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Ecotoxicological information

Short-term toxicity to fish

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Link to relevant study record(s)

Reference
Endpoint:
short-term toxicity to fish
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
Qualifier:
according to guideline
Guideline:
OECD Guideline 203 (Fish, Acute Toxicity Test)
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
25.0 mL water samples were taken at the middle of the aquarium in control and treatment groups at 0, 24h, 48h, 72h and 96h in fresh and aged medium. 25 mL collected water samples were extracted with 25 mL n-hexane by shaking for 5 min, and then allowed to stand for I min. The upper organic phases were filtrated by 0.22 μm millipore membrane, then the filtrates were analysed by GC/MS.
Vehicle:
no
Details on test solutions:
WAFs (water accommodated fractions) solutions were prepared by adding appropriate amount of the test substance to the test medium in glass aspirator bottles with appropriate size. The mixing aspirator bottle was stoppered and the aqueous test substance mixture was stirred for 24 hrs on a magnetic stirplate and a teflon stirbar at room temperature (about 23 °C ~ 25°C). The vortex height was set at least 10% of the static liquid height. At the end of the 24 h, stirring was stopped and the test
substance was allowed to settle down. The mixture was allowed to settle for I hour at room temperature. The undissolved test substances in 1 0 mg/L W AFs and 100 mg/L W AFs solution were floating on the surface of the test solution. Then the aqueous portion removed through the outlet of the aspirator stirring bottle was the W AFs solutions of the test substance without further filtration to remove the remaining undissolved test substance.
Test organisms (species):
other: Gobiocypris rarus
Details on test organisms:
TEST ORGANISM
- Common name: Rare minnow
- Source: in-house culture (Batch F20180715G)
- Measurements at study initiation: The average wet-weight and the length of the fish used in the limit test was 0.232 g and 2.40 cm, with the relative standard deviation (RSD) of 4.83% and 4.11 %, respectively

ACCLIMATION
- Acclimation period: Fish to be used in the test were held for 7 days in water of the quality and temperature to be used in the test. A photoperiod of I 6 hours light, provided by overhead fluorescent tubes, and 8 hours dark was maintained. Water quality was the same with the test water. The oxygen concentration was more than 80% of the air saturation value. And the temperature was controlled between 22.8°C and 23.4°C.
- Type and amount of food during acclimation: The fish were fed twice daily during the holding period on proprietary fish food. They were held without food for approximately 24 hours before being placed into the test vessels.
- Health during acclimation (any mortality observed): No mortality observed.

Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h
Hardness:
125 to 136 mg (CaCO3)/L
Test temperature:
23.0°C to 23.1°C
pH:
7.68 - 7.87
Dissolved oxygen:
87% - 97% of the air saturation
Nominal and measured concentrations:
The measured concentrations of 10, 20, 40, 60, 80 and 100 mg/L W AFs test solution were 0.58, 1.13, 2.16, 3.33, 4.72 and 5.60 mg/L, respectively. The results indicated that concentration of test substance was stable ( deviation within 20%) in the water during the test period.
Details on test conditions:
TEST SYSTEM
- Aeration: No
- Renewal rate of test solution: Daily
- Biomass loading rate: 0.7 g to 0.9 g fish (wet weight) per litre of test medium

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Photoperiod: 12h daily

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
At 3, 6, 24, 48, 72 and 96 h, the mortalities of the fish were recorded, and observations on individual behaviour were performed.

TEST CONCENTRATIONS
- Test concentrations: 10, 20, 40, 60, 80 and 100 mg/L (loading rates)
- Range finding study
- Test concentrations: 1, 10 and 100 mg/l
Reference substance (positive control):
yes
Remarks:
Potassium Dichromate
Key result
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
2.02 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
mortality (fish)
Details on results:
During the test period, all fish in the control and treatment of 10 mg/L WAFs test solution were alive and appeared nonnal. Effects (Fish lying on side or back) occurred at concentrations of 20 mg/L WAFs test solution and above. All Fish were dead after 96 h-exposure at concentration of 80 mg/L WAFs test solution.
Sublethal observations / clinical signs:

Mortality during the Definitive Test

Nominal concentration WAF [mg/l]    Measured concentration [mg/l]     Initial number of fish     Number of dead fish               
 3h  6h  24h  48h  72h 96h 
0 (Control) not detected 10
10 3.15 10 
20 6.57 10 
40 10.0  10
60  13.0  10 
80 22.2  10  10  10  10  10 
100 31.5  10  10  10  10  10  10 
LL50 (95% CI) [mg/l]                    36.5 (30.4 -43.8)
LC50 (95% CI) [mg/l]                    2.02 (1.68 -2.42) 
Validity criteria fulfilled:
yes
Conclusions:
The results showed that under valid semi-static test conditions (24 h renewal), the 96 h-LC50 of the test substance to fish (Rare minnow, Gobiocypris rarus) was 2.02 mg/L, 95% CJ 1.68-2.42 mg/L (based on measured concentration).
Executive summary:

Under semi-static conditions (24h renewal), the acute toxicity of test substance dihexyl ether to Rare minnow (Gobiocypris rarus) was conducted according to Procedure 203 of the "Guidelines for Testing of Chemicals" of the OECD: "Fish, Acute Toxicity Test" (I 992).

A range-finding test and then a definitive test were performed respectively. Nominal concentrations of 1.00, 10.0 and 100 mg/L W AFs test solutions were used in the range-finding test, and the nominal concentrations of 10, 20, 40, 60, 80 and 100 mg/L WAFs test solutions were used in the definitive test. Concentrations of the test substance were quantified using GC/MS.

The mean measured concentrations of the test substance were 0.58, 1.13, 2.16, 3.33, 4.72 and 5.60 mg/L, respectively.

In the range-finding test, 5 fish per treatment and no replicates were used. And 10 fish per treatment and a single replicate were used in the definitive test. The test fish were exposed for 96 hours to the test solution.

During the test period, the pH values of the control mediums and test mediums were between 7.68 and 7.87, the Dissolved Oxygen (DO) values varied from 87% ~ 97% of the air saturation at the test temperature, the temperature of the test mediums were maintained in the range of 23.0°C to 23.1 °C, and the total hardness was in the range of 125 mg (CaCO3)/L to 136 mg (CaCO3)/L.

During the test period, all fish in the control and treatment of 10 mg/L WAFs test solution were alive and appeared normal. Effects (Fish lying on side or back) occurred at concentrations of20 mg/L WAFs test solution and above. All Fish were dead after 96 h-exposure at concentration of 80 mg/L WAFs test solution. The results showed that under valid semi-static test conditions (24 h renewal), the 96 h-LL50 of the test substance to fish (Rare minnow, Gobiocypris rarus) was 36.5 mg/L WAFs, with 95% confidence limit of 30.4--43.8 mg/L WAFs. Based on the measured concentration, the 96 h-LC50 was 2.02 mg/L, with 95% confidence limit of 1.68-2.42 mg/L. The maximum loading level causing no mortality (96 h-LL0) was 20 mg/L WAFs (mean measured concentration I. 13 mg/L).

The minimum loading level causing 100% mortality (96 h-LL100) was 80 mg/L W AFs (mean measured concentration 4.72 mg/L), i.e.:

96 h-LL50= 36.5 mg/L WAFs, 95% CI 30.4~43.8 mg/L WAFs (based on the nominal concentration);

96 h-LC5o = 2.02 mg/L, 95% CI 1.68~2.42 mg/L (based on measured concentration);

96 h-LL0 = 20 mg/L WAFs (mean measured concentration 1.13 mg/L);

96 h-LL100 = 80 mg/L W AFs (mean measured concentration 4.72 mg/L).

Description of key information

The acute aquatic toxicity of dihexyl ether towards fish was determined in an OECD 203 study with Gobiocypris rarus, resultung in an LC50(96)=2.02 mg/l.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish
Effect concentration:
2.02 mg/L

Additional information

A reliable QSAR model (Ecological Structure-Activity Relationship (ECOSAR) version 1.11) was used to predict the acute toxicity of dihexyl ether to fish and is provided as supporting information. The 96 hour LC50 was 0.324 mg/L for the neutral organic class. This results shows the conservativeness of the model assumptions.