Tricobalt dicitrate

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Comparable to guideline study with acceptable restrictions.

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1991

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

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

Deviations:

yes

Remarks:

- no urinalysis, no clinical chemistry; limited documentation of the results

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

10026-24-1

EC Number:

600-050-9

Cas Number:

10026-24-1

IUPAC Name:

10026-24-1

Constituent 2

Reference substance name:

cobalt(II)sulfate heptahydrate

IUPAC Name:

cobalt(II)sulfate heptahydrate

Details on test material:

- Name of test material (as cited in study report): cobalt(II)sulfate heptahydrate
- Molecular formula (if other than submission substance): CoSO4*7H2O
- Molecular weight (if other than submission substance): 281 g/mol
- Analytical purity: 99%
- Other: The pH of aqueous solutions of cobalt(II)sulfate heptahydrate was measured at three concentrations. Solutions of 0.01, 0.1, and 1 M were found to have pH values of 6.3, 6.2 and 5.2, respectively.

Test animals

Species:

mouse

Strain:

B6C3F1

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Taconic Farms, Inc. (Germantown, NY, USA)
- Age at study initiation: 7 weeks
- Housing: individual housing
- Diet (e.g. ad libitum): NIH 07 rat and mouse ration (Zeigler Bros., Inc., Gardners, PA); ad libitium except during exposure periods

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20.7 - 25.2
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Remarks on MMAD:

MMAD / GSD: The mass median aerodynamic diameter of the aerosol for all exposures ranged from 0.83 to 1.10 µm.

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Hazleton 2000, Lab Products, Inc.
- System of generating particulates/aerosols: Cobalt sulfate heptahydrate aerosol was generated from an aqueous solution by nebulisation using dried compressed air. The aerosol was diluted to the desired concentration with air from the chamber air-conditioning system.
- Method of particle size determination: Cascade impactor samples were taken to determine aerosol size distribution. The mass median aerodynamic diameter of the aerosol for all exposures ranged from 0.83 to 1.10 µm. Cobalt sulfate hydration in the aerosol distribution line was determined by ultraviolet/visible spectroscopy. Hydration ratios of 7.66 and 7.67 were determined for two samples taken during the studies.

TEST ATMOSPHERE
- Brief description of analytical method used: 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.

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.

Duration of treatment / exposure:

13 weeks

Frequency of treatment:

6 hours/day, 5 days/week

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0.3, 1, 3, 10, 30 mg/m3
Basis:
other: nominal conc.; calculated as the anhydrous salt of cobalt(II)sulfate heptahydrate

Doses / concentrations 2

Remarks:

Doses / Concentrations:
0.300±0.029; 0.990±0.087; 2.93±0.275; 9.95±0.579; 30.0±1.64 mg/m3
Basis:
analytical conc.

No. of animals per sex per dose:

10

Control animals:

yes

Details on study design:

Animals distributed to weight classes and then assigned to cages and groups by a table of random numbers.

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice per day

DETAILED CLINICAL OBSERVATIONS: Yes

BODY WEIGHT: Yes
- Time schedule for examinations: weighed initially and once per week thereafter

HAEMATOLOGY: Yes
- Blood was obtained from the supraorbital sinus.

OTHER:
- estrous cyclicity
- sperm parameters (testis weight, sperm motility, sperm morphology)

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Statistics:

The analysis of organ weight and male reproductive system data was carried out by using the non-parametric multiple comparison procedures of Dunn (1964) or Shirley (1977) to assess the significance of pairwise 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 pairwise comparisons.
The proportion of time spent in each stage of the estrous cycle was compared by using the Wilks criterion statistic (Wilks, 1932) of the multivariate analysis of variance procedure, which was performed after an arc sine transformation of the data.

Results and discussion

Results of examinations

Details on results:

CLINICAL SIGNS AND MORTALITY
Two of ten males exposed to 30 mg/m3 died before termination of the study. No observed clinical signs appeared to be related to the exposure, with exception of rapid breathing and skin discoloration in the two males that died during week 11.

BODY WEIGHT AND WEIGHT GAIN
Mean body weights of males and females exposed to 30 mg/m3 and females exposed to 10 mg/m3 were lower than those of controls throughout the study. The final mean body weight of mice at 30 mg/m3 was 14% lower than that of the controls for males and 22% lower for females.

HAEMATOLOGY
No consistent or dose-related hematologic effects were observed.

ORGAN WEIGHTS
The absolute lung weights and the lung weight to body weight ratios were significantly increased in the 10 and 30 mg/m3 exposure groups. The absolute testis weight and the testis weight to body weight ratios were significantly decreased for males exposed to 30 mg/m3.

GROSS PATHOLOGY/HISTOPATHOLOGY:
Compound-related microscopic examinations were generally limited to the respiratory tract of mice of each sex. Lesions were concentration related and similar in incidence and severity in males and females. In the nose, degeneration of olfactory epithelium, squamous metaplasia of the respiratory epithelium, and an acute inflammatory cell exudate in the nasal cavity were seen primarily at the two highest exposure concentrations.
At the highest exposure concentration, necrosis, inflammation, and squamous metaplasia of the laryngeal epithelium were present in most mice. Some foci of necrosis in the laryngeal epithelium extended through the basement membrane into the underlying lamina propria. Squamous metaplasia of the respiratory epithelium in the trachea also occured in the higest exposure group in male and female mice. In all exposure groups below 30 mg/m3, inflammation and squamous metaplasia were observed.
In the lung of mice exposed to 10 or 30 mg/m3, there was regeneration of bronchiolar epithelium and hyperplasia of the alveolar epithelium. Infiltration of histiocytes (macrophages) into the alveolar spaces was also present. Chronic inflammation occurred primarily at the highest exposure concentration and consisted of fibrosis around bronchioles and in alveolar septae along with an inflammatory cell infiltrate. At the lower concentration, only a minimal increase in macrophages was seen in the alveoli.
Lymphoid hyperplasia was present in the mediastinal lymph nodes of mice at the 30 mg/m3 exposure concentration.
At the highest exposure concentration, atrophy of the testes was observed, which consisted of a loss of ferminal epithelium in the seminiferous tubules; more severely affected testes also contained foci of mineralisation.

OTHER:
REPRODUCTIVE FUNCTION: ESTROUS CYCLE
The estrous cycle was significantly longer in female mice exposed to 30 mg/m3.

REPRODUCTIVE FUNCTION: SPERM MEASURES
The number of abnormal sperm in mice exposed to 30 mg/m3 was significantly increased, and sperm motility was significantly reduced in mice exposed to 3, 10, or 30 mg/m3.
At the highest concentration, atrophy of the testis was observed, which consisted of a loss of germinal epithelium in the seminiferous tubules; more severly affected testes also contained foci of mineralisation.

Effect levels

1

Dose descriptor:

LOAEC

Effect level:

0.3 mg/m³ air

Sex:

male/female

Basis for effect level:

other: calculated as the anhydrous salt of cobalt(II)sulfate heptahydrate; the LOAEC based on squamous metaplasia in the larynx

2

Dose descriptor:

LOAEC

Effect level:

0.5 mg/m³ air

Sex:

male/female

Basis for effect level:

other: CoC6H6O7; recalculated value

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Lesions seen in the respiratory tract included degeneration of the olfactory epithelium, squamous metaplasia of the respiratory epithelium, and inflammation in the nose. The most sensitive tissue was the larynx, with squamous metaplasia observed also at the lowest exposure concentration. Thus, no NOAEC was identified.