The sun is essential to life. However, overexposure to sunlight can affect your health. Sunlight gives off a type of radiation called ultraviolet (UV) radiation. The International Agency for Research on Cancer (IARC) classifies UV radiation as a cancer-causing agent. Skin cancer is the most common cancer in the United States. Exposure to UV light causes most cases of melanoma, the deadliest kind of skin cancer. Learn more about skin cancer.

The Tracking Network includes data on exposure to sunlight and UV in the United States. These data can be used to identify regions of high exposure and to track trends over time. To learn more about the data sources, see Tracking Sunlight and UV.