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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)
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
yes
Remarks:
During the final test the temperature was stable within 2.3 instead of 2.0ºC. Evaluation: Extend of the deviation was insignificant and therefore, had no effect on the results.
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
- Concentrations:
- Sampling method:
- Sample storage conditions before analysis:
Vehicle:
no
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Reference substance (positive control):
yes
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
67 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL 52 - 85 mg a.i./L
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
32 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
biomass
Remarks on result:
other: 95% CL 21 - 47 mg a.i./L
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
18 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Validity criteria fulfilled:
yes
Conclusions:
Under the conditions of a GLP OECD 201 study with Pseudokirchneriella subcapitata, MEA Polyborate 1:3 reduced growth rate and inhibited the yield of this fresh water algae species significantly at 32 mg a.i./l and higher.

The EC50 for growth rate reduction (ERC50: 0-72h) was 67 mg a.i./l with a 95 % confidence interval ranging from 52 to 85 mg a.i./l.

The EC50 for yield inhibition (EYC50: 0-72h) was 32 mg a.i./l with a 95 % confidence interval ranging from 21 to 47 mg a.i./l.

The NOEC for growth rate reduction and yield inhibition was 18 mg a.i./l.

Executive summary:

Pseudokirchneriella subcapitata, Fresh Water Algal Growth Inhibition Test with

MEA Polyborate 1:3.

 

The study procedures described in this report were based on the OECD guideline No. 201, 2006. In addition, the procedures were designed to meet the test methods of the Commission Regulation (EC) No 440/2008, Part C.3, 2008; Amended by EC No. 761/2009and the ISO International Standard 8692, 2004.

 

The test substance, MEA Polyborate 1:3, is a complex multi-component substance (a UVCB or unknown variable complex or biological) substance containing salt and non-salt compounds in rapid equilibrium. The test substance is prepared from monoethanolamine, borate compounds and water. The non-water components (regarded as the active ingredient, a.i.) are 68% (w/w) of the test substance. The batch of test substance used was a clear colourless liquid and completely soluble in test medium at the concentrations tested.

 

A final test was performed based on the results of a range-finding test. Preparation started with a concentration of 100 mg active ingredient (a.i.)/l which corresponds to 147 mg MEA Polyborate 1:3 per litre. To this end 115 µl of the test substance was added to 1000 ml test medium and magnetically stirred for a period of 15 minutes. The pH of the highest concentration was adjusted with 1M HCl (Merck, Darmstad, Germany). The lower test concentrations were prepared by subsequent dilutions of the highest concentration in test medium.

Samples taken from the nominal concentrations of 14.7, 26.5, 47, 82 and 147 mg/l (i.e. 10, 18, 32, 56 and 100 mg a.i./l) were analysed. The concentrations of both boron and MEA were determined.

 

Boron analyses: The nominal concentrations of boron in analysed samples were 1.71, 3.07, 5.45, 9.55 and 17.1 mg boron per litre, respectively.

 

Analysis of the samples taken at the start of the final test showed that the actual concentrations were in agreement with nominal (90 - 92% of nominal) and except for the samples taken from the nominal concentrations of 18 and 56 mg a.i./l, the measured concentrations remained stable during the entire period of exposure (99 – 107% of initial). The measured concentrations in the samples taken from nominally 18 and 56 mg a.i./l decreased to 21 and 54% of initial after 24 hours of exposure, respectively. The measured concentrations remained stable to the end of the exposure.

MEA analyses: The nominal concentrations of MEA in analysed samples were 2.5, 4.51, 7.99, 14 and 25 mg MEA per litre, respectively.

 

Analysis of the samples taken at the start of the final test showed that the actual concentrations were in agreement with nominal, i.e 99 - 107% of nominal and remained stable during the entire test period (86 - 99% of initial).

 

The cause of the decrease of boron concentrations in two samples during the first 24 hours of exposure is not known. Note that at the same time the concentration of MEA in the same test solutions remained stable. Moreover, the concentrations of boron in the mentioned samples did not decrease during the following 48 hours of exposure and in all other test groups the concentrations of boron were stable during the entire test period. Therefore, the effect concentrations were expressed in terms of the nominal concentrations of the active ingredient.

The study met the acceptability criteria prescribed by the protocol and was considered valid.

MEA Polyborate 1:3 reduced growth rate and inhibited the yield of this fresh water algae species significantly at 32 mg a.i./l and higher.

 

The EC50for growth rate reduction (ERC50: 0-72h) was 67 mg a.i./l with a 95 % confidence interval ranging from 52 to 85 mg a.i./l. This value is considered a short-term or acute endpoint under the OECD Guideline.

 

 

The EC50for yield inhibition (EYC50: 0-72h) was 32 mg a.i./l with a 95 % confidence interval ranging from 21 to 47 mg a.i./l.

 

The NOEC for both growth rate reduction and yield inhibition was 18 mg a.i./l. These values are considered long-term or chronic endpoints under the OECD Guideline.



Description of key information

Under the conditions of a GLP OECD 201 study with Pseudokirchneriella subcapitata, MEA Polyborate 1:3 reduced growth rate and inhibited the yield of this fresh water algae species significantly at 32 mg a.i./l  and higher.

The EC50 for growth rate reduction (ERC50: 0-72h) was 67 mg a.i./l  with a 95 % confidence interval ranging from 52 to 85 mg a.i./l.

Key value for chemical safety assessment

EC50 for freshwater algae:
67 mg/L

Additional information