Zinc isodecyl phosphorodithioate

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:

24th November 2017 - 2nd March 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Version / remarks:

1992

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: All test concentrations and the control
- Sampling method: 2.0 mL from the approximate centre of the test vessels taken at the start of the test and after 72 hours from freshly prepared solutions and at the first renewal (24 hours) and end of the test for 24-hour old solutions
- Sample storage conditions before analysis: None, samples were analysed on the day of sampling

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Test solutions were individually prepared loading rates. A three-day period of magnetic stirring was applied to accelerate dissolution of the test item in medium. The obtained mixtures were allowed to settle for a period of approximately one hour. Thereafter, the aqueous Water Accommodated Fractions (WAFs) were collected through glass wool and used as test concentrations.
- Controls: Test medium without test item
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): None
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): All test solutions were clear and colorless at the end of the preparation procedure.

Test organisms (species):

Cyprinus carpio

Details on test organisms:

TEST ORGANISM
- Common name: Carp (Cyprinus carpio, Teleostei, Cyprinidae) Linnaeus, 1758
- Source: Zodiac, proefacc, "De Haar Vissen", Wageningen University and Research Centre, The Netherlands
- Length at study initiation (length definition, mean, range and SD): 2.3 ± 0.1 cm
- Weight at study initiation (mean and range, SD): 0.20 ± 0.04 g
- Characteristics: F1 from a single parent-pair bred in UV-treated water


ACCLIMATION
- Acclimation period: At least 12 days after delivery
- Acclimation conditions (same as test or not): Same as test (adjusted ISO medium)
- Type and amount of food during acclimation: Fed with pelleted fish food
- Feeding frequency during acclimation: Daily
- Health during acclimation (any mortality observed): In the batch of fish used for the test, mortality during the seven days prior to the start of the test was less than 5%.


FEEDING DURING TEST
- No feeding from 24 hours prior to the test and during the total test period

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

180 mg CaCO3/L

Test temperature:

21 - 22°C

pH:

7.4 - 7.9

Dissolved oxygen:

6.5 - 9.7 mg/L

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal: 4.6, 10, 22, 46, 100 mg/L
Measured (test start): 0.027, 0.10, 0.15, 0.11, 0.092 mg/L
Measured (72 hours, fresh): 0.069, 0.13, 0.19, 0.50, 0.32 mg/L
Measured (24 hours, aged): 0.017, 0.059, 0.11, 0.067, 0.053 mg/L
Measured (96 hours aged): 0.048, 0.10, 0.14, 0.47, 0.22 mg/L
Mean measured: 0.039, 0.097, 0.15, 0.28, 0.17 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 3.2 litre vessels
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: All-glass, silanised (to prevent adsorption of the test item to glass), containing 3 litres of test solution
- Aeration: None
- Type of flow-through (e.g. peristaltic or proportional diluter): Not applicable
- Renewal rate of test solution: Daily renewal
- No. of organisms per vessel: 7
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1
- No. of vessels per vehicle control (replicates): Not applicable
- Biomass loading rate: 0.47 g fish/L

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Adjusted ISO medium
- Culture medium different from test medium: No
- Intervals of water quality measurement: Dissolved oxygen, pH and temperature measured daily in all vessels with surviving fish

OTHER TEST CONDITIONS
- Adjustment of pH: None
- Photoperiod: 16 hours

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Mortality assessed at 2 1/4, 24, 48, 72 and 96 hours

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2.2
- Justification for using less concentrations than requested by guideline: Not applicable
- Range finding study : Yes
- Test concentrations: 1, 10 and 100 mg/L
- Results used to determine the conditions for the definitive study: Yes. The result of the full test were not in line with the results of the range-finding test, as in the latter all fish exposed to the highest group did not survive the exposure. The reason behind this is unknown. However, all average exposure concentrations tested in the full test were above the water solubility of the test item and some of them were higher than the highest concentration measured in the range-finding test. Therefore it is justified to base the effect of the test item on the results of the full test.

Reference substance (positive control):

yes

Remarks:

pentachlorophenol

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 0.28 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Remarks on result:

other: LC50 was above the limit of solubility of the test item

Results with reference substance (positive control):

Tested at concentrations of 0.1, 0.22 and 0.46 mg/L, 13 - 17 February 2017
96-hour LC50: 0.32 mg/L (95% confidence interval: 0.22 - 0.46 mg/L)
Historical range: 0. 1 - 0.46 mg/L (April 1988 - present)

Reported statistics and error estimates:

No LC50 could be calculated because the test item proved to be non-toxic (LC50 > maximum soluble concentration).

Sublethal observations / clinical signs:

Table 1 Incidence of Mortality and Total Mortality During the Final Test

Test item Average Exposure Concentration (mg/L)	Initial number of fish	Cumulative mortality					Total Mortality (%)
		2¼h	24h	48h	72h	96h
Control	7	0	0	0	0	0	0
0.039	7	0	0	0	0	0	0
0.097	7	0	0	0	0	0	0
0.15	7	0	0	0	0	0	0
0.28	7	0	0	0	0	0	0
0.17	7	0	0	0	0	0	0

Table 2 Average Exposure Concentration Versus Nominal Concentration of the Final Test

Test item Loading rate (mg/L)	Measured concentration (mg/L)				Average Exposure Concentration (mg/L)
	t=0h (fresh)	t=24h (old)	t=72h (fresh)	t=96 (old)
4.6	0.027	0.017	0.069	0.048	0.039
10	0.10	0.059	0.13	0.10	0.097
22	0.15	0.11	0.19	0.14	0.15
46	0.11	0.067	0.50	0.47	0.28
100	0.092	0.053	0.32	0.22	0.17

Table 3 Incidence of Mortality and Total Mortality During the Range-Finding Test

Test item WAF loading rate (mg/L)	Initial number of fish	Cumulative mortality					Total Mortality (%)
		2¼h	24h	48h	72h	96h
1.0	3	0	0	0	0	0	0
10	3	0	0	0	0	0	0
100	3	0	3	3	3	3	100

Table 4 Average Exposure Concentration Versus Nominal Loading rates of the Range-Finding Test

Test item WAF Loading rate (mg/L)	Measured concentration (mg/L)			Average exposure concentrations (mg/L)
	t=0h	t=24h	t=96
1.0	0.041	0.016	0.010	0.016
10	0.19	0.12	0.074	0.11
100	0.20	0.14	0.12	0.14

Validity criteria fulfilled:

yes

Remarks:

No mortality observed in control at end of test; test conditions maintained constant throughout the test; dissolved oxygen >60% air saturation throughout test; results based on mean measured as deviated from nominal by >20%

Conclusions:

The 96-hour LC50 value for the test item was determined to be >0.28 mg/L (based on measured concentrations), considered to be the limit of solubility for the test item in test medium.

Executive summary:

Tobor-Kaplon (2018) is a GLP-compliant study following OECD guideline 203, with Cyprinus carpio. Following the OECD guidance on difficult to test substances the test solutions were individually prepared as water accommodated fractions (WAF) at loading rates of 4.6, 10, 22, 46 and 100 mg/L. Tests solutions were renewed daily and after 24 hours of exposure the measured

test item concentrations were at the level of 58 – 76% of initial. A similar decrease was observed in the 24-hour old solutions at the end of the test (69 – 75% of initial in old solutions), except for the WAF prepared at a loading rate of 46 mg/L, which was at 95% of initial. Mean measured concentrations were determined to be 0.039, 0.097, 0.15, 0.28 and 0.17 mg/L and results were reported based on these mean measured concentrations. 7 fish were tested per test concentration and for the untreated control and mortality was assessed after 2 1/4, 24, 48, 72 and 96 hours. All validity criteria for the study were met. The 96 -hour LC50 was determined to be >0.28 mg/L (based on measured concentrations), considered to be the limit of solubility for the test item in test medium.

The results of the full test were not in line with the results of the range-finding test, as in the latter all fish exposed to the highest group did not survive the exposure. The reason behind this is unknown. However, all average exposure concentrations tested in the full test were above the water solubility of the test item and some of them were higher than the highest concentration measured in the range-finding test. Therefore it is justified to base the effect of the test item on the results of the full test.

Description of key information

The 96-hour LC50 value for the test item was determined to be >0.28 mg/L (based on measured concentrations), considered to be the limit of solubility for the test item in test medium.

Additional information

Tobor-Kaplon (2018) is a GLP-compliant study following OECD guideline 203, with Cyprinus carpio. Following the OECD guidance on difficult to test substances the test solutions were individually prepared as water accommodated fractions (WAF) at loading rates of 4.6, 10, 22, 46 and 100 mg/L. Tests solutions were renewed daily and after 24 hours of exposure the measured test item concentrations were at the level of 58 – 76% of initial. A similar decrease was observed in the 24-hour old solutions at the end of the test (69 – 75% of initial in old solutions), except for the WAF prepared at a loading rate of 46 mg/L, which was at 95% of initial.Mean measured concentrations were determined to be 0.039, 0.097, 0.15, 0.28 and 0.17 mg/L and results were reported based on these mean measured concentrations. 7 fish were tested per test concentration and for the untreated control and mortality was assessed after 2 1/4, 24, 48, 72 and 96 hours. All validity criteria for the study were met. The 96 -hour LC50 was determined to be >0.28 mg/L (based on measured concentrations), considered to be the limit of solubility for the test item in test medium.

The results of the full test were not in line with the results of the range-finding test, as in the latter all fish exposed to the highest group did not survive the exposure. The reason behind this is unknown. However, all average exposure concentrations tested in the full test were above the water solubility of the test item and some of them were higher than the highest concentration measured in the range-finding test. Therefore it is justified to base the effect of the test item on the results of the full test.