Manganese oxide

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

09-12-2009 to 05-01-2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP study conducted to current accepted guideline.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2010

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.2 (Acute Toxicity (Inhalation))

GLP compliance:

yes

Test type:

fixed concentration procedure

Limit test:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Manganese oxide

EC Number:

215-695-8

EC Name:

Manganese oxide

Cas Number:

1344-43-0

Molecular formula:

MnO

IUPAC Name:

oxomanganese

Details on test material:

- Name of test material: MnO
- Substance type: Green powder
- Physical state: Solid
- Impurities : Fe : Max- 77 ppm, Min-56 ppm. Ins ac: Max- 16 ppm, Min- 15ppm
- Composition of test material, percentage of components: Min- Mn:77.7% Max-Mn: 77.8% .Min- MnO2 :0.45 % Max-MnO2: 0.46%
- Purity test date: 28/09/08
- Lot/batch No.: 240908-25
- Storage condition of test material: Room temperature in the dark

Test animals

Species:

rat

Strain:

other: HsdHan: WIST

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Laboratories UK, Ltd. Bicester, Oxon, UK
- Age at study initiation: 8 to 12 weeks
- Weight at study initiation: The bodyweight varied between 200g to 357g*. * One male animal was slightly above the weight in the protocol (200g - 350g). This deviation was considered not to affect the purpose or validity of the study.
- Housing: Animals were housed in groups of five by sex in solid-floor polypropylene cages with stainless steel lids, furnished with softwood flakes.
- Diet : With the exception of the exposure period, free access to food (Harlan 2014 Rodent Diet, Harlan Laboratories UK Ltd, Oxon, UK) was allowed throughout the study.
- Water: With the exception of the exposure period, free access to mains drinking water was allowed throughout the study.
The diet, drinking water, bedding and chew blocks were routinely analysed and were considered not to contain any contaminants that could reasonably be expected to affect the purpose or integrity of the study.
- Acclimation period: A minimum of 5 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 to 25 °C
- Humidity (%): 30 to 70 %
- Air changes (per hr): A minimum of 15 changes per hour
- Photoperiod (hrs dark / hrs light): 12 hour cycle

Administration / exposure

Route of administration:

inhalation: dust

Type of inhalation exposure:

nose only

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Consisted of a SAG 410 Solid Aerosol Generator (TOPAS GmbH, Dresden, Germany) located adjacent to the exposure chamber

- Exposure chamber volume: The cylindrical exposure chamber had a volume of approximately 30 litres (dimensions: 28 cm diameter x 50 cm high).

- Method of holding animals in test chamber: Each rat was individually held in a tapered, polycarbonate restraining tube fitted onto a single tier of the exposure chamber and sealed by means of a rubber 'O' ring. Only the nose of each animal was exposed to the test atmosphere

- Source and rate of air: The SAG 410 was connected to a meter compressed air supply.

- Method of conditioning air: Homogeneity of the test atmosphere within the chamber was not specifically determined during the study. Chambers of the same design (ADG Developments Lts, Hitchin, Herts, UK) have been fully validated and shown to produce evenly distributed atmospheres in the animals breathing zone with a wide variety of test materials (Green J D et al, 1984).

- System of generating particulates/aerosols: A dust atmosphere was produced from the test material using a SAG 410 Solid Aerosol Generator (TOPAS GmbH, Dresden, Germany). A particulate separator was introduced before the aerosol entered the exposure chamber in order to remove large particles and thereby increase the inhalable portion of the generated aerosol.

- Method of particle size determination: The particle size of the generated atmosphere inside the exposure chamber was determined three times during the exposure period using a Marple Personal Cascade Impactor (Westech IS Ltd, Beds., UK). This device consisted of six impactor stages (9.0, 6.3, 4.0, 1.7, 0.81 and 0.30 µm cut points) with stainless steel collection substrates and a back up glass fibre filter, housed in an aluminium sampler. The sampler was temporarily sealed in a sampling port in the animals' breathing zone and a suitable, known volume of exposure chamber air was drawn through it using a vacuum pump. The collection substrates and backup filter were weighed before and after sampling and the weight of test material, collected at each stage, calculated by difference. The mean amount for each stage was used to determine the cumulative amount below each cut-off point size. In this way, the proportion (%) of aerosol less than 9.0, 6.3, 4.0, 1.7, 0.81 and 0.30 µm was calculated.

- Treatment of exhaust air: The extract from the exposure chamber passed through a 'scrubber' trap and was connected with a high efficiency filter to a metered exhaust system.

- Temperature, humidity, pressure in air chamber: The temperature and relative humidity inside the exposure chamber were measured by an electronic thermometer/ humidity meter (Hanna Instruments Ltd, Beds., UK) located in a vacent port in the animals' breathing zone of the chamber and recorded every thirty minutes throughtout the four-hour exposure period. Oxygen levels within the exposure chamber were measured by an electronic oxygen analyser (Servomex (UK) Ltd, Crowborough, East Sussex) located in a vacant port in the animals' breathing zone of the chamber and recorded every thirty minutes through out the four-hour exposure period. The test atmosphere was generated to contain at least 19% oxygen.


TEST ATMOSPHERE
- Samples taken from breathing zone: yes. The actual chamber concentration was measured at regular intervals during the exposure period. The gravimetric method used glass fibre filters placed in a filter holder. The holder was temporarily sealed in a vacant port in the exposure chamber in the animals' breathing zone and a suitable, known volume of exposure chamber air was drawn through the filter using a vacuum pump.



TEST ATMOSPHERE (if not tabulated)
- Particle size distribution: The resulting values were converted to probits and plotted against Log10 cut-point size. From this plot, the Mass Median Aerodynamic Diameter (MMAD) was determined (as the 50% point) and the geometric standard deviation was calculated. In addition the proportion (%) of aerosol less than 4µm (considered to be the inhalable fraction) was determined. See table 2.

CLASS METHOD (if applicable)
- Rationale for the selection of the starting concentration: During characterisation, a group of two rats (one male, one female) were exposed to an atmosphere of the test material at a mean achieved atmosphere concentration of 2.11 mg/L for four hours. No significant effects were noted for either animal.

Duration of exposure:

4 h

Concentrations:

5.35 mg/L

No. of animals per sex per dose:

5 Male and 5 Female

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: All animals were observed for clinical signs at hourly intervals during exposure, immediately on removal from the restraining tubes at the end of exposure, one hour after termination of exposure and subsequently once daily for fourteen days. Any deaths or evidence of overt toxicity was recorded at each concentration. Individual bodyweights were recorded prior to treatment on the day of exposure and on Days 7 and 14 or at death.
- Necropsy of survivors performed: yes. At the end of the fourteen day observation period the surviving animals were killed by intravenous overdose of sodium pentobarbitone. All animals, including the one that died during the study, were subjected to a full external and internal examination, and any macroscopic abnormalities were recorded. The respiratory tract was subjected to a detailed macroscopic examination for signs of irritancy or local toxicity.

Statistics:

Data evaluations included the relationship, if any, between the animals' exposure to the test material and the incidence and severity of all abnormalities including behavioural and clinical observations, necropsy findings, bodyweight changes, mortality and any other toxicological effects.
Using the mortality data obtained, an estimate of the acute inhalation median lethal concentration (LC50) of the test material was made.

Results and discussion

Preliminary study:

During characterisation, a group of two rats (one male, one female) were exposed to an atmosphere of the test material at a mean achieved atmosphere concentration of 2.11 mg/L for four hours. No significant effects were noted for either animal.

Effect levels

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 5.35 mg/L air (analytical)

Exp. duration:

4 h

Mortality:

No deaths occurred in a group of ten rats exposed to a mean achieved atmosphere concentration of 5.35 mg/L for four hours

Clinical signs:

other: Signs of hunched posture and pilo-erection are commonly seen in animals for short periods on removal from the chamber following 4-hour inhalation studies. Wet fur is commonly recorded both during and for a short period after exposure. Generalised fur stai

Body weight:

Individual bodyweights, together with weekly bodyweight changes, are given in table 9.
Variations in bodyweight gain are frequently seen for female animals of this strain and age during this type of study and, in isolation, are considered not to be significant.
All male animals and two females exhibited a bodyweight loss during Week 1 but recovered to show normal development during Week 2. Normal bodyweight development was noted for all other animals during the course of the study.

Gross pathology:

No macroscopic abnormalities were detected at necropsy

Other findings:

Nott reported

Any other information on results incl. tables

Table 3.The mortality data were summarised as follows:

 

Mean Achieved Atmosphere Concentration (mg/L)	Deaths
	Male	Female	Total
5.35	0/5	0/5	0/10

 

Table 4.Exposure Chamber Atmosphere Concentration

 

Duration of Exposure (minutes)	Net Weight of Sample (mg)	Volume of Air Sampled (L)	Chamber Flow Rate (L/min)	Atmosphere Concentration (mg/L)
2	9.17	2	60	4.59
16	10.18	2	60	5.09
30	13.88	2	60	6.94
46	13.63	2	60	6.82
59	9.06	2	60	4.53
75	7.98	2	60	3.99
90	11.09	2	60	5.55
105	11.51	2	60	5.76
120	9.15	2	60	4.58
135	9.01	2	60	4.51
150	7.16	2	60	3.58
165	12.41	2	60	6.21
181	13.91	2	60	6.96
195	12.77	2	60	6.39
210	10.58	2	60	5.29
225	9.04	2	60	4.52
235	11.21	2	60	5.61

 

Mean achieved atmosphere concentration (mg/L) = 5.35

Standard deviation = 1.05

Test Material Used (g)	108
Air Flow (L/min)	60
Total Generation Time (mins)	243
Nominal Concentration (mg/L)	7.40

 

Particle size distribution

 

Table 5. Cascade Impactor Data

 

Impactor Stage Number	Cut Point (µm)	Amount Collected (mg) per sample number			Mean Amount Collected (mg)
		1	2	3
3	9.0	0.05	0.06	0.00	0.04
4	6.3	0.28	0.30	0.17	0.25
5	4.0	0.81	0.85	0.50	0.72
6	1.7	0.46	0.45	0.32	0.41
7	0.81	0.16	0.19	0.08	0.14
8	0.30	0.01	0.05	0.02	0.03
Back-up filter	< 0.30	0.01	0.02	0.03	0.02
Total Mean Amount of Test Material Collected					1.61

 

Table 6.Calculation

 

Cut Point (μm)	Log10 Cut Point	Mean Cumulative Amount Less Than Cut Point
		(mg)	%	Probit
9.0	0.954	1.57	97.5	6.96
6.3	0.799	1.32	82.0	5.92
4.0	0.602	0.60	37.3	4.68
1.7	0.230	0.19	11.8	3.82
0.81	-0.092	0.05	3.11	3.14
0.30	-0.523	0.02	1.24	2.76

 

Mortality Data

 

Mean Achieved Atmosphere concentration (mg/L)	Sex	Deaths During Exposure	Deaths Post Exposure (1 Hour)	Deaths During Day of Observation								Total Deaths
				1	2	3	4	5	6	7	8-14
5.35	Male	0	0	0	0	0	0	0	0	0	0	0/10
	Female	0	0	0	0	0	0	0	0	0	0

 

Key To Clinical Observations

Fs = generalised green fur staining by the test material

H = hunched posture

P = pilo-erection

Ri = increased respiratory rate

RI = laboured respiration

Rn= noisy respiration

Sh = stained head

Wf= wet fur

O = no abnormalities detected

 

Table 7.Individual Clinical Observations (Day of Exposure)

 

Mean achieved atmosphere concentration(mg/L)	Animal number and sex	Hours during exposure			On removal From chamber	One hour post-exposure
		1	2	3
5.35	1 Male	Wf	Wf	Wf	Wf H P Ri Fs
	2 Male	Wf	Wf	Wf	Wf H P Ri Fs	Wf H P Ri Fs
	3 Male	Wf	Wf	Wf	Wf H P Ri Fs	Wf H P Ri Fs
	4 Male	Wf	Wf	Wf	Wf H P Ri Fs	Wf H P Ri Fs
	5 Male	Wf	Wf	Wf	Wf H P Ri Fs	Wf H P Ri Fs
	6 Male	Wf	Wf	Wf	Wf H P Ri Fs	Wf H P Ri Fs
	7 Male	Wf	Wf	Wf	Wf H P Ri Fs	Wf H P Ri Fs
	8 Male	Wf	Wf	Wf	Wf H P Ri Fs	Wf H P Ri Fs
	9 Male	Wf	Wf	Wf	Wf H P Ri Fs	Wf H P Ri Fs
	10 Male	Wf	Wf	Wf	Wf H P Ri Fs	Wf H P Ri Fs

 

Table 8.Individual Clinical Observation (Recovery Period)

 

Mean achieved atmosphere concentration (mg/L)	Animal number and sex	Days post exposure
		1	2	3	4	5	6	7	8-14
5.35	1 Male	H P Ri Fs	H Ri	Ri	0	0	0	0	0
	2 Male	H P Ri Rn Fs	H Ri	Ri	0	0	0	0	0
	3 Male	H P Ri Fs	H Ri	Ri	0	0	0	0	0
	4 Male	H P Ri Rn Fs	H Ri	Ri	0	0	0	0	0
	5 Male	H P Ri Fs	H Ri	Ri	0	0	0	0	0
	6 Male	H P Ri Fs	H Ri	Ri	0	0	0	0	0
	7 Male	H P Ri Rn Fs	H Ri	Ri	0	0	0	0	0
	8 Male	H P Ri Rn Fs	H Ri	Ri	0	0	0	0	0
	9 Male	H P Ri Rn Fs	H Ri	Ri	0	0	0	0	0
	10 Male	H P Ri Rn Fs	H Ri	Ri	0	0	0	0	0

 

 

Table 9.Individual Bodyweights

 

Mean achieved atmosphere concentration (mg/L)	Animal number and sex	Bodyweight (g) on Day:			Increment (g) During Week:
		0	7	14	1	2
5.35	1 Male	299	276	307	-23	31
	2 Male	311	303	348	-8	45
	3 Male	300	274	317	-26	43
	4 Male	292	261	304	-31	43
	5 Male	292	284	316	-8	32
	6 Male	218	225	237	7	12
	7 Male	220	229	236	9	7
	8 Male	219	208	221	-11	13
	9 Male	219	220	224	1	4
	10 Male	227	224	241	-3	17

 

 

Table 10.Individual Necropsy Findings

 

Mean Achieved Atmosphere Concentration (mg/L)	Macroscopic Observation	Animal Number and Sex
		1 Male	2 Male	3 Male	4 Male	5 Male	6 Male	7 Male	8 Male	9 Male	10 Male
5.35		N	N	N	N	N	N	N	N	N	N

 

 Table 11. Temperature and Relative Humidity in Exposure Chamber

 

Time (Minutes)	Chamber Temperature(°c) During Exposure	Chamber Relative Humidity (%) During Exposure
0	20	44
30	20	38
60	20	40
90	20	39
120	20	41
150	20	40
180	20	40
210	20	42
240	20	40

 

Table 12. Air Flow and Oxygen Concentration in Exposure Chamber

 

Time (Minutes)	Air Flow (L/min) During Exposure	Oxygen Concentration(%) During Exposure
-3	60	-
0	60	20.8
30	60	-
60	60	-
90	60	-
120	60	20.8
150	60	-
180	60	-
210	60	-
240	60	20.8

 

 

 

 

 

 

 

Applicant's summary and conclusion

Interpretation of results:

study cannot be used for classification

Conclusions:

No deaths occurred in a group of ten rats exposed to a mean achieved atmosphere concentration of 5.35 mg/L for four hours.
It was therefore considered that the acute inhalation median lethal concentration (4 hr LC50) of MnS, in the HsdHan:WIST stain rat, was greater than 5.34 mg/L.