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Toxicological information

Repeated dose toxicity: inhalation

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Administrative data

Endpoint:
short-term repeated dose toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
GLP study reliable with restrictions. With respect to the purpose for which this study was conducted as a 16d inhalation toxicity study, it may be considered reliable with restriction. However, the study design and the reporting suffer from several major shortcomings which ultimately do not allow the identification of potential target organ for systemic effects as detailed below.
Cross-reference
Reason / purpose:
reference to same study

Data source

Referenceopen allclose all

Reference Type:
publication
Title:
Inhalation toxicity studies of cobalt sulfate in F344/N rats and B6C3F1 mice
Author:
Bucher, J.R., et al.
Year:
1990
Bibliographic source:
Fund. Appl. Tox. 15, 357-372
Reference Type:
study report
Title:
Unnamed
Year:
1991
Reference Type:
publication
Title:
Inhalation toxicity and carcinogenicity studies of cobalt sulfate
Author:
Bucher, J.R.; et al.
Year:
1999
Bibliographic source:
Toxicol. Sci. 49, 56-67

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Groups of five mice of each sex were exposed to air containing cobalt sulfate heptahydrate at concentrations of 0 (chamber controls), 0.1, 0.5, 5, 50 or 200 mg/m³ (calculated on the basis of the anhydrous salt) 6 hours per day, for 12 exposures over 16 days.
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Cobalt sulfate heptahydrate (CoSO4 * 7H2O) (From Curtin Matheson Scientific Inc. (Kansas City, MO)- Physical state: red, crystalline solid- Molecular weight: 281.13 g- Analytical purity: approx. 99 %; Elemental analyses for sulfur and hydrogen were in agreement with the theoretical values for cobalt sulfate heptahydrate. Karl Fischer water analysis indicated 44.6 % +/- 0.5% water- Impurities (identity and concentrations): Spark source mass spectroscopy indicated 140 ppm nickel present as impurity; all other impurities had a combined total of less than 175 ppm.- Lot No.: 412092- Storage condition of test material: To ensure stability, the bulk chemical was stored in its original shipping containers, metal cans, at room temperature.- Other: Cobalt sulfate heptahydrate is stable as a bulk chemical when stored protected from light at normal temperatures. The heptahydrate dehydrates to the hexahydrate at 41.5 °C and to the monohydrate when heated to 71°C, with no further changes expected below the decomposition temperature (708°C). Therefore, an accelerated stability study was not conducted. Stability was monitored during the study using elemental analysis by inductively coupled plasma/atomic emission spectroscopy (ICP/AES) normalized against a cobalt standard (National Institute of Standards and Technology, Gaithersburg, MD); no degradation of the bulk chemical was detected.

Test animals

Species:
mouse
Strain:
B6C3F1
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS- Source: Taconic Farms (Germantown, NY)- Age at study initiation: 8 weeks- Weight at study initiation:- Fasting period before study:- Housing: Mice were housed individually. - Diet (ad libitum): NIH-07 (Zeigler Brothers, Inc., Gardners, PA)- Water (e.g. ad libitum):- Quarantine period: 25 days before beginning of the studyENVIRONMENTAL CONDITIONS- Temperature (°F): 69.2 77.3°F- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:
inhalation: aerosol
Type of inhalation exposure:
whole body
Vehicle:
clean air
Remarks on MMAD:
MMAD / GSD: 0.83-1.10 µm, GSD not reported
Details on inhalation exposure:
Cobalt sulfate heptahydrate aerosol was generated from an aqueous solution by nebulisation using dried compressed air. The aerosol was heated to about 26° C to dry the particles partially and then was passed into a Nalgene® settling tank to eliminate large particles and water droplets. Further drying was accomplished by heating the aerosol to 45° C as it left the tank. The cobalt sulfate heptahydrate/air stream entered the distribution tube and was injected into each chamber (Hazleton 2000, Lab Products, Inc.) with air multiplier pumps. The aerosol was diluted to the desired concentration with air from the chamber air-conditioning system.Atmospheric concentrations are expressed in milligrams of cobalt sulfate per cubic meter of air rather than in milligrams of the heptahydrate
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Three real-time aerosol monitors (Model RAM-1, GCA Environmental Instruments) were used to determine the concentration of the aerosol in the exposure chambers once every 20 minutes throughout the exposure period. The monitors were calibrated through the use of filter grab samples. Samples collected on filter paper were analysed for cobalt by inductively coupled plasma analysis after extraction with dilute nitric acid.Although the mean chamber concentrations achieved during the 16-day studies were quite close to target concentrations, the variations about the means were much larger than desired.
Duration of treatment / exposure:
16 days
Frequency of treatment:
6 hours (plus T90: approx. 8 min) per day for 12 exposures
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:0.093 mg/m³Basis:analytical conc.
Remarks:
Doses / Concentrations:0.50 mg/m³Basis:analytical conc.
Remarks:
Doses / Concentrations:4.73 mg/m³Basis:analytical conc.
Remarks:
Doses / Concentrations:50.1 mg/m³Basis:analytical conc.
Remarks:
Doses / Concentrations:199 mg/m³Basis:analytical conc.
No. of animals per sex per dose:
5 males / 5 females
Control animals:
yes, concurrent vehicle
Positive control:
No

Examinations

Observations and examinations performed and frequency:
Observed 2 or 3 x d; weighed initially, on d 8, and at necropsy
Sacrifice and pathology:
GROSS PATHOLOGY: Yes (see any other information on material and methods)HISTOPATHOLOGY: Yes (see any other information on material and methods)
Other examinations:
Organ weights obtained at necropsy.
Statistics:
The analysis of organ weight data was carried out by using the nonparametric multiple comparison procedures of Dunn (1964)* or Shirley (1977)* to assess the significance of pair wise comparisons between dosed and chamber control groups. Jonckheere's test (Jonckheere, 1954)* was used to evaluate the significance of dose-response trends and to determine whether Dunn's or Shirley's test was more appropriate for pair wise comparisons. * References- Dunn, O.J. (1964) Multiple comparisons using rank sums. Technometrics 6:241-252.- Shirley, E. (1977) A non-parametric equivalent of Williams' test for contrasting increasing dose levels of a treatment. Biometrics 33:386-389.- Jonckheere, A. (1954) A distribution-free sample test against ordered alternatives. Biometrika 41:133-145.

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
Mortality: 200 mg/m³ all rats & 50 mg/m³ 4/5 males & 1/5 females before study end; Clinical signs: 50 or 200 mg/m³ exposure included hyperactivity, chromodacryorrhea, hypothermia, rapid & shallow breathing & reduced body tone
Mortality:
mortality observed, treatment-related
Description (incidence):
Mortality: 200 mg/m³ all rats & 50 mg/m³ 4/5 males & 1/5 females before study end; Clinical signs: 50 or 200 mg/m³ exposure included hyperactivity, chromodacryorrhea, hypothermia, rapid & shallow breathing & reduced body tone
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
mice exposed to 50 mg/m³ lost weight; final mean body weights at other exposure concentrations were similar to those of controls
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
Behaviour (functional findings):
not specified
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
50 mg/m³: absolute lung weight and lung weight to body weight ratios were significantly increased for both sexes. Absolute thymus weights and thymus to body weight ratios were markedly decreased (less than 1/2 those of controls) for both sexes.
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
Exposure-related lesions observed at necropsy in mice from the 3 highest exposure groups consisted of grey discolouration of the lungs and fluid in the larynx and trachea.
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
see "details on results"
Histopathological findings: neoplastic:
not specified
Details on results:
Lesions attributed to cobalt sulfate exposure were seen at all levels of the respiratory tract in mice. At the three highest concentrations, inflammationand necrosis of the respiratory epithelium were seen in the larynx, trachea, bronchioles, and respiratory turbinates of the nose. Degeneration of the olfactory epithelium was also present. In the 50 mg/m³ group, mice that survived more than 1 week or were killed at the end of the 16-day exposure period had hyperplasia (acanthosis) of the squamous epithelium in the larynx and regeneration of the bronchiolar epithelium in the lung. Also at the 50 mg/m³ exposure concentration, an inflammatory response in the lung was characterized by fibrosis around bronchioles and infiltration of histiocytes into alveolar spaces. Other lesions observed in exposed mice that died during the exposure period consisted of lymphoid depletion and necrosis in the thymus and congestion of vessels in the brain/meninges. In the liver, necrosis of hepatocytes was present in all mice that died during the exposure period; minimal necrosis was present in the liver of one male mouse (50 mg/m³) that was killed at the end of the study.

Effect levels

open allclose all
Dose descriptor:
NOAEC
Based on:
test mat.
Sex:
male/female
Remarks on result:
not determinable
Remarks:
no NOAEC identified
Dose descriptor:
other: no LOAEC identified
Remarks on result:
not measured/tested
Remarks:
Effect level not specified (migrated information)

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
In 16-day studies, exposure to 200 mg/m³ cobalt sulfate heptahydrate as an aerosol resulted in deaths of all mice of each sex within the first 3 days on study. Several male and female mice exposed to 50 mg/m³ also died somewhat later. These relatively short periods of exposure to 50 or 200 mg/m³ cobalt sulfate heptahydrate resulted in necrotizing inflammation in the upper respiratory tract (nares, larynx, and trachea) as well as in the bronchiolar epithelium of the lung. Only oedema and haemorrhage were seen in the alveolar portion of the lung in animals dying early in the exposure period. Animals that survived beyond 1 week developed an inflammatory response in the lungs characterized by infiltration of macrophages and fibrosis around bronchioles. Necrotizing inflammatory lesions in the airways were less common in animals that survived; in these animals, metaplasia of the respiratory epithelium to a squamous epithelial cell with acanthosis or hyperplasia, fibrosis, and histiocyte infiltration was commonly seen.Lesions observed in other organs in mice in the 16-day studies, including congestion and lymphoid necrosis in the thymus, congestion and necrosis in the liver, and congestion of vessels in the brain, are typical changes associated with an agonal or stressed condition in moribund or early-death animals. No adverse effects in the heart of mice were noted.With respect to systemic toxicity, the study shows major shortcomings in design, conduct, dose/exposure selection and reporting, which do not allow the identification of potential target organs for systemic effects. Major deficiencies include that neither both species nor all exposure groups were chosen for histopathological examination, and where presented the severity of such lesions is not indicated. Because of this, for example the investigation of effects on the reproductive system, serum and thyroid function nor any other potential target organs for systemic toxicity or any other dose-response relationship can be determined. In addition, since the respiratory tract is particularly sensitive to soluble cobalt substances, this fact limits the maximum exposure/dose to a level at which systemic toxicity does not yet manifest itself.In conclusion, this study is not suitable to derive a NOAEC/LOAEC for systemic effects.