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Description of key information

Key value for chemical safety assessment

Additional information

As described in Section 1, CTO is a UVCB substance containing at least 80 different constituents. No in vitro or in vivo toxicokinetic studies are available for the whole product and it would not be scientifically feasible to conduct such a test. 

The constituents of CTO are all naturally occurring secondary metabolites of pine trees and many other types of plant. Fatty acid constituents in particular are an important dietary source for humans, and the sterol constituent β-sitosterol is used as a supplement in certain types of fat spreads due to its cholesterol-lowering properties.

Metabolism and other biological behaviour of these constituents has been extensively reported in the published literature and, in the absence of significant toxicological effects (see Sections 5.2-5.9), it is not necessary for the purposes of this CSR to describe these in detail.

Some toxicity studies, for example the repeated oral exposure with Distilled Tall Oil (Clubb and Daly, 2002), show clear evidence of absorption and distributionin vivo(particularly to the liver). Uptakeviamicelleular solubilisation is an important mechanism for substances with log Kow >4 and low water solubility (REACH Technical Guidance Chapter R7c).

In the only available dermal toxicity study for CTO (Bernat, 2005), there were no clinical signs of toxicity or gross pathological findings at the limit dose level of 2000 mg/kg/day. It is therefore not possible to determine if any dermal absorption occurred. Dermal absorption is optimal for substances with log Kow 2-3, and is favourable for those with log Kow in the range 0-4. All the constituents of CTO have log Kow >4 in the neutral form (relevant for dermal exposure). For those in the log Kow range 4-6, the rate of 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. 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. (REACH Technical Guidance Chapter R7c).

The positive Local Lymph Node Assay skin sensitisation test for CTO (Weber, 2005) indicates that some constituents do penetrate the epidermis and reach the lymph nodes via epidermal Langerhans cells.

Significant inhalation exposure is not expected for this non-volatile substance, and no toxicity data are available for this exposure route.