The ducks are skating on the ice and the temperature outside is dropping faster than the snow. It might be difficult to imagine now but, sooner or later, summer is coming. And with that longed-for season comes the age-old desire to worship the sun — and with that comes the inherent danger of overexposure.
Sunburn can be serious — in 2007, the Centers for Disease Control (CDC) published results that consistently showed more than 50 percent of those involved in randomized population studies reported getting some form of sunburn in the previous 12 months. More alarming is new research, led by Dr. Sanjay Premi of Yale's Department of Therapeutic Radiology, which suggests that even once we're out of the sun, we may not be safe from its harmful rays.
People with red or blond hair seem to suffer most with sunburn, but even those with dark hair are at risk if their skin is pale. The skin has its own method of protection: melanin. When exposed to ultraviolet (UV) light, cells in the skin — called melanocytes — produce melanin. This darkens the skin preventing damage to its deeper layers. The longer you sit there, the more melanin you produce and, theoretically, the deeper your tan. Sounds good, right? Well, not quite.
Though some prefer a healthy tan, it is extremely important to keep in mind the risk to health. The UV rays that penetrate the skin cause damage to DNA, which can ultimately result in skin cancers. According to the American Cancer Society (ACS), more than 3.5 million cases of skin cancer are diagnosed every year. Of the cases diagnosed in 2015, says the ACS, 73,000 will be melanomas — cancers that begin in the melanocytes. And at the top of their list of risk factors is overexposure to harmful UV radiation, whether from artificial or natural light.
The dangers of repeated exposure to the sun have been known a long time. Now, according to the study at Yale, the damage done doesn't stop once you step into the shade. Darkening by melanin doesn't prevent all UV getting through — hence the progressive deepening of the tan — and, during a "second wave" of damage, the melanocytes themselves can be adversely affected.
When exposed to UV light, the cells produce two enzymes that chemically combine and release energy. "This energy," says the study, "is then transferred to DNA, inducing the same damage as ultraviolet light, but in the dark."
The damage done to skin is caused by tiny, complex "DNA photoproducts" called CPDs. According to the team, these "are typically created picoseconds after an ultraviolet photon is absorbed." More importantly, "CPDs are created for more than three hours after exposure to UVA," a form of ultraviolet light that is "a major component of the radiation in sunlight and in tanning beds."
In other words, though immediate exposure produces melanin that ostensibly protects the skin, damage to the melanin-producing cells themselves goes on for much longer. "Melanin," says Douglas E. Brash, another of the authors of the new paper, "may thus be carcinogenic as well as protective against cancer."
Previously, says Brash, it was believed that cancer-causing damage to the skin was produced by direct exposure to sunlight, "but then you look at countries like Egypt, where many people have fairly light skin tones, and there isn't the high skin cancer incidence you'd expect." The immediate effect of sunlight exposure was clear, but the secondary effect on melanin-producing cells was unknown, possibly because it can take hours to happen.
It is hoped, in the long run, that sunscreen can be adapted to compensate for this effect. "Conceivably," the study says, "this energy could be dissipated by adding quenchers to sunscreens." These "quenchers" would deflect the damaging power of the CPDs away from the melanin and offer greater protection.
In the meantime, the advice remains the same. "There is no such thing as a healthy tan," says the National Center for Biotechnology Information. Stay out of the sun during the harshest periods — between 10 a.m. and 2 p.m. Cover up, wear a hat, slip on some shades and always, always wear sunscreen. Though melanoma is the most aggressive form of skin cancer and accounts for the greatest number of deaths, it is important to remember that it is "almost always curable when it’s found in its very early stages," says the ACS. Remember to follow their advice for protection and detection when it's finally time to have some fun in the sun.
It may feel like Siberia out there right now but once summer gets here, it will have the power to be just as harsh as this winter has been. Be ready for it.