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Key value for chemical safety assessment

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Absorption and Distribution :

Luperox 610 is an UVCB, colourless liquid, with a molecular weight of 288 g/mol for the main component 3-hydroxy-1,1-dimethylbutyl 2-ethyl-2-methylheptaneperoxoate. The substance is only slightly soluble in water (120 mg/L at 5.5°C). The logKow was measured to be 4.2 at 23°C. Based on this log Kow a BCF of 274 L/kg was calculated. Luperox 610 has a low vapour pressure of 254 Pa at 25 °C and is degraded hydrolytically. The hydrolysis by-products have not been identified.

Oral absorption is favored for molecular weights below 500 g/mol. Based on the high logKow of 4.2, Luperox 610 can be regarded as a lipophilic substance. Such a lipophilic compound may be taken up by micellular solubilisation. This mechanism may be of particular importance, as the substance is only slightly soluble and would otherwise be poorly absorbed. As Luperox 610 showed slight effects at 300 mg/kg bw/day in a 90-day study by oral route, it can be assumed that absorption across the gastrointestinal tract epithelium occurs, even if the observed effects were non-adverse.

Based on the low vapour pressure of 254 Pa at 25 °C, inhalation exposure is not likely. Nevertheless, if the substance reaches the lung, Luperox 610 may be absorbed by micellular solubilisation (see above). The low water solubility may enhance penetration to the lower respiratory tract. Together, this indicates low systemic availability after inhalation.

Similarly, based on physical-chemical properties, the substance is not likely to penetrate skin to a large extent as the high logKow and the low water solubility do not favour dermal penetration. Between water solubility of 100-10000 mg/l absorption is anticipated to be moderate to high. For substances with a log Kow between 4 and 6, the rate of penetration is limited by the rate of transfer between the stratum corneum and the epidermis. Only the uptake into the stratum corneum should be high. Furthermore, Luperox 610 is irritating to rabbit skin and damage to the skin surface may enhance penetration.

When reaching the body, Luperox 610 may be distributed into cells due to its lipophilic properties and the intracellular concentration may be higher than extracellular concentration particularly in fatty tissues. Based on its relatively high BCF value Luperox 610 may have the potential to accumulate within the body.

Metabolism:

Based on the structure of the molecule, hydrolysis of the peroxide function is expected to occur quickly.

Excretion:

As discussed above Luperox 610 is expected to be hydrolysed enzymatically in products having lowest molecular weight, allowing them to be excreted via the urine.