E173 – properties, uses, pros, cons, safety and alternatives

Description

E173 (CI 77000) is a metallic pigment based on aluminium, used as a white/metallic colorant in cosmetic and industrial applications. It is also known as Aluminum Powder or Pigment Metal 1.
In the European food context it is classified as the additive E173, with restricted and specifically regulated uses.

The pigment is valued for its reflective properties and bright metallic effect, but it raises relevant safety and toxicological concerns, especially in the case of repeated or prolonged exposure.

Chemical composition and structure

E173 consists predominantly of metallic aluminium in a finely divided powder form. Its structure is that of an elemental metal, without complex molecular bonds, with a high surface area due to its fine particle size.

Main raw materials

• Aluminium
  A light, malleable metal characterized by high reflectivity and surface corrosion resistance.
  From a biological perspective, aluminium is considered non-essential to the human body and potentially toxic if absorbed.

 Aluminum is known for its reflective properties and resistance to corrosion, but it is also known to be dangerous when it enters the human body. Link below:

https://www.tiiips.com/m/tiiips/home?action=viewObject&oID=25256

• Acids and chemical reagents
  Used during manufacturing for surface treatments, improving adhesion, stability, and compatibility of the pigment in finished formulations.

Industrial synthesis of CI 77000

The manufacturing process follows standardized industrial steps:

• Production of aluminium powder
  Aluminium metal is converted into powder through controlled milling or atomization.

• Chemical treatment
  The powder is treated with acids or other reagents to improve oxidation resistance, adhesion, and stability.

• Purification
  Removal of impurities to ensure consistent quality and compliance with application standards.

• Quality control and packaging
  Verification of particle size, purity, and safety prior to packaging for cosmetics, paints, coatings, and other industrial uses.

What it is used for and where it is used

Cosmetics

• Used as a metallic colorant to provide shine and reflective highlights in products such as:

  • eyeshadows

  • nail polishes

  • decorative make-up

Cosmetic Safety

Restricted cosmetic ingredient as IV / 117  a Relevant Item in the Annexes of the European Cosmetics Regulation (EU) 2023/1545. Substance or ingredient reported: Aluminium. Wording of conditions of use and warnings    Purity criteria as set out in Commission Directive 95/45/EC (E 173)

Cosmetic assessment
From a formulation standpoint, it is an aesthetic ingredient, not a skin-benefit active. For this reason it is often regarded as a colorant to avoid, particularly in products with prolonged contact with skin and mucous membranes.

Pros and cons

Safety

Aluminium may interfere with several biological processes, including:

• cellular oxidative stress

• calcium metabolism

• mitochondrial function

The nervous system is considered one of the primary targets of aluminium toxicity.
Chronic or cumulative exposure may increase the risk of undesirable effects, which is why cosmetic use is controversial and subject to regulatory restrictions.

Regulatory identification

• CAS: 7429-90-5

• Chemical name: Aluminium

• Molecular formula: Al

• EC number: 231-072-3

• UNII: KZJ3T010RQ

• DTXSID: 3040273

Alternatives