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Description of key information

The absorption efficiencies used in the assessment are:
Dermal - 50%
Oral - 100%
Inhalation - 100%

Key value for chemical safety assessment

Bioaccumulation potential:
low bioaccumulation potential
Absorption rate - oral (%):
100
Absorption rate - dermal (%):
50

Additional information

The metabolism of TPP has been described as involving step-wise hydrolysis of the parent phosphite with release of phenol, or oxidation of the parent compound to triphenyl phosphate with subsequent step-wise hydrolysis to release phenol (Abou-Dania, 1992). This is supported by the hydrolysis data in the dossier, which shows rapid hydrolysis from TPP to phenol with little accumulation of intermediate products. Complete metabolism would result in the release of three molecules of phenol, and phosphoric acid. The hydrolysis rate of TPP is pH-dependent. Oxidation of TPP to the more stable phosphate form is the basis for its successful commercial use as an antioxidant. The relative bioavailability of the phosphite vs phosphate forms and their comparative hydrolysis kinetics have not been fully described.

 

While there are no specific toxicokinetic studies of TPP, toxicology testing appears to indicate that it is readily absorbed via the oral route. Due to its rapid hydrolysis in water, with a half-life of 0.5 hours at neutral pH (see hydrolysis section), it may be appropriate to consider the toxicokinetics of phenol for oral and inhalation routes since there would be a high likelihood of hydrolysis via these routes. The Phenol RAR (ECB 2006) concludes 100% absorption via the oral and inhalation routes and rapid elimination with low potential for bioaccumulation. These conclusions are also being applied to TPP.

 

The basis for the dermal absorption recommendation is discussed in Section 7.1.2.

 

Reference: Abou-Donia MB. (1992) Triphenyl Phosphite: A Type II Organophosphorus Compound-Induced Delayed Neurotoxic Agent. In J. Chambers and P. Levi (Eds), Organophosphates: Chemistry, Fate and Effects (pp 327 – 351). San Diego, CA: Academic Press.