Sulfuric acid, mono-C9-11-alkyl esters, sodium salts

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

migrated information: read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Expert judgement combined with experimental data. According to the ECHA guidance document “Practical guide 6: How to report read-across and categories (Dec 2012)”, the reliability was changed from RL1 to RL2 to reflect the fact that this study was conducted on a read-across substance.

Data source

Reference

Reference Type:

secondary source

Title:

SIDS Category of Alkyl sulfates, Alkane sulfonates and Alpha-olefin sulfonates

Author:

OECD

Year:

2007

Bibliographic source:

UNEP Publications

Materials and methods

Objective of study:

toxicokinetics

Principles of method if other than guideline:

No guideline exists for this type of appraisal.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Category of Alkyl sulfates

IUPAC Name:

Category of Alkyl sulfates

Details on test material:

not applicable

Radiolabelling:

other: partly

Test animals

Species:

other: rat, dog and human

Sex:

male/female

Details on test animals or test system and environmental conditions:

not applicable

Administration / exposure

Route of administration:

oral: unspecified

Duration and frequency of treatment / exposure:

Various, for details see SIDS

Doses / concentrations

Remarks:

Doses / Concentrations:
Various, for details see SIDS

No. of animals per sex per dose / concentration:

Various, for details see SIDS

Control animals:

other: Various, for details see SIDS

Results and discussion

Main ADME results

Main ADME results 1

Type:

absorption

Results:

After oral administration, alkyl sulfates are well absorbed in rats, dogs and humans.

Main ADME results 2

Type:

excretion

Results:

The major path of excretion of the alkyl sulfates is the urine.

Toxicokinetic / pharmacokinetic studies

Details on absorption:

After oral administration, alkyl sulfates are well absorbed in rats, dogs and humans. This was indicated by excretion of up to 98% of the dose administered (maximum for C12ASO4Na in the urine and by comparison of excretion after oral and i.v. or i.p. application for C11ASO4K, C12ASO4K and C18ASO4Na alkyl sulfates.

Details on distribution in tissues:

After application of 14.4 mg/kg of the erythromycin salt of C16ASO4 to dogs or 250 mg/person to humans, radioactivity in plasma was maximal within 30 minutes to 2 hours of oral administration in both species indicating rapid absorption. The plasma concentration declined rapidly afterwards and reached 10% of the maximum concentration after 6 hours, indicating rapid elimination.
 
Whole body autoradiography has been performed to follow the distribution of 35S-C10ASO4K, C12ASO4K and C18ASO4K or their metabolites within the body with time in experiments with rats after i.p. injection. For all compounds the only organs, where radioactivity was detected, were the liver and the kidney. The levels (not quantified) were highest 1 h after application. C10 AS was cleared from tissues more rapidly than C18. After 6 hours, only traces of the C10 salt remained in the kidney, whereas it took 12 hours for the C18 salt to be cleared from the kidney.

Details on excretion:

The major path of excretion of the alkyl sulfates is the urine. The data show, that there are only minor differences for the alkyl sulfates of different chain lengths in the overall excretion after i.p. application. There are also no major differences in overall excretion between male and female rats or after oral, intraperitoneal or intravenous application. The rate of excretion in the urine, however, is somewhat different. After oral as well as i.p. application, excretion of the C12 compound is complete within 6 hours after application. In contrast the excretion amounts only to about 60% (C10), 40% (C11), 15% (C18) after i.p. application, and to 25% for C11or C186 hrs after oral application. This indicates faster metabolism of the C12 compound than for the other chain lengths.
 
Lower amounts of the alkyl sulfates are excreted via the feces within 48 hrs after oral application for the C12, C16and C18 compounds. The lowest value was obtained for the C12, while the highest values with considerable variation of 2.5 - 19.9% (2 m, 2f) were found for C11. In the bile from < 1 to 7.7% (highest amount with C11) of the dose applied was found up to 6 hours after i.v. application, indicating, that the amounts in the feces are mainly due to metabolism and not to unabsorbed compound. In addition the distribution of label in urine and feces from orally administered potassium dodecyl 35S-sulfate (C12A35SO4K) was similar in both antibiotic-treated and untreated rats, indicating that the intestinal flora does not play a significant role in the metabolism of this compound.

Metabolite characterisation studies

Metabolites identified:

yes

Details on metabolites:

Alkyl sulfates are extensively metabolized in rats, dogs and humans. This was tested with radiolabelled C10, C11, C12, C16 and C18 alkyl sulfates, potassium salts.
The postulated mechanism is degradation involving omega-oxidation, followed by beta-oxidation, to yield metabolites with chain lengths of C2 and C4 for even-chain carbon alkyl sulfates. The major metabolite for even-chained alkyl sulfates was identified as the 4-carbon compound, butyric acid 4-sulfate. The 4-butyrolactone has been found as a minor metabolite which is also formed after application of butyric acid 4-sulfate. Dog and human urine also contained one other minor metabolite, glycolic acid sulfate.
Metabolism of odd numbered chains (specifically, C11) in rats was postulated to follow a similar omega-, beta-degradation pathway: propionic acid-3-sulfate was the major urinary metabolite and pentanoic acid-5-sulfate and inorganic sulfate were minor metabolites.
The C2 fragments enter the C2 pool of the body and are either oxidized to CO2 or found in the body. In addition about 10 to 20% of the dose usually is eliminated as inorganic sulfate.

Any other information on results incl. tables

Table 1: Data availability for toxicokinetics, metabolism and distribution

Compound		Endpoints investigated
Test substance	Counter ion	Oral absorption	Distribution	Metabolism	Excretion
Alkyl sulfates
C10ASO4K CAS 7739-63-1	K			+	+
C11ASO4K CAS not available	K	+		+	+
C12ASO4K CAS 4706-78-9	K		+	+	+
C12ASO4Na CAS 151-21-3	Na			+	+
C16ASO4Na CAS 4706-78-9	K			+	+
C16ASO4Na CAS 1120-01-0	Na	+		+	+
C18ASO4Na CAS 1120-04-3	Na	+	+	+	+

Table 2: Metabolites formed from alkyl sulfates with even chain length*

HOOC-CH2-CH2-CH2-OSO3H	C4-H6-O2	HOOC-CH2OSO3H
butyric acid-4-sulfate	4-butyrolactone (ring structure)	Glycolic acid sulfate
Major Metabolite Found in rats, dogs, humans	Minor metabolite Found in rats, dogs, humans	Minor metabolite Found in dogs (and humans)

* investigated substances were potassium salts of C₁₀, C₁₂, C₁₄& C₁₈alkyl sulfates

Table 3: Influence of chain length on elimination of alkyl sulfates

Compound Shorthand	C10ASO4K CAS 7739-63-1		C11ASO4K CAS n.a.**		C12ASO4K CAS 4706-78-9		C18ASO4K CAS 7739-61-9
Number of animals, sex*	3 m	3 f	3 m	3 f	6 m	6 f	3 m	3 f
Recovery from urine at 48 h (% of dose)^*	82.9	79.5	98.2	90.6	86.3	93.2	77.1	73.9
Recovery from feces at 48 h (% of dose)^*	1.2	1.0	2.5	7.3	0.2	0.9	1.1	2.6
Recovery from carcass at 48 h (% of dose)^*	8.1	4.0	1.6	27.6	0.4	0.4	9.4	15.6

* mean number of number of animals indicated, all values are mean values; ** n.a. = not available; 5 mg/kg bw of the³⁵S labeled compounds was applied i.p. to MRC rats

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): no bioaccumulation potential based on study results
Alkylsulfates have a common metabolic fate that involves hydrolysis of the ether bond between the fatty alcohol and the sulfate chain.
Fatty alcohols, representing the variation in the structure of different alkylsulfates, are oxidized to the corresponding fatty acid and fed into physiological pathways like the citric acid cycle, sugar synthesis and lipid synthesis. The remaining sulfate chain is renal excreted.
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.

Executive summary:

The toxicokinetic behaviour of alkyl sulfates was assessed. Alkyl sulfates are well absorbed after ingestion. After absorption, these chemicals are distributed mainly to the liver. Alkyl sulfates are metabolized by cytochrome P450-dependent w-oxidation and subsequent beta-oxidation of the aliphatic fatty acids. End products of the oxidation are a C₄sulfate and a C₃or C₅sulfate. In addition, for the alkyl sulfates, sulfate is formed as a metabolite. The metabolites are rapidly excreted in urine. Due to the low concentrations of the substances in consumer products and the limited uptake after dermal exposure which is the main route for consumers, significant exposure of the developing foetus via the placenta or the neonate via the breast milk is not likely. Therefore a bioaccumulation of alkyl sulfates is not expected.