LINEAR ALKYLBENZENE SULFONATE (LAS)

Linear Alkylbenzene Sulphonate (LAS) is the most widely used anionic surfactant in the world, primarily in laundry detergents and cleaning products. It was introduced in 1964 as the readily biodegradable replacement for highly branched alkylbenzene sulphonates (ABS).

  • Function and benefits

    What is its function and benefit?
    Surfactants are often referred to as the “engine” of the detergent system. They wet the fabrics and soils and so allow the removal of soils and dirt. They suspend a whole range of stains and dirt (particulate, greasy, body soils, cosmetics).

    The use of mixtures of anionic and nonionic surfactants in detergent formulators helps to achieve an optimum cleaning performance, through optimized surfactant 'packing' at the fabric interface, better anti-redeposition properties, water hardness tolerance through preventing the precipitation of insoluble calcium salts of anionics.

    How does it work?
    LAS or Linear Alkylbenzene Sulphonate (American spelling: sulfonate) is an anionic surfactant that lowers the surface tension of water, enabling soils and stains to loosen and release from fabrics and surfaces. LAS is the primary cleaning agent used in many liquid and powder laundry detergents and speciality household cleaners at concentrations up to 25 percent of the total formulation. (Ref: OECD SIDS)

  • Chemical structure and composition

    Linear Alkylbenzene Sulfonate

    (Ref: HERA)

    Chemical formula: CH3(CH2)11C6H4SO3H
    LAS is a non-volatile anionic surfactants with molecules characterized by a hydrophobic and a hydrophilic group. LAS are complex mixtures of homologues of different alkyl chain lengths (C10 to C13 or C14) and phenyl positional isomers of 2 to 5-phenyl in proportions dictated by the starting materials and reaction conditions, each containing an aromatic ring sulphonated at the para position and attached to a linear alkyl chain at any position with the exception of terminal one (1-phenyl). The properties of LAS differ in physical and chemical properties according to the alkyl chain length, resulting in formulations for various applications.
    It is distinguished from an earlier less biodegradable form of alkylbenzene sulfonate, termed ABS, by its linear (straight chain) structure, which provides its good biodegradation properties.
    Sodium dodecyl benzene sulphonate is the most important single type of LAS. (Ref: SDA Science)

  • Product / Category: where is it used?

    Most of LAS European consumption is in household detergents (>80%). Important application products are laundry powders, laundry liquids, dishwashing products and all purpose cleaners. The remainder of the LAS (<20%) is used in Industrial and Institutional (I&I) cleaners, textile processing as wetting, dispersing and cleaning agents, industrial processes as emulsifiers, polymerization and in the formulation of crop protection agents. (Ref: HERA)
    The most recent and realistic market survey was completed by the Ecosol companies (ECOSOL, 2005), which estimated a total consumption tonnage of about 430 kt for the year 2005, with a breakdown by household applications of about 350 k (Ref: HERA)
  • Ingredient safety and information

    AISE-CEFIC published a human and environmental risk assessment for LAS.
    LAS degrades rapidly aerobically (half-life in rivers i about 3 hours) (Ref: HERA) and is therefore completely biodegraded aerobically. It can be completely biodegraded anaerobically as well, but only if oxygen is available initially, to start the process. In conventional sewage treatment plants, more than 99% of LAS is removed. Where soil is fertilized with sewage sludge, LAS will biodegrade rapidly to the point of complete removal. No accumulation in soil and no bioaccumulation in plants could be detected experimentally (Ref: HERA).
    LAS toxicity data (EC50) to aquatic organisms range between 1 and 10 mg per litre in short term tests. LAS toxicity to fish and invertebrates is approximately equal, whereas toxicity to algae varies widely. LAS does not bioconcentrate in aquatic organisms because they are rapidly metabolized.
    The risk characterisation as expressed by the PEC/PNEC ratio was below 1 for all environmental compartments. It was concluded that the ecotoxicological parameters of LAS have been adequately and sufficiently characterized and that the ecological risk of LAS is judged to be low. (Ref: HERA)
    In view of the extensive database on toxic effects, the low exposure values calculated and the resulting large Margin of Exposure described above, it can be concluded that use of LAS in household laundry and cleaning products raises no safety concerns for the consumers. (Ref: HERA)
    Ingredient information sheet (PDF file)
    Visit also www.heraproject.com

  • References


    Some Publications by P&G Scientists

    • van de Plassche, E.J. et al., 1999, Predicted No-Effect Concentrations and Risk Characterization of Four Surfactants: Linear Alkyl Benzene Sulfonate, Alcohol Ethoxylates, Alcohol Ethoxylated Sulfates, and Soap. Environmental Toxicology and Chemistry, 18(11), pp.2653-2663.
    • Feijtel, T.C.J., Struijs, J., Matthijs, E., 1999, Exposure modeling of detergent surfactants—prediction of 90th-percentile concentrations in the Netherlands. Environmental Toxicology and Chemistry, 18, pp.2645–2652.
    • McAvoy, D.C. et al, 1998, Removal of Alcohol Ethoxylates, Alkyl Ethoxylate Sulfates, and Linear Alkylbenzene Sulfonates in Wastewater Treatment. Environmental Toxicology and Chemistry, 17(9), pp.1705-1711.
    • de Wolf, W. and Feijtel, T., 1998, Terrestrial Risk Assessment for Linear Alkyl Benzene Sulfonate (LAS) in Sludge-Amended Soils. Chemosphere, 36(6), pp.1319-1343.
    • Kloepper-Sams, P., Torfs, F., Feijtel, T. and Gooch, J., 1996, Effects assessments for surfactants in sludge-amended soils: a literature review and perspectives for terrestrial risk assessment. Science of The Total Environment, 185(1-3), pp.171-185.

Close
The Head Line
Close

Glossary

Illustrations from P&G's Science-in-the-Box website can be used freely for educational, non-commercial purposes provided that the source will be published as follows: "Obtained from www.scienceinthebox.com (P&G website)"

Print

Top of page
Top of page