Gallium

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Endpoint:

skin sensitisation: in vivo (LLNA)

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:

The solubility of the originally to be used test item - “gallium” – in test specific solvents was determined in pre-test. The test item is insoluble in all solvent indicated by the respective OECD guidelines at the required concentrations. Even after sonication, precipitates were clearly visible with the unaided eye. “Gallium(III) nitrate hydrate” is selected as alternative because of its higher solubility and the absence of sensitizing effects from the nitrate ions. In vitro skin sensitization testing in accordance with OECD 442C is not applicable to the testing of metals and metal compounds and therefore an in vivo approach has been selected.
A read-across approach between gallium (III) nitrate and gallium metal is followed assuming that the toxicity of gallium (III) nitrate hydrate is completely attributed to the 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 429 (Skin Sensitisation: Local Lymph Node Assay)

GLP compliance:

yes (incl. QA statement)

Parameter:

SI

Value:

1.23

Test group / Remarks:

25% Gallium(III) nitrate hydrate

Parameter:

SI

Value:

1.11

Test group / Remarks:

50% Gallium(III) nitrate hydrate

Parameter:

SI

Value:

1.66

Test group / Remarks:

100% Gallium(III) nitrate hydrate

Interpretation of results:

GHS criteria not met

Conclusions:

The test item Gallium (III) nitrate hydrate is not considered a skin sensitizer under the test conditions of this study (OECD 429). As gallium is part of the test substance, a read-across is performed and Gallium is also not considered a skin sensitizer.

Executive summary:

The sensitization of Gallium (III) nitrate hydrate was evaluated using the Local Lymph Node Assay (LLNA). The LLNA has been developed to determine the allergic contact sensitization potential of chemicals.

Based on the recommendations of the OECD 429, the test item was suspended in DMSO (w/v). The positive control (alpha-Hexylcinnamic aldehyde) (25 %) was dissolved in the same vehicle. The Pre-screen test was performed using the dose of 5780 mg test item/mL (referred to as 100 %). Based on the observations recorded in the Pre-screen tests, the concentration of 100 % was selected as top dose for the main test.

Five female mice (CBA/Ca) per group were topically exposed (dorsum of both ears) to the test itemat concentrations of 25 %, 50 % and 100 % (corresponding to 1445, 2890 and 5780 mg/mL, respectively), to the positive control and to the vehicle only. Lymphocyte proliferation was measured using incorporation of radioactive 125I-iododeoxyuridine and 10-5M fluorodeoxyuridine in the draining lymph nodes. The radioactive incorporation was expressed as disintegrations per minute

(DPM)/pooled treatment group and compared with DPM value from the vehicle control group and expressed as the Stimulation Index (SI).

After application of the test item at three concentrations (25 %, 50 % and 100 % w/v) the animals did not show visible clinical symptoms of either local irritation or systemic toxicity. In this study the Stimulation Indices (SI) of 1.23, 1.11 and 1.66 were determined with the test item at concentrations of 25 %, 50 %, and 100 % in DMSO, respectively. The EC3 value could not be

calculated, since none of the tested concentrations induced a SI greater than the threshold value of 3.

The test item Gallium (III) nitrate hydrate is not considered a skin sensitizer under the test conditions of this study.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available