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  • Dr. Rob Thiry

Skin cancer and sunscreen

Sun exposure, increased skin cancer, and sunscreen - you probably have many questions about these topics. Should we use sunscreen or should we avoid it? Is sun exposure actually good for me? With all the outdoor activities we enjoy in the Treasure Valley, it's important to have some facts in order to make the right decisions for both ourselves and our families.

The main type of radiation given off by the sun associated with skin cancer is Ultraviolet Radiation. It is broken down into three types:

  • Ultraviolet C (UVC): The most harmful of the three types, but almost completely absorbed by the ozone layer.

  • Ultraviolet B (UVB): Also absorbed by the ozone layer, but still able to pass through to the earth surface. UVB affects the outer most layers of the skin and may cause sunburn, cataracts, and immune suppression (genetic damage) that may lead to skin cancer. UVB also stimulates the production of vitamin D by the body.

  • Ultraviolet A (UVA): This type of radiation passes through the ozone layer and reaches the earth’s surface. It penetrates deeper into the skin can cause skin aging, damage to DNA, and leads to free radicals and reactive oxygen species that damage cells and lead to skin cancer.

According to the current research all three types of radiation are harmful and may lead to skin damage or even cancer. However, there is some research which shows certain amounts of sun exposure actually reduce the risk of sun cancer.

Vitamin D3 ( Cholecalciferol ) is a steroid that is produced when the skin is exposed to the UVB rays of the sun. Research suggests that Vitamin D3 is not only important in the repair of damaged tissue but may also be a potent cancer fighter. It may accomplish this by prevention and replication of these types of cells.

A 2011 research article by Dianne E. Godar, a chemist with the Food and Drug Administration, even suggests that indoor workers are as or more likely to develop melanoma than outdoor workers. The two main reasons are:

1) minimal sun exposure during the week and high concentrations of sunlight on weekends and holidays leading to an increased risk of sunburn and

2) working indoors where windows filter out the UVB rays which promote Vitamin D3 synthesis and allow all of the harmful UVA rays in for exposure.

The need for Vitamin D to promote healthy bones and tissues as well as the potential cancer fighting benefits exists, so the question arises why the increase in skin cancer cases over the past 25 years.

Is it that the ozone layer has deteriorated and more harmful rays are reaching the earth's surface? There are many articles that all seem to have different opinions. One article will say we are doomed; the next will say the ozone layer is regenerating; and, another says the whole thing is untrue. An article in the British Journal of Dermatology suggests the increase in cases of skin cancer is related to a new way of reporting, not an increase in exposure. The new way of reporting includes benign lesions as stage 1 melanoma. As a result lesions that in the past were not reported as cancer now are.

It gets to be a little confusing. Is sun is bad or good? Should I be indoors or outdoors? Is the ozone layer gone or is it just fine? In the end, it appears the general consensus is that a certain amount of sun is actually good and healthy, but over exposure may lead to abnormal skin aging and possible skin cancer.


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