Dicarbonyl(pentane-2,4-dionato-O,O')rhodium

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:

31 Oct 2019 - 17 March 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: 40.0% Rhodium

Analytical monitoring:

yes

Details on sampling:

The concentrations of rhodium in the aqueous solutions was 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.
Samples were filtered through a 0.22 μm PES filter before measurement. All samples were
measured within 24 hours after sampling.

Vehicle:

no

Details on test solutions:

The highest test concentration was prepared by weighing in 99.8 mg (d-1) and 100.2 mg (d1)
of the test item and transferring it to 1000 mL test medium.
The test media was stirred for 24 hours at room temperature (about 20°C).
After stirring, undissolved yellow-brownish test item was still observed. Therefore, the test
media was first ultra sonicated for 30 minutes followed by filtration through a 0.22 μm PES
filter to remove the undissolved test item. After filtration no undissolved test item was left,
however, the test solutions with concentrations higher than 30.9 mg test item (nominal) were
clear but slightly yellowish colored.
The test solution was subsequently diluted to obtain the lower test concentrations.
In addition, a control was prepared in the same way as the test solutions with dilution water
only.

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:

18.9-19.5°C (19.3°C mean temperature)

pH:

7.32 - 8.32

Dissolved oxygen:

5.61 - 8.89 mg/L (73.8 – 107 % 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, 9.5, 17.1, 30.9, 55.6 and 100 mg test item/L (corresponding to 3.8, 6.84, 12.4, 22.2 and 40.0 mg Rh/L)

Measured concentrations:
Concentrations of freshly prepared test media showed recovery rates between 21.7 and
33.2 % of nominal concentrations. Concentrations in aged test media showed recovery rates
between 18.7 and 24.8 % of nominal concentrations and 65.5 to 114 % of initial
concentrations.
The evaluation of effects was based on the geometric mean measured concentrations of
0.907, 1.78, 2.77, 5.42 and 9.89 mg Rh/L, equivalent to 2.27, 4.45, 6.91, 13.5 and 24.7 mg
test item/L (considering a rhodium content of 40.0 % in the test item). Recovery rates of
mean measured concentration were between 22.4 and 26 % of nominal concentrations.
Background concentrations of rhodium were at 0.538, 0.431, 0.019 and 0.220 μg Rh/L at 0h,
24h (fresh/aged) and 48h, respectively, and were deducted from the measured
concentrations.

Details on test conditions:

light intensity: 853-895 lx (corresponding to 11.4-11.9 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.:

18.3 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat. (dissolved fraction)

Basis for effect:

mobility

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

7.29 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element (dissolved fraction)

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

6.91 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat. (dissolved fraction)

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 geometric mean measured test item concentrations.
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 Probitanalysis
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.

geometric mean measured concentrations (mg test tem/L)	total introduced	mobile	immobile	% immobility
control	20	20	0	0
2.27	20	18	2	10
4.45	20	19	1	5
6.91	20	19	1	5
13.5	20	8	12	60
24.7	20	9	11	55

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 to18.3 mg test item/L, corresponding to 7.29 mg Rh/L.

Executive summary:

A study was performed at the Fraunhofer Institute for Molecular Biology and Applied Ecology

(IME) to investigate the influence of the test item Dicarbonyl(pentane-2,4-dionato-

O,O')rhodium 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

9.50, 17.1, 30.9, 55.6 and 100 mg test item/L. Considering the rhodium content of 40.0 %,

3.80, 6.84, 12.4, 22.2 and 40.0 mg rhodium/L were introduced.

Cu-reduced dilution water enriched with CaCl2 was used as test medium. A control with test

medium only was run in parallel.

The concentrations of the test item in the media were confirmed by measurements of

rhodium (Rh) concentrations at beginning of the test, before and after media renewal at 24

hours and at test end using an ICP-MS system.

Concentrations of freshly prepared test media showed recovery rates between 21.7 and 33.2

% of nominal concentrations. Concentrations in aged test media showed recovery rates

between 18.7 and 24.8 % of nominal concentrations. After incubation in the test for 24 hours,

test concentrations showed 65.5 to 114 % of initial concentrations.

The measured concentrations were not within a range of 80 – 120 % of nominal

concentrations and did not remain stable during the test. The evaluation of effects was based

on the geometric mean measured concentrations of 0.907, 1.78, 2.77, 5.42 and 9.89 mg

Rh/L, equivalent to 2.27, 4.45, 6.91, 13.5 and 24.7 mg test item/L (considering a rhodium

content of 40.0 % in the test item).

The test was considered valid according to OECD 202.

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

two highest test concentrations of 13.5 and 24.7 mg test item /L. The EC50 was calculated to

be 18.3 mg test item/L (7.29 mg Rh/L), the NOEC was set to 6.91 mg test item/L (2.77 mg

Rh/L).

Description of key information

The EC50 for immobility of D. magna was 18.3 mg test item/L, corresponding to 7.29 mg Rh/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

18.3 mg/L

Additional information

The short-term toxicity to Daphnia magna was determined according to OECD Guideline 2020 (GLP compliant). Using geometric mean measured dissolved concentrations the EC50 for immobility was calculated as 18.3 mg test item/L, corresponding to 7.29 mg Rh/L.