Diindium trioxide

Endpoint summary

Description of key information

Short-term aquatic toxicity

There were several studies available on short-term aquatic effects of indium substances, mostly on indium trichloride.

Since, like for the other metals, the ecotoxicity of Indium and its compounds is basically related to the effect of the Indium-ion, In3 +, all studies obtained on InCl3 and other soluble In-substances can be read accross to the other In-substances. All PNECs derived are expressed as indium (ion) concentration. They are consequently also relevant for all In-substances.

A total of 12 LC/EC50s, from 9 different species, representing 3 trophic levels (1 algae, 6 invertebrate and 2 fish species) is available. Below is a table showing the species in the indium trichloride acute dataset, the respective LC/EC50 values, species group and the references.

Species	LC/EC50 mg/L	Endpoints	Species group	Reference
Oreochromis mossambicus	19.5	48-h, mortality	Fish	Lin & Wang, 1998
Sillago japonica*	>20.0	24-h, mortality	Fish	Onikura et al. 2008
Brachionus plicatilis*	24.4	24-h, mortality	Invert.	Onikura et al. 2008
Artemia salina*	51.0	48-h, mortality	Invert.	Onikura et al. 2008
Artemia salina	7.1	48-h, mortality	Invert.	Onikura et al. 2008
Americamysis bahia*	30.5	96-h, mortality	Invert.	Onikura et al. 2008
Daphnia magna	>455.5	48-h, mortality	Invert.	Aecom, 2012
Daphnia magna	31.9	24-h, mobility	Invert.	Zurita et al. 2007
Hyalella azteca	>3.1	7-d, mortality	Invert.	Borgmann et al. 2005
Hyalella azteca**	>1	7-d, mortality	Invert.	Borgmann et al. 2005
Macrobrachium nipponense	6.9	96-h, mortality	Invert.	Yang et al. 2014
Pseudokirchneriella subcapitata	1.6	72-h, biomass	Algae	Aecom, 2012

*Test conducted in marine water; ** soft water.

The lowest acute toxicity value was >1mg In/L, so it was concluded that there is no acute classification for aquatic effects under CLP.

Chronic aquatic toxicity

A total of 11 NOEC/EC10s, from 7 different species, representing 3 trophic levels (1 algae, 4 invertebrates and 2 fish species) were used to derive the PNEC. The species used in the PNEC assessment, the respective NOEC/EC10 values, endpoints, species group and the references are presented in table below.

Species		NOEC/EC10 µg/L		Endpoint		Species group		Reference
Oreochromis mossambicus		1950		16-d, length		Fish		Lin & Wang, 1998
Pimephales promelas		25000		14-d, weight		Fish		Aecom, 2012
Ceriodaphnia dubia*		93.92*		7-d, reproduction		Invert.		Aecom, 2011^a,b,c; Aecom, 2012^c,d
Daphnia magna		410		21-d, reproduction		Invert.		Aecom, 2012^e
Strongylocentrotus purpuratus		825		48-h, development		Invert.		Nautilus, 2012
Mytilus galloprovincialis		18100		48-h, development		Invert.		Nautilus, 2012
Pseudokirchneriella subcapitata		366		72-h, biomass		Algae		Aecom, 2012g

*Geometric mean calculated from 5 separate studies. 

 

Additional information

Indium and indium compounds form a data poor substance group. Under neutral real-life water conditions, there was no dosis-respons observed with dissolved In-concentrations. Therefore all results were expressed as total In.

It seemed that higher loading of InCl3 during experiments leads to a shift in pH: addition of In at higher loading (i.e. > 10mg InCl3/L) causes a pH effect, which could influence metal speciation and subsequently the ecotoxicity results.

Acute aquatic toxicity

There were two studies conducted with Daphnia magna as a test species where in a first test pH was adjusted to test conditions and in a second test pH was not adjusted (Aecom 2012). The study with the unadjusted pH (lower pH shift in the higher In concentrations) had a 8.5 times lower LC50 compared to the adjusted pH test. As the higher In concentrations in the unadjusted pH tests had pH lower than 4.5, the LC50 of the adjusted pH test was used as an appropriate toxicity endpoint for acute freshwater toxicity tests.

Several acute studies did not record the pH. For example, Lin and Hwang (1998) tested the toxicity of InCl3 on 3-day-old larvae of Oreaochromis mossambicus. The LC50 observed on Oreochromis mossambicus is 19519 µg total In/L. Lin and Hwang (1998) did not measure pH. High loading with In in the tests (>15 mg In/L) could result in a pH-drop and subsequently contribute to an observed ecotoxicity. However, even if pH were not recorded the data were still used, as this would represent a ‘worst-case’ scenario (i.e. very conservative dataset). Given that all acute data reviewed in the dataset showed LC/EC50 values greater than 1 mg/L, this results in there being no classification.

Chronic aquatic toxicity

The long-term aquatic toxicity database covers 7 different species, representing 3 trophic levels (1 algae, 4 invertebrates and 2 fish species).

Indium precipitates under neutral (6-8) pH conditions. Therefore, no dose-response could be correlated with the observed dissolved In concentrations. The effect concentrations are expressed as total In concentrations. Total and dissolved indium concentrations were measured in 3 tests with Ceriodaphnia and 2 tests with D. magna. In the study of Aecom (2012d) DOC was used in the test medium (nominal concentration of 10 mg C/L). This study clearly indicates that Indium binds strongly to DOC, as the dissolved In concentration was comparable to the total In concentration; whereas in the other studies where no DOC was used, the dissolved concentrations were much less than the total In concentrations. Results are shown in Table below:

Species	NOEC nominal (µg total In/L)	NOEC dissolved (µg In/L)	NOEC total (µg In/L)	DOC	Reference
Ceriodaphnia dubia	62	3.6	52.9	ND	Aecom (2011a)
Ceriodaphnia dubia	62	1.9	58.1	ND	Aecom (2012c)
Ceriodaphnia dubia	1847	1184	1710	10	Aecom (2012d)
Daphnia magna	1000	5.4	809	ND	Aecom (2012e)
Daphnia magna	<3300	3.6	2780	ND	Aecom (2012e)

The studies of Aecom (2011b,c; 2012 a,c,d,e) also clearly indicate that the ecotoxicity of Indium towards invertebrates is influenced by hardness.

Species	pH	Hardness (mg CaCO3/L)	DOC (mg C/L)	NOEC (µg total In/L)	EC10 (µg total In/L)	EC50 (µg total In/L)	Reference	Remarks
Fish
Pimephales promelas	7.8 -8.2	ND	ND	>25000	>25000		Aecom (2012a)
Oreochromis mossambicus	ND	ND	ND	1951.9	ND	ND	Lin and Hwang (1998)	pH was not measured
Invertebrate
Ceriodaphnia dubia	8.0	90	ND	10	ND	ND	Aecom (2011b)	test was range finder study; test result not used for classification and PNEC deriviation
Ceriodaphnia dubia	8.1	96	ND	52.9	<20.4	ND	Aecom (2011a)
Ceriodaphnia dubia	8.2	90	ND	20	<20	ND	Aecom (2011c)
Ceriodaphnia dubia	7.9	402	ND	58.1	87.2	ND	Aecom (2012c)
Ceriodaphnia dubia	7.9	90	10	>1710	130	ND	Aecom (2012d)	NOEC test result not used for PNEC deriviation as lower reproduction in control determines NOEC
Daphnia magna	7.3 -8.5	170	1.55 -2.21	809	1398	412	Aecom (2012e)	Tests conducted in hard water
Daphnia magna	6.8 -7.6	510	1.43 -2.03	<2780	<2780	<2780	Aecom (2012e)	Tests conducted in very hard water
Algae
Pseudokirchneriella subcapitata	7.4 -9.6	14	1.39	321	1164	>5025	Aecom (2012f)

Given the number of species data and the taxonomic coverage, the PNEC was derived using a species sensitivity distribution approach.

3. Aquatic chronic toxicity: marine water

Two marine species are included in the aquatic chronic dataset, Mediterranean mussel (Mytilus galloprovincialis) and the purple sea urchin (Strongylocentrotus purpuratus) (see Section 6.1). They are neither the most sensitive or tolerant species in the SSD and are included with the freshwater species-sensitivity distribution. Given the lack of difference observed in toxicity in freshwater and marine water, the same PNEC is derived for the marine water.

4. STP

There were two test results available. In a first test, the respiration slugde study was carried out without pH adjustement. This resulted in a NOEC of 460 mg InCl3/L and an EC50 of 680 mg InCl3/L. The pH in the controls and substance series, before addition of sludge was 7.3 at 10 mg/L and decreased to 2.9 at 1000 mg/L. After 3 hours exposure period the pH in the Indium trichloride series was 7.8 at 10 mg/L and decreased to 3.4-3.7 at 1000 mg/L.

In a second test, the pH was adjusted to 7.2. This resulted in a NOEC of 1000 mg/L and an EC50 of >1000 mg InCl3/L. As pH was very low in the pH non adjustement treatment, the results of the pH adjusted treatments were taken to set the PNEC for STP. The NOEC was 1000 mg InCl3/L or 516 mg In/L. Using an AF of 10, this results in a PNEC of 51.6 mg In/L for STP.