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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
Study period:
Study initiation date: March 29th, 2010. Experimental starting date: April 6th, 2010. Experimental completion date: April 9th, 2010. Study completion date: April 20th, 2010.
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
yes
Remarks:
All validity criteria except one was fulfilled. The mean coefficient of variation for section -by-section specific rates in the control cultures was 65 % exceeding the validation criteria (limit < 35 %).
GLP compliance:
yes
Remarks:
SNAS Reg. No. 049/G-020
Analytical monitoring:
yes
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
SAG Strain Number: 86.81. Source: Jan Futak Botanical Association, Bratislava. Received in the laboratory: 29.01.2010. Storage: a glass tube with slant agar alga culture stored in refrigerator at 5 C+/- 1 C.
Test type:
static
Water media type:
freshwater
Total exposure duration:
72 h
Test temperature:
Test was performed in the air-conditioned chamber with an automatic regulation and temperature monitoring. Average temperature in the chamber during the test was 23.6 C.
pH:
The Initial pH and the pH after 72 hours were measured in the controls and each test solutions during the test. The pH in the control varied between 8.00 to 9.31, and between 7.87 to 9.23 in the test solutions.
Nominal and measured concentrations:
The definitive test was performed with these nominal concentrations of the test substance: 0 mg/l, 312,5 mg/l, 625 mg/l, 1250 mg/l, 2500 mg/l, 5000 mg/l. Based on the preliminary test results on stability of the test substance, this substance was stable in the test media during 72 hours. Concentration of TOC (%) remained within 80-120 % of nominal concentration after 72 hours stability test. Therefore, no calculation adjustment of concentrations was needed in the proper test.
Details on test conditions:
Test media was prepared in accordance with SOP D28 365 A, and in compliance with OECD guideline. After preparation of alga pre-culture and stockculture, the initial biomass of the alga culture was 5000 cells/l in control and test solutions. Each test solution was prepared to the total test volume of 300 ml, containing 30 ml of alga stock solution and remaining volume of growth media. This total volume was distributed into 3 parallels. Control solution was prepared to the total test volume of 600 ml consisting of 540 ml of growth media and 60 ml of stock alga culture. This total volume was distributed into 6 parallels.

The inhibition of growth was used as an endpoint measurement expressed as the logarithmic increase in biomass. The specified growth rate inhibition was determined, and the results were expressed as EC10 and EC50-values. In addition, the NOEC-value was determined from the EC10-values.
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
120.2 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95 % confidence interval: 84.7-158.4 mg/l
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
1 199 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95 % confidence interval: 1078.7-1331.2 mg/l
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
<= 312.5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Results with reference substance (positive control):
Potassium dichromate was used as a reference substance. 72 hour EC50-value for potassium dichromate was 0.96 mg/l, and the result was within the range specified in ISO 8692 (0.6-1.08 mg/l).
Reported statistics and error estimates:
All effective concentrations were calculated using TOXEDO v.1.2 software. Confidence intervals (95 %) were determined for the EC-values. The NOEC-values were calculated using sofware Dunnet v 1.5.
Validity criteria fulfilled:
yes
Remarks:
The mean coefficient of variation for section -by-section specific rates in the control cultures was 65 % exceeding the validation criteria (limit < 35 %).
Conclusions:
The toxicity study of the test substance (Betafin BP20) on algae was conducted in compliance with Principles of Good Laboratory Practice. The study was carried out according to OECD guideline method 201. The inhibition of growth was used as an endpoint measurement expressed as the logarithmic increase in biomass. The specified growth rate inhibitions after 72 hours exposure were determined and toxicity was expressed as the EC10- and EC50-values.The EC10-value of the test substance was 120.2 mg/l with confidence interval of 84.7-158.4 mg/l. The EC50-value was 1199 mg/l with confidence interval of 1078.7-1331.2 mg/l. The NOEC-value of the test substance was < 312.5 mg/l after 72 hour exposure.
Executive summary:

The toxicity study of the test substance (Betafin BP20) on algae was conducted in compliance with Principles of Good Laboratory Practice. The study was carried out according to OECD guideline method 201. The inhibition of growth was used as an endpoint measurement expressed as the logarithmic increase in biomass. The specified growth rate inhibitions after 72 hours exposure were determined and toxicity was expressed as the EC10- and EC50-values.The EC10-value of the test substance was 120.2 mg/L with confidence interval of 84.7-158.4 mg/L. The EC50-value was 1199 mg/L with confidence interval of 1078.7-1331.2 mg/L. The NOEC-value of the test substance was < 312.5 mg/L after 72 hour exposure.

Description of key information

The study was carried out according to OECD guideline method 201. Growth inhibition of Desmodesmus subspicatus was determined as EC10- and EC50-values for 72 hours exposure. Also the NOEC-value for the average specific growth rate was calculated. The study was conducted in compliance with Principles of Good Laboratory Practice.  The EC10-value of the test substance was 120.2 mg/L with 95% confidence interval of 84.7-158.4 mg/L. The EC50-value was 1199 mg/L with 95% confidence interval of 1078.7-1331.2 mg/L. In addition, the NOEC-value for this substance was <312.5 mg/L. Test results indicate that this substance possesses low toxicity in freshwater.

Key value for chemical safety assessment

EC50 for freshwater algae:
1 199 mg/L
EC10 or NOEC for freshwater algae:
120.2 mg/L

Additional information

Acute toxicity testing of the substance (BETAFIN BP20) on algae (Desmodesmus subspicatus) was conducted in compliance with Principles of Good Laboratory Practice. The study was carried out according to the OECD guideline method 201. The inhibition of growth was used as an endpoint measurement expressed as the logarithmic increase in biomass. The specified growth rate inhibitions after 72 hours exposure were determined, and toxicity was expressed as the EC10- and EC50-values. The EC10-value of the test substance was 120.2 mg/L with 95 % confidence interval of 84.7-158.4 mg/L. The EC50-value was 1199 mg/l with 95 % confidence interval of 1078.7-1331.2 mg/L. In addition, the NOEC-value for the average specific growth rate after 72 h exposure time was calculated by using the software Dunnet v 1.5. The NOEC-value for this substance was <312.5 mg/L.

Aquatic toxicity test result (72 h) to D. subspicatus does not indicate the need for this substance to be classified as hazardous to the aquatic environment.