Manganese dioxide

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

disregarded due to major methodological deficiencies

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: The study was not performed under GLP conditions, and the report contains unexplained inconsistencies. It is therefore not possible to ascertain the relibaility of the findings.

Data source

Reference

Reference Type:

publication

Title:

Short-term oral administration of several manganese compounds in mice: physiological and behavioural alterations caused by different forms of manganese

Author:

Komura J and Sakamoto M

Year:

1991

Bibliographic source:

Bulletin of Environmental, Contamination and Toxicology, 46:921-928

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Mice were exposed to MnO2 in their diet for 100 days and compared to controls fed on a diet containing 130 mg Mn/kg. Thirty days into the exposure period, mice were tested for spontaneous motor activity. Mice were decapitated 24 hours after their last feed. Blood samples were collected and analysed. Furthermore, tissues were removed, weighed and analysed for Mn content.

GLP compliance:

not specified

Limit test:

no

Test material

Reference

Name:

Unnamed

Type:

Constituent

Details on test material:

- Molecular formula: MnO2

Test animals

Species:

mouse

Strain:

other: ddY

Sex:

male

Details on test animals and environmental conditions:

TEST ANIMALS
- Age at study initiation: 6 weeks
- Weight at study initiation: 28.2 ± 0.7 g
- Diet: ad libitum
- Water: ad libitum

Administration / exposure

Route of administration:

oral: feed

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

100 days

Frequency of treatment:

daily

Doses / concentrations

Remarks:

Doses / Concentrations:
2 g Mn / kg
Basis:
nominal in diet

No. of animals per sex per dose:

8 males per dose group.

Control animals:

other: Standard laboratory mouse chow containing 130 mg Mn/kg

Positive control:

None

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: No data

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations:

FOOD CONSUMPTION AND COMPOUND INTAKE: Yes
- Time schedule: Daily
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes / No / No data
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: Yes / No / No data

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at termination
- How many animals: all animals
- Parameters checked included: red blood cell count, white blood cell count, haemoglobin and haematocrit

CLINICAL CHEMISTRY: No data

URINALYSIS: No data

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: the mice were tested for spontaneous motor activity after an interval of 30 days. Activity was measured using an ANIMEX Activity Meter. Two mice were placed in a plastic cage at night, and after 10 minutes of acclimatisation, their activity was measured for 30 minutes.

Sacrifice and pathology:

Mice were decapitated at 24 hours after their last feed.

Tissue samples were removed, weighed, and stored at -20°C until analysis. Hair was rinsed with ethyl alcohol and washed withsodium lauryl sulphate, and then dried. Tissues were digested by the wet ashing method and the resulting solutions were analysed for Mn content by atomic absorption spectroscopy with a flame atomizer.
Tissues sampled included: liver, kidney, pancreas, prostate gland, spleen, brain, hair, bone and muscle.

Statistics:

Data were statistically analysed using Student's t-test and analysis of variance.

Results and discussion

Results of examinations

Clinical signs:

not examined

Mortality:

not examined

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

See "Details on results" for information

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

effects observed, treatment-related

Description (incidence and severity):

See "Details on results" for information

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

(Mn content of various tissues)

Histopathological findings: non-neoplastic:

not examined

Histopathological findings: neoplastic:

not examined

Details on results:

BODY WEIGHT AND WEIGHT GAIN: MnO2 did not cause any effect on weight change compared to the controls.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Food consumption was similar to controls. The mean daily food consumption was 3.6 ± 0.9 g in the control group and 3.8 ± 0.7 g in the MnO2 group.

HAEMATOLOGY: White blood cell count was significantly lower than the control

NEUROBEHAVIOUR: No locomotor differences were seen compared to the control

GROSS PATHOLOGY: manganese content in tissues was significantly greater than controls in the liver, kidney, spleen, hair, bone and muscle

Effect levels

Dose descriptor:

NOAEL

Sex:

male

Remarks on result:

not determinable

Remarks:

no NOAEL identified

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Manganese concentration in various tissues are shown below. Values represent the mean +/- SD for 8 mice

Organ	Control	MnO2
Liver	2.80±0.39	4.30±0.58^c)
Kidney	2.84±0.23	3.70±0.37^c)
Pancreas	2.04±0.23	2.75±1.01
Prostate gland	1.18±0.21	1.60±0.40
Spleen	0.40±0.06	0.85±0.30 b)
Brain	0.97±0.25	1.45±0.50
Hair	2.98±0.42	4.13±0.85 b)
Bone	1.66±0.32	2.75±0.25^c)
Muscle	0.37±0.04	0.63±0.10^c)

b) p < 0.05

c) p < 0.01 (Student’s t-test), i.e. statistically significantly different to control

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Intake rate decreased within the first month but then became constant in all groups.

Applicant's summary and conclusion

Conclusions:

Due to inconsistencies in the study, the certainty of the results for MnO2 are bought into question, and as such it is difficult to make solid conclusions. Given the low bioavailability of MnO2 (actually, the lowest for all manganese substances tested, see Anderson K, IUCLID section 7.12) and its insoluble nature ( 0.073 mg/L, See IUCLID section 4. 8 ) the raised Mn concentrations relative to the control could also be seen as unusual.

Executive summary:

The repeated dose toxicity of manganese dioxide was investigated in a study in which mice were exposed to MnO2 in the diet for 100 days and compared to controls fed on a diet containing 130 mg Mn/kg. The mice receiving MnO2 were fed an additional Mn dose of approximately 200 mg Mn/kg bw, daily. Thirty days into the exposure period, mice were tested for spontaneous motor activity. Mice were decapitated 24 hours after their last feed. Blood samples were collected and analysed. Furthermore, tissues were removed, weighed and analysed for Mn content.

There was no effect on food intake or body weight development between the controls and the group fed MnO2 during the course of the study. White blood cells (40.6 ± 9.9 x 10^2/mm³) ashowed a slight decrease compared to controls (59.3 ± 18.0 x 10^2/mm³); the difference was statistically significant (p < 0.05). Mn concentrations in the liver, kidney, spleen, hair, bone, and muscle were significantly increased in the MnO2 group compared to the controls. In the control group, motor activity increased from days 15-45, thereafter remaining constant. The MnO2 group showed significantly less activity than the control group.

Due to inconsistencies in the study, the certainty of the results for MnO2 are bought into question, and as such it is difficult to make solid conclusions; the findings from this study are therefore diregarded.