Diammonium hexachloroiridate

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:

23 Sept 2019 - 6 May 2020

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:

13 April 2014

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Version / remarks:

30 May 2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

purity:41.43 % Iridium

Analytical monitoring:

yes

Details on sampling:

The concentrations of iridium in the aqueous solutions were measured during the study.
Fresh samples were taken from all five test solutions and the control at the beginning of the test and at medium renewal at 24 hours prior to distribution to the test vessels. Samples of aged solutions were taken from one representative replicate at media renewal and test end.
Aged samples were filtered through a 0.22 μm PES (Polyethersulfonate) filter before sampling. Additionally, one set of aged samples were taken without filtration. However, these samples were not further analysed.
All samples were acidified and stored at 4 – 8 °C until analysis.

Vehicle:

no

Details on test solutions:

The highest test concentration was prepared by weighing in the appropriate amount of test item and transferring it to 500 mL dilution water.
The test medium was stirred for 24 hours at room temperature (about 20°C).
Since no undissolved test item was observed after 24 hours, the test medium was not ultrasonicated or filtered.
Afterwards, the test medium was diluted with test medium to obtain the lower test concentrations.

Test organisms (species):

Daphnia magna

Details on test organisms:

The test organisms were juvenile Daphnia magna, 4 – 24 hours old.
Origin of the cladocerans is the German Federal Environment Agency, Institut für Wasser-, Boden- und Lufthygiene.
Specimens used in the test were bred in the laboratory of the Fraunhofer IME.

Pre-Treatment:
Adult Daphnia, at least 3 weeks old, were separated from the stock population by sieving.
Batches of 30 to 50 animals were held at room temperature in ca. 1.8 L dilution water for one week. During this week the daphnids were fed daily with an algal suspension (Desmodesmus subspicatus) and ArtemioFluid (JBL). Algae growing in the log-phase were centrifuged and the pellet was re-suspended in a few mL of medium. 5 mL of this suspension was given to 1.8 L Daphnia medium.
The water was changed three times per week.
Newborn D. magna were separated by sieving, the first generation was discarded.
Individuals applied in the test were transferred with a bore Pasteur pipette a few hours after sieving to ensure applying only healthy specimens.

Test type:

semi-static

Water media type:

freshwater

Remarks:

Purified, Cu-reduced drinking water was used as holding- and dilution water.

Limit test:

no

Total exposure duration:

48 h

Hardness:

Hardness of the Cu-reduced water is below the recommended range. Therefore, it is enriched with an appropriate amount of CaCl2 to values of 250 – 350 mg CaCO3/L.

Test temperature:

19.1-19.4°C (19.2°C mean temperature)

pH:

7.66 - 8.10

Dissolved oxygen:

8.56 - 9.78 mg/L (97.9 – 111 % of air saturation)

Conductivity:

277 µS/cm

Nominal and measured concentrations:

Nominal concentrations:
range finding test: 1 -10 - 100 mg test item/L
definitive test: control - 0.316 - 1.00 - 3.16 - 10.0 - 31.6 mg test item/L (corresponding to control - 0.131 - 0.414 - 1.31 - 4.14 - 13.1 mg Ir/L)

Measured concentrations:
definitive test: Concentrations of freshly prepared test media showed recovery rates between 84.2 and 104 % of nominal concentrations.
Concentrations in aged test media showed recovery rates between 87.5 and 106 % of nominal concentrations and therefore remained stable with 92.0
to 110 % of initial concentrations.
The evaluation of effects was therefore based on the nominal concentrations

Details on test conditions:

light intensity: 869 lx (corresponding to 11.6 μE/(m² * s)) throughout the test
alkalinity: 1.6 mmol/L
total hardness: 1.2 mmol/L

Reference substance (positive control):

yes

Remarks:

K2Cr2O7 (latest 24h EC50 = 1.267 mg/L (95%CI: 1.056-1.609 mg/L)

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

3.51 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (dissolved fraction)

Remarks:

measured dissolved equals 80-120% of nominal

Basis for effect:

mobility

Remarks on result:

other:

Remarks:

95%CI: 2.41-5.13

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

1.46 mg/L

Nominal / measured:

nominal

Conc. based on:

element (dissolved fraction)

Remarks:

measured dissolved = within 80-120% of nominal added

Basis for effect:

mobility

Remarks on result:

other:

Remarks:

95%CI: 0.998-2.13

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

0.316 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (dissolved fraction)

Remarks:

measured dissolved = within 80-120% of nominal added

Basis for effect:

mobility

Details on results:

No significant signs of disease or stress like discoloration or abnormal behavior were observed in any replicate.

Results with reference substance (positive control):

latest 24h EC50 = 1.267 mg/L (95%CI: 1.056-1.609 mg/L)

Reported statistics and error estimates:

The evaluation of the concentration-effect-relationships and the calculations of effect concentrations was based on the nominal test item concentrations since the measured concentrations varied less than ± 20% of the nominal concentrations throughout the test.
The results showed inhibition of around 50 % and therefore were statistically analyzed to determine the EC50 and EC10 value together with 95 % confidence intervals using Probit analysis assuming log-normal distribution of the values.
The NOEC and LOEC values were determined using appropriate statistical methods (e.g. Fisher`s Exact Binomial Test for quantal response).
The computer program ToxRat was used for statistical evaluations.

nominal concentrations (mg test tem/L)	total introduced	mobile	immobile	% immobility
control	20	20	0	0
0.316	20	19	1	5
1.00	20	17	3	15
3.16	20	16	4	20
10	20	1	19	95
31.6	20	0	20	100

Validity criteria fulfilled:

yes

Remarks:

mortality in controls does not exceed 10 %, the dissolved oxygen concentration at the end of the test (48 h) ≥ 3 mg/L in control and test vessels.

Conclusions:

The short-term toxicity to Daphnia magna was determined according to OECD Guideline 202 (GLP compliant). The EC50 for immobility was calculated to 3.51 mg test item/L, corresponding to 1.46 mg Ir/L.

Executive summary:

A study was performed to investigate the short-term toxicity of Diammonium hexachloroiridate on the

mobility of Daphnia magna. The test was conducted under semi-static conditions over a

period of 48 hours with one media exchange after 24 hours. Effects on immobilization were

determined daily.

The daphnids were placed in water containing the test item in nominal concentrations of

0.316 to 31.6 mg test item/L, corresponding to 0.131 to 13.1 mg iridium/L. Iridium concentrations of freshly prepared test media and aged test media were determined and were within a range of 80 – 120 % of nominal concentrations

and remained stable during the test. Therefore, the evaluation of effects was based on the

nominal concentrations.

The test item had a statistically significant effect on the immobilization of the daphnids in the

four highest test concentrations. The EC50 was calculated to be 3.51 mg test item/L (1.46 mg Ir/L), the NOEC was set to 0.316 mg test item/L (0.131 mg Ir/L).

Description of key information

The EC50 for immobility of D. magna was 3.51 mg test item/L, corresponding to 1.46 mg Ir/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

3.51 mg/L

Additional information

The short-term toxicity to Daphnia magna was determined according to OECD Guideline 202 (GLP compliant). Measured dissolved concentrations were within 80 -120% of nominal added concentrations. The EC50 for immobility was calculated as 3.51 mg test item/L, corresponding to 1.46 mg Ir/L.