Carbonyl(pentane-2,4-dionato-O,O')(triphenylphosphine)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:

23 Sept 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:20.59% Rh

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.
Aged samples were filtered through a 0.22 μm PES filter before sampling.
All samples were acidified and analysed within 24 hours after sampling. All samples will be
discarded after finalization of the study.

Vehicle:

no

Details on test solutions:

The highest test concentration was prepared by weighing in 99.9 mg (d-1) and 100 mg (d0)
of the test item and transferring it to 1000 mL test medium. This solution was first
ultrasonicated for 30 minutes and afterwards stirred for 24 hours. Since undissolved test
material was observed at the surface of the test solution after stirring, the solutions was
filtered using a 0.22 μm PES filter to remove the undissolved test material. After filtration, the
test solution was clear and no undissolved material was left. The filtered solution was diluted
to obtain the lower test concentrations. A control consisting of dilution water only was treated
the same way as test solutions.

NOTE: In an attempt to increase test item dissolution, an oversaturated solution was prepared by
weighing 1000 mg of the test item and transferring it to 1000 mL test medium in an additional
non-GLP test. This solution was stirred for 72 hours at 30 – 35 °C. Since
undissolved test material was observed at the surface of the test solution after stirring, the
solution was filtered using a 0.45 μm PES filter to remove the undissolved test material. After
filtration, the test solution was clear and no undissolved material was left. This additional test
did not show a higher test item dissolution (as assessed by dissolved Rh concentration in
solution), and no effects on daphnid survival were observed.

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:

18.7-19.4°C (19.1°C mean temperature)

pH:

7.70-8.11

Dissolved oxygen:

7.28-9.28 mg/L (84.6-105 % 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 -6.25-12.5-25.0-50.0-100 mg test item/L (corresponding to control - 1.29-2.57-5.15-10.3-20.6 mg Rh/L)

Measured concentrations:
Concentrations of freshly prepared test media showed low recovery rates between 0.230 and
0.346 % of nominal concentrations. Concentrations in aged test media showed recovery
rates between 0.174 and 0.365 % of nominal concentrations and therefore only slightly
changed with 71.1 to 113 % of initial concentrations.
The measured concentrations were not within a range of 80 – 120 % of nominal
concentrations. Therefore, the evaluation of effects was based on the geometric mean
measured concentrations of 3.18, 6.62, 13.6, 26.0 and 53.9 μg Rh/L, equivalent to 15.4,
32.2, 65.8, 126 and 262 µg test item/L (considering a purity of 20.59 % in the test item).
Recovery rates of mean measured concentration were between 0.247 and 0.263 % of
nominal concentrations.
Background concentrations of rhodium were 0.021, 0.020, 0.09 and 0.291 μg Rh/L at test
start, after 24h (aged, fresh) and test end, respectively. Background concentrations were
deducted from measured concentrations.

NOTE: In an attempt to increase test item dissolution, an oversaturated solution was prepared by
weighing 1000 mg of the test item and transferring it to 1000 mL test medium in an additional
non-GLP test. This solution was stirred for 72 hours at 30 – 35 °C. Since
undissolved test material was observed at the surface of the test solution after stirring, the
solution was filtered using a 0.45 μm PES filter to remove the undissolved test material. After
filtration, the test solution was clear and no undissolved material was left. This additional test
did not show a higher test item dissolution (as assessed by dissolved Rh concentration in
solution), and no effects on daphnid survival were observed.

Details on test conditions:

light intensity: 865-913 lx (corresponding to 11.5-12.2 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.:

> 262 µg/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.:

> 53.9 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element (dissolved fraction)

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

> 262 µg/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
deviation from the nominal concentration was greater than ± 20 %.
Results did not show inhibition of around 50 %, therefore no EC50 and EC10 value together
with 95 % confidence intervals using Probit-analysis assuming log-normal distribution of the
values could be calculated. Therefore, the EC50 will be reported as being > highest mean
measured concentration tested.

The NOEC and LOEC values were determined using appropriate statistical methods, if
possible (e.g. Fisher`s Exact Binomial Test for quantal response).

The computer program ToxRat was used for statistical evaluations.

geometric mean measured concentrations (µg test tem/L)	total introduced	mobile	immobile	% immobility
control	20	19	1	5 (-)
15.4	20	20	0	0(-)
32.2	20	14	6	30(-)
65.8	20	17	3	15(-)
126	20	20	0	0(-)
262	20	19	1	5(-)

(-) statistically not significant different from the control

30 % and 15 % immobility were observed in the treatments with 32.2 and 65.8 μg test item/L.

However, the statistical evaluation revealed that this increase in immobility is not significantly

different to the control. Therefore, the observed immobility is considered to be of no

biological relevance as no clear concentration-response behavior at the higher concentration

levels was observed. The observed immobility is mainly related to a single replicate.

Mobile daphnids after 24 h and 48 h. Single values [Ind.] of the replicates. N = 5 per replicate. Concentration of test item given as

geometric mean measured concentration [μg/L].

test species	replicate	control	15.4	32.3	65.8	126	262
24h	1	5	5	5	5	5	5
	2	5	5	5	5	5	5
	3	5	5	4	5	5	5
	4	5	5	4	5	5	5
48	1	5	5	5	4	5	5
	2	5	5	5	4	5	4
	3	5	5	1	4	5	5
	4	4	5	3	5	5	5

The test item had no statistically significant effect on immobility of the daphnids up to the

highest test concentrations. The EC50 for immobility is determined to be > 262 μg test item/L

(geometric mean measured concentrations) and the NOEC is ≥ 262 μg test item/L (geometric

mean measured concentrations). Considering the rhodium content of 20.59 %, the EC50 is

determined to be > 53.9 μg Rh/L and the NOEC is ≥ 53.9 μg Rh/L.

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 test item had no statistically significant effect on immobility of the daphnids up to the highest test concentrations. The EC50 for immobility is determined to be > 262 μg test item/L and the NOEC is ≥ 262 μg test item/L (based on geometric mean measured concentrations). Considering the rhodium content of 20.59 %, the EC50 and NOEC is determined to be 53.9 μg Rh/L, respectively.

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 Carbonyl(pentane-2,4-dionato-O,O’)

(triphenylphosphine)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

6.25, 12.5, 25.0, 50.0 and 100 mg test item/L. Considering the rhodium content of 20.59 %,

1.29, 2.57, 5.15, 10.3 and 20.6 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 low recovery rates between 0.230 and

0.346 % of nominal concentrations. Concentrations in aged test media showed recovery

rates between 0.174 and 0.365 % of nominal concentrations. During incubation in the test,

test concentrations only slightly decreased with 71.1 to 113 % of initial concentrations.

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

concentrations. Therefore, the evaluation of effects was based on the geometric mean

measured concentrations of 3.18, 6.62, 13.6, 26.0 and 53.9 μg Rh/L, equivalent to 15.4,

32.2, 65.8, 126 and 262 μg test item/L (considering a rhodium content of 20.59 % in the test

item).

The test item had no statistically significant effect on the immobilization of the daphnids in

any tested concentration. The test was considered valid according to OECD 202.

The test item Carbonyl(pentane-2,4-dionato-O,O’)(triphenylphosphine)rhodium did not show

any effect on the test organism Daphnia magna in a 48-hour acute toxicity test at the highest

tested dose level. Based on geometric mean measured concentrations, the EC50 for

immobilization of the test organisms was set to be higher than the highest tested

concentration of 262 μg test item/L, equivalent to 53.9 μg Rh/L.

Description of key information

The EC50 for immobility of D. magna was >262 µg test item/L, corresponding to >53.9 µg Rh/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

262 µg/L

Additional information

The short-term toxicity to Daphnia magna was determined according to OECD Guideline 202 (GLP compliant). Effects were expressed as geometric mean measured dissolved test item concentrations. The test item did not show any effect on the test organism Daphnia magna in a 48-hour acute toxicity test at the highest tested dose level.

The EC50 for immobility was calculated as >262 µg test item/L, corresponding to >53.9 µg Rh/L.