The 50% rule - Are nano-free sunscreens really free of nanoparticles?

In this article, we explain the definition of nano-free sunscreens according to EU regulations, as well as the benefits and potential dangers of nanoparticles for our health and our environment. You will find out whether nanoparticles are also permitted in certified natural cosmetics and whether a sunscreen with 49% nanoparticles is actually considered "non-nano" according to the current EU definition.

What are UV nanoparticles?

Nanoparticles (from the ancient Greek: nanos = dwarf) are extremely small particles whose size is between 1 and 100 nanometers. Mineral sunscreens often contain nanoparticles made of zinc oxide (ZnO) and titanium dioxide (TiO₂). Mineral particles reflect UV rays directly before they can penetrate the skin. They offer broad-spectrum protection and do not disintegrate under sunlight, so they are photostable. Chemical UV filters such as avobenzone, oxybenzone, octocrylene or ethylhexyl methoxycinnamate can also be used in nano size to increase their stability and effectiveness and improve absorption through the skin.

What are the benefits of nanoparticles in new generation sunscreens?

• Cosmetic properties: Since mineral nanoparticles are significantly smaller, they have an almost transparent appearance when applied and do not leave any visible white residue on the skin, as is the case with larger particles. While larger mineral particles more or less seal the skin and make it difficult for the skin to sweat, the skin feel much lighter and more pleasant with creams containing nanoparticles.
• Stability: Nanoparticles spread better in a sunscreen than larger particles. They are less likely to settle and stabilize the texture of a cream.

What potential dangers do UV nanoparticles pose?

• Uncertainties regarding the long-term health consequences: There are repeated warnings that nanoparticles can penetrate the body through the skin and have toxic effects there. In animal experiments, researchers have observed that nanoparticles can cause inflammation, organ damage and tumors in the bodies of mice and rats (EJ Evans, et al., "Titanium dioxide nanoparticles: a review of current toxicological data," Journal of Applied Toxicology, 2019). However, the study situation is not yet clear. Many experts consider the risk to be low as long as the skin barrier is intact. A labeling requirement from the first nanoparticle would make it easier for researchers and consumers to better monitor potential exposure in the long term and identify risks at an early stage.
• Environmental pollution from nanowaste: Nanoparticles can enter the environment via sunscreens when bathing, settle and damage aquatic ecosystems such as coral reefs. According to EU chemicals law (REACH), nano-zinc oxide must not enter the environment; it is considered very toxic to aquatic organisms, with acute and long-term effects (water hazard class 2, hazard phrase H 410).

UV nanoparticles and the 50% rule

Conventional sunscreens, but also natural cosmetic sunscreens, can contain nanoparticles. If the nanoparticle content is more than 50% of the total UV filter particles used, this must be declared as "nano" according to the EU definition of nanomaterials. However, if the proportion of mineral or chemical nanoparticles is less than 50%, the product does not have to be declared as "nano" (see Official Journal of the European Union, Recommendation for a Definition of Nanomaterials of October 18, 2011, revised on June 10, 2022).

This means that it is not possible to tell from the list of ingredients (INCI list) whether a product is actually 100% free of nano particles. Natural cosmetics standards also allow the use of UV nano filters below 50% without the need for additional labeling as "nano" on the label - in accordance with the 50% rule according to EU guidelines.

UV filters and the body's own vitamin D production

Chemical and mineral UV sunscreen filters hinder the body's own production of vitamin D. This vitamin in its active form, calcitriol, supports the incorporation of calcium into our bone tissue, it has a significant influence on the function of the thyroid gland and it strengthens our immune system. Even a chemical or mineral SPF 20 blocks 95-99% of the body's own vitamin D production. A deficiency in this vital vitamin is one of the biggest health problems of our time. Studies show that vitamin D not only improves our protection against colds and depression, but also against diabetes, colon cancer, osteoporosis and heart attacks.

Conclusion

Mineral nanoparticles in new generation sunscreens offer effective UV protection and at the same time improve the transparency of a cream on the skin. However, the EU's 50% rule for defining nano products poses a problem for consumer safety and transparency. Clear labeling would help to raise awareness of the risks and enable consumers to make an informed purchasing decision. The potential health and environmental hazards of nanoparticles must be taken into account in order to ensure long-term safety.