Sodium Metaphosphate

What Is It?

Sodium Metaphosphate, Sodium Trimetaphosphate and Sodium Hexametaphosphate are all sodium polyphosphates made of repeating units of NaPO3. Sodium Metaphosphate generally refers to a long chain of NaPO3 units that is not soluble in water, which is why it is sometimes called insoluble metaphosphate. Sodium Trimetaphosphate has three NaPO3 units, and Sodium Hexametaphosphate has six NaPO3 units. Both the Trimetaphosphate and the Hexametaphosphate are soluble in water. In cosmetics and personal care products, Sodium Metaphosphate, Sodium Trimetaphosphate and Sodium Hexametaphosphate are used in the formulation of makeup foundations, mascara, bath products, and moisturizing and skin care products.

Why Is It Used?

Sodium Metaphosphate, Trimetaphosphate and Hexametaphosphate inactivate metallic ions so as to prevent the deterioration of cosmetics and personal care products. Sodium Metaphosphate is also used to polish the teeth, reduce oral odor, or otherwise cleanse or deodorize the teeth and mouth. Sodium Trimetaphosphate minimizes the change in the pH of a solution when an acid or a base is added to the solution and Sodium Hexametaphosphate prevents the corrosion (rust) of metallic materials used in packaging cosmetics and personal care products.

Scientific Facts

Sodium Trimetaphosphate, and Hexametaphosphate are all inorganic salts that are often referred to as glassy sodium polyphosphates. Sodium Metaphosphate, in the form of long chains, is referred to as insoluble metaphosphate.

Safety Information

The Food and Drug Administration (FDA) includes Sodium Metaphosphate and Hexametaphosphate on its list of substances considered Generally Recognized As Safe (GRAS) for direct addition to food as sequestrants. Sodium Trimetaphosphate is permitted as a multipurpose additive in modified food starch not to exceed 0.04% residual phosphate. The safety of these three ingredients has been assessed by the Cosmetic Ingredient Review (CIR) Expert Panel. The CIR Expert Panel evaluated the scientific data and concluded that Sodium Metaphosphate, Sodium Trimetaphosphate and Sodium Hexametaphosphate were safe for use in cosmetics and personal care products when formulated to avoid skin irritation.

CIR Safety Review: The CIR Expert Panel noted that only Sodium Hexametaphosphate was reported to be used. Although the typical concentrations historically have been less than 1% for these ingredients, higher concentrations have been used in products such as bath oils, which are diluted during normal use. Pure Sodium Hexametaphosphate was a severe skin irritant, whereas a 0.2% solution was only mildly irritating. A similar pattern was seen with ocular toxicity. These ingredients were not genotoxic in bacterial systems nor were they carcinogenic.

No reproductive or developmental toxicity was seen after exposure to Sodium Hexametaphosphate or Sodium Trimetaphosphate. In clinical testing, irritation was observed as a function of concentration; concentrations as high as 1% produced no irritation in contact allergy patients.

The CIR Expert Panel concluded Sodium Metaphosphate, Sodium Trimetaphosphate and Sodium Hexametaphosphate were safe for use in cosmetic products when formulated to avoid skin irritation.

Link to FDA Code of Federal Regulations for Sodium Metaphosphate, Sodium Trimetaphosphate, and Sodium Hexametaphosphate

Sodium Metaphosphate, Trimetaphosphate, and Hexametaphosphate may be used in cosmetics and personal care products marketed in Europe according to the general provisions of the Cosmetics Regulation of the European Union.