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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Link to relevant study record(s)

Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Justification for type of information:
Guideline study to GLP
The study performed on hop extract is relevant for tetrahydroiso-alpha acids, since tetrahydroiso-alpha acids are derived from hop extract. A further study has been planned for iso-alpha acids and will be entered as an update.
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Batch no. 160025
Analytical monitoring:
yes
Vehicle:
no
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
Strain CCAP 278/4
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
20.7 - 26.0 oC
pH:
7.53 - 8.08
Reference substance (positive control):
yes
Remarks:
Separate GLP rerefence study on potassium dichromate
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
ca. 86.7 mg/L
Conc. based on:
test mat.
Basis for effect:
biomass
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
ca. 83.1 mg/L
Conc. based on:
test mat.
Basis for effect:
biomass
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
ca. 25 mg/L
Conc. based on:
test mat.
Basis for effect:
biomass
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
ca. 42.7 mg/L
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
ca. 52.5 mg/L
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
ca. 12.5 mg/L
Conc. based on:
test mat.
Basis for effect:
growth rate
Validity criteria fulfilled:
yes
Conclusions:
Notes from report:

The definitive test conducted from 06 to 09 March 2018 was performed according to the OECD 201 (2011) guideline.
The growth curves demonstrate that the algae in the control were in logarithmic growth for the duration of the study.
The 48 hour EC(r)50 and EC(y)50 of HOP EXTRACT to Pseudokirchneriella subcapitata were 86.7mg/l and 42.7mg/l respectively (both determined by Maximum Likelihood-Logit).
The 72 hour EC(r)50 and EC(y)50 of HOP EXTRACT to Pseudokirchneriella subcapitata were
83.1mg/l and 52.4mg/l respectively (both determined by Maximum Likelihood-Logit).
The 0 to 72-hour NOEC(r) was 25mg/l and the 0-72 hour LOEC was 50mg/l (both determined by direct observation).
The 0 to 72-hour NOEC(y) was 12.5mg/l and the 0-72 hour LOEC was 25mg/l (both determined by direct observation).
The algal cells were examined microscopically during the determination of cell concentration.
All cells within the control and test concentrations appeared normal, no abnormalities were observed
(see section 3.2).
All validity criteria for the definitive test were met (see section 3.5).
The water quality measurements and incubation conditions are given in the summary tables in
Appendix 2 and were within accepted limits.
Analytical measurements of the freshly prepared exposure solutions indicated that the initial measured concentrations were not within 20% of nominal concentrations. In addition, analytical measurements of the 48 hour aged exposure solutions could not detect the test substance in the samples and therefore were also not within the ± 20% of nominal concentrations or ± 20% of the initial measured concentrations. This was expected due to the lack of water-solubility of HOP EXTRACT. All effect loading rates of the test substance are reported as nominal concentrations of the test substance.
Executive summary:

The study performed on hop extract is relevant for tetrahydroiso-alpha acids, since tetrahydroiso-alpha acids are derived from hop extract. A further study has been planned for iso-alpha acids and will be entered as an update.

Description of key information

Key value for chemical safety assessment

EC50 for freshwater algae:
42.7 mg/L
EC10 or NOEC for freshwater algae:
12.5 mg/L

Additional information

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