Glycerides, C8-18 and C18-unsatd.

Endpoint summary

Description of key information

Short description of key information on bioaccumulation potential result: 
No bioaccumulation of ‘glycerides, C8-18 and C18-unsatd. (SDA Reporting Number: 01-001-00)’

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

‘Glycerides, C8-18 and C18-unsatd. (SDA Reporting Number: 01-001-00)’ is composed mainly of triglycerides containing a glycerol backbone and linear fatty acids with a carbon chain length of C8-18 as well as unsaturated C18 fatty acids. The other known constituents are mono- and di-glycerides as well as free fatty acids. The toxicokinetics of glycerides and fatty acids are well known as a result of their widespread use in nutritional (food and feed), cosmetic and industrial applications for example.

When taken up orally, triglycerides are split in the intestinal lumen into glycerol and fatty acids with the help of lipases and bile secretions (in a process called lipolysis), then move into the cells lining the intestines (absorptive enterocytes). The triglycerides are rebuilt in the enterocytes from their fragments and packaged together with cholesterol and proteins to form chylomicrons. These are excreted from the cells, collected by the lymph system and transported to the large vessels near the heart before entering the blood. Various tissues can capture the chylomicrons, releasing the triglycerides to be used as a source of energy. When the body requires fatty acids as a source of energy, the hormone glucagon signals the breakdown of the triglycerides by hormone-sensitive lipases to release free fatty acids from the adipose cells (fat cells), the major site of triglyceride accumulation. The fatty acids are then broken down by stepwise elimination of C2-units in the mitochondrial β-oxidation. The C2-units are esterified to acetyl-Coenzyme A which directly enters the citric acid cycle where it is converted to carbon dioxide and energy (MacDonald, 1973; Robinson, 1973; Chen and Farese, 2002).

The extent of absorption in the gastro-intestinal system varies depending on the chain length of the fatty acids and their degree of saturation. Generally, short-chain fatty acids are better absorbed than the long chain counterparts. Also, absorption decreases with increasing saturation (MacDonald, 1973; Robinson, 1973; Chen and Farese, 2002).

No experimental studies were located for absorption through the dermal route. However,as per Section R.7.12.2.1 of REACH guidance document R7.C (May 2008),the extent of dermal absorption may be predicted based on physico-chemical properties, including:

-      Water solubility

-      Partition coefficient

-      Molecular weight / fatty acid chain length (inversely proportional)

‘Glycerides, C8-18 and C18-unsatd. (SDA Reporting Number: 01-001-00)’ is poorly water soluble (< 10 mg/L), has an estimated log Pow > 6 and a molecular weight range of 470 – 908(see Sections 1.3 and 4). As such,uptake into thestratum corneumof skin and further transfer into the epidermis are likely to be low. A default dermal penetration value of 10% can be assumed (REACH guidance document R7.C (May 2008)).

No significant inhalatoryexposure to ‘glycerides, C8-18 and C18-unsatd. (SDA Reporting Number: 01-001-00)’ will occur as the substance is semi-solid to solid under environmental conditions.