![]() Does Melanin Protect The Skin From UV Radiation?.You can skip the overview by using the table of contents below. If you’re not particularly interested in the detailed science behind sun damage, how sunscreen works, or how sunscreen protection is measured – here is a (not-so) brief overview… Part III (this article) – The Best Sunscreens With High UVA Protection. Part II – How Is Sunscreen Tested? SPF vs UVAPF If you’re interested in the science, or if you would like to be directed to sources for this information, please see Parts 1&2. This article is Part 3 of a three-part sunscreen guide. So how do we know how much UVA protection a sunscreen offers? Which sunscreens have the highest UVA protection? Fear not! For here are the best sunscreens with high UVA protection… While UVA rays are less associated with skin cancer than UVB rays, they are the biggest contributor to sun-induced premature aging. However, SPF is only a measure of how effective a sunscreen is at blocking UVB rays. The majority of people understand how SPF works – the higher the SPF, the more protective the sunscreen is. Not only is too much sun exposure associated with a higher increase in skin cancer, but it contributes to 80-90% of facial skin aging. You can also submit answers by post to: The Last Word, New Scientist, 25 Bedford Street, London WC2E 9ES.Daily sunscreen use is essential for our overall skin health. New Scientist Ltd retains total editorial control over the published content and reserves all rights to reuse question and answer material that has been submitted by readers in any medium or in any format. Please include a postal address, daytime telephone number and email address. We reserve the right to edit items for clarity and style. To answer this question – or ask a new one – email should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. This effect is enhanced when there are more particles in the air, which is why volcanic explosions can lead to spectacular sunsets. At sunset and sunrise, when sunlight strikes Earth at a low angle compared with the observer and therefore passes through a large amount of atmosphere on its route to the surface, the result tends to be red and yellow skies. The more atmosphere the light passes through, the greater the effect. This means that as sunlight passes through the atmosphere, blue light is filtered out more than other wavelengths. Different wavelengths are affected to a different extent, with short wavelengths (blues and UV) affected the most. But caution is needed even then as the eyes and face will still be subject to UV radiation reflected from the ground and backscattered from elsewhere in the sky.Īll light waves are scattered as they interact with molecules and particles in the atmosphere, a process known as Rayleigh scattering. The parts of the face that are angled slightly upwards, such as the nose, will be more susceptible to burning when the sun is higher in the sky, when irradiance will also be greater. This suggests that the face, much of it being a nearly vertical surface, receives the most radiation at this angle. In the UK, the sun generally climbs higher than this only in the summer months. One recent study found that the greatest amount of UV radiation reaches the eye when the sun is at an elevation of 40 degrees. The strength of ultraviolet radiation at ground level varies through the day due to attenuation that is largely dependant on the sun’s angle in the sky. Of course, if a person is lying on their back, their face will get the most UV when the sun is highest in the sky. A walker’s face is likely to get the most impactful UV radiation when the sun is between 40 degrees and 60 degrees above the horizon. ![]() When the sun is directly overhead, known as the zenith, its light doesn’t hit the face of a person walking below. Because UVB can cause more biological damage than UVA, the effects of UV radiation on human skin are stronger when the sun is high in the sky. ![]() Therefore, when the sun is low in the sky, the proportion of UVB falls compared with UVA. The most energetic band, UVC, is absorbed by ozone in the atmosphere, and more UVB is absorbed by the atmosphere than UVA. The UV radiation spectrum is divided into three bands: UVA (320 to 400 nanometres), which is close to visible light, UVB (280-320 nm) and UVC (100-280 nm).
0 Comments
Leave a Reply. |