Magnesium hydroxide

Endpoint summary

Description of key information

A combined repeated dose reproductive toxicity screening study (OECD 422) study was performed with magnesium hydroxide to assess sub-acute oral toxicity in rats. No test substance related effects were observed at the highest dose tested which was equal to the limit dose for the repeated dose toxicity test of 1000 mg/kg bw.

No data is available to assess the sub-chronic toxicity of the target substance. Therefore, available data from a sub-chronic repeated dose toxicity study conducted with a suitable read-across partner was used in a weight-of-evidence approach to assess the specific target organ toxicity of the target substance. Based on the results, no classification for specific target organ toxicity is warranted for magnesium hydroxide.

Key value for chemical safety assessment

Toxic effect type:

dose-dependent

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Reference 1

Endpoint:

sub-chronic toxicity: oral

Type of information:

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

Adequacy of study:

weight of evidence

Justification for type of information:

For details and justification of read-across please refer to the attached report in section 13 of IUCLID.

Reason / purpose for cross-reference:

read-across source

Clinical signs:

no effects observed

Description (incidence and severity):

No overt signs of toxicity or changes in behavior were noted during routine daily observation

Mortality:

mortality observed, non-treatment-related

Description (incidence):

All animals survived until the scheduled termination date, with one exception.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

The mean body weights of both sexes given a diet containing magnesium chloride at the dose level of 5% throughout the experiment period were significantly decreased as compared with those fed the control diet. Fasted body weights before sacrifice were significantly decreased for males fed 1.25% or above, and for females fed 5% magnesium chloride.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

Food consumption data for all magnesium chloride treated groups were essentially similar to the control group values. However, total material intakes for female mice were greater than for male mice given the same doses

Food efficiency:

not examined

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

no effects observed

Description (incidence and severity):

Water intake data for all magnesium chloride treated groups were essentially similar to the control group values.

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Description (incidence and severity):

No treatment-related adverse effects were found regarding the results for hematology.

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

No treatment-related adverse effects were found regarding the results for blood biochemistry.

Endocrine findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Increased relative brain weights in males given 2.5% or above and females given 5%, kidney weights in both sexes receiving 2.5 or 5%, and testes of males given 2.5% or above appeared to be related to retardation of body weight increase. Increased heart weights in males given 0.6% or above (except for 5%), and decreased spleen weights in males receiving 2.5 or 5% were also observed. No significant change was seen in the liver.

Gross pathological findings:

no effects observed

Description (incidence and severity):

No macroscopic lesions were observed in either sex of any of the groups.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

Light microscopic examination revealed treatment-related changes in the kidneys. Significantly increased vacuolar lesions appeared in the proximal tubules, especially in the P1 and P2 segments of males, but not females, given the 5% concentration. Squamous cell hyperplasia of the forestomach sporadically developed in some mice of both sexes, given the test chemical. However, this finding was not dose-dependent, and was therefore not considered of toxicological significance. No other microscopic lesions which could be unequivocally attributed to the magnesium chloride administration were apparent in any organs or tissues.

Histopathological findings: neoplastic:

no effects observed

Other effects:

not examined

Details on results:

No treatment related effects were noted at any dose levels for survival, clinical observation, hematology or blood biochemistry. The average body weights of both sexes fed the diet containing 5% magnesium chloride were lower than those fed the control diet. Significant increases in the relative weights of some organs were observed in both sexes of the 2.5 and 5 % groups. However, no blood biochemical or histopathological changes were found. A significant decrease in the relative spleen weight was noted in the male 2.5 and 5% groups. Organ weight changes were considered to be simply related to the lower body weight, since no hematological or histopathological alterations were seen. Renal cell vacuolation was found in high dose males (but not in females). This change might reflect reabsorption of magnesium, but as this alteration was not linked with change in any blood biochemical parameters indicating renal failure, its toxicological significance was considered to be minimal.
For detailed results see Tables 1-3 in "Any other information on results incl. tables".

Key result

Dose descriptor:

NOAEL

Effect level:

6 810 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

female

Basis for effect level:

body weight and weight gain

Key result

Dose descriptor:

NOAEL

Effect level:

2 690 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male

Basis for effect level:

histopathology: non-neoplastic

Critical effects observed:

not specified

Table 1: Average food consumption, material and water intakes for B6C3F1 mice fed magnesium chloride for 13 weeks

Dietary level (%)	Average food consumption (g/mouse/day)	Material intake		Average water intake (g/mouse/day)
		Average (g/kg/day)	Total (g/kg)
Males
0	6.9	-	-	11.0
0.3	6.4	0.61	55.9	9.7
0.6	6.5	1.22	110.8	11.0
1.25	6.7	2.69	245.2	10.7
2.5	6.7	5.41	492.6	10.2
5	6.4	11.40	1037.5	9.4
Females
0	6.5	-	-	6.5
0.3	6.3	0.77	70.3	5.9
0.6	6.4	1.58	143.7	6.0
1.25	6.5	3.26	296.6	6.0
2.5	6.6	6.81	612.0	6.4
5	6.3	13.83	1258.9	7.4

Table 2: Final body and organ weights for B6C3F1 mice fed magnesium chloride for 13 weeks

Dietary level (%)	Number of mice examined	Final body weight (g)	Organ weight (% body weight)
			Brain	Heart	Liver	Spleen	Kidneys	Testes/Ovaries
Males
0	10	33.9± 1.6(a)	1.48 ± 0.10	0.55 ± 0.03	4.67 ± 0.54	0.38 ± 0.05	1.85 ± 0.21	0.75 ± 0.05
0.3	10	31.7 ± 1.3**	1.53 ± 0.09	0.56 ± 0.05	4.31 ± 036	0.34 ± 0.04*	1.71 ± 0.13	0.78 ± 0.04
0.6	9	32.9 ± 2.0	1.53 ± 0.04	0.59 ± 0.04*	4.69 ± 0.29	0.39 ± 0.09	1.85 ± 0.07	0.77 ± 0.04
1.25	10	31.9 ± 1.7*	1.51 ± 0.06	0.60 ± 0.07*	4.80 ± 0.48	0.39 ± 0.08	1.96 ± 0.14	0.77 ± 0.04
2.5	10	31.4 ± 1.0**	1.58 ± 0.06*	0.64 ± 0.07**	4.43 ± 0.25	0.33 ± 0.05*	2.03 ± 0.10*	0.81 ± 0.04*
5	10	28.8 ± 1.7**	1.68 ± 0.09**	0.58 ± 0.06	4.24 ± 0.26	0.27 ± 0.04**	2.22 ± 0.16**	0.83 ± 0.06**
Females
0	10	27.4 ± 1.8	1.87 ± 0.11	0.55 ± 0.07	4.34 ± 0.36	0.34 ± 0.05	1.52 ± 0.09	0.13 ± 0.04
0.3	10	26.6 ± 1.2	1.96 ± 0.13	0.60 ± 0.07	4.52 ± 0.37	0.36 ± 0.02	1.67 ± 0.17*	0.12 ± 0.02
0.6	10	26.5 ± 1.7	1.88 ± 0.09	0.57 ± 0.06	4.26 ± 0.19	0.35 ± 0.03	1.61 ± 0.13	0.12 ± 0.04
1.25	10	27.2 ± 1.6	1.88 ± 0.14	0.62 ± 0.09	4.33 ± 0.64	0.37 ± 0.05	1.60 ± 0.10	0.15 ± 0.04
2.5	10	26.5 ± 1.8	1.91 ± 0.13	0.57 ± 0.05	4.26 ± 0.15	0.34 ± 0.03	1.71 ± 0.13**	0.12 ± 0.04
5	10	24.7 ± 1.2**	2.08 ± 0.11	0.63 ± 0.10	4.36 ± 0.25	0.34 ± 0.03	1.80 ± 0.17**	0.15 ± 0.03

(a) Mean ± SD

* Significantly different from respective control value at P < 0.05

** Significantly different from respective control value at P < 0.01

Table 3: Histopathological results for B6C3F1 male mice fed magnesium chloride for 13 weeks

Organ/finding	Male
Dietary level (%)	0	0.3	0.6	1.25	2.5	5
Number of mice examined	10	10	9	10	10	10
Kidneys/Vacuolation(a)
Slight	1	0	0	1	2	4**
Moderate	1	0	0	0	0	5**
Severe	0	0	0	0	0	1**

(a) This finding appeared mainly in P1 and P2 segments of proximal tubules

**Significantly different from control values at P<0.01

Conclusions:

Based on these results, a No Observed Adverse Effect Level (NOAEL) of 6810 mg/kg body weight/day for females and 2690 mg/kg body weight/day for males was determined.

Executive summary:

In a 13-week sub-chronic study conducted similar to guideline OECD 408, magnesium chloride hexahydrate (98% purity) was administered by feed to B6C3F mice (10/sex/dose) at dietary levels of 0 (control), 0.3, 0.6, 1.25, 2.5 and 5% for 13 weeks.

In both sexes of the 5% treatment group, a decrease in body weight was observed. While clinical signs and hematological or blood biochemistry parameters showed no treatment-related effects, histopathologically, vacuolation of kidney tubular cells was apparent in males of the 2.5 and 5% concentration groups.  

Significant increases in the relative weights of some organs were observed in both sexes of the 2.5 and 5% groups, but no blood biochemical or histopathological changes were found. Significant decrease of the relative spleen weight was apparent in the male 2.5 and 5% groups. However, since no hematological or histopathological alterations were seen these organ weight changes were considered to be simply related to the lower body weight.

Based on these results, a No Observed Adverse Effect Level (NOAEL) of 2.5% (equals to 6810 mg/kg body weight/day) for females and 1.25% (equals to 2690 mg/kg body weight/day) for males was determined, which is equal to 1954 mg/kg bw/day and 772 mg/kg bw/day magnesium hydroxide.

This information is used in a read-across approach in the assessment of the target substance. For details and justification of read-across please refer to the attached report in section 13 of IUCLID.

This information is used in a read-across approach in the assessment of the target substance. For details and justification of read-across please refer to the attached report in section 13 of IUCLID.

Reference 2

Endpoint:

short-term repeated dose toxicity: oral

Remarks:

combined repeated dose and reproduction / developmental screening

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2010-03-02 to 2010-09-01

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

Version / remarks:

March 1996

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: The EPA Health Effects Test Guidelines, OPPTS 870.3650, Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test, July 2000

Version / remarks:

July 2000

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Commision Regulation (EC) No 440/2008 Part B:Methods for the Determination of Toxicity and other Heallth Effects; B.7: "Repeated Dose (28 days) Toxicity (oral)". Official Journal of the European Union No. L142, May 2008

Version / remarks:

May 2008

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity Study in Rodents)

Version / remarks:

October 2008

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: EPA OPPTS 870.3050( repeated Dose 28-day oral toxicity study in rodents)

Version / remarks:

July 2000

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Specific details on test material used for the study:

- Name of the test material used in the report: Magnesium hydroxide
- Appearance: white powder
- Batch No.: 20BR0026
- Purity: 99.90%
- Storage: at room temperature in the dark
- Expiry date: 2012-01-31

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories france, L'Arbresle Cedex, France.
- Age at study initiation: Approximately 11 weeks
-Weight at study initiation: Males and females were weighed on the first day of exposure and weekly thereafter. Mated females were weighed on Days 0, 4, 7, 11, 14, 17 and 20 post-coitum, and during lactation on days 1 and 4. Live pups were weighed on days 1 and 4 of lactation.
-Health check: A health inspection was performed prior to commencement of treatment to ensure that the animals were in a good state of health.
-Housing: Pre-mating: Animals were housed in groups of 5 animals/sex/cage in Macrolon cages (MIV type, height 18cm).
Mating: Females were caged together with males on a one-to-one basis in Macrolon cages ( MIII type, height 18cm)
Post-mating: Males were housed in their home cage (macrolon cages, MIV type, height 18cm) with a maximum of 5 animals per cage. Fema les were individually housed in Macrolon cages (MIII type, height 18cm).
Lactation: Pups were kept with the dam until termination in Macrolon cages( MIII type, height 18cm)
General: Sterilised sawdust as bedding material and paper as cage-enrichment were supplied. During activity monitoring animals were ho used individually in Macrolon cages (MIII type; height 15cm) with sterilised sawdust as bedding material. No cage-enrichment was provide d during activity monitoring.
-Number of animals: 40 females and 40 males.
- Diet : free access to pelleted rodent diet.
- Water : Free access to tap water.
- Acclimation period: At least 5 days prior to start of treatment.

ENVIRONMENTAL CONDITIONS
Animals were housed in a controlled environment.
- Temperature (°C): 21 ± 3°C ( actual range: 19.7-21.7 °C)
- Humidity (%): A relative humidity of 40-70% (actual range: 34-73%)
- Air changes (per hr): Approximately 15 air changes per hour
- Photoperiod (hrs dark / hrs light): 12 hours artificial light and 12 hours darkness per day.

Route of administration:

oral: gavage

Details on route of administration:

Oral gavage, using a plastic feeding tube. Formulations were placed on a magnetic stirrer during dosing.

Vehicle:

water

Details on oral exposure:

VEHICLE
- Justification for use and choice of vehicle: Based on trial formulations performed at NOTOX and on information provided by the sponsor.
- Method of Formulation: Formulations were prepared daily within 6 hours prior to dosing and were homogenised to a visually accepted level.
-Rationale for dose levels: Based on the results of a 10-day dose range finding study the dose levels for this combined 28-day oral gavage with reproduction/developmental toxicity screening test were selected to be 110, 330 and 1000 mg/kg.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

-Formulation analysis showed that the formulations were prepared accurately and homogenously.
Chemical analysis of dose preparations:
-Analyses were conducted during the treatment phase, according to a validated method. Samples of formulations were analysed for homogenity and accuracy of preparation. The accuracy of preparation was considered acceptable if the mean measured concentrations were 85-115% of the target concentration. Homogeneity was demonsrated if the coefficient of variation was <= 10%.
Analytical conditions: Instrument Agilent 7500CE (Agilent Technologies, Tokyo, Japan)
Cone: Nickel or Platinum
Plasma forward power: 1500 W
Peripump flow rate: 0.08 rps
Nebulizer
Type :MicroMist
Material:quartz
Spray chamber
Material: quartz
Temperature: 15 °C
Torch :2.5 mm i.d.
Detection of Magnesium
Reaction gas: none
Integration time: 0.1 seconds per replicate
Replicates per analysis: 5
Quantitation m/z: 24

Duration of treatment / exposure:

Males were exposed for 29 days, i.e. 2 weeks prior to mating, during mating, and up to termination. Females were exposed for 41-45 days i.e. during two weks prior to mating, during mating, during post-coitum, and during at least 4 days of lactation. Females 41, 46, 48, 49 ( Group 1, table 1), 53, 59 ( Group 2, table 1), 61,62, 68 ( Group 3, table 1) and 76 ( Group 4, table 1) were not dosed during littering.

Frequency of treatment:

Once daily for 7 days per week, approximately the same time each day with a maximum of 6 hours difference between the earliest and latest dose. Animals are dosed up to the day prior to scheduled necropsy.
-Pups were not treated directly, but were potentially exposed to the test substance in utero and through lactational transfer

Dose / conc.:

0 mg/kg bw/day (nominal)

Remarks:

Control

Dose / conc.:

110 mg/kg bw/day (nominal)

Remarks:

Low dose

Dose / conc.:

330 mg/kg bw/day (nominal)

Remarks:

Mid dose

Dose / conc.:

1 000 mg/kg bw/day (nominal)

Remarks:

High dose

No. of animals per sex per dose:

Four groups of ten male and ten female Wistar (Hans) rats were exposed by oral gavage to the test substance.

Control animals:

yes, concurrent no treatment

Details on study design:

- Dose selection rationale:Based on the results of a 10-day dose range finding study the dose levels for this combined 28-day oral gavage study with reproduction/developmental toxicity screening test were selected to be 110, 330 and 1000 mg/kg.
- Rationale for animal assignment: This species and strain of rat has been recognised as appropriate for general and reproduction toxicity studies. The animal model has been proven to be susceptible to the effects of reproductive toxicants.

Observations and examinations performed and frequency:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily detailed clinical observations were made in all animals immediately after dosing. Once prior to the start of treatment and at weekly intervals this was also performed outside the home cage in a standard arena. Arena observations were not performed when the animals were mating, or housed individually.

BODY WEIGHT: Yes
- Time schedule for examinations: Males and females were weighed on the first day of exposure and weekly thereafter. Mated females were weighed on Days 0, 4, 7, 11, 14, 17 and 20 post-coitum, and during lactation on Days 1 and 4 of lactation.

FOOD CONSUMPTION:
- Food consumption : Weekly,except for males and females which were housed together for mating. Food concumption of mated females was measured on Days 0, 4, 7, 11, 14, 17 and 20 post-coitum, and during lactation on Days 1 and 4.


WATER CONSUMPTION : Yes
- Time schedule for examinations: Subjective appraisal was maintained during the study, but no quantitative investigation was introduced as no effect was suspected.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Blood samples were collected from the 5 animals/sex/group (see table 2) immediately prior to scheduled post mortem examination, between 7.00 and 10.30 a.m.
- Anaesthetic used for blood collection: Yes isoflurane anaesthesia was used for blood collection
- Animals fasted: Yes animals were fasted overnight before blood sampling but w ater was provided.

URINALYSIS: Yes
- Time schedule for collection of urine: Urine samples were collected overnight ( approximately 15-24 hrs) from the 5 selected males/group ( see table 2).
- Metabolism cages used for collection of urine: Yes urine was collected into a specimen vial, using a metabolism cage.
- Animals fasted: Yes animals were deprived of food but water was provided.

Sacrifice and pathology:

PATHOLOGY: Yes
-Necropsy parental animals: All animals were fasted overnight prior to planned necropsy, but water was provided. Animals survivng to the scheduled necropsy were deeply anaesthetised using iso-flurane vapor and subsequently exsanguinated.
Necropsy was coducted on the following days:
Condition Day of necropsy
Females which delivered Lactation Days 5-6
Males Following completion of the mating period ( 29 days of dose administration).

All animals were subjected to macroscopic examination (including examination of the body surface, orifices and cranial, thoracic and abdominal tissues and organs and their contents), with special attention being paid to the reproductive organs. Pups survivng to planned termination were decapitated on lactation Day 5 or 6.
All pups were sexed and descriptions of all external abnormalities were recorded. The stomach was examined for the presence of milk. If possible, defects or cause of death were evaluated. Any abnormal pup, organ or tissue was preserved in 10% buffered formalin for possible further examination.

HISTOPATHOLOGY: Yes
The following slides were examined by a pathologist:
-The preserved organs and tissues of the selected 5 animals/sex of groups 1 and 4( see table 1).
-The additional slides of the testes of the selected 5 males of Groups 1 and 4 to examine staging of spermatogenesis( see table 2).
-All gross lesions of all animals ( all dose groups).
All abnormalities were described and included in the report. An attempt was made to correlate gross observations with microscopic findings.

Statistics:

The following statistical methods were used to analyze the data:
- If the variables could be assumed to follow a normal distribution, the Dunnett-test (Ref. 2; many-to-one t-test) based on a pooled variance estimate was applied for the comparison of the treated groups and the control groups for each sex.
- The Steel-test (Ref. 3; many-to-one rank test) was applied if the data could not be assumed to follow a normal distribution.
- The Fisher Exact-test (Ref. 4) was applied to frequency data.

All tests were two-sided and in all cases p < 0.05 was accepted as the lowest level of significance.

Clinical signs:

no effects observed

Description (incidence and severity):

No clinical signs of toxicity were noted during the observation period. Incidental findings that were noted in single females included alopecia pr piloerection. These findings occurred within the range of background findings to be expected for rats of this age and strain which are housed and treated under the conditions in this study. At the incidence observed, these were considered signs of no toxicological relevance.

Mortality:

no mortality observed

Description (incidence):

No mortality occurred during the study period.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

Body weights and body weight gain of treated animals remained in the same range as controls over the treatment period.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

Food consumption before or after allowance for body weight was similar between treated and control animals.

Food efficiency:

not specified

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

not specified

Ophthalmological findings:

not examined

Haematological findings:

effects observed, non-treatment-related

Description (incidence and severity):

No toxicologically relevant changes occurred in haematological parameters of treated rats. Any statistically significant changes were considered to be of no toxicological relevance as they occurred in the absence of a treatment-related distribution and remained within the range considered normal for rats of this age and strain. These changes consisted of lower red blood cell counts in males at 1000 mg/kg, higher mean corpuscular volume (MCV) and/or higher mean corpuscular haemoglobin levels (MCH) in males at 110 and 1000 mg/kg, higher reticulocyte counts in females at 110 mg/kg (due to female no.52) and lower mean corpuscular haemoglobin concentration (MCHC) in females at 110 and 100 mg/kg.

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

The following statistically significant changes in clinical biochemistry parameters distinguished treated animals from control animals:
-Lower total protein levels in males at 330 and 1000 mg/kg,
-Lower albumin levels in males at 1000 mg/kg
-Lower calcium levels in males at 330 and 1000 mg/kg.
Means of these changes only just exceeded or remained within the range considered normal for rats of this age and strain.
Any other statistically significant changes were not considered to be toxicologically relevant as they occurred in the absence of a treatment-related trend and/or remained within the range considered normal for rats of this age and strain. These included lower or higher urea levels in males at 110 and 330 mg/kg respectively, higher potassium values in males at 110 and 330 mg/kg, and higher cholesterol and potassium levels in females at 110 and 330 mg/kg respectively.

Endocrine findings:

not examined

Urinalysis findings:

effects observed, treatment-related

Description (incidence and severity):

The following statistically significant changes in urinary parameters distinguished treated males from control males:
- Lower sodium excretion (mmol/TPV) at 330 and 1000 mg/kg,
- Lower potassium excretion (mmol/TPV) at 1000 mg/kg,
- Higher calcium concentration (mmol/L) at 1000 mg/kg.
Means of these changes only just exceeded or remained within the range considered normal for rats of this age and strain. The significant higher specific gravity seen at 330 mg/kg was not considered to be toxicologically relevant as it occurred in the absence of a dose-related trend.

Behaviour (functional findings):

effects observed, non-treatment-related

Description (incidence and severity):

Hearing ability, pupillary reflex, static righting reflex and grip strength were normal in all animals. The variation in motor activity did not indicate a relation with treatment.

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, non-treatment-related

Description (incidence and severity):

No toxicologically relevant changes were noted in organ weights and organ to body weight ratios.
The significantly lower absolute thymus weight observed for females at 1000 mg/kg was considered to be due a low weight for female no. 72. Individual weights of other females of this dose group remained within the range observed among other treated females. The higher testes to body weight ratio of males at 110 mg/kg and the lower liver to body weig ht ratios of males at 110 and 1000 mg/kg occurred in the absence of a dose-related trend and means remained within the normal range for rats of this age and strain. These changes were therefore considered to be of no toxicological relevance.

Gross pathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

Macroscopic observations at necropsy did not reveal any alterations that were considered to have arisen as a result of treatment.
Incidental findings among control and treated animals included red foci on the stomach glandular mucosa or thymus, red discoloration of the mandibular lymph node and thymus, reduced size of the thyroid, a gray-white focus on or dark red discoloration of the papillary process of the liver, papillary process grown together with the left lateral lobe, enlarged clitoral glands, greenish soft nodule or tan focus on the clitoral glands, a yellowish hard or soft nodule on the tail of the epididymis, pelvic dilation of the kidneys and alopecia. The incidence of these findings was within the background range of findings that are encountered among rats of this age and strain and did not show a dose-related trend. These necropsy findings were therefore considered to be of no toxicological relevance.

Neuropathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

There were no treatment related microscopic findings.
Recorded microscopic findings were within the range of background pathology encountered in Wistar (Han) rats of this age in this type of study and occurred at similar incidences and severity in both control and treated rats. The spermatogenic staging profiles were normal for all group 1 and group 4 males evaluated.

Histopathological findings: neoplastic:

no effects observed

Key result

Dose descriptor:

NOAEL

Effect level:

>= 1 000 mg/kg bw/day (nominal)

Sex:

male/female

Basis for effect level:

other: see 'Remark'

Critical effects observed:

not specified

Table 4: Clinical signs Males parental animals

		Pre-Mating		Reproduction period
Sign (Max Grade)	Week	1	2	1	2	3	4
Location	day	1,2,3,4,5,6,7	1,2,3,4,5,6,7	1,2,3,4,5,6,7	1,2,3,4,5,6,7	1,2,3,4,5,6,7	1,2,3,4,5,6,7,1,2,3
Group 1 (control) No clinical signs noted		-	-	-	-	-	-
Group 2 (110 mg/kg) No clinical signs noted		-	-	-	-	-	-
Group 3 (330 mg/kg) No clinical signs noted		-	-	-	-	-	-
Group 4 (1000 mg/kg) No clinical signs noted		-	-	-	-	-	-

 

Table 5: Clinical signs Females parental animals

		Pre-Mating		Reproduction Period
Sign (Max Grade)	Week	1	2	1	2	3	4
Location	Day	1,2,3,4,5,6,7	1,2,3,4,5,6,7	1,2,3,4,5,6,7	1,2,3,4,5,6,7	1,2,3,4,5,6,7	1,2,3,4,5,6,7,1,2,3
Group 1 (control) No clinical signs noted		-	-	-	-	-	-
Group 2 (110 mg/kg) Skin/ fur  Alopecia	G:   %:	-   -	-   -	-   -	1,1,1,1,1,1,1   1,1,1,1,1,1,1	1,1,1,1,1,1,1   1,1,1,1,1,1,1	1,1,1,1,1,1,1   1,1,1,1,1,1,1
Group 3 (330 mg/kg) Skin/fur  Piloerection	G:   %:	-   -	-   -	1   1	-   -	-   -	-   -
Group 4 (1000 mg/kg) No clinical signs noted		-	-	-	-	-	-

Key:

G: Median value of the highest individual daily grades

%: Percent of affected animals (0= less than 5%, 1= between 5% and 15%, A= more than 95%)

-        : observation performed, no sign detected

Table 6: Body weights (g) Summary: Parental Males/Females 

		Group 1 Control		Group 2 110 mg/kg		Group 3 330 mg/kg		Group 4 1000 mg/kg
		Male	Female	Male	Female	Male	Female	Male	Female
Pre-mating
Day 1	Mean	314	180	312	175	319	177	317	180
Week 1	St.Dev	19.8	7.9	17.3	4.9	22.6	4.5	29.2	11.2
	N	10	10	10	10	10	10	10	10
Day 8	Mean	337	190	334	186	342	186	337	188
Week 2	St.Dev	23.1	12.0	17.7	6.6	22.7	7.2	28.1	8.1
	N	10	10	10	10	10	10	10	10
Mating period
Day 1	Mean	353	195	346	193	356	192	351	195
Week 1	St.Dev	29.0	12.2	19.1	7.5	24.9	6.5	30.1	7.6
	N	10	10	10	10	10	10	10	10
Day 8	Mean	365		354		365		356
Week 2	St.Dev	33.1		21.7		25.1		32.5
	N	10		10		10		10
Day 15	Mean	385		368		381		376
Week 3	St.Dev	34.2		22.1		26.9		34.7
	N	10		10		10		10

 

Table 7: Food consumption (G/Animal/Day) Males/Females

		Group 1 Control		Group 2 110 mg/kg		Group 3 330 mg/kg		Group 4 1000 mg/kg
		Males	Females	Males	Females	Males	Females	Males	Females
Pre mating
Days 1-8	Mean	23	14	23	14	23	14	22	14
Weeks 1-2	St.Dev	0.0	0.4	1.9	0.2	0.2	0.3	0.5	0.3
	N (cage)	2	2	2	2	2	2	2	2
Days 8-15	Mean	24	15	23	16	24	15	24	15
Weeks 2-3	St.Dev	0.0	0.4	1.2	0.6	0.6	0.1	0.0	1.3
	N (cage)	2	2	2	2	2	2	2	2
Mean f Means over pre mating: mean		24	15	23	15	24	14	23	15
Mating Period
Days 1-8	Mean	26	-	26		26		27
Weeks 1-2	St.Dev	0.8	-	3.2		0.9		0.3
	N (cage)	2	0	2		2		2
Days 8-15	Mean	24		23		24		25
Weeks 2-3	St.Dev	0.3		1.3		1.2		0.4
	N (cage)	2		2		2		2
Mean of means over mating period: mean		25		25		25		26

 

 

Conclusions:

Based on the results obtained from a combined 28-day repeated dose study with the reproduction/developmental toxicity screening test conducted according to OECD 422, a NOAEL of 1000 mg/kg/day was determined.

Executive summary:

In a combined 28-day repeated dose study with the reproduction/developmental toxicity screening test conducted according to OECD 422, magnesium hydroxide (99.9% purity) was administered by daily oral gavage to male and female Wistar Han rats at dose levels of 0, 110, 330 and 1000 mg/kg bw/day. Males were exposed for 2 weeks prior to mating, during mating, and up to termination (for 29 days). The females were exposed for 2 weeks prior to mating, during mating, during post-coitum, and at least 4 days of lactation (for 41- 45 days).

Formulation analysis showed that the formulations were prepared accurately and homogenously.

A number of clinical biochemistry and urinary changes were noted at 330 and 1000 mg/kg bw in males which included lower total protein, albumin and calcium levels in blood, and lower sodium and potassium excretion and higher calcium concentration in urine. Means of these changes only just exceeded or remained within the range considered normal for rats of this age and strain. Moreover, there were no histopathological correlates in eg. liver or kidneys that would support these changes. Therefore, these changes were considered not to be of toxicological

relevance.

Overall, no toxicologically relevant changes were noted in any of the parental parameters investigated in this study (i.e. clinical appearance, functional observations, body weight, food consumption, clinical laboratory investigations, macroscopic examination, organ weights, and microscopic examination).

Based on these results, the NOAEL is considered to be 1000 mg/kg/day, the highest dose administered in this study.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

772 mg/kg bw/day

Study duration:

subchronic

Species:

mouse

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

A combined repeated dose reproductive toxicity screening study (OECD 422) study was performed with magnesium hydroxide to assess the sub-acute oral toxicity in rats. No test substance related effects were observed at the highest dose tested which was equal to the limit dose for the repeated dose toxicity test of 1000 mg/kg bw.

No data is availableto assess the sub-chronic toxicity of the target substance. Therefore, available data from a sub-chronic repeated dose toxicity study conducted with a suitable read-across partner was used in a weight-of-evidence approach to assess the specific target organ toxicity of the target substance.

In a 13-week sub-chronic toxicity study similar to OECD 408, magnesium chloride hexahydrate was administered by feed to male and female to groups of 10 male and 10 female B6C3F mice at dietary levels of 0 (control), 0.3, 0.6, 1.25, 2.5 and 5% for 13 weeks.

In both sexes of the 5% treatment group a decrease in body weight was observed. While clinical signs and hematological or blood biochemistry parameters showed no treatment-related effects, histopathologically, vacuolation of kidney tubular cells was apparent in males of the 2.5 and 5% concentration groups.  

Significant increases in the relative weights of some organs were observed in both sexes of the 2.5 and 5% groups, but no blood biochemical or histopathological changes were found. Significant decrease of the relative spleen weight was apparent in the male 2.5 and 5% groups. However, since no hematological or histopathological alterations were seen these organ weight changes were considered to be simply related to the lower body weight.

Based on these results, a No Observed Adverse Effect Level (NOAEL) of 2.5% (equals to 6810 mg/kg body weight/day) for female and 1.25% (equals to 2690 mg/kg body weight/day) for male was determined, based on the reduced body weight and the vacuolation of kidney tubular cells, which is equal to 1954 mg/kg bw/day and 772 mg/kg bw/day magnesium hydroxide.

Further results were derived from a repeated dose toxicity study conducted with rats, which showed slight toxicity of magnesium chloride hexahydrate. In this study, conducted similar to OECD guideline 408, 10 male and female Wistar rats were treated with magnesium chloride hexahydrate at doses of 0.1, 0.5, and 2.5% for 90 days. In the 2.5% group, soft stool, decreased body weight gain in males and increased water intake was observed. Among females, rats in the 2.5% group showed a decrease in actual and relative weight of the liver. The soft stool disappeared during the treatment period. No treatment-related death was observed during the study. Based on the results of this study, a NOAEL of 299 mg/kg bw/day for females and 308 mg/kg bw/day.

Based on the low toxicity determined in these tests, no further testing for toxicity to other routes is proposed and due to the absence of any relevant local effects the oral studies can be used as a basis for the DNEL derivation for the dermal and inhalation routes as well.

Justification for classification or non-classification

Based on the available data, magnesium hydroxide does not warrant classification for specific target organ toxicity in accordance with CLP Regulation 1272/2008.