UVA vs UVB as it applies to sun tanning
Nov 10, 2013 3:42:59 GMT -5
325i, Tanru, and 1 more like this
Post by aeroguy39 on Nov 10, 2013 3:42:59 GMT -5
An interesting passage I found on Wikipedia:
Exposure to sun[edit]
See also: Sun tanning
.... "Melanin in the skin protects the body by absorbing solar radiation. In general, the more melanin there is in the skin the more solar radiation can be absorbed. Excessive solar radiation causes direct and indirect DNA damage to the skin and the body naturally combats and seeks to repair the damage and protect the skin by creating and releasing further melanin into the skin's cells. With the production of the melanin, the skin color darkens, but can also cause sunburn. The tanning process can also be created by artificial UV radiation.
There are two different mechanisms involved. Firstly, the UVA-radiation creates oxidative stress, which in turn oxidizes existing melanin and leads to rapid darkening of the melanin, also known as IPD (immediate pigment darkening). Secondly, there is an increase in production of melanin known as melanogenesis. Melanogenesis leads to delayed tanning and first becomes visible about 72 hours after exposure. The tan that is created by an increased melanogenesis lasts much longer than the one that is caused by oxidation of existing melanin. Tanning involves not just the increased melanin production in response to UV radiation but the thickening of the top layer of the epidermis, the stratum corneum.
A person's natural skin color has an impact on their reaction to exposure to the sun. Generally, those who start out with darker skin colour and more melanin have better abilities to tan. Individuals with very light skin and albinos have no ability to tan. The biggest differences resulting from sun exposure are visible in individuals who start out with moderately pigmented brown skin: the change is dramatically visible as tan lines, where parts of the skin which tanned are delineated from unexposed skin.
Modern lifestyles and mobility have created mismatch between skin colour and environment for many individuals. Vitamin D deficiencies and UVR overexposure are concerns for many. It is important for these people to individually determine their diet and lifestyle according to their skin colour, the environment they live in, and the time of the year. When exposed to UVB, the entire exposed area of body’s skin of a highly dark-skinned person is able to between 3500 - 6500 IU of vitamin D, while a lightly pigmented person is able to make 10000-20000 IU of vitamin D.For practical purposes, such as exposure time for sun tanning, six skin types are distinguished following Fitzpatrick (1975), listed in order of decreasing lightness:
Fitzpatrick scale[edit]
Main article: Fitzpatrick scale
Type
Also called
Sunburning
Tanning behavior
Von Luschan's chromatic scale
I Light, pale white Often Occasionally 1–5
II White, fair Usually Sometimes 6–10
III Medium, white to light brown Rarely Usually 11–15
IV Olive, moderate brown Rarely Often 16–21
V Brown, dark brown Very rarely Sometimes darkens 22–28
VI Very dark brown to black Extremely rarely Naturally black-brown skin 29–36
Dark skin with large concentrations of melanin protects against ultraviolet light and skin cancers; light-skinned people have about a tenfold greater risk of dying from skin cancer, compared with dark-skinned persons, under equal sunlight exposure. Furthermore, UV-A rays from sunlight are believed to interact with folic acid in ways that may damage health. In a number of traditional societies the sun was avoided as much as possible, especially around noon when the ultraviolet radiation in sunlight is at its most intense. Midday was a time when people stayed in the shade and had the main meal followed by a nap,[80] a practice similar to the modern siesta. Modern lifestyles and mobility have created mismatch between skin colour and environment for many individuals. Vitamin D deficiencies and UVR overexposure are concerns for many. It is important for these people to individually determine their diet and lifestyle according to their skin colour, the environment they live in, and the time of the year. When exposed to UVB, the entire exposed area of body’s skin of a highly dark-skinned person is able to between 3500 - 6500 IU of vitamin D, while a lightly pigmented person is able to make 10000-20000 IU of vitamin D."
Exposure to sun[edit]
See also: Sun tanning
.... "Melanin in the skin protects the body by absorbing solar radiation. In general, the more melanin there is in the skin the more solar radiation can be absorbed. Excessive solar radiation causes direct and indirect DNA damage to the skin and the body naturally combats and seeks to repair the damage and protect the skin by creating and releasing further melanin into the skin's cells. With the production of the melanin, the skin color darkens, but can also cause sunburn. The tanning process can also be created by artificial UV radiation.
There are two different mechanisms involved. Firstly, the UVA-radiation creates oxidative stress, which in turn oxidizes existing melanin and leads to rapid darkening of the melanin, also known as IPD (immediate pigment darkening). Secondly, there is an increase in production of melanin known as melanogenesis. Melanogenesis leads to delayed tanning and first becomes visible about 72 hours after exposure. The tan that is created by an increased melanogenesis lasts much longer than the one that is caused by oxidation of existing melanin. Tanning involves not just the increased melanin production in response to UV radiation but the thickening of the top layer of the epidermis, the stratum corneum.
A person's natural skin color has an impact on their reaction to exposure to the sun. Generally, those who start out with darker skin colour and more melanin have better abilities to tan. Individuals with very light skin and albinos have no ability to tan. The biggest differences resulting from sun exposure are visible in individuals who start out with moderately pigmented brown skin: the change is dramatically visible as tan lines, where parts of the skin which tanned are delineated from unexposed skin.
Modern lifestyles and mobility have created mismatch between skin colour and environment for many individuals. Vitamin D deficiencies and UVR overexposure are concerns for many. It is important for these people to individually determine their diet and lifestyle according to their skin colour, the environment they live in, and the time of the year. When exposed to UVB, the entire exposed area of body’s skin of a highly dark-skinned person is able to between 3500 - 6500 IU of vitamin D, while a lightly pigmented person is able to make 10000-20000 IU of vitamin D.For practical purposes, such as exposure time for sun tanning, six skin types are distinguished following Fitzpatrick (1975), listed in order of decreasing lightness:
Fitzpatrick scale[edit]
Main article: Fitzpatrick scale
Type
Also called
Sunburning
Tanning behavior
Von Luschan's chromatic scale
I Light, pale white Often Occasionally 1–5
II White, fair Usually Sometimes 6–10
III Medium, white to light brown Rarely Usually 11–15
IV Olive, moderate brown Rarely Often 16–21
V Brown, dark brown Very rarely Sometimes darkens 22–28
VI Very dark brown to black Extremely rarely Naturally black-brown skin 29–36
Dark skin with large concentrations of melanin protects against ultraviolet light and skin cancers; light-skinned people have about a tenfold greater risk of dying from skin cancer, compared with dark-skinned persons, under equal sunlight exposure. Furthermore, UV-A rays from sunlight are believed to interact with folic acid in ways that may damage health. In a number of traditional societies the sun was avoided as much as possible, especially around noon when the ultraviolet radiation in sunlight is at its most intense. Midday was a time when people stayed in the shade and had the main meal followed by a nap,[80] a practice similar to the modern siesta. Modern lifestyles and mobility have created mismatch between skin colour and environment for many individuals. Vitamin D deficiencies and UVR overexposure are concerns for many. It is important for these people to individually determine their diet and lifestyle according to their skin colour, the environment they live in, and the time of the year. When exposed to UVB, the entire exposed area of body’s skin of a highly dark-skinned person is able to between 3500 - 6500 IU of vitamin D, while a lightly pigmented person is able to make 10000-20000 IU of vitamin D."