The sun emits electromagnetic radiation of different wavelengths (i.e. different energy). Some of the radiation, such as that making up the colors of rainbow, is visible which our eyes can see. The part of radiation beyond the violet end of visible light is called UV radiation which our eyes cannot see.
Are there any beneficial effects of UV radiation on human health?
A moderate exposure to the sun helps our body to produce vitamin D which could bring increased absorption and better utilization of calcium and phosphorus required for healthy bones and minimized risk of bone fracture.
Positive (beneficial) effects of UV:
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.
Bug Zapper: Insects are attracted to the UV light and killed by the electric shock in bug zappers.
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.
Helps moods – Research suggests that sunlight stimulates the pineal gland in the brain to produce certain chemicals called ‘tryptamines’. These chemicals improve our mood.
Helps some animals’ vision – Some animals (including birds, bees and reptiles) are able to see into the near UV light to locate many ripe fruits, flowers and seeds that stand out more strongly from the background. The fruits, flowers and seeds often appear quite different from how humans see them.
For example, when seen in UV light, some flowers have different line markings, which may help direct bees and birds to the nectar.
Aids some insects’ navigation – Many insects use UV emissions from celestial objects as references for navigating in flight. This is why a light sometimes attracts flying insects by disrupting their navigation process.
What are the harmful health effects of UV radiation?
Excessive exposure to UV radiation from the sun may cause painful sunburns, wrinkling and premature ageing of the skin as well as increase the risk of skin cancers and cataracts. In respect of skin cancer, about 80% of all cases may be attributable to excessive exposure to sunlight.
Specifically, studies suggested that UVB causes tanning of our skin slowly but significantly promotes the development of skin cancer, while UVA is responsible for the wrinkling, ageing and immediate tanning effects and may also enhance the development of skin cancer.
In respect of cataracts, the World Health Organization estimates that up to 20% of cataracts may be due to UV overexposure. Therefore, one must not underestimate the potential harm UV overexposure may bring.
Causes sunburn – 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 over-exposure 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.
Damages eyes – Prolonged exposure to UV or high intensities of UV (for example, in sunbeds) damages the tissues of 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.
In 1998, the Journal of 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.
Weakens plastics – Many polymers used in consumer items (including plastics, nylon and polystyrene) are broken down or lose strength due to exposure to UV light.
Fades colors – Many pigments (used for coloring food, cosmetics, fabric, plastic, paint, ink and other materials) and dyes absorb UV and change color. Fabrics, furnishings and paintings need protection from UV (fluorescent lamps as well as sunlight) to prevent color change or loss.