p-phenylbenzonitrile

Endpoint summary

Description of key information

Based on the chemical structure and physico-chemical properties, no bioaccumulation potential is expected.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

There were no studies available in which the toxicokinetic properties of p-phenylbenzonitrile were investigated.

P-phenylbenzonitrile (molecular weight of 179 g/mol) is a white to yellow powder with a water solubility of 19.33 mg/L at 25 °C (see chapter "water solubility". The log Po/w was calculated to be 3.77 at 25 °C (see chapter "partition coefficient"), indicating that accumulation of the substance is not likely to occur.

Absorption

As a powder, particles will first have to dissolve into the surface moisture of the skin before uptake is possible. For partition from the stratum corneum into the epidermis sufficient water solubility is necessary. Based on a water solubility of 19.33 mg/L, low to moderate dermal uptake is likely. Additionally, a log Po/w between 1 and 4 favours dermal absorption. Taken together, dermal uptake of p-phenylbenzonitrile is likely to be possible (ECHA GD 7c, 2008).

 

P-phenylbenzonitrile has a very low calculated vapour pressure of 0.03 Pa at 25 °C (see chapter “vapour pressure”).

As a powder, dust formation of p-phenylbenzonitrile has to be expected. The dust may be inhaled and may be absorbed directly from the respiratory tract or, through the action of clearance mechanisms, may be transported out of the respiratory tract and swallowed.

No data are available about the particle size of the dust. Generally, water-soluble dusts or solids in solution would readily diffuse/dissolve into the mucus of the respiratory tract. The rate at which the particles dissolve into the mucus and the amount that can be absorbed is limited by the water solubility. Therefore, small amounts of the dust may be taken up by phagocytosis and transported to the blood via the lymphatic system. Furthermore, the moderate log Po/w of 3.77 (between -1 and 4) may favour the absorption directly across the respiratory tract epithelium by passive diffusion, and the low water solubility may enhance the penetration into the lower respiratory tract (ECHA GD 7c, 2008).

In summary, inhalation and respiratory absorption of the test item is likely to be possible.

Metabolism

Using the OECD toolbox vs.2.2, the (improved) liver metabolism simulator provided 6, and the skin simulator 0 potential metabolites (OECD toolbox vs.2.2, 2011).

Most of the predicted metabolites were hydroxylated forms of the parent compound. The cyano-group of the nitril is not a target of liver metabolism. Hydrolysis to the corresponding carboxylic acid is however known in microbial metabolism.

Excretion

The potential hydroxylated metabolites as well as the parent chemical have a molecular weight lower than 500 g/mol. The potential metabolites are expected to be soluble in water and therefore are likely to be excreted predominantly via the urine (ECHA GD 7c, 2008).

ECHA (2008). GD 7c. Endpoint specific Guidance.