L-gluco-Octitol, 1,5-anhydro-6,8-dideoxy-, (7.xi.)-

Endpoint summary

Description of key information

Absorption of Mexoryl SBF by oral route is likely to be limited while Mexoryl SBF as not volatil hydrophilic paste is unlikely to be absorbed at significant rate by dermal route or by inhalation.
If absorbed, Mexoryl SBF  may be transported through the circulatory system but distribution into fatty tissues should be low.  Moreover, Mexoryl SBF is expected to be mainly excreted in urine if absorbed.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

There is no specific requirement to generate toxicokinetic information in REACH. However, some indications regarding the toxicokinetic profile of Mexoryl SBF (i.e.absorption, distribution, metabolism and elimination) was derived from the physical chemical characteristics of the substance.

Physico-chemical characteristics

Mexoryl SBF is a multi-constituent substance composed of two consituents having a relatively low molecular weight of 192 g/mol. The substance is highly water soluble (> 590 g/L), hydrophilic based on the octanol/water partition coefficient (log Kow = -2.07,) and not volatile according to its vapour pressure (1.7x10^-6Pa at 25°C). The hydrolysis study concluded that Mexoryl SBF is considered as hydrolytically stable at pH 4, pH 7 and pH 9, with half-life at 25°C considered to be greater than 1 year.

 

Absorption

The physical chemical characteristics described above suggest that Mexoryl SBF is of adequate molecular size to participate in endogenous absorption mechanisms within the mammalian gastrointestinal tract. However, being hydrophilic, crossing of gastrointestinal epithelial barriers by Mexoryl SBF is likely to be limited even if the absorption may be promoted by the ability of the substance to dissolve into gastro-intestinal fluids and hence make contact with the mucosal surface.

Regarding the dermal absorption, Mexoryl SBF being hydrophilic paste (log Kow = -2.07), the rate of uptake into the stratum corneum is expected to be very low even nonexistent. Moreover, enhanced skin penetration is not expected since Mexoryl SBF is not a skin irritant or corrosive even after repeated (14 days) dermal application (see section 7.5.3).

The potential for inhalation toxicity was not evaluated in vivo. However, the vapour pressure of Mexoryl SBF (1.7x10^-6Pa at 25°C) indicated an absence of volatility and therefore no exposure by inhalation is anticipated. Thus, at ambient temperature, no respiratory absorption is expected under normal use and handling of the paste which is Mexoryl SBF.

Distribution

Systemic distribution of Mexoryl SBFcan be predicted from its physical chemical characteristics. Considering that the substance is hydrophilic (log Pow = -2.07) and highly water soluble, it is suggested that, upon systemic absorption, Mexoryl SBF may be transported through the circulatory system in association with a carrier molecule such as a lipoprotein or other macromolecule. However based on its very low lipophilic character, the substance won’t cross cellular barriers easily and therefore distribution into fatty tissues should be low.

Metabolism

Excretion

Having a molecular weight lower than 300, Mexoryl SBF is expected to be mainly excreted in urine if it is absorbed.

Following dermal exposure, hydrophilic substances, such as Mexoryl SBF, that have penetrated the stratum corneum at slow and low rate may be sloughed off with skin cells during the natural desquamation process.