Running from the sun. UV light is the most preventable risk factor for all skin cancers. The sun emits two types of ultraviolet rays–UVA and UVB. Both kinds of radiation can lead to skin cancer. Runners and others who like to be outdoors are especially at risk, particularly when the sun is high and their, face, arms and legs are bare. And, during many endurance events such as marathons and triathlons, competitors often spend time in the sun when ultraviolet rays are strongest–between 10 a.m. and 4 p.m. We encourage everyone to protect their skin in a way that suits them best. For example: 1.Use sunscreen with SPF 30 or higher 2.Wear protective clothing (such as a cap) 3.Seek the shade 4.Go out when the UV rates are lowest.