Do you know that sun light could lead to skin cancer? Do you know that 90% of skin aging is by sun?
"Oh, it's a sunny day!" Do you love sunny days? Sunny days are the best time for you to hang out with your friends, go to the beach, and have a lot of fun! But wait a second! Will you use the sunscreen before going out? Have you wondered why do we need sunscreen at all? Have you ever wondered why the sunshine is dangerous for us?
Every day, our skin encounters with sun light. The same time that the sun lights our world, the same time it provides us the energy to generate electricity, but the sun also brings UV radiation (Ultraviolet Radiation).
Q1. What is UV Radiation?
The Sun itself is a source of the full spectrum of ultraviolet radiation, which could then be divided into three categories: UV-A, UV-B, and UV-C. UV-C is the most harmful one, but thanks to our atmosphere, it has almost been completely absorbed. UV-B is the one that causes you to get a sunburn. Fortunately, about 95 percent UV-B rays are absorbed by ozone in the Earth's atmosphere. And the one that finally reaches us: UV-A, which will penetrate deep into the dermis, the skin's thickest layer.  Both the U.S. Department of Health and Human Services and the World Health Organization have identified UV as a proven human carcinogen .
Why is it dangerous?
UV Radiation has always been seen as one of the reasons that will cause DNA damage. Because UV-A will be able to penetrate deep into the dermis, the skin's thickest layer, it will also reach our skin cells. One essential component of any cells is the genetic information, which is DNA in our body. When the UV Radiation reaches the DNA, it will generate bulky lesions, breaking the structure of the DNA that carries our genetic information. [as reviewed in 5] When there's damage, it will be hard for the cell to go through several processes, including DNA replication. Although repair mechanisms are acting as a guard, some errors will persist and may cause a serious problem --- Skin Cancer.  According to the research, an estimated 90 percent of skin aging is caused by the sun.  And each year in the U.S. over 5.4 million cases of nonmelanoma skin cancer are treated in more than 3.3 million people. 
So, what could we do to prevent skin cancer from happening?
Although the problem is serious, you don't need to panic, because some easy steps will help you to reduce your risk of getting skin cancer.
1. Check the UV index before going outside
The UV index in U.S has confirmed with international guidelines founded by WHO. Different UV index means different level and the amount of ultraviolet radiation. To learn more about what different UV index means on your health, click here to see what different indexes mean.
To check the UV Index at your current location, open the weather app on your iPhone. Scroll down to the bottom, and then you will be able to see the UV index option. (Note that this screen shot is taken at night, so there's of course no UV radiation)
2. Wear sunscreen protection
Sunscreen is like an extra layer of your skin and the UV Rays from the sun. Buy a sunscreen based on your needs, and always check for the ingredients to make sure you are suitable to use the product and it's safe to use for you (Ask your doctor for the advice). There will always be a number on your sunscreen starting with SPF (Sun Protection Facto). It means the level of protection, and the higher SPF value is, the more protection this sunscreen could bring to you. You should always check the UV index for the day and use the proper sunscreen with an appropriate SPF value.
These are the two tips to help you avoid skin cancer. Although our body will be able to fix most of the errors produced by UV Rays, it's always important to keep in mind that UV Rays could also lead harms to us, and to protect ourselves so we could be healthy.
(Maybe the best and the fanciest solution is Just at home with A.C on during the hot days!)
Enjoy your weekend!
: Taylor CR, Stern RS, Leyden JJ, Gilchrest BA. Photoaging/photodamage and photoprotection. J Am Acad Dermatol 1990; 22:1-15.
: Rogers HW, Weinstock MA, Feldman SR, Coldiron BM. Incidence estimate of nonmelanoma skin cancer (keratinocyte carcinomas) in the US population, 2012. JAMA Dermatol 2015; 151(10):1081-1086.
: Skin Cancer Foundation. UVA & UVB - SkinCancer.org. [accessed 2017 Jul 29].
: Does UV radiation cause cancer? American Cancer Society. [accessed 2017 Jul 29]. https://www.cancer.org/cancer/cancer-causes/radiation-exposure/uv-radiation/uv-radiation-does-uv-cause-cancer.html
: Novarina, D., Amara, F., Lazzaro, F., Plevani, P., & Muzi-Falconi, M. (2011). Mind the gap: Keeping UV lesions in check. DNA Repair, 10(7), 751–759. http://doi.org/10.1016/j.dnarep.2011.04.030
: How the sun and UV cause cancer. Cancer Research UK. [accessed 2017 Jul 29]. http://www.cancerresearchuk.org/about-cancer/causes-of-cancer/sun-uv-and-cancer/how-the-sun-and-uv-cause-cancer