Why should excess exposure to ultraviolet light be avoided?

Electromagnetic radiation encompasses a wide range of wavelengths and energies, including visible light, radio waves, X-rays, and ultraviolet (UV) light. The latter is particularly important when discussing sun exposure, as UV light has the capability to affect the skin and other living tissues adversely.

UV light is categorized into three types: UVA, UVB, and UVC. UVA has the longest wavelength, followed by UVB, while UVC has the shortest. It's essential to understand that although UVC is the most harmful, it is mostly absorbed by the Earth's ozone layer and doesn't reach the ground. UVA and UVB, however, do reach the surface and can penetrate the skin, leading to various health concerns.

Due to its higher energy levels compared to visible light, UV radiation can initiate chemical reactions in the body, some of which can be damaging. For instance, it can break chemical bonds in DNA, which is why protecting oneself from excessive UV exposure is crucial.

DNA is the blueprint of life stored in every cell, instructing them how to function. When UV light penetrates the skin, it can interact with the DNA molecules in the cells. The high energy of UV radiation, especially from UVB rays, can cause neighboring thymine bases in DNA to dimerize, forming thymine dimers. This alteration is a form of DNA damage known as a mutation.

Our bodies can sometimes repair this damage, but not always. If the repair is unsuccessful or incomplete, mutations accumulate. Over time, these mutations can interfere with the cell's normal operation, which may lead to uncontrolled cellular growth - the hallmark of cancer. In the context of skin cells, this means an increased risk for skin cancers such as basal cell carcinoma, squamous cell carcinoma, and melanoma.

Moreover, DNA damage is not limited to the risk of cancer. It can also trigger cell death, immune responses, and premature aging of the skin, manifesting as wrinkles and loss of elasticity.

Preventing skin cancer is a multi-faceted approach that hinges on protecting the skin from excessive UV radiation. Since we can't completely avoid sunlight, which is the main source of ultraviolet light, we can take measures to minimize our risk of skin damage and cancer.

Among the most effective strategies are the use of broad-spectrum sunscreens, which block both UVA and UVB rays, with a Sun Protection Factor (SPF) of 30 or higher. Reapplying sunscreen every two hours, especially after swimming or sweating, is also crucial.

Other preventative measures include wearing protective clothing, such as long-sleeved shirts, wide-brimmed hats, and sunglasses with UV protection. Seeking shade, especially during the hours when the sun's rays are most intense (10 a.m. to 4 p.m.), and avoiding indoor tanning beds are also key practices in reducing the risk of developing skin cancer.

Like the skin, the eyes are susceptible to harm from UV radiation. Long-term exposure can lead to serious eye conditions, including cataracts, which is the clouding of the lens, leading to decreased vision, and photokeratitis, also known as UV keratitis, which is akin to a sunburn of the cornea.

Protecting our eyes can be achieved by wearing sunglasses that offer 100% UV protection. They not only shield the delicate tissue of the eye but also the surrounding skin, which is thin and vulnerable to damage from UV radiation. Wrap-around styles can provide additional side protection, which is especially beneficial for individuals spending long periods in highly reflective environments like snow or water.

It's also wise to wear a wide-brimmed hat for added shade and to monitor any changes in vision with regular eye exams, as early detection of UV-related eye damage can help prevent more severe consequences.