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Description of key information

The following assessment of the toxicokinetic profile of Reaction products of monoethanolamine and boric acid (1:), EC#701-025-6 is based on the physical chemical properties and toxicity data on the substance. No experimentally derived ADME data are available for this substance.

 

Substance Characterization

Analytical characterizations show that this substance meets the definition of a UVCB. This substance is a clear colorless to pale yellow liquid at ambient laboratory temperature (20°C)andonly exists in aqueous solution. It exists in a constant state of equilibrium and attempts to remove the water result in a shift of equilibrium, and a change in the nature of the molecule.The idealized molecular formula is given as C2H7NO.xBH3O3 and the MW is a minimum of 122.92, but the reality is too complex to define.

 

The complex structure of this UVCB substance is fully described in section 13. 

 


Physical Chemical Properties

Molecular weight, water solubility, log Kow, and vapour pressure are key physical chemical properties for assessing the toxicokinetics of a substance. This substance is a liquid. The substance is highly soluble in water (infinite according to OECD 202 study) and the partition coefficient (log Pow) of Reaction products of monoethanolamine and boric acid (1:1) in an OECD 107 study under GLP conditions was -1.9 at 19.7°C, pH 8.3-8.6 for the polyborate moiety and -1.1 for the organic moiety. The determined log Pow values were within the acceptable range of ± 0.3 log units. The substance has a negligible vapour pressure (< 1.3 x 10(-8) Pa and < 3.9 x 10(-8) Pa at 20°C (293K) and 25°C (298K) respectively).

 

Exposure Routes

The potential for exposure to this substance is limited by its use and physical chemical properties. The dermal contact route is considered to be the primary route of occupational exposure. Inhalation exposure is expected to be limited because this substance has a negligible vapour pressure. Because of the use pattern oral exposure is not an anticipated route of exposure, either to workers or the general public.

 

Absorption

Dermal

The dermal absorption of the main components of this UVCB substance is expected to be very limited because of the high solubility in water and low lipid solubility. ECHA endpoint specific guidance chapter R.7C indicates that substances with a MW <100 are favored for absorption (this substance has a MW >100) and given that water solubility is >10g/L and a Log PoW <0, the substance may be too hydrophilic to cross the lipid rich environment of the stratum corneum. Consequently, absorption via the dermal route is expected to be very low, which is supported by the toxicity data.

 

In a skin irritation study with an exposure period of 4 hours there was no evidence of skin irritation in either of three female rabbits. In an eye irritation study the substance was shown to be non-irritant. The results of an acute dermal toxicity study in rats indicate that dermal absorption of this substance is, as expected, very limited. Animals were given a single dermal dose of 2000 mg/kg for a 24-hour exposure period and observed for systemic and local effects for 14 days. No evidence of systemic toxicity was observed and there were no premature deaths. Slight to moderate erythema was noted at the test sites of the animals up to 3 days after exposure and all signs of irritation has disappeared by day 8. Animals showed expected gains in bodyweight over the study period, except for one female which showed no bodyweight gain during the first week but the expected gain in bodyweight during the second week, and another female which showed the expected bodyweight gain during the first week but a slight loss in bodyweight during the second week. In a Buehler sensitisation test the substance was shown to be a non-sensitizer when tested at 100% (induction concentration) and 100% in PEG400 (challenge concentration).

 

Based on the toxicological evidence, the test substance is not likely to be absorbed following dermal application.

 

Oral

Absorption in the gastrointestinal tract is predominantly influenced by the water solubility, ionization state, lipophilicity, and molecular weight of a chemical. This UVCB substance is highly soluble in water and has a very low lipid solubility (log Kow -1.1 to -1.9), which is outside the range of -1 to 4 that is considered favorable for absorption, even though the molecular weight is below that which may permit passage through aqueous pores (e.g., <200). The results of an acute oral toxicity study indicate no evidence of systemic toxic effects, which may be because the substance is not absorbed or because of low intrinsic toxicity. The physicochemical properties suggest low absorption is probable, and the in vitro mammalian cell assays suggest that the substance has low intrinsic toxicity. In vitro studies with bacteria show that the substance is not toxic to Salmonella typhimurium, either with or without metabolic activation. In mammalian cell genotoxicity assays in vitro the substance was shown to be non-toxic in the absence or presence of metabolic activation enzymes (S9 mix), but some modest toxicity was observed after long-term exposure (24 or 48 hours) in the absence of S9.

 

It is therefore considered that absorption via the oral route is likely to be very low.

 

Inhalation  

The substance is a liquid and has a negligible vapour, therefore the potential for inhalation exposure via vapour is highly unlikely.

 

Distribution

Once this UVCB substance (or at least the absorbable components) is absorbed, it is expected to be circulated via the blood to the liver and other tissues. Due to its strong hydrophilic nature it is predicted not to be absorbed by cells of the organs and tissues that it contacts except for the kidney. Therefore, the substance is highly unlikely to bioaccumulate because of its very low lipid solubility.

 

Metabolism

The absorbed components of this UVCB substance are expected to be unlikely to be metabolised by intracellular enzymes because the low lipophilicity of the substance will limit entry to cells. Metabolism is therefore expected to be minimal.

 

Elimination

Because of the physicochemical characteristics of this substance any absorbed material is expected to be excreted rapidly via the kidneys and non-absorbed material will be excreted via the faeces.

Key value for chemical safety assessment

Bioaccumulation potential:
low bioaccumulation potential

Additional information