What do woolen clothing protect us from

Clothes instead of sunscreen: how well they protect against UV radiation

Long sleeves protect better than greased arms in midsummer - that's what Prof. Dr. Hans-Christoph Mertins, Dean of our Department of Physical Technology, and Assoc. Prof. Dr. Heiko Timmers. Born in Steinfurt, he is currently teaching at the University of New South Wales in Canberra. Two material physicists on the complex sun protection problem that cannot be completely solved.

Assoc. Prof. Dr. Heiko Timmers from the University of New South Wales in Australia (r.) And Prof. Dr. Hans-Christoph Mertins from our physical engineering department explain why you should wear long clothes in summer. (Photo: FH Münster / press office)

We have to protect ourselves from strong sun rays in summer - everyone knows that and uses sunscreen and a sun hat. But what exactly are we shielding ourselves from?

Prof. Mertins: The UV rays in sunlight are dangerous. They come in different wavelengths - the shorter the wavelength, the more energy they have and the more dangerous they are. Fortunately, most of the most dangerous UV-C radiation remains in the atmosphere. But we have to protect ourselves from UV-A and UV-B radiation, because they penetrate our skin cells to different depths and can cause cancer through cell mutations.


How can you best protect yourself from UV radiation?

Prof. Timmers: First of all, you have to know that absolute protection is hardly possible. A single UV exposure can cause cancer. But the probability is extremely low. We in Australia have a very high level of solar radiation, so children are only allowed to go to the school yard with hats and neck protection in summer, for example. This shows that sun protection works best with clothing.

Prof. Mertins: Many people believe that sunscreen offers 100% protection, but that is not true. It only increases the amount of time you would normally spend in the sun before getting sunburned. And it can be rubbed off. Clothing, on the other hand, offers constant protection.


What clothes do you recommend?

Prof. Mertins: Clothes are made of fabric, and the types of fabric differ immensely. Tightly woven textiles such as cotton or plastics are recommended in direct sunlight - thin silk, for example, would be rather bad, and coarse-meshed linen is also not an advantage.

Prof. Timmers: There are also so-called UV clothing, the idea of ​​which was developed in Australia. But this is also appropriate in this country if you want to spend a whole day on the beach or go on a hiking tour in the mountains.


What exactly is UV clothing? How does it differ from our normal clothing?

Prof. Timmers: Actually, every piece of clothing protects with a certain factor, just like the sunscreen. This UPF factor depends on the density of the fabric. If the fabric is made in such a way that half of the UV radiation lands on the skin, the garment has a factor of 2. UV clothing is clothing with a UPF factor of 50 and more - so only a maximum of one fiftieth of the radiation can get through the fabric. There is talk of new clothing. Some items of clothing are subjected to an endurance test before the UPF rating, the 801 standard. This is because the fabric stretches when it is worn and washed, and so the used or wet material absorbs less UV radiation. The test simulates this and awards a label if the garment continues to protect with a factor of 50.

Prof. Mertins: But it is important to find a compromise. Because with too much clothing you sweat more, and you don't want to get a heat shock either. So if you cycle along shady avenues in summer, you don't necessarily need UV clothing. But hat and sunglasses. And good to know: dark clothes absorb more UV radiation than light ones!


Does UV radiation also have advantages?

Prof. Mertins: Yes, with a healthy dose we stimulate our vitamin D balance. The dose is determined by the intensity of the sun's rays and the length of time. So if you stay outside longer, you should look for shade and thus reduce the dose.

Prof. Timmers: UV radiation is also a blessing in research. A lot can be done with it, especially in materials physics. For example, UV light can sterilize surfaces. Or it is used in spectroscopy: We analyze materials with light, or more precisely the interaction of light and matter, without destroying the material. This is particularly important in our current research area of ​​nano-physics, where individual atomic layers are involved.