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Ammonium lauryl sulfate
Ammonium Lauryl Sulfate (ALS) is the common name for ammonium dodecyl sulfate (CH3(CH2)10CH2OSO3NH4). The dodecyl signifies the presence of a 12-member carbon chain in the molecular backbone which allows the molecule to bond with non-polar portions of molecules while the highly polar sulfate head allows the molecule to bond with polar molecules such as water. ALS is classified as an alkyl sulfate and is an anionic surfactant found primarily in shampoos and body-wash as a foaming agent. Lauryl sulfates are very high-foam surfactants that disrupt the surface tension of water by forming micelles around the polar water molecules.
Additional recommended knowledge
Action in solution
Ammonium lauryl sulfate, like any other surfactant, makes a good base for cleansers because of the way it disrupts the hydrogen bonding in water. Hydrogen bonding is the primary contributor to the high surface tension of water. In solution, the lauryl sulfate anions and the ammonium cations separate. The former align themselves into what is known as a micelle, in which the ions form a sphere, with the polar heads (the sulfate) on the surface of the sphere and the nonpolar hydrophobic tails pointing inwards towards the center. The water molecules around the micelle arrange themselves around the polar heads, but this disrupts their hydrogen bonding with the water surrounding them. The overall effect of having these micelles in an aqueous (water) environment is that the water becomes more able to penetrate things like cloth fibers or hair, and also becomes more readily available to solvate anything coming off the aforementioned substance.
In high concentrations this molecule may cause severe irritation to eyes and skin. Inhalation may cause irritation to the respiratory system. Ingestion may cause irritation, nausea or diarrhea.
In a 1983 report by the Cosmetic Ingredient Review, shampoos containing up to 31% ALS registered 6 health complaints out of 6.8 million units sold. These complaints included two of scalp itch, two allergic reactions, one hair damage and one complaint of eye irritation.
The CIR report concluded that both sodium and ammonium lauryl sulfate “appear to be safe in formulations designed for discontinuous, brief use followed by thorough rinsing from the surface of the skin. In products intended for prolonged use, concentrations should not exceed 1%.”
The Human and Environmental Risk Assessment (HERA) project performed a thorough investigation of all alkyl sulfates, as such the results they found apply directly to ALS. Most alkyl sulfates exhibit low acute oral toxicity, no toxicity through exposure to the skin, concentration dependent skin irritation, and concentration dependent eye-irritation. They do not sensitize the skin and did not appear to be carcinogenic in a two year study on rats. The report found that longer carbon chains (16-18) were less irritating to the skin than chains of 12-15 carbons in length. In addition, concentrations below 1% were essentially non-irritating while concentrations greater than 10% produced moderate to strong irritation of the skin.
The HERA project also conducted an environmental review of alkyl sulfates that found all alkyl sulfates are readily biodegradable and standard wastewater treatment operations removed 96-99.96% of short-chain (12-14 carbons) alkyl sulfates. Even in anaerobic conditions at least 80% of the original volume is biodegraded after 15 days with 90% degradation after 4 weeks.
The CDC has reported on occupations which were routinely exposed to ALS between 1981 and 1983 during this time the occupation with the highest number of workers exposed was registered nurses followed closely by funeral directors.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Ammonium_lauryl_sulfate". A list of authors is available in Wikipedia.|