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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
yes
Vehicle:
yes
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
24 degrees Celcius
pH:
7.6-8.6
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
cell number
Validity criteria fulfilled:
yes
Conclusions:
The effect of the test item on the growth of Pseudokirchneriella subcapitata has been investigated over a 72-Hour period and based on the geometric mean measured test concentrations gave the following results:
Response Variable EC50 (mg/L) No Observed Effect Concentration (NOEC) (mg/L)
Growth Rate >100 100
Yield >100 100
Executive summary:

Introduction

A study was performed to assess the effect of the test item on the growth of the green alga Pseudokirchneriella subcapitata. The method followed that described in the OECD Guidelines for Testing of Chemicals (2006) No 201, "Freshwater Alga and Cyanobacteria, Growth Inhibition Test" referenced as Method C.3 of Commission Regulation (EC) No 761/2009.

Methods

Preliminary solubility work conducted indicated that it was not possible to obtain a testable solution of the test item using traditional methods of preparation e.g. ultrasonication and high shear mixing.

A preliminary media preparation trial indicated that a dissolved test item concentration of approximately 85 mg/L was obtained from a saturated solution method of preparation indicating this to be the limit of water solubility of this item under test conditions.

Following a preliminary range-finding test, Pseudokirchneriella subcapitata was exposed to solutions of the test item at nominal concentrations of 1.0, 3.2, 10, 32 and 100% v/v saturated solution (three replicate flasks per concentration) for 72 hours, under constant illumination and shaking at a temperature of 24 ± 1 °C. The test item solutions were prepared by stirring an excess (100 mg/L) of test item in culture medium using a propeller stirrer at approximately 1500 rpm for 24 hours. After the stirring period any undissolved test item was removed by filtration (0.2 μm Sartorius Sartopore filter, first approximate 1 liter discarded in order to pre-condition the filter) to produce a 100% v/v saturated solution of the test item. This saturated solution was then further diluted as necessary, to provide the remaining test groups.

Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group, using a Coulter® Multisizer Particle Counter.

Results

Analysis of the 100 mg/L loading rate WAF at 0 hours showed a measured test concentration of 0.30 mg/L was obtained.  A decline in measured test concentration was observed at 72 hours to 0.080 mg/L.

Given that the toxicity cannot be attributed to a single component or a mixture of components but to the test item as a whole, the results were based on nominal loading rates only.

Exposure of Pseudokirchneriella subcapitata to the test item gave EL50 values of greater than 100 mg/L loading rate WAF.  The No Observed Effect Loading Rate (NOEL) was 100 mg/L loading rate WAF.

It was considered unnecessary and unrealistic to test at loading rates in excess of 100 mg/L loading rate WAF.

Description of key information

The effect of the test item on the growth of Pseudokirchneriella subcapitata has been investigated over a 72-Hour period and based on the geometric mean measured test concentrations gave the following results:

Response Variable       EC50 (mg/L)       No Observed Effect Concentration (NOEC) (mg/L)       

Growth Rate              >100                                   100                            

Yield                          >100                                   100       

Key value for chemical safety assessment

Additional information