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Category name:
Alkyl Ethoxysulfate (AES)

Justifications and discussions

Category definition:
This category comprises alcohol ethoxysulfates of linear fatty alcohols (carbon chain range between C8 and C18) with an average number of ethylene oxide units of 1 to 2.5. The corresponding cations are sodium, magnesium, ammonium, mono- or triethanolamine, mono- or triisopropanolamine.
Category description:
The category applies to all systemic mammalian toxicity endpoints.
Category rationale:
Alcohol ethoxysulfates have a common metabolic fate that involves hydrolysis of the ether bond to the fatty alcohol and the ethoxysulfate chain.
Fatty alcohols, representing the variation in the structure of different alcohol ethoxysulfates, are oxidized to the corresponding fatty acid and fed into physiological pathways like the citric acid cycle, sugar synthesis and lipid synthesis. The remaining ethoxysulfate chain is renal excreted (see Figure 1).

Grouping of alcohol ethoxysulfates is justified because they are metabolised to either physiological occurring metabolites (fatty acids), which chemically behave in the same way as their nature counterparts or compounds of low toxicity.
The predicted metabolism of alcohol ethoxysulfates is supported by McDermott et al. (1975), who stated that there was no evidence of hydrolysis of the sulfate group or of metabolism of the ethoxylate portion of the molecule. The major metabolite found in urine had the structure –OOCCH2(OCH2CH2)3OSO3–.
Moreover, the HERA report on alcohol ethoxysulfates reveals, that this group of anionic surfactants shows a very homogenous toxicological potential by demonstrating low repeated dose toxicity as well as no mutagenic, genotoxic or carcinogenic properties and no reproductive or developmental toxicity.
Regarding the different anions, it is expected that the salts will be converted to the acid form in the stomach. This means that for all types of parent chemical the same compound structure eventually enter the small intestine. Hence, the situation will be similar for compounds originating from different salts and therefore no differences in uptake are anticipated.