Gallium

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

As gallium is quite insoluble (ca 46 µg/L) toxicity testing has been performed with gallium(III) nitrate hydrate, which has a higher water solubilty. A read-across approach is followed assuming that the toxicity of gallium (III) nitrate hydrate is completely attributed to the dissolved gallium ion. Even if the nitrate ion would contribute partly to the toxicity of the substance, it is considered worst case to completely attribute the toxicity to the gallium ion.

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

GLP compliance:

yes (incl. QA statement)

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

10.3 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element

Remarks:

Gallium

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

LOEC

Effect conc.:

21.4 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element

Remarks:

Gallium

Basis for effect:

mobility

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

23.65 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element

Remarks:

Gallium

Basis for effect:

mobility

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

14.96 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element

Remarks:

Gallium

Basis for effect:

mobility

Validity criteria fulfilled:

yes

Conclusions:

The following results were determined for the test item Gallium(III) nitrate hydrate (species:Daphnia magna).
Based on dissolved Gallium (III) concentration:
48h-NOEC = 10.3 mg/L
48h-LOEC = 21.4 mg/L
24h-EC50 = 23.65 mg/L
48h-EC50 = 14.96 mg/L

Executive summary:

The study was performed using 6 concentrations ranging from 13 to 581 mg/L (test item) and respectively 2.2 to 100 mg/L Gallium (III) nominal concentration. For each test concentration and the blank control, 20 daphnia were exposed to the test item for 48 hours in

a static test system. After 24 and 48 hours, the immobilised daphnia were counted. Two concentrations showed toxicity between 90 and 100% immobilisation. Only one treatment (58 mg/L test item) showed 5% immobilisation, which can be neglected as biological

fluctuation. None of the animals was immobilised in the blank control. Potassium dichromate K2Cr2O7 (CAS No. 7778-50-9) was used as positive control in a current reference study to assure that the test conditions are reliable.

At the beginning and at the end of the test, the content of Gallium (Ga) as part of the test item (17.2 % Gallium content) in the test solutions was determined using ICP-OES - determination. The measured values are not in the range ± 20% of the nominal value. In

the validation of the analytical method, a precipitation of the test item was observed when adjusting the pH during the preparation of the stock solution for the stability test. The deviation from the 20% of the nominal value can therefore be explained. This is again confirmed by the very small margin of the % of nominal values (45 - 48%) in the test solutions.

Therefore, the results are related to the geometric mean value of the measurements at the start and the end of the exposure (t = 0 and 48 h, respectively) (cf. OECD Guideline No. 202). Recovery in the unfiltered samples from test solutions was similar to the recovery in the filtered stability samples (34 – 39%). It can therefore be concluded that filtration or not did not critically affect the result of the Ga analysis in the test solutions and the measured Ga concentrations can be considered as dissolved concentrations.

The results are given in relation to the test item content and additionally in relation to the Ga content.Due to the rapid increase in immobilisation, no confidence interval can be specified for the EC values. In addition, the significance level was lowered for this reason.

The following results were determined for the test item Gallium(III) nitrate hydrate (species:

Daphnia magna).

Based on dissolved test item concentration:

48h-NOEC = 60.0 mg/L

48h-LOEC = 124.3 mg/L

24h-EC50 = 137.48 mg/L

48h-EC50 = 87.03 mg/L

Based on dissolved Gallium (III) concentration:

48h-NOEC = 10.3 mg/L

48h-LOEC = 21.4 mg/L

24h-EC50 = 23.65 mg/L

48h-EC50 = 14.96 mg/L

Description of key information

A GLP conform study was performed on short-term toxicity of gallium(III) nitrate hydrate towards Daphnia magna according to the OECD 202 guideline. The results were expressed based on the measured dissolved Ga concentration.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

14.96 mg/L