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Sunbaker, by Max Dupain. Exposure of skin to ultraviolet radiation from sunlight presents both positive and negative health effects. On the positive side, UV exposure enables the synthesis of vitamin D 3, which is essential for bone health [1] and potentially plays a role in inhibiting certain cancers.
This effect is a response of the skin called erythema, which is caused by a sufficient strong dose of UV-B. The Sun's UV output is divided into UV-A and UV-B: solar UV-A flux is 100 times that of UV-B, but the erythema response is 1,000 times higher for UV-B. [citation needed] This exposure can increase at higher altitudes and when reflected by ...
The atmosphere blocks about 77% of the Sun's UV, when the Sun is highest in the sky (at zenith), with absorption increasing at shorter UV wavelengths. At ground level with the sun at zenith, sunlight is 44% visible light, 3% ultraviolet, and the remainder infrared. [26] [27] Of the ultraviolet radiation that reaches the Earth's surface, more ...
All UV frequencies have been classed as Group 1 carcinogens by the World Health Organization. Ultraviolet radiation from sun exposure is the primary cause of skin cancer. [65] [66] Thus, at UV frequencies and higher, electromagnetic radiation does more damage to biological systems than simple heating predicts.
The ultraviolet radiation in sunlight has both positive and negative health effects, as it is both a requisite for vitamin D 3 synthesis and a mutagen. Sunlight takes about 8.3 minutes to reach Earth from the surface of the Sun. [ 3 ] A photon starting at the center of the Sun and changing direction every time it encounters a charged particle ...
Variations in the ultraviolet component. The UV component varies by more than the total, so if UV were for some (as yet unknown) reason to have a disproportionate effect, this might explain a larger solar signal. Effects mediated by changes in galactic cosmic rays (which are affected by the solar wind) such as changes in cloud cover.
Ozone depletion would magnify all of the effects of UV on human health, both positive (including production of vitamin D) and negative (including sunburn, skin cancer, and cataracts). In addition, increased surface UV leads to increased tropospheric ozone, which is a health risk to humans.
Sunburn effect (as measured by the UV Index) is the product of the sunlight spectrum at the Earth's surface (radiation intensity) and the erythemal action spectrum (skin sensitivity). Long-wavelength UV is more prevalent, but each milliwatt at 295 nm produces almost 100 times more sunburn than at 315 nm.