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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:
1999
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:
yes
Remarks:
MODIFIED ALGAL GROWTH INHIBITION TEST for colored test substances
Qualifier:
according to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
GLP compliance:
yes (incl. QA statement)
Remarks:
Swiss GLP
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: TVR50
- Expiration date of the lot/batch: September 01,2004

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: At room temperature at about 20 °C, away from direct sunlight
- Stability under test conditions: At least 24 hours (at room temperature)
- Solubility of the test substance in the solvent/vehicle: >80 g/l in water (20 °C)
Analytical monitoring:
yes
Details on sampling:
For the analytical measurements of the test item concentrations, duplicate samples were taken at the start of the test from the freshly prepared test media (without algae) of all test concentrations and from the control.
For the determination of the stability of the test item under the test conditions, and for the maintenance of the test item concentrations during the test period respectively, sufficient volumes of the freshly prepared test media of all test concentrations and the control were incubated under the same conditions as in the actual test (but without algae), and were sampled in duplicate at the end of the test (after the 72 h test period). The samples which were taken at the start of the test from the freshly prepared test media and from the control were stored in a refrigerator overnight and analyzed on the next day. All other samples were deep-frozen (at about -20 °C) immediately after sampling. The concentrations of the test item FAT 40'571/A were measured in the duplicate test media samples from all test concentrations and both sampling times (0 and 72 h). From the control samples only one of the duplicate samples was analyzed from each of both sampling times (0 and 72 h). The analytical procedure and results are described in the attached analytical report. Remaining samples are kept stored at about -20 °C to enable additional analyses. After delivery of the final test report all samples will be discarded.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
The test organism used for the study was Scenedesmus subspicatus CHODAT, Strain No. 86.81 SAG, supplied by the "Sammlung von Algenkulturen, Pflanzenphysiologisches Institut der Universität Göttingen", D-37073 Göttingen.
The algae had been grown in the RCC laboratories under standardized conditions according to the test guidelines.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
24 mg CaCO3/L
Test temperature:
22 - 23 °C
pH:
7.9 - 8.8
Nominal and measured concentrations:
nominal concentrations: 4.6, 10, 22, 46 and 100 mg/l.
The mean concentrations were found to be in the range of 78 % to 108 % of the spiked values, with an average of 93 % (n = 8), if the quantification is based on the main compound. For the quantification based on the sum of the peaks the main concentration were found to be in the range of 88 % to 101 % of the spiked values, with an average of 94 % (n = 8 ). Therefore, no correction for possible losses during the analytical procedure is necessary.
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 100 mg/L
Basis for effect:
growth rate
Validity criteria fulfilled:
yes
Conclusions:
The LC50 and NOEC of FAT 40571/A on the growth of Scenedesmus subspicatus was greater than 100 mg/l.
Executive summary:

The effect of FAT 40'571/A on the growth of the green algal species Scenedesmus subspicatus was investigated in a 72-h static test according to the EU C.3 and OECD 201 guideline. However, the test method was modified to quantify the algicidal effect of the test item, but also the growth inhibition effect caused by reduced light intensities in the colored test solutions.

The nominal test concentrations were 4.6, 10, 22, 46 and 100 mg/l and a control. All test media down to the lowest test concentration were slightly to strongly colored by the test item. In the test media the mean measured test item concentrations at the start of the test ranged from 100 to 105% of the nominal values, based on the main compound. During the test period of 72 h, the amount of the main compound decreased to 69 - 79% of the nominal values. Taking into consideration the sum of the main compound and the degradation products, the mean recoveries ranged from 86 to 94% during the test period of 72 h.

 

Therefore, all biological results are related to the nominal concentrations of the test item. The same growth inhibition of Scenedesmus subspicatus was observed when the algae grew in test water without test item, but under reduced light intensities by the filter effect of the colored test media as in the second parallel experimental part, where the algae grew in the test media with dissolved test item.

 

In conclusion, this modified algal test has clearly demonstrated that the observed growth inhibition effect of the test item FAT 40'571/A on Scenedesmus subspicatus was caused only due to an indirect effect, the light filter effect in the colored test solutions. Thus, a toxic effect of the test item on the algal cells can be excluded up to the highest test concentration of nominal 100 mg/l.

Description of key information

The LC50 and NOEC of the test substance on the growth of Scenedesmus subspicatus was greater than 100 mg/l. 

Key value for chemical safety assessment

Additional information

The effect on the growth of the green algal species Scenedesmus subspicatus was investigated in a 72-h static test according to the EU C.3 and OECD 201 guideline. The test method was modified to quantify the algicidal effect of the test item, but also the growth inhibition effect caused by reduced light intensities in the colored test solutions. The nominal test concentrations were 4.6, 10, 22, 46 and 100 mg/l and a control. All test media down to the lowest test concentration were slightly to strongly colored by the test item. In the test media the mean measured test item concentrations at the start of the test ranged from 100 to 105% of the nominal values, based on the main compound. During the test period of 72 h, the amount of the main compound decreased to 69 - 79% of the nominal values. Taking into consideration the sum of the main compound and the degradation products, the mean recoveries ranged from 86 to 94% during the test period of 72 h.

 

Therefore, all biological results are related to the nominal concentrations of the test item. The same growth inhibition of Scenedesmus subspicatus was observed when the algae grew in test water without test item, but under reduced light intensities by the filter effect of the colored test media as in the second parallel experimental part, where the algae grew in the test media with dissolved test item.

 

In conclusion, this modified algal test has clearly demonstrated that the observed growth inhibition effect on Scenedesmus subspicatus was caused only due to an indirect effect, the light filter effect in the colored test solutions. Thus, a toxic effect of the test item on the algal cells can be excluded up to the highest test concentration of nominal 100 mg/l.