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Key value for chemical safety assessment

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No studies on toxicokinetics are available. However, toxicokinetic information can be derived from the physicochemical properties and the chemical reactivity of the constituents of the reaction mass of magnesium carbonate and magnesium hydroxide and magnesium oxide and magnesium peroxide.

The reactions that take place when the different components of the reaction mass of magnesium carbonate and magnesium hydroxide and magnesium oxide and magnesium peroxide are dissolved in water are equally applicable when the systemic availability of the reaction mass of magnesium carbonate and magnesium hydroxide and magnesium oxide and magnesium peroxide is assessed. Indeed, the chemicals can only be systemically available to the organs when they can be transported to different parts of the body, which requires dissolution of the chemicals in the blood.

 

As a consequence, the chemical reactions driving the environmental fate and the environmental toxicity ofthe reaction mass of magnesium carbonate and magnesium hydroxide and magnesium oxide and magnesium peroxideare also relevant for the assessment of the toxicokinetics of this multi-constituent substance.

 

MgO2+ 2 H2O -> Mg2++ 2 (OH)-+ H2O2

H2O2+ H2O -> 2 H2O + O2

MgO + H2O -> Mg2++ 2 (OH)-

Mg(OH)2-> Mg2++ 2 OH-

MgCO3-> Mg2++ CO32 -

 

Therefore, the read-across from test results available for hydrogen peroxide and magnesium hydroxide is considered justified not only for ecotoxicological but also for toxicological endpoints. According to the applicable chemical reaction (see above), the amount of hydrogen peroxide formed is equimolar to the amount of magnesium peroxide present in the reaction mass. 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.

 

It is to be noted that hydrogen peroxideitself rapidly degrades both in tissues of first contact and blood due to the presence of catalase in these environments. Catalase is an iron-containing enzyme present in blood and many tissues. Its biological role is to scavenge the hydrogen peroxidethat is formed as a byproduct in many normal metabolic processes.