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March 20, 2015 | By:  Samantha Jakuboski
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Dangers of the Sun

When I walk into a room, my friends and family know without even looking up that I have entered. It’s as if they can sense my presence. And, in an odd way, they can—with their noses. Just as my roommate always smells of Narciso Rodriguez perfume, my grandma of Chanel No. 5, and my dad of Kiehl’s Facial Fuel lotion, I have my own luxurious and posh scent that people instantly recognize: SPF 70 sunblock. Every day, whether it is the middle of February or the hottest day in August, I slather a generous amount of sunblock all over my face, neck, ears, arms and other exposed parts of my body. My friends call me fanatical, but I prefer the term prepared. With freckles and very light skin and eyes (my Sicilian genes have abandoned me in this respect!) it is an absolute necessity for me to shield myself from the sun. In fact, it is an absolute necessity for darker-skinned people as well, including my olive-skinned paesani, to take precaution before going out into the sun. From skin cancer to cataracts to wrinkles, the health problems caused by the sun are threats to people of all skin colors, and so it is important for everybody to take the sun seriously, especially now with spring finally here. As the warm months come and we spend more time outside enjoying the beautiful weather, no longer bundled up in long winter jackets, more skin will be exposed to the sun and for longer periods. Additionally, even though it may not be sweltering hot right now (in fact, it is snowing as I write this!), the UV radiation is intensifying as we get nearer to summer, and so the risks of getting sunburn and skin damage are increasing.

In writing this post and highlighting some of the main sun-induced skin maladies, I hope to make you all fanatical prepared like me when it comes to the sun so that you can continue to have healthy, youthful, and cancer-free skin well into old age.

What Makes the Sun So Harmful?

Two words: ultraviolet (UV) radiation.

This type of energy is so harmful to our heath that the United States Department of Health and Human Services and the World Health Organization declared it a carcinogen, especially of the skin (it cannot penetrate deep within the body’s tissues and organs). Depending on the wavelength of the UV radiation emitted, it can be classified as UVA, UVB, or UVC radiation.

UVA radiation, the A of which stands for aging, has wavelengths between 320 and 400 nm that can penetrate the deeper layers of the skin. It is responsible for aging, skin cancer, and wrinkles. Since the ozone layer barely absorbs it, UVA radiation accounts for 95% of the UV radiation that hits the Earth.

UVB radiation, the B of which stands for burning, has wavelengths between 320 and 290 nm and is mostly trapped by the ozone layer. It makes up the remaining 5% of the UV radiation that hits the Earth. UVB radiation is responsible for the production of vitamin D in our bodies, but overexposure to this radiation causes damage to the skin, mostly the top layer, resulting in skin cancer, sunburns, and even cataracts. In recent years, due to ozone layer depletion, more UVB rays have been reaching the Earth, and such increases are correlated with an increase in skin cancer.

Lastly, UVC radiation, which has the shortest wavelengths between 290 and 100 nm, and hence the highest energy, is the most harmful of the three radiations. Luckily this radiation is blocked almost completely by the ozone layer.

Changes in UV Intensity

Throughout the year, and even during the day, the strength of UV radiation changes due to many factors. During the spring and summer, the tilt of the Earth’s axis positions us (the northern or southern hemisphere, depending on where you live) in such a way that we are "pointed" more toward the sun. This allows for a more direct path for the sun’s UV radiation through the atmosphere, causing it to be very strong when it hits the Earth. However, for places near the equator with very low latitudes, the sun is mostly always directly overhead (independent of the Earth's tilt), leading to a shorter path the UV radiation has to travel and increasing its intensity.

The amount of UV radiation also varies depending on the time of day it is. When the sun is high in the sky between 11AM and 1PM, the distance the UV radiation has to travel to reach the Earth is the shortest for that day, and so, the UV radiation is the strongest. In fact, almost one third of the UV radiation that hits the Earth in a day occurs during these two hours. Additionally, UV radiation is more intense as altitude increases, as cloud cover decreases, and as the ozone layer depletes, because it encounters less barriers that can block it.

UV Index

According to the Environmental Protection Agency, one way to estimate just how strong the UV radiation is at a particular time during the day is by looking at your shadow. According to this Shadow Rule, if your shadow is shorter than you are, the sun is high in the sky and so the intensity of the UV radiation is strong. However, if your shadow is taller than you are, the sun is not very high up, and so the UV radiation that is reaching you is not at its strongest level.

Luckily however, there is a more accurate way of determining the intensity of UV radiation at a given place and time than staring at your shadow. Enter the UV Index. This index is a scale that ranges from zero (low UV radiation strength) to eleven and over (very high strength), and it allows people to take the precautions needed before going out into the sun. Have you ever gotten a UV alert on your phone or seen an alert on the morning news? Well, this is based on the UV levels and is issued when the UV Index reading in your area is a six and above or is exceedingly high for your region during that time of year. When I was a summer camp counselor a couple years back, we always heeded to these UV alerts and limited our little four-year old campers’ playtime outside to less than twenty minutes. When the UV radiation is that intense, people are more likely to burn quicker and get skin damage.

Click here to find out your current location’s UV level. You can also find the UV level for the day in your local newspaper and on the radio.

Vitamin D

We all have been told that exposure to the sun is beneficial for our bodies, since the UV radiation, specifically UVB radiation, allows our bodies to produce vitamin D. However, there is a limit to how much sun is good. Most sources, including the National Institutes of Health, advise that lighter-skinned individuals should get between ten and fifteen minutes of sunlight at least three times a week, during which they should not be wearing sunblock*. Darker-skinned individuals may need ten times this amount to produce the same amount of vitamin D since their skin has high melanin levels, and hence more protection against the UV radiation. However, these times are simply estimates, because depending on ones specific skin tone, the UV Index of a particular place, and how much skin is exposed, the time needed to produce the right amount of vitamin D will vary. It is also important to note that staying in the sun for longer periods than the recommended time does not provide any additional health benefits. Instead, it can actually destroy the vitamin D produced and cause skin damage.

*Side note: If you are crazy overly prepared like me and refuse to walk out of the house without sunblock, you can simply eat foods rich in vitamin D, such as egg yolks and fortified milk, and take vitamin supplements to get the necessary dosage each day to stay healthy. This way of obtaining vitamin D is actually suggested by many doctors.

Health Effects of Ultraviolet Radiation


From blisters on the verge of popping, to itching, peeling skin, the consequences of sunburns can leave us in pain for days. Formally known as erythema, sunburn is the body's response to UV radiation exposure. When UVB radiation hits the skin, the cells of the skin die and parts of their non-coding micro-RNA become damaged and break. The body's neighboring cells detect such RNA damage and set off a series of reactions to inflame the skin around the dead cells. This inflammation, which we call sunburn, allows the skin to heal by removing the dead cells and cells that may have undergone genetic mutations due to exposure to the UV radiation. As discussed later in the section Sun and Skin Cancer, such mutations are the basis of cancer formation. The removal of dead and possibly cancerous cells is what causes our skin to peel.

Although sunburns may just seem like an uncomfortable, short-term effect of overexposure to the sun, it actually has many long-term implications for people's health. Just one severe sunburn in childhood, or five sunburns throughout a person life, doubles a person's risk of developing skin cancer, specifically melanoma, in later life. Therefore, it is critical to shield our children from the sun from Day 1 and to continue protecting ourselves from the sun as we age. Time to put (throw) away the tanning oil and pull out that SPF 50!

Fun Fact: Do not be fooled by cloudy days and think that it is okay to leave the house without any sun protection. Even on days of light cloud cover, 80% of UVB rays can still reach the Earth's surface, and you can still get sunburn and skin damage.


Unfortunately, in spite of the pain caused by sunburn and the increased risk of developing cancer, many people refuse to part from their Hawaiian Tropic Dark Tanning Oil. In fact, a lot of my friends pride themselves on their rosy checks and their very distinguishable tan lines after a long day of lying on the beach, because they know, or at least hope, that the next color after the lobster-red stage is that prized and popular tan complexion.

So what exactly causes this tan that everybody nowadays yearns for?

It all starts with the pituitary gland, which releases melanocyte-stimulating hormone (MSH) in response to UV radiation exposure. MSH triggers special cells called melanocytes to produce more melanin, the skin's pigment that absorbs UV radiation and hence protects the skin. Therefore, in stimulating the production of more melanin and darkening the skin, the body is able to create a shield that will protect the skin the next time it is exposed to high amounts of UV radiation. However, some lighter-skinned individuals, such as myself, are not as receptive to MSH, and so do not have high levels of melanin. Therefore, it is hard for us to tan, we have less protection against the sun's UV radiation, and we are more prone to getting sunburn and developing skin maladies, such as skin cancer.

Are tanning beds a safer alternative to the natural sun?

Absolutely not!! Just as the sun’s UV radiation was named a carcinogen by the United States Department of Health and Human Services and WHO, tanning beds have been categorized as “carcinogenic to humans” by the International Agency on Cancer. Tanning beds lead to the same maladies caused by the sun because they, too, emit UVA and UVB radiation. Furthermore, people who start using tanning beds before the age of 35 are 75% more likely to get melanoma than people who never use tanning beds. Another study found that women who go to tanning salons more than once a month are 55% more likely to develop melanoma. With over one million people, mostly teen girls and young women, using tanning beds every day, it is so important that awareness is spread of the dangers of using tanning salons. If I had the power, I would shut down all the tanning salons in the country, because they truly are dangerous “cancer inducing factories.”

Sun and Skin Cancer

With over one million diagnoses each year, skin cancer has become the most common cancer in the United States. The three most diagnosed forms of skin cancer are basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma (for information on the rarer skin cancers, click here). BCC and SCC, called non-melanomas, account for over 3.5 million skin cancer diagnoses each year. Luckily, these two types of cancer seldom metastasize, and treatment for them has increased over the years.

Melanoma, on the other hand, is a much more dangerous type of skin cancer, resulting in 9,900 of the 13,000 deaths caused by skin cancer each year. Melanoma begins when melanocytes undergo uncontrolled cell division and form a tumor. In contrast to BCC and SCC, which usually form in an area of the body that had experienced prolonged sun exposure, melanoma can result from just one really bad sunburn and exposure. (Yes, I know I already stated that fact in the previous section, but it is one that needs to be stressed and repeated!) Additionally, melanoma is different from BCC and SCC because it is known to metastasize and spread throughout the body, increasing the severity and harmful effects of the cancer. It is projected that in 2015 alone, over 73,000 new cases of melanoma alone will be diagnosed.

So how exactly does ultraviolet radiation cause skin cancer?

UV radiation has high energy, and so exposure to this radiation causes damage to our cells' chromosomes and mutations in our DNA. One common mutation is the alteration and breakage at a point in the chromosome that codes for a specific tumor suppressor gene. Such tumor suppressor genes are important in regulating the cell cycle, and if such a gene, such as TP53, loses its function, it may result in the cell's uncontrolled cell division. As the cell and its progeny cells, which also contain the mutation, continue to divide uncontrollably, a mass of cells, or a tumor, can form. Other common mutations in DNA caused by exposure to UV radiation are the translocation of chromosomes and the alteration of nucleotide base pairs in the promoter or the coding section of a gene. These mutations can cause a normal proto-oncogene to become an overactive oncogene, and result in uncontrolled, rapid division of the cell. However, it is important to note that one mutation is rarely the cause of cancer development. Rather, cancers usually form due to an accumulation of gene mutations, through what is known as the multistep progression of cancer.

The mutations mentioned above are just some of the changes UV radiation can have on our cells' DNA, but as you can see, even slight mutations can greatly alter the functioning of a cell and have massive impacts. Due to such mutations in DNA, ultraviolet radiation from the sun accounts for 86% of all melanoma cases and 90% of SCC and BCC cases. I find it extremely unsettling that these cases can be prevented if people stay out of the sun or use sun protection. Such statistics show that we, as a society, need to increase awareness that the sun is a carcinogen and is dangerous for our health. Of course, other risk factors must be taken into account when analyzing patients diagnosed with skin cancer, such as family history, the fairness of ones skin, medical treatments such as organ transplants, and exposure to chemicals, but it is clear that the rate of skin cancer can decrease if people become more aware of the dangers of the sun and act accordingly by taking the proper precautions before going outside.

Ultraviolet Radiation and the Eyes

Not only is skin exposure to UV light harmful for our skin, but it is also very dangerous for our eyes, especially for people with blue or very lightly colored eyes. Just like skin, the eyes can get burned by short-term exposure to UVB radiation. In what is known as photokeratitis, the cornea becomes burned and inflamed, and in photoconjunctivitis, the conjunctiva (inner surface of the eyelids) is burned. Luckily, “sunburn of the eyes” does not seem to have any detrimental long-term affects on eye health. However, this is not to say that UV radiation does not have long-term affects on the eyes. Eyes exposed to UV radiation over a period of time are more prone to cataracts (the clouding of the eye lens), damage to the retina, and macular degeneration, which can lead to blindness. Additionally, long-term exposure to UV radiation is even linked to melanoma of the eye.


After discussing cancer and eye maladies caused by exposure to the sun, it may seem silly to talk about the consequences of sun-induced aging, such as wrinkles. Still, I think it is very important to understand the full spectrum of effects that the sun can have on our health and bodies.

The same culprit that causes skin cancer and the eye problems discussed above is responsible for sun-induced aging: UV radiation. When exposed to UV radiation, the collagen and elastin fibers in our faces break down, thus reducing the flexibility of the skin. As the flexibility of our skin decreases, the face starts to sag because it can no longer “snap back” when pulled or stretched. Hence, sagging and wrinkles. According to a study published in Clinical, Cosmetic, Investigational Dermatology, 80.3% of wrinkles and other sun-caused skin aging is due to UV radiation! (However, I would take this study with a grain of salt considering that L’Oreal, a cosmetics company that sells many skin care products including sunblock, commissioned it.)

Of course, cancer is my number one concern when it comes to the health effects of the sun. Still, I hope I don’t sound superficial when I say that I refuse to get premature wrinkles due to sun-induced aging. If this means staying out of the sun and slathering my face with sunscreen five times a day, so be it. I know that wrinkles are a natural sign of aging-- and that is totally honorable since they are a sign of a long life, full of wonderful experiences and memories-- but why should I prematurely loosen the connective tissues of my face when that can be postponed to when I am older (preferably when I am ninety/ ninety-five)? Unlike the wrinkles of the Chinese Shar-Pei above, which are not caused by the sun and are absolutely adorable, I personally do not see the allure of having lines running down my face and neck before I enter into old age!*

*My friends always tease me that I will be the first one to get wrinkles since I am the most impassioned about skin protection. Now wouldn’t that just be unfortunate?

Now knowing the dangerous effects of the sun, do I still seem as paranoid as I first did in the introduction? Of course I am not saying that people should be nocturnal and not go out during the day. Now that’s fanatical. Instead, I am saying that sun exposure should be limited, whether by wearing sunblock every day, sun protective clothing, or even a hat and big sunglasses. In my next post, I will write about some of my favorite sun style tips that allow me to have fun in the sun, while being safe and protected from UV radiation. Shielding yourself from the sun doesn’t have to be time-consuming, laborious, or nerdy-- trust me.

What are your views on the dangers of the sun? Do you agree that the sun is one of the most dangerous carcinogens facing people today, or do you think I am just too fanatical? What kind of sun style tips would you like in my next post?

Please share your thoughts below.


ASK THE EXPERT: Is Sun Exposure the Only Cause of Skin Cancer.” Skin Cancer Foundation. n.d

Barrymore, John “How Does the Sun Affect People With Dark 20 August 2009

Brain, Marshall “How Sunburns and Suntans 1 April 2000

Facts about Sunburn and Skin Cancer.” Skin Cancer Foundation. n.d

Indoor Tanning: The Risks of Ultraviolet RaysUnited States Food and Drug Administration. 21 January 2015

Make Vitamin D, Not UV, a Priority.” Skin Cancer Foundation. n.d.

Melanocyte-Stimulating Hormone.” Society for Endocrinology. 24 October 2013

Melanoma/Skin Cancer Health Center.” WebMD. n.d

Ozone and UV: Where We Now.” Skin Cancer Foundation. n.d

Skin Cancer Facts.” American Cancer Society. 2 February 2015

Skin Cancer Facts.” Skin Cancer Foundation. 9 February 2015

Skin Cancer: Who gets and Causes.” American Academy of Dermatology. n.d

SunburnWebMD. n.d

The Known Health Effects of UVWorld Health Organization. n.d.

Understanding UV Radiation and the UV Index.” The Leeds, Grenville & Lanark District Health Unit. n.d

UV Alert United States Environmental Protection Agency. 5 December 2011

UV Index.” United States Environmental Protection Agency. 5 February 2015

UV Index Scale.” United States Environmental Protection Agency. 5 February 2015

UV Protection: Protecting Your Eyes From Solar Radiation.” American Optometric Association. n.d

UV Radiation.” Environmental Protection Agency. June 2010

UV Radiation.” World Health Organization. n.d

What is UV Radiation.” American Cancer Society. 30 May 2014

Wrinkles Causes.” Mayo Clinic. 21 October 2014


Hertz, P., McMillan B., & Russel, P. (2014). Biology: The Dynamic Science. Belmont, CA: Cengage Learning, 360-363

Published Studies:

Bernard, J., Cowing-Zitron C., Nakatsuji, T., et al. (2012). Ultraviolet radiation damages self noncoding RNA and is detected by TLR3. Nature Medicine, 18, 1286-1290.

Flament, Frederic et al. (2013) “Effect of the Sun on Visible Clinical Signs of Aging in Caucasian Skin.” Clinical, Cosmetic and Investigational Dermatology, 6: 221–232.

Gruijl, F. (1990). Skin Cancer and Solar UV Radiation. European Journal of Cancer, 25: 2003-2009

Henriksen, T., Dahlback, A., Larsen, S. H.H. and Moan, J. (1990), ULTRAVIOLET-RADIATION and SKIN CANCER. EFFECT OF AN OZONE LAYER DEPLETION. Photochemistry and Photobiology, 51: 579–582.

Hussien, Mahmoud. (2005). Ultraviolet Radiation and Skin Cancer: Molecular Mechanisms. Journal of Cutaneous Pathology, 32: 191-205.

Picture Credits:

Grabbing the Sun: Yaniv (via flickr) and available for use under the CC license

Sunburned Boy: Erin Stevenson O’Connor (via flickr) and available for use under the CC license

Chinese Shar-Pei: Big Tiger (via flickr) and available for use under the CC license

Eye: Kev-Shine (via flickr) and available for use under the CC license

April 23, 2015 | 10:36 PM
Posted By:  Samantha Jakuboski
Thanks for sharing the poster, Ilona! It was interesting to learn that most melanoma-casuing mutations, which result in uncontrolled cell division, are those that affect the p16INK4A–CDK4/CDK6–RB pathway.
April 23, 2015 | 06:20 PM
Posted By:  Ilona Miko
Thanks for all the info! Here is a poster about melanoma from NPG's Nature Reviews Disease Primers. It might be interesting to readers?
April 11, 2015 | 12:17 PM
Posted By:  Ahmed ELsheikh
What is best time FOR EXPOSURE TO sunlight?,I have heard that the best time is from 9.30 am to 11 am .


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