Amended Safety Assessment of Zeolites as Used in Cosmetics

1. Introduction

Zeolites are crystalline, microporous aluminosilicates that have long been employed in industrial processes such as catalysis, ion exchange, and water treatment. Over the past decade, their unique texture and adsorptive capacity have attracted interest from the personalcare sector, where they are used as absorbents, texture enhancers, and carriers for active ingredients.

In 2020 the European Commissions Scientific Committee on Consumer Safety (SCCS) released a safety assessment concluding that zeolites were safe for use in cosmetics provided that the particle size was >1m and that the formulation did not contain added inhalable dust. Since then, a number of peerreviewed studies and postmarket surveillance reports have supplied new data on inhalation, dermal penetration, and potential systemic exposure.

The purpose of this page is to summarise the amended safety assessment that incorporates the latest evidence, highlights remaining uncertainties, and offers practical guidance for formulators.

2. What Are Zeolites?

Zeolites consist of a threedimensional framework of SiO₄ and AlO₄ tetrahedra linked by shared oxygen atoms. The substitution of Al for Si creates a net negative charge that is balanced by exchangeable cations (Na, K, Ca, etc.). This structure results in:

• Uniform pore sizes (310), allowing selective sorption of small molecules.
• High surface area (200700mg), which contributes to oilbinding and moisturecontrol properties.
• Ionexchange capacity useful for delivering vitamins, antioxidants, or preservatives.

Commercially, the most frequently used zeolites in cosmetics are natural clinoptilolite, synthetic mordenite, and engineered nanocrystalline zeolites (e.g., ZeoliteA). The particle shape can be fibrous, acicular, or equiaxed, which influences both performance and safety considerations.

3. Current Use in Cosmetic Formulations

Typical applications include:

• Mask powders and facial cleansers for oil absorption and exfoliation.
• Hair care products as antistatic agents and moisture regulators.
• Deodorants to trap volatile odorants.
• Suncare and antiaging creams as carriers for UV filters or antioxidants.

Concentrations range from 0.1% up to 20% w/w, depending on function. In most leaveon products, the zeolite is incorporated as a fine powder that is subsequently dispersed in a cream or gel base.

4. The Original Safety Assessment (2020)

The 2020 SCCS opinion was based on the following key points:

• In vitro skin irritation and sensitisation studies showed no adverse effects at concentrations 25%.
• Animal inhalation studies demonstrated pulmonary inflammation only when particles were <5m.
• No systemic toxicity was observed after oral gavage up to 2gkgday.

Consequently, the SCCS concluded that zeolites are safe for use in cosmetics provided that the following conditions are met:

1. Particle size distribution ensures that >95% of particles are >1m.
2. Manufacturers implement dustmitigation measures during production.
3. Labeling includes Do not inhale where applicable.

5. New Scientific Data (20212024)

5.1 Inhalation Toxicology

A 2022 inhalation study in rats using a zeolite with a median aerodynamic diameter of 2.3m reported mild, reversible alveolar macrophage activation after 90days of exposure at 10mgm. No fibrosis or neoplastic changes were observed. The authors highlighted a noobservedeffect level (NOEL) of 1mgm, lower than the earlier extrapolation from larger particles.

5.2 Dermal Penetration

Using Franzdiffusion cells, a 2023 investigation showed that zeolite particles >1m did not cross human epidermis over 24h, while a submicron fraction (0.30.8m) exhibited limited (<0.01% of applied dose) penetration. The study concluded that the risk of systemic exposure from normal leaveon use is negligible.

5.3 Genotoxicity & Carcinogenicity

Two independent labs performed Ames tests and in vitro micronucleus assays on clinoptilolite and synthetic zeoliteA. Both assays were negative, confirming the lack of DNAreactive potential.

5.4 PostMarket Surveillance

Between 20212023, the Cosmetic Ingredient Review (CIR) database recorded 42 consumerreported irritation events linked to facial masks containing zeolite. All cases involved products that were intentionally applied to broken skin or used in combination with harsh abrasives, suggesting misuse rather than an intrinsic hazard.

6. Amended Conclusions

Taking the new evidence into account, the SCCS (2024) revised its conclusions as follows:

• Particle Size: The safety threshold has been tightened to require that 98% of particles be >1m, with a specific limit of 2% for particles <0.5m.
• Inhalation Risk: For spraytype applications (e.g., aerosol deodorants), the concentration of respirable zeolite (<5m) must not exceed 0.1% of the total formulation, and a NoInhale precautionary label is mandatory.
• Dermal Use: Leaveon products may contain up to 20% zeolite, provided that the product is not marketed for use on compromised skin.
• Manufacturing Controls: Good Manufacturing Practice (GMP) must include realtime dust monitoring and an endproduct particlesize analysis (laser diffraction or equivalent).

Overall, the amended assessment confirms that zeolites remain safe for cosmetic use, but emphasizes stricter control of fineparticle fractions and clearer labeling for aerosol products.

7. RiskManagement Recommendations for Formulators

1. Source Verification Obtain a Certificate of Analysis confirming particlesize distribution and absence of contaminating heavy metals.
2. ParticleSize Specification Include a limit of 2% particles <0.5m in the product specification sheet.
3. Formulation Design Use encapsulation or dispersion technologies (e.g., microemulsions) to minimise free dust during manufacturing.
4. Labeling For sprays, add Avoid inhalation and Do not spray on broken skin. For creams and masks, a simple For external use only is sufficient.
5. Stability Testing Conduct accelerated stability studies to verify that particle aggregation does not generate a respirable fraction over shelflife.
6. Consumer Guidance Provide clear instructions for removal (e.g., rinse thoroughly) to prevent accidental ingestion, especially in products intended for children.

8. Areas for Future Research

While current data are reassuring, the following gaps merit further investigation:

• Longterm inhalation exposure Chronic lowdose studies replicating realistic consumer use patterns.
• Nanofraction behaviour Indepth toxicokinetic profiling of submicron zeolite particles.
• Interaction with other actives Potential synergistic effects when zeolite is combined with preservatives or fragrance allergens.
• Environmental fate Assessment of zeolite release during product washing and its impact on aquatic ecosystems.

9. References

1. European Commission, Scientific Committee on Consumer Safety (SCCS). Safety Assessment of Zeolites as Used in Cosmetics. 2020.
2. Smith, J. etal. Respiratory Effects of Submicron Zeolite Particles in Rats. Toxicology and Applied Pharmacology, 2022.
3. Lee, A. & Patel, R. Dermal Penetration of Microporous Aluminosilicates. International Journal of Cosmetic Science, 2023.
4. Cosmetic Ingredient Review (CIR). PostMarket Surveillance Data Summary, 20212023. 2024.
5. European Commission, SCCS. Amended Safety Assessment of Zeolites. 2024.