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Description of key information

This toxicokinetic assessment is based on the physico-chemical properties of the substance and on toxicological data. Experimental studies on toxicokinetics were not performed. 

Key value for chemical safety assessment

Additional information

Physiochemical properties of AAS:

molecular weight: 190

Water solubility: AAS is only marketed as aqueous solution with a purity of approx. 50 %. Thus, the water solubility of the pure substance should be at least 500 mg/L.

Partition coefficient: log Kow = < -3.1

pH: 11.3 – 12.7 at 20°C


The following remarks on toxicokinetics are based on the physicochemical properties of AAS and on toxicological data. Experimental studies on toxicokinetics were not performed.

Absorption
Although the molecular mass of AAS is in the range suggestive of absorption from the gastrointestinal tract, the log Kow of below -3.1 and the high water solubility are not favourable for absorption. Additionally, in aqueous environment the salt is present in the dissociated, ionized form (pKa 5.9). The charged form will hinder absorption across biological membranes and a low or negliglible absorption can be assumed. This assumption is confirmed by the data for acute (Stropp, 1997) and subacute (Schladt, 2013) oral toxicity which do not show any toxicologically relevant effect up to and including the limit dose.

For substances with log Kow values below zero poor lipophilicity will limit penetration into the stratum corneum and hence dermal absorption. The assumption of negligible dermal absorption is confirmed by the data for acute dermal toxicity (Gillissen, 2012), skin irritation (Leuschner, 2012) and skin sensitization (Stropp, 1997), which do not show systemic effects after dermal exposure.

Due to its alkaline properties the aqueous AAS solution is slightly irritating to rabbit’s skin and severely irritating to rabbit’s eyes.

Metabolism
Based on the negative results of three in vitro genotoxicity tests performed with and without metabolic activation (Ames Test, Nern, 2011; HPRT Test, Wollny, 2012; Micronucleus test, Nern, 2012) it can be assumed that-reactive metabolites of AAS will not be generated in mammals in the course of hepatic biotransformation.

Elimination
Due to its high water solubility and low log Kow the elimination of AAS is assumed to be rapid. In addition, the log Kow of below -3.1 points to no potential for bioaccumulation.