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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)

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Details on sampling:

Range finding test : a preliminary test performed to find the range of toxicity of the test item. The test sample has been prepared at 1000mg/L in culture medium. 5 different concentrations have been prepared with ten-folds dilutions to 0.1 mg/L and then tested.
Definitive test : a test performed after a range finding test to calculate the toxicity of the test item (limit test or EC50 test). The test sample has been prepared at 100 mg/L in culture medium.

Details on test solutions:

Concentration tested :
Range findin test : 5 different concentrations have been prepared with ten-folds dilutions to 0.1 mg/L
Definitive test : 100 mg/L in culture medium

Test organisms (species):

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

Details on test organisms:

Test organism : Green algae
Genus : Pseudokirchneriella
Species : subcapitata
Family : Chlorophyceae
Order : Chlorococcalles

Test type:

semi-static

Water media type:

saltwater

Limit test:

yes

Total exposure duration:

72 h

Post exposure observation period:

no

Test temperature:

23 ± 2°C

Nominal and measured concentrations:

Determination of analytical concentration of total organic carbon (TOC) using an automatic Sievers analyser.

Details on test conditions:

Range finding test :
Starting cellular density = 10000
Number of replications : 3 for all treated tested concentration and 3 for control
Definitive test :
Starting cellular density = 10000
Number of replications : 6 for the treated tested concentration and 6 for control

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Details on results:

Cellular concentration : A normal and healthy appearance of the algae at the end of the test was observed at microscopic for control and treated group.
pH : the results for definitive test satisfy the requirements of the regulation (pH must not deviate by more than 1.5 units during the test).
temperature : the results for definitive test atisfy the requirements of the guideline (23± 2°C)
Analytical verification of the concentration of the test item : The test item should be considered stable, because the TOC values and the end of the test remain in the required range (80-120%) respect to the initial values.
EC50 > 100 mg/L

Validity criteria fulfilled:

yes

Conclusions:

The obtained results, in compliance with assay validity criteria, showed that the Algae Growth Inhibition rate (Ir%) after 72 hours at the concentration of 100 mg/l of the test item "KERASTIM S" is 2.73%. EC50> 100 mg/I.

Executive summary:

On the test item "KERASTIM S" the growth inhibition test on a culture of algae Pseudokirchneriella subcapitata was performed on a culture in exponential growth phase.

This approach, according to OECD 201, allowed to calculate the growth inhibition (effect) concentration to the 50% of the organisms (EC₅₀).

During the range finding test the algae have been exposed to 5 different dilutions of the test item for 72 hours.

After the results of the range finding test a limit test has been performed. The algae have been exposed to 100 mg/I of the test item for 72 hours.

After this period the cellular concentration has been measured using a Burker chamber.

At the end of the test, microscopic observation was performed to verify a normal and healthy appearance of the inoculum culture and to observe any abnormal appearance of the algae.

At the beginning and at the end of the test (72 hours), pH and temperature have been measured in all the vessels. Organic carbon concentration (TOC) have been measured at the beginning and at the end of the test in a pool derived from vessels in the control and in the treated.

The obtained results, in compliance with assay validity criteria, showed that the Algae Growth Inhibition rate (I_r%) after 72 hours at the concentration of 100 mg/I of the test item "KERASTIM S" is 2.73%.

Description of key information

The obtained results, in compliance with assay validity criteria, showed that the Algae Growth Inhibition rate (Ir%) after 72 hours at the concentration of 100 mg/l of the test item "KERASTIM S" is 2.73%. EC50> 100 mg/I.

Key value for chemical safety assessment

EC50 for freshwater algae:

100 mg/L