Before a day at the beach you may want to consider this: The interaction between the sun rays, our skin and our body is a complicated one. So much so that leaving the sun behind doesn’t stop its effects. According to a study published
Before a day at the beach you may want to consider this: The interaction between the sun rays, our skin and our body is a complicated one. So much so that leaving the sun behind doesn’t stop its effects. According to a study published in Science, skin damage continues 3 to 4 hours after you have gone inside.
What’s more, melanin—you may know it as the stuff that makes us tan and helps protect us from the sun—might fuel the process. “It [melanin] is doing good things and it’s doing bad,” says study co-author Douglas E. Brash, PhD, a clinical professor of therapeutic radiology and dermatology at Yale School of Medicine. At the most basic level, there are two types of melanin that make up our skin color—light and dark. Which way the ratio of the two goes, determines our skin cancer risk: Dark skin has less risk than lighter skin. “And that is all true, but that isn’t the whole story.”
For a long time there has been an increasing body of evidence that melanin may be causing a bit of havoc under its halo; however, those studies were done in test tubes or there were other effects that the melanin could have. The research that Brash and colleagues published helps put together the odds and ends of science’s findings about melanin.
The moment that an ultraviolet (UV) photon penetrates our skin it starts off a chemical reaction activating two enzymes whose chemical byproducts react with each other instantly creating a third chemical compound. “If melanin is nearby that substance can break the melanin down, dissolving it,” Dr. Brash explains. “It also starts off a chain reaction which ends up with two extra oxygens on the melanin in a square ring—it is very unstable with high energy and it isn’t going to last very long. It breaks.” Think about when planets blow up in the movies, that energy flies outward. Now imagine that the planet is melanin and DNA is next door. “The DNA absorbs the energy, and the result is the same as what we have always thought happened when a UV photon entered the skin, the energy is absorbed and it puts a bend in the DNA.” This process can continue for 3 to 4 hours after exposure to UVA or UVB rays.
And it is this bend that has a few outcomes—some toward skin cancer. That bend could prevent a cell’s DNA from being copied or signal it for programmed cell death. In both cases the cell dies. Another possibility is that the cell’s DNA is copied with a mistake, giving the daughter cell a mutation. “In that case at least the cell is not dying but you get a mutation. If that happens in an oncogene (a cell that can turn into a tumor cell) or a tumor suppressor gene then that cell can start on the way to skin cancer,” Brash says.
How do they know? This recent paper built upon research that Dr. Brash and his collea