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Short-term toxicity to fish

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Reference
Endpoint:
short-term toxicity to fish
Type of information:
experimental study
Adequacy of study:
key study
Study period:
22 May 2017 - 9 November 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 203 (Fish, Acute Toxicity Test)
Qualifier:
according to guideline
Guideline:
EU Method C.1 (Acute Toxicity for Fish)
Qualifier:
according to guideline
Guideline:
other: The OECD Series on Testing and Assessment No. 23: Guidance document on aquatic toxicity testing of difficult substances and mixtures.
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
yes
Details on sampling:
- Water samples were taken from the control and each surviving test group at 0 and 72 hours from fresh media and at 24 and 96 hours from old media for quantitative analysis.
- Duplicate samples and samples at 24 (fresh media), 48 (old and fresh media) and 72 hours (old media) were taken and stored frozen for further analysis if necessary.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Due to the insolubility of the test item in test water, a saturated solution method of preparation was considered most appropriate.
- Stirring experiment: A nominal amount of test item (500 mg) was dispersed in 5 L of test water with the aid of vigorous magnetic stirring for 96 hours. After 3, 24 and 96 hours, the pH of the media was checked and a sample taken for chemical analysis after filtration through a 0.2 μm Gelman Acrocap filter (initial 100 mL discarded).
- The results of the stirring experiment indicated that a 3-hour stirring period was appropriate.
- The nominal test concentrations in the combined range finder-limit test were 1.0, 10 and 100% v/v saturated solutions. The 100% v/v saturated solution was prepared in a similar way as described for the stirring experiment (2250 mg test item in 22.5 L test water, 3 h stirring, 0.2-µm filtered using a Gelman Acrocap filter). The 1.0 and 10% v/v saturated solutions were then prepared through serial dilution of the 100% saturated solution.
Test organisms (species):
Oncorhynchus mykiss (previous name: Salmo gairdneri)
Details on test organisms:
TEST ORGANISM
- Common name: Rainbow trout
- Source: Brow Well Fisheries Limited, Hebden, near Skipton, Yorkshire, UK
- Length at the end of the combined range finder-limit test (length definition, mean, range and SD): mean: 4.3 cm; SD: 0.26
- Weight at study initiation (mean and range, SD): mean: 0.77 g; SD: 0.13
- Feeding during test: no

ACCLIMATION
- Acclimation period: 8 days before the test
- Acclimation conditions (same as test or not): yes, same as test
- Type and amount of food: commercial trout pellets (discontinued 24 h before start of the test)
- Feeding frequency: daily
- Health during acclimation (any mortality observed): no mortality in the seven days prior to the start of the test
Test type:
semi-static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
96 h
Hardness:
140 mg/L as CaCO3
Test temperature:
14-16°C
pH:
t=0h (fresh media): 7.5-7.7
t=24h (old media): 7.6-7.9
t=24h (fresh media): 7.7-7.9
t=48h (old media): 7.7-8.1
t=48h (fresh media): 7.9-8.0
t=72h (old media): 7.5-8.0
t=72h (fresh media): 7.6-8.0
t=96h (old media): 8.2
Dissolved oxygen:
t=0h (fresh media): 9.6-9.8
t=24h (old media): 8.9-9.6
t=24h (fresh media): 9.4-9.6
t=48h (old media): 9.3-9.8
t=48h (fresh media): 9.4-9.5
t=72h (old media): 9.1-9.7
t=72h (fresh media): 9.3-9.5
t=96h (old media): 9.4-9.8
Salinity:
not applicable
Conductivity:
345 μS/cm at 20°C (dilution water)
Nominal and measured concentrations:
Combined range finder limit test:
- Nominal concentrations: Control, 1.0, 10 and 100% v/v of a saturated solution (SS) with nominal loading rate of 100 mg/L (as Yb2O3)
- Measured concentrations at t=0h (fresh): < LOQ, < LOQ, 0.000112, 0.000916 mg/L Yb; < LOQ, < LOQ, 0.000128, 0.00105 mg/L test item
- Measured concentrations at t=24h (old): < LOQ, < LOQ, 0.000094, 0.000795 mg/L Yb; < LOQ, < LOQ, 0.000107, 0.000909 mg/L test item
- Measured concentrations at t=72h (fresh): < LOQ, < LOQ, 0.000189, 0.00171 mg/L Yb; < LOQ, < LOQ, 0.000216, 0.00196 mg/L test item
- Measured concentrations at t=96h (old): < LOQ, < LOQ, 0.000162, 0.00154 mg/L Yb; < LOQ, < LOQ, 0.000185, 0.00176 mg/L test item
Details on test conditions:
TEST SYSTEM
- Test vessel: aquaria
- Material, size, headspace, fill volume: 25-30-L glass aquaria, filled with 20 L test solution, covered to reduce evaporation
- Aeration: yes, via narrow bore glass tubes
- No. of organisms per vessel: 7 (control and 100% v/v SS); 3 (1.0 and 10% v/v SS)
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1
- Biomass loading rate: 0.27 g fish/L

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Laboratory tap water, dechlorinated by passage through an activated carbon filter (Purite Series 500) and partly softened (Elga Nimbus 1248D Duplex Water Softener) giving water with a total hardness of approximately 140 mg/L as CaCO3.
- Culture medium different from test medium: no
- Intervals of water quality measurement: water temperature, dissolved oxygen and pH were recorded daily in fresh and old test media

OTHER TEST CONDITIONS
- Photoperiod: 16 h light and 8 h dark, with 20-min transition periods to mimic dusk and dawn transition periods

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Fish were considered to be dead when no reaction was observed after touching the caudal peduncle and visible breathing movements were absent. Mortality checks were performed after 1, 3, 6, 24, 48, 72 and 96 h.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 10 (combined range finder-limit test)
- Range finding study: yes, the study was a combined range finder-limit test as no (adverse) effects were expected
- Test concentrations: 1.0, 10 and 100% of a saturated solution with nominal loading rate of 100 mg/L (test item)
- Results used to determine the conditions for the definitive study: no (the test was a combined range finder-limit test)
Reference substance (positive control):
not specified
Key result
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
> 100 other: % v/v of a saturated solution with nominal loading rate of 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality (fish)
Details on results:
No mortality was observed in any of the test solutions.
The 96-h LC50 was therefore > 100% v/v of a saturated solution with nominal loading rate of 100 mg/L.
The mean measured dissolved Yb concentration in the 100% v/v saturated solution was 0.0013 mg Yb/L (i.e. 0.0015 mg Yb2O3)/L).
Sublethal effects: Swimming at the bottom was detected in the 100% v/v saturated solution in 2/7 fish after 6 h and 3/7 fish after 24 h but disappeared later on. Swimming at the bottom was observed in the 100% v/v saturated solution in 3/7 fish but disappeared towards the end of the test.
Reported statistics and error estimates:
No statistics applied.
Validity criteria fulfilled:
yes
Conclusions:
The acute toxicity of ytterbium oxide to juvenile rainbow trout was investigated in accordance with OECD guideline 203 and GLP. A semi-static combined range finder-limit test was performed, in which no adverse effects were observed up to and including at the highest concentration tested (i.e., a 100% v/v saturated solution with nominal loading rate 100 mg/L). The 96-h LC50 was therefore > 100% v/v of a saturated solution with nominal loading rate 100 mg/L. The mean measured dissolved Yb concentration in this saturated solution was 0.0013 mg Yb/L (corresponding to 0.0015 mg Yb2O3/L).

Description of key information

The acute toxicity of diytterbium trioxide to juvenile rainbow trout (Oncorhynchus mykiss) was determined in a 96-hour semi-static test with a daily medium renewal, performed according to OECD Guideline 203 and conform GLP requirements (Ablitt, 2017; Klimisch 1). In this study, fish were exposed in a combined range finder limit test to blank medium or to 1.0, 10 or 100% v/v dilutions of a saturated solution with nominal loading rate of 100 mg/L (as ytterbium oxide). No mortality was observed during the test. The 96-h LC50 of diytterbium trioxide to rainbow trout was therefore > 100% v/v of a saturated solution with nominal loading rate of 100 mg Yb2O3/L. Based on the results of this study, diytterbium trioxide can be concluded to be non-harmful to fish. The study of Ablitt (2017) was considered as key study for endpoint coverage.

Key value for chemical safety assessment

Additional information