Health effects of ultraviolet radiation
Ultraviolet (UV) radiation has some benefits. But as with all forms of radiation, there are risks involved with overexposure to UV radiation (rays).
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A tan is visible proof that your skin has been damaged by UV rays. Tanning is your skin's response to overexposure to UV rays. Sunburn is also caused by too many UV rays: your skin turns red and may become hot and painful or even swell and blister.
Overexposure to UV rays also causes premature aging effects, like:
- skin wrinkling and hardening (leathery skin)
- loss of elasticity
- dark patches ("age spots" or "liver spots")
- precancerous skin changes (called actinic keratoses)
Skin damage caused by the sun is cumulative. This means that long-term, daily exposure to sunlight adds up. UV exposure causes damage in the DNA of your skin cells. Damaged cells die or repair themselves. If, however, the damage is too severe to be repaired, you can get skin cancer.
During the summer months your health may be at risk from extreme heat especially if you are sunburned. Sunburned skin loses its sweating efficiency, which slows your body's ability to regulate its temperature.
Too much exposure to UV rays may cause painful temporary injuries to your eye (called photokeratitis and photoconjunctivitis). Reflections off water, sand, snow, concrete and glass can inflame your cornea and conjunctiva within minutes. This is like burning the sensitive, skin-like tissue covering your eyeballs and lining your eyelids. "Snow blindness" is a term used by skiers and snowboarders when they experience this after a day on the slopes without goggles.
Remember to wear sunglasses that provide UVA and UVB protection in every season. Exposure to UV from the sun can prematurely age your eye lenses, causing clouding of the lens (cataracts), non-cancerous growths of tissue (pterygium), loss of vision (macular degeneration), and cancer of the eyelid.
Weakened immune system and increased infections
Hanging out in the sun can also weaken your immune system (your body's natural defence against disease). UV rays can suppress your body's ability to resist bacteria, which increases your risk of infection. Also, UV rays can cause smallpox lesions to grow, and can reactivate Herpes simplex Virus I and II (which cause cold sores).
Tans weren't always popular. Being as pale as possible was once desirable in some countries because a tan was a sign of outdoor manual labor. The wealthy could afford to have other people do that work for them, so people tried to look pale to appear rich.
Everyone is at risk for UV damage. But some people are more easily affected than others.There are many factors that increase your risk. You need to be especially careful of UV exposure if you have:
- a fair complexion (skin colour)
- blond, red or light brown hair
- lots of moles (20 or more), several larger moles (5mm or more), or a larger mole present at birth
- freckles and a tendency to burn, instead of tan
- had severe sunburns, especially in childhood and early adulthood
- a heredity disorder like xeroderma pigmentosum, Gorlin's syndrome, or lupus
- been treated for skin cancer
- a family history of skin cancer
- been treated with radiotherapy (for psoriasis and other skin conditions)
You are also at greater risk if you:
- spend a lot of time outdoors (farm worker, gardener, lifeguard, or building site/construction worker)
- tan in the sun or use tanning equipment
- live or vacation in an area where intense sun exposure is common (high altitudes or tropical regions)
- are an organ transplant patient and take medications to lower your immunity
- are taking medications that increase your sensitivity to UV rays (examples: oral contraceptives, antibiotics, anti-inflammatories, tranquilizers, anti-nausea drugs, antidepressants, and medicines for high blood pressure, heart conditions and diabetes)
- have had contact with certain chemicals, including coal tar, soot, pitch, asphalt, creosote, paraffin wax, petroleum products, and arsenic
Although people with light skin are more likely to have UV damage, those with dark skin can also be affected.
There is no safe way to tan. Protect yourself by following these safety tips:
- Cover up. When the UV Index is 3 or higher, protect your skin as much as possible. Wear light-coloured, long-sleeved shirts, pants, and a wide-brimmed hat made from breathable fabric. When you buy sunglasses, make sure they provide protection against both UVA and UVB rays.
- Limit your time in the sun. Keep out of the sun and heat between 11 a.m. and 3 p.m. The UV index in Canada can be 3 or higher during those times. When your shadow is shorter than you, the sun is very strong. Look for places with lots of shade, like a park with big trees, partial roofs, awnings, umbrellas or gazebo tents. Always take an umbrella to the beach.
- Use the UV Index forecast. Tune in to local radio and TV stations or check online for the UV index forecast in your area. When the UV index is 3 or higher, wear protective clothing, sunglasses, and sunscreen, even when it’s cloudy.
- Use sunscreen. Put sunscreen on when the UV index is 3 or higher. Use sunscreen labelled “broad spectrum” and “water resistant” with an SPF of at least 30.
- Drink plenty of cool liquids (especially water) before you feel thirsty. If sunny days are also hot and humid, stay cool and hydrated to avoid heat illness. Dehydration (not having enough fluids in your body) is dangerous, and thirst is not a good indicator of dehydration.
- Avoid using tanning equipment. There is no such thing as a ‘healthy’ tan. Using tanning equipment damages your skin and increases your risk of developing melanoma, the deadliest form of skin cancer.
Vitamin D production
Vitamin D helps your body absorb calcium and phosphorus which plays a big role in bone development.
The UVB part of sunlight is what creates vitamin D in your skin. However, season, time of day, cloud cover, smog, skin pigmentation, and sunscreen use are all factors that can affect the amount of UV rays you receive. Intentional UV exposure to meet Vitamin D requirements is not recommended. You can get vitamin D by eating fatty fish, eggs, and fortified foods (like milk and margarine). Following Eating Well with Canada's Food Guide will help meet your needs for vitamin D.
Most people in Canada are not deficient in vitamin D. However, if you have dark skin, are over the age of 50, do not drink milk, or avoid the sun, you are at higher risk of low blood levels of vitamin D. Talk to your health care provider to see if vitamin D supplements are needed.
Treatment of skin conditions
UV rays have been used to successfully treat a number of diseases, including rickets, psoriasis, eczema, jaundice, lupus vulgaris, and vitiligo.
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