Indium trihydroxide

Endpoint summary

Description of key information

High quality repeat dose whole body inhalation studies, following OECD guidelines 412 (2 -week exposure) and 413 (13 -week exposure) were conducted on indium oxide (IO) and indium tin oxide (ITO) (Nagano et al 2011) in rats and mice. Specific effects included increased lung weights, alveolar proteinosis, increased inflammatory cell infliltration and hyperplasia of the alveolar epithelium. A further group of animals was used to set-up a 13 -week recovery group at the 0.1 mg/m3 ITO dose level. The comparable results in rats are shown below:

RATS 13 wk study	IO (mg/m^3)	IO (mg/m^3)	IO (mg/m^3)	ITO (mg/m^3)	ITO (mg/m^3)	ITO (mg/m^3)	ITO (mg/m^3)+13 wk recovery	ITO (mg/m^3)+13 wk recovery	ITO (mg/m^3)+13 wk recovery
	0	0.1	1	0	0.1	1	0	0.1	NA
Lung weight		↑	↑		↑	↑		↑
Alveolar proteinosis			+		+	+		+
AM infiltration		+ (slight)	+		+	+		+
Inflammatory cell infiltration			+			+		+
Hyperplasia alveolar epithelium			+					+
BALT granuloma
Alveolar wall fibrosis								+
Pleural thickening								+
LN granuloma			+		+	+		+
		NOAEL			LOAEL

AM: alveolar macrophages; LN: Lymph nodes

If the results of the studies are evaluated in context with the guidance produced by the SCOEL committee (Ref: European Commission Methodology for the derivation of occupational exposure limits. Scientific Committee on Occupational Exposure Limits (SCOEL). Key documentation (version 7), June 2013) on setting an OEL, where the objective of Council Directive 80/1107/EC is "The protection of workers against risks to their health and safety from exposure to chemical, physical and biological agents considered harmful" then the data used to derive an OEL should be separated into the 4 categories listed below:

The effects of increasing exposure to chemical substances may be viewed as a continuum:

(1) no effects observed

(2) compensatory effects or early effects of dubious significance without adverse health consequences

(3) early health impairement (clear adverse effects)

(4) overt disease, possibly death

Effects may be considered to become 'adverse' during the transition from (2) to (3) above

Using this guidance when interpreting the results of the 13 -week study in rat with IO it could be concluded that the 0.1 mg/m3 dose level is an NOAEL. The only effect observed at this dose level, infiltration of alveolar macrophage and neutrophils and increased lung weight, could be due to exposure to a relatively insoluble, high density metal salt. Without other clear adverse endpoints present, the 0.1mg/m3 dose level shows an adaptive resonse to the clearance of a relatively insoluble metallic salt and could therefore be defined as a NOAEL for the purpose of defining a DNEL or OEL.

For ITO, the adverse effects were more significant even at the lowest dose tested in the rat and all lung/lymph lesions persisted in the 13-week recovery period for ITO (not measured for IO) with progression to alveolar wall fibrosis, alveolar epithelial hyperplasia, infiltration of alveolar macrophages and inflammatory cells at 0.1 mg/m³.

 

In mice, similar results were observed to those described in the rat studies (lesions more severe with ITO than IO) but with overall lower severity scores compared to rats, particularly for alveolar proteinosis and alveolar macrophage infiltration. There was no recovery period included in the study.

In a further study, Nagano et al 2011, conducted a 2 -year carcinogenicity study on ITO in the rat and mouse to OECD Guideline 451 (see below in additional information).

The table below present the LOAEL and NOAEL's for the most sensitive respiratory effects observed in the sub-chronic inhalation animal studies conducted with respirable size aerosols of indium oxide and ITO in Fisher 344 rats and B6C3F1 mice. It also calculates an NOAEL for use in subsequent chronic DNEL derivation for IO and ITO. The toxic effects of both compounds in both species were typical of lung inflammation, with the overall response for both compounds being greater in rats and the response for ITO being greater than IO in both species.

MICE	IO (mg/m^3)	ITO (mg/m^3)
13 wk NOAEL	0.1	NA
13 wk LOAEL	1.0 (M/F)	0.1 (M/F)
RATS
13 wk NOAEL	0.1	NA
13 wk LOAEL	1 (M/F)	0.1 (M/F)
2 yr NOAEL		NA
2 yr LOAEL		0.01
Choice of NOAEL/LOAEL for DNEL determination	0.1 mg/m^3	0.01 mg/m^3
Conversion factor from sub-chronic to chronic^a	2	1
Conversion factor for NOAEL determination from a LOAEL value^b	1	3
Comparable chronic NOAEL for DNEL derivation	0.05 mg/m^3	0.0033 mg/m^3

a –Conversion for difference in duration of exposure:2 (sub-chronic to chronic exposure)

b –To convert a LOAEL to a NOAEL, the REACH TGD (Chapter R.8 of the ‘Guidance on information requirements and chemical safety assessment’) suggests an assessment factor (AF) of 3 as minimum for the majority of cases and going up to a default of 10 for exceptional cases. An AF of 3 is applied to convert LOAEL to NOAEL.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Repeated dose toxicity: inhalation - local effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

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

Adequacy of study:

key study

Study period:

No information

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

see section 13 in IUCLID for read-across justification report

Qualifier:

according to guideline

Guideline:

OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)

GLP compliance:

not specified

Limit test:

no

Species:

rat

Strain:

Fischer 344/DuCrj

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Japan, Inc (Kanagawa, Japan)
- Age at study initiation: 4 wk old
- Weight at study initiation: M: 101-104 g (mean body weight per group); F: 92-94 g (mean body weight per group)
- Housing: individually in stainless-steel wire hanging cages, which were placed in a stainless steel inhalation exposure chamber
- Diet : sterilized commercial pellet diet (CRF-1, Oriental Yeast Co., Ltd, Tokyo, Japan)
- Water : sterilized water, ad libitum
- Acclimation period: 2 wk

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24
- Humidity (%): 30-70
- Air changes (per hr): 12
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

whole body

Vehicle:

other: no data

Mass median aerodynamic diameter (MMAD):

>= 2.1 - <= 2.3 µm

Geometric standard deviation (GSD):

1.7

Remarks on MMAD:

dose 0.1 mg/m3 : MMAD: 2.1 µm, GSD: 1.7µm
dose 1mg/m3: MMAD: 2.3 µm, GSD: 1.7µm

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus:
for 100mg/m3 a system was used consisting of a dust feeder equiped with an ejector, an exposure chamber and a digital dust indicator (Type AP-632T, Sibata Scientific Technology, Ltd, Tokyo, Japan)
for 10, 1 and 0.1mg/m3 a system was used consisting of the first-stage system for aerosol generation of a high concentration at 100mg/m3 and a further dilution system
- System of generating particulates/aerosols:
for 100mg/m3: drawing the powder with compressed clean air at the first ejector and introduced into the top of the exposure chamber where the filtered air had been kept flowing downward at 12 air changes/h
for 10, 1 and 0.1mg/m3: aerosol generation of the high concentration and its regulation were performed in the same manner as described above, and airflow containing the aerosol was delivered to a reservoir chamber for stabilization of the aerosol concentration. The airflow containing the aerosol was delivered to the second ejector and then introduced into the top of the exposure chambers where the filtered air had been kept flowing downward at 12 air changes/h
- Method of particle size determination: particles were collected on a filter and dissolved in a mixture solution of distilled water, hydrochloric acid and nitric acid (2:2:1 by volume ratio) at 160 °C. The resulting solution was diluted with nitric acid, and then subjected to atomic absorption spectrometry analysis (Polarized Zeeman Atomic Absorption Spectrophotometer, Z-5010)
- Particle size distribution: the material aerosol was collected with an 8-stage Andersen sampler. Using the mass of the particles on the filter collected at each stage of the Andersen sampler, mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) were determined
- Temperature, humidity, pressure in air chamber: negative pressure (-100 Pa)


TEST ATMOSPHERE
- Analytical method used: the mass-equivalent concentration of the material aerosol was monitored with the digital dust indicator; aerosol concentration in the exposure chamber was monitored with the second digital dust indicator and regulated at a target concentration of 10, 1 or 0.1 mg/m3

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

none

Duration of treatment / exposure:

13 wk

Frequency of treatment:

6h/day, 5day/wk for 13 wk

Dose / conc.:

0.1 mg/m³ air

Dose / conc.:

1 mg/m³ air

No. of animals per sex per dose:

10 rats of each sex per dose

Control animals:

yes, concurrent no treatment

Details on study design:

none

Positive control:

None

Observations and examinations performed and frequency:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: animals were observed daily for their clinical signs and mortality

BODY WEIGHT: Yes
- Time schedule for examinations: weekly throughout the study periods

FOOD CONSUMPTION:
- Food consumption for each animal determined : weekly throughout the study periods

HAEMATOLOGY: Yes


OTHER: sections of lung tissue were examined.

Sacrifice and pathology:

animals surviving to the end of the 13wk received complete necropsy

Other examinations:

Determination of indium concentrations in the lung and blood

Statistics:

Body weight, organ weight, and hematological and blood biochemical parameters were analyzed by Dunnett's test. Histopathological findings in the 13 weeks study were analyzed by chi-square. A two tailed test was used for all statistics. a p value of 0.05 was used as the level of significance.

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

not examined

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

not specified

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY: neither death nor abnormal clinical sign, such as irregular sounds of respiration, was observed in any group exposed to the test material for 13 weeks. There was no growth retardation in any group exposed to the test material for 13 weeks as compared with the growth rate in the respective control.

HAEMATOLOGY: potassium was significantly decreased in both 0.1 and 1 mg/m3 indium oxide exposed rats. Significant decreases in sodium and chlorine in the 0.1 and 1 mg/3 indium oxide exposed rats and significantly decreased triglyceride in the 0.1 and 1 mg/m3 indium oxide exposed female rats were also observed.

ORGAN WEIGHTS: significantly increased relative lung weights in the rats of both sexes exposed to indium oxide at 0.1 and 1 mg/m3

HISTOPATHOLOGY: NON-NEOPLASTIC:
-test material particles were deposited in the lung of all the exposed rats , primarly within the alveolar macrophages and partly as a free form in the alveolar space. The test material particles were also observed to a lesser extent in the bronchus-associated lymhoid tissue (BALT) of the lung of 1mg/m3 indium oxide exposed rats, in the mediastinal lymph nodes (MLN) of both 0.1 and 1mg/m3 indium oxide exposed rats and in the nasal-associated lymphoid tissue (NALT) of the nasopharyngeal duct of the 1mg/m3 indium oxide exposed rats
- significant increase of alveolar proteinosis in the 1 mg/m3 indium oxide exposed rats
- incidences of alveolar macrophage infiltration were significantly increased in the 0.1 and 1mg/m3 indium oxide exposed rats
- significant infiltration of inflammatory cells was observed in the 1 mg/m3 indium oxide exposed rats
- significant increase hyperplasia of alveolar epithelium occured in the 1mg/m3 indium oxide exposed rats

Dose descriptor:

LOAEL

Effect level:

1 mg/m³ air

Based on:

test mat.

Sex:

male/female

Basis for effect level:

organ weights and organ / body weight ratios

other: lung effects

Dose descriptor:

NOAEL

Effect level:

0.1 mg/m³ air

Based on:

test mat.

Sex:

male/female

Remarks on result:

other: The only effects are: infiltration of alveolar macrophage and neutrophils, increased lung weight. The 0.1 mg/m3 dose level shows an adaptive response to the clearance of a relatively insoluble metallic salt and could therefore be defined as a NOAEL

Critical effects observed:

yes

Lowest effective dose / conc.:

1 mg/m³ air

System:

respiratory system: lower respiratory tract

Organ:

alveoli

bronchi

bronchioles

lungs

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

yes

Lung and blood contents of indium: -) lung contents of indium were increased with an increase in the concentration of exposure to indium oxide or indium tin oxide: -the exposure concentration related increase in the whole lung content of indium was disproportionally lowered to greater extent in the indium tin oxide exposed rats than in the indium oxide exposed rats. -the whole lung contents of indium in the 0.1 mg/m3 indium tin oxide exposed rats of both sexes were higher than those of the 0.1mg/m3 indium oxide exposed rats of both sexes. -the whole lung contents of indium in the indium tin oxide exposed rats of both sexes measured at the end of the 26 wk post exposure period were lowered to 40% as compared with those measured at the end of the 13 wk exposure -) the blood contents of indium in the 1mg/m3 indium tin oxide exposed groups of both sexes were 4 -fold higher than those in 1mg/m3 indium oxide group of both sexes. The blood contents of indium in the 0.1 mg/m3 indium tin oxide exposed rats of both sexes measured at the end of the 26 week post exposure period were 1.3 fold higher than those measured at the end of the 13 week exposure period.

Conclusions:

Persistent pulmonary lesions including alveolar proteinosis and macrophage infiltration occured after 13 wk inhalation exposure of F344 rats to indium oxide.
In this study the rats were also administered by inhalation indium tin oxide and the results indicate that the pulmonary toxicity of inhaled indium tin oxide particles is more severe than that of indium oxide particles and that alveolar macrophages play a critically important role in the induction of indium toxicity as evidenced by alveolar proteinosis, alveolar macrophage infiltration and swollen alveolar macrophages engulfing the particles, all of which occur at the lowest exposure concentration of 0.1 mg/m3 indium tin oxide.

Executive summary:

A study was conducted to determine the effects of sub-chronic exposure of the test material on the respiratory system in F344 rats.

The test material was administered by inhalation 6 h /d and 5 d/wk for 13 wk at 0, 0.1 or mg/m3 to groups of 10 rats/sex/dose. Blood and lung contents of indium were elevated in a dose-related manner in the indium oxide exposed rats. The indium oxide particles were deposited in the lung, mediastianl lymph node and nasal-associated lymphoid tissue. Exposures to the test material induced alveolar proteinosis, infiltrations of alveolar macrophages and inflammatory cells and alveolar epithelial hyperplasia in addition to increased lung weight.

In conclusion, persistent pulmonary lesions including alveolar proteinosis and macrophage infiltration occured after 13 wk inhalation exposure of rats to indium oxide.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

0.1 mg/m³

Study duration:

subchronic

Species:

rat

Repeated dose toxicity: dermal - systemic effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: dermal

Data waiving:

exposure considerations

Justification for data waiving:

a short-term toxicity study does not need to be conducted because exposure of humans via the dermal route in production and/or use is not likely as based on the provided thorough and rigorous exposure assessment

Critical effects observed:

not specified

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: dermal

Data waiving:

exposure considerations

Justification for data waiving:

a short-term toxicity study does not need to be conducted because exposure of humans via the dermal route in production and/or use is not likely as based on the provided thorough and rigorous exposure assessment

Critical effects observed:

not specified

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Nagano et al 2011, conducted also a 2 -year carcinogenicity study on ITO in the rat and mouse to OECD Guideline 451. Fifty mice of both sexes were exposed to ITO at 0 (control), 0.01, 0.03 or 0.1 mg/m3 for 6h/day, 5day/wk for 104wk, and 50 rats of both sexes were exposed to 0, 0.01 or 0.03 mg/m3 ITO for the same time period. The repeated exposure of 50 rats of both sexes to 0.1 mg/m3 ITO was discontinued at the 26th week, followed by clean air exposure for the remaining 78wk. In rats, incidences of bronchiolo-alveolar adenomas and carcinomas, bronchiolo-alveolar hyperplasia, alveolar wall fibrosis and thickened pleural wall, alveolar proteinosis and infiltrations of alveolar macrophages and inflammatory cells were significantly increased. Combined incidences of malignant lung tumours in male rats and total lung tumours in male and female rats were significantly increased at exposure to 0.01 mg/m3 ITO. In mice, no carcinogenic response occurred, but thickened pleural wall, alveolar proteinosis and alveolar macrophage infiltration were induced. Mice were less susceptible to ITO than rats. The lung content of indium was the greatest, followed by the spleen, kidney and liver. Increases in blood indium levels were dose-dependent. There was clear evidence that inhaled ITO was carcinogenic in male and female rats but no clear evidence in mice, together with occurence of chronic pulmonary lesions in both rats and mice.

Justification for classification or non-classification

The results of the repeat dose whole body inhalation studies indicate that both indium oxide and indium tin oxide would receive a specific target organ toxicity repeat exposure (STOT-RE) classification, category 1 according to the EU CLP criteria (EU 1272/2008) as 'significant' effects (those that clearly indicate functional disturbance or morphological changes) were observed at or < 0.02 mg/L/6h/d (20 mg/m3/6h/d)

Based upon read across to Indium oxide (In203) repeated dose toxicity inhalation data and according to Regulation (EC) No 1272/2008, Indium hydroxide would require a specific target organ toxicity repeat exposure (STOT-RE) classification, category 1