Methyl ester of fatty acids, Cx-Cy, Hydroxymethylated

Phototransformation in air

Description of key information

The components of this UVCB mixture do not possess chromophoric functional groups, and their fate will not be significantly affected by direct photolysis.  Rather, indirect photolysis via reaction with photochemically-generated hydroxyl radical is expected to be the dominant process affecting the fate of these substances in the atmosphere.  Dissipation half-lives for the five principal components of this mixture were estimated using an accepted QSAR (AOPWIN), and range from 9.4 to 20 hours.

Additional information

The Natural Oil Monomer substance has a measured vapour pressure of< 3.95 x 10^-3Pa, and therefore has low potential for volatilization or emission to the atmosphere. In the unlikely event of atmospheric emission, the fate of the Natural Oil Monomer components is most likely to be affected by indirect photolysis, via reaction with photochemically-generated hydroxyl radical. The half-life for indirect photolysis of each of the five major components of the Natural Oil Monomer was predicted using the AOPWIN v1.91 software (U.S. EPA, 2005). The estimated half-lives for reaction with photochemically-generated hydroxyl radical, assuming atropospheric hydroxyl radical concentration of 500,000 molecules OH/cm³, range from 9.4 hours (methyl trihydroxymethyl stearate) to 20 hours (methyl palmitate).

 

As evidenced from the UV/VIS spectrum of the Natural Oil Monomer, the substance exhibits little or no absorbance of light at wavelengths > 290 nm, which is the cut-off for solar irradiation that penetrates into the troposphere. Therefore, direct photolysis in air is not expected to be an important process affecting the fate of the Natural Oil Monomer components in the atmosphere.