Oxybispropanediol

Endpoint summary

Description of key information

Short description of key information on bioaccumulation potential result:

For risk assessment purposes the following absorption factors were derived:

oral absorption factor: 100%

dermal absorption factor: 100%

inhalation absorption factor: 100%

Key value for chemical safety assessment

Bioaccumulation potential:

low bioaccumulation potential

Additional information

In general, a substance needs to be dissolved before it can be taken up from the gastro-intestinal tract after oral administration. The relatively small molecular weight (166) and the high water solubility (>1000 g/L) of diglycerol indicates that uptake can take place through aqueous pores. However, the hydrophilic character of diglycerol (log Po/w -2.5) will limit this passive diffusion. Overall, it is likely that diglycerol is absorbed from the gastro-intestinal tract. For risk assessment purposes oral absorption of diglycerol is set at 100%. The results of the toxicity studies do not provide reasons to deviate from this proposed oral absorption factor.

 

Once absorbed, distribution of the test substance throughout the body is expected based on its relatively low molecular weight, and accumulation in the body will be limited based on its hydrophilic character. Based on its hydrophilic character, extracellular concentration is expected to be higher than intracellular concentration. Absorbed diglycerol might undergo conjugation. The conjugates will either be excreted via the bile (high molecular weights compounds) or the urine (low molecular weight compounds).

 

Due to the low vapour pressure (1.81 x 10^-5Pa) of the substance it is not to be expected that diglycerol will reach the nasopharyncheal region or subsequently the tracheobronchial or pulmonary region. However, if diglycerol reaches the tracheobronchial region no potential for absorption directly across the respiratory tract epithelium is expected due to its hydrophilic character (log Po/w -2.5). However, based on its water solubility (>1000 g/L) and relative low molecular weight (166) the substance may be retained within the mucus and subsequently absorbed through aqueous pores. Overall, although it is unlikely that diglycerol will be available to a high extent after inhalation via the lungs due to the low vapour pressure. For risk assessment purposes the inhalation absorption of diglycerol is set at 100%.

 

Diglycerol being a liquid has the potential to partition from the stratum corneum into the epidermis. Since the water solubility is above 10.000 mg/L (>1000 g/L) and the log Po/w below 0 (log Po/w -2.5), the substance may be too hydrophilic to cross the lipid rich environment of the stratum corneum, and dermal uptake will be therefore low. As the criteria for dermal absorption as given in the REACH guidance IR CSA R.7c (MW > 500 and log P_ow< -1 or > 4) are not met, 100% dermal absorption of diglycerol is proposed for risk assessment purposes. The results of the toxicity studies do not provide reasons to deviate from this proposed dermal absorption factor.

Discussion on bioaccumulation potential result:

The bioaccumulation potential is expected to be low based on the hydrophilic character of the substance.