Magnesium

Carcinogenicity

Description of key information

There are conclusive but not suffcient data for the classification of substance Magnesium with regard to carcinogenicity

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records

Reference

Endpoint:

carcinogenicity: oral

Type of information:

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

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

In the current study, magnesium was administered in the form of magnesium chloride, the chloride ion being ubiquitious component of mammalian mineral supply via the diet, omnipresent in body fluids and involved in osmoregulation, and therefore of limited toxicologically relevance at the tested doses. The objective of the study was the evaluation of any effects of magnesium

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)

Deviations:

yes

Remarks:

Only two dose levels

Principles of method if other than guideline:

The study examined the potential carcinogenicity of MgCl2*6 H2O in B6C3F1 mice. Groups of 50 male and 50 female B6C3F1 mice were given magnesium chloride (MgCl2*6H2O) at dose levels of 0 (control), 0.5 and 2 % in the diet for 96 weeks, after which all animals received the control diet for 8 weeks and were then necropsied.

GLP compliance:

not specified

Species:

mouse

Strain:

B6C3F1

Sex:

male/female

Details on test animals or test system and environmental conditions:

Mice, 6 weeks age, were obtained from Charles River Japan Inc, Kanagawa, Japan
Mice were housed in plastic cages (five animals/cage) containlng bedding of wood chips (Beta Chip Bedding, Northeastern Products Co, NY, USA).
The cages were housed in an environmentally controlled room maintained at a temperature of 20 (+/-2)°C, a relative humidity of 55 (+/-10)% and a 12-hr light/dark cycle
The animals were kept under optimal hygien conditions and were moved twice each week to allow cleaning of the cages and a change of bedding.
Prior to the study, the animals received a commercial diet ad lib.

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on exposure:

Magnesium chloride hexahydrate was mixed with the commercial powdered diet at the appropriate concentrations.

Analytical verification of doses or concentrations:

not specified

Details on analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

96 weeks

Frequency of treatment:

Daily

Post exposure period:

8 weeks

Remarks:

Doses / Concentrations:
0.5% test substance
Basis:
nominal in diet

Remarks:

Doses / Concentrations:
2% test substance
Basis:
nominal in diet

No. of animals per sex per dose:

50 females and 50 males per dose

Control animals:

yes

Details on study design:

- After 96 weeks of test compound feeding, all aimals received the control diet for further 8 weeks.
- The dietary levels of MgCl2 were selected on the basis of results from a preliminary investigation of the effects of MgCl2 x 6H2O at dose levels of 0, 0.3, 0.6, 1.25, 2.5 and 5% in the diet to male and female mice for up to 13 weeks.

Positive control:

no data

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: No data

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: all animals were observed daily for clinical signs.

BODY WEIGHT: Yes
- Time schedule for examinations: mice were weighed weekly for the first 14 weeks and then every other week.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- Time schedule for examinations: food consumption were measured over the 2-day period before each weighing.

FOOD EFFICIENCY: No data

WATER CONSUMPTION: Yes
- Time schedule for examinations: water consumption were measured over the 2-day period before each weighing.

OPHTHALMOSCOPIC EXAMINATION: No
HAEMATOLOGY: Yes
- How many animals: 10 mice/sex/group.
- Parameters checked: haemoglobin concentration, haematocrit, erythrocyte, leukocyte and platelet counts; red blood cell indices of mean corpuscular haemoglobin concentration were calculated; differential leukocyte counts and an estimate of the percentage of nucleated red blood cells, anisocytosis and polychromasia were calculated.

CLINICAL CHEMISTRY: Yes
- How many animals: 10 mice/sex/group.
- Parameters checked: glutamic-pyruvic transaminase, glutamic-oxaloacetic transaminase, alkaline phosphatase, total cholesterol, total protein albumin-globulin ratio and urea nitrogen in serum.

URINALYSIS: Yes
- Time schedule for collection of urine: during week 104 of the study.
- Fresh urine samples were obtained.
- How many animals: 10 mice/sex/group.
- Parameters checked: pH, protein, glucose, ketones, bilirubin, occult blood, urobilinogen and specific gravity.

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

Gross and microscopic examinations were performed on all mice found dead or killed if moribund or at the end of the study.

PATHOLOGY
- The following organs were removed from animals necropsied at the end of the study: liver, kidneys, brain, heart and testes or ovaries.
- The organs were weighed and organ-to-body weight ratios were calculated.

HISTOPATHOLOGY
- Organs and tissues were preserved in 10% phosphate-buffered formaline and stained with haematoxylin and eosin.
- Organs examined: liver, kidneys, brain, heart and testes or ovaries, salivary glands, trachea, lungs, thymus, lymph nodes, stomach, small intestine, large intestine, pancreas, urinary bladder, pituitary, thyroids, adrenals, prostate, seminal vesicles, eyes, Harderian glands, spinal cord, sciatic nerve and any macroscopic pathological lesions.

Other examinations:

No data

Statistics:

Data were analysed where appropriate using the F- and Student's t-tests. The significance of differences in the incidences of non-neoplastic or neoplastic lesions between the different groups was evaluated by chi-square or Fisher's exact probability tests. Differences at p<0.05 were considered significant.

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not specified

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

not specified

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

not specified

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

effects observed, treatment-related

Details on results:

CLINICAL SIGNS AND MORTALITY:
- No abnormal clinical signs were observed in any of the treated mice throughout the test period.
- Survival rate were not affected; at week 104, survival rates of females fed 0, 0.5 and 2% magnesium chloride were 66, 72 and 72%, respectively.

BODY WEIGHT AND WEIGHT GAIN:
- Mean body weight of females given a diet containing 2% were significantly decreased from week 8 until the end of the study.
- Male body weights were comparable among groups.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Average food consumption of female mice given 2% magnesium chloride in the diet was greater than that for male mice given the same dose.
- Average compound intakes were 0.57 or 2.81 g/kg bw/d in males and 0.73 or 3.93 g/kg bw/d in females of the 0.5 and 2.0% groups, respectively.

HAEMATOLOGY/CLINICAL CHEMISTRY/URINALYSIS:
- No treatment-related changes were noted.

ORGAN WEIGHTS:
- In high-dose females (2% in the diet), significant increased absolute and relative brain weights and relative heart and kidney weights were observed.
- In the same group, a significant decrease was noted in the absolute liver weights. HISTOPATHOLOGY: NON-NEOPLASTIC:
- No treatment-related changes were noted.

HISTOPATHOLOGY: NEOPLASTIC (if applicable):
- The only tumour that showed an increased incidence, although not strictly in a dose-related manner, was malignant lymphoma/leukaemia in females and to a lesser extent in males. The incidences were within the range seen in previous studies conducted in the laboratory.
- In males, a dose-related decrease in the incidence of hepatocellular carcinoma was observed (significantly (p<0.05) at 2% in the diet).
- A decrease in the incidence of hyperplastic nodules in the liver was also noted in males of both treated groups.
- Two cases of bone osteosarcomas were noted in females of the high-dose groups, and sarcomas of the uterus were observed in both the control and treated groups; these tumours sometimes metastasised to the lung, liver and a number of other organs.

No further details are given.

Relevance of carcinogenic effects / potential:

There was no evidence of compound-related carcinogenicity.MgCl2 * 6 H2O had no carcinogenic potential in B6C3F1 mice of both sexes.
This finding can be used for read-across to magnesium.
With the exception of a significant decrease in the incidence of liver tumours among males of the high-dose group, no difference was noted in the tumour incidence between the treated and control animals.

Dose descriptor:

NOAEL

Effect level:

2 810 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male

Basis for effect level:

other: No evidence of a carcinogenic potential was seen in male and female mice fed dose levels up to 2810 and 3930 mg/kg bw/d magnesium chloride, respectively, equivalent to 336 and 470 mg Mg/kg bw/d for males and females.

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

Dose descriptor:

NOAEL

Effect level:

3 930 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

female

Basis for effect level:

other: No evidence of a carcinogenic potential was seen in male and female mice fed dose levels up to 2810 and 3930 mg/kg bw/d magnesium chloride, respectively, equivalent to 336 and 470 mg Mg/kg bw/d for males and females.

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

Dose descriptor:

NOAEL

Effect level:

336 mg/kg bw/day (actual dose received)

Based on:

element

Remarks:

Magnesium

Sex:

male

Basis for effect level:

other: No evidence of a carcinogenic potential was seen in male and female mice fed dose levels up to 2810 and 3930 mg/kg bw/d magnesium chloride, respectively, equivalent to 336 and 470 mg Mg/kg bw/d for males and females.

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

Dose descriptor:

NOAEL

Effect level:

470 mg/kg bw/day (actual dose received)

Based on:

element

Remarks:

Magnesium

Sex:

female

Basis for effect level:

other: No evidence of a carcinogenic potential was seen in male and female mice fed dose levels up to 2810 and 3930 mg/kg bw/d magnesium chloride, respectively, equivalent to 336 and 470 mg Mg/kg bw/d for males and females.

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

The highest incidence of non-neoplastic lesions was observed for cystic endometrial hyperplasla, which occurred in about 59, 38 and 34% of female in the control and low- and high-dose groups, respectively. Other lesions seen in mice of both sexes occurred in the lymph nodes, spleen, thyroid, lung, forestomach, kidney and ovary. However, the development of biologically significant lesions attributable to the treatment was not observed.

The only tumour that showed an increased incidence, although not strictly in a dose-related manner, was a malignant lymphoma/leukaemla in females and to a lesser extent in males. In male mice, a dose-related decrease in the incidence of hepatocellular carcinoma was observed. A decrease in the incidence of hyperplastlc (neoplastic) nodules in the liver was also noted in males of treated groups but the differences from the control value were not significant.

Two cases of bone osteosarcomas were noted in females of the high-dose group, and sarcomas of the uterus were observed in both control and treated groups. These tumours sometimes metastasized to the lung, liver and a number of other organs.

The mean body weights of females, but not males, fed with diets containing 2% MgCl2 6H20, were lower than those of the control females from wk 8 until the end of the study (wk 104). In the same treatment group, significant decreases and increases in the absolute weights and in the relative weights of some organs were seen. These changes seem to be related to the decrease in body weight. The average food and total test material intake values of females in the high-dose group were higher than those of males given the same dose. The reason for this discrepancy between intake and body weights is unclear. However, no significant treatment related pathological or toxicological changes were observed in any organs in females of the high-dose group. Therefore, this change was considered not to be of biological significance and lay within the range expected for this parameter.

Conclusions:

Under the condition of this test, for a period of 96 weeks, the NOAEL for female and male mice was, respectively 3,930 mg/kgbw/day (2% in feed) and 2,810 mg/kgbw/day (2% in feed),respectively, equivalent to 470 and 336 mg Mg/kg bw/d for f males and males.

Executive summary:

Groups of 50 male and 50 female B6C3F1 mice were given MgCl2, 6H20 at dose levels of 0 (control), 0 5 and 2% in the diet for 96 wk, after which all animals received the control diet for 8 wk and were then necropsied. In females of the high-dose group, a decrease in body weight was observed. However, survival rates did not differ between the treatment and control groups for males or females and clinical signs and urinary, haematological or serum clinical chemistry parameters showed no treatment-related effects. Therefore, this change was considered not to be of biological significance.

On histological examination, tumours were mainly found in the skin/subcutis, liver and lymphatic system. However, with the exception of a significant decrease in the incidence of liver tumours among males of the high-dose group, no differences were noted in the tumour incidence between the treated and control animals Thus, the study described here clearly shows a lack of carcinogenicity of MgCl2, 6H20 given to B6C3F1 mice in the diet.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

336 mg/kg bw/day

Study duration:

chronic

Species:

mouse

Carcinogenicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

carcinogenicity: inhalation

Type of information:

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

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study well documented, meets generally accepted scientific principles, acceptable for assessment.

Qualifier:

no guideline followed

Principles of method if other than guideline:

One year inhalation exposure of rats (6 hours/day, 5 days/week) followed by a 1 year clearance period.
The test methodology was designed to maximise the amount of asbestos like 'whiskers' in the test atmosphere which is inhaled by the test animals. Two test substances were used with different 'whisker' lengths in order to better obtain the potential for damage to the lungs.
There was a large variation in the test concentrations for the short and large 'whisker' substance types. This deficiency in test methodology was considered not to affect the reliability of the study result.

GLP compliance:

not specified

Species:

rat

Strain:

Wistar

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Not reported.
- Age at study initiation: 4 weeks old.
- Weight at study initiation: Not reported.
- Housing: Not reported.
- Diet (e.g. ad libitum): Not reported.
- Water (e.g. ad libitum): Not reported.
- Acclimation period: Not reported.

ENVIRONMENTAL CONDITIONS
Not reported.

Route of administration:

inhalation

Type of inhalation exposure (if applicable):

whole body

Vehicle:

air

Details on exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: consisted of a whisker generator and an exposure chamber (volume 0.43m^3) made from stainless steel.
- System of generating particulates/aerosols: whiskers were premixed with glass beads (250µm) and put into a hopper. The whiskers mixed with glass beads were supplied from the hopper to a fluidised bed generator. Air from a compressor was passed through a silica gel fixed bed and introduced into the bottom of the fluidised bed. Glass beads with whiskers were moved in the fluidised bed due to airflow and the whiskers were detached from the glass beads.
- Temperature, humidity in air chamber: 25°C, 50%
- Air flow rate: air with whiskers was introduced from the top of the chamber with a flow rate of 150 L/minute.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The whisker concentration in the chamber was monitored continuously with a digital dust indicator.

Duration of treatment / exposure:

Subchronic exposure: 4 weeks
Chronic exposure: 1 year

Frequency of treatment:

6 hours/day 5 days/week

Post exposure period:

1 year

Remarks:

Doses / Concentrations:
2.3 mg/m3 (short whiskers)
Basis:
nominal conc.

Remarks:

Doses / Concentrations:
4.0 mg/m3 (long whiskers)
Basis:
nominal conc.

No. of animals per sex per dose:

80 rats were divided into 3 groups: 27, 27 and 26 rats per group for short whiskers, long whiskers and controls, respectively

Control animals:

yes

Details on study design:

Rats were randomly divided

Positive control:

no data

Observations and examinations performed and frequency:

Body weights of the rats were measured every week to obtain the growth curves.

Sacrifice and pathology:

In the subchronic exposure five or six rats in each group were killed and dissected at one, two, three and four weeks after the beginning of the exposure, and two weeks, four weeks, six months and one year after the end of exposure. In all dissections, the weights of body and organs (lung, liver, kidney and spleen) were measured. Lungs were divided and part was used for the analysis of the whiskers (wet ashing method). The remaining portions were used for the histopathological examination.

Other examinations:

no

Statistics:

no data

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

not specified

Food efficiency:

not specified

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

not specified

Ophthalmological findings:

not examined

Haematological findings:

not specified

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

not specified

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

effects observed, treatment-related

Details on results:

CLINICAL SIGNS AND MORTALITY:
- Survival rates were no affected by inhaltion exposure.
- 48% (10/21), 41% (9/22) and 30% (6/20) of rats died within 1 year after end of exposure in the controls, the short whisker, and long whisker groups, respectively.

BODY WEIGHT AND WEIGHT GAIN:
- Growth curves were similar in all groups.

ORGAN WEIGHTS:
- Organ weights did not show significant differences.

HISTOPATHOLOGY:
- In the rats with one year clearance after chronic exposure, several non-plastic lesions were found in both experimental and control groups.
- Incidences of 2/13, 2/14 and 1/11 pulmonary adenomas were seen animals examined in the short whisker, long whisker and the control groups, respectively.
- One showed a pronounced epithelial atypia, but this was not conclusive of carcinoma.
- The number of adenomas in the exposure groups was not significantly greater than that of the control group.
- Hepatocellular adenoma (1/14) and carcinoma (1/13) occurred more often in the whisker groups than in the control group (0/11).

MAGNESIUM CONTENT OF THE LUNGS:
The magnesium content did not increase even when the exposure periods lengthened from one to four weeks. The amount of magneisum in the rats after exposure to the long whiskers for two to three weeks was significantly greater than after one week (p<0.05). It should not be considered that the average magnesium content increased but rather magnesium content in the one week exposure group was smaller than the others, because the values were not greater than those in the control group for all exposure periods. The magneisum concentrations in the short whisker group were almost identical with those in the long whisker and control groups. See table 3.

Relevance of carcinogenic effects / potential:

Relevance for RA limited: only 2 exposure groups (long and short whiskers); focused on lung toxicity in relation to physical/chemical characteristics of fibres; not designed as carcinogenicity study.

Dose descriptor:

NOAEL

Basis for effect level:

other: Any adverse effects observed in the test groups were also observed in the control groups and were considered not to be statistically significant.

Remarks on result:

not determinable

Remarks:

no NOAEL identified

Dose descriptor:

NOEC

Effect level:

2.3 mg/m³ air (nominal)

Based on:

other: digital dust indicator

Sex:

male

Basis for effect level:

other: No statistically significant effects were noted in the study at the concentration (short whiskers) tested.

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

Dose descriptor:

NOEC

Effect level:

4 mg/m³ air (nominal)

Based on:

other: digital dust indicator

Sex:

male

Basis for effect level:

other: No statistically significant effects were noted in the study at the concentration (long whiskers) tested.

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

Table 1. Weights of body and organs.

 

	n	Body weight (g(SD))	Lung (g(SD))	Liver (g(SD))	Kidneys (g(SD))	Spleen (g(SD))
1 week
Control	5	203.0 (6.0)	1.10 (0.19)	6.06 (0.23)	1.61 (0.09)	0.58 (0.04)
Short whisker	5	204.2 (4.9)	1.03 (0.12)	5.96 (0.29)	1.54 (0.05)	0.59 (0.07)
Long whisker	5	197.8 (5.7)	1.00 (0.06)	5.76 (0.44)	1.50 (0.12)	0

 

2 weeks
Control	5	255.8 (12.4)	1.15 (0.07)	7.31 (0.53)	1.65 (0.11)	0.71 (0.07)
Short whisker	5	248.2 (9.0)	1.10 (0.06)	6.89 (0.29)	1.70 (0.12)	0.78 (0.24)
Long whisker	5	247.4 (17.7)	1.11 (0.04)	7.00 (0.85)	1.65 (0.15)	0.71 (0.09)
3 weeks

 

Control	5	286.0 (14.9)	1.17 (0.08)	7.81 (0.55)	1.95 (0.12)	0.70 (0.07)
Short whisker	5	288.6 (16.1)	1.20 (0.06)	8.48 (0.66)	1.95 (0.14)	0.74 (0.08)
Long whisker	5	281.4 (19.0)	1.17 (0.06)	7.60 (0.69)	1.83 (0.08)	0.69 (0.05)
4 weeks
Control	5	323.4 (21.1)	1.22 (0.07)	8.19 (0.63)	2.01 (0.23)	0.74 (0.10)
Short whisker	5	317.6 (14.3)	1.24 (0.04)	8.36 (0.51)	1.98 (0.08)	0.79 (0.10)
Long whisker	5	309.6 (32.2)	1.19 (0.09)	7.85 (0.85)	1.94 (0.28)	0

 

4 weeks + 2 months
Control	5	365.4 (35.0)	1.26 (0.11)	9.36 (1.55)	2.20 (0.27)	0.77 (0.15)
Short whisker	5	373.2 (26.8)	1.27 (0.08)	9.09 (0.70)	2.26 (0.26)	0.81 (0.15)
Long whisker	5	382.2 (28.8)	1.34 (0.13)	9.91 (1.06)	2.29 (0.21)	0.90 (0.10)

 

4 weeks + 4 months
Control	5		414.2 (38.1)	1.49 (0.07)		10.57 (0.89)		2.33 (0.21)		0.78 (0.09)
Short whisker	5		405.8 (37.8)	1.33 (0.11)		9.73 (1.63)		2.29 (0.32)		0.82 (0.04)
Long whisker	5		398.2 (29.1)	1.37 (0.07)		9.76 (0.74)		2.28 (0.18)		0.82 (0.07)
4 weeks + 6 months
Control	-		-	-		-		-		-
Short whisker	6		599.8 (38.3)	1.64 (0.07)		13.42 (0.99)		2.63 (0.22)		0.94 (0.07)
Long whisker	6		567.2 (62.2)	1.57 (0.30)		12.37 (2.08)		2.52 (0.40)		0
4 weeks + 12 months
Control	6	626.0 (65.0)			1.73 (0.15)		12.43 (1.68)		2.92 (0.29)	0.86 (0.14)
Short whisker	6	665.0 (101.5)			1.95 (0.52)		14.13 (2.80)		3.39 (0.71)	1.00 (0.12)
Long whisker	6	678.8 (154.6)			1.96 (0.49)		13.89 (3.45)		3.23 (0.55)	0

 

Table 2. Summary of histopathological features.

 

	Short whisker	Long whisker			Control
No. of rats	6	6			6
Pulmonary lesions:
Thickening of the pleura	3	1			2
Calcification of pulmonary artery	4	3			1
Squamous metaplasia	0	1			0
Aggregate of form cells	2	2			1
Pulmonary tumour:
Adenoma			0	1		0
Squamous cell carcinoma			0	0		0
Extrapulmonary lesions:
Pancreas:
Acinic cell adenoma			0	0		1
Islet cell adenoma			0	0		0
Kidney:
Pyelonephritis			2	0		0
Infarct			0	0		0
Liver:
Hepatocellular adenoma			0	0		0
Hepatocellular carcinoma			0	0		0
Soft tissue tumour:
Fibroma			0	0		0
Sarcoma (fibrosarcoma)			0	0		0
Salivary gland adenoma			0	0		0
Pituitary adenoma			0	0		2

Table 3. Magnesium content in the lung.

Period (weeks)	Control (µg/g lung)	Long whisker (µg/g lung)	Short whisker (µg/g lung)
1	132.0 (15.6)	122.2 (8.1)	124.7 (11.8)
2	134.2 (2.3)	131.3 (1.2)†	129.9 (2.5)*
3	134.2 (2.3)	131.5 (1.4)†	133.3 (3.4)
4	132.5 (3.2)	130.0 (6.9)	134.8 (1.7)

†p<0.05 compared to one week exposure to long whiskers

*p<0.05

 

Conclusions:

A histopathological examination indicated occurence of adenoma and carcinoma a year after chronic exposure to magnesium sulphate whiskers. However, there was no significant difference between exposed rats and control rats.
No significant difference in the occurrence of adenoma and carcinoma between exposed and control groups was observed indicating that even fibrous forms of magnesium sulphate did not induce an increased tumour incidence in rats exposed up to one year. However in any case the results are of limited relevance for magnesium hydroxide as it does not exist in a fibrous form.

Executive summary:

Male Wistar rats were exposed to two types of magnesium sulphate whiskers by inhalation for six hours a day, five days a week, for four weeks (sub-chronic study), or for one year (chronic study) to clarify the biological effects of the whiskers. There were few whiskers detected in the rat lungs even at one day after the exposure, suggesting that they are dissolved and eliminated rapidly from the lungs. To measure the clearance rate of the whiskers from the lungs, an intratracheal instillation was performed in golden hamsters. The half life of the whiskers in the lung was determined as 17-6 minutes by temporally measuring the magnesium concentration up to 80 minutes after the instillation. A histopathological examination indicated a frequent occurrence of adenoma and carcinoma in the year after chronic exposure, but it was not significantly different between exposed and control rats.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEC

14.6 mg/m³

Study duration:

chronic

Species:

mouse

Carcinogenicity: via dermal route

Link to relevant study records

Reference

Endpoint:

carcinogenicity: oral

Type of information:

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

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

In the current study, magnesium was administered in the form of magnesium chloride, the chloride ion being ubiquitious component of mammalian mineral supply via the diet, omnipresent in body fluids and involved in osmoregulation, and therefore of limited toxicologically relevance at the tested doses. The objective of the study was the evaluation of any effects of magnesium

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)

Deviations:

yes

Remarks:

Only two dose levels

Principles of method if other than guideline:

The study examined the potential carcinogenicity of MgCl2*6 H2O in B6C3F1 mice. Groups of 50 male and 50 female B6C3F1 mice were given magnesium chloride (MgCl2*6H2O) at dose levels of 0 (control), 0.5 and 2 % in the diet for 96 weeks, after which all animals received the control diet for 8 weeks and were then necropsied.

GLP compliance:

not specified

Species:

mouse

Strain:

B6C3F1

Sex:

male/female

Details on test animals or test system and environmental conditions:

Mice, 6 weeks age, were obtained from Charles River Japan Inc, Kanagawa, Japan
Mice were housed in plastic cages (five animals/cage) containlng bedding of wood chips (Beta Chip Bedding, Northeastern Products Co, NY, USA).
The cages were housed in an environmentally controlled room maintained at a temperature of 20 (+/-2)°C, a relative humidity of 55 (+/-10)% and a 12-hr light/dark cycle
The animals were kept under optimal hygien conditions and were moved twice each week to allow cleaning of the cages and a change of bedding.
Prior to the study, the animals received a commercial diet ad lib.

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on exposure:

Magnesium chloride hexahydrate was mixed with the commercial powdered diet at the appropriate concentrations.

Analytical verification of doses or concentrations:

not specified

Details on analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

96 weeks

Frequency of treatment:

Daily

Post exposure period:

8 weeks

Remarks:

Doses / Concentrations:
0.5% test substance
Basis:
nominal in diet

Remarks:

Doses / Concentrations:
2% test substance
Basis:
nominal in diet

No. of animals per sex per dose:

50 females and 50 males per dose

Control animals:

yes

Details on study design:

- After 96 weeks of test compound feeding, all aimals received the control diet for further 8 weeks.
- The dietary levels of MgCl2 were selected on the basis of results from a preliminary investigation of the effects of MgCl2 x 6H2O at dose levels of 0, 0.3, 0.6, 1.25, 2.5 and 5% in the diet to male and female mice for up to 13 weeks.

Positive control:

no data

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: No data

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: all animals were observed daily for clinical signs.

BODY WEIGHT: Yes
- Time schedule for examinations: mice were weighed weekly for the first 14 weeks and then every other week.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- Time schedule for examinations: food consumption were measured over the 2-day period before each weighing.

FOOD EFFICIENCY: No data

WATER CONSUMPTION: Yes
- Time schedule for examinations: water consumption were measured over the 2-day period before each weighing.

OPHTHALMOSCOPIC EXAMINATION: No
HAEMATOLOGY: Yes
- How many animals: 10 mice/sex/group.
- Parameters checked: haemoglobin concentration, haematocrit, erythrocyte, leukocyte and platelet counts; red blood cell indices of mean corpuscular haemoglobin concentration were calculated; differential leukocyte counts and an estimate of the percentage of nucleated red blood cells, anisocytosis and polychromasia were calculated.

CLINICAL CHEMISTRY: Yes
- How many animals: 10 mice/sex/group.
- Parameters checked: glutamic-pyruvic transaminase, glutamic-oxaloacetic transaminase, alkaline phosphatase, total cholesterol, total protein albumin-globulin ratio and urea nitrogen in serum.

URINALYSIS: Yes
- Time schedule for collection of urine: during week 104 of the study.
- Fresh urine samples were obtained.
- How many animals: 10 mice/sex/group.
- Parameters checked: pH, protein, glucose, ketones, bilirubin, occult blood, urobilinogen and specific gravity.

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

Gross and microscopic examinations were performed on all mice found dead or killed if moribund or at the end of the study.

PATHOLOGY
- The following organs were removed from animals necropsied at the end of the study: liver, kidneys, brain, heart and testes or ovaries.
- The organs were weighed and organ-to-body weight ratios were calculated.

HISTOPATHOLOGY
- Organs and tissues were preserved in 10% phosphate-buffered formaline and stained with haematoxylin and eosin.
- Organs examined: liver, kidneys, brain, heart and testes or ovaries, salivary glands, trachea, lungs, thymus, lymph nodes, stomach, small intestine, large intestine, pancreas, urinary bladder, pituitary, thyroids, adrenals, prostate, seminal vesicles, eyes, Harderian glands, spinal cord, sciatic nerve and any macroscopic pathological lesions.

Other examinations:

No data

Statistics:

Data were analysed where appropriate using the F- and Student's t-tests. The significance of differences in the incidences of non-neoplastic or neoplastic lesions between the different groups was evaluated by chi-square or Fisher's exact probability tests. Differences at p<0.05 were considered significant.

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not specified

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

not specified

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

not specified

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

effects observed, treatment-related

Details on results:

CLINICAL SIGNS AND MORTALITY:
- No abnormal clinical signs were observed in any of the treated mice throughout the test period.
- Survival rate were not affected; at week 104, survival rates of females fed 0, 0.5 and 2% magnesium chloride were 66, 72 and 72%, respectively.

BODY WEIGHT AND WEIGHT GAIN:
- Mean body weight of females given a diet containing 2% were significantly decreased from week 8 until the end of the study.
- Male body weights were comparable among groups.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Average food consumption of female mice given 2% magnesium chloride in the diet was greater than that for male mice given the same dose.
- Average compound intakes were 0.57 or 2.81 g/kg bw/d in males and 0.73 or 3.93 g/kg bw/d in females of the 0.5 and 2.0% groups, respectively.

HAEMATOLOGY/CLINICAL CHEMISTRY/URINALYSIS:
- No treatment-related changes were noted.

ORGAN WEIGHTS:
- In high-dose females (2% in the diet), significant increased absolute and relative brain weights and relative heart and kidney weights were observed.
- In the same group, a significant decrease was noted in the absolute liver weights. HISTOPATHOLOGY: NON-NEOPLASTIC:
- No treatment-related changes were noted.

HISTOPATHOLOGY: NEOPLASTIC (if applicable):
- The only tumour that showed an increased incidence, although not strictly in a dose-related manner, was malignant lymphoma/leukaemia in females and to a lesser extent in males. The incidences were within the range seen in previous studies conducted in the laboratory.
- In males, a dose-related decrease in the incidence of hepatocellular carcinoma was observed (significantly (p<0.05) at 2% in the diet).
- A decrease in the incidence of hyperplastic nodules in the liver was also noted in males of both treated groups.
- Two cases of bone osteosarcomas were noted in females of the high-dose groups, and sarcomas of the uterus were observed in both the control and treated groups; these tumours sometimes metastasised to the lung, liver and a number of other organs.

No further details are given.

Relevance of carcinogenic effects / potential:

There was no evidence of compound-related carcinogenicity.MgCl2 * 6 H2O had no carcinogenic potential in B6C3F1 mice of both sexes.
This finding can be used for read-across to magnesium.
With the exception of a significant decrease in the incidence of liver tumours among males of the high-dose group, no difference was noted in the tumour incidence between the treated and control animals.

Dose descriptor:

NOAEL

Effect level:

2 810 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male

Basis for effect level:

other: No evidence of a carcinogenic potential was seen in male and female mice fed dose levels up to 2810 and 3930 mg/kg bw/d magnesium chloride, respectively, equivalent to 336 and 470 mg Mg/kg bw/d for males and females.

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

Dose descriptor:

NOAEL

Effect level:

3 930 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

female

Basis for effect level:

other: No evidence of a carcinogenic potential was seen in male and female mice fed dose levels up to 2810 and 3930 mg/kg bw/d magnesium chloride, respectively, equivalent to 336 and 470 mg Mg/kg bw/d for males and females.

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

Dose descriptor:

NOAEL

Effect level:

336 mg/kg bw/day (actual dose received)

Based on:

element

Remarks:

Magnesium

Sex:

male

Basis for effect level:

other: No evidence of a carcinogenic potential was seen in male and female mice fed dose levels up to 2810 and 3930 mg/kg bw/d magnesium chloride, respectively, equivalent to 336 and 470 mg Mg/kg bw/d for males and females.

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

Dose descriptor:

NOAEL

Effect level:

470 mg/kg bw/day (actual dose received)

Based on:

element

Remarks:

Magnesium

Sex:

female

Basis for effect level:

other: No evidence of a carcinogenic potential was seen in male and female mice fed dose levels up to 2810 and 3930 mg/kg bw/d magnesium chloride, respectively, equivalent to 336 and 470 mg Mg/kg bw/d for males and females.

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

The highest incidence of non-neoplastic lesions was observed for cystic endometrial hyperplasla, which occurred in about 59, 38 and 34% of female in the control and low- and high-dose groups, respectively. Other lesions seen in mice of both sexes occurred in the lymph nodes, spleen, thyroid, lung, forestomach, kidney and ovary. However, the development of biologically significant lesions attributable to the treatment was not observed.

The only tumour that showed an increased incidence, although not strictly in a dose-related manner, was a malignant lymphoma/leukaemla in females and to a lesser extent in males. In male mice, a dose-related decrease in the incidence of hepatocellular carcinoma was observed. A decrease in the incidence of hyperplastlc (neoplastic) nodules in the liver was also noted in males of treated groups but the differences from the control value were not significant.

Two cases of bone osteosarcomas were noted in females of the high-dose group, and sarcomas of the uterus were observed in both control and treated groups. These tumours sometimes metastasized to the lung, liver and a number of other organs.

The mean body weights of females, but not males, fed with diets containing 2% MgCl2 6H20, were lower than those of the control females from wk 8 until the end of the study (wk 104). In the same treatment group, significant decreases and increases in the absolute weights and in the relative weights of some organs were seen. These changes seem to be related to the decrease in body weight. The average food and total test material intake values of females in the high-dose group were higher than those of males given the same dose. The reason for this discrepancy between intake and body weights is unclear. However, no significant treatment related pathological or toxicological changes were observed in any organs in females of the high-dose group. Therefore, this change was considered not to be of biological significance and lay within the range expected for this parameter.

Conclusions:

Under the condition of this test, for a period of 96 weeks, the NOAEL for female and male mice was, respectively 3,930 mg/kgbw/day (2% in feed) and 2,810 mg/kgbw/day (2% in feed),respectively, equivalent to 470 and 336 mg Mg/kg bw/d for f males and males.

Executive summary:

Groups of 50 male and 50 female B6C3F1 mice were given MgCl2, 6H20 at dose levels of 0 (control), 0 5 and 2% in the diet for 96 wk, after which all animals received the control diet for 8 wk and were then necropsied. In females of the high-dose group, a decrease in body weight was observed. However, survival rates did not differ between the treatment and control groups for males or females and clinical signs and urinary, haematological or serum clinical chemistry parameters showed no treatment-related effects. Therefore, this change was considered not to be of biological significance.

On histological examination, tumours were mainly found in the skin/subcutis, liver and lymphatic system. However, with the exception of a significant decrease in the incidence of liver tumours among males of the high-dose group, no differences were noted in the tumour incidence between the treated and control animals Thus, the study described here clearly shows a lack of carcinogenicity of MgCl2, 6H20 given to B6C3F1 mice in the diet.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

2.7 mg/kg bw/day

Study duration:

chronic

Species:

mouse

Justification for classification or non-classification

Based on the hazard assessmentof Magnesium in section 2.1 and 2.2.in IUCLID 5.4., available data for the substance and following the “Guidance on Information Requirement and Chemical Safety Assessment R.8. Characterisation of dose [concentration]- response for human health”, according to the EU’s list of dangerous substances (OJEC No L200/130.7.99)

and according to the criteria described in Directive 67/548 and in the CLP Regulation:

 

 

Directive 67/548	Carcinogenicity Carc. Cat. 1; R45 May cause cancer. Carc. Cat. 1; R49 May cause cancer by inhalation. Carc. Cat. 2; R45 May cause cancer. Carc. Cat. 2; R49 May cause cancer by inhalation. Carc. Cat. 3; R40 Limited evidence of a carcinogenic effect.
CLP	Carcinogenicity Carc. 1A Carc. 1B Carc. 2 H350: May cause cancer <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>. H351: Suspected of causing cancer <state route of exposure if it is conclusively proven that no other routs of exposure cause the hazard>.

 

It is concluded that the substance Magnesium does not meet the criteria to be classified for human health hazards for Carcinogenicity.

 

Additional information

Oral effects:

Under the condition of the testIn a reliable studyof Kurata, Y.; et al.,1989, for a period of 96 weeks,.No evidence of a carcinogenic potential was seen in male and female mice fed dose levels up to 2810 and 3930 mg/kg bw/d magnesium chloride, respectively, equivalent to 336 and 470 mg Mg/kg bw/d for males and females.

Inhalation effects:

The oral dose for the rat is converted to the corresponding air concentration using a standard breathing volume for the rat (1.15m3/kg for 24 hours exposure. The resulting air concentration needs to be additionally corrected for 24 hlight activity (20 m³), assuming 100 % absorption for both routes.

NOAEL mice              336 mg/kg bw/day

÷1.15m3/kgbw

÷20m3/mice

NOAECmice     14.6 mg/m3

Dermal Effects:

For dermal exposure we taken that:

-the average weight of mice is 80 g (60 -100 g),

-the dose is applied over an area which is approximately 10% of the total body surface=0.008 kg

 

corrected dermal NOAEL=    oral NOAEL

                                   336 mg/kg bw/dx 0.008 kg =                   

 NOAECrat      2.7 mg/kg bw/day

 

Justification for selection of carcinogenicity via inhalation route endpoint:
The dose descriptor for dermal irritation/corrosion come from dermal acute study and dermal Repeated toxicity study. In these studies, the dose is reported in the unit mg/kg of body weight/day. This needs to be modified to enable comparison with the human exposure, generally expressed in mg/cm2/day.
We have taken that:
• the average weight of rats is 230g (210 -251.5g), used by SIAM 32, 19/04/2011
• the dose is applied over an area which is approximately 10% of the total body surface, and
• the total body surface of rats is on the average 376 cm2 used by SIAM 32, 19/04/2011

The generic modification from the dose in mg/kg bw to NOAECmodified(in mg/cm2/day) will be
 
NOAEC in mg/cm2 =        ((average animal weight in kg) x (dose in mg/kg bw)) / Treated surface in cm2)
 
NOAEC in mg/cm2 =       (0.23 x 2000)/36.7 =12.5 mg/cm2

 -The dose was 2000 mg/kg bw in the acute study of SIAM 32, 19/04/2011
- average animal weight in kg was 0.23 kg
- Treated surface in cm2 was 36.7 cm2
 
NOAEC in mg/cm2 =       (0.23 x 2000)/36.7 =12.5 mg/cm2

Justification for selection of carcinogenicity via dermal route endpoint:
Dermal Effects:
For dermal exposure we taken that:
-the average weight of mice is 80 g (60 -100 g),
-the dose is applied over an area which is approximately 10% of the total body surface=0.008 kg
 
corrected dermal NOAEL=    oral NOAEL
                                   336 mg/kg bw/dx 0.008 kg =                   
 NOAECrat      2.7 mg/kg bw/day
 

Carcinogenicity: via oral route (target organ): other: all gross lesions and masses

Carcinogenicity: via inhalation route (target organ): respiratory: lung; other: all gross lesions and masses

Carcinogenicity: via dermal route (target organ): other: skin