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The water solubility of Standolized soybean oil is very low (<1 mg/L). Since in general a compound needs to be dissolved before it can be taken up from the gastro-intestinal tract, it is unlikely that Standolized soybean oil will show a high systemic exposure after oral administration (1). However, its highly lipophilic character (log Po/w > 6) indicates that uptake by micellular solubilisation may be of particular importance. For risk assessment purposes oral absorption of Standolized soybean oil is set at 50%. The results of the toxicity studies (4) do not provide reasons to deviate from this proposed oral absorption factor.

Once absorbed, distribution throughout the body will be limited due to its low water solubility. Intracellular concentration is expected to be higher than extracellular concentration based on its lipophilic character. Absorbed Standolized soybean oil might undergo conjugation (3). The conjugates will either be excreted via the bile (high molecular weights compounds) or the urine (low molecular weight compounds).

Due to the very low vapour pressure (1.0 x 10-12 Pa at 25 °C) and the high boiling point (reaction and/or decomposition at 350°C) it is not to be expected that Standolized soybean oil will reach the nasopharyncheal region or subsequently the tracheobranchial or pulmonary region. If Standolized soybean oil reaches the tracheobranchial region it is likely that uptake of Standolized soybean oil by crossing the alveolar and capillary membranes will take place based on its highly lipophilic character (log Po/w >6). However, the low water solubility of Standolized soybean oil (< 1.15 x 10-4 g/L at 20.0 ± 0.5 °C) indicates that absorption from the respiratory tract will be limited. Overall, although it is unlikely that Standolized soybean oil will be available to a high extent after inhalation via the lungs, for risk assessment purposes the inhalation absorption of Standolized soybean oil is set at 100%.

Standolized soybean oil being a liquid has the potential to partition from the stratum corneum into the epidermis. However, the highly lipophilic character (log Po/w > 6) and the low water solubility (< 1.15 x 10-4 g/L at 20.0 ± 0.5 °C) of the substance indicate that the transfer between the stratum corneum and the epidermis will be impaired. Although the data are insufficient (no molecular weight available) to meet the criteria for 10% dermal absorption as given in the TGD (2), a dermal absorption of 10% is proposed for risk assessment purposes based on the available information. The results of the toxicity studies do not provide reasons to deviate from this proposed dermal absorption factor.

References:

1. Martinez NM, Amidon GL. Mechanistic approach to understanding the factors affecting drug absorption: a review of fundamentals. J Clin Pharmacol 2002; 43:620 -43.

2. ECB EU Technical Guidance Document on Risk Assessment, 2003. Guidance for the implementation of REACH. Guidance on information requirements and chemical safety assessment. Chapter R.7c: Endpoint specific guidance. European Chemical Agency, May 2008.

3. A. Parkinson. In: Casarett and Doull's Toxicology, The basic science of poisons. Sixth edition. Ed. C.D. Klaassen. Chapter 6: Biotransformation of xenobiotics. McGraw-Hill, New York, 2001.

4. G. Chibanguza (1988) Bodied linseed oil, 800 P. (Leinöl-Standöl, 800 P.) Acute oral toxicity in rats according to OECD-Guideline 401 (limit test), IBR Forschungs GmbH, Sudkampen Nr. 21, 3030 Walsrode 1, Germany. March 11, 1988.

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