Ethyltriphenylphosphonium iodide

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2003-03-18 to 2003-10-17

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Version / remarks:

adopted April 4, 1984

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Version / remarks:

Publication No. L383, December 1992

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

During the final test duplicate samples for analysis were taken from the blank-control and 0.32, 1 .0 and 5.6 mg/L.
Sampling:
Frequency: at t=0h and t=48h.
Volume: 10 mL from the approximate centre of the test vessel
Storage: The samples not analysed on the day of sampling were stored in a freezer.

Vehicle:

yes

Details on test solutions:

Preparation of test solutions considering OECD Guidance document on aquatic toxicity testing of difficult substances and mixtures, OECD series on testing and assessment number 23, December 14, 2000, started with a stock at 100 mg/L. ln the final test, the test substance was weighed under darkness. The stock solution was treated with ultrasonic waves for 5-15 minutes, after which it was a clear and colourless solution (first EC50 test and final test) or containing slight precipitation and a floating layer (range-finding test only). The stock (or the clear part of the stock, without precipitate and floating layer in the range-finding test) was diluted in test medium to reach the lower test concentrations. All final solutions were clear and colourless.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: water flea
- Strain: Daphnia magna (Crustacea, Cladocera) (Straus, 1820), at least third generation, obtained by acyclical parthenogenesis under specified breeding conditions.
- Validity of batch: Daphnids originated from a healthy stock, 2nd to 5th brood, showing no signs of stress such as mortality >20%, presence of males, ephippia or discoloured animals and there was no delay in the production of the first brood.
- Characteristics: For the test selection of young daphnia with an age of < 24 hours, from parental daphnids of more than two weeks old.

BREEDING
- Start of each batch: With newborn daphnids, i.e. less than 3 days old, by placing about 250 of them into 10 litres of medium in an all-glass culture vessel.
- Maximum age of the cultures: 4 weeks
- Renewal of the cultures: After 7 days of cultivation half of the medium twice a week.
- Temperature of medium: 18-22°C
- Feeding: Daily, a suspension of fresh water algae.
- Medium: M7, as prescribed by Dr. Elendt-Schneider (Elendt, B.-P., 1990: Selenium deficiency in Crustacea. An ultrastructural approach to antennal damage in Daphnia magna Straus. Protoplasma 154, 25-33).

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

250 mg/L expressed as CaCO3

Test temperature:

19.5-20.8 °C

pH:

8.0 ± 0.2 after aeration

Dissolved oxygen:

8.6-8.7

Nominal and measured concentrations:

nominal 0.32, 0.56, 1.0, 1.8, 3.2 and 5.6 mg/L

Details on test conditions:

TEST PROCEDURE AND CONDITIONS:
Test duration: 48 hours
Test type: Static
Test vessels: 100 mL, all-glass
Medium: ISO
Number of daphnia: 20 per concentration
Loading: 5 per vessel containing 80 mL medium
Light: 16 hours photoperiod daily
Feeding: No feeding
Aeration: No aeration of the test solutions
lntroduction of daphnia: Within 1 1/2 hours after preparation of the test solutions
MEASUREMENTS AND RECORDINGS:
lmmobility (including mortality): At 24 hours and at 48 hours
pH: At the beginning and at the end of the test, for all concentrations and the control
Dissolved oxygen: At the beginning and at the end of the test, for all concentrations and the control
Temperature of medium: Continuously in a temperature control vessel, beginning at the start of the test

COMBINED LIMIT/RANGE-FINDING TEST
The project started with a combined limit/range-finding test. Twenty daphnids per concentration were exposed to 100 mg/L and a blank-control in the limit test, while ten daphnids per concentration were exposed to 0.1,1.0 and10 mg/L in the combined range-finding test. Samples for analysis were taken at the start and the end of the test. Further conditions were comparable to those in the final test.

FIRST TEST
Based on the results of the range-finding test, the first EC50 test was performed exposing 20 daphnia per concentration to a blank-control and 1.0, 1.8, 3.2, 5.6 and 10 mg/L. Oxygen was measured in all concentrations and the blank-control at the start of the test, and at 10 mg/L after 24 hours of exposure. Oxygen was not measured at the end of the test. pH was measured in all concentrations and the blank-control at the start of the test and only in the blank-control at the end of the test. Samples for analysis were taken at the start of the exposure period.

FINAL TEST
No precipitation was observed throughout the test. The responses were somewhat higher than expected based on the range-finding test. In correspondence with the range-finding test, all daphnids had become immobilised at 10 mg/L. Contrary to the results of the combined limit/range-finding, 35% of the daphnids exposed to 1.0 mg/L were immobile at the end of the test. Therefore, a final test was performed with 0.32, 0.56, 1.0, 1.8, 3.2 and 5.6 mg/L.

CALCULATION of EC50
The EC50-value was calculated at 24 and 48 hours of exposure from the probits of the percentages of affected daphnia and the logarithms of the corresponding test substance concentrations using the maximum likelihood estimation method (Finney, D.J., 1971: Probit analysis, Cambridge University Press, Cambridge, U.K., 3rd edition).

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

0.32 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

1.9 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 95% confidence interval: 1.4 to 2.7 mg/L

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

0.86 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 95% confidence interval: 0.57 to 1.2 mg/L

Details on results:

Combined limit/range-finding test:
After 24 hours of exposure all organisms exposed to 10 and 100 mg/L became immobilised, while no immobilisation was observed at lower concentrations. The EC50 was expected to be between 1.0 and 10 mg/L.

First EC50 test:
No precipitation was observed throughout the test. The responses were somewhat higher than expected based on the range-finding test. In correspondence with the range-finding test, all daphnids had become immobilised at 10 mg/L. Contrary to the results of the combined limit/range-finding, 35% of the daphnids exposed to 1.0 mg/L were immobile at the end of the test. Therefore, a final test was performed with a lower concentration range.

Final test:
The responses recorded in this test allowed for determination of an EC50. The mean of the responses recorded at 1.0, 1.8, 3.2 and 5.6 mg/L were in agreement with the results of the first EC50 test. No precipitation was observed. Measured initial concentrations were in agreement with nominal (100-104%). These concentrations remained stable throughout the test. Therefore, results were based on nominal concentrations. pH and oxygen concentrations (mg/L) remained within the limits prescribed by the protocol (pH: 6.0-8.5, not varying more than 1 unit; oxygen: >7 and >=5 mg/L at the start and the end of the test, respectively).
The temperature of the test medium measured in the blank-control varied from 19.5 to 20.8°C.

The test item did not induce acute significant immobilisation of Daphnia magna at 0.32 mg/L after 48 hours of exposure (NOEC).
The 24h-EC50 was 1.9 mg/L based on nominal concentrations (95% confidence interval 1.4 and 2.7 mg/L).
The 48h-EC50 was 0.86 mg/L based on nominal concentrations (95% confidence interval 0.57 and 1.2 mg/L).

ACCEPTABILITY OF THE TEST
1. In the control, no daphnia became immobilised or trapped at the surface of the water.
2. The oxygen concentration was > 5 mg/L at the end of the test. Other test conditions (pH and temperature) were maintained within the limits prescribed by the protocol and the guidelines.
3. The 24h-EC50 (based on the initial concentration) of potassium dichromate was within the range 0.6 mg/L to 1.7 mg/L.

Results with reference substance (positive control):

The 24h-EC50 (based on the initial concentration) of potassium dichromate was within the range 0.6 mg/L to 1.7 mg/L.

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of the present study Ethyltriphenylphosphonium iodide did not induce immobilisation of Daphnia magna at 0.32 mg/L after 48 hours of exposure (NOEC).
The 24h-EC50 was 1.9 mg/L based on nominal concentrations (95% confidence interval 1.4 and 2.7 mg/L).
The 48h-EC50 was 0.86 mg/L based on nominal concentrations (95% confidence interval 0.57 and 1.2 mg/L).

Description of key information

48h-EC50 Daphnia magna: 0.86 mg/L (OECD 202/EU C.2, GLP)

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

0.86 mg/L

Additional information

The 48-hr-acute toxicity of test item Ethyltriphenylphosphonium iodide to Daphnia magna was studied under static conditions according to OECD Guideline 202 (1984) and EU method C.2 (1992). Daphnids were exposed to control and test chemical at nominal concentrations of 0.32, 0.56, 1.0, 1.8, 3.2 and 5.6 mg/L. The test was performed in quadruplicate with 5 daphnia per vessel. Samples for analysis were taken at the start and the end of the test. Analysis of the samples taken during the final test showed that the measured concentrations were in agreement with nominal throughout the test period (100-104%). The study met the acceptability criteria described in the protocol and was considered valid.

The 24h-EC50 was 1.9 mg/L based on nominal concentrations (95% confidence interval 1.4 and 2.7 mg/L).

The 48h-EC50 was 0.86 mg/L based on nominal concentrations (95% confidence interval 0.57 and 1.2 mg/L).

Ethyltriphenylphosphonium iodide did not induce acute significant immobilisation of Daphnia magna at 0.32 mg/L after 48 hours of exposure (NOEC).