Weighing the Effects of UV Sunlight

by Anna Birk

Shiyong Wu presenting the effects of Ultraviolet light, Photo by Anna Birk

Ultraviolet, or UV, rays are a topic we often hear about during the summer, when it becomes a rarity to leave home without sunscreen.  What many people may not consider, however, is that radiation from ultraviolet light can be extremely harmful in the winter months as well. Likewise, many may not consider that there are three UV rays leaving the sun. The two UV rays which humans interact with on a daily basis are UV-A and UV-B.UV-A radiation causes premature aging and is more prominent in sunlight than UV-B. UV-B radiation creates sunburn and black mole skin cancer. 

On October 16, Professor Shiyong Wu spoke about the effects of UV radiation at a Science Cafe for Ohio University. 

Wu, Director of the Edison Biotechnology Institute at Ohio University, has been published 30 times over the past five years with seven studies directly relating to UV radiation. Wu holds a Ph.D. in Chemistry from the University of Nebraska and is a professor of chemistry and molecular cellular biology at OU. Currently, Professor Shiyong Wu is studying how cells become resistant to UV radiation. 

Professor Wu began the Science Cafe by informing the audience of UV-B rays. UV-B radiation reaches deeply into the skin, affecting the epidermis and a portion of the dermis. These harmful rays can even affect gene replication. 

“UV-B wavelengths are perfect for your DNA to absorb,” Wu said.

Wu’s statement posed an important question: How do our bodies “absorb” cancer-causing UV rays? 

When considering this question, it is important to note that human DNA has four bases. These bases are Adenine (A), Cytosine (C), Guanine (G), and Thymine (T). Typically, they are bonded together in a specific pair; adenine bonds to thymine while guanine bonds to cytosine.

“Your DNA gets excited when it absorbs UV-B light, much like when people get drunk,” Wu said. 

When UV radiation excites DNA, the DNA recombines itself and bonds in the wrong way.  For example, thymine would become bonded to another thymine. When DNA replicates, this bond can go unrecognized and will continue to reproduce incorrectly. 

But don’t worry yet. Skin covers the entire body and this mutation may only become an issue if it occurs in a gene that is crucial for survival. 

“If a genetic mutation occurs and the gene progresses, [the body] can use a suicide method and kill the cells, just like a virus,” Wu said. 

In order to avoid harmful skin complications, Professor Shiyong Wu encouraged the audience to avoid tanning beds, wear hats and use sunscreen. Wu suggested choosing a sunscreen that contains zinc oxide as a main ingredient.  

According to the Environmental Working Group, sunscreens containing zinc oxide do not break down near as easily as other active ingredients may. Even though no single-method of sun protection is 100 percent effective, zinc oxide’s protectant abilities make it a top sunscreen ingredient. Other active ingredients, such as oxybenzone and formaldehyde, can cause harmful effects to newborns as well as oceanic ecosystems. These chemicals are why Wu hopes people pay attention to the ingredients in sunscreen. 

“More powerful chemicals can be passed along to a newborn by way of the mother’s milk,” Wu said. “These chemicals often can be strong enough to bleach a coral reef.”

Professor Wu informed the audience that even with sunscreen, UV rays can be absorbed into the body within a short amount of time. 

“Fifteen to 20 minutes in the sun can ultimately provide you with enough Vitamin D for a single day,” Wu said. Professor Wu suggested going outside more frequently in the weeks leading up to a vacation to a warmer climate. Increased sun exposure decreases shock to the body when it comes in contact with sunlight for a prolonged period of time. 

While only UV-A and UV-B affect people on Earth today, Wu warned the audience that the effects of climate change could bring the third type of UV radiation: UV-C. 

“UV-C is absorbed by the ozone layer, unless the ozone layer continues to be depleted,” Wu said. 

If UV-C enters the atmosphere, it has the potential to cause severe eye and sunburn damage. 

To close, Professor Wu made a final one final suggestion for the audience.

“Wear a hat,” he said. “Hats give you shade and help to protect against these harmful UV rays.”

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