The International Agency for Research on Cancer has listed ultraviolet light as a Class I carcinogen. 

1. Damage to the eyes. 

Intense ultraviolet radiation will first damage the cornea. When the local tissue cells of the corneal edge are irradiated by ultraviolet rays, the lipids of unsaturated fatty acids will undergo peroxidation reaction, causing cell damage, and the level of superoxide dismutase in corneal epithelial cells will decrease. Aldehyde levels increase and the homeostatic environment of corneal cells is disrupted. Secondly, after the lens is exposed to ultraviolet rays for a long time, the evenly distributed crystal chains will be interrupted and become irregular, resulting in reduced light transmittance of the lens, decreased vision, and even radiation cataracts. Finally, excessive ultraviolet radiation can cause damage to the macula of the retina, causing macular degeneration, which can lead to loss of vision in severe cases. 

2. Damage to the skin. 

At the molecular level, ultraviolet radiation can induce regulatory T cells to produce leukocyte differentiation antigens, and the activated regulatory T cells will inhibit the body's immune response. From the cellular level, ultraviolet rays can change the shape, distribution and density of epidermal cells, thereby affecting the immune system; ultraviolet rays can induce and inhibit the formation of T cells, thereby inhibiting the host's immune system and leading to the formation of immune tolerance; ultraviolet radiation can also activate B Cells, inhibit the activity of dendritic cells, thereby suppressing the immune system. 

3. Damage to the immune system. 

At the molecular level, ultraviolet radiation can induce regulatory T cells to produce leukocyte differentiation antigens and secrete immunosuppressive cytokines interleukins, and the activated regulatory T cells will inhibit the body's immune response. From the cellular level, ultraviolet rays can change the shape, distribution and density of epidermal cells, thereby affecting the immune system; ultraviolet rays can induce and inhibit the formation of T cells, thereby inhibiting the host's immune system and leading to the formation of immune tolerance; ultraviolet radiation can also activate B Cells, inhibit the activity of dendritic cells, thereby suppressing the immune system.