Magnesium hydroxide sulfate (Mg6(OH)10(SO4)), hydrate (1:3)

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

26 October 2009 - 30 November 2009

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted to GLP in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2010

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test type:

standard acute method

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

-

EC Number:

483-390-9

EC Name:

-

Cas Number:

12508-61-1

Molecular formula:

H16Mg6O17S MgSO4 • 5Mg(OH)2 • 3H2O

IUPAC Name:

Magnesium hydroxide sulphate trihydrate

Test animals

Species:

rat

Strain:

other: HsdRccHan: WIST

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Laboratories LTD, Oxon, UK
- Age at study initiation: 8 - 12 weeks
- Weight at study initiation: 200 - 350g
- Fasting period before study: NDA
- Housing: The animals were housed in groups of five by sex in solid-floor polypropylene cages with stainless steel lids, furnished with softwood flakes (Datesand Ltd., Cheshire, UK) and provided with environmental enrichment items: wooden chew blocks and cardboard "fun tunnels" (Datesand Ltd., Cheshire, UK).
- Diet (e.g. ad libitum): With the exception of the exposure period, free access to food (Harlan 2014 Rodent Diet, Harlan Laboratories Ltd, Oxon, UK) was allowed throughout the study.
- Water (e.g. ad libitum): 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 are routinely analysed and are considered not to contain any contaminants that could reasonably be expected to affect the purpose or integrity of the study.
- Acclimation period: At least five days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 – 25 °C
- Humidity (%): 30 – 70% relative
- Air changes (per hr): At least 15 changes per hour
- Photoperiod (hrs dark / hrs light): 12 hours continuous light and 12 hours darkness

IN-LIFE DATES: At the end of the 14 day observation period the animals were killed by intravenous overdose of sodium pentobarbitone.

Administration / exposure

Route of administration:

inhalation: dust

Type of inhalation exposure:

nose only

Vehicle:

air

Details on inhalation exposure:

INHALATION EXPOSURE
ATMOSPHERE GENERATION
A dust atmosphere was produced from the test material using a SAG 410 Solid Aerosol Generator (TOPAS GmbH, Dresden, Germany) located adjacent to the exposure chamber. The SAG 410 was connected to a metered compressed air supply.
Compressed air was supplied by means of an oil free compressor and passed through a water trap and respiratory quality filters before it was introduced to the SAG 410.
The cylindrical exposure chamber had a volume of approximately 30 litres (dimensions: 28 cm diameter x 50 cm high). The concentration within the chamber was controlled by adjusting the test material feed rate from the SAG 410. The extract from the exposure chamber passed through a 'scrubber' trap and was connected with a high efficiency filter to a metered exhaust system. The chamber was maintained under negative pressure.
Homogeneity of the test atmosphere within the chamber was not specifically determined during this study. Chambers of the same design (ADG Developments Ltd, 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).
Prior to the start of the study, test material atmospheres were generated within the exposure chamber. During this characterisation period, grinding techniques and test material input rates were varied to achieve the required atmospheric concentrations.

EXPOSURE PROCEDURE
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 '0' ring. Only the nose of each animal was exposed to the test atmosphere.
Following an appropriate equilibration period a single group of ten rats (five males and five females) was exposed to an atmosphere of the test material for a period of four hours. A target concentration of 5.0 mg/L was used for the exposure. As the mean achieved concentration was 102% of target and no deaths occurred, no further levels were required.

SIGHTING EXPOSURE
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 1.88 mg/L for approximately four hours. No significant effects were noted for either animal.

EXPOSURE CHAMBER TEMPERATURE AND RELATIVE HUMIDITY
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 vacant port in the animals' breathing zone of the chamber and recorded every thirty minutes throughout the four-hour exposure period.

EXPOSURE CHAMBER OXYGEN CONCENTRATION
Oxygen levels within the exposure chamber were measured by an electronic oxygen analyser (Servomex (UK) Ltd, Crowborough, East Sussex) located in a port in the animals breathing zone during the four-hour exposure period. The test atmosphere was generated to contain at least 19% oxygen.

EXPOSURE CHAMBER ATMOSPHERE CONCENTRATION
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.
Each filter was weighed before and after sampling in order to calculate the weight of collected test material. The difference in the two weights, divided by the volume of atmosphere sampled, gave the actual chamber concentration.
The nominal chamber concentration was calculated by dividing the mass of test material used by the total volume of air passed through the chamber.

PARTICLE SIZE DISTRIBUTION
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.
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 4 µm (considered to be the inhalable fraction) was determined.

The particle size analysis of the atmosphere drawn from the animals' breathing zone, was as follows:

Mean Achieved Mean Mass Median Inhalable Fraction Geometric Standard
Atmosphere Aerodynamic Diameter (% <4 µm) Deviation
Concentration (mg/L) (µm)

5.10 2.91 60.5 3.34

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

4 h

Concentrations:

Exposure Chamber Concentration
The test atmosphere was sampled seventeen times during the exposure period and the actual concentration of the test material calculated. The mean values obtained were:
Atmosphere Concentration:
Mean Achieved (mg/L) Standard Deviation Nominal (mg/L)
5.10 0.60 12.7
The chamber flow rate was maintained at 60 L/min providing 120 air changes per hour. The theoretical chamber equilibration time (T99) was 3 minutes (Silver, 1946).

No. of animals per sex per dose:

5 MALE
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 evidence of overt toxicity were recorded at each observation. Individual bodyweights were recorded prior to treatment on the day of exposure and on Days 7 and 14.
- Necropsy of survivors performed: yes - At the end of the fourteen day observation period the animals were killed by intravenous overdose of sodium pentobarbitone. All animals 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:

EVALUATION OF DATA
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

Effect levels

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 5.1 mg/L air

Based on:

test mat.

Exp. duration:

4 h

Remarks on result:

other: No deaths occurred in a group of 10 rats exposed to a mean achieved atmosphere concentration of 5.10 mg/L for 4 hours.

Mortality:

No deaths occurred in a group of 10 rats exposed to a mean achieved atmosphere concentration of 5.10 mg/L for 4 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. These observations a

Body weight:

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.
Normal development was noted animals during the course of the study.

Gross pathology:

No macroscopic abnormalities were noted amongst animals at necropsy.

Any other information on results incl. tables

The mean achieved atmosphere concentration was as follows:

Atmosphere Concentration
Mean Achieved (mg/L)	Standard Deviation	Nominal (mg/L)
5.10	0.60	12.7

 

The characteristics of the achieved atmosphere were as follows:

Mean Achieved Atmosphere Concentration (mg/L)	Mean Mass Median Aerodynamic Diameter (µm)	Inhalable Fraction (% <4µm)	Geometric Standard Deviation
5.10	2.91	60.5	3.34

 

The mortality data were summarised as follows:

Mean Achieved Atmosphere Concentration (mg/L)	Deaths
	Male	Female	Total
5.10	0/5	0/5	0/10

References

Green J D et al (1984) Effect of Equilibration Zones on Stability, Uniformity and Homogeneity Profiles of Vapours and Aerosols in the ADG Nose Only Inhalation Exposure System. Fundamental and Applied Toxicology 4, 768-777.

Silver S D (1946) Constant flow gassing chambers: Principles influencing design and operation. J Lab Clin Med 31, 1153-1161.

Applicant's summary and conclusion

Interpretation of results:

not classified

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

No deaths occurred in a group of ten rats exposed to a mean achieved atmosphere concentration of 5.10 mg/L for four hours. It was therefore considered that the acute inhalation median lethal concentration (4 hr LC50) of Experimental 20829-95, in the HsdRccHan : WIST strain rat, was greater than 5.10 mg/L.

Executive summary:

A study was performed to assess the acute inhalation toxicity of the test material. The method used followed that described in the OECD Guidelines for Testing of Chemicals (1981) No. 403 "Acute Inhalation Toxicity" referenced as Method B2 (Inhalation) of Commission Regulation (EC) No. 440/2008. The method was also designed to satisfy the US Environmental Protection Agency (EPA) Health Effects Test Guidelines, OPPTS 870.1300, Acute Inhalation Toxicity, August 1998.

No deaths occurred in a group of ten rats exposed to a mean achieved atmosphere concentration of 5.10 mg/L for four hours. It was therefore considered that the acute inhalation median lethal concentration (4 hr LC50) of Experimental 20829-95, in the HsdRccHan^TM: WIST strain rat, was greater than 5.10 mg/L.