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Assessment of the Toxicokinetic Behaviour

 

Diphosphorus pentaoxide (CAS-No. 1314-56-3)

 

There are no studies available in which the toxicokinetic properties of Diphosphorus pentaoxide were investigated.

 

Diphosphorus pentaoxide (molecular weight of 142 g/mol) is a white hygroscopic solid, which is hydrolytically unstable (formation of phosphoric acid; see chapter 4.8). The substance is an inorganic salt and therefore the log Po/wdoes not need to be derived (see chapter 4.7 partition coefficient). Due to the rapid and complete hydrolysis of Diphosphorus pentaoxide to the water soluble Phosphoric acid a general accumulation of Diphosphorus pentaoxide is unlikely to occur.

 

Absorption

According to EU regulation 1907/2006, AnnexVII, column 2 acute toxicity studies do not need to be conducted since the substance is corrosive.

The exposure to Diphosphorus pentaoxide under physiological conditions (aqueous system, regardless of the exposure route) will principally lead to local effects due to the strong corrosivity of the generated Phosphoric acid. Consequently, the toxicity of Phosphoric acid/Diphosphorus pentaoxide, respectively is solely based on secondary effects of corrosivity. Due to the complete hydrolysis of Diphosphorus pentaoxide the only compound which will be available systemically after exposure is Phosphate, known to be an endogenous compound and food additive without reported toxic properties.

 

Metabolism

Since Diphosphorus pentaoxide is corrosive, an uptake of considerable amounts of this substance is very unlikely to occur. As already discussed, the only component, which will be bioavailable after P2O5exposure is the anionic Phosphate. No further metabolism is expected to occur.

Studies on genotoxicity performed with the hydrolysis product Phosphoric acid (Ames-Test; chromosome aberration test in Chinese hamster lung cells) were negative, i.e. there is no indication of a reactivity of Diphosphorus pentaoxide or its hydrolysis product (Phosphoric acid) under the test conditions.

 

Excretion

The only possible metabolite/hydrolysis product Phosphate, which is the sole component to that the organism is exposed under physiological conditions after P2O5exposure, is highly water soluble and has a molecular weight lower than 500 u. Therefore, Diphosphorus pentaoxide and its metabolite/hydrolysis product Phosphate are expected to be excreted completely and predominantly via the urine.