The Skin, The Sun And Protection: The Impact of UV Rays on The Skin

Activities such as deforestation and burning fossil fuels have increased greenhouse gas emissions resulting in a global phenomenon known as Climate change. One of the significant consequences of this global phenomenon is the depletion of the ozone layer, which helps protect the surface of the Earth from the Sun’s harmful Ultraviolet (UV) radiation. As the ozone layer depletes, more UV rays reach the surface of the Earth, increasing the risk of skin damage. Excessive exposure to high levels of UV rays can lead to sunburn, premature ageing and an increased risk of skin cancer.

UV radiation is a critical element of sunlight, it consists of UVA, UVB, and UVC rays, which can be differentiated based on their wavelengths. UVA (315-400 nm) and UVB (280-315 nm) rays can reach the surface of the Earth and not only deeply penetrate the skin but also impact its physiology and overall health. UVC rays do not typically reach the Earth's surface as most are absorbed by the Earth's atmosphere. When UV rays encounter the skin, they interact with biomolecules, mainly nucleic acids and proteins. Ultraviolet B rays are more energetic than Ultraviolet A rays and can directly damage DNA, resulting in the formation of cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts. These DNA lesions interfere with DNA replication base pairing, when the repair mechanisms are not able to correct these damages, mutations are often the result; If mutations persist there is an increased risk of skin cancer, which can be deadly. Even though UVA rays are less energetic, they generate reactive oxygen species (ROS) or free radicals within skin cells, contributing to oxidative stress and cellular damage affecting various parts of the skin such as epidermal cells, capillaries, elastin fibres and collagen.

In response to the harmful impact of UV rays, the skin has developed a multifaceted defence system. This defence system is a pigment known as Melanin and it is also responsible for skin colour. It acts as a natural sunscreen by absorbing and dissipating UV energy as heat. When exposed to UV radiation, melanocytes in the skin increase melanin production, resulting in tanning. However, this protection is limited, and prolonged or intense UV exposure can still overwhelm the skin's defences. Intense UV exposure can not only lead to sunburn but also photoaging which occurs when ultraviolet rays permanently damage the skin’s structure. Some symptoms of photoaging include wrinkling, pigmentation changes (age spots, liver spots, freckles), redness, uneven skin texture and blotchiness.

While UV rays are essential for vitamin D synthesis and mood regulation, excessive exposure can lead to adverse effects. Implementing sun-protective measures is essential in preventing these adverse effects. These measures include using broad-spectrum sunscreens both indoors and outdoors, ensuring reapplication every two hours. Wearing long protective clothing and sunglasses, avoiding the Sun during peak hours (10 a.m. - 4 p.m.) alongside artificial UV radiation from tanning beds, which can be just as harmful as natural sunlight.

By Rachell Dixon

References

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