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Description of key information

Minimal absorption via oral, dermal or inhalation routes of exposure has been predicted based on the experimental data, physico-chemical properties of the substance and expected use patterns., if absorbed, the test item could undergo primary Phase I reaction followed by subsequent conjugation reactions (Phase II). The conjugated metabolites are expected to be excreted via the urine or via the faeces. The substance will not bioaccumulate.

Key value for chemical safety assessment

Bioaccumulation potential:
no bioaccumulation potential

Additional information

Physico-chemical properties

 

The test item is a UVCB substance with an average molecular weight of 673 g/moL. The material is a liquid (melting point 0 ± 3 °C) with a determined water solubility of 9.34 mg/L. Octanol/water partition coefficient was estimated as Log Pow 5.14 based on the properties of the environmentally relevant component (which is > 4, the bioaccumulation limit), and the vapour pressure is low (0.013 Pa at 25 °C). The substance was determined to be surface active.

 

Absorption

 

Oral route

 

Passive diffusion (transcellular) and passage through the aqueous pores (para-cellular) are the primary absorption mechanisms of molecules from the gastro-intestinal (GI) tract. Key physicochemical properties that determines the mechanism of absorptions are molecular weight (MW), Log p and aqueous solubility.  Log p values in the range of 0 - 3 and a MW less than 500 g/moL favors paracelluar transport.  Molecules that pass through transcellular route are small (molecular weight up to around 200 g/moL) water-soluble molecules.  The substance is surface active (surface tension determined to be 50.0 mN/m at 21.0 ± 0.5 °C for test item prepared at 90 % saturation in water), consequently it may participate in micellar transport into the hepatic portal system along with other lipophilic substances (e.g., dietary fats). Based on the sum of these characteristics,the test item is expected to have a low absorption potential from the GI tract because of the large molecule size (MW of 673 g/moL), high lipophilicity (Log Pow of 5.14) and low water solubility (9.34 mg/L).

  

Inhalation route

 

Volatility, aqueous solubility and log P values  determine the inhalation uptake. The substanceis liquid at room temperature and has a high boiling point (278°C) suggesting that the potential for exposure through inhalation route is less likely at standard conditions. The test item is alsopoorly water soluble, will not readily dissolve into the mucus lining the respiratory tract, will not be absorbed directly across the respiratory tract epithelium because of the high log Pow value.

 

Dermal route

 

The skin absorption rate of molecules with a log p value in the range of < -1 or > 4 and the molecular weight of > 500 is considered low. The substanceis expected to be poorly absorbed through the skin considering its poor water solubility and the relatively high log p.

 

Distribution

 

The extent of distribution of molecules is affected by molecular weight, lipid solubility, pKa, and plasma protein binding (PPB). Molecules that are lipophilic at pH 7.4 and high plasma protein binding are likely to have high volume of distribution (Vd). Physicochemical properties that influence PPB include lipophilicity and pKa. In general, chemicals with high lipophilicity and/or ones with acidic character will have a greater degree of PPB, than more hydrophilic or basic compounds.Once absorbed,the substanceis expected to have a high volume of distribution due to its high log Pow value. High log Pow for the test item can result in initially partitioning preferentially into highly vascularized lipid rich areas. 

 

Metabolism and excretion

 

If absorbed, the test item could undergo primary Phase I reaction followed by subsequent conjugation reactions (Phase II). The conjugated metabolites are expected to be excreted via the urine or via the faeces.

 

Conclusions

A qualitative judgement on thetoxicokineticbehavior ofthe UVCB substancewas performed based on the physico-chemical characteristics. Thetest itemis expected to be poorly absorbed via the oral, dermal and inhalation routes and will be widely distributed through the body. The substance might undergoprimary Phase I reaction followed by subsequent conjugation reactions (Phase II). The conjugated metabolites are expected to be excreted via the urine or via the faeces.

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