General Description

Sodium lauryl ether sulphate (SLES) is a sodium salt produced through the ethoxylation of the sodium lauryl sulphate. This generates an ethoxylate, which is transformed into a half ester of sulphuric acid and neutralized to achieve SLES. The structure of SLES consists of a long hydrophobic chain of 12 carbon atoms (lauryl group), a sulfate group (-OSO3-), and an ethoxylated chain of variable length. SLES is among the most common anionic surfactants found in a wide range of commercial products for different purposes. SLES is an important ingredient in many personal care and household cleaning products due to its effective cleaning and foaming properties. 1

Structure and Properties

SLES is an anionic surfactant commonly used in personal care and household cleaning products. Its molecular structure consists of a long hydrophobic chain of 12 carbon atoms (lauryl group) and a hydrophilic sulfate group (-OSO3-) connected to an ethoxylated chain of variable length. The ethoxylated chain consists of multiple repeating units of alternating ethylene oxide (CH2CH2O) and propylene oxide (CH2CH(CH3)O) moieties, which contribute to the overall hydrophilicity of the molecule.

In aqueous solutions, SLES exhibits good solubility and stability due to its amphiphilic nature. The hydrophobic portion of the molecule aligns with nonpolar substances such as oils and grease, while the hydrophilic sulfate group interacts with water molecules. This enables SLES to form micelles that can emulsify and suspend grease, dirt, and other particles in water, allowing for efficient removal during cleaning.

Hazard

sodium laureth sulfate may be contaminated with measurable amounts of ethylene oxide and 1,4-dioxane. The International Agency for Research on Cancer ethylene oxide as a known human carcinogen and 1,4-dioxane as a possible human carcinogen. Ethylene oxide can also harm the nervous system and the California Environmental Protection Agency has classified it as a possible developmental toxicant based on evidence that it may interfere with human development. 1,4-dioxane is also persistent. In other words, it doesn’t easily degrade and can remain in the environment long after it is rinsed down the shower drain. 1,4-dioxane can be removed from cosmetics during the manufacturing process by vacuum stripping, but there is no easy way for consumers to know whether products containing sodium laureth sulfate have undergone this process. The industry panel that reviews the safety of cosmetics ingredients notes that sodium laureth sulfate can irritate the skin and eyes (though approving of its use in cosmetics).

Side Effects

Sodium lauryl ether sulfate(SLES) can irritate eyes, skin, and lungs, especially with long-term use. It may also be contaminated with a substance called 1,4-dioxane, which is known to cause cancer in laboratory animals. This contamination occurs during the manufacturing process.