Registration Dossier

Administrative data

Endpoint:
sub-chronic toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
90 days
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Justification for type of information:
As with all inorganic salts, the significance for toxicity or environmental assessment is the presence of specific ions that will form when in solution or when in biological systems.In the case of Cr III salts, the counter ion will have an effect on solubility and this is itself dependant on the type of media being used and in particular the pH of that media. It is generally accepted that in the case of metal salts, testing with salts that are soluble in the respective test media will ensure maximum exposure of the metal ions. This will include chlorides and nitrates as being more soluble and will indeed have relevance when dissolved in acid media, such as if ingested.Read-across to other chromium III salts is therefore considered valid as long as the exposure in the test system is greater than wold be expected for the substance under review for registration.

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 MJ, Rinehart WE, Hilaski RJ, Thompson RB, Löser E
Year:
1999
Bibliographic source:
Toxicological Sciences, 52:278–288

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)
Deviations:
not specified
GLP compliance:
not specified
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Type:
Constituent
Type:
Constituent
Test material form:
solid: particulate/powder
Remarks:
migrated information: powder
Details on test material:
CHROMIC OXIDE- Name of test material (as cited in study report): Chromic oxide- Molecular formula (if other than submission substance): Cr2O3- Molecular weight (if other than submission substance): 151.2- Physical state: Dark green powder- Analytical purity: Test article purity was detemined to be greater than 99% Cr(III) as Cr2O3 and less than 0.0001% Cr(VI)BASIC CHROMIUM SULFATE- Name of test material (as cited in study report): Basic chromium sulfate- Molecular formula (if other than submission substance): Cr(OH)(SO4)- Molecular weight (if other than submission substance): 165.1- Physical state: Dark green powder- Analytical purity: Test article purity was detemined to be greater than 25% Cr(III) as Cr2O3 and less than 0.0003% Cr(VI)- Storage condition of test material: Test articles were stored in separate, unused 1 m3 chambers that were continuously purged with a low flow of dry crompressed air. - Other: Both substances were supplied by British Chrome Chemicals (Urlay Nook, Eaglescliffe, Cleveland, UK)

Test animals

Species:
rat
Strain:
other: CDF (Fischer 344)/Crl BR VAF/Plus
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS- Source: Charles River Laboratories- Age at study initiation: 5 weeks- Housing: 3 days of group housing then indivuidually housed in stainless steel, suspended wire mesh cages- Diet (e.g. ad libitum): free access to commercial laboratory feed (Purina Certified Rodent Chow No 5002) diuring non exposure periods- Water (e.g. ad libitum): free access during non exposure periods- Acclimation period: 2 weeksENVIRONMENTAL CONDITIONS- Temperature (°C): 21 +/- 2C- Humidity (%): 43 +/- 11%- Photoperiod (hrs dark / hrs light): 12 hr light/dark cycle

Administration / exposure

Route of administration:
inhalation: dust
Type of inhalation exposure:
nose only
Vehicle:
air
Remarks on MMAD:
MMAD / GSD: Mean particle size distribution data (MMAD) in microns (GSD)) over 13 weeks (21 sampels per test group) were 1.8 (1.9), 1.9 (1.84), and 1.9 (1.78) for chromic oxide and 4.2 (2.48), 4.2 (2.37), and 4.5 (2.5) for basic chromium sulfate for the low, mid and high exposure groups respectively.
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION- Exposure apparatus: Stainless steel and acrylic nose only inhalation chambers- System of generating particulates/aerosols: Chromic oxide: modified low output dust generator, using spinning glass beads over a packed cake of test material Basic chrome sulfate: auger dust feeder and an air microniser- Air change rate: At least 12 chamber air changes per hour- TEST ATMOSPHERE- Brief description of analytical method used: Particle size measurements were made using a cascade impactor from each exposure level once per day for the first two weeks, then weekly thereafter.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Mean aerosol concentrations and standard deviations over 13 weeks were4.4 ± 0.23, 15 ± 1.2, and 44 ± 3.7 mg/m3 for chromic oxide and 17 ± 4.3, 54 ± 4.2, and 168 ± 25.3 mg/m3 for basic chromium sulfate. No hexavalent chromium was detected (detection limit = 10 ng/ml).
Duration of treatment / exposure:
Animals were exposed for 65 exposures over 13 consecutive weeks.
Frequency of treatment:
Animals were exposed for 6 hrs/day, 5 days/week
Doses / concentrationsopen allclose all
Dose / conc.:
4.4 mg/L air (nominal)
Remarks:
Chromic oxide
Dose / conc.:
15 mg/L air (nominal)
Remarks:
Chromic oxide
Dose / conc.:
44 mg/L air (nominal)
Remarks:
Chromic oxide
Remarks:
Doses / Concentrations:0, 17, 54, 168 mg/m3Basis:other: basic chromium sulfate
No. of animals per sex per dose:
10 males and 10 females, main group5 males and 5 females, additional 13 week recovery period5 males and 5 females, 5 day exposule, BAL
Control animals:
yes, sham-exposed
Details on study design:
- Dose selection rationale: Doses were set to be multiples of the threshold limit value (TLV) for trivalent chromium and were equivalent to 3, 10 and 30 mg/m3 chromium

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes- Time schedule: Before and after each exposure for clinical signs of toxicity. Twice daily for morbidity and mortality during the recovery period and at weekends. BODY WEIGHT: Yes- Time schedule for examinations: WeeklyOPHTHALMOSCOPIC EXAMINATION: Yes- Time schedule for examinations: All animals examined during the acclimation period and prior to terminal necropsy. HAEMATOLOGY: Yes / No / No data- Time schedule for collection of blood:- Anaesthetic used for blood collection: Yes (identity) / No / No data- Animals fasted: Yes / No / No data- How many animals:- Parameters checked in table [No.?] were examined.CLINICAL CHEMISTRY: Yes / No / No data- Time schedule for collection of blood:- Animals fasted: Yes / No / No data- How many animals:- Parameters checked in table [No.?] were examined.URINALYSIS: Yes / No / No data- Time schedule for collection of urine:- Metabolism cages used for collection of urine: Yes / No / No data- Animals fasted: Yes / No / No data- Parameters checked in table [No.?] were examined.NEUROBEHAVIOURAL EXAMINATION: Yes / No / No data- Time schedule for examinations:- Dose groups that were examined:- Battery of functions tested: sensory activity / grip strength / motor activity / other:OTHER:
Sacrifice and pathology:
Animals found dead or euthanised by design at study terminatiion were necropsied. At necroscopy, heart, lungs, liver, spleen , kidneys, adrenal glands, thyroid/parathyroid glands, testes, and ovaries were weighed. Tissues typically harvested for sub-chronic studies were also removed and preserved. All tissues were placed in 10% neutral buffered formalin, except eye tissue which was fixed in Davidson's fixative. Microscopic evaluation was conducted on hematoxylin and eosin stained tissues from the control and high exposure groups for both test substances. The kidneys, livers, nasal tissues, trachea, lungs, larynx, mediastinal and mandibular lymph nodes and gross lesions from all animanls in the low and mid exposure group levels were also examined for both substances. A formal peer review of the histopathologic findings was performed.
Other examinations:
CLINICAL PATHOLOGYStandard hematology, clinical biochemistry, and urinalysis determinations were conducted on 10 animals per sex per group, designated for necropsy at the end of exposure. Animals were fasted overnight, prior to sampling, with water available. Blood samples were obtained from the orbital sinus plexus. At necropsy, bone marrow smears were prepared and differential cell counts were evaluated. All clinical procedures were performed using automated instrumentation except bone marrow smears, which were examined microscopically. Urinalysis determinations were conducted on samples collected overnight in stainless steel metabolism cages. Urinalysis determinations were performed by gross observation, microscopy and automated clinical analyser. Following urinalysis testing, aliquots of the remaining urine from 5 animals in the control group and the high exposure level groups for both test substances were submitted for beta2-microglobulin analysis. BRONCHOALVEOLAR LAVAGE EVALUATIONBAL analysis was conducted on 5 animals per sex per group exposed for 5 consecutive days with the main study animals. Rats were anaesthetised by i.p. injection of sodium pentobarbital. Lungs, heart, trachea, larynx and tongue were removed en block. Following tracheal cannulation, the airways were washed 3 successive times with warmed physiological saline (30 µl/g bw) and the resulting BALF pooled. Nucleated cell counts were preformed using a Neubauer hemocytometer, and cell differential counts were perfomred on Wright-Giemsa stained smears. Chemical analysis performed spectrophotometrically included for lactate dehydrogenase, total protein, beta-glucoronidase and glutathione reductase. SPERM EVALUATIONAt necropsy sperm samples from the left caudal epidydimis of 10 males per group were used for automated evaluations of sperm motility, count and morphology. Concentration and morphology were evaluated using visual methods. 200 intact sperm were evaluated for morphology. Intact sperm were evaluated as normal or abnormal. The number of disarticulated sperm in each field was also assessed.
Statistics:
Statistical anlysis were performed of body weights, clinical pathology tests, BALF data and organ weights using one-way analysis of variance. If the result was non-significant, no additional analysis was performed. 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 comparison. If Bartlett's test was significant, the Welch t-test with Bonferonni correction was used for pairwise comparisons. Kruskal-Wallis analysis of variance, followed where appropriate by the Mann-Whitney U test was used for those parameters whose parametric analysis was inappropriate. The level for statistical significance was set at p ≤ 0.5.

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
effects observed, treatment-related
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:
no effects observed
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Details on results:
CLINICAL SIGNS AND MORTALITYNo compound related mortalities occurred for either test substance during the study. 6 animals died on Day 1 as a direct result of the restraint tubes. and were replaced. One male from the high exposure group for basic chromium sulfate died on Day 4, but death was not considered to be related to exposure. Clinical signs of toxicity were limited to sporadic laboured breathing noted during 2 of the weekly observations in females exposed to the high concnetration of basic chromium sulfate. No exposure related effects were noted for either test substance in the opthalmologic evaluations or for sperm motility, morphology or concentration. BODY WEIGHT AND WEIGHT GAINNo statistically significant differences in body weight gains in males or females were found for the chromic oxide exposed group. In the basic chromium sulfate exposed group, statistically significant exposure related reduced mean body weights were observed in males in the mid and high exposure groups, and in females in the high exposure group during the 13 week exposure period. At the end of the 13 week recovery period, sacrificed males from the same exposure groups continued to show reduced meman body weights. Female body weights were comparable to the control group in all groups after the recovery sacrifice. FOOD CONSUMPTIONQuantitative data were not collected, but no observable decreases in food consumption were noted. OPHTHALMOSCOPIC EXAMINATIONNo effects were noted in eaminations during the acclimatisation period or on examination before necropsy. HAEMATOLOGY/CLINICAL CHEMISTRY/URINALYSISChromic oxide: None of the exposure groups for either sex exhibited a statistically significant difference for any hematological, serum biochemical or urinalysis parameters. Beta-microglobulins were not detected in urine samples from any group.Basic chromium sulfate: Most hematological, serum biochemical and urinalysis parameters from all exposure groups were similar to the controlmgroup a tthe terminal sacrifice. Increased leukocytes associated with increased neutrophils, some statistically significant were noted in the mid and high exposure groups for males and females. Alkaline phosphatase was statistically elevated in high exposure group females and serum cholesterol was statistically decreased in mid and high exposure group females. ORGAN WEIGHTSChromic oxide:Slight yet statistically significant increases in mean absolute and relative lung/trachea weights occurred in high exposure level males. Macroscopic and histologic changes were present to explain these changes. Other statistically significant increasees were noted in mean absolute and relative thyroid/parathyroidweights in the mid exposure group females, and in the mean thyroid/parathyroid/bodyweight ratios in the high exposure group females. These organ weight changes were very small and theur biological importance could not be determined. At the recovery sacrifice, all organ weights were comparable to the control group. Basic chromium sulfate: At terminal sacrifice statistically significant increases in mean absolute and relative lung/trachea weights occurred in all exposure groups in males and females. These changes corresponded to changes seen microscopically. Other organ weight changes, without corresponding microscopic changes were noted which typicallty correspond to reduced body weights. At the recovery sacrifice statistically significant increases in male and female mean absolute and relative lung weights continued for the mid and high exposure groups. Microscopic changes were present to explain the increased lung weights. GROSS PATHOLOGYExposure-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. Gray lung discoloration was commonly observed in animals exposed to basic chromium sulfate at the mid- and high-exposure levels. The degree of discoloration with both materials 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 or basic chromium sulfate (recovery sacrifice only). Mediastinal lymph-node enlargement was observed at the recovery sacrifice in animals exposed to basic chromium sulfate (all exposure levels). Tan focus/foci were observed in the lungs at the recovery sacrifice of a high percentage of males exposed to the high level of basic chromium sulfate. The tan focus/foci correlated well with the presence of alveolar macrophages, and mediastinal lymph node enlargement correlated well with histiocytosis described below. Additional macroscopic observations were few in number and considered incidental. HISTOPATHOLOGY: NON-NEOPLASTICChromic oxide: In microscopic examination, an accumulation of randomly distributed foci or aggregates of alveolar macrophages filled with dense black pigment was observed within the alveolar spaces. Black pigment was also present at tracheal bifurcation, in the peribronchial lymphoid tissue, and within the mediastinal lymph nodes. The black pigment correlated with the macroscopic green discoloration of lungs and was presumed to represent the test article. Trace to mild chronic inflammation and septal hyper-plasia were observed in alveolar septa surrounding the aggregates of pigmented macrophages in mid- and high-exposure animals, and lymphoid hyperplasia was present in all exposure groups. Pigment deposits and slight inflammatory changes or septal hyperplasia were also observed after the recovery period at a similar or increased incidence and severity. Also, some low-dose males exhibited slight inflammatory changes in alveolar septa. No other treatment-related changes in macro-scopic or microscopic pathology, sperm evaluation, clinical biochemisty, urinalysis, or haematology were observed.Basic Chromiun sulfate: At terminal sacrifice, chronic inflammation was observed involving the alveoli of all exposure-level groups, consisting of alveolar spaces filled with macrophages, neutrophils, lymphocytes, and cellular debris. Some foci exhibited quite intense inflammation and thickening of alveolar walls. Chronic interstitial inflammation was usually multifocally distributed and consisted of thickened alveolar septa caused by inflammatory cell infiltration and hyperplasia of alveolar septal cells (type II pneumocytes). Multifocal areas of granulomatous inflammation, characterized by infiltration of macrophages and multinucleated giant cells, was observed at all exposure levels and was closely associated with foreign material seen in the lung and presumed to be the test article. Trace to severe, multifocal to diffuse pulmonary infiltration of alveolar macrophages with foamy or granular appearing acidophilic cytoplasm was observed in the alveolar lumens and correlated with the gray discoloration of the lungs that was observed at necropsy. These changes corresponded to the increased lung weights observed in all the exposure groups. Green refractile foreign material was present in the lamina propria and submucosa of the larynx of animals in all treatment groups and was associated with an infiltration of macrophages and multinucleated giant cells (granulomatous inflammation). Histiocytosis consisting of macrophages or histiocytes with abundant foamy cytoplasm and lymphoid hyperplasia observed in the peribronchial lymphoid tissue and mediastinal lymph node correlated with lymph node enlargement observed at necropsy. Changes in nasal tissues considered to be test article-related, were observed in males and females, and included acute inflammation, suppurative exudate, and mucoid exudate. One or more of these changes were seen in all 4 examined levels of the nasal cavity but were slightly more prevalent in the mid-posterior portion. All other microscopic findings were incidental and/or spontaneous and considered unrelated to the test article. At recovery sacrifice foreign material persisted in the lungs of some animals in all exposure groups, but with decreased incidence in most groups. Trace to moderate chronic inflammation of the alveoli, trace to moderate chronic interstitial inflammation, septal cell hyperplasia, and alveolar macrophages were approximately equal in incidence and severity at the mid- and high-exposure levels as compared to the terminal sacrifice animals, with severity slightly reduced at the low exposure level. Peribronchial histiocytosis continued to be observed only in males and females of the mid- and high-exposure groups. The incidence and severity in the mid-exposure group was approximately equal to the terminal sacrifice animals while the incidence in the high-exposure group increased in both males and females, suggesting clearing of the basic chromium sulfate via the reticuloendothelial system. Granulomatous inflammation of the lung decreased in incidence except in the males and females of the high-exposure group where the incidence was approximately equal to that of the terminal sacrifice animals of this group. In the larynx, foreign material and granulomatous inflammation was either not detected at the low-exposure (both sexes) or mid-exposure (males) or markedly decreased in incidence and severity in mid-exposure females and high-exposure groups (both sexes) as compared to the terminal-sacrifice animals. The incidence and severity of histiocytosis and lymphoid hyperplasia of the mediastinal lymph node generally remained at similar levels in both males and females of all treated groups in the terminal and recovery sacrifices. Nasal cavity findings were not detected except for trace suppurative exudate seen in the most anterior section in one or two animals from each treatment group. All other microscopic findings were incidental andor spontaneous and considered unrelated to the test article.BRONCHOALVEOLAR LAVAGEChromic oxide:None of the exposure groups demonstrated a statistically significant difference from the control gorup for any BAL parameter. Basic chromium sulfate: Evaluation of the BAL fluid from exposued animals demostrated several compound related effects. Males and females at all levels showed statistically reduced total nucleated cell counts. Segemented neutrophils increased while mononucleated clear cells decreased, although not to a statistically significant degree, at all concentration levels. Non-statistical increases in protein and lactic dehydrogenase were also observed. Increased amounts of cell debris and lysed cells were noted at all exposure levels.

Effect levels

open allclose all
Dose descriptor:
NOAEL
Basis for effect level:
other: chromic oxide
Remarks on result:
not determinable
Remarks:
no NOAEL identified
Dose descriptor:
LOAEL
Effect level:
4.4 mg/m³ air
Basis for effect level:
other: chromic oxide
Dose descriptor:
NOAEL
Basis for effect level:
other: basic chromium sulfate
Remarks on result:
not determinable
Remarks:
no NOAEL identified
Dose descriptor:
LOAEL
Effect level:
17 mg/m³ air
Basis for effect level:
other: basic chromium sulfate

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/m3

15 mg/m3

44 mg/m3

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 103)

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

   

Table 2: Selected Organ Weight Changes at Terminal and Recovery Sacrifices of Rats Exposed to Basic Chromium Sulphate

Control

17 mg/m³

54 mg/m³

168 mg/m³

Males

Lung/trachea

wt [g]

0.99 ±0.70

(1.32 ± 0.113)

1.26 ± 0.071**

(1.52 ± 0.132)

1.51 ± 0.088**

(1.95 ± 0.068**)

1.86 ± 0.89**

(2.67 ± 0.144**)

wt/bw [%×10]

4.42 ± 0.187

(3.89 ± 0.214)

5.60 ± 0.271**

(4.66 ± 0.373**)

7.15 ± 0.252**

(6.37 ± 0.298**)

10.69 ± 0.688**

(8.77 ± 0.274**)

Brain

 wt [g]

1.79 ± 0.087

1.82 ± 0.055

1.76 ± 0.061

1.71 ± 0.069*

 wt/bw [%×10]

8.02 ± 0.380

8.12 ± 0.374

8.38 ± 0.473

9.83 ± 0.518**

Kidney

wt [g]

1.54 ± 0.106

1.35 ± 0.049**

1.62 ± 0.085

1.64 ± 0.082

 wt/bw [%×10]

7.62 ± 0.300

7.28 ± 0.207

7.30 ± 0.283

7.78 ± 0.350**

Liver

wt [g]

5.48 ± 0.367

5.63 ± 0.271

5.17 ± 0.459

4.39 ± 0.146**

 wt/bw [%×10]

2.45 ± 0.070

2.50 ± 0.050

2.45 ± 0.091

2.53 ± 0.120

Thyroid/parathyroid

wt [mg]

14 ± 2.5

15 ± 2.9

14 ± 1.8

15 ± 3.5

 wt/bw [%×103]

6.21 ± 1.052

6.64 ± 1.475

6.74 ± 1.021

8.76 ± 2.074*

Spleen

wt [g]

0.45 ± 0.038

0.48 ± 0.036

0.40 ± 0.040*

0.32 ± 0.035**

 wt/bw [%×10]

1.99 ± 0.149

1.91 ± 0.132

1.89 ± 0.125

1.84 ± 0.151

Testes

wt [g]

2.36 ± 0.356

2.39 ± 0.261

2.22 ± 0.286

2.18 ± 0.215

wt/bw[%×10]

10.54 ± 1.315

10.65 ± 1.098

10.52 ± 1.049

12.53 ± 1.238**

Females

Lung/trachea

wt [g]

0.81 ±0.081

(0.93 ± 0.079)

0.98 ± 0.094**

(1.08 ± 0.120)

1.29 ± 0.164**

(1.59 ± 0.120**)

1.66 ± 0.084**

(2.45 ± 0.120**)

wt/bw [%×10]

5.65 ± 0.418

(4.74 ± 0.384)

6.99 ± 0.619**

(5.75 ± 0.315**)

9.24 ± 1.036**

(8.02 ± 0.750**)

12.89 ± 1.134**

(13.34 ± 0.614**)

Thyroid/parathyroid

wt [mg]

12 ± 1.9

11 ± 1.3

12 ± 1.8

14 ± 2.1*

wt/bw [%×103]

8.26 ± 1.493

7.96 ± 1.154

8.63 ± 1.265

10.77 ± 1.522**

Spleen

wt [g]

0.33 ± 0.037

0.31 ± 0.033

0.30 ± 0.033

0.28 ± 0.033**

wt/bw [%×10]

2.32 ± 0.268

2.19 ± 0.212

2.17 ± 0.162

2.19 ± 0.273

Note. Organ weight changes, values given as mean ± SD; bw = body weight. Non-bracketed values = terminal sacrifice, bracketed values = recovery sacrifice.* p0.05;**p0.01.

Applicant's summary and conclusion

Conclusions:
A NOAEC was not established. The LOAEC for chromic oxide was 4.4 mg/m3 and for basic chromium sulphate was 17 mg/m³. These valuses are equivalent to a chromium level of 3 mg/m3.Effects appear to be localised to the respiraotry tract. Systemic effects were not noted for either test substance, apart from bodyweight changes for basic chromium sulfate, which are considered secondary to the stress of exposure.
Executive summary:

The toxicity of trivalent chromium compounds; chromic oxide and basic chromium sulfate, was investigated in rats in a 13-week nose-only inhalation study that included a 13-week recovery period. Nose-only exposures to insoluble chromic oxide dust at 4.4, 15, or 44 mg/m3 or soluble basic chromium sulfate dust at 17, 54, or 168 mg/m3 (trivalent chromium equivalent concentrations of 3, 10, and 30 mg/m3) were carried out for 6 h/day, 5 days/week. No compound-related mortality occurred. General toxic effects, only observed with high-exposure levels of basic chromium sulfate, included sporadic signs of labored breathing and depressed body weights. No apparent compound-related effects were noted for sperm motility or morphology, for any concentration of either test material. Bronchoalveolar lavage fluid evaluations showed test material in mononuclear cells with chromic oxide and increased neutrophils, protein, lactic dehydrogenase and cellular debris with basic chromium sulfate. The principle effects for both materials were primarily to the respiratory tract. Chromic oxide caused pathological changes in the bronchial and mediastinal lymphatic tissue and lungs, consisting of the presence of pigment-laden macrophages, lymphoid and septal hyperplasia, and interstitial inflammation similar to that observed with other inert dusts. Basic chromium sulfate produced more severe and widespread effects in the nasal cavity, larynx, lungs, and mediastinal lymph node. Effects were characterized by accumulation of foreign material, infiltration of alveolar macrophages, septal cell hyperplasia, and granulomatous and chronic inflammation. Pigment was still present in chromic oxide and, to a lesser extent, in basic chromium sulfate-treated animals after the 13-week recovery period, with partial recovery of the pathological lesions. A NOAEL was not established for either test material, but 4.4 mg/m3 was thought to be near the NOAEL level for subchronic exposure to chromic oxide. The results of this study indicate significant differences in toxicity to the respiratory tract between trivalent chromium compounds chromic oxide and basic chromium sulfate. These are likely related to differences in acidity and water solubility, rather than chromium concentration per se.