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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
28-03-2017 to 05-01-2018
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Justification for type of information:
For industrial enzymes, the PNEC (predicted no effect concentration) value for enzymes in general is considered the highest dose tested for a given endpoint in studies conducted and published by the enzyme industry. The one exception is for some proteases and oxidoreductases, where effects may be observed at lower concentrations. Similarly, although the algal growth inhibition study with sedolisin was not conducted GLP, the 48-hour algal growth inhibitory effect concentration (EC50) for sedolisin was greater than the limit dose of 100 mg/L. The weight-of-evidence indicates that enzymes in general are not or of very low ecotoxicity.

Due to the similarity between the two enzymes, similar results are expected for trypsin.
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
Qualifier:
according to
Guideline:
ISO 8692 (Water Quality - Fresh Water Algal Growth Inhibition Test with Scenedesmus subspicatus and Selenastrum capricornutum)
Deviations:
no
Principles of method if other than guideline:
Only nominal concentrations.
GLP compliance:
no
Remarks:
See *justification for type of information'
Test material information:
Composition 1
Analytical monitoring:
no
Details on sampling:
- Concentrations: 10, 30, 50, 70, 100 TOS mg/L.
Vehicle:
no
Details on test solutions:
According to the MicroBiotests Inc SOP.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: Unicellular green algae
- Strain: Pseudokirchneriella subcapitata
- Source (laboratory, culture collection): MicroBiotests Inc. The algal growth inhibition bioassay has been developed by the research teams at the Laboratory for Biological Research in Aquatic Pollution (LABRAP) at the University of Ghent in Belgium.
- Method of cultivation: According to the MicroBiotests Inc. SOP.
Algae are supplied as de-immobilized algal beads.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
23°C +/- 2 °C
pH:
8.1 +/- 0.2
Dissolved oxygen:
Media was saturated with air before use
Nominal and measured concentrations:
Nominal concentrations
Details on test conditions:
TEST SYSTEM
- Test vessel: 25 mL calibrated flask
- Material, size, headspace, fill volume: 25 mL
- Initial cells density: 1*10^4 algae/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3

GROWTH MEDIUM
- Standard medium used: yes.
- Detailed composition if non-standard medium was used: As described in OECD Guideline 201and the ISO/DIS Guideline 8692.

OTHER TEST CONDITIONS
- Sterile test conditions: no
- Photoperiod: 72 h
- Light intensity and quality: 10000 lux for sideway illumination or min. 3000-4000 lux for bottom illumination

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: spectrophotometer
Reference substance (positive control):
no
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 24.7 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 other: mg TOS/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
> 10 other: mg TOS/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
> 2.5 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Details on results:
No significant growth inhibition and no abnormalities were observed.
Validity criteria fulfilled:
yes
Conclusions:
Endopeptidase, batch PPF38268 was tested in concentrations 10, 30, 50, 70, 100 TOS mg/L. It was found to inhibit growth rate at all concentrations tested after 72h exposure, whereas no significant inhibition was observed after 24 and 48h exposure. Inhibition of the growth rate at 72h was found to be approximately 3% at 10 mg TOS/L, 34 % at 30 mg TOS/L, 30% at 50 mg TOS/L, and 12 % at 100 mg TOS/L indicating only slightly toxicity towards algal growth. There was no dose-response relationship and because of the low observed toxicity towards algal growth no ErC50 value could be estimated and must be > 100 mg TOS/L (> 24.7 mg aep/L). The NOEC value was determined to be < 10 mg TOS/L (< 2.5 mg aep/L).
Executive summary:

The purpose of this study was to screen for toxicity of endopeptidase, batch PPF38268 towards algae. A 72h algal growth inhibition test was performed in long cell test vials with Pseudokirchneriella subcapitata. Algae are supplied as de-immobilized algal beads. The Algal tox kit test follows the prescriptions of the OECD "Algal growth inhibition test" (Guideline 201) and the ISO "Water Quality Freshwater Algal Growth Inhibition Tests with Unicellular Green Algae" (ISO Standard 8692). Endpoint of the study is percent inhibition (I%) of algal growth rate compared to the control.

IC50: Calculated/estimated 50% growth inhibition compared to control algae.

Endopeptidase, batch PPF38268 was found to inhibit growth rate at all concentrations tested after 72h exposure, whereas no significant inhibition was observed after 24 and 48h exposure. Inhibition of the growth rate at 72h was found to be approximately 3% at 10 mg TOS/L, 34 % at 30 mg TOS/L, 30% at 50 mg TOS/L, and 12 % at 100 mg TOS/L indicating only slightly toxicity towards algal growth. There was no dose-response relationship and because of the low observed toxicity towards algal growth no ErC50 value could be estimated and must be > 100 mg TOS/L (> 24.7 mg aep/L). The NOEC value was determined to be < 10 mg TOS/L (< 2.5 mg aep/L).

Description of key information

The toxicity of trypsin in algae was not tested, however, an enzyme from the same sub-subclass - sedolisin - was tested.

There was no dose-response relationship and because of the low observed toxicity towards algal growth no ErC50 value could be estimated and must be > 100 mg TOS/L (> 24.7 mg aep/L). The NOEC value was determined to be < 10 mg TOS/L (< 2.5 mg aep/L). Due to the similarity between the two enzymes, similar results are expected for trypsin.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater algae:
2.5 mg/L

Additional information