Are SLES and SLS linked to cancer？

Sodium lauryl sulfate (SLS) is a chemical you’ll probably spot in the ingredients list of your shampoo, shower gel, toothpaste or bubble bath; you might also spot sodium laureth sulfate (SLES), which is commonly used as an alternative, and which has very similar properties. These compounds are the reason your shampoo (or other toiletry of choice) foams, due to their chemical characteristics.

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Both SLS and SLES are what are known as ‘surfactants’ in chemistry, and both can be derived from coconut oil. Surfactants are usually organic molecules that have a hydrophobic (water-hating) end, and a hydrophilic (water-loving) end. These surfactants can lower the surface tension of water, reducing the amount of work needed to create the foam and increasing the stability of the bubbles that are within it. Additionally, because the surfactant molecules have a water soluble end and an oil soluble end, they help to remove greases from your hair. They can organise themselves with the hydrophobic ends of the molecule trapping the oil, allow it to be suspended in the water due to the presence of the hydrophilic ends of the surfactant molecules, then rinsing it away.

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These days it seems that any chemical found in everyday products, is being demonised and linked with cancer. SLS is a mild irritant. SLS has absolutely no links with cancer – it’s just going to make your eyes sting a bit, and certainly won’t kill you (unless you can stomach swallowing about 7.5kg of toothpaste).

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SLES itself isn’t carcinogenic. It’s made via a process called ethoxylation, and the sulfation of the ethoxylated alcohol produces another chemical as a byproduct, 1,4-dioxane, which is a confirmed carcinogen in animals at high concentrations, and a suspected (but unconfirmed) carcinogen in humans. So, why are we still routinely using SLES in our shampoo? Firstly, research has stated that skin absorption due to dermal exposure to products containing 1,4-dioxane is very low; this study gives a figure of 3.2%. Additionally, it doesn’t bioaccumulate a great deal (build up in the body over a long time), even if it is absorbed, as it’s removed from the body quite easily. In shampoo, it generally isn’t found in levels above 140 parts per million, and in most is much lower. At these levels it isn’t considered to be a health risk by regulatory bodies. You aren’t going to absorb enough 1,4-dioxane from shampoo to reach the dangerous levels found in animal studies, even using it on a daily basis.

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Getting back to SLS,other uses for SLS include industrial uses in engine degreasers and floor cleaners. It’s also present in some pesticides, although is commonly classified as an inert substance in these. Amusingly, it’s also been investigated as a potential shark repellent. It was tested on a variety of sharks in this study, which found that it did produce a repellent response, although not at a low enough concentration for it to be useful as a ‘cloud repellent’. The study does, however, suggest that it could still be useful as a directional repellent with ‘squirt application’.

By https://www.compoundchem.com/