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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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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
Study period:
27 February 2017 - 12 June 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Version / remarks:
March 2006, corrected July 2011
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Remarks:
dated 14 January 2016
Analytical monitoring:
yes
Details on sampling:
Chemical analyses of the test item were performed in the test solutions:
- at the beiginning of the test (T = 0h),
- at the end of the test (T = 72h).
All the WAF solutions were analysed taken directly from the starting solutions without algae.
Vehicle:
no
Details on test solutions:
The test item was not soluble in the test medium, a special solubilisation protocol was carried out before the experimentation, according to the OECD n°23 guidance document on aquatic toxicity testing of difficult substances and mixtures.
This method consisted in stirring each test item nominal concentrations in test medium during 24 hours, in the dark and 20±2°C (these concentrations were prepared by adding directly the test item in flasks containing test medium).
All the test solutions (five concentrations) plus WAF Control (algae test medium) were then filtered through a membrane filter to remove suspended particles: solutions obtained were named WAF (Water Accommodated Fraction).
If the pH of the WAF solutions was not remain in the range 7.5 – 8.5, the pH adjustment was made with HCl and NaOH.
Test organisms (species):
Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)
Details on test organisms:
Freshwater unicellular green alga Pseudokirchneriella subcapitata of the chlorococcal order (formerly named Raphidocellis subcapitata) strain number CCAP 278.4 was used in this study.
The algae cultures are stored in the laboratory on a solid medium (LC/agar Petri plates) and in a liquid medium with regular sub-culturing (every week).
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
22.7 - 23.3°C
pH:
7.0 - 9.0
Nominal and measured concentrations:
nominal: 0, 10.0, 22.0, 48.4, 106.5, 234.3 mg/L of test substance
Details on test conditions:
This method consisted in stirring each test item nominal concentrations in test medium during 24 hours, in the dark and 20±2°C (these concentrations were prepared by adding directly the test item in flasks containing test medium).
All the test solutions plus Control (algae test medium) were then filtered through a membrane filter (cellulose acetate 0.45 µm batch G9952942) to remove suspended particles: solutions obtained were named WAF (Water Accommodated Fraction).
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
108.7 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: [84.3 - 158.9]
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
34.5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: [25.0 - 44.0]
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
48.4 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
106.5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
In the control, the increase of the biomass during 72 hours was determined to be higher than factor of 16.
The coefficients of variation of daily section-by-section specific growth rate and of average specific growth rate were determined respectively to be less than 35% and 7% in the control.
The validity criteria were successful fulfilled.

According the results, the concentration of the test item was well maintained within ± 20 per cent of the measured initial concentration at all wavelengths. Consequently, the test item was considered as stable in the testing conditions after 72 hours of exposure.
Results with reference substance (positive control):
The last algae growth inhibition test performed with the reference item K2Cr2O7 (January 23, 2017) gave an ErC50(0-72h) = 1.18 mg/L [1.03 – 1.36], indicating that the algae sensitivity is correct (within the accepted interval of 0.65 to 1.73 mg/L fixed by the International Standard NF EN ISO 8692 from Mai 2012 as mentioned in the OECD Guideline) and in accordance with previous data obtained by the laboratory.
Validity criteria fulfilled:
yes
Conclusions:
The results obtained for the test item on the toxicological endpoint “inhibition of growth rate” indicate an ErC50-(0-72h) equal to 108.7 mg/L [84.3 – 158.9] value expressed in nominal test item concentration.

The results obtained for the test item on the toxicological endpoint “inhibition of growth rate” indicate an ErC10-(0-72h) equal to 34.5 mg/L[25.0 – 44.0] value expressed in nominal test item concentration.

Description of key information

Under the experimental conditions of a test conducted according to OECD guideline 201, the results obtained for the test item on the toxicological endpoint “inhibition of growth rate” indicate:

- an ErC50-(0-72h) equal to 108.7 mg/L [84.3 – 158.9] value expressed in nominal test item concentration.

- an ErC10-(0-72h) equal to 34.5 mg/L[25.0 – 44.0] value expressed in nominal test item concentration.

Key value for chemical safety assessment

EC50 for freshwater algae:
108.7 mg/L
EC10 or NOEC for freshwater algae:
34.5 ng/L

Additional information