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Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
48 hours
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Justification for type of information:
The study performed on hop extract is relevant for tetra acids, since hop extract may contain significant levels of these related hop extracts.
A further study has been planned for beta acids and will be entered as an update.
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
Batch 160025
Analytical monitoring:
yes
Vehicle:
no
Details on test solutions:
Media was stirred for 22 hours and 15 minutes and settled for 4 hours. After settling the first 100ml (approximately) of aqueous phase was removed (avoiding all settled and floating material) and discarded. The remaining aqueous phase provided sufficient volumes for water quality
measurements and testing.
Test organisms (species):
Daphnia magna
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
pH:
7.08 - 7.57
Dissolved oxygen:
6.17 - 7.31 mg/l
Nominal and measured concentrations:
Loading rates 0.1, 1.0, 10 and 100mg/l from stock solutions (WAF) used in preliminary study
Loading rates 1.0, 1.8, 3.2, 5.8 and 10.4mg/l were used in the main study
Reference substance (positive control):
yes
Remarks:
1.4 mg/l potassium dichromate in a separate GLP study
Key result
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
ca. 2.242 mg/L
Nominal / measured:
nominal
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 5.8 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (total fraction)
Basis for effect:
mobility

In range finder, 1 mg/l loading lead to no effect, but at 10 mg/l and 100 mg/l, there was 100% immobilisation

In main study, 2.42 or lower concentrations gave no adverse effects

A concentration of 5.8 mg/l resulted in 30% (6/20) immobilisation

A concentration of 10 mg/l resulted in 0% immobilisation (possibly due to partition effects from undissolved material)

Validity criteria fulfilled:
yes
Conclusions:
The 24-hour EC50 and 48-hour EC50 of HOP EXTRACT to Daphnia magna were >2.24mg/l and >2.24mg/l respectively (both determined by Linear Interpolation).
The 0 to 24-hour NOEC and LOEC were 2.242mg/l and >2.24mg/l respectively
The 0 to 48-hour NOEC and LOEC were 2.242mg/l and >2.24mg/l respectively
The Daphnia were examined at 24-hours and 48-hours for abnormal behaviour during the determination of immobility. All Daphnia appeared normal with no signs of abnormality
No test concentration immobilised 100% Daphnia and the highest concentration where no immobilisation occurred was 2.242mg/l.
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.

Higher treatment levels up to 10 mg/l were also tested, but at higher concentrations, there was a lower rate of immobilisation, perhaps due to partitioning of biologically active components into undissolved oils.

The water solubility has been hard to determine due to the multiple components in the substance; the biological effects seen in this study indicate that there is dissolved material present

Description of key information

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
5.8 mg/L

Additional information

Number for CSR. Results from endpoint show that the EC50 for 24 or 48 h was >5.8 mg/l.

Higher treatment levels up to 10 mg/l were also tested, but at higher concentrations, there was a lower rate of immobilisation, perhaps due to partitioning of biologically active components into undissolved oils.

The water solubility has been hard to determine due to the multiple components in the substance; the biological effects seen in this study indicate that there is dissolved material present