Diindium trioxide

Endpoint summary

Description of key information

Assessment of the acute inhalation toxicity of indium oxide in Grosz et al 2012:

In2O3 was administered to rats by a single four-hour nose-only inhalation exposure to the dust atmosphere, followed by an observation period of 14 days. No deaths occurred in a group of 10 rats exposed to a mean achieved atmosphere of 5.0 mg/L for 4 hours. The acute inhalation median lethal concentration (LC50) of diindium trioxide, in Wistar Crl:WI rats was therefore considered to be greater than 5.0 mg/L.

Assessment of the acute oral toxicity of indium in Asakura et al 2008:

A limit study with Crj:CD (SD) IGS rats (SPF) was carried out according to OECD guideline no 401 to assess the oral LD50. No deaths and no abnormalities in clinical signs, body weights, and necropsy findings were observed for any of the animals. An LD50 value >2000mg/kg bw was reported.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Reference 1

Endpoint:

acute toxicity: oral

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because a study on acute toxicity by the inhalation route is available

Reference 2

Endpoint:

acute toxicity: oral

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Study period:

not applicable

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Justification for type of information:

Please refer for justification of read-across document in section 13

Qualifier:

according to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

GLP compliance:

not specified

Test type:

standard acute method

Limit test:

yes

Species:

rat

Strain:

other: Crj: CD(SD) IGS rats (SPF)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Japan, Inc
- Age at study initiation: 5 wk
- Weight at study initiation: 125-145 g (male) and 116-130g (female)
- Fasting period before study: 18h
- Diet (ad libitum): pellet diet (MF, Oriental Yeast co, Ltd)
- Water (ad libitum): tap water irradiated by UV rays after passing through a 5µm filter
- Acclimation period: 6days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22.2 ± 2
- Humidity (%): 55 ± 15
- Air changes (per hr): 12 changes per hour
- Photoperiod (hrs dark / hrs light): 12 hrs dark/12 hrs light

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

MAXIMUM DOSE VOLUME APPLIED: the dosing volume was set at 10mg/kg and the dose volume for individual animals was calculated based on the body weight measured just before dosing

DOSAGE PREPARATION (if unusual): done on the administration day

Doses:

2000mg/kg

No. of animals per sex per dose:

12

Control animals:

yes

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: body weights of all animals were measured before dosing and on days 4, 8, and 15 (day of administration was designated as day 1)
- Necropsy of survivors performed: no
- Other examinations performed:
clinical signs: observed 5 times (shortly before dosing, and 0.5, 1, 3 and 5h after dosing) on the those day and thereafter once a day for 14 days
body weight: measured before dosing and on days 4, 8, and 15

Statistics:

Barlett's test: to test the homogeneity of the variances of the data
one way analysis of variance: used when to variances of the treatment group and the control group were homogenous; to analyze statistical significances in the numerical data (body weight, food consumption, hematology, blood chemistry, and organ weights)
Kruskal-Wallis test: used when to variances of the treatment group and the control group were heterogenous; to analyze statistical significances in the numerical data (body weight, food consumption, hematology, blood chemistry, and organ weights)
Dunnett's test or Dunnett-type ranksum test: to examine statistical significances in the data between groups
chi square test: to examine statistical significances in graded categorical data (urinalysis)

Preliminary study:

a preliminary study was done in which no death were observed

Key result

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Mortality:

No mortality observed

Clinical signs:

other: No abnormalities in clinical signs observed

Gross pathology:

Necroscopy:
no abnormalities observed

Other findings:

spontaneous changes: in one male of the 2000 mg/kg group pelvic dilatation of the kidneys was observed

none

Interpretation of results:

GHS criteria not met

Conclusions:

Tests done according to standard protocol. Good quality and considered useful for setting the reference value for acute oral toxicity (LD50>2000mg/kg)

Although this study represented an out of date test guideline as it was deleted on 17th December 2002 and replaced with the fixed dose (TG 420 [4]) and acute toxic class (OECD TG 425 [5]) methods, it meets in light of current test guidelines (i.e. TG 420) the minimum animal required of 5 animals (Asakura et al. used 12)
The preference within the current test guideline is that test substances are preferentially administered as an aqueous solution/suspension/emulsion followed in order of preference by a solution/suspension/emulsion in oil (e.g. corn oil) as used by Asakura et al).

Executive summary:

A limit study with Crj:CD (SD) IGS rats (SPF) was carried out according to OECD guideline no 401 to assess the oral LD50. No deaths and no abnormalities in clinical signs, body weights, and necropsy findings were observed for any of the animals. An LD50 value >2000mg/kg bw was reported.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

2 000 mg/kg bw

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

not applicable

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Qualifier:

according to guideline

Guideline:

EU Method B.2 (Acute Toxicity (Inhalation))

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.1300 (Acute inhalation toxicity)

GLP compliance:

yes (incl. QA statement)

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Research Models and Services, Germany GmbH, Sandhofer Weg 7, D-97633 Sulzfeld.
- Age and weight at study initiation:
Sighting exposure: 10 weeks old, 388 g (male) and 218 g (female)
Main study: approximately 8-9 weeks old, 325-338 g (males) and 234-250 g (females).
- Housing: Group caging (5 animals/cage/ sex), during the sighting study individual caging; cage type: Type III. polycarbonate cages with stainless steel mesh lids
- Diet: ssniff SM R/M-Z+H “Autoclavable Complete Feed for Rats and Mice – Breeding and Maintenance” (ssniff Spezialdiäten GmbH, D-59494 Soest, Germany) ad libitum
- Water: tap water from the municipal supply, as for human consumption from 500 ml bottles ad libitum.
- Acclimation period: Animals were acclimatised to laboratory conditions for 14 days (sighting study) or 11 days (main study) prior to involvement in the study. In addition, the animals were acclimatised to the test apparatus (restrain procedures) for a short period prior to testing in order to lessen the stress during exposure.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19.1- 25.0
- Humidity (%): 30-70 %
- Air changes (per hr): at least 15 air exchanges/hour
- Photoperiod (hrs dark / hrs light): 12 hours daily, from 6.00 a.m. to 6.00 p.m.

Route of administration:

inhalation

Type of inhalation exposure:

nose only

Vehicle:

other: unchanged (no vehicle)

Mass median aerodynamic diameter (MMAD):

2.69 µm

Geometric standard deviation (GSD):

1.8

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus:
Dust particles were produced using a rotating brush dust generator Palas RBG 1000 (Palas GmbH, Karlsruhe, Germany for the sighting exposure.
The test atmosphere in the main study was generated using Solid Aerosol Generator : Topas SAG 410 generator (Topas GmbH, Dresden, Germany) located at the top of the exposure chamber. Dispersion was carried out by a high velocity air flow inside the outlet nozzle.
In order to improve aerodynamic size distribution of the test atmospheres of both part of the study, large particles were trapped via impaction in the subsequent simple pre-separator.
- Method of holding animals in test chamber: the animals were held in polycarbonate restraint tubes located around the chamber which allowed only the animal's nases to enter the exposure port.
- Source and rate of air: Compressed air was supplied by means of an oil-free compressor and passed through a suitable filter system prior to introduction to the dust generator.
- Method of particle size determination:
determined three times during the exposure period using a 7-stage impactor of Mercer style (TSE Systems GmbH, Bad Homburg, Germany). Such devices employ an inertial separation technique to isolate particles in the discrete aerodynamic size ranges. Samples were taken from an unoccupied exposure port (representing the animal’s breathing zone).
The collection substrates and the backup filter were weighed before and after sampling and the weight of test item, collected at each stage, calculated by this difference.
The total amount collected for each stage was used to determine the cumulative amount below each cut-off point size. In this way, the proportion (%) of aerosol less than 0.550, equal to 0.550, 0.960, 1.550, 2.105, 3.555, 6.655 and 10.550µm of aerodynamic diameter was calculated.
From these data, using the software supplied with the impactor (TSE Systems GmbH, Bad Homburg, Germany), the Mass Median Aerodynamic Diameter (MMAD), and Geometric Standard Deviation were calculated. In addition, the proportion (%) of aerosol less than 4µm (considered to be the inhalable portion) was determined.
Results of the particle size analysis from the samples taken at the animal’s breathing zone indicated that the test atmosphere was respirable to the rats.
- Temperature, humidity, pressure in air chamber: monitored continuously and recorded every minute during each exposure period by the TSE-DACO monitoring system integrated into the exposure system

TEST ATMOSPHERE
- Brief description of analytical method used: The test atmosphere was sampled at regular intervals during each exposure period. Samples were taken from an unoccupied exposure port (representing the animal‟s breathing zone) by pulling a suitable, known volume of test atmosphere through weighed GF10 glass fibre filters (Schleicher & Schuell GmbH, Dassel, Germany or similar).
- Samples taken from breathing zone: yes


Animal exposure system:
The animals were exposed, nose-only, to an atmosphere of the test item using a TSE Rodent Exposure System (TSE Systems GmbH, Bad Homburg, Germany). This system comprises of 2, concentric anodised aluminium chambers and a computer control system incorporating pressure detectors and mass flow controllers.
Fresh aerosol from the generation system was constantly supplied to the inner plenum (distribution chamber) of the exposure system from where it was distributed to the individual exposure ports. The animals were held in polycarbonate restraint tubes located around the chamber which allowed only the animal’s nares to enter the exposure port. After passing through the animal’s breathing zone, used aerosol entered the outer cylinder from where it was exhausted through a suitable filter system. Atmosphere generation was therefore dynamic.

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

4 h

Concentrations:

sighting exposure group: 1.00 mg/L
main study group : 5.00 mg/L

No. of animals per sex per dose:

sighting exposure group: 1 (F), 1(M)
main study group: 5(F), 5(M)

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing:
mortality/viability: Animals were checked hourly during exposure, 1 hour after exposure and twice daily (early and late in the working day) during the 14 days of the observation period for morbidity and/or mortality.
body weights: Individual bodyweights were recorded prior to treatment on the day of exposure (before the exposure on Day 0) and on Days 1, 3, 7 and 14.
clinical signs: All animals were observed for clinical signs at hourly intervals during exposure whilst the animals were still restrained. Following exposure, clinical observations were performed twice on the day of exposure (following removal from the restrainer and approximately one hour after completion of the exposure) and subsequently once daily for 14 days.
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs, body weight

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 5 mg/L air

Based on:

test mat.

Exp. duration:

4 h

Mortality:

During the sighting exposure at a concentration of 1.0 mg/L no animals died.
There were no deaths seen in either males or females exposed to the test atmosphere at the concentration of 5.0 mg/L.

Clinical signs:

other: In a single male and female rat (Group 0.1) exposed to a concentration of 1.0 mg/L the only clinical sign was slightly laboured respiration noticed during the third hour of the exposure. Following removal from the restraint and during the 14-day observati

Body weight:

No adverse effect on body weight and body weight gain was observed in animals exposed to 1.0 or 5.0 mg/L.
The mean body weight and body weight gain of the animals at the termination of the study were in the normal range, compared to untreated animals of the same age and strain.

Gross pathology:

Necroscopy:
Pale multifocal discoloration of the lungs seen in 1/5 male and 4/5 females dose at 5.0 mg/L were considered to be potentially test item-related.

Other findings:

none

none

Interpretation of results:

GHS criteria not met

Conclusions:

Tests done according to standard protocol. Good quality and considered useful for setting the reference value for acute inhalation toxicity (LC50, 4h >5mg/L)
Under the experimental conditions of this study, no deaths occurred in a group of 10 rats exposed to a mean achieved atmosphere of 5.0 mg/L for 4 hours. The acute inhalation median lethal concentration (LC50) of diindium trioxide, in Wistar Crl:WI rats was therefore considered to be greater than 5.0 mg/L.

Executive summary:

The purpose of this study was to assess the acute inhalation toxicity of In2O3 when administered to rats by a single four-hour nose-only inhalation exposure to the dust atmosphere, followed by an observation period of 14 days.

The results of the study serve as the basis for hazard assessment and classification and labelling of the product.

Under the experimental conditions of this study, no deaths occurred in a group of 10 rats exposed to a mean achieved atmosphere of 5.0 mg/L for 4 hours. The acute inhalation median lethal concentration (LC50) of diindium trioxide, in Wistar Crl:WI rats was therefore considered to be greater than 5.0 mg/L.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LC50

Value:

5 000 mg/m³ air

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

- An LC50 for acute inhalation toxicity > 5mg/L In2O3 /kg bw (Grosz 2012) is used for the risk characterisation as well as classifcation.

- Based on read across an LD50 for acute oral toxicity >2000mg In/kg bw (Asakura et al., 2008) is used for the risk characterisation as well as classification.

- There are no available data on which to evaluate acute dermal toxicity. However, acute dermal toxicity can be considered to be low in view of the poor absorption by this route.

Justification for classification or non-classification

Based on read across from the results of the available and reliable acute oral rat study with indium, indium oxide does not require classification for acute oral toxicity according to EU CLP criteria (EC 1272/2008).

Based on the results of the available acute inhalation rat study indium oxide does not require classification for acute inhalation toxicity according to EU CLP criteria (EC 1272/2008).

There are no available data on which to evaluate acute dermal toxicity. However, acute dermal toxicity can be consideredto be low in view of the poor absorption by this route and the substance does not meet the criteria for classification as acute toxicity or STOT SE by the oral route. Therefore, indium oxide does not require classfication for acute dermal toxicity according to EU CLP criteria (EC 1272/2008)

No clear evidence of specific target organ toxicity was noted. As such, classification for STOT-SE is not considered appropriate.