Propane-1,2-diol, propoxylated

Endpoint summary

Additional information

Propane-1,2-diol, propoxylated, 1-4.5 mol propoxylated is a relative non-volatile liquid at room temperature. It is miscible with water and has a log P (measured) of < 0.3-0.9. It is essentially non toxic.

There are no studies on the toxicokinetics of propane-1,2-diol, propoxylated, 1-4.5 mol propoxylated. The approach employed in this toxicokinetics assessment is to examine data for the repeating unit and the initiating agent (propane-1,2-diol) and the oligomers formed from it (oxydipropanol [propane-1,2-diol, 1 mol propoxylated], {[methylethylene]bis[oxy]}dipropanol [propane-1,2-diol, 2 mol propoxylated]). Conclusions for the longer oligomers are based on those data and on structure activity information.

Discussion on bioaccumulation potential result:

Propane-1, 2-diol is both a core substance (initiator) and a repeating unit. For this particular polyol toxicokinetic information is available for one of the low molecular weight oligomers as well as the core substance/repeating unit. The information on the toxicokinetics of propane-1, 2-diol, propoxylated, 1-4.5 mol (the NLP polyol) is based on the information for propane-1,2-diol and its dimer (1 mol propoxylated propane-1,2-diol) and trimer (2 mol propoxylated propane-1,2-diol). Propane-1,2-diol has two hydroxy groups, thus oligomers are considered to be core substances with chains of between one and three repeating units. Commercial material contains a range of propoxylated propanediols.

At the molecular weight range of the NLP polyol (and up to the pentamer) the postulated mechanism for absorption is passive diffusion. At Mn >400 the facilitated diffusion mechanism probably applies, thus the calculated value for bioavailability of the hexamer, based on passive diffusion, is probably low. It would be inappropriate to calculate values for higher oligomers.

For the calculations of bioavailability of the commercial NLP polyol LogP values were calculated using the incremental fragment method of Suzuki and Kudo (1990). The propoxy groups have an important effect on the toxicity by modulating any toxicity arising from the core substance. The substitution of a hydroxyl group on a core compound by a propoxy group increases its logP value by 0.24 units and its molecular weight by 58 Daltons. The combined effect of these changes is to reduce the bioavailability by a factor of 1.53 (calculated using the Potts and Guy equation). The substitution of a hydroxyl group on a core compound by an ethoxyl- group decreases its logP value by 0.083 units and increases its molecular weight by 44 Daltons. The effect of these changes is to reduce the bioavailability by a factor of about 2.12. Thus the molecular weight changes are more significant than the logP changes in determining the bioavailability.