Excessive exposure to UVR leads to skin burns and pigmentation, as well as to long-term effects: accelerated skin aging, the development of precancerous and neoplastic lesions, and the triggering of specific immunosuppression.​

UVB rays make up about 5% of all ultraviolet rays, but their biological effects are more pronounced than those of UVA.​

The highest intensity of UVB is in the afternoon hours, while the intensity of UVA remains constant throughout the day.​

UVA rays pass freely through car and window panes, which are UVB impermeable.