Chromium (III) oxide

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

28 April to 21 May 2009

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2009

Report date:

2009

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Version / remarks:

1981-05-12

GLP compliance:

yes

Test type:

standard acute method

Limit test:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Chromium (III) oxide

EC Number:

215-160-9

EC Name:

Chromium (III) oxide

Cas Number:

1308-38-9

Molecular formula:

Cr2O3

IUPAC Name:

chromium (III) oxide

Details on test material:

Purity = 99.1%
Physical condition; green powder
Storage; room temperature

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: sealed container, at room temperature

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

The animals were male and female Han Wistar rats, obtained from Harlan UK Ltd. The animals were weight matched to 200 g ± 15% on arrival and were less than 12 weeks of age at the start of the study.
The animals were housed in groups of five. The room provided a minimum of 15 air changes per hour, temperature was maintained at 19 to 25°C and relative humidity was maintained at 40 to 70 %. The animals were removed from this environment during acclimatisation to tube restraint and during test article exposure. Fluorescent lighting was provided on a 12 hour light/dark cycle.
The rats were provided with wooden 'Aspen' chew blocks as enrichment. They were fed SQC Rat and Mouse Maintenance Diet No.1, Expanded (SDS Ltd., UK) ad libitum. Mains water was provided ad libitum.
All animals were examined for ill health on arrival. They underwent 9 days acclimatisation, the final 3 days of which they underwent acclimatisation to restraint tubes.

Administration / exposure

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

air

Mass median aerodynamic diameter (MMAD):

2.22 µm

Geometric standard deviation (GSD):

2.36

Remark on MMAD/GSD:

88.3 - 89.8 % ofthe particles were below 3.5 μm in diameter.

Details on inhalation exposure:

TEST ATMOSPHERE / CHAMBER DESCRIPTION
- System of generating particulates/aerosols: test aerosol was generated from chromium (III) oxide using a Rotating Brush Generator that fed into a flow-through (nose-only) exposure chamber with an internal volume of approximately 40 L. The air flow was 35 L/min and was sufficient to provide a minimum of 12 air changes per hour.
- Method of particle size determination: the particle size distribution of the aerosol was measured gravimetrica!ly using a Marple 298 Cascade impactor by sampling the aerosol from inside the chamber at a flow rate of 2L/min. The weight of test article collected on each weighed substrate was used to calculate the mass median aerodynamic diameter and geometric standard deviation. A total of three samples were collected during exposure.
- Temperature, humidity, pressure in air chamber: the temperature, relative hurnidity, air flow and oxygen concentration inside the exposure chamber were monitored continuously and recorded approximately hourly during the animal exposure.
During the animal exposure the mean temperature and relative humidity within the chamber were 21.5 ± 0.283 °C and 10.9 ± 0.150 % respectively. The low relative humidity was due to a combination of the dried air supply necessary for the consistent aerosol generation of a powder and the effect of the dry powder aerosol itself. The low humidity level is to be expected with a dry powder aerosol and has no detrimental effect on the outcome ofthe study. Oxygen concentration remained stable at 20.9 % v/v throughout the animal exposure. The air flow was 35 L/min and was sufficient to provide a minimum of 12 air changes/hour.

TEST ATMOSPHERE
- Brief description of analytical method used: the achieved aerosol concentration in the exposure chamber was measured gravimetrically prior to and at approximately half-hourly intervals throughout the exposure.
During the exposure additional aerosol samples were taken for the purposes of monitoring aerosol stability when the aerosol generator was changed once the powder reservoir in the generator was depleted.
The chamber aerosol concentration was sampled onto weighed glass-fibre filters. After sampling (ca 1 L/min), the filters were then re-weighed. U sing the collected weight and volume of air sampled, the gravimetric chamber aerosol concentration was calculated.
- Samples taken from breathing zone: yes

The rats had Vaseline petroleum jelly smeared over their closed eyelids prior to test article exposure as a precautionary measure to avoid adverse irritant effects to the eye.GENERATION OF

Analytical verification of test atmosphere concentrations:

yes

Remarks:

The achieved aerosol concentration was measured gravimetrically prior to and at approximately half-hourly intervals throughout the exposure.

Duration of exposure:

4 h

Concentrations:

Nominal concentration = 17.6 mg/L.
Mean achieved concentration = 5.41 ± 0.744 mg/L, with a range of 4.57 to 6.84 mg/L.

No. of animals per sex per dose:

5 males / 5 females

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: all animals were observed daily (for 14 days post-exposure) for signs of ill health or overt toxicity. Animals were observed approximately hourly during the exposure period and for the remainder of the exposure day. Individual body weights were recorded before and after exposure on Day 1, and on Days 2, 8 and 15. Additional body weights were recorded on Days 3, 4 and 5.
- Necropsy of survivors performed: all animals were subject to a gross necropsy. The gross necropsy procedure included inspection of the nasal cavity and respiratory tract.

Statistics:

Not performed.

Results and discussion

Preliminary study:

Not applicable.

Effect levels

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 5.41 mg/L air (analytical)

Based on:

test mat.

Exp. duration:

4 h

Mortality:

No animals died during the study.

Clinical signs:

other: Adverse treatment related clinical signs were increased breathing rate in 4 females and 2 males during exposure, and hunched posture in one female. No adverse clinical signs were observed immediately following exposure or during the remainder of the obser

Body weight:

All animals lost body weight during exposure, but regained their pre-exposure body weight by day 5. As a result of the initial loss, the body weight gain seen during the first week of the study was less than expected for most animals of this age and strain. Animals generally gained more weight during the second week (especially females) and weight gain during this week was more comparable with other rats of this strain and age.

Gross pathology:

Macroscopic findings included green areas in the lung and lymph nodes in the majority of animals. Reddened nasal cavity, mandibular lymph nodes and thymus were also noted in several animals. One animal had a pale urinary bladder, however this was not considered to be treatment-related.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

LC50 (rats; 4 hours) > 5.41 mg/L air (actual concentration)
According to the EC-Regulation 1272/2008 and subsequent regulations, the test item is not classified as acute toxic via the inhalation route.

Executive summary:

Male and female Han Wistar rats underwent a single 4 hour nose-only inhalation exposure to chromium (III) oxide at a mean atmospheric exposure level of 5.41 mg/L. Exposure to the test compound was well tolerated and no mortalities occurred. Clinical signs were limited to increased breathing rate during exposure. Adverse clinical signs did not persist into the 14 day observation period. Necropsy revealed green staining in the lung and lymph nodes and reddening of the nasal cavity and mandibular lymph nodes. The LC50 is therefore considered to be in excess of 5.41 mg/L.