Effects of Sun Exposure
The public has increasingly become aware of the negative effects and dangers of excessive exposure to ultraviolet radiation in the form of sunlight. While some exposure to the sun is important for vitamin D metabolism, bone health and development in children, in most environments, incidental sun exposure is adequate to achieve these objectives. Vitamin D deficiency rickets in the United States due to inadequate sun exposure is rare. In most cases, health problems related to sunlight are not due to a deficiency, but rather over-exposure to the sun. Besides skin cancer, there are several other negative sun-associated effects including photoaging and wrinkling.
The spectrum of light emitted by the sun includes visible and invisible rays. The invisible wavelengths known as ultraviolet-A (UVA) and ultraviolet-B (UVB) are the most harmful. Both UVA and UVB contribute to tanning of the skin, sunburns and damage to skin cells.
The amount of UV exposure is greater at higher altitudes, during the summer months, between the hours of 10AM-4PM and in tropical regions (closer to the equator). Water, ice, sand and snow can reflect and intensify UVA and UVB rays. When the weather is cloudy, UV radiation continues to reach the earth because clouds are poor absorbers of UV light.
Effects of the sun
Sunburn – Skin that has been exposed to sunlight for too long causes sunburn with associated redness, pain, swelling and blistering. Severe cases of sunburn can cause fever, chills, nausea, increased heart rate and low blood pressure. Shedding of the skin after 1 week is common. Generally speaking, the lighter the baseline skin color, the more likely the skin is to burn when exposed to the same amount of UV radiation. Sunburns can occur during overcast days as well as sunny days. A person`s risk for malignant melanoma doubles if he or she has had 5 or more sunburns.
Treatments for sunburn include pain management with acetaminophen (Tylenol) or nonsteroidal anti-inflammatory medications, cool compresses and soothing emollients such as aloe vera lotion.
Tanning – Though tanning is often mistaken for the appearance of good health, tanning of the skin is a sign of injury to skin cells. The pigment-producing cells of the skin respond to the damaging UV rays by producing more melanin (pigment). Indoor tanning is just as bad for your skin as sunlight. Tanning salons are certainly no safer than natural sunlight since most tanning salons administer UVA radiation. UVA light penetrates deeper into the skin than UVB light to contribute to premature aging and skin cancer. Spray tans and tanning lotions containing a chemical called dihydroxyacetone are a safer alternative to UV light exposure.
Aging – Outdoor workers or others who sun bathe frequently tend to develop tough, leathery skin as well as freckles, broken blood vessels and other blemishes that make them appear older than they actually are. Children, adolescents and young adults may not be as aware or concerned about the negative effects of UV radiation. Because the lifetime sun exposure in most individuals occurs before age 20, parents need to be proactive in educating their children from an early age about the importance of sun protection.
Wrinkles – UV radiation creates free radicals (unstable oxygen molecules) which in turn activate proteins called metalloproteinases which break down collagen, to form fine lines and wrinkles.
Skin cancer – Sun exposure clearly contributes to the three most common forms of skin cancer: basal cell carcinoma, squamous cell carcinoma and malignant melanoma. In fact, more than 90 percent of all skin cancers occur on sun-exposed areas of the skin such as the face, scalp, ears, forearms and backs of the hands.
Sun reactions – Certain troublesome skin rashes including red, blotchy areas, hives, and itchy eruptions are caused by sun exposure. Other sun-induced rashes only occur in association with the use of medications including certain antibiotics and medicines used to treat high blood pressure, arthritis and depression. Skin reactions can occur with sun exposure after exposure to certain perfumes, plants, lime juice and certain topical medications.