Digadolinium trioxide

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

from 2016-08-24 to 2016-11-22

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2016

Report date:

2016

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 436 (Acute Inhalation Toxicity: Acute Toxic Class Method)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.1300 (Acute inhalation toxicity)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test type:

acute toxic class method

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Digadolinium trioxide

EC Number:

235-060-9

EC Name:

Digadolinium trioxide

Cas Number:

12064-62-9

Molecular formula:

Gd2O3

IUPAC Name:

Digadolinium trioxide

Test material form:

solid: particulate/powder

Details on test material:

- Name of test material (as cited in study report): digadolinium trioxide
- Physical state: solid
- Appearance: white powder

Specific details on test material used for the study:

- Treatment of test material prior to testing: the test item was used as supplied
- With a correction factor of 1.002, no correction was done during formulation preparation

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: 3 male and 3 female rats, CRL:(WI) rats; Charles River Laboratories, Research Models and Services, Germany GmbH, Sandhofer Weg 7, D97633 Sulzfeld
- Females (if applicable) nulliparous and non-pregnant: yes
- Age at dosing: 12 weeks
- Weight at dosing: 437-449 g (males) and 250-254 g (females)
- Fasting period before study: no data
- Housing: Group of 3 (by sex) in type III polypropylene solid floor cages with stainless steel mesh lids. Lignocel Bedding for Laboratory Animals and Arbocel nesting material were available to animals during the study. Rodents were housed with deep wood sawdust bedding to allow digging and other normal rodent activities.
- Diet (e.g. ad libitum): ad libitum, the animals were provided with ssniff SM R/M “Autoclavable Complete Feed for Rats and Mice – Breeding and Maintenance” (ssniff Spezialdiäten GmbH, D-59494 Soest Germany; batch: 278 5652; expiry: November 2016)
- Water (e.g. ad libitum): ad libitum, tap water fit for human consumption
- Acclimation period: 34 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19.1 - 25.9 °C
- Humidity (%): 39 - 86%
- Air changes (per hr): 15-20 air exchanges/hour
- Photoperiod (hrs dark / hrs light): 12/12, light from 6.00 a.m. to 6.00 p.m.

Administration / exposure

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

air

Mass median aerodynamic diameter (MMAD):

3.64 µm

Geometric standard deviation (GSD):

2.03

Remark on MMAD/GSD:

inhalable fraction (% < 4µm): 55.3%

Details on inhalation exposure:

TECHNICAL TRIALS
- Prior to animal exposures, test material atmospheres were generated within the exposure chamber. During these technical trials, air-flow settings and test material input rates were varied to achieve the required atmospheric characteristics.

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- 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 two, 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, under positive pressure, it was distributed to the individual exposure ports.
- 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 nares to enter the exposure port.
- Source and rate of air: Compressed air was supplied by means of an oil-free compressor passed through a suitable filter system prior to introduction to the nebuliser. The flow of air through each port was at least 0.7 L/min. This flow rate was considered adequate to minimise re-breathing of the test atmosphere as it is about twice the respiratory minute volume of a rat.
- System of generating particulates/aerosols: The test item was aerosolised using Palas RBG1000 (Palas GmbH, Karlsruhe, Germany) located at the top of the exposure chamber. The rate of formulation use was controlled by the rotation speed. Compressed air was supplied by means of an oil-free compressor passed through a suitable filter system prior to introduction to the nebuliser.
- Method of particle size determination: The particle size of the test atmosphere was 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 the 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 0.55, 0.96, 1.55, 2.11, 3.56, 6.66 and 10.55 µm was calculated. From these data, using software supplied with the impactor, the Mass Median Aerodynamic diameter (MMAD), and Geometric Standard Deviation (GSD) were calculated. In addition, the proportion (%) of aerosol less than 4 µm (considered to be the inhalable portion) was determined.
- Treatment of exhaust air: After passing through the breathing zone, used aerosol entered the outer cylinder from where it was exhausted through a suitable filter system. Atmosphere generation was therefore dynamic.
- Temperature, humidity, pressure in air chamber: 23.5 °C (22.0 - 24.1 °C), 1.9% (1.6 - 2.1 %) relative humidity

TEST ATMOSPHERE
- 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 (Whatman GmbH, Hahnestraße 3 – D-37586 Dassel, Germany).
- The difference in the pre- and post-sampling weights, divided by the volume of atmosphere sampled, was equal to the actual achieved test atmosphere concentration. The nominal concentration was calculated by dividing the mass of test material disseminated into the chamber by the total volume of air that went through the chamber during the same period.

CLASS METHOD (if applicable)
- Rationale for the selection of the starting concentration: no data

Analytical verification of test atmosphere concentrations:

yes

Remarks:

gravimetrical determination

Duration of exposure:

4 h

Concentrations:

5 mg/L (nominal concentration)

No. of animals per sex per dose:

3 males and 3 females

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing:
- Morbidity/mortality: Animals were checked hourly during exposure, one hour after exposure and twice daily (early and late in the working day) during the 14-day observation period;
- Clinical signs: All animals were observed for clinical signs at hourly intervals during exposure, as soon as practically possible following removal from restraint at the end of exposure, one hour after exposure and subsequently once daily for fourteen days;
- Body weight: Individual body weights were recorded prior to treatment on the day of exposure (Day 0) and on Days 1, 3, 7 and 14.
- Necropsy of survivors performed: Yes. At the end of the 14-day observation period, the animals were euthanised by exsanguination under anaesthesia (intra-peritoneal injection of pentobarbital solution – Euthanimal 40%) and gross macroscopic examination was performed. All animals were subject to a gross necropsy which included a detailed examination of the abdominal and thoracic cavities. Special attention was given to the respiratory tract for macroscopic signs of irritancy or local toxicity.

Statistics:

No data

Results and discussion

Effect levels

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 5.04 mg/L air (analytical)

Based on:

test mat.

Exp. duration:

4 h

Mortality:

0/3 for males
0/3 for females

Clinical signs:

other: Wet fur, fur staining was recorded mostly on the day of exposure. These observations were considered to be related to the restraint and exposure procedures and, in isolation, were considered not to be biologically significant. Laboured respiration (slight

Body weight:

The exposure procedure caused slight body weight loss in the animals (1.0% - 6.0%). After day 3, normal body weight gain was observed.

Gross pathology:

A single four hour nose-only exposure of digadolinium trioxide to CRL: (WI) Wistar rats dosed at 5.04 mg/L, with a 14-day observation period, was not associated with any test item-related gross changes.

Other findings:

No data

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

Under the experimental conditions of the study, no deaths occurred in a group of six rats exposed to the concentration of 5.04 mg/L for four hours. The acute inhalation median lethal concentration (4-h LC50) of digadolinium trioxide, in CRL: (WI) Wistar strain rats, was therefore considered to be greater than 5.04 mg/L. Based on these results, the test substance is considered not classified as acute toxicant via inhalation according to CLP Regulation.