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Key value for chemical safety assessment

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No studies on toxicokinetic behavior of monoethanolamine oleate are available.

Monoethanolamine oleate is a UVCB substance containing primarily salts of monoethanolamine with fatty acids, with the main components being monoethanolamine oleate (34.19%) and oleic acid (33.41%). Other constituents are present at concentrations below 10%.

Oleic acid is considered to be non-hazardous and is exempted from registration according to Annex V of REACH, thus it is not expecited to be harmful upon body uptake. As the other main component, monoethanolamine oleate, is a salt of monoethanolamine and oleic acid, it is expected to dissociate into the respective monoethanolammonium cation and oleate anion in aqueous media, i.e. upon the uptake by the body. Thus the systemic human toxicological properties of monoethanolamine oleate are expected to be mostly governed by systemic human toxicological properties of monoethanolamine. The liver is the primary site for the metabolism of monoethanolamine and metabolites of monoethanolamine are found in urine of treated laboratory animals. Monoethanolamine is a normal constituent of the body (animal and human) and following condensation to phosphatidylethamolamine or transformation into phosphatidyl choline can be incorporated into cellular membranes. It can be converted into amino acids such as glycine and serine and incorporated into proteins. The molecule can be deaminated, with the amine group eliminated from the body as nitrogenous waste (urea or uric acid depending on the species) and the remaining carbon skeleton can be used as an energy source and oxidized fully to carbon dioxide. Monoethanolamine can be eliminated "unchanged" in the urine, with experiments in rats indicating that it is a dose-dependent phenomenom. This may be due to the saturation of metabolic pathways and suggests that excess levels in the body are not accumulated but can be directly eliminated via the kidneys. Ethanolamine is a normal constituent of human urine and in a limited numbers of subjects observed there was wide inter-individual variation of urinary levels (1).

Monoethanolamine oleate is sparingly soluble in water (280 mg/L) and has an (estimated) log Kow of 6.02. The high value of log Kow is expected to be not favourable for absorption. Regarding oral absorption, according to Chapter R7.C of REACH Guidance on information requirements and chemical safety assessment, the absorption of highly lipophilic substances (log P of 4 or above) may be limited by the inability of such substances to dissolve into gastrointestinal fluids and hence make contact with the mucosal surface. However, the absorption of such substances will be enhanced if they undergo micellular solubilisation by bile salts (Aungst and Shen, 1986). Substances absorbed as micelles (aggregate of surfactant molecules, lowering surface tension) enter the circulation via the lymphatic system, bypassing the liver. As monoethanolamine oleate is a surfactant (surface tension of 90% saturated aqueous solution is 26.2 mN/m), a micellular solubilisation may occur. For inhalation absorption, lipophilic substances (log P >0) have the potential to be absorbed directly across the respiratory tract epithelium. For dermal absorption, for substances with log Kow > 4, the rate of skin penetration may be limited by the rate of transfer between the stratum corneum and the epidermis, but uptake into the stratum corneum will be high. At log Kow above 6, the rate of transfer between the stratum corneum and the epidermis will be slow and will limit absorption across the skin. Uptake into the stratum corneum itself may be slow.

In the abscence of quantitative data on the absorption of the substance, the default values according to Chapter R.8 of REACH Guidance on information requirements and chemical safety assessment will be taken forward to DNEL derivation.

References

1. Binks SP, Glass DC et al., Smillie MV. Criteria document for ethanolamine. CEC. Occupational exposure limits. Vol. 14240 (1992).