UV rays are part of the natural energy produced by the sun. On the electromagnetic spectrum, UV light has shorter wavelengths than visible light, so your eyes can’t see UV, but your skin can feel it.
While UVA and UVB rays differ in how they affect the skin, they both do harm.
In this article, we discuss the Positive and Negative Effects of UV Rays as part of July Ultraviolet Safety Month.
Positive (beneficial) effects of UV Rays
Triggers vitamin D
UV from the Sun is needed by our bodies to produce vitamin D. Vitamin D helps strengthen bones, muscles, and the body’s immune system. It may also lower the risk of getting some kinds of cancers such as colon cancer.
Helps some skin conditions
UV is used in the treatment of skin conditions such as psoriasis. This is a condition where the skin sheds its cells too quickly and develops itchy, scaly patches. Exposure to UV slows the growth of the skin cells and relieves the symptoms.
Research suggests that sunlight stimulates the pineal gland in the brain to produce certain chemicals called ‘tryptamines’. These chemicals improve our mood.
Useful for disinfection and sterilization
UV has positive applications in the fields of disinfection and sterilization. UV can effectively ‘kill’ (deactivate or destroy) microorganisms such as viruses and bacteria, for example, when hanging cloth nappies, underwear, and tea towels outside on the clothesline.
To destroy the microorganisms, UV rays penetrate the cell’s membrane, destroying the DNA, and so stops its ability to reproduce and multiply. This destructive effect explains why we can use UV antibacterial lamps for disinfection and sterilization. Mangere Wastewater Treatment Plant in Auckland uses UVC light to disinfect wastewater.
Negative (harmful) effects of UV Rays
Causes skin cancer
UV is an environmental human carcinogen. It’s the most prominent and universal cancer-causing agent in our environment. There is very strong evidence that each of the three main types of skin cancer (basal cell carcinoma, squamous cell carcinoma, and melanoma) is caused by sun exposure. Research shows that as many as 90% of skin cancers are due to UV radiation.
UV burns the skin. Sunburn is a burn that occurs when skin cells are damaged. This damage to the skin is caused by the absorption of energy from UV rays. Extra blood flows to the damaged skin in an attempt to repair it, which is why your skin turns red when you are sunburnt.
Damages immune system
Over-exposure to UV radiation has a harmful suppressing effect on the immune system. Scientists believe that sunburn can change the distribution and function of disease-fighting white blood cells in humans for up to 24 hours after exposure to the sun. Repeated overexposure to UV radiation can cause even more damage to the body’s immune system.
The immune system defends the body against bacteria, microbes, viruses, toxins, and parasites (disease and infection). You can see how effective the immune system is by looking at how quickly something decays when it dies and the immune system stops working.
Prolonged exposure to UV or high intensities of UV (for example, in sunbeds) damages the tissues of the eyes and can cause a ‘burning’ of the eye surface, called ‘snow blindness’ or photokeratitis. The effects usually disappear within a couple of days, but may lead to further complications later in life.
The American Medical Association reported that even low amounts of sunlight can increase the risk of developing eye damage such as cataracts (which, left untreated, will cause blindness), pterygium, and pinguecula. UV damage to the eyes is cumulative, so it is never too late to start protecting the eyes.
UV speeds up the aging of skin since the UV destroys collagen and connective tissue beneath the top layer of the skin. This causes wrinkles, brown ‘liver’ spots, and loss of skin elasticity. The difference between skin tone, wrinkles, or pigmentation on the underside of a person’s arm and the top side of the same arm illustrate the effects of sun exposure on the skin. Usually, the top side of the arm has had more exposure to the sun and shows greater sun damage.
Because photo-aging of the skin is cumulative, it is never too late for a person to start a sun protection program. Otherwise, though a tan may look good now, you could be paying for it with wrinkly leathery skin or skin cancer later.
Despite the risk factors, you can safely, and happily enjoy the great outdoors by protecting your skin against UV exposure with a broad-spectrum sunscreen and sun-safe clothing, hats, and eyewear. You can also consider UV window film for your home and car.