Fatty acids, C18-unsatd., trimers

Bioaccumulation: aquatic / sediment

Description of key information

In accordance with Regulation (EC) No 1907/2006, Annex IX, 9.3.2, column 2 a bioaccumulation study does not need to be conducted as the substance has a low potential for bioaccumulation and a low potential to cross biological membranes.

Additional information

Due to the properties of the Dimerised Fatty Acids category members, their bioaccumulation potential in aquatic organisms is assumed to be low.

The Dimerised Fatty Acids are relatively large molecules (C16-18 as monomers, C36 as dimers and C54 as trimers) with high molecular weights (monomenric acids: ≈ 282 g/mol, dimeric acids 561 g/mol, trimeric acids 838 g/mol). Thus, they have a low potential to cross biological membranes (Lipinski et al., 2001).

From the toxicokinetic behaviour of mono- and oligomeric acids in mammals it can be assumed that unsaturated monomeric C16-C18 fatty acids are more readily absorbed than saturated fatty acids like octadecanoic and isooctadecanoic acid but less readily than fatty acids with shorter chain length. Very low absorption is reported for dimeric and trimeric fatty acids via the gastro intestinal tract and thus, most of the ingested fatty acids will be excreted in the faeces (≥ 80% for dimeric acid methyl esters (Hsieh and Perkins, 1976; Paschke et al. 1964)). In case of absorption fatty acids will undergo rapid metabolism and excretion (either in the expired CO2 or as hydroxylated or conjugated metabolite in the urine in the case of cyclic fatty acids) as they feed into physiological pathways like the citric acid cycle, sugar synthesis, and lipid synthesis.

Hence, no significant bioaccumulation in animal tissue is expected for Dimerised Fatty Acids due to general low absorbed amounts and their metabolic fate in organisms.

Furthermore, as dimerised fatty acids have very low water solubilities (sub-category dimers and trimers: < 0.52 mg/L), only low concentrations in the aquatic environment and thus low concentrations in aquatic organisms can be expected at all. The U.S. EPA HPV report (2009) states an expected low bioaccumulation potential based on the negligible solubility and their anionic nature.

In conclusion, Fatty acids, C18-unsaturated, trimers (CAS No. 68937-90-6) does not pose a risk to organisms in regard to bioaccumulation/biomagnification, consequently in accordance with Regulation (EC) No 1907/2006, Annex IX, 9.3.2, column 2 a bioaccumulation study does not need to be conducted as the substance has a low potential for bioaccumulation and a low potential to cross biological membranes.

 

References:

Hsieh, A. and Perkins, E.G. (1976). Nutrition and Metabolic Studies of Methyl Ester of Dimer Fatty Acids in the Rat. Lipids, 11(10):763-768.

Lipinski et al. (2001) Experimental and computational approaches to estimate solubility and permeability in drug discovery and development settings, Adv. Drug Del. Rev., 2001, 46, 3-26.

Paschke, R.F. et al. (1964). Dimer acid structures. The dehydro-dimer from methyl oleate and Di-t-butyl peroxide. Journal of the American Oil Chemists' Society 41(1):56-60.

U.S. Environmental Protection Agency (2009). Risk-Based Prioritization Document. Initial Risk-Based Prioritization of High Production Volume (HPV) Chemicals – Fatty Acid Dimers and Trimer Category. pp 1-19. Report date: April 2009.