Registration Dossier

Administrative data

Link to relevant study record(s)

Description of key information

Absorption: Oral absorption 100%, Dermal absorption 0.9%.
Distribution/Metabolism: Once absorbed, AES are extensively metabolized by beta- or omega oxidation. Tissue accumulation can be excluded.
Excretion: AES are excreted principally via the urine. However, alcohol ethoxysulfates with longer ethoxylate chains (>7-9 EO units) are excreted at a higher proportion in the faeces. There is no evidence of hydrolysis of the sulfate group or of metabolism of the ethoxylate portion of the molecule.

Key value for chemical safety assessment

Bioaccumulation potential:
no bioaccumulation potential
Absorption rate - oral (%):
100
Absorption rate - dermal (%):
0.9

Additional information

To draw a coherent picture of the toxicokinetics, metabolism and distribution of the various members of the alkyl ethersulfates (also called alcohol ethoxysulfates) this endpoint is covered by read-across from structurally related alcohol ethoxysulfates. The possibility of a read-across from other alkyl ethersulfates in accordance with Regulation (EC) No 1907/2006 Annex XI 1.5. Grouping of substances and read-across approach was assessed. In Annex XI 1.5 it is given that a read-across approach is possible for substances, whose physicochemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity. The AES reported within the AES category show structural similarity. The alkyl chain length in the alcohol ethoxysulfates category varies from C8 to C18. In addition most chemicals of this category are not defined substances, but mixtures of homologues with different alkyl chain lengths (UVCBs). The most important common structural feature of the category members is the presence of a predominantly linear aliphatic hydrocarbon chain which is coupled to 1-2.5 ethanol moieties via ether bonds and a polar sulfate group, neutralized with a counter ion. This structural feature confers the surfactant properties of the alkyl ethersulfates. The surfactant property of the members of the AES category in turn represent the predominant attribute in mediating effects on mammalian health. Due to the structural similarities also the disposition within the body is comparable throughout the category. The AES of the category also have similar physico-chemical, environmental and toxicological properties, validating the read across approach within the category. The approach of grouping different AES for the evaluation of their toxicokinetics, metabolism and distribution as well as their effects on human health and the environment was also made by the Danish EPA (2001) and by a voluntary industry program carrying out Human and Environmental Risk Assessments (HERA (2003)). Data on absorption, distribution, metabolism and excretion reported within the discussion below summarize the data of the HERA report.

ADME

McDermott et al. (1975) studied the absorption of AES (C16;3 EO) and AES (C16, 9EO), labeled with14C in the 1-position of the alkyl chain, after oral exposure in man and rats. Seventy-two hours after administration of AES (C16; EO3), radioactive material was mainly excreted via urine (man: 80%; rat: 50%) and to a lesser extent via faeces (man: 9%; rat: 26%) and air (man: 7%; rat: 12%). For AES (C16; 9EO) however, the radioactivity was mainly excreted via faeces (man: 75%; rat: 82%) and to a lesser extend via urine (man: 4%; rat: 0.6%) and air (man: 6%; rat: 4%). The length of the ethoxylate portion of an AES molecule appears to determine the metabolic fate of the compound following oral administration in both man and rat. There was no evidence of hydrolysis of the sulphate group or of metabolism of the ethoxylate portion of the molecule. The major metabolite found in urine had the following structure:-OOCCH2(OCH2CH2)xOSO3-where x equals either 3 or 9, respectively.

In a similar investigation, Taylor et al. (1978) studied the metabolic fate of orally, intraperitoneally or intravenously administered AES (14C-C11; 3EO) and AES (14C-C12; 3EO) in the rat. The authors observed that both compounds were extensively metabolized (ω-, β-oxidation) with the proportion of radioactivity appearing in urine and respired air generally independent of the route of administration. Some sex differences in the proportions of radioactivity excreted in urine and respired air was seen, but total recoveries for both compounds were comparable. By the oral route, 67% of the administered radioactivity with AES (C11; 3EO) appeared in the urine of male rats compared to 45% in females; expired air contained 19% and 35% of administered radioactivity respectively; 4-5% was present in faeces for both sexes. The major urinary metabolite of AES (C12; 3EO) was identified as 2-(triethoxy sulfate) acetic acid, with AES (C11; 3EO), the major urinary metabolite was tentatively identified as 3-(triethoxysulfate) propionic acid.

 

Conclusion:

Following oral exposure, AES is readily absorbed in the gastrointestinal tract in human and rat and excreted principally via the urine or faeces depending on the length of the ethoxylate chain but independently of the route of administration. Once absorbed, AES is extensively metabolized by beta- or omega oxidation. The alkyl chain appears to be oxidized to CO2 which is expired. The EO-chain seems to be resistant to metabolism. 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 enters the small intestine. Hence, the situation will be similar for compounds originating from different salts and therefore no differences in uptake are anticipated.

The length of the ethoxylate portion in an AES molecule seems to have an important impact on the biokinetics of AES in humans and in the rat. Alcohol ethoxysulfates with longer ethoxylate chains (>7-9 EO units) are excreted at a higher proportion in the faeces. This is however not of interest for the AES within this category as their ethoxylation grade is 1 to 2.5.

 

Dermal absorption

There are two reliable and relevant studies available assessing the dermal absorption rate of AES. The study with AES (C12 -14; 2 EO) Na (CAS 68891-38-3) was performed according to OECD guideline 428 with human skin of the abdomen region (3 donors, n=2). The test substance was applied at a concentration of 10% for 24 h (Zengerly, 2009)

The mean amount removed from the skin surface (skin wash) ranged from 87.16% to 94.56% of the dose applied. The amounts in the receptor could not be quantified, since it was below the analytical limit of quantification (LOQ). The mean recovery in the two first tape strips was 1.48% during all performed experiments. In the further 18 tape strips a mean recovery of 2.86% was documented. The recovery values for the cryocuts have accounted 0.56% in mean.

The mean absorbed dose, sum of the amounts found in the viable epidermis, dermis and receptor medium was 0.56%. The mean recovery values have varied from 90.90% to 100.21%, which complies with the acceptance criteria of 100 ± 15%.

 

There is also an in vivo study according to OECD guideline 427 for AES (C12 -14; 2 EO) Na (CAS 68891-38-3) available (Aulmann, 1996). Wistar rats were exposed to 1% aqueous solutions of the test item for 15 min and 48 h under semi-occlusive conditions. The mean amount of AES (C12-14; 2 EO) Na (CAS 68891-38-3) removed from the skin surface after the 15 min exposure period (via washing) ranged from 92.8% to 97.2% of the dose and from 91.6% to 98.4% after 48 h when the skin was not washed until sacrifice. The amounts in faeces and skin could not always be quantified, since it was below the analytical limit of quantification (LOQ).

The mean absorbed dose, sum of the amounts found in urine, faeces and skin in the experiment with washing was about 0.1% and 0.9% without washing.

The mean recovery values varied from 98.6% to 103%.

 

Taking the results of both studies together the dermal absorption is very low. The in vitro study with human skin indicated the dermal absorption to be 0.56% within 24 h and the in vivo study indicated the dermal absorption to be 0.9% within 48 h. The mean recovery rates on the skin are greater than 87%. These data demonstrate that the test substance remains on the skin surface. Thus, the value of 0.9% dermal absorption is taken for the dermal absorption.

 

References:

Danish EPA - Environmental and Health Assessment of Substances in Household Detergents and Cosmetic Detergent Products (2001). Environmental Project No. 615, pp. 24-28

HERA (2003). Human & Environmental Risk Assessment on ingredients of European household cleaning products Alcohol Ethoxysulphates, Human Health Risk Assessment Draft, 2003. http: //www. heraproject. com.