Helios, the sun god in Greek mythology, rode a chariot across the sky, east to west, sunrise to sundown, year round, as dusk bestows silvery moonlight accompanied by stars that extend to infinity followed by dawn that welcomes renewing sunlight.
The sun is not always reflected as gentle and rosy. The sun can get stupendously stormy and frightfully tempestuous. The phenomenon, none less, is called 鈥渟olar storm鈥�.
Solar storm kicks off with an explosion above a sunspot, according to NASA. Sunspots are defined as sites where magnetic fields strive through the sun鈥檚 surface. These unstable exploding magnetic fields are so powerful, first sending off a 鈥渟olar flare鈥� followed by emitting high-energy particles (protons that are packed together with neutrons in the nucleus of atoms) the magnitude of 10 billions hydrogen nuclear bombs. One such solar storm took place in 1972, blissfully between two NASA missions of Apollo 16 and Apollo 17, so unimaginable devastations to the astronauts and the space vessels were narrowly avoided.
Ultraviolet rays from the sun cast harmful rays on earth undramatically, unannounced, with no visible fanfare. Ultraviolet rays, abbreviated as UV rays, are a form of electromagnetic (EM) radiation. Radiation is classified by wave length and frequency on the EM spectrum. The shorter the wave length, the higher the frequency, and the higher the energy. Examples of high-energy radiation include alpha, beta, gamma, and X rays. Radiation can also be of low energy (such as radio waves). UV lies between high- and low-energy radiation.
UV rays are classified by three types: UVA (95%), UVB (5%), and UVC. Both UVA and UVB rays can penetrate the outmost layer of skin called epidermis and both are linked to skin damage and increased risk of skin cancer, in addition to compromising human immune response. UVC is the most energetic hence, potentially the most damaging. Fortunately, UVC gets filtered by the ozone layer of earth鈥檚 atmosphere. Where ozone layer is damaged, however, UVC will cast rays on earth and affect living organisms including humans. Gases (from refrigerants and aerosol spray ) released into the atmosphere break down ozone molecules and reduce ozone鈥檚 UV-filtering capacity.
UVs from the sun's high-energy rays can damage our DNA, leading to mutations which, if not corrected, can transform normal cells to cancerous cells over time. All three forms of UV rays are cancer-causing (carcinogenic). Artificial UV rays, such as UVA rays emitted in tanning stations, can be up to 12 times more UVA light than natural sunlight. The American Association of Dermatology (AAD) states unequivocally of the harmful effects of tanning stations on skin health especially for young people. The American Cancer Society (ACS) describes UV rays as a clear major cause of melanoma.
Why is melanoma so serious? There are three distinct types of skin cancer: Basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma. Although all three types have UV rays as the main culprit, not all skin cancers are the same. SCC is the second most common form of skin cancer in North America. Thanks to progress made, the majority of SCC is treatable.
Melanoma is a totally different story. Compared to other skin cancers, melanoma is much more serious and tougher with treatment. It is classified into four stages depending on severity and metastatic properties. To date, melanoma 5-year survival rate is 100% for Stage-1, 80% for Stage-2, 70% for Stage-3, but only 30% for Stage-4. Melanoma is malignancy arisen in melanocytes. Melanocytes reside in the skin, (also hair follicles, inner ear, and iris of the eye) and secret melanin. Melanin is a pigment, a complex polymer derived from tyrosine (one of 20 amino acids as the building blocks of proteins). Aside from determining skin color and hair color, melanin also shields the skin from the sun鈥檚 rays. Melanin levels increase in response to skin鈥檚 sun exposure, resulting in a tan. Extended exposure to the sun or artificial UV rays, however, renders inadequate amount of protective melanin to be produced, leading to a sunburn. UV-induced DNA breakage causes mutations in melanocytes, if the affected genes control cell growth and cell division, that means melanocytes would grow uncontrollably and overtime developing into melanoma. As a side note, melanomas of sun-exposure versus non sun-exposure involve different gene mutations. Befuddling but interesting. Elucidating unique mutation patterns could shed light on developing respectively targeted therapeutic strategies.
Does it mean one should avoid the sun at all costs and at all times? Nah. Direct sunlight helps convert a type of cholesterol in the skin to vitamin D, an important molecule involved in more than 300 biological and physiological activities.
How I miss keeping my chin up and eyes closed to soak up the warm sunlight as the chairlift snailing unhurriedly toward the summit of snow-covered Mont Tremblant!
Take-home message:
- The sun鈥檚 rays can be harmful but at the same time beneficial. Moderation is key.
Dr. Nancy Liu-Sullivan holds a Ph.D. in Molecular and Cellular Pharmacology and served as a senior research scientist at Memorial Sloan Kettering Cancer Center. She currently teaches biology at the College of Staten Island, City University of New York.
