How safe are zinc oxide and titanium dioxide?
If you search the internet for information about good, safe sun filters, then dermatologists will always advise zinc oxide and titanium dioxide. I have slightly mixed views about this.
It is funny to see how everyone accepts information they find on the internet without checking the source. I can understand why American dermatologists advise zinc oxide and titanium dioxide, because a number of good sun filters which we use in Europe have not yet been approved there. Sun cream products over there come under the medicines Act. This means that the registering of new filters is an expensive and endless process carried out through the FDA, leaving the country trailing behind with regard to the filters which are used and advised for use. Dutch skin specialists, however, should know better.
What do these sun filters do?
Zinc oxide and titanium dioxide are mineral filters. At present they are the most commonly used filters and very rarely cause an allergic reaction. They are so called broad spectrum filters? That is to say they protect against UVB as well as UVA rays. Zinc oxide is superior to titanium dioxide in this; the latter is missing a small part of the UVA spectrum in its protection.
So they are good filters, however both zinc oxide and titanium dioxide do make your skin stark white. They are therefore not good to use in their original state, unless you prefer to look like a geisha. Manufacturers have found a solution for this. By breaking down the active substances into microscopic particles the cream becomes more transparent. This process is called nanotechnology, and is controversial.
What do nanoparticles do?
I will tell you some more about this later, but simply put, one nanoparticle is not the same as another. The effectiveness and safety of nanoparticles directly relate to properties such as the ability to mix, the reaction in sunlight such as the generating of free radicals, the nature of the material, the exact size, weight and shape, the effect on the cell and the ability of the body to break it down. All of these properties determine the ultimate action and the effect in the body. You can compare it with a raindrop or a small stone on your car windscreen; the same size but with a very different impact.
Another point you should realise about titanium oxide and zinc oxide is that when exposed to sunlight they form free radicals. I am going to tell you more about these and other (negative) effects of zinc oxide and titanium dioxide (also described in their chemical abbreviation form ZnO and TiO2) below so that you can decide for yourself if you want to apply this substance onto your skin.
The forming of free radicals
Zinc oxide and titanium dioxide are known photocatalysts, meaning that the substances can form free radicals as soon as they come into contact with sunlight. And those free radicals can damage your cells and DNA, most definitely if you have an insufficient amount of antioxidants in your skin to eliminate them. This applies to both the ordinary particles and the nano version, and titanium dioxide appears to be slightly worse than zinc oxide. The problem is partly solved by the use of coated zinc oxide and titanium particles. A clever manufacturer who keeps their products up to date and doesn’t mind paying a little more for ingredients will use this. But that is not always clear to the consumer. Sometimes you can see on the packaging that coating has been used. You can also check with the supplier.
Do nanoparticles of zinc oxide and titanium dioxide penetrate the skin?
Several studies have shown that both sun filters in nano form penetrate into the skin no further than the stratum corneum (the outermost layer of the skin) – that is on a healthy, undamaged skin (i.e. these studies 1, 2, 3, 4, 5). However, in 2016 a study found that, in nano form, titanium dioxide can penetrate into the dermis. Nano-zinc oxide penetrates no further than the epidermis (i.e. these studies 1, 2, 3, 4). That was recently confirmed again in a study whereby subjects applied a cream, containing zinc oxide, onto the skin twice a day for five consecutive days.
Toxicologists see the greatest risk by the inhalation of the nano particles titanium dioxide and zinc oxide. According to the International Agency for Research into Carcinogenic Substances, titanium dioxide can be carcinogenic when inhaled in high doses and it is therefore better to avoid using sunscreens with these particles in spray and powder forms.
What are the effects on the environment?
I could write a whole blog on this subject; the mass use of sunscreen products is an environmental disaster. Oxybenzone for example is notorious, this sun filter has already broken down so much coral into powder! But there is also something to say about zinc oxide and titanium dioxide, and again titanium dioxide comes out worse than zinc oxide. The negative effect on the environment is mainly due to the fact that these substances can form free radicals. The uncoated version especially causes problems.
My conclusion? If, for instance, you are allergic to most sunscreen products (first check that you don’t have a sun allergy) then mineral filters are a good choice. My advice, then, is to use a cream with a zinc oxide base rather than titanium dioxide.
Don’t be fooled, a cream which is translucent or quite translucent, always uses nano particles, even if the manufacturer doesn’t mention this. Organic brands also make use of it; and this is also acceptable in American products. It doesn’t have to be a problem at all, certainly not with coated nano particles zinc oxide, but if you would rather not, then check with the supplier. With regard to the environment, if you are swimming in a coral area, think about wearing sun protective clothing instead. Every little bit helps.
One last tip! Make sure that you have a good supply of antioxidants in your skin, eat plenty of fruit and vegetables and apply a cream with antioxidants. Then you will reduce the risk of free radicals damaging your skin.
Research Physician Cosmetic Dermatology