The Skin Sins: UV Exposure
Sunlight is essential for vitamin D production in the skin and of course our very own happiness. Excess exposure to UV rays have a prolific effect on skin ageing, so much so that the suns ray’s accounts for 90 percent of premature skin aging. Increasing levels of pollutants also have a habit for breaking down the ozone layer, which in more recent years has made us more vulnerable to UV exposure.
UV radiation is one of the major creators of molecule monsters known as free radicals. Free radicals are what is known as an unpaired electron making it extremely reactive enabling it to cause changes within a healthy cell. (see fig1)
Sun exposure is the primary environmental stressor leading to damaged skin. The damage to skin components caused by both prolonged and incidental sun exposure is called photoaging. Ozone layer depletion decreases our atmosphere’s natural protection from the sun’s harmful ultraviolet (UV) radiation. The presence of solar UV radiation in human life is essential for vitamin D production but also leads to skin photoaging, damage, and malignancies.
UV radiation is divided into three main types based on wavelength:
UVC radiation (200–280 nm) is predominately filtered by the ozone layer in the stratosphere
UVB radiation (280–320 nm) is mainly absorbed by the epidermis
UVA radiation (320–400nm) penetrates deeper into the dermis but interacts with both the Stratum Corneum (skin barrier) and epidermis as well.
The Skin & Environmental Ageing
The Stratum Corneum tries to block the penetration of ultraviolet light, filtering much of it out before it even reaches deeper into the skin however prolonged exposure to the rays knocks this on its head and begins to breakdown all layers. Alteration of the Stratum Corneum’s mechanical properties can lead to severe macroscopic skin damage such as chapping and cracking and associated inflammation, infection, scarring, and abnormal desquamation. Such damage can cause a compromised barrier function and can further aggravate skin disorders such as atopic dermatitis.
The penetration of UV radiation into the skin can also initiate detrimental photochemical reactions, causing both acute conditions such as erythema and chronic conditions such as photoaging, the main contributor to changes in skin’s appearance with age, and skin cancers. It is also important to know that while both UVA and UVB rays can harm the skin and lead to skin cancers, UVB is effectively blocked by glass. However, at least 50 percent of UVA radiation can pass through windows. (Car windows have been proven to let in more than 60 percent.) Photoaging damages collagen, elastin, melanocytes, and the moisture barrier, resulting in wrinkles, sagging, uneven skin tone, dark spots, and a rough, dry skin texture.