spirodiclofen (ISO);3-(2,4-dichlorophenyl)-2-oxo-1-oxaspiro[4.5]dec-3-en-4-yl 2,2-dimethylbutyrate

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

In-life initiated/completed: 12-Feb-1998 to 04-Dec-1998

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

This experimental study report is reliable for use in the risk assessment as it has been conducted by a trusted laboratory, under GLP and following OECD and EPA Guidelines relevant at the time of the study being conducted. There are no deviations from the OECD 203 Guideline in place at the time when the study was conducted, however there has since been an update to the OECD 203 Guideline in 2019. Despite this update, the data produced in this study is still deemed appropriate to use.

Qualifier:

according to guideline

Guideline:

EU Method C.1 (Acute Toxicity for Fish)

Version / remarks:

Previously known as 'EG C.1' in this study

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPP 72-1 (Fish Acute Toxicity Test)

Version / remarks:

Not specified

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Version / remarks:

Pre-2019

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Analytical determinations of the active substance concentrations were made in the test media on day 0, on day 2 and on day 4. Before taking the water samples, 10 mL acetonitrile were added to the sampling bottles to avoid an absorption of Spirodiclofen at the glass. The samples were analysed using the HPLC method. The water samples were directly injected into the HPLC. The quantification of Spirodiclofen was based on UV-detection. The limit of quantification was 0.01 mg/L.

Vehicle:

no

Details on test solutions:

The test concentration was set as limit test at the border of water solubility at a nominal concentration of 60.0 µg/L. In this flow-through test the stock solution was set up in acidified methanol (2.5% acetic acid). Slight acidification of methanol was required to minimize the degradation of Spirodiclofen in the stock solution, the pre-mixing vessels and in the aquaria. Seven days before the start of the test the aquaria were filled with the respective test medium by starting the water flow and the dosing system. At the start of the test, thirty fish were introduced into each aquarium in an order determined by a table of random numbers. During the test, fish were examined after four hours and then daily for mortalities and symptoms of intoxication.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

Test Organism common name: Rainbow Trout

All test fish were held in culture tanks on a 16/8 hour light/dark photoperiod and observed for at least 14 days prior to testing. Less than 3% mortality was noted prior to the test initiation and all unsuitable fish (e.g. injured, deformed, etc.) were eliminated from inclusion in the test prior to assignment to test groups. Fish were delivered on September 10, 1998. In the 48 hour acclimation period before testing less than 3 percent offish died.

Feed: During the acclimation period fish were fed a commercial trout diet. They were not fed 48 h before and during the study. During the 48 h acclimation period no fish died. The feed was not analyzed for unwanted contaminants.

Loading: In this test mean body wet weight of the fish at the beginning of the test was 1.9 + 0.4 g (Mean + SD), mean body standard length was 5.0 + 0.3 cm (Mean + SD). The biomass loading in the test medium was 0.24 g fish/L/d.

Test type:

flow-through

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

96 h

Hardness:

40 - 60 mg CaC03/L

Test temperature:

12.7°C - 13.0°C

pH:

6.5 - 7.3

Dissolved oxygen:

87 % - 99 %

Conductivity:

< 0.2 µS/cm

Nominal and measured concentrations:

60 µg/L nominal, 35.1 µg/L measured

Details on test conditions:

TEST SYSTEM:
- Glass aquaria of 32L x 36W x 38H cm. Test solution volume in the aquaria was 40 L.
- Aeration of the test system is not mentioned in the report.

REPLICATES:
- One replicate of thirty fish for each treatment level.

CONTROLS/TREATMENTS:
- Test design was a limit test; control, solvent control and 35.1 µg/L.
- The highest concentration was the practical limit of solubility.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Reconstituted water.

Reference substance (positive control):

no

Key result

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

>= 35.1 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

act. ingr.

Basis for effect:

other: No effects

Key result

Duration:

96 h

Dose descriptor:

LOEC

Effect conc.:

> 35.1 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

act. ingr.

Basis for effect:

not specified

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 35.1 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

act. ingr.

Basis for effect:

mortality (fish)

Details on results:

The LC50 (96h) of the test substance spirodiclofen (97.6 %) to rainbow trout (Oncorhynchus mykiss) in a 96-hour-limit test under flow-through conditions were determined to be > 35.1 µg/L (mean measured value). In this test one group of thirty fish was exposed at the border of solubility to a nominal (mean measured) concentration of 60.0 (35.1) µg/L. An additional group of thirty fish was exposed to the highest used solvent concentration (100 µL organic solvent/1 test water). A further control group of 30 fish was exposed to untreated test water. There were neither mortalities nor symptoms of intoxication in the control and in the solvent control group, respectively (table 1). The lowest lethal concentration (LLC) and the lowest-observed-effect-concentration (LOEC) were > 35.1 µg/L. The no-observed-effect-concentration (NOEC) was > 35.1 µg/L (table 1). All dosing systems (stock solutions > aquaria) functioned properly and the consumption of stock solutions was in accordance with the theoretical values. Spirodiclofen is stable in the stock solution with acidified methanol (2.5 % acetic acid), as used in this study. 100 µL methanol per liter dilution water (= 0.01 vol.-%) were used in this study as solvent carrier. In such a concentration methanol is not acute toxic to fish and well accepted by the test guidelines. Also, 100 µL acidified methanol per liter dilution water (= 0.01 voI.-% methanol and = 0.00025 vol.-% glacial acetic acid) did not produce any detrimental solvent effects in this study. Glacial acetic acid doesn't have an remarkable intrinsic toxicity to fish as shown by Yoshida & Nishiuchi (1976), but could act in higher concentrations via acidulation of the dilution water below pH values acceptable for fish. In the guidelines it is recommended to prefer test waters with pH values between 6.0 and 8.5, which was kept for all test levels.

Reported statistics and error estimates:

In the stock solution a mean measured value of 82% of nominal was detected. In test water a mean measured value of 58% of nominal was detected, based on analytical determination of spirodiclofen by HPLC. The discrepancy between the nominal and the measured concentration of spirodiclofen in water is caused by the border of its practical water solubility under test conditions and its tendency to adsorb easily to glass surfaces. All reported results are related to mean measured concentrations of spirodiclofen.

Validity criteria fulfilled:

yes

Conclusions:

There were no mortalities in any treatment level. The study was conducted as a limit test and
the highest concentration was at the limit of solubility in the test water (35.1 µg/L).

Executive summary:

In a 96-h acute toxicity study, rainbow trout (Oncorhynchus mykiss) were exposed to spirodiclofen technical at the practical limit of solubility in the test system. The study was a limit test. The treatments included a control, solvent control and the nominal concentration of 60 µg/L. The measured concentration was 35.1 µg/L under flow through conditions. The 96-h LC₅₀ was greater than 35.1 µg/L. There were no mortalities and no sublethal effects in any of the control or treated fish. Based on the results of this study, spirodiclofen technical would be classified as very highly toxic to rainbow trout in accordance with the classification system of the U.S. EPA. This classification is somewhat misleading in this case. The maximum solubility for spirodiclofen is less than 0.1 mg/L which automatically classifies the result as “very highly toxic” despite the lack of mortality and sublethal effects in this 96-hour fish study. This toxicity study is classified as acceptable and satisfies the guideline requirement for an acute fish (rainbow trout, Oncorhynchus mykiss) toxicity study.

Description of key information

In a 96-h acute toxicity study, rainbow trout (Oncorhynchus mykiss) were exposed to spirodiclofen technical at the practical limit of solubility in the test system. The study was a limit test. The treatments included a control, solvent control and the nominal concentration of 60 µg/L. The measured concentration was 35.1 µg/L under flow through conditions. The 96-h LC₅₀ was greater than 35.1 µg/L. There were no mortalities and no sublethal effects in any of the control or treated fish. Based on the results of this study, spirodiclofen technical would be classified as very highly toxic to rainbow trout in accordance with the classification system of the U.S. EPA. This classification is somewhat misleading in this case. The maximum solubility for spirodiclofen is less than 0.1 mg/L which automatically classifies the result as “very highly toxic” despite the lack of mortality and sublethal effects in this 96-hour fish study. This toxicity study is classified as acceptable and satisfies the guideline requirement for an acute fish (rainbow trout, Oncorhynchus mykiss) toxicity study.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Dose descriptor:

LC50

Remarks:

Limit of solubility

Effect concentration:

> 35.1 µg/L