Characteristics of Titanium Dioxide and its harmlessness

Sunscreens and cosmetics: nano or microparticles?

In a recent article we have already dealt with sunscreens. We have highlighted how solar radiation can damage our skin.

In fact, the energy transmitted by the UV rays causes the formation of free radicals thatreact in turn with the molecules of the cellular structures, degrading them and making them, at the very least, less functional.

This leads, over time, to degenerative processes such as skin ageing (spots and wrinkles) and the development of skin tumours.

We have placed the emphasis on the sun protection factor (SPF) and how important it is to daily use cosmetics that offer a certain degree of protection from UV rays.

In this article we will talk again about sunscreens and their composition, because they are not all the same.

Some contain chemical filters (cinnamates, triazine and mexoryl), ie substances that interact chemically with the sun’s rays, absorbing their impact.

The best sunscreens are based on physical filters (zinc oxide and titanium dioxide), ie white powders that absorb and reflect light. The physical filters therefore also act upstream: they prevent UV rays from reaching the surface of the skin.

Solar cosmetics based on titanium dioxide give excellent protection not only against UV rays but also against visible light (400-800 nm) and infrared rays (heat).

This is very important because even exposure to visible light and infrared leads to the formation of free radicals and skin damage. For those with sensitive skin prone to blotches and acne rosacea it is essential to protect the skin from heat rays and temperature changes between indoor and outdoor environments.

In the past, sunscreens based on physical filters were not very welcome because of the very visible white patina on the skin.

The most modern formulations are based on the same but micronised powders. This ensures greater product spreadability and even the anti-aesthetic white patina is much less visible.

Titanium dioxide is also used in many other cosmetics, especially in the make-up field. It contributes to the final white colour of the product and gives an opaque, anti-gloss effect, while also giving brightness to the skin, due to its reflecting effect of light.

 The TiO2 titanium dioxide is classified both for animals and humans as biologically inert.

In cosmetics it is increasingly used in micronised form, that is in the form of microparticles.

Certainly there is also titanium dioxide in the form of nanoparticles that would give greater cosmetic spreadability and acceptability, but on nanoparticles and their safety there are more and more doubts.

Nanoparticles are substances smaller than 0.1 micrometres or 100 nanometres.

According to the European Food Safety Authority (EFSA), which in 2011 published guidelines for assessing “potential risks related to certain uses of nanotechnology in the food sector”, nanoparticles may have different physical and chemical properties than the same material in non-nanoparticulate form.

For example, it was found that the absorption of UV rays by the TiO2 nanoparticles leads to a greater production of radical oxygen species.

This can lead to cellular damage, genotoxic effects, inflammatory responses.

Due to the widespread use of creams with sunscreen containing TiO2, exposure through the skin can be significant. 

The risk is that such small particles can penetrate through the skin causing damage due to accumulation in the body.

So far, from various studies, it appears that the TiO2 nanoparticles are not able

to penetrate through the intact skin, however, especially in the presence of UV, long-term data is still insufficient.

In the case of damaged or altered skin we know that the penetration of such small particles is possible. Nanoparticles could then pass into the blood and lymphatic flow, and accumulate in various organs causing oxidative stress and inflammation.

Finally, from recent studies it seems that sun protection products and cosmetics based on titanium dioxide and zinc oxide nanoparticles can also pose some problems to the environment.

(* BASF Environmental Evaluation of Sunscreen Products)

The titanium dioxide and zinc oxide nanoparticles are released into the seawater during the swim and can have toxic effects on marine organisms. With solar irradiation from the nanoparticles hydrogen peroxide would develop, which is a powerful oxidant and which damages marine plankton, an important component of the ecosystem of the sea and the oceans. It would seem, but it is not certain, that the accumulation of nanoparticles derived from sunscreen products at the coral reef with the consequent decrease in plankton, together with other environmental factors such as the heating of the oceans, is partly responsible for bleaching and of the progressive reduction of corals.

Titanium dioxide in micronised form is certainly safer for the skin. It is however appropriate that in formulations it is associated with antioxidant molecules, precisely to limit and neutralise the development of free radicals which, as I wrote before, always occurs with solar exposure, but to a much lower extent than titanium dioxide in nanoparticles.

Considering that we apply cosmetics to improve the state of the skin or protect it from the harmful effects of the sun, it is always important to evaluate well what to use for our health. And, as it seems, also for the environment