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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

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 substances are extensively metabolized by - or ω-oxidation. Tissue accumulation can be excluded.


Excretion: AES substances are excreted predominantly via the urine. However, Alkyl Ether Sulfates with longer ethoxylate chains (> 7-9 EO groups) are excreted at a higher proportion in the faeces. There is no evidence of hydrolysis of the sulfate group.

Key value for chemical safety assessment

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

Additional information

ADME considerations based on physico-chemical properties


AES substances are salts consisting of a non-polar aliphatic hydrocarbon chain, which is coupled to a polar moiety containing 1 - 2.5 ethoxy groups via ether bonds, and a sulfate group, neutralized with a counter-ion. The alkyl chain length in the AES category varies from C8 to C18. This structural feature (non-polar chain bound to a polar terminal group) confers the surfactant properties of the AES substances. The surfactant properties of the AES substances in turn represent the predominant attribute in causing effects on human health.


Substances in the AES category are marketed in products, containing varying amounts of water. The tests examining their physico-chemical properties were conducted on pure dried substances after removing the aqueous phase. Importantly, the AES category member substances are not mono-constituent substances but substances with variable and/or unknown composition, i.e. substances of UVCB . Therefore, several physico-chemical properties are not defined or not applicable.


The physico-chemical properties of the AES category members that can be determined are similar over the category. Measured values are often in predictable narrow ranges (e.g. surface tension). The differences are related to the length of the alkyl chain, the ethoxylation degree of the material tested, or are due to different counter ions. However, most of the physico-chemical properties can only be estimated for surface active substances. The AES category members are pasty or waxy solids under ambient conditions, with broad melting ranges. They tend to decompose before boiling. Their molecular weight is mostly < 500 g/mol. They are non-volatile (vapour pressure << 100 Pa) and they do not partition into the air. AES substances are surfactants and the measured values for surface tension clearly identify the AES substances as surface-active. The accurate determination of a log Pow value is very difficult for surface-active substances. Surfactants tend to concentrate at hydrophilic/hydrophobic boundaries rather than to equilibrate between phases. Therefore, this parameter is of limited significance for AES member substances. However, all obtained values are low, i.e. log Pow < 3. Similarly, the determination of water solubility is difficult for surface-active substances. The AES substances are fully dissociating in water and miscible in any proportion with water. Estimated values for water solubility are in a range of several hundreds g/L.


Based on the relatively low molecular weight, the high water solubility and the log Pow value, absorption from the gastro-intestinal tract after oral exposure is expected for ionised AES substances, considering, however, that irritation is the leading health effect. Inhalation exposure to neat AES substances is considered negligible due to the low vapour pressure of the substances. However, inhalation in the form of droplets, dusts or other aerosols can occur. In case of inhalation, it is assumed that a certain proportion may well be absorbed. But again, the irritant properties are considered the leading health effect. Similarly, in case of dermal exposure, the irritant properties of AES substances are considered the leading health effect. Based on the physico-chemical properties, uptake to the stratum corneum is expected for AES substances. However, penetration from the stratum corneum to the epidermis and subsequent absorption to the circulation are expected to be very low. If absorbed and systemically available, it is assumed that the AES substances are supplied to the fatty acid metabolism and degraded via oxidation processes (e.g. β-oxidation). Subsequently, excretion via the kidneys and urine is the most likely route of excretion.


 


Experimental data on dermal absorption


There are two reliable and relevant studies available assessing the dermal absorption rate of the AES category member alcohols, C12-14, ethoxylated, sulfates, sodium salts (CAS No. 68891-38-3, EC No. 500-234-8). An ex vivo dermal absorption study was performed according to OECD guideline 428, and in compliance with GLP requirements, with human skin of the abdomen region (3 donors, n = 2). The test substance was applied at a concentration of 10% for 24 h (BASF, 2009). The mean amount removed from the skin surface (skin wash) ranged from 87.16% to 94.56% of the dose applied. The test substance amount in the receptor medium 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 mean absorbed dose of the test substance, i.e. sum of test substance amount found in the viable epidermis, dermis and receptor medium sum up to 0.56% of the applied dose. The mean recovery values have varied from 90.90% to 100.21%, which complies with the acceptance criteria (100 ± 15%). Under the conditions of the study, dermal absorption was found to be very low.


An in vivo study similar to OECD guideline 427, non-GLP compliant, was conducted with alcohols, C12-14, ethoxylated, sulfates, sodium salts (CAS No. 68891-38-3, EC No. 500-234-8; BASF, 1996a). Wistar rats were exposed to 1% aqueous solution of the test item for 15 min and 48 h under semi-occlusive conditions. The mean amount of alcohols, C12-14, ethoxylated, sulfates, sodium salts (CAS No. 68891-38-3, EC No. 500-234-8) rinsed off the skin surface after a 15 min exposure period ranged from 92.8% to 97.2% of the dose and from 91.6% to 98.4% after 48 h exposure, 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 LOQ. The mean absorbed dose of the test substance, i.e. sum of test substance amount found in urine, faeces and skin was about 0.1% and 0.9% of the applied dose in the experiment with washing (15 min exposure) and without washing (48 h exposure), respectively. The mean recovery values varied from 98.6% to 103%. Under the conditions of the study, dermal absorption was found to be very low.


 


Data on toxicokinetics described in HERA report


The following studies were conducted in the course of a voluntary industry programme carrying out Human and Environmental Risk Assessments (HERA, 2003, and references therein). The programme investigated the toxicokinetic behaviour of AES substances with various C-chain lengths (alkyl moieties) and ethoxylation degrees (number of ethoxy (EO) groups). The studies compiled in the HERA report were performed mainly with AES substances carrying 0 - 8 EO groups. However, the information derived in those studies is considered appropriate to assess the toxicokinetic behaviour of the members of the AES category.


The nomenclature used in this section follows the one applied in the HERA report. This nomenclature is generally accepted throughout the surfactant industry and thus widely used. The short names of AES substances contain the description of the alkyl moiety (the C-chain length), followed by ‘AE’ (alkyl ether) and the number of the ethoxy groups. Examples are C8AE4S, C12AE3S and C16AE8S representing tetraethylene glycol monooctyl ether sulfate, triethylene glycol mono dodecyl ether sulfate and octaethylene glycol monohexadecyl ether sulfate, respectively.


 


Absorption and excretion


McDermott et al. (1975) studied the absorption of C16AE3S and C16AE9S, labelled with 14C in the 1-position of the alkyl chain, after oral exposure in man and rats. Seventy-two hours after administration of C16AE3S, 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 C16AE9S 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 toxicokinetic behaviour of the compound following oral administration in both man and rat. 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 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 14C-C11AE3S and 14C-C12AE3S in the rat. The authors observed that both compounds were extensively metabolized (β-, ꞷ-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 C11AE3S 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 C12AE3S was identified as 2-(triethoxy sulfate) acetic acid, with C11AE3S, the major urinary metabolite was tentatively identified as 3-(triethoxy sulfate) propionic acid.


Taylor et al. (1978) also measured the percutaneous absorption of 14C-labelled NaC12AE3S. The NaC12AE3S was applied to rats as 150 µL of a 1% v/v solution. The 14C-levels were measured in urine collected over 48 h. Penetration of NaC12AE3S was 0.39 ± 0.12 µg/cm2. In experiments in which application was continued for up to 20 min, skin penetration was proportional to the duration of the contact. It was also proportional to the number of applications.


 


Summary of toxicokinetics from HERA report


Following oral exposure, AES substances are readily absorbed in the gastrointestinal tract in man and rat and excreted mainly via the urine. The length of the ethoxylate portion, i.e. the number of ethoxy (EO) groups, in an AES molecule seems to have an important impact on the toxicokinetic behaviour of AES substances in humans and in the rat. AES substances with longer ethoxy chains (> 7 - 9 EO groups) are excreted at a higher proportion in the faeces. Once absorbed, AES substances are extensively metabolized by β- or ꞷ-oxidation.


The dermal absorption of AES substances is relatively poor as can be expected from an ionic molecule. The percutaneous absorption of C12AE3S was measured in a rat in vivo study. The study determined a dermal flux of the tested compound of 0.0163 µg/cm2/h.


 


Conclusion on toxicokinetic behaviour


Following exposure, the irritating properties of the AES category member substances are considered as the leading health effect at the site of first contact. Following oral exposure, AES substances are readily absorbed in the gastrointestinal tract in human and rat and excreted mainly via the urine or faeces depending on the length of the ethoxy (EO) chain but independently of the route of administration. Following dermal exposure, dermal absorption of AES substances is very low (< 1%). Available ex vivo and in vivo data demonstrate that the AES test substance remains on the skin surface. Once absorbed, AES substances are extensively metabolized by β- or ꞷ-oxidation. The alkyl chain appears to be oxidized to CO2, which is expired. The EO-chain seems to be resistant to metabolism. The length of the ethoxy chain, i.e. the number of ethoxy (EO) groups, in an AES molecule seems to have an important impact on the toxicokinetics of AES substances in humans and in the rat. AES substances with ethoxy chains > 7 - 9 EO groups are excreted at a higher proportion in the faeces. This is however not of relevance for the present AES category members as their mean ethoxylation degree is < 2.5.