Common Eco-Myth: Sodium Lauryl Sulfate (SLS) Causes Cancer
Companies have often gone to great lengths to exploit widely held consumer beliefs, however misguided, and translate them into higher profit margins. In recent years, we have seen efforts by firms operating in a variety of industries, ranging from the food industry (see latest non-fat/vitamin enriched/sugar-free/etc fad) to the cookware industry (see a recent post on the Teflon pan/PFOA exposure myth here), to capitalize on some of these misperceptions by airing and marketing them.
One such misperception that has managed to persist in the public domain over the last few years is the perceived carcinogenic risk posed by sodium lauryl sulfate, a chemical commonly found in beauty care products. Despite strong evidence to the contrary, including an article published by the American Cancer Society definitively positing no link between SLS and cancer, this urban legend remains ingrained in many consumers' minds. We decided to go on our own little fact-finding expedition to get to the bottom of this widely-held myth.Part of the confusion likely arises from the fact that sodium lauryl sulfate is in fact frequently implicated in cancer experiments. However, it is always used to solubilize chemicals prior to being injected into test animals and never as the active ingredient. No evidence in the literature has ever been found directly linking SLS to cancer.
SLS is a coarse powder that is often used as a foaming agent or detergent in soaps. It is created by joining sulfate and lauric acid, two compounds widely found in nature. According to Dr. Ed Friedlander, SLS' properties as a skin and eye irritant make it an ideal model for skin contact dermatitis. Indeed, a recent search of the literature using the National Center for Biotechnology Information (NCBI) search engine PubMed found most SLS citations in articles published in dermatology journals like Contact Dermatitis.
One dubious claim often made by the dozens of anti-SLS websites is that sodium lauryl sulfate is carcinogenic because it produces nitrosamines when it reacts with formaldehyde. Since neither compound contains a nitrogen atom, however, that is chemically impossible.
Despite the fact that there was and still is no hard evidence to back up the link between SLS and cancer, many unscrupulous companies took advantage of the suspicions and allegations raised by such websites to market as many "SLS-free" products as they could, often selling them to major organic/natural stores like Whole Foods and Wild Oats, thus helping to further legitimize this myth. Although many of these body care products contained far more harmful chemicals such as parabens and ethanolamines (which do contain nitrosamines), the sole scapegoating of SLS allowed these companies to safely continue using them without arousing much public scrutiny.
David Bronner, President of Dr. Bronner's Magic Soaps, has long felt that SLS has been unfairly scapegoated in the beauty care industry. "We do feel that SLS has been incorrectly scapegoated, as a lightning rod for legitimate consumer concerns about cosmetic ingredient safety ... the issue with SLS primarily has to do with it being irritating to skin, which can be addressed by buffering with ingredients like Coco Glucoside," he said, stating that his company doesn't use it in any of its personal care products (though it does use it in one of its cleaning products).
He argues that those chemicals that do pose potential health effects have largely been ignored.
"Ethoxylated ingredients in personal care, including SLES, Sodium Myreth Sulfate, PEG ingredients, etc., are a problem due to 1,4 dioxane contamination. The dioxane can be vacuum stripped to less than 10 ppm levels, but especially with personal care products, the cumulative effect of constant low-level exposure from different dioxane containing products is unknown ... Other ingredients of concern in cosmetics are formaldehyde donor preservatives, parabens, nitrosamine containing ingredients like ethanolamines (any ingredients with MEA, DEA or TEA)."
The easiest way to get rid of all these potential health risks would simply be to formulate away from ingredients that involve petrochemicals, a point he recently emphasized in a video criticizing companies for incorrectly claiming to be "natural" brands.
As always, we recommend you do your own research if you're still not fully convinced and ask the manufacturers of the beauty care products you use for their policies on SLS (most should have it on their websites). Also feel free to check out our "how to" guide on women's personal care for more tips and don't be shy about weighing in with your own opinion.
See also: ::Movie Review: Dr. Bronner's Magic Soapbox, ::Common Eco-Myth: Wind Turbines Kill Birds, ::TreeHuggers Show Some Skin for Bert, Juice, NOW, & Avalon, ::The Greater Good: Burt's Bees Campaign for Truly Natural Personal Care, ::domino & TreeHugger's Green List: Beauty