Chromium (III) oxide

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

not specified

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

The study is generally well documented and meets generally accepted scientific standards. A number of methodological or reporting deficiencies when comparing the publications with the relevant OECD TG 413 (1981): the guideline foresees that if recovery from test item-related effects is investigated, this may be done in a separate group of animals (10 animals/sex) given the highest dose and observing these animals during a post-treatment period of normally 28 days. In this study five animals of the regular high dose group were kept for a post-exposure group lasting 13 weeks; exposure parameters were not recorded( oxygen content, air flow, temperature, humidity); uncertainty, if equilibration of the chamber concentration was checked; clinical observations during exposure were not recorded; food consumption measurements were missing; haematological, clinical chemistry, and urinalysis parameters were not defined (only statement that these investigations were carried out); histopathological examination was not defined, but it was stated by the author that tissues harvested for this type of study were examined; historical and individual data were missing; exposure apparatus was not described in detail; unclear if actual concentration was measured in the animal's breathing zone

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Reference

Endpoint:

fertility, other

Remarks:

90-day inhalation study with histopathology of reproduction organs and sperm evaluations

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

not specified

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

significant methodological deficiencies

Remarks:

Several methodological deficiencies from the OECD 413 (1981) guideline were noted: the guideline foresees that if recovery from test item-related effects is investigated, this may be done in a separate group of animals (10 animals/sex) given the highest dose and observing these animals during a post-treatment period of normally 28 days. In this study five animals of the regular high dose group were kept for a post-exposure group lasting 13 weeks; exposure parameters were not recorded( oxygen content, air flow, temperature, humidity); uncertainty, if equilibration of the chamber concentration was checked; clinical observations during exposure were not recorded; food consumption measurements were missing; haematological, clinical chemistry, and urinalysis parameters were not defined (only statement that these investigations were carried out); histopathological examination was not defined, but it was stated by the author that tissues harvested for this type of study were examined; historical and individual data were missing; exposure apparatus was not described in detail; unclear if actual concentration was measured in the animal's breathing zone

Reason / purpose for cross-reference:

reference to same study

Qualifier:

equivalent or similar to guideline

Guideline:

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

Version / remarks:

1981-05-12

Deviations:

yes

Remarks:

please refer to the remarks field of the field "Rationale reliability incl. deficienceis " above

GLP compliance:

not specified

Remarks:

not specified in the publication

Limit test:

no

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source of test material: British Chrome Chemicals (Orlay Nook, Eaglescliffe, Cleveland, U.K.)

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: test article was stored in separate, unused 1-m³ chambers that were continuously purged with a low flow of dry compressed air.

Species:

rat

Strain:

other: CDF (Fischer 344)/Crl BR VAF/Plus

Details on species / strain selection:

not specified

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories (Raleigh, NC)
- Age at study initiation: 7 weeks of age
- Housing: housed in groups for three days and then individually housed in stainless steel, suspended wire-mesh cages
- Diet (ad libitum): commercial laboratory feed (Purina Certified Rodent Chow No. 5002)
- Water (ad libitum): tap water

ENVIRONMENTAL CONDITIONS
- Temperature: 21 ± 2 °C
- Relative humidity: 43 ± 11%
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

inhalation: dust

Type of inhalation exposure (if applicable):

nose only

Mass median aerodynamic diameter (MMAD):

>= 1.8 - <= 1.9 µm

Remarks on MMAD:

GSD (range): 1.78 - 1.93

Vehicle:

air

Details on exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: rats were exposed in stainless steel and acrylic nose-only inhalation chambers operated with at least 12 chamber air changes per hour.

- System of generating particulates/aerosols: generation of chromic oxide particles was accomplished with a modified low-output dust generator, using spinning glass beads over a packed cake of test material.

- Method of particle size determination: particle-size measurements were made from each exposure level using a cascade impactor once per day for the first two weeks
and weekly thereafter.

TEST ATMOSPHERE
- Brief description of analytical method used: chamber samples were determined once per hour by standard gravimetric methods, with periodic analysis for Cr(III) and Cr(VI).

Details on mating procedure:

not applicable

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Please refer to the field "Details on exposure" above.

Duration of treatment / exposure:

13 consecutive weeks

Frequency of treatment:

6 hours/day, 5 days/week for 65 exposure days

Details on study schedule:

not specified

Dose / conc.:

4.4 mg/m³ air (analytical)

Remarks:

SD: 0.23

Dose / conc.:

15 mg/m³ air (analytical)

Remarks:

SD: 1.2

Dose / conc.:

44 mg/m³ air (analytical)

Remarks:

SD: 3.7

No. of animals per sex per dose:

Main study: 15 animals/sex/dose

Control animals:

yes

Details on study design:

- Dose selection rationale: the desired exposure levels were selected to be multiples of the threshold limit value (TLV) for trivalent chromium and set at chromium equivalents of 3, 10, and 30 mg/m³.
- Post-exposure recovery period (main study): 5 males and 5 females from each group were maintained for an additional 13-week recovery period during which time they received no additional exposures.

Positive control:

none

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule:
daily prior to and following each exposure
- Cage side observations checked: clinical signs

- Time schedule: twice daily during the recovery period and on weekends
- Cage side observations checked: morbidity and mortality

DETAILED CLINICAL OBSERVATIONS: Not specified

BODY WEIGHT: Yes
- Time schedule for examinations:
weekly during the exposure and recovery periods

FOOD CONSUMPTION AND COMPOUND INTAKE:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Not specified
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: Not specified

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: Not specified

WATER CONSUMPTION AND COMPOUND INTAKE: Not specified

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations:
during the acclimation period and prior to terminal necropsy

HAEMATOLOGY: Yes
- Anaesthetic used for blood collection: Not specified
- Animals fasted: Yes, water available
- How many animals:
10 per sex per group, designated for necropsy at the end of exposures
At necropsy, bone marrow smears were prepared and differential cell counts were evaluated.

CLINICAL CHEMISTRY: Yes
- Animals fasted: Yes, water available
- How many animals:
10 per sex per group, designated for necropsy at the end of exposures

URINALYSIS: Yes
- Metabolism cages used for collection of urine: Yes, overnight
- Animals fasted: Not specified
- How many animals: 10 per sex per group, designated for necropsy at the end of exposures
Urinalysis determinations were performed by gross observation, microscopy, and automated clinical analyzer.
Following urinalysis testing, aliquots of the remaining urine from 5 animals per sex from the control group, and the high-exposure level groups for both test articles were submitted for Beta2-microglobulin analysis.

NEUROBEHAVIOURAL EXAMINATION: Not specified
IMMUNOLOGY: Not specified

Oestrous cyclicity (parental animals):

not specified

Sperm parameters (parental animals):

At necropsy, sperm samples from the left caudal epididymis of 10 males per group were used for automated evaluation of sperm motility, count, and morphology. The concentration and morphology of the sperm were evaluated using visual methods. Two hundred intact sperm were evaluated from each animal for morphology. Intact sperm were evaluated as
normal or abnormal. The number of disarticulated sperm in each field was also assessed.

Litter observations:

not specified

Postmortem examinations (parental animals):

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Animals found dead or euthanized by design at study termination were necropsied. At necropsy the heart, lungs, liver, spleen, kidneys, brain, adrenal glands, thyroid/parathyroid glands, testes, and ovaries were weighed. Tissues typically harvested for subchronic studies were also removed and preserved. Microscopic evaluation was conducted on all hematoxylin and eosin-stained tissues from the control and high-exposure level groups. The kidneys, liver, nasal tissue, trachea, lungs, larynx, mediastinal and mandibular lymph nodes, and gross lesions from all animals in the low- and mid-exposure level groups were also examined.

Postmortem examinations (offspring):

not specified

Statistics:

One-way analysis of variance on body weights, clinical pathology laboratory tests, and organ weights. If the result was significant, Bartlett's test for homogeneity of variance was performed. If Bartlett's test was non-significant, Dunnett's t-test was used for pairwise comparisons. If Barlett's test was significant, the Welch t-test with Bonferroni correction was used for pairwise comparisons. The Kruskal-Wallis analysis of variance, followed where appropriate by Mann-Whitney test was used for those parameters where parametric analysis was inappropriate. The level for statistical significance was set at p ≤ 0.05.

Offspring viability indices:

not specified

Clinical signs:

no effects observed

Dermal irritation (if dermal study):

not specified

Mortality:

mortality observed, non-treatment-related

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

not specified

Food efficiency:

not specified

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

not specified

Ophthalmological findings:

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not specified

Immunological findings:

not specified

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

not specified

Other effects:

not specified

Reproductive function: oestrous cycle:

not specified

Reproductive function: sperm measures:

no effects observed

Reproductive performance:

not specified

MORTALITY
- 4.4, 15 and 44 mg/m³: no compound-related mortalities occurred during the conduct of this study. Some animals died on exposure day 1 as a direct result of the restraint tubes, and they were replaced.

BODY WEIGHT AND WEIGHT CHANGES:
- 4.4, 15 and 44 mg/m³: male and female mean body weights during exposures to chromic oxide were not statistically different from the control group's mean body weights in any week. Mean body weights of males exposed to the high concentration of chromic oxide were slightly lower than controls during the recovery period but weight gains for these animals were similar to controls.

OPHTHALMOLOGIC FINDINGS:
- 4.4, 15 and 44 mg/m³: no exposure-related effects were noted in the ophthalmologic evaluations.

HAEMATOLOGICAL FINDINGS:
- 4.4, 15 and 44 mg/m³: after 13 weeks of exposure, none of the exposure groups, for either sex, exhibited a statistically significant difference from the control group for any hematological parameters.

CLINICAL CHEMISTRY:
- 4.4, 15 and 44 mg/m³: after 13 weeks of exposure, none of the exposure groups, for either sex, exhibited a statistically significant difference from the control group for any serum biochemical parameters.

URINALYSIS FINDINGS:
- 4.4, 15 and 44 mg/m³: after 13 weeks of exposure, none of the exposure groups, for either sex, exhibited a statistically significant difference from the control group for any urinalysis parameters. Beta- microglobulins were not detected in urine samples from any group.

ORGAN WEIGHT FINDINGS:
- 4.4, 15 and 44 mg/m³: Slight, yet statistically significant increases in mean absolute and relative lung/trachea weights occurred in high-exposure-level group males. Macroscopic and histologic changes were present to explain these organ weight changes. Lung weights were not affected in females. Other statistically significant increases were observed in the mean absolute and relative thyroid/parathyroid weights in the mid-exposure-group females and in the mean relative thyroid/parathyroid/body weight ratios in the high-exposure-group females. These organ weight changes were very small. At the recovery sacrifice, organ weights of all the exposure groups were comparable to the control group.

GROSS PATHOLOGICAL FINDINGS:
- 4.4, 15 and 44 mg/m³: exposure-related macroscopic findings at the terminal and recovery sacrifices were observed in the lungs and mediastinal lymph nodes of most animals in this study. Green lung discoloration was observed in animals exposed to chromic oxide at all exposure levels.
The degree of discoloration increased with exposure level and was present both at the terminal and recovery sacrifices. Similar discoloration was observed in the mediastinal lymph nodes of animals exposed to chromic oxide (terminal and recovery sacrifices).
Mediastinal lymph-node enlargement was observed at the recovery sacrifice in animals exposed to chromic oxide (high exposure only).
Additional macroscopic observations were few in number and considered incidental.

HISTOPATHOLOGICAL FINDINGS: NON-NEOPLASTIC
- 4.4, 15 and 44 mg/m³:
1) Terminal sacrifice: randomly distributed foci or aggregates of pigmented macrophages filled with dense black pigment were observed within alveolar spaces adjacent to the junctions of terminal bronchioles and alveolar ducts and subjacent to the pleura in males and females from all chromic-oxide treatment
groups. Similar black pigment was also observed at the tracheal bifurcation, in the peribronchial lymphoid tissue, and within the mediastinal lymph node. The pigment stained black with hematoxylin and eosin stain and was presumed to represent the test article. The presence of the pigment corresponded to the green discoloration seen macroscopically. Trace to mild chronic interstitial inflammation of the lung, characterized by an infiltration of inflammatory cells, was observed in alveolar septa surrounding aggregates of pigmented macrophages in some mid-exposure and high-exposure level males and females. Chronic interstitial inflammation was accompanied by septal cell hyperplasia (Type II pneumocytes) in some mid- and high-exposure level males. The microscopic changes were
generally associated with the pigment and corresponded to the increased lung weight observed for the males in the high-exposure-level group. Lymphoid hyperplasia of the node was also present in all exposure groups. No test article-related lesions were seen in the nasal cavities of animals exposed to chromic oxide at any exposure level.

2) Recovery sacrifice: in the lung, trace to mild pigmented macrophages and black pigment in the peribronchial lymphoid tissue persisted in all treatment groups, males and females, at approximately equal incidence and severity, as seen in the terminal-sacrifice animals. Trace to mild septal cell hyperplasia and trace to mild chronic interstitial inflammation persisted in males of all treatment groups and females in the mid- and high-exposure-level groups. These lesions were the same or slightly increased in severity as compared to the terminal-sacrifice groups. Trace to mild black pigment also persisted in mediastinal lymph nodes in all exposure groups, with an apparent increase in incidence in some males in the two lowest-exposure groups as compared to the terminal-sacrifice group,
suggesting pulmonary clearance via the lymphatic system. Most of the pathologic changes observed at the recovery sacrifice were of minimal severity.

REPRODUCTIVE PERFORMANCE:
- 4.4, 15 and 44 mg/m³: no exposure-related effects were noted for sperm motility, morphology, or concentration.

Dose descriptor:

NOAEL

Sex:

male

Remarks on result:

not determinable due to absence of adverse toxic effects

Critical effects observed:

not specified

Clinical signs:

not specified

Dermal irritation (if dermal study):

not specified

Mortality / viability:

not specified

Body weight and weight changes:

not specified

Food consumption and compound intake (if feeding study):

not specified

Food efficiency:

not specified

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

not specified

Ophthalmological findings:

not specified

Haematological findings:

not specified

Clinical biochemistry findings:

not specified

Urinalysis findings:

not specified

Sexual maturation:

not specified

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

not specified

Histopathological findings:

not specified

Other effects:

not specified

Behaviour (functional findings):

not specified

Developmental immunotoxicity:

not specified

Ophthalmological findings:

not specified

Reproductive effects observed:

not specified

Conclusions:

Inhalation exposure to chromium oxide dust in this study did not have any adverse effects on sperm parameters.

Data source

Reference

Reference Type:

publication

Title:

Thirteen-week subchronic rat inhalation toxicity study with a recovery phase of trivalent chromium compounds, chromic oxide, and basic chromium sulfate.

Author:

Derelanko, M.J., Rinehart, W.E., Hilaski, R.J., Thompson, R.B. &, Löser, E.

Year:

1999

Bibliographic source:

Toxicological Sciences 52: 278-288

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

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

Version / remarks:

1981-05-12

Deviations:

yes

Remarks:

please refer to the remarks field of the field "Rationale reliability incl. deficienceis " above

GLP compliance:

not specified

Remarks:

not specified in the publication

Limit test:

no

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

Test material form:

solid: particulate/powder

Details on test material:

- State of aggregation: dark green powders

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source of test material: British Chrome Chemicals (Orlay Nook, Eaglescliffe, Cleveland, U.K.)

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: test article was stored in separate, unused 1-m³ chambers that were continuously purged with a low flow of dry compressed air.

Test animals

Species:

rat

Strain:

other: CDF (Fischer 344)/Crl BR VAF/Plus

Details on species / strain selection:

not specified

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories (Raleigh, NC)
- Age at study initiation: 7 weeks of age
- Housing: housed in groups for three days and then individually housed in stainless steel, suspended wire-mesh cages
- Diet (ad libitum): commercial laboratory feed (Purina Certified Rodent Chow No. 5002)
- Water (ad libitum): tap water


ENVIRONMENTAL CONDITIONS
- Temperature: 21 ± 2 °C
- Relative humidity: 43 ± 11%
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

inhalation: dust

Type of inhalation exposure:

nose only

Vehicle:

air

Mass median aerodynamic diameter (MMAD):

>= 1.8 - <= 1.9 µm

Remarks on MMAD:

GSD (range): 1.78 - 1.93

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: rats were exposed in stainless steel and acrylic nose-only inhalation chambers operated with at least 12 chamber air changes per hour.

- System of generating particulates/aerosols: generation of chromic oxide particles was accomplished with a modified low-output dust generator, using spinning glass beads over a packed cake of test material.

- Method of particle size determination: particle-size measurements were made from each exposure level using a cascade impactor once per day for the first two weeks and weekly thereafter.

TEST ATMOSPHERE
- Brief description of analytical method used: chamber samples were determined once per hour by standard gravimetric methods, with periodic analysis for Cr(III) and Cr(VI).

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Please refer to the field "Details on inhalation exposure" above.

Duration of treatment / exposure:

Main study: 13 consecutive weeks
Bronchoalveolar lavage parameters: 5 consecutive days

Frequency of treatment:

Main study: 6 hours/day, 5 days/week for 65 exposure days

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

4.4 mg/m³ air (analytical)

Remarks:

SD: 0.23

Doses / concentrations 2

Dose / conc.:

15 mg/m³ air (analytical)

Remarks:

SD: 1.2

Doses / concentrations 3

Dose / conc.:

44 mg/m³ air (analytical)

Remarks:

SD: 3.7

No. of animals per sex per dose:

Main study: 15 animals/sex/dose
Bronchoalveolar lavage evaluation: 5 animals/sex/dose

Control animals:

yes

Details on study design:

- Dose selection rationale: the desired exposure levels were selected to be multiples of the threshold limit value (TLV) for trivalent chromium and set at chromium equivalents of 3, 10, and 30 mg/m³.
- Post-exposure recovery period (main study): 5 males and 5 females from each group were maintained for an additional 13-week recovery period during which time they received no additional exposures.

Positive control:

not specified

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily prior to and following each exposure
- Cage side observations checked: clinical signs

- Time schedule: twice daily during the recovery period and on weekends
- Cage side observations checked: morbidity and mortality

DETAILED CLINICAL OBSERVATIONS: Not specified

BODY WEIGHT: Yes
- Time schedule for examinations: weekly during the exposure and recovery periods

FOOD CONSUMPTION AND COMPOUND INTAKE:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Not specified
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: Not specified

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: Not specified

WATER CONSUMPTION AND COMPOUND INTAKE: Not specified

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: during the acclimation period and prior to terminal necropsy

HAEMATOLOGY: Yes
- Anaesthetic used for blood collection: Not specified
- Animals fasted: Yes, water available
- How many animals: 10 per sex per group, designated for necropsy at the end of exposures
At necropsy, bone marrow smears were prepared and differential cell counts were evaluated.

CLINICAL CHEMISTRY: Yes
- Animals fasted: Yes, water available
- How many animals: 10 per sex per group, designated for necropsy at the end of exposures

URINALYSIS: Yes
- Metabolism cages used for collection of urine: Yes, overnight
- Animals fasted: Not specified
- How many animals: 10 per sex per group, designated for necropsy at the end of exposures
Urinalysis determinations were performed by gross observation, microscopy, and automated clinical analyzer.
Following urinalysis testing, aliquots of the remaining urine from 5 animals per sex from the control group, and the high-exposure level groups for both test articles were submitted for Beta2-microglobulin analysis.

NEUROBEHAVIOURAL EXAMINATION: Not specified
IMMUNOLOGY: Not specified

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Animals found dead or euthanized by design at study termination were necropsied. At necropsy the heart, lungs, liver, spleen, kidneys, brain, adrenal glands, thyroid/parathyroid glands, testes, and ovaries were weighed. Tissues typically harvested for subchronic studies were also removed and preserved. Microscopic evaluation was conducted on all hematoxylin and eosin-stained tissues from the control and high-exposure level groups. The kidneys, liver, nasal tissue, trachea, lungs, larynx, mediastinal and mandibular lymph nodes, and gross lesions from all animals in the low- and mid-exposure level groups were also examined.

Other examinations:

BRONCHOALVEOLAR LAVAGE EVALUATION:
Rats were anesthetized and the lungs, heart, trachea, larynx, and tongue were removed en-block. Following tracheal cannulation, the airways were washed with warmed, physiological saline and the resulting BALF was pooled. Nucleated cell counts were performed using a Neubauer hemocytometer, and cell differential counts were performed on Wright-Giemsa-stained smears. Chemical analyses performed spectrophotometrically included for lactate dehydrogenase (LDH), total protein, beta-glucuronidase, and glutathione reductase.

Statistics:

One-way analysis of variance on body weights, clinical pathology laboratory tests, BALF data and organ weights. If the result was significant, Bartlett's test for homogeneity of variance was performed. If Bartlett's test was non-significant, Dunnett's t-test was used for pairwise comparisons. If Barlett's test was significant, the Welch t-test with Bonferroni correction was used for pairwise comparisons. The Kruskal-Wallis analysis of variance, followed where appropriate by Mann-Whitney test was used for those parameters where parametric analysis was inappropriate. The level for statistical significance was set at p ≤ 0.05.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

mortality observed, non-treatment-related

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

not specified

Food efficiency:

not specified

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

not specified

Ophthalmological findings:

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not specified

Immunological findings:

not specified

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Neuropathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

not specified

Other effects:

no effects observed

Details on results:

MORTALITY
- 4.4, 15 and 44 mg/m³: no compound-related mortalities occurred during the conduct of this study. Some animals died on exposure day 1 as a direct result of the restraint tubes, and they were replaced.

BODY WEIGHT AND WEIGHT CHANGES:
- 4.4, 15 and 44 mg/m³: male and female mean body weights during exposures to chromic oxide were not statistically different from the control group's mean body weights in any week. Mean body weights of males exposed to the high concentration of chromic oxide were slightly lower than controls during the recovery period but weight gains for these animals were similar to controls.

OPHTHALMOLOGIC FINDINGS:
- 4.4, 15 and 44 mg/m³: no exposure-related effects were noted in the ophthalmologic evaluations.

HAEMATOLOGICAL FINDINGS:
- 4.4, 15 and 44 mg/m³: after 13 weeks of exposure, none of the exposure groups, for either sex, exhibited a statistically significant difference from the control group for any hematological parameters.

CLINICAL CHEMISTRY:
- 4.4, 15 and 44 mg/m³: after 13 weeks of exposure, none of the exposure groups, for either sex, exhibited a statistically significant difference from the control group for any serum biochemical parameters.

URINALYSIS FINDINGS:
- 4.4, 15 and 44 mg/m³: after 13 weeks of exposure, none of the exposure groups, for either sex, exhibited a statistically significant difference from the control group for any urinalysis parameters. Beta- microglobulins were not detected in urine samples from any group.

ORGAN WEIGHT FINDINGS:
- 4.4, 15 and 44 mg/m³: Slight, yet statistically significant increases in mean absolute and relative lung/trachea weights occurred in high-exposure-level group males. Macroscopic and histologic changes were present to explain these organ weight changes. Lung weights were not affected in females. Other statistically significant increases were observed in the mean absolute and relative thyroid/parathyroid weights in the mid-exposure-group females and in the mean relative thyroid/parathyroid/body weight ratios in the high-exposure-group females. These organ weight changes were very small. At the recovery sacrifice, organ weights of all the exposure groups were comparable to the control group.
Please also refer to the field "Any other information on results incl. tables" below.

GROSS PATHOLOGICAL FINDINGS:
- 4.4, 15 and 44 mg/m³: exposure-related macroscopic findings at the terminal and recovery sacrifices were observed in the lungs and mediastinal lymph nodes of most animals in this study. Green lung discoloration was observed in animals exposed to chromic oxide at all exposure levels.
The degree of discoloration increased with exposure level and was present both at the terminal and recovery sacrifices. Similar discoloration was observed in the mediastinal lymph nodes of animals exposed to chromic oxide (terminal and recovery sacrifices).
Mediastinal lymph-node enlargement was observed at the recovery sacrifice in animals exposed to chromic oxide (high exposure only).
Additional macroscopic observations were few in number and considered incidental.

HISTOPATHOLOGICAL FINDINGS: NON-NEOPLASTIC
- 4.4, 15 and 44 mg/m³:
1) Terminal sacrifice: randomly distributed foci or aggregates of pigmented macrophages filled with dense black pigment were observed within alveolar spaces adjacent to the junctions of terminal bronchioles and alveolar ducts and subjacent to the pleura in males and females from all chromic-oxide treatment
groups. Similar black pigment was also observed at the tracheal bifurcation, in the peribronchial lymphoid tissue, and within the mediastinal lymph node. The pigment stained black with hematoxylin and eosin stain and was presumed to represent the test article. The presence of the pigment corresponded to the green discoloration seen macroscopically. Trace to mild chronic interstitial inflammation of the lung, characterized by an infiltration of inflammatory cells, was observed in alveolar septa surrounding aggregates of pigmented macrophages in some mid-exposure and high-exposure level males and females. Chronic interstitial inflammation was accompanied by septal cell hyperplasia (Type II pneumocytes) in some mid- and high-exposure level males. The microscopic changes were
generally associated with the pigment and corresponded to the increased lung weight observed for the males in the high-exposure-level group. Lymphoid hyperplasia of the node was also present in all exposure groups. No test article-related lesions were seen in the nasal cavities of animals exposed to chromic oxide at any exposure level.

2) Recovery sacrifice: in the lung, trace to mild pigmented macrophages and black pigment in the peribronchial lymphoid tissue persisted in all treatment groups, males and females, at approximately equal incidence and severity, as seen in the terminal-sacrifice animals. Trace to mild septal cell hyperplasia and trace to mild chronic interstitial inflammation persisted in males of all treatment groups and females in the mid- and high-exposure-level groups. These lesions were the same or slightly increased in severity as compared to the terminal-sacrifice groups. Trace to mild black pigment also persisted in mediastinal lymph nodes in all exposure groups, with an apparent increase in incidence in some males in the two lowest-exposure groups as compared to the terminal-sacrifice group,
suggesting pulmonary clearance via the lymphatic system. Most of the pathologic changes observed at the recovery sacrifice were of minimal severity.

BRONCHOALVEOLAR LAVAGE EVALUATION:
- 4.4, 15 and 44 mg/m³: None of the exposure groups demonstrated a statistically significant difference from the control group for any BAL parameter. A yellow intracytoplasmic, crystalline material was present within the mononuclear cells from all exposure groups. The relative amount of material and percentage of affected cells increased progressively with increasing exposure concentration. Small amounts of crystals were present in >90% of the cells observed from the low-exposure-group animals and moderate to large amounts of crystalline material were noted in >99% of the cells observed in all high-exposure-group animals. The amount of crystals in the mid-exposure group was intermediate to the other 2 groups.

Effect levels

Dose descriptor:

NOEC

Effect level:

15 mg/m³ air (analytical)

Sex:

male/female

Basis for effect level:

organ weights and organ / body weight ratios

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Table 1. Selected organ weight changes at terminal sacrifice of rats exposed to chromic oxide

	Control	4.4 mg/m^3	15 mg/m^3	44 mg/m^3
Males Lung/trachea
wt (g)	0.99 + 0.07	0.98 + 0.055	1.0 + 0.077	1.11 + 0.050**
wt/bw (% x 10)	4.42 + 0.187	4.52 + 0.273	4.49 + 0.396	4.98 + 0.228**
Females Lung/trachea
wt (g)	0.81 + 0.081	0.81 + 0.080	0.85 + 0.084	0.88 + 0.068
wt/bw (% x 10)	5.65 + 0.418	5.78 + 0.577	5.77 + 0.629	6.40 + 0.618
Thyroid/parathyroid
wt (mg)	12 + 1.9	13 + 1.3	15 + 1.5**	14 + 2.3
wt/bw (% x 10^3)	8.26 + 1.493	8.89 + 0.880	10.10 + 1.147*	10.04 + 1.346*
Note: Organ weight changes given as mean + SD; bw = body weight. Organ weights of exposed animals were not statistically different from control animals at recovery sacrifice. * p </= 0.05; ** p </= 0.01

Applicant's summary and conclusion

Conclusions:

Derelanko et al. (1999) investigated the repeated dose inhalation toxicitiy of chromium oxide in groups of 15 male and 15 female CDF (Fischer 344/Crl BR VAF/Plus rats, which received the substance via nose-only inhalation at concentrations of 4.4, 15 and 44 mg/m³ air (actual concentration). The animals received the substance 6 hours/day, 5 days/week for 13 consecutive days. An control group was run concurrently. Five animals/sex of the treatment groups were used as recovery group at the end of the treatment period for a duration of 13 weeks. In addition, separate groups of 5 animals/sex/dose were investigated for bronchoalveolar lavage parameters. No test item-related effects were observed for clinical signs, mortality, body weights,ophthalmological examination, haematology, clinical chemistry and urinalysis. In addition, no test item-related effects were found during the bronchoalveolar lavage evaluation.

A NOAEC of 15 mg Cr2O3/m³ is derived on the basis of a dose-dependent mild inflammatory response characterised by an increase of phagocytotic cells and a subsequent increase of lung weights being significant in the male animals of the high dose group. None of the BALF parameters (lactate dehydrogenase (LDH), total protein, beta-glucuronidase, and glutathione reductase) was affected after 90-day inhalation exposure, indicating a lack of tissue damage. No other adverse effects were observed and the inflammatory response was completely reversible within the recovery period.