Sun Damage
Of all the many factors that cause extrinsic aging of the skin, the everyday assault by sunlight is the number one danger.
Being out in the fresh air and daylight is psychologically uplifting, even therapeutic. Sunlight is instrumental in enabling our bodies to make vitamin D, which in turn is needed to make use of calcium to build healthy teeth and bones. So is sunlight good for us? To some extent, yes.
But there’s a downside. Sunlight is damaging; it’s the biggest single cause of skin aging. The visible part of sunlight has some impact[1], but the most severe skin damage is caused by rays of invisible ultraviolet light (UV) that impacts our skin every day. It damages the cells in your eyes too.
UV is the component of sunlight that causes skin to darken as it tans, redden as it burns and peel when it’s burned too much. Too much UV exposure causes skin cell damage that can evolve into a variety of problems, including forms of skin cancer. In the U.S., Americans who live into their 60s have at least a 40 percent chance of having skin cancer at some point in their lives.[2]If you live in Australia, and you make the most of the outdoor life, your chances rise to more than 60 percent according to the Australian Cancer Council.[3]
Just as visible light is defined in terms of wavelengths, invisible UV light is categorized in the same way. There are three different subgroups within the UV spectrum: UVA, UVB and UVC.[4]
UVA is the group with the longest wavelength and represents around 95 percent of the UV radiation that reaches Earth. UVA is the radiation that causes tanning, which is an attempt by the body to protect the skin from damage. It penetrates the skin deeply and damages skin cells in the dermis and epidermis, causing wrinkles and other signs of aging. UVA has been shown to contribute to DNA damage in skin cells[5], which can lead to melanoma. Itpasses right through clouds and ozone; even on a dull and cloudy day, you’re still receiving a heavy dose of UVA (and thus need skin protection).
UVB, unlike UVA, is blocked somewhat by ozone and clouds, so UVB represents (on average) only around 5 percent of the UV radiation at the Earth’s surface(more on a clear sunny day). Nevertheless, UVB is more energetic than UVA and is absorbed in high concentrations in the epidermis (the top outer layer), where it causes a lot of damage. UVB has a shorter wavelength than UVA and so UVB cannot penetrate so deeply into the skin’s layers. That means all of its energy is absorbed in just a small layer of surface skin. It’s UVB that causes most of the reddening of skin exposed to sunlight. If your skin goes red, your skin has been damaged by UVB. Overexposure to UVB is a significant risk factor for skin cancers.
UVC is even more energetic than UVB, and even more dangerous, but because of its short wavelength it’s almost entirely blocked by the ozone layer. (There are some industrial sources of UVC, welding equipment for example, and people close to such equipment must wear protection for the skin and the eyes to avoid serious damage.)
[1]. Visible blue light causes inflammation and oxidative stress:https://www.sciencedirect.com/science/article/pii/S0014483515000044. Blue light at night affects circadian rhythms: https://www.health.harvard.edu/staying-healthy/blue-light-has-a-dark-side.
[2]. http://www.skincancer.org/skin-cancer-information/skin-cancer-facts
[3].http://www.cancer.org.au/preventing-cancer/sun-protection/about-skin-cancer.html
[4]. The UV subgroup wavelengths ranges are: UVA 320-400nm, UVB 290-320nm, and UVC 100-290mm.
[5]. UVA radiation damages DNA: https://www.sciencedaily.com/releases/2010/07/100701103415.htm.
Exposure to the Elements
In addition to the ravages of sunlight, just being in the atmosphere causes stress to our skin. Dry air outside and inside damages skin cells by dehydrating them. Polluted air, polluted water, and wind all attack your skin. Tobacco smoke and other pollutants lead to a decrease in oxygen levels in your skin and accelerate aging by reducing the skin’s regenerative capabilities.
Your skin also can be damaged by what is taking place inside your body. Damage at the cellular level can be caused by poor food choices, consuming damaging substances, lack of exercise and too much mental stress.
Dr. Marc Ronert - Age Later 