwater algae:
560 mg/L

Additional information

EC 50 (4 d) of Dicyandiamide was determined to be 2.04 g/L (nominal concentrations) based on cell number.

The NOEC (4 d) was 0.56 g/L (nominal concentrations) based on cell number.

Based on the classification range given in Annex VI of the directive 67/548/EEC, Dicyandiamide is not toxic to algae.