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Three questions about UV
Source: COMING | Author: COMING | Release time : 2021-07-22 | 93 Views: | 分享到:
Most natural UV light is generated by the sun with about ten percent of sunlight being UV and only about three to four percent penetrating the atmosphere to reach the ground. Of the UV radiation that reaches the earth, 95 percent is UVA and five percent is UVB.
No measurable UVC from the sun reaches the earth’s surface. Because of the spectral sensitivity of DNA, only the UVC region demonstrates significant germicidal properties.

What is UVC?

UV-C is one of many electromagnetic frequencies emanating from the sun.
Like other of these waveforms, its properties are unique to its wavelength.
Ultra-Violet (UV) light is invisible to human eyes.
It can be subdivided into three categories:
UVA, UVB and UVC. UV-A from 315 to 400 nm UV-B from 280 to 315 nm UV-C from 200 to 280

Is UV-C harmful

We’re exposed to parts of the UV spectrum while outdoors. Generally, excessive UV exposure can produce adverse effects depending on wavelength, type and duration, and UV response differences between individuals. 

The three basic wavelengths:

A. UV-C - includes the germicidal wavelength of 253.7nm and is used for air and water disinfection. Human overexposure causes temporary skin redness and harsh eye irritation, but no permanent damage, skin cancer, or cataracts.

B. UV-B - is a narrower but more dangerous band of UV. Prolonged exposure has been associated with skin cancer, skin aging, and cataracts (clouding of the lens of the eye).

C. UV-A - is more predominant outdoors than the other two. It helps to tan our skin and is used in medicine to treat certain skin disorders. It is generally a harmless wavelength. UVA, B and C will damage collagen fibers and accelerate skin aging. Generally, UVA is least harmful; UVB contributes to DNA damage and cancer. It penetrates deeply but does not cause sunburn. Because of no reddening (erythema) it cannot be measured in SPF testing. There’s no good clinical measurement of UVB blocking, but it is important that sunscreens block both UVA and B. UVC however, penetrates superficially and has not been associated with long term tissue effects.

How does UVC disinfection work?

As evident by multiple research studies and reports, when biological organisms are exposed to deep UV light in the range of 200 nm to 300 nm it is absorbed by DNA, RNA, and proteins.Absorption by proteins can lead to rupture of cell walls and death of the organism. Absorption by DNA or RNA (specifically by thymine bases) is known to cause inactivation of the DNA or RNA double helix strands through the formation of thymine dimers. If enough of these dimers are created in DNA, the DNA replication process is disrupted, and the cell cannot replicate.


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