We are surrounded by UV rays wherever we go outside – even on cloudy days. While UV light has positive effects, it can still damage our body in several different ways. That's why we protect ourselves with sunglasses and sunscreen. But what actually blocks UV light? BETTER VISION answers questions like: Do windowpanes or car windows provide effective UV protection? What is most important when selecting a pair of eyeglasses with UV protection? Does spending time in the shade reduce your exposure to radiation? And does clothing help protect your body against UV rays – and if yes, how?
The sun is shining and there's not a cloud in the sky – on days like these, a lot of people grab their sunglasses and put on some sunscreen to protect themselves when spending longer periods outside. Yet UV radiation is not just found outdoors in the sunlight – UV rays even penetrate your windows. While most windowpanes provide a certain degree of UV protection, a portion of the damaging UV light – UV-A radiation – comes through without being filtered out. You can see this in clothes or window coverings that have been near a window for a longer period of time: the sunlight causes the colors to fade and damage to the fabric.
UV light can damage your eyes as well as your skin – and not just when the sun is shining. Thus not only sunglass lenses, but also normal eyeglass lenses should have a special UV filter with protection up to 400 nm1 to effectively protect your eyes from UV radiation. With sunglasses, however, UV protection should not be confused with glare protection: even sunglasses without a UV filter reduce the intensity of the sunlight and consequently provide glare protection. However, this only minimizes brightness, not the level of UV radiation. UV rays not only come through, but can sometimes do more damage than without sunglasses. The dark lenses cause the pupil to expand, letting in even more UV light. So make sure you only purchase sunglass lenses with optimum protection against glare, reflections and damaging UV radiation. When buying eyeglass lenses, always check that they offer full UV protection up to 400 nm1. If the salesperson can't give you any information or only very imprecise details about the level of protection offered by the sunglass lenses, you shouldn't buy them.
Most car windows offer only limited UV protection. Windshields are equipped with an effective UV blocker that protects against both UV-B and UV-A radiation. Since the 1980s, for example, the front windshield on all new cars is equipped with a colorless, transparent film that blocks all UV-B radiation and almost all UV-A radiation.
However, this is not sufficient for comprehensive UV protection in your car: most side and rear windows do not contain any UV filter for either UV-A or UV-B radiation. As a consequence, these untreated windows can let in up to 80 percent of UV-A radiation. Even tinted windshields aren't an effective means of protection, because these only filter out around 40 percent of UV-A radiation. Read more about the different types of UV radiation here
Thus UV radiation isn't just a concern when you're enjoying the sunny weather at the beach – it's found virtually everywhere no matter the time of day. Sunscreen and clothing help protect your skin against the harmful UV rays. The tighter the weave, the better the level of protection – we'll explain this in more detail below. Your eyes, however, still need eyeglass or sunglasses lenses with UV protection.
While there is less UV radiation in the shade than in direct sunlight, up to 50 percent of harmful UV radiation can still reach you. It's even possible to get a harmful dose of UV light under a patio umbrella or awning. Buildings, water and sand reflect up to 85 percent of radiation. UV radiation even penetrates the surface of the water, so be careful when swimming: at a depth of 3 feet, UV-A radiation can still have an intensity of 75 percent, UV-B radiation an intensity of 50 percent. Make sure you cover your face and body with a suitable, waterproof sunscreen. Since there are different types of UV radiation and people react differently to these depending on their skin type, sunscreens have been specially adapted to meet these needs.
The best form of sun protection depends largely on your skin type and the particular self-protection time of your skin. "Self-protection time" refers to the amount of time your skin can be exposed to the sun without burning. People with light skin and light-colored hair (blond, red, light brown) have a shorter self-protection time than those with a dark skin types and dark hair (brown, black). A blond, light-skinned person has a self-protection time of around ten minutes. The sun protection factor (SPF) of a sunscreen tells you how much longer you can stay in the sun without getting a sunburn. For example, sunscreen with a sun protection factor of 30 increases the skin's self-protection time by a factor of 30, i.e. a self-protection time of 10 minutes multiplied by 30 equals 300 minutes or five hours – that's the amount of time the sun cream protects your skin against damage.
Here's how to determine your ideal self-protection factor: divide the amount of time you plan on staying in the sun by your personal self-protection time to find the SPF that's right for you. If a light-skinned person with a self-protection time of 10 minutes wants to relax on the beach for around about 150 minutes, then a self-protection factor of 15 is just fine.
There are also special UV clothes with a UV blocker for swimming or spending longer periods of time outdoors.
Clothing is a good form of sun protection for the outdoors. Together with an outstanding pair of sunglasses for your eyes and sunscreen for your skin, you'll enjoy effective, protection for your entire body – assuming you're wearing the right clothes. While any piece of clothing protects against harmful UV radiation, how well it does this depends on two factors: the weave and the thickness of the cloth. Keep the following rule of thumb in mind: the tighter the weave, the less UV light can reach your skin. While white cotton or linen t-shirts are especially popular on hot days, they offer little protection and let through a large portion of UV radiation. Clothes made of synthetic fibers like polyester offer better protection because they can be manufactured and processed with tightly-woven fibers. The density of cotton fibers depends on the cotton itself. Amongst the natural materials, natural silk offers a high UV protection factor: the fibers feature matting components which reflect and absorb UV rays. The "ultraviolet protection factor" (UPF) indicates the level of protection offered by special UV clothing. This tells you how much longer you can spend in the sun without damage – much like the sun protection factor of a sunscreen. When purchasing special clothing or swimwear with UV protection, make sure has the UV standard 801 classification in addition to the sun protection factor. This guarantees that your clothes will afford UV protection not only when they're unstretched and dry, but also after they're stretched out and wet. This way the UV light will be blocked effectively in any situation.