The ABCs of UV rays

MOST people battle sunburn and eye damage with products boasting of absolute protection against harmful ultraviolet (UV) rays. But UV beams are not that simple and easy to sweat off.

Perceived by many to exist as a single type, harmful UV rays actually have three kinds based on their effects on human health and environment, namely UVA, UVB, and UVC.

UVA rays constitute 99 per cent of UV rays that reach the earth’s surface. With wavelengths measuring 320-400 nanometers, UVA rays are the longest of the three. They can penetrate clouds, light clothing, and untinted glass easily, and are least absorbed by the ozone layer. UVA rays produce long-term effects such as premature skin aging and wrinkles.

Longer in wavelength than UVA rays are the UVB rays, which make up the remaining one per cent of UV rays. Also known as medium wave, UVB rays measure 280-320 nanometers and are 1,000 times stronger than UVA, making it responsible for the immediate effects of UV ray exposure such as sunburn. However, UVB is essential to the body, as it stimulates Vitamin D production.

Meanwhile, UVC rays, the most hazardous, are mostly absorbed by the ozone layer. Measuring less than 280 nanometers, UVC have the shortest wavelength. The major artificial sources of UVC rays are water purifiers and germ-killing lamps. The rays’ effects become more risky with the thinning ozone.

Ray, ray, go away

UV rays are the most common cause of skin cancer, cataracts, premature skin aging, and weakening of the immune system. It may also cause solar keratosis, a disease more commonly found among fair-skinned people. It is characterized by thick, scaly, or crusty patches of skin.

According to Dr. Melanie Pauline Chao-Lo, chief resident of the Dermatology Department of the UST Hospital, prolonged exposure to the sun’s UV rays may lead to sunburn, characterized by reddening or, among Filipinos, browning of the skin.

Filipinos, who are brown-skinned, are less at risk from the negative effects of UV rays since they have more melanin, a chemical that serves as the skin’s protection from UV rays, resulting in darker skin color.

Some people believe that taking regular breaks during sunbathing would help prevent accumulation of sunburn, but according to the World Health Organization, UV ray exposure is cumulative during the day, making regular breaks useless.

Sunburn is also thought by many to occur only if the hot rays of the sun are felt. But, UV rays cannot be felt. It’s the infrared rays of the sun that are responsible for the heat.

Further, there is no such thing as a fashionable or healthy tan. A tan is a result of UVB rays reacting with melanin. Tanning salons used as substitute to sunbathing can actually be more damaging since it uses pure UV light, mostly made up of UVA rays, which is responsible for premature skin aging and skin cancer.

Although not naturally found in the earth’s surface, UVC rays from artificial sources may also cause temporary skin redness and eye irritation.

Most skin damage from UV rays are acquired from the skin’s overexposure to it. The amount of UV rays that the skin is exposed to may vary depending on several factors: the time of day, amount of clouds present, elevation, environment, location, duration of exposure to the sun, and type of clothing worn. For example, the skin is more vulnerable to the effects of UV ray exposure during noontime, with less amount of clouds to reduce the amount of rays reaching the earth’s surface.

Also, in elevated areas, where the air is thinner and clearer, the skin is exposed to more UV rays, as well as areas near sand, water, or concrete where UV rays are not absorbed but reflected.

According to Chao-Lo, to prevent UV-induced skin damage, sunblock lotion should be applied 30 minutes prior to sun exposure everyday, not only during the summer, and must be reapplied every two hours.

“The most ideal time of the day for sun exposure is from seven to nine in the morning and four to five in the afternoon,” she said.

In a study published by the New England Journal of Medicine, titled “Reduction of Solar Keratoses by Regular Sunscreen Use,” it was reported that daily sunscreen application has proven to decrease incidence of solar keratosis.

Sunblock lotion protects the skin by either absorbing, scattering, or reflecting the UVA and UVB rays reaching the skin, depending on its active ingredient. It helps prevent negative effects of prolonged exposure to UVA and UVB rays. Protection against UVC rays isn’t necessary since it is already absorbed by the ozone layer.

A way of determining sunblock lotion’s effectiveness is through its sun protection factor (SPF), a measure of a lotion’s effectiveness based on the length of time it takes before a person acquires sunburn due to UVB rays. According to Chao-Lo, the higher the SPF, the more effective it is in protecting the skin.

Contrary to popular belief, SPF values cannot be added. Applying two sunblocks with SPF 15 and SPF 12 will only result in a protection factor of 15, the higher SPF among the two.

In addition, not only SPF should be considered in choosing a sunblock lotion, as there are certain ingredients that should also be looked for. Chao-Lo said that chemical ingredients such as PABA or PABA ester, a UV absorbing chemical, or Titanium dioxide, a UV scattering agent, should be present in a sunblock lotion.

Sunglasses can also help in reducing UV rays by absorbing them. Ideally, sunglasses should block at least 99 to 100 percent or up to 410 nanometers of UVA and UVB radiation.

To avoid the adverse effects of the scorching sun and its UV army, it is still best to retreat to the shade and avoid the sun altogether whenever possible.