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What Every Runner Needs to Know About Sun Safety – Part 1:
UV Radiation Decoded
August 12, 2016 Lindsey N. Dyn
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Disclaimer: I am not a doctor of any kind. I never attended medical school. The information in this article was derived from a variety of resources which can be found in the References at the end of this posting. This article is meant as a vehicle for awareness and is not meant to be interpreted as medical advice.
We as runners spend a significant amount of time pounding the pavement (or trail) out in the sun. Summertime can be an especially dangerous time if you’re also trying to fit in those last few days of vacation or pool time. While society has trained (aka brainwashed) us to covet that dark, even tan, I beg you…resist that urge! Being sun-smart is not always the sexiest or most fun thing to do before starting your summer vacation, favorite hike, or day at the pool, but it’s critical to be up-to-speed on the various factors that influence our chances of accumulating additional sun damage (culminating in sunburns, or worse, skin cancer), and steps runners and non-runners alike can take to protect ourselves. Since August is Sun Safety Awareness and this is such an important topic, today’s blogpost is the first in a series addressing sun safety. We’re going to start off with the basics of UV radiation (and for easy navigating, I’ve also provided navigation links below).
This article also contains quite a few abbreviations and terms you may or may not be familiar with. I never like to see people confused, so below is a quick and dirty table listing some of the terms, abbreviations, and their meanings. Because I like to be helpful…so enjoy.
What is UV radiation?
This first part is going to be a little technical, a bit of a throw-back to your high school science days, but we have to cover it for good reason. So what in the heck is UV radiation? Ultraviolet radiation, abbreviated UV for short, is a type of energy with a specific range of wavelengths on the electromagnetic spectrum. Think of the electromagnetic spectrum like a scale. At the low end of the spectrum reside radio waves, with extremely long wavelengths measured in meters (m), and at the high end, gamma waves, measured in fractions of a nanometer (nm). The higher you travel toward the right on the spectrum (toward gamma waves), the shorter the wavelengths and greater the energy levels become. (1, 3)
UV radiation deals with energy that has wavelengths which fall within the 100 – 400 nm range of the electromagnetic spectrum. UV radiation is further divided into discrete categories based on wavelength: UVA (wavelengths between 315 – 400 nm), UVB (wavelengths between 280 – 315 nm), and UVC (wavelengths between 100 – 280 nm) (3). As a point of reference, what we term the visible light portion of the electromagnetic spectrum has wavelengths ranging from approximately 400 – 800 nm. (1, 3)
Why is this important? It all comes down to energy. Light with the highest energy has the greatest potential to be damaging. (3) So looking at what we previously covered, shorter wavelengths of light are higher in energy, and therefore are more damaging. From the references above, you can see UVC has the highest amount of energy, followed by UVB, and then UVA. For those of you so inclined to see the mathematical proof of this, click here.
By now, some of you may be confused about the uproar concerning use of ‘Broad Spectrum’ (UVA and UVB protective) sunscreen. You may be asking, ‘If UVB is more damaging than UVA, isn’t protecting against that enough? And why aren’t we concerned about UVC? It has the shortest wavelength (and highest energy) of all the UV radiation.’
So, there’s a little more to the UV story. Mother Nature has provided us with some built in protection: our ozone layer. Think of the ozone layer like a filter: letting certain energies through, and blocking others. All of UVC radiation, and the vast majority of UVB radiation is blocked from penetrating the atmosphere by stratospheric ozone. But there’s a bit of a catch. While UVA is less energetically damaging, more of it reaches the Earth’s surface – a lot more, actually. It’s estimated that at midday, approximately 95% of radiation is attributed to UVA radiation, with only 5% consisting of UVB radiation. (3) To complicate things, global climate change and the past use of CFC’s have slowly eaten away at the stratospheric ozone layer, diminishing some of it’s buffering effects, (3) and consequently exposing us to increased ultraviolet radiation levels, particularly UVB. (1)
What affects UV radiation?
The ozone layer is just one of many factors that contribute to the amount of UV radiation that you are subjected to. The infographic below provides an overview of some of the factors, while the table after that highlights the other major factors in a little more detail. (1)
Sources: (1, 3)
Factors Affecting UV Radiation Levels
Sources: (1, 3)
We’ve covered the basics of what UV radiation is and factors that can affect the levels you are exposed to, but why does this truly matter? In short, in addition to the uncomfortable visible sunburns, UV radiation also has more serious health consequences – cancer. (4) Next week’s article will take a more in depth look at the dangers of UV radiation and why you shouldn’t believe all the $@#! tanning companies are selling you.
Stay tuned for the next sun safety article and until next time, happy running!
1.) World Health Organization. Global Solar UV Index: A Practical Guide. 2002.
2.) U.S. Food and Drug Administration. Questions and Answers: FDA Announces New Requirements for Over-the-Counter (OTC) Sunscreen Products Marketed in the U.S. 2011. http://www.fda.gov/drugs/resourcesforyou/consumers/buyingusingmedicinesafely/understandingover-the-countermedicines/ucm258468.htm accessed 7/19/2016.
3.) International Agency for Research on Cancer. Solar and Ultraviolet Radiation. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, 100D 2012: 35-101.
4.) Sharfstein, J.M., A Spotlight on Sunscreen Regulation, N Engl J Med 2015; 373: 101-109 DOI: 10.1056/NEJMp1504912.