Reaction mass of Magnesium peroxide and magnesium carbonate and magnesium hydroxide and magnesium oxide

Endpoint summary

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study is in compliance with OECD 401 and was carried out under GLP conditions.

Qualifier:

according to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

GLP compliance:

yes

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

other: Crl:CD BR

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Raleigh, North Carolina
- Age at study initiation: male rats were 56-62 days old, female rats were 63-66 days old
- Weight at study initiation: males weighed between 222 and 242 g, females weighed between 191 and 194 g
- Fasting period before study: approximately 18 hours
- Housing: Singly in suspended, stainless steel, wire-mash cages
- Diet (e.g. ad libitum): Purina certified Rodent Chow, #5002 ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: approximately 1 week

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 23 +/- 1 °C
- Humidity (%): 50 +/- 10 %
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

see Table 1

Doses:

nominal doses were 500, 1000 and 1500 mg/kg body weight in males and 500, 750 and 1000 mg/kg body weight in females

No. of animals per sex per dose:

5

Control animals:

no

Details on study design:

Animals were observed for 14 days after the administration of the single dose of hydrogen peroxide. All rats on study were examined grossly at necropsy either when found dead or sacrificed by design after cessation of the observation period. All animals were checked daily for mortality and clinical signs.

Statistics:

Method of determination of LD50: Finney, D.J. (Probit analysis, 3rd. Ed., Cambridge University Press, 1971)

Preliminary study:

none

Sex:

male

Dose descriptor:

LD50

Effect level:

1 026 mg/kg bw

Sex:

female

Dose descriptor:

LD50

Effect level:

693.7 mg/kg bw

95% CL:

427 - 960

Mortality:

2 males in the 1000 mg/kg dose group and 5 males in the 1500 mg/kg dose group were found dead before the end of the observation period.
1 female in the 500 mg/kg dose group, 2 females in the 750 mg/kg dose group and 5 females in the 1000 mg/kg dose group were found dead before the end of the observation period.

Clinical signs:

other: Clinical signs of toxicity were observed in all dose groups, and included lethargy, immobility, irregular respiration, and hunced posture. Other clinical signs were low posture, low carriage, red ocular discharge and ruffled fur.

Gross pathology:

Gross findings included discoloration of the tongue, fluid in the esophagus, thickened and discolorated stomach with observed fluid, ulcer/erosion of the stomach, discoloration of the duodenum and fluid formation in the tissue, fluid in the peritoneal cavity and adhesion of stomach, liver and spleen.

Other findings:

Microscopic findings: degenerative (ulcer) and regenerative (hyperplasia) alterations in the mucosa and/or submucosa of the plyoric antrum of the stomach were present in males at 500 (2/5), 1000 (2/5) and 1500 (1/5) mg/kg levels and in females at the 500 (3/5) and 750 (3/5) mg/kg levels. Ulcerswere focal areas of necrosis of the epithelium, lamina propria and muscularis mucosa. Inflammation was not diagnosed accompanying an ulcer, as it was considered a component of the ulcer diagnosis. Pyloric mucosal hyperplasia was characterised by increased gland height and goblet cells full of mucus and was most often seen near ulcers. In other instances, mucosal hyperplasia was accompanied by inflammation and these changes togehter were considered indicative of irritation that had not progressed to ulceration. Small to large irregularly round to oval clear spaces were detected in the mucosa, submucosa and tunica muscularis of the stomachs of all rats found dead on test day 1. The spaces were interpreted to be accumulations of gas, probably oxygen.
The stomach lesions noted in rats sacrificed by design were considered morphologically reparable upon cessation of treatment with hydrgen peroxide, although scar tissue might focally replace the muscularis mucosa at sites of ulceration.

Table 1: Results of the acute oral toxicity test in male and female rats

Dose [mg/kg bw]	Number of dead		Dose volume (mL/kg)
	male	female	male	female
500	0/5	1/5	0.39	0.39
750	-	2/5	-	0.58
1000	2/5	5/5-	0.78	0.78
1500	5/5		1.16	-
LD50 value	1026 mg/kg bw	694 mg/kg bw	Combined LD50: 805 mg/kg bw

Interpretation of results:

Category 4 based on GHS criteria

Remarks:

Migrated information

Conclusions:

70% hydrogen peroxide is classified as harmful if swallowed (R22; Xn) according to Directive 2001/59/EC (adaptation of 67/548/EEC) and is classified with acute toxicity category 4 according to Regulation (EC) No 1272/2008.

Executive summary:

The acute oral toxicity of hydrogen peroxide (70 % w/w in aqueous solution) was tested in male and female Crl:CD BR rats receiving 500, 750, 1000, or 1500 mg/kg body weight by oral gavage in compliance with OECD Guideline No. 401. Animals were observed for 14 days and then sacrificed. All animals were subjected to gross necropsy. Additionally, microscopic tissue examinations were performed. Mortality occurred in 2 males receiving 1000 mg/kg, 1 female receiving 500 mg/kg and 2 females receiving 750 mg/kg and in all males and females receiving 1500 mg/kg and most animals were found dead on the day of administration. Compound-related gross changes of the tongue, oesophagus, stomach and duodenum and adhesions in the peritoneal cavity were noted in male and female rats found dead. At all dose levels degenerative ulceration and regenerative hyperplasia of the pyloric antrum of the stomach were found. The ulcerative necrosis penetrated into the gastric epithelium (muscularis mucosa): the severity of the ulcerations was rated minimal to mild.

The LD50 value was 1026 (not confidence interval available) mg/kg for male rats and 693.7 (427 to 960) mg/kg for female rats, respectively.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study was carried out in compliance with GLP and US-EPA Vol 50 (§798.1150) Guideline, which is equivalent to OECD Guideline No. 403.

Qualifier:

according to guideline

Guideline:

other: US-EPA Vol 50 (§798.1150)

GLP compliance:

yes

Test type:

standard acute method

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Inc. Raleigh, North Carolina
- Age at study initiation: 8-9 weeks;
- Weight at study initiation: males: 262 - 277 g; females 217 – 257 g
- Fasting period before study:
- Housing: Doubly in suspended, stainless steel, wire mash cages during acclimation and non-exposure period; individually in 100 litre Plexiglass exposure chambers during exposure
- Diet (e.g. ad libitum): Purina Rodent Laboratory Chow Brand Animal Diet #5001 ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: All animals were acclimated for 11 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-25 °C; 25 °C (during exposure)
- Humidity (%): 17-60 % (40-44 % during exposure)
- Air changes (per hr): No data
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

inhalation

Type of inhalation exposure:

whole body

Vehicle:

other: no data

Details on inhalation exposure:

The atmosphere was generated by bubbling air flow through a reservoir containing 1000 ml of 50% hydrogen peroxide. Particle size distribution measurements showed a particulate level of 0.020 mg/m3, which was comparable to background air levels thus indicating no appreciable aerosol formation.

Analytical verification of test atmosphere concentrations:

yes

Remarks:

Samples for colorimetric determination of vapours of hydrogen peroxide (50 %) were withdrawn once per hour

Duration of exposure:

4 h

Concentrations:

Nominal concentration: 7.7 [mg/L]
Analytical concentration: 0.17 [mg/L] (maximum attainable vapour)

No. of animals per sex per dose:

5 rats

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Necropsy of survivors performed: yes/no
- Other examinations performed: clinical signs, body weight,organ weights, histopathology

Statistics:

no data

Preliminary study:

none

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 170 mg/m³ air

Exp. duration:

4 h

Mortality:

No deaths occurred.

Clinical signs:

other: Observations noted during exposure included decreased activity and eye closure. Signs exhibited by animals upon removal from the chamber and during the two-hour post-exposure observation period on Day 1 included nasal discharge, excessive salivation and a

Body weight:

Body weight at day 2 was slightly less than pre-test value. Recovery of weight occurred thereafter and all animals were in excess of their pre-exposure body weight by termination of the study.

Gross pathology:

No effects considered treatment-related were found. Lung weights were comparable to historical values

Other findings:

no other findings

none

Interpretation of results:

not classified

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

Classification according to Directive 2001/59/EC (adaptation of 67/548/EEC) is not necessary since at the maximum technical attainable vapour concentration of 0.17 mg/L no deaths occurred.

Executive summary:

The acute inhalation toxicity of hydrogen peroxide (50 %) aerosols was tested in male and female Sprague-Dawley rats according to US EPA Guideline Vol 50 (§798.1150). Animals received a single 4 -hour whole-body exposure to the maximum attainable aerosol concentration of 170 mg/m³. All tested animals survived the exposure and subsequent 14 -day post-exposure observation period. Signs of treatment were minimal during the exposure but a few responses such as nasal discharge were noted during the whole 14 -day observation period. A minimal, transient adverse effect upon body weight was produced by treatment. Otherwise, body weight gain was considered unremarkable. Gross post mortem observations and lung weights were considered unremarkable. No LD₅₀ value for acute inhalation toxicity could be established and the LD₅₀ value must be greater than the attainable aerosol concentration of hydrogen peroxide of 170 mg/m³.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Acute toxicity: via dermal route

Link to relevant study records

Reference

Endpoint:

acute toxicity: dermal

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

Read CSR in Section 13 for RA justification

Reason / purpose for cross-reference:

read-across source

Preliminary study:

none

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 8 948 mg/kg bw

Based on:

other: Recalculated based on the amount of H2O2 that can be formed from the reaction mass.

Gross pathology:

There were no gross internal lesions observed in any animal at necropsy.

Other findings:

Erythema, oedema and blanching of the test sites were observed in all rabbits 24 hours after administration. By day 4 of the study, all rabbits had necrosis which developed into eschar on day 7. At termination of the study, eschar and exfoliation were present in all rabbits.

Interpretation of results:

not classified

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

No classification for dermal toxicity is necessary for hydrogen peroxide (source substance-35%) according to Directive 2001/59/EC (adaptation of 67/548/EEC) or according to Regulation (EC) 1272/2008.

Executive summary:

The acute dermal toxicity of a 35 % aqueous solution of hydrogen peroxide (source substance) was tested according to US EPA Guidelines (PB82 -232984, August 1982) and under GLP conditions. Male and female young adult New Zealand White rabbits received a single dose of 2000 mg/kg (source substance) the test material under occlusion. Animals were prevented from manipulating the test site by the application of Elizabethan collars. Occlusion remained for 24 hours. After removal of the occlusion, animals were observed for 14 days. All animals showed local skin irritation exhibiting erythema, oedema and blanching of the test sites after 24 hours and eschar and exfoliation at termination of the study. No gross internal lesions were found at necropsy at termination of the study.

None of the animals died so that the dermal LD₅₀ value was greater than 2000 mg/kg.

This dose descriptor value was recalculated based on the amount of H₂O₂ that can be formed from the reaction mass of magnesium carbonate and magnesium hydroxide and magnesium peroxide, which results in an LD₅₀ > 8948 mg/kg.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Additional information

In order to be systemically available, a chemical needs to be absorbed, either via the oral, inhalatory or dermal route. Dissolution of solids is generally assumed to be a prerequisite for absorption. As the reaction mass of magnesium carbonate and magnesium hydroxide and magnesium oxide and magnesium peroxide is a solid inorganic multi-constituent substance, this means that Mg²⁺, OH^- and hydrogen peroxide are the species to be taken into account when assessing its systemic toxicity.

 

Acute oral toxicity

No reliable experimental data are available that assess the acute oral toxicity of the reaction mass of magnesium carbonate and magnesium hydroxide and magnesium oxide and magnesium peroxide. Nevertheless, the information available for the read-across substances is considered to be sufficient for the purpose of the chemical safety assessment and for the classification and labelling.

 

There are 2 key studies available for the acute oral toxicity of hydrogen peroxide: Finlay (1996) and FMC (1983).

In the study by Finlay, the acute oral toxicity of a 70% aqueous solution of hydrogen peroxide was tested in male rats at doses ranging from 500 to 1500 mg/kg bw, and in female rats at doses ranging from 500 to 1000 mg/kg bw. The test was carried out according to the OECD 401 guideline and GLP. The LD₅₀ value was determined to be 1026 mg/kg bw for male rats and 693.7 mg/kg bw for female rats.

In the study by FMC, the acute oral toxicity of a 35% aqueous solution of hydrogen peroxide was tested in male and female Sprague-Dawley rats at doses ranging from 630 to 2000 mg/kg bw for males and doses ranging from 794 to 1588 mg/kg bw for female animals. The test was carried out according to a US EPA Guideline and in compliance with GLP. The LD₅₀ value was determined to be 1193 mg/kg bw for males and 1270 mg/kg bw for female rats.

 

The key study (van Otterdijk, 2010) that is available for the acute oral toxicity of magnesium hydroxide is performed according to OECD guideline 423 and in compliance with GLP. In this study, three female Wistar rats are dosed with 2000 mg/kg bw magnesium hydroxide. The substance was administered via gavage of a 200 mg/mL magnesium hydroxide solution in water and the animals were observed for 15 days post exposure. No mortalities occurred during the study, resulting in an LD₅₀ > 2000 mg/kg bw.

 

From the above information it can be concluded that the toxicological effects anticipated to occur after oral exposure to the reaction mass of magnesium carbonate and magnesium hydroxide and magnesium oxide and magnesium peroxide will mainly be related to the formation of hydrogen peroxide from the reaction mass.

 

As this situation is similar to the reaction mass of calcium carbonate and calcium dihydroxide and calcium peroxide, the key study available for this substance is as well taken into consideration. A reliable and well-documented acute oral toxicity limit test is available that assessed the effects upon administration of 5000 mg/kg bw calcium peroxide to Sprague-Dawley rats. The study was performed according to GLP and internationally accepted protocols. No deaths occurred during the 14d observation period of the study and no gross internal lesions were observed at necropsy. Transient clinical observations included diarrhoea and abdominogenital staining. As a consequence, it was concluded that the LD50 of calcium peroxide is > 5000 mg/kg bw and the substance is practically non-toxic to both male and female rats.

 

 

For the purpose of the chemical safety assessment of the reaction mass of magnesium carbonate and magnesium hydroxide and magnesium oxide and magnesium peroxide, the LD50 for this multi-constituent substance can be calculated from the corresponding LD50 value for hydrogen peroxide. The LD₅₀ value determined by Finlay for the female rats is used as the starting point: 693.7 mg/kg bw. As the concentration of magnesium peroxide in the reaction mass is ca. 37%, 100 mg of the reaction mass contains 37 mg of magnesium peroxide, which corresponds to 0.66 mmol of magnesium peroxide. Therefore, 0.66 mmol (= 22.35 mg) of hydrogen peroxide is formed upon dissolution of 100 mg of the reaction mass.

 

The LD₅₀ of 693.7 mg/L for hydrogen peroxide can thus be extrapolated to result in the following LD₅₀ for the reaction mass of magnesium carbonate and magnesium hydroxide and magnesium oxide and magnesium peroxide:

100 mg reaction mass            yields              22.35 mg hydrogen peroxide

3104 mg reaction mass           yields              693.7 mg hydrogen peroxide

The extrapolated LD₅₀ for the multi-constituent substance is: 3104 mg/kg bw.

 

 

It is to be noted that this is a conservative approach, knowing that the acute oral toxicity test available for the reaction mass of calcium carbonate and calcium dihydroxide and calcium peroxide has an LD₅₀ > 5000 mg/kg bw, and the content of calcium peroxide in this test material is higher than the content of magnesium peroxide in the reaction mass of magnesium carbonate and magnesium hydroxide and magnesium oxide and magnesium peroxide. Therefore, it can be reasonably assumed that the LD₅₀ for the reaction mass of magnesium carbonate and magnesium hydroxide and magnesium oxide and magnesium peroxide will equally be > 5000 mg/kg bw.

 

Acute inhalation toxicity

No reliable experimental data are available that assess the acute inhalation toxicity of the reaction mass of magnesium carbonate and magnesium hydroxide and magnesium oxide and magnesium peroxide. Nevertheless, the information available for the read-across substances is considered to be sufficient for the purpose of the chemical safety assessment and for the classification and labelling.

 

A reliable acute inhalation toxicity study (Hoffman, 1990) is available for hydrogen peroxide in which male and female Sprague-Dawley rats received a single 4 -hour whole-body exposure to a 50% aqueous solution of hydrogen peroxide at the maximum attainable aerosol concentration of 170 mg/m³. All tested animals survived the exposure and subsequent 14 -day post-exposure observation period. Signs of treatment were minimal during the exposure but a few responses such as nasal discharge were noted during the whole 14 -day observation period. It was as a consequence concluded that the LD₅₀ value must be greater than the attainable aerosol concentration of hydrogen peroxide of 170 mg/m³.

 

For magnesium hydroxide the key study (van Huygevoort, 2010) is performed according to OECD 403 and GLP criteria. In this test, groups of 5 male and female Wistar rats were treated with magnesium hydroxide as an aerosol for 4 hours. The maximum attainable concentration was 2.1 mg/L (= 2100 mg/m³). No mortality or other relevant adverse effects were observed. Therefore, the LC₅₀ was concluded to be > 2100 mg/m³.

 

Additionally, a study with healthy volunteers (Kuschner et al, 1997) exposed to high doses of fine and ultrafine magnesium oxide particles for 15 to 45 minutes did not reveal any adverse effects.

 

Acute dermal toxicity

No reliable experimental data are available that assess the acute dermal toxicity of the reaction mass of magnesium carbonate and magnesium hydroxide and magnesium oxide and magnesium peroxide. Nevertheless, the information available for the read-across substances is considered to be sufficient for the purpose of the chemical safety assessment and for the classification and labelling.

 

The reliable study assigned as the key study in the REACH registration dossier for hydrogen peroxide dates from 1983 (Geiger 1983). It is carried out according to GLP and US EPA guidelines. In this experiment, male and female New Zealand White rabbits were exposed to a 35% aqueous hydrogen peroxide solution under occlusive coverage during 24 hours. The applied dose was 2000 mg/kg bw. No deaths occurred during the 14d observation period, but skin irritation effects were observed at the contact site. The LD₅₀ was thus found to be > 2000 mg/kg bw.

 

For magnesium hydroxide no study results are available that assess the acute dermal toxicity of the substance. The information available on the oral route demonstrates that the substance does not exert systemic toxicity. Furthermore, taking into account that it is unlikely that dermal absorption of an ionic substance will exceed the oral absorption, it can reasonably be expected that magnesium hydroxide will not cause systemic toxicity following dermal exposure as well.

 

In conclusion, based on the information available for the degradation products that are formed upon dissolution of the reaction mass of magnesium carbonate and magnesium hydroxide and magnesium oxide and magnesium peroxide, the reaction mass of magnesium carbonate and magnesium hydroxide and magnesium oxide and magnesium peroxide is not expected to exert acute systemic toxicity following dermal exposure.

Justification for selection of acute toxicity – oral endpoint
Well-documented GLP study according to internationally accepted guideline.

Justification for selection of acute toxicity – inhalation endpoint
Well-documented GLP study according to internationally accepted guideline.

Justification for selection of acute toxicity – dermal endpoint
Well-documented GLP study according to internationally accepted guideline.

 

Justification for classification or non-classification

In accordance to EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008, classification is not necessary for acute toxicity for the oral and dermal routes based on the available test results for the reaction mass of magnesium carbonate and magnesium hydroxide and magnesium oxide and magnesium peroxide and/or information available on the read-across substances hydrogen peroxide and magnesium hydroxide. The selected dose descriptor values (oral LD50 > 2000 mg/kg bw and dermal LD50 > 2000 mg/kg) are outside the classification criteria.

 

For the inhalatory route, no adverse effects were observed at the maximum attainable aerosol concentration generated from a 50% aqueous solution of hydrogen peroxide. Therefore, in the hydrogen peroxide registration dossier it is concluded that classifying for acute toxicity via inhalation is not required for mixtures containing < 50% hydrogen peroxide. Accordingly, as the maximum concentration of hydrogen peroxide that can be formed from the reaction mass of magnesium carbonate and magnesium hydroxide and magnesium oxide and magnesium peroxide is < 50%, classification for acute toxicity via inhalation is not required.

The effects of respiratory irritation observed upon exposure to hydrogen peroxide lead to a STOT-SE Cat. 3 classification for this substance. Therefore, a STOT-SE Cat. 3 with the respiratory tract as affected organ is also adopted for the reaction mass of magnesium carbonate and magnesium hydroxide and magnesium oxide and magnesium peroxide.