Be Careful When Sheryl Crow Tells You To "Soak Up The Sun"

I'm always amazed when I think about the fact that a giant ball of gas about 93-million miles away can have such an impact on human health. In addition to all of the things it does peripherally to support human life, such as giving trees the energy they need to convert carbon dioxide into oxygen, the sun also gives our cells the energy needed to produce vitamin D. There may be other benefits too, but today I want to talk about the dangers.

I've already talked about heat related problems, like heat exhaustion and heat stroke, and that staring at the sun can lead to blindness, but I think it's important to also talk about a type of cancer that's preventable; skin cancer. It's the most common type of cancer in the US, and there are things you can do to lower your risk.

First, let's take a moment to geek out with physics and remember that light, while behaving like a particle, also behaves like a wave. And depending on the amount of energy associated with that light wave, it will fall someone on a light spectrum, from radio/microwave, to infra-red, to visible light, to ultraviolet, and then to X-rays and gamma rays. As the spectrum gets towards the ultraviolet end, the waves become shorter and the frequency becomes higher. Light anywhere on the spectrum can cause harm, but the higher intensity of the ultraviolet end makes that more dangerous. 

Higher energy types of radiation are called ionizing radiation. This means they have enough energy to remove an electron from (ionize) an atom or molecule. Ionizing radiation can damage the DNA (genes) in cells, which in turn may lead to cancer.

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The sun's ultraviolet (UV) waves are also broken down to UV-A, UV-B, and UV-C. With UV-C being the most dangerous to humans. Fortunately, our atmosphere blocks just about all UV-C from reaching the surface of the earth. Most of the UV-B is blocked by the atmosphere too, so the majority of the sun's UV rays that hit the surface of the earth are UV-A, and both UV-A and UV-B can cause cellular damage that can lead to cancer. 

UV rays damage cellular DNA, causing incorrect pairing, the base pairs cytosine and thymine pair with other cytosine and thymine instead guanine and adenine, respectively. These mismatches form bulges that tend to bend the DNA. Over time, these damaged DNA segments can lead to cells growing out of control, and then cancer. 

Skin cancer manifests as either basal cell cancer, squamous cell cancer, or melanoma. Basal and squamous are more common, while melanoma is less common, but more serious. 

Images from UpToDate

Bottom line, you can take steps to prevent skin cancer, or at least severely reduce your risk, so why wouldn't you?

Some of the recommendations to reduce your chances of getting skin cancer are hard for outdoors people to achieve. You can't always be in the shade, nor can you avoid the time of the day when UV rays can be the most intense (10a-4p).

But you can cover up, be that with clothing or sun screen. 

I am, admittedly, not very good at remembering to wear sunscreen, much to my wife's chagrin. But I do try to wear loose, long sleeve jerseys, wide brim hats, neck buff, or other things to keep those UV rays at bay. 

Other times, sunscreen it is. You can find plenty of advice to help you choose the best option, but the TL:DR is to use one that has at least SPF 30, protects against both UV-A ad UV-B, and has some level water resistance. 

Whatever one you choose, apply liberally to all areas that are exposed to the sun, and re-apply every two hours or so. When I *do* remember to put on some sunscreen, I sometimes look like a glazed donut, but I usually do that just to annoy my wife. 

One final note, if you're going to be somewhere near coral reefs (Hawaii, etc), certain sunscreens are banned because the chemicals can damage marine life, so keep that in the back of your mind. And while you're there, put some sunscreen on the back of your neck.

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