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Key value for chemical safety assessment

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No toxicokinetic studies are available for the registered UVCB. An assessment is based on the physico-chemical properties and available toxicological studies.

Trideanamine, n-tridecyl-, branched and linear (DTDA) has a molecular weight of app. 380 g/mol (based on the main component > 90%), a very low vapour pressure of < 0.00001Pa, and is insoluble in water (< 30µg/L). The latter matches the high logPoW value of app. 12 for the main component.

Oral absorption is not hindered by the molecular weight, but will require micellular solubilisation due to a log PoW >> 4. Nevertheless, oral uptake is considered likely.

Absorption after inhalation can only occur, if aerosols are generated, since the very low vapour pressure prevents any significant vapour concentrations to occur. If aerosols are present, they will not be soluble in the mucus membrane of the upper airways and will enter the lower respiratory tract, where they can be absorped vie micellular solubilisation. In general, inhalation uptake is considered possible, but not the main route of exposure.

Based on the physico-chemical properties it would be expected that the substance quickly enters the outer layers of the skin, but remains in the stratum corneum (high lipophilicity, but no water solubility). But in in vivo studies for skin irritation even 1min of exposure led to skin necrosis. The fact that there was no real difference in exposure times confirms the theory of a quick uptake in the outer layers of the skin. Also, the observation of damaged areas far beyond the area of application support the theory that the substance is not easily taken up systemically, but remains in the skin. There, instead of staying in the stratum corneum, it can reach living cell layers and causes inflammation and cell death.

In summary, absorption can occur via the GI tract and inhalation, though inhalation exposure is limited to aersols, and is inefficient after dermal exposure.

Once in the body, the substance is expected to migrate to adipose tissues. A log PoW > 4 indicates the potential of bioakkumulation. Deamination and N-dealkylation have been described as metabolic pathways for secondary amines, though the branched structure and long side chains might limit efficiency of these reactions. Aliphatic chains can also be shortened in a step-wise process by C2 -units via mitochondrial beta-oxidation. This process is most efficient for linear molecules, but though side chains slow the reaction, they do not terminate it. Based on data on the isotridecanol used in the manufacturing process of the registered UVCB and the corresponding primary amine, metabolism is thought to occur and to eventually result in CO2 and urea, but it is thought to be slower for the secondary amine due to the presence of two long, branched side chains.