That radiation randomly damages the DNA in your cells—as if you’ve been shot with millions of tiny pins. (UV rays are borderline ionizing, which is why you can get skin cancer from tanning.) If ionizing radiation strips enough electrons from your DNA, or if you’re unlucky and it hits the wrong places in your genome, the genes that control cell growth can start to function abnormally. Certain cells divide out of control, causing tumors, leukemias, or other cancers. The risk is particularly high for children, whose cells have divided less often and are more likely to run amok if damaged.
