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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.
The periodic (daily) exposure to sunlight generally tunes the circadian rhythm to a 24-hour cycle. However, exposure to light sources that excite melanopsin in the retina during nighttime can interfere with the circadian rhythm. Harvard Health Publishing asserts that exposure to blue light at night has a strong negative effect on sleep. [17]
The ultraviolet radiation in sunlight has both positive and negative health effects, as it is both a principal source of vitamin D 3 and a mutagen. [48] A dietary supplement can supply vitamin D without this mutagenic effect, [49] but bypasses natural mechanisms that would prevent overdoses of vitamin D generated internally from sunlight.
Sunlight, especially its ultraviolet radiation component, can cause increased or additional types of damage in predisposed individuals, such as those taking certain phototoxic drugs, or those with certain conditions associated with photosensitivity, including: Psoriasis [5] Atopic eczema [5] Mastocytosis; Mast cell activation syndrome ...
Sunburn effect (as measured by the UV index) is the product of the sunlight spectrum (radiation intensity) and the erythemal action spectrum (skin sensitivity) across the range of UV wavelengths. Sunburn production per milliwatt of radiation intensity is increased by nearly a factor of 100 between the near UVB wavelengths of 315–295 nm.
Here, the path of sunlight through the atmosphere is elongated such that much of the blue or green light is scattered away from the line of perceivable visible light. This phenomenon leaves the Sun's rays, and the clouds they illuminate, abundantly orange-to-red in colors, which one sees when looking at a sunset or sunrise.
Global dimming is a decline in the amount of sunlight reaching the Earth's surface. [2] [3] It is caused by atmospheric particulate matter, predominantly sulfate aerosols, which are components of air pollution. [4]
Sungazing is the unsafe practice of looking directly at the Sun.It is sometimes done as part of a spiritual or religious practice, most often near dawn or dusk. [1] The human eye is very sensitive, and exposure to direct sunlight can lead to solar retinopathy, pterygium, [2] cataracts, [3] and potentially blindness.