Fatty acids, tall-oil, reaction products with ethanolamine, ethoxylated

Endpoint summary

Description of key information

Due to the high lipophilicity and the relatively high molecular weight, an uptake by micellular solubilisation is expected after oral exposure or inhalation. As demonstrated in animal studies for the structural related substance lauric acid diethanolamine condensate (LDEA), the dermal uptake is limited (please refer to ch. 13 for read-across justification). Once absorbed, the substance is expected to be efficiently metabolized by hydrolases and other metabolic enzymes. The excretion of the degradation products is via exhalation air (carbon dioxide) or urine (water and Phase II-conjugates). A bioaccumulation potential is not expected.

Key value for chemical safety assessment

Bioaccumulation potential:

low bioaccumulation potential

Additional information

1.    Chemical and physic-chemical description of the substance

The target substance is a reaction product of tall-oil fatty acids (mainly C16-18 and C18-unsaturated) with ethanolamine and ethylene oxide. It can be described with the CAS no. 61791-19-3 (CAS name: Fatty acids, tall-oil, reaction products with ethanolamine, ethoxylated (1.5EO)).

The composition of the substance was investigated by analytical methods (IR-, UV-Vis-, NMR-spectroscopy, water determination, GC/MS and LC analysis) and resulted in the identification of three major components:

~ 33% Octadecenamide or octadecadienamide, reaction product with N-(2-hydroxyethyl), 1-EO
~ 25%Octadecenamide or octadecadienamide, reaction product with N-(2-hydroxyethyl), 2-EO
~14%  Octadecenamide or octadecadienamide, reaction product with N-(2-hydroxyethyl)

These three major components account for appr. 72% of the substance. Other minor components are present at a concentration of <10% in each case.

Description of the physico-chemical properties:

- physical state (20°C): liquid

- vapour pressure (20°C):≤ 0.51 Pa (0.51*10-2 mbar)

- molecular weight: appr. 326 Da (without EO), appr.370 Da (1 EO), appr. 414 Da (2 EO)

- log Pow (23 °C): > 5 (experimental result; Dermwin calculation: 5.97 (without EO), 5.70 (1 EO) and 5.42 (2 EO))

- water solubility: 30 mg/L at 20 °C (experimental data)

- Boiling point: substance decomposes at about 297°C

 

The substance is characterized by a lipophilic nature, a low volatility and relatively low water solubility. Though the substance is composed of several individual components, the structural resemblance as well as the PC data indicate a relatively homogenous toxikokinetic behavior.

2.     Toxicokinetic assessment

 

No experimental data on absorption, metabolism and distribution are available for the substance. Based on the structure and the physico-chemical properties of the substance, the toxikokinetic behavior can be evaluated.

2.1 Absorption:

With a molecular weight of 326-414 Da, the components of the target substance are expected to have a moderate absorption potential after oral intake. The high log Pow of >5 suggests and the low water solubility (<30 mg/L) suggest that passive diffusion is rather unlikely, and an uptake by micellular solubilisation is favored. Altogether, a worst case oral absorption of 100% is assumed for the target substance.

With regard to absorption after inhalation, the target substance has a low vapour pressure of ≤ 0.51 Pa and decomposes at about 297°C, indicating that inhalation as a vapour will be negligible. If the substance reaches the respiratory tract, passive diffusion is unlikely due to the high log Pow, the relatively low water solubility and the rather high molecular weight. Theoretically, a systemic uptake could take place after micellular solubilisation.

The relatively high molecular weight (326-414 Da) and the high lipophilicity (log Pow >5, water solubility = 30 mg/L) suggests a limited dermal uptake. It is expected that the target substance might enter the stratum corneum, but the transfer to the epidermis (and thus the bioavailability after dermal contact) will be limited. These theoretical assumptions are supported by data obtained with the read-across substance lauric acid diethanolamine condensate (LDEA, CAS RN 120-40-1). The available studies on LDEA demonstrate that absorption through rat skin is slower than through mouse skin. In rats, 25 to 30% of the dose penetrated the skin during the first 72 hours, whereas in mice, 50 to 70% of the applied dose was absorbed in the first 72 hours. Therefore the target substasnce is expected to have a similar dermal absorption profile. It is also important to consider that the degree of dermal absorption through human skin is expected to be less than that of animal skin, since human skin is less permeable (factor of 3-7). Therefore the absorption rate through human skin can be expected to be less than 30%, consequently 10% absorption can be assumed.

 

2.2 Metabolism and Excretion:

In principle, the ether linkage between the EO chain and the ethanolamine as well as the amide function are points of attack by metabolic enzymes.

It has been demonstrated for the group of fatty alcohol ethoxylates that the ether linkage is likely to be hydrolyzed, resulting in (poly)ethylene glycols and an alcoholic chain (e.g. summarized in the HERA report, http://www.heraproject.com/RiskAssessment.cfm?SUBID=34). This ether cleavage is also likely to take place in the metabolism of the target substance, with mono- or diethylene glycol and N-(2-hydroxyethyl) octadec(adi)enamide as products. In the studies with fatty alcohol ethoxylates evaluated by the HERA project, the polyethylene glycols were excreted via urine (in the case of shorter chains) and air (as CO₂, mainly observed for longer polyethylene glycols). As the cleavage of the target substance results in the shorter molecules mono- and diethylene glycol, a major excretion via urine is assumed.

The N-(2-hydroxyethyl) octadec(adi)enamide can further be metabolized in the Phase I metabolism by enzymes with a hydrolysis function. The resulting 2-aminoethanol will be further extensively metabolized, as shown in an in vivo study in mice (Klain et al, 1985). The major site of metabolism for 2-aminoethanol was the liver, where 24% of the applied radioactive dose was recovered. The same amount (24.3%) was recovered at the skin administration site (24.3%). Extensive metabolization was indicated by appearance of labelled carbon dioxide in skin and hepatic amino acids, proteins and incorporation into phospholipids, and by recovery of over 18% of radioactive dose as [14]-CO₂. Urea, glycine, serine, choline, and uric acid were the urinary metabolites of 2-aminoethanol.

The other cleavage product - fatty acids - will be further metabolized like any other dietary fatty acid, undergoing an oxidation to carbon dioxide and water.

In conclusion based on the available toxicokinetics data, the target substance is expected not to significantly bioaccumulate based on the rapid and effective metabolism by P450 enzymes into innocuous polar metabolites which are then rapidly excreted (primarily) in urine. Consequently it is reasonable to assume that no significant risk from bioaccumulation is expected to occur following oral or dermal exposure to the target substance.