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Diss Factsheets

Toxicological information

Acute Toxicity: inhalation

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Administrative data

acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
September 2010
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study conducted according to Guidelines in a GLP certified laboratory.

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guidelineopen allclose all
according to guideline
OECD Guideline 403 (Acute Inhalation Toxicity)
according to guideline
EU Method B.2 (Acute Toxicity (Inhalation))
according to guideline
EPA OPPTS 870.1300 (Acute inhalation toxicity)
GLP compliance:
Test type:
acute toxic class method

Test material

Constituent 1
Chemical structure
Reference substance name:
Magnesium hydroxide
EC Number:
EC Name:
Magnesium hydroxide
Cas Number:
Molecular formula:
magnesium dihydroxide
Details on test material:
- Name of test material: Magnesium hydroxide
- Molecular formula: Mg(OH)2
- Molecular weight: 58.32
- Physical state: solid
- Storage condition of test material: At room temperature in the dark

Test animals

Details on test animals or test system and environmental conditions:
Rat: Crl:WI(Han) (outbred, SPF-Quality)
Recognised by international guidelines as the recommended test system (e.g. OECD, EC).
Source: Charles River Deutschland, Sulzfeld, Germany.
Number of animals
5 males and 5 females (females were nulliparous and non-pregnant) per exposure level.
Age and body weight
Young adult animals were selected (approximately \ weeks old).
Animals used within the study were of approximately the same age and body weight variation did not exceed +/- 20% of the sex mean.
Health inspection
A health inspection was performed prior to commencement of treatment, to ensure that the animals were in a good state of health.

Administration / exposure

Route of administration:
inhalation: aerosol
Type of inhalation exposure:
whole body
Details on inhalation exposure:
Test atmosphere generation
Administering the test substance to a stream of dry pressurized air using a combination of a spiral feeder and air mover generated an aerosol. The aerosol was passed through a cyclone, allowing larger particles to settle, before it entered the exposure chamber (Appendix 1, Figure 1). The mean total airflow was 47 L/min. From the exposure chamber the test atmosphere was passed through a filter before it was released to the exhaust of the fume hood.

Nominal concentration
The nominal concentration was calculated by dividing the amount of test substance used by the volume of pressurized air (average air flow times exposure time) entering the exposure chamber used for exposure of the animals.

Actual concentration
The actual concentration was determined twelve times during the exposure period. Samples were drawn from the test atmosphere through a tube mounted in one of the free animal ports of the middle section of the exposure chamber. Samples were drawn through a glass fiber filter (type APFC04700, Millipore, Billerica, MA, USA). The collected amount of the test substance in the air sample was measured gravimetrically. Sample volumes were measured by means of a dry gas meter (type G 1.6, Actaris Meterfabriek B.V., Dordrecht, The Netherlands).

Subsequently the mean concentration with the standard deviation was calculated.

The particle size distribution was characterized twice during the exposure period. The samples were drawn (2 L/min) from the test atmosphere through a tube mounted in one of the free animal ports of the middle section of the exposure chamber (Appendix 1, Figures 1 and 2). The samples were collected with an 8 stage Marple personal cascade impactor containing fiber glass filters (SKC 225-713, fiber glass, SKC Omega Specialty Division, Chelmsford, MA, USA) and a fiber glass back-up filter (SEC-290-GFS, Westech, Upper Stondon, Bedfordshire, England). Amounts of test substance collected were measured gravimetrically. Subsequently the Mass Median Aerodynamic Diameter (MMAD) and the Geometric Standard Deviation (GSD) were determined.
Analytical verification of test atmosphere concentrations:
The collected amount of the test substance in the air sample was measured gravimetrically. Sample volumes were measured by means of a dry gas meter (type G 1.6, Actaris Meterfabriek B.V., Dordrecht, The Netherlands).
Duration of exposure:
4 h
The mean actual concentration was 2.1 ± 0.47 mg/L. The nominal concentration was 21.7 mg/L resulting in a generation efficiency (ratio of actual and nominal concentration) of 10%. The concentration measurements distributed over time showed that the substance was sufficiently stable
No. of animals per sex per dose:
5 males and 5 females
Control animals:
Details on study design:
- Duration of observation period following administration: 15 days
- Frequency of observations and weighing: Days 1 (pre-administration), 2, 4, 8 and 15.
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs, body weight,organ weights, histopathology, other: On Day 1, one and three hours after exposure and once daily thereafter until Day 15.
No statistical analysis was performed.

Results and discussion

Effect levels
Dose descriptor:
Effect level:
> 2.1 mg/L air
Based on:
test mat.
Exp. duration:
4 h
No mortality occurred.
Clinical signs:
other: No clinical signs were noted during exposure. After exposure, ptosis and/or piloerection were noted in two males and one female on Day 1 only.
Body weight:
Overall body weight gain in males and females was within the range expected for rats of this strain and age used in this type of study.

Applicant's summary and conclusion

Interpretation of results:
practically nontoxic
Migrated information Criteria used for interpretation of results: OECD GHS
The inhalatory LC50, 4h value of Magnesium hydroxide in Wistar rats was established to exceed 2.1 mg/L.
Executive summary:

Groups of 5 male and female Wistar rats were treated with Magnesium hydroxide as aerosol during 4 hours. No mortality or other relevant adverse effects were observed. An inhalatory LC50 (4h)value for magnesium hydroxide exceeding 2.1 mg/L was determined, being this value the maximum feasible concentration that could be tested.