UV index

The UV index ( UVI ) is an internationally standardized measure of the solar irradiance ( ultraviolet radiation ) effective for sunburn . In general, the UV index is a measure of the strongest solar radiation around noon (daily maximum). The higher the UVI, the faster health damage caused by UV radiation such as sunburns can occur on unprotected skin. It varies with the cloud cover , the position of the sun (i.e. with geographical latitude , time of day and season), the thickness of the ozone layer and the altitude of the location. A UVI value greater than five indicates a high level of exposure to UV radiation; from UVI 3, sun protection measures ( sun cream etc.) are recommended.

The UV index, which is uniformly understood worldwide, was introduced by the World Health Organization (WHO), the World Meteorological Organization , the United Nations Environment Program and the International Commission for Protection against Non-Ionizing Radiation .

Grading and protection

The UV index is an integer, open-ended quantity of the dimension number ; it is often given in weather forecasts . The information always refers to the expected maximum daily value of sunburn effective UV radiation at the time when the UV rays are strongest and therefore most dangerous; this is usually the case at the highest point of the sun. Recommendations for protection against UV radiation are assigned to the various UVI values ​​(behavioral measures, sunscreens). Taking into account UVI and individual light sensitivity ( skin type , acquired self-protection), appropriate protective measures are recommended for being outdoors:

UV index	rating	protection
0-2	low	No protection required.
3-5	moderate	Protection required: hat, t-shirt, sunglasses , sunscreen
6-7	high	Protection required: hat, t-shirt, sunglasses, sunscreen. The WHO recommends looking for the shade at noon .
8-10	very high	Additional protection required: Avoid staying outdoors if possible The WHO recommends avoiding being outdoors between 11 a.m. and 3 p.m. Even in the shade, a sun-proof top, long trousers, sunscreen, sunglasses and a wide-brimmed hat are part of sun-friendly behavior.
≥ 11	extreme	Additional protection required: Avoid staying outdoors if possible The WHO advises staying in the shelter of a house between 11 a.m. and 3 p.m. and looking for shade outside of this time. Even in the shade, a sun-proof top, long pants, sunscreen, sunglasses and a wide-brimmed hat are essential.

According to the German Radiation Protection Commission, the best sun protection is achieved through appropriate clothing and good sunglasses. At least twice the UV index is recommended as a sufficient sun protection factor for sunscreens; they should be effective in the UV-B and UV-A range. Children and particularly sensitive people are particularly in need of protection.

However, since it is not specified,

• whether a permanent life outdoors without skin damage is possible with consistent application of the recommended protective measures or
• whether additional time spent in the sun must be limited,
• whether the same measures are required for very short periods of time outdoors
• and because the skin type is excluded,

The UV index can only be used as a comparative point of reference, similar to how in cold weather it is estimated which clothing prevents frostbite during a certain length of stay and activity outdoors.

If the individual minimum erythema dose (MED, specified in Jm ⁻² ) of a person is known, the time (in minutes) to achieve the first visible reddening of the skin, the sunburn time, can be calculated as follows with the UV index (UVI): Amount the MED divided by one and a half times the UV index. For example, a MED of 240 Jm ⁻² and a UV index of 8 (maximum 0.2 Wm ⁻² ) results in a sunburn time of 20 minutes. As skin damage occurs even at a dose that does not yet cause sunburn, unprotected exposure to the open air should be significantly shorter than the sunburn time.

UVI values ​​over the course of the year

Typical UVI values ​​of selected locations over the course of a year ( maximum values , i.e. around noon, on the 21st of each month):

place	Latitude	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Petersburg	60 ° N	0	0	1	3	4th	5	5	4th	2	1	0	0
Berlin	52 ° N	1	1	2	4th	5	7th	7th	5	3	1	1	0
Mallorca	39 ° N	2	3	4th	6th	8th	9	9	8th	6th	4th	2	1
Singapore	1 ° N	11	12	13	13	11	11	11	11	12	12	11	10
Sydney	34 ° S	11	10	8th	5	3	2	3	4th	6th	7th	9	10

Typical daily courses of the UV index using New York City as an example

• The intensity of the UV radiation depends primarily on the sun's zenith angle and thus strongly on latitude , the time of year and the time of day.
• Extreme UVI values ​​above 10 can only be found near the equator, in areas with a reduced ozone layer and in high mountains (e.g. Switzerland).
• Depending on the cloud cover , significantly lower values ​​can result.

The highest ever recorded UV radiation intensity was measured in 2003 in the Bolivian Andes with a value of 43.3.

Germany

In Germany, a UV index between 5 and 8 is common between May and August. The index can reach 3 to 5 from March to the end of October. In winter, however, only values ​​up to a maximum of 3 are achieved, with the exception of the mountain regions. Values ​​of 9 and 10 can also be achieved in the higher altitudes of the Alps, especially in summer.

definition

The UV index is an internationally established measure . The spectral irradiance of a horizontal surface is weighted and integrated with the spectrum of activity defined by the CIE : ${\displaystyle E(\lambda )}$ ${\displaystyle s_{\text{er}}(\lambda )}$

${\displaystyle E_{\text{CIE}}=\int s_{\text{er}}(\lambda )\,E(\lambda )\,\mathrm {d} \lambda }$

The spectrum of activity evaluates radiation of 298  nm and short-wave radiation with a factor of 1, longer-wave radiation increasingly lower, radiation of 328 nm with a factor of about 0.0015 and radiation of 400 nm with a factor of 0.00012. This usually results in values ​​of up to around 300  mW / m² . In order to obtain the UV index as a handy dimensionless quantity, it is divided by 25 mW / m².

After all, the maximum UV index of a day suitable for warnings is defined as the highest 30-minute mean value.

The weight function takes into account the damaging effect of the radiation, which is strongly dependent on the wavelength . It is defined in the range from 250 to 400 nm (CIE document S007 / G-1998), but since the UV intensity on the ground drops steeply beyond 300 nm, it is sufficient for the application of the UV index to measure the irradiance in Measure range from 290 to 400 nm. ${\displaystyle s_{\text{er}}(\lambda )}$

history

The UV index was introduced in Canada in 1992 in response to growing concerns about the potential increase in UV radiation from the thinning of the ozone layer ( ozone hole ). In 1994 the index was adopted as the standard indicator of UV values ​​by the World Meteorological Organization (WMO) and the World Health Organization (WHO). The original index ranged from zero to ten, based on North American radiation levels. In 2002 the WHO adopted a guideline (Global Solar UV Index - A Practical Guide) , which took into account the higher radiation values ​​in tropical regions and led to the further development of the index based on the Canadian index. In February 2004, the UV index, which is still used internationally today, was finally introduced by the WHO, WMO, the United Nations Environment Program (UNEP) and the International Commission for Protection against Non-Ionizing Radiation (ICNIRP).

See also

• UV radiation protection

Web links

• Definition of the UV index - standardized by WMO, WHO, UNEP, ICNIRP . German Weather Service (PDF; 86 kB; with spectrum of reference effects for erythema)
• Current Values:
  • Germany ( Federal Office for Radiation Protection )
  • Austria (Section for Biomedical Physics, Medical University Innsbruck )
  • Switzerland ( Federal Office of Public Health )
• 27 different places on earth and their typical monthly UVI values on the website of the Federal Office for Radiation Protection

Individual evidence

1. ↑ Information - What is the UV index . German Weather Service , accessed on July 8, 2017.
2. ↑ ^{a b} What is the UV index? Federal Office for Radiation Protection.
3. ↑ Swiss Federal Office of Public Health .
4. ↑ UV exposure and protection recommendations according to WHO . German Weather Service, accessed on August 4, 2017.
5. ^ The new classification of the solar UV index (UVI) - adaptation to the international recommendation of the WHO - recommendation of the radiation protection commission . Radiation Protection Commission , 192nd meeting, 24./25. June 2004, accessed on August 4, 2017 (PDF).
6. ↑ Frequently asked questions about the "UV index". What does the UV index (UVI) mean? ( Memento from March 2, 2014 in the Internet Archive ) Federal Office for Radiation Protection
7. ↑ Definition of the UV index (with reference spectrum of activity for erythema) (PDF; 86 kB) German Weather Service.
8. ↑ UV index worldwide. Federal Office for Radiation Protection, December 18, 2012; Retrieved July 21, 2013.
9. ^ Gies P. Capital city maximum UV levels by month. Melbourne, Australia: Australian Radiation Protection and Nuclear Safety Agency; 2013.
10. ↑ solar zenith angle
11. ↑ n-tv.de
12. ↑ T-Online: Sun protection - What the UV index says
13. ↑ Information on solar UV radiation from the Federal Environment Agency
14. ↑ Information on the UV index of the German Weather Service
15. ↑ Vitali Fioletov, James B. Kerr, Angus Fergusson: The UV Index: Definition, Distribution and Factors Affecting It . In: Canadian Public Health Association (Ed.): Canadian Journal of Public Health , Vol. 101, No. 4, July / August 2010, pp. I5 – I9 ( PDF ; English).

This article is about a health issue. It is not used for self-diagnosis and does not replace a diagnosis by a doctor. Please note the information on health issues !