Sulfonic acids, C6-8-alkane, sodium salts

Endpoint summary

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - oral (%):

100

Absorption rate - dermal (%):

1

Absorption rate - inhalation (%):

100

Additional information

The anionic surfactants category

The anionic surfactants (ANS) category includes three structurally related classes of substances: Alkyl sulfates, which are sulfate salts consisting of a predominantly linear alkyl chain bearing a terminal sulfate ester anion, neutralised with a base (single chain length or a defined chain length distribution); primary alkane sulfonates, the salt of a linear saturated alkyl chain, bearing a terminal sulfonate anion, neutralized with sodium hydroxide; and alpha-olefin sulfonates, a mixture of sodium alkene sulfonate and hydroxyl alkane sulfonate salts, with the sulfonate group in the terminal position and the double bond, or hydroxyl group, located at various positions along a linear aliphatic chain in the vicinity of the sulfonate group.

The most important common structural feature of the category members is the presence of a predominantly linear aliphatic hydrocarbon chain with a polar sulfate or sulfonate group, neutralized with a counter ion. The hydrophobic hydrocarbon chain and the polar sulfate or sulfonate groups confer surfactant properties and enable the commercial use of these substances as anionic surfactants. Common physical and/or biological pathways result in structurally similar breakdown products and are, together with the surfactant properties, responsible for the essentially identical hazard profiles with regard to human health.

The toxicological properties of the ANS category were assessed under the high production volume (HPV) chemicals program of the Organisation for Economic Cooperation and Development (OECD) in 2007 at the OECD SIDS Initial Assessment Meeting (SIAM) 25 using a category approach (a grouped approach, in which data for individual members are presented and discussed together as part of a category, rather than substance-by-substance). In total, 61 anionic surfactants were assessed: 46 alkyl sulfates, 6 primary alkane sulfonates (including 1-Octanesulfonic acid, sodium salt), and 9 alpha-olefin sulfonates. For the ANS category members, a comprehensive data set was collected from many sources, which is fully described in the peer-reviewed Screening Information Dataset (SIDS) documentation and discussed in the SIDS Initial Assessment Report (SIAR) [OECD, 2007]. For those members of the category where reliable data were not available for all obligatory endpoints required according to the Manual for Investigation of HPV Chemicals, read across of toxicological data from closely related chemicals of the category was applied to address their properties.

Toxicokinetics, metabolism and distribution

There are several studies available for members of the ANS category (see table below). 

The data for experimental animals as well as studies with human volunteers demonstrate that the alkyl sulfates, alkane sulfonates and alpha-olefin sulfonates are well absorbed after oral uptake, as up to 98% of the applied doses were excreted rapidly via urine [Denner et al. (1969); Burke et al. (1975, 1976); Merits (1975); Taylor et al. (1978); Black & Howes (1980); Inoue et al. (1982)]. Hence, oral absorption is assumed to be 100%.

On the other hand, the penetration through intact skin with < 1% of the applied doses is poor [Howes (1975); Prottey & Ferguson (1975); Minegishi et al. (1977); Black & Howes (1980)]. Based on the experimental data, a default assumption of 1% dermal absorption was taken for deriving the DNEL. Since dermal absorption decreases with increasing concentration of a solution, this percentage can also be used for workers as a worst case approach.

After absorption, these chemicals are distributed mainly to the liver (Denner et al. (1969); Burke et al. (1975, 1976); Merits (1975); Taylor et al. (1978); Inoue et al. (1982)] and the alkyl sulfates, alkane sulfonates and most probably also alpha-olefin sulfonates are metabolized by cytochrome P450-dependent omega-oxidation and subsequent beta-oxidation of the aliphatic fatty acids. End products of the oxidation are a C4 sulfate or sulfonate (even numbered chain lengths) and a C3 or C5 sulfate or sulfonate (odd numbered chain lengths). For the alkyl sulfates, sulfate is also formed as a metabolite (Denner et al. (1969); Ottery et al. (1970); Burke et al. (1975, 1976); Merits (1975); Taylor et al. (1978); Greb & Wingen (1980); Black & Howes (1980); Inoue et al. (1982)]. Several reasons for a lack of concern regarding bioaccumulation exist including rapid excretion of metabolites via urine, limited dermal exposure (main route of consumer exposure) and the low concentration of substances in consumer products.

Summary of toxicokinetic metabolism and distribution studies

	Data availability (chain lengths, counter ions) and results for sub-category
	ASO4	ASO3	A=/OHSO3
Metabolism and excretion	C10, C11, C12, C16, C18 Na, K,TEA	C12, C16 Na	C14
Excretion in urine	C12 (complete within 6h) C10, 11, 16, 18 (mainly within 48 h)	C12, C16 (not complete within 6h)	C14 (not complete within 24h)
Amounts excreted in urine (% of dose in 48 h)	C10–18 74–98% (5mg/kg, oral)	C12: 87–96% (5mg/kg oral) C16: 48–65% (5 mg/kg oral)	C14: 72% (100mg/kg oral,5days)
Amounts excreted in faeces (% of dose in 48 h)	C12: negligible C11, 18: <10% as metabolites	C12: <10% unabsorbed C16: 40% unabsorbed	C14: 22% (mainly unabsorbed, 5 days)
Main metabolites	Even chain numbers: Butyric acid 4-sulfate odd chain number: Propionic acid-3 sulfate, pentanoic acid-5-sulfate Sulfate	Even chain number: Butyric acid 4-sulfonate Odd chain number: not investigated No Sulfate	No data
Distribution	C10, C12, C18 K Whole body autoradiography after i.p. application Liver, kidney	C12, C16 Na Whole body autoradiography after i.p. application Liver, kidney	C14 Na radioactivity in organs after oral application, gastrointestinal tract, liver, kidney
References	Burke et al. (1975, 1976) Denner et al. (1969) Blank & Gould (1961) Howes (1975) Prottey & Ferguson (1975) Merits (1975) Burke et al. (1975)	Prottey & Ferguson (1975) Taylor et al. (1978)	Inoue et al. (1982) Minegishi et al. (1977)

 

References

Black GJ, Howes D (1980) Absorption, metabolism, and excretion of anionic surfactants. In: Gloxhuber C (Ed.), Surfactant Science Series, vol. 10: Anionic Surfactants—Biochemistry, Toxicology, Dermatology. Dekker, New York, pp. 51–85.

Burke B, Olavesen AH, Curtis CG, Powell GM (1975) The biodegradation of some anionic detergents in the rat. A common metabolic pathway. Xenobiotica 5, 573–584.

Burke B, Olavesen AH, Curtis CG, Powell GM (1976) The biodegradation of the surfactant undecyl sulphate. Xenobiotica 6, 667–678.

Denner WHB, Olavesen AH, Powell GM, Dodgson KS (1969) The metabolism of potassium dodecyl [35-S]sulphate in the rat. Biochem. J. 111, 43–51.

Howes D (1975).. The percutaneous absorption of some anionic surfactants. J. Soc. Cosmet. Chem. 26, 47–63.

Inoue S, O’Grodnick JS, Tomizawa S (1982) Metabolism of alpha-olefin sulfonate (AOS) in rats. Fundam. Appl. Toxicol. 2, 130–138.

Merits I (1975) The metabolism of labelled hexadecyl sulphate salts in the rat, dog and human. Biochem. J. 148, 219–225.

Minegishi K-I, Osawa M, Yamaha T (1977) Percutaneous absorption of alpha-olefin sulfonate (AOS) in rats. Chem. Pharm. Bull. (Tokyo) 25, 821–825.

OECD (2007) Category of Alkyl sulfates, Alkane sulfonates and a-Olefin sulfonates. SIDS Initial Assessment Report for SIAM 25, Organization for Economic Cooperation and Development, Paris. OECD Integrated HPV database online at /http://cs3-hq.oecd.org/scripts/hpvS.

Prottey C, Ferguson TF (1975) Factors which determine the skin irritation potential of soaps and detergents. J. Soc. Cosmet. Chem. 26, 29–46.

Taylor AJ, Olavesen AH, Black JG, Howes D (1978) The metabolism of the surfactants dodecyl sulfonate and hexadecyl sulfonate in the rat. Toxicol. Appl. Pharmacol. 45, 105–117.

Wibbertmann A, Mangelsdorf I, Gamon K, Sedlak R (2011) Toxicological properties and risk assessment of the anionic surfactants category: Alkyl sulfates, primary alkane sulfonates, and alpha-olefin sulfonates, Ecotoxicology and Environmental Safety, 74, 1089–1106