What Should I Know about SLS?

Dear sorland7, Since the recent introduction of our improved Natural Dish Liquid formula we’ve received many inquiries about our choice to use the surfactant Sodium Lauryl Sulfate (SLS) and we want to help you understand how and why we made our decision. Many people have been influenced by anti-SLS campaigns and mistakenly believe that SLS is a dangerous ingredient.

For years we have used Sodium Lauryl Ether Sulfate (SLES) in our cleaning products - it is an effective surfactant with very good human health and environmental safety profiles. As a result of our pledge to consumers that we will eliminate 1,4 dioxane from our products, we started a search for an alternative naturally derived surfactant system to replace the surfactant system containing SLES, which can be a source of 1,4 dioxane contamination.

After exhaustive reviews of many ingredients, SLS emerged as the most authentic ingredient for three major reasons:

1. SLS has a long history of safe use in consumer products
   At Seventh Generation we pride ourselves on the strict standards we use for ingredient review and our review of SLS was conducted with typical rigor. So why does SLS receive such bad press? Why do so many websites caution against it? Much of the negative view of the ingredient can be traced back to misinterpretations of the scientific literature that were used in wide scale anti-SLS internet campaigns. The 4 false claims that are most often made about SLS are:
   
   
   1. SLS Causes Cancer: SLS is not classified by any regulatory agency or cancer authority as a carcinogen. In fact, the American Cancer Society has a page in its “Rumors, Myths, and Truths” section about SLS which clarifies that SLS does not cause cancer. The origin of this myth is likely to come from two sources. First, SLS is commonly used in laboratory research to process biological samples. The study that is often cited as proof that SLS is carcinogenic actually uses SLS to process the biological samples being studied, not as an experimental carcinogen [1]. Second, some sources have claimed that SLS can react with formaldehyde to produce carcinogenic nitrosamines. The problem with this argument is that nitrosamines contain two nitrogen atoms and neither SLS nor formaldehyde contains any nitrogen atoms, therefore the two cannot react to form a nitrogen containing nitrosamine. There is no scientific evidence to support the claim that SLS is a carcinogen.
      
      
   2. SLS Causes Blindness: Like the claim that SLS is a carcinogen, claims around severe eye damage, cataracts, and blindness are also the result of misinterpretations of scientific studies. The study that is most often cited shows that when an eye has a physically or chemically damaged cornea a large concentration of SLS will slow down the healing process, but this does not equate to causing blindness or damaging the eye [2]. Regarding cataracts, SLS can experimentally induce cataract formation when the lens of the eye is removed and immersed in a concentrated solution of SLS. However, the anatomy of the eye renders direct exposure to SLS impossible as the lens is deep within the eye and therefore not vulnerable to exposure through consumer product usage [3]. There is no evidence that products containing SLS can cause blindness, cataracts, or severe eye damage.
      
      
   3. SLS Causes Hair Loss: Several studies have shown that SLS can deposit on the root sheath of hair follicles [4, 5]. However, there has been no evidence that the presence of SLS on hair follicles is responsible for or contributes to hair loss.
      
      
   4. SLS Bioaccumulates and Causes Organ Damage: Extensive reviews of the absorption and excretion of SLS in humans and animals ultimately draw the conclusion that, while SLS can be absorbed through the skin, absorbed SLS is broken down by the liver and its break down products and intact SLS are excreted through the urine, feces, and exhaled carbon dioxide [5, 6]. There is no evidence that SLS can bioaccumulate or cause organ damage.
      
      
   Clearly, these claims are misleading, not scientifically supported, and extremely scary. As a result of our research we determined one undesirable feature of SLS: it has the potential to irritate the skin if not formulated correctly with other ingredients. We address this concern through proper formulation and skin safety testing. For our new Natural Dish Liquid formula we conducted lab tests for irritation and clinical tests with human subjects for irritation and allergy. These studies show that this product does not irritate the skin and is hypoallergenic.
   
   
2. SLS has a superior environmental profile to SLES. We are also committed to eliminating non-renewable carbon from our product line. SLS does not contain carbon molecules derived from petroleum. As a result, the renewable carbon index (RCI*) of plant-derived SLS is 100% which means that all of the carbons in the molecule are derived from a plant source rather than a petroleum source. Common replacements for SLS such as SLES and cocamidopropyl betaine contain carbon molecules derived from petroleum and have RCIs of around 76% and 55%, respectively. By transitioning the formula from an SLES based surfactant system to an SLS based surfactant system we have made our new Natural Dish Liquid formula more natural and are one step closer to eliminating non-renewable carbon from our product line.
   * Renewable Carbon Index: The percentage of carbon in the molecule or formula that is derived from a natural, renewable source such as coconut oil or palm kernel oil.
   
   
3. SLS is a high performance surfactant that provides excellent cleaning performance. While the human health and environmental safety profiles of products are of critical importance, the products have to work well too! SLS is a high performance surfactant that has excellent cleaning power: The SLS-based surfactant system in our new Natural Dish Liquid formula has actually improved the product’s cleaning performance by 53%.
   
   

To summarize, by transitioning from an SLES surfactant system to an SLS surfactant system in our new Natural Dish Liquid we have given you a more natural, high performance formula that meets the strict safety and authenticity requirements that you expect from Seventh Generation. But the prejudice against SLS continues. The anti-SLS movement is so strong that many natural companies opt against using SLS in their products and some natural retailers will not sell products that contain the ingredient. This is unfortunate given the petroleum savings that can be realized when choosing SLS over other surfactants, as well as the product performance and safety profile that can be achieved when formulating with SLS properly. Because we are committed to doing what we believe is right for human health and for the environment we plan to fully transition from SLES based surfactant systems to SLS based surfactant systems in our products.

References:

1. Birt DF, Lawson TA, Julius AD, Runice CE, Salmasi S. Inhibition by dietary selenium of colon cancer induced in the rat by bis(2-oxopropyl)nitrosamine. Cancer Research 1982;42(11):4455-59.
2. Green K, Johnson RE, Chapman JM, Nelson E, Cheeks L. Preservative effects on the healing rate of rabbit corneal epithelium. Lens & Eye Toxicity Research 1989;6(1-2):37-41.
3. Mandal K, Chakrabarti B, Thomson J, Siezen RJ. Structure and stability of gamma-crystallins. Denaturation and proteolysis behavior. Journal of Biological Chemistry 1987;262(17):8096-102.
4. Willis CM, Reiche L, Wilkinson JD. Immunocytochemical demonstration of reduced Cu,Zn-superoxide dismutase levels following topical application of dithranol and sodium lauryl sulphate: an indication of the role of oxidative stress in acute irritant contact dermatitis. European Journal of Dermatology 1998;8(1):8-12.
5. Final Report on the Safety Assessment of Sodium Lauryl Sulfate and Ammonium Lauryl Sulfate. International Journal of Toxicology 1983;2(7):127-81.
6. Madsen T, Boyd HB, Nylén D, Pedersen AR, Petersen GI, Simonsen F. Environmental and Health Assessment of Substances in Household Detergents and Cosmetic Detergent Products. Environmental Project No 615, Miljøprojekt. 2001;