Reaction Products of Dimethyl hydrogen phosphite and Alcohols C14-18, Even, Linear

Endpoint summary

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

Physicochemical properties:

The test item is a UVCB substance with an average molecular weight of 515 g/moL. The material is a waxy solid (melting point 26 to 42 °C) with a water solubility of 0.025mg/L at 20°C. Octanol/water partition coefficient was determined to be Log Kow > 10.0 for the UVCB substance as a whole (which is > 4, the bioaccumulation limit), and the vapour pressure is low (0.323 Pa at 25 °C). The substance is not expected 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 Kow and aqueous solubility. Log Kow values in the range of 0 - 3 and a MW less than 500 g/moL favours paracelluar transport. Molecules that pass through transcellular route are small (molecular weight up to around 200 g/moL) water-soluble molecules. Based on this, the test item is expected to have a low absorption potential from the GI tract because of the large molecule size (MW of 515 g/moL), high lipophilicity (Log Kow of >10) and low water solubility (0.025mg/L).  

 

Inhalation route

Volatility, aqueous solubility and Log Kow values determine the inhalation uptake. The substance is a low melting point solid at room conditions and has a high boiling point (300°C) suggesting that the potential for exposure through inhalation route is less likely at standard conditions. Low melting point solid having low water solubility, it will not readily dissolve into the mucus lining the respiratory tract and because of the high Log Kow value it would not be absorbed directly across the respiratory tract epithelium.

 

Dermal route

The skin absorption rate of molecules with a Log Kow value in the range of < -1 or > 4 and the molecular weight of > 500 g/moL is considered low. The test item is expected to be poorly absorbed through the skin considering its poor water solubility and the relatively high Log Kow.

 

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 substance is expected to have a high volume of distribution due to its high Log Kow values. The high Log Kow value of the test item can result in initially partitioning preferentially into highly vascularized lipid rich areas. 

 

Metabolism and excretion

The substance will undergo primary Phase I reaction followed by subsequent conjugation reactions (Phase II). The metabolites could be excreted via the urine or via the feces.

 

Conclusions

A qualitative judgement on the toxicokinetic behavior of the substance was performed based on the physico-chemical characteristics. The test item is expected to be poorly absorbed via the oral, dermal and inhalation routes. The substance is expected to be widely distributed through the body, if absorbed in to systemic circulation. The test item might 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.