Ultraviolet index

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Average UV at noon 1996-2002 (European Space Agency) GOME.uviecclimyear lr.gif
Average UV at noon 1996-2002 (European Space Agency)

The ultraviolet index, or UV index, is an international standard measurement of the strength of the sunburn-producing ultraviolet (UV) radiation at a particular place and time. It is primarily used in daily and hourly forecasts aimed at the general public. The UV index is designed as an open-ended linear scale, directly proportional to the intensity of UV radiation, and adjusting for wavelength based on what causes human skin to sunburn. [1] The purpose of the UV index is to help people effectively protect themselves from UV radiation, which has health benefits in moderation but in excess causes sunburn, skin aging, DNA damage, skin cancer, immunosuppression, [2] and eye damage, such as cataracts.

Contents

The scale was developed by Canadian scientists in 1992, and then adopted and standardized by the UN's World Health Organization and World Meteorological Organization in 1994. [3] Public health organizations recommend that people protect themselves (for example, by applying sunscreen to the skin and wearing a hat and sunglasses) if they spend substantial time outdoors when the UV index is 3 or higher; see the table below for more detailed recommendations.

Description

Typical variation of UV index by time of day and time of year, around 40.71 -74.01, based on FastRT UV Calculator UV Index NYC.png
Typical variation of UV index by time of day and time of year, around 40.71 -74.01, based on FastRT UV Calculator

The UV index is a linear scale that measures the intensity of UV radiation with respect to sunburn. For example, assuming similar spectral power distributions, radiation with a UV index of 12 is twice as intense as radiation at a UV index of 6. For a wide range of timescales, sunburn in response to controlled UV radiation occurs in proportion to the total number of photons delivered, not varying with the intensity or duration of exposure. [5] Therefore, under similar conditions, a person who develops a sunburn after 30 minutes of exposure to UV index 6 radiation would most likely develop a sunburn after 15 minutes of exposure to UV index 12 radiation, since it is twice the intensity but half the duration. [6] This linear scale is unlike other common environmental scales such as decibels or the Richter scale, which are logarithmic (the severity multiplies for each step on the scale, growing exponentially).

An index of 0 corresponds to zero UV radiation, as is essentially the case at night. An index of 10 corresponds roughly to midday summer sunlight in the tropics with a clear sky when the UV index was originally designed; now summertime index values in the tens are common for tropical latitudes, mountainous altitudes, areas with ice/water reflectivity and areas with above-average ozone layer depletion. [7]

While the UV index can be calculated from a direct measurement of the UV spectral power at a given location, as some inexpensive portable devices are able to approximate, the value given in weather reports is usually a prediction based on a computer model. Although this may be in error (especially when cloud conditions are unexpectedly heavy or light), it is usually within ±1 UV index unit as that which would be measured. [8]

When the UV index is presented on a daily basis, it represents UV intensity around the sun's highest point in the day, called solar noon, halfway between sunrise and sunset. This typically occurs between 11:30 and 12:30, or between 12:30 and 13:30 in areas where daylight saving time is being observed. Predictions are made by a computer model that accounts for the effects of sun-earth distance, solar zenith angle, total ozone amount, tropospheric aerosol optical depth, elevation, snow/ice reflectivity and cloud transmission, all of which influence the amount of UV radiation at the surface. [7]

Technical definition

Sunburn effect (as measured by the UV index) is the product of the sunlight power spectrum (radiation intensity) and the erythemal action spectrum (skin sensitivity) across the range of UV wavelengths. Erythemal action spectrum.svg
Sunburn effect (as measured by the UV index) is the product of the sunlight power spectrum (radiation intensity) and the erythemal action spectrum (skin sensitivity) across the range of UV wavelengths.

The UV index is a number linearly related to the intensity of sunburn-producing UV radiation at a given point on the Earth's surface. It cannot be simply related to the irradiance (measured in W/m2) because the UV of greatest concern occupies a spectrum of wavelengths from 295 to 325 nm, and shorter wavelengths have already been absorbed a great deal when they arrive at the earth's surface. However, skin damage from sunburn is related to wavelength, the shorter wavelengths being much more damaging. The UV power spectrum (expressed as watts per square meter per nanometer of wavelength) is therefore multiplied by a weighting curve known as the CIE-standard McKinlay–Diffey erythemal action spectrum. [9] [10] There are some older formulas for the spectrum, resulting in differences of up to 2%. [11] The result is integrated over the whole spectrum. This gives a weighted figure called the Diffey-weighted UV irradiance (DUV) or the erythemal dose rate. Since the normalization weight is 1 for wavelengths between 250nm and 298nm, a source of a given DUV irradiance causes roughly as much sunburn as a radiation source emitting those wavelengths at the same intensity, although inaccuracies in the spectrum definition and varying reactions by skin type may mean this relationship does not actually hold. [12] When the index was designed, the typical midday summer sunlight was around 250 mW/m2. Thus, for convenience, the DUV is divided by 25 mW/m2 to produce an index [13] [14] nominally from 0 to 11+, though ozone depletion is now resulting in higher values.

To illustrate the spectrum weighting principle, the incident power density in midday summer sunlight is typically 0.6 mW/(nm m2) at 295 nm, 74 mW/(nm m2) at 305 nm, and 478 mW/(nm m2) at 325 nm. (Note the huge absorption that has already taken place in the atmosphere at short wavelengths.) The erythemal weighting factors applied to these figures are 1.0, 0.22, and 0.003 respectively. (Also note the huge increase in sunburn damage caused by the shorter wavelengths; e.g., for the same irradiance, 305 nm is 22% as damaging as 295 nm, and 325 nm is 0.3% as damaging as 295 nm.) Integration of these values using all the intermediate weightings over the full spectral range of 290 nm to 400 nm [13] produces a figure of 264 mW/m2 (the DUV), which is then divided by 25 mW/m2 to give a UV index of 10.6. [14]

History

After sporadic attempts by various meteorologists to define a "sunburn index" and growing concern about ozone depletion, Environment Canada scientists James B. Kerr, C. Thomas McElroy, and David I. Wardle invented the modern UV index in Toronto, Ontario. Environment Canada launched it as part of the weather forecast on May 27, 1992, making Canada the first country in the world to issue official predictions of UV levels for the next day. [15] [16] Many other countries followed suit with their own UV indices. Initially, the methods of calculating and reporting a UV index varied significantly from country to country. A global UV index, first standardized by the World Health Organization and World Meteorological Organization in 1994, [17] gradually replaced the inconsistent regional versions, specifying not only a uniform calculation method (the Canadian definition) but also standard colors and graphics for visual media. [18]

On December 29, 2003, a world-record ground-level UV index of 43.3 was detected at Bolivia's Licancabur volcano, [19] [20] though other scientists dispute readings higher than 26. [21]

In 2005, Australia [22] and the United States [23] launched the UV Alert. While the two countries have different baseline UV intensity requirements before issuing an alert, their common goal is to raise awareness of the dangers of over-exposure to the Sun on days with intense UV radiation.

In 2007, the United Nations honored UV index inventors Kerr, McElroy, and Wardle with the Innovators Award for their far-reaching work on reducing public health risks from UV radiation. [24] In the same year, a survey among meteorologists ranked the development of the UV index as #11 on The Weather Channel's 100 Biggest Weather Moments .

In 2022, a new mobile phone application that provides localized information on ultraviolet (UV) radiation levels has been launched by the World Health Organization (WHO), the World Meteorological Organization (WMO), the United Nations Environment Programme (UNEP) and the International Labour Organization (ILO). [25]

Index usage

The recommendations below are for average adults with lightly tanned skin [ citation needed ] (Fitzpatrick scale of skin colour: Type II). Those with darker skin (Type IV+) are more likely to withstand greater sun exposure, while extra precautions are needed for children, seniors, particularly fair-skinned adults, and those who have greater sun sensitivity for medical reasons [26] or from UV exposure in previous days.

When the day's predicted UV index is within various numerical ranges, the recommendations for protection are as follows: [18] [27]

UV indexMedia graphic colorRisk of harm from unprotected sun exposure, for the average adultRecommended protection
0 - 2Green"Low"A UV index reading of 0 to 2 means low danger from the Sun's UV rays for the average person.

Wear sunglasses on bright days. If you burn easily, cover up and use broad spectrum SPF 15+ sunscreen. Bright surfaces, [26] sand, water, and snow, [18] will increase UV exposure.

3 - 5Yellow"Moderate"A UV index reading of 3 to 5 means moderate risk of harm from unprotected sun exposure.

Stay in shade near midday when the sun is strongest. If outdoors, wear sun-protective clothing, a wide-brimmed hat, and UV-blocking sunglasses. Generously apply broad spectrum SPF 50+ sunscreen every 1.5 hours, even on cloudy days, and after swimming or sweating. Bright surfaces, such as sand, water, and snow, will increase UV exposure.

6 - 7Orange"High"A UV index reading of 6 to 7 means high risk of harm from unprotected sun exposure. Protection against skin and eye damage is needed.

Reduce time in the sun between 10 a.m. and 4 p.m. If outdoors, seek shade and wear sun-protective clothing, a wide-brimmed hat, and UV-blocking sunglasses. Generously apply broad spectrum SPF 50+ sunscreen every 1.5 hours, even on cloudy days, and after swimming or sweating. Bright surfaces, such as sand, water, and snow, will increase UV exposure.

8 - 10Red"Very high"A UV index reading of 8 to 10 means very high risk of harm from unprotected sun exposure. Take extra precautions because unprotected skin and eyes will be damaged and can burn quickly.

Minimize sun exposure between 10 a.m. and 4 p.m. If outdoors, seek shade and wear sun-protective clothing, a wide-brimmed hat, and UV-blocking sunglasses. Generously apply broad spectrum SPF 50+ sunscreen every 1.5 hours, even on cloudy days, and after swimming or sweating. Bright surfaces, such as sand, water, and snow, will increase UV exposure.

11+Violet"Extreme"A UV index reading of 11 or more means extreme risk of harm from unprotected sun exposure. Take all precautions because unprotected skin and eyes can burn in minutes.

Try to avoid sun exposure between 10 a.m. and 4 p.m. If outdoors, seek shade and wear sun-protective clothing, a wide-brimmed hat, and UV-blocking sunglasses. Generously apply broad spectrum SPF 50+ sunscreen every 1.5 hours, even on cloudy days, and after swimming or sweating. Bright surfaces, such as sand, water, and snow, will increase UV exposure.

Some sunshine prediction and advice apps have been released. These use the UV index and Fitzpatrick scale skin type to calculate the maximum exposure time before receiving a sunburn. [28] The Fitzpatrick scale is not sufficient to precisely estimate the minimum radiation dose needed for sunburn - it varies in populations. Research has found a 4x increase in minimum dose to sunburn from subjects in the US compared to subjects in Taiwan. [29] Neglecting weighting, 9 mJ/cm2 is 1 UV index hour.

See also

Related Research Articles

<span class="mw-page-title-main">Electromagnetic spectrum</span> Range of frequencies or wavelengths of electromagnetic radiation

The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength. The spectrum is divided into separate bands, with different names for the electromagnetic waves within each band. From low to high frequency these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. The electromagnetic waves in each of these bands have different characteristics, such as how they are produced, how they interact with matter, and their practical applications.

<span class="mw-page-title-main">Ozone layer</span> Region of the stratosphere

The ozone layer or ozone shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet radiation. It contains a high concentration of ozone (O3) in relation to other parts of the atmosphere, although still small in relation to other gases in the stratosphere. The ozone layer contains less than 10 parts per million of ozone, while the average ozone concentration in Earth's atmosphere as a whole is about 0.3 parts per million. The ozone layer is mainly found in the lower portion of the stratosphere, from approximately 15 to 35 kilometers (9 to 22 mi) above Earth, although its thickness varies seasonally and geographically.

<span class="mw-page-title-main">Radiation</span> Waves or particles moving through space

In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or a material medium. This includes:

<span class="mw-page-title-main">Sunlight</span> Light emitted by the Sun

Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when the Sun is above the horizon. When direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and radiant heat (Atmospheric). When blocked by clouds or reflected off other objects, sunlight is diffused. Sources estimate a global average of between 164 watts to 340 watts per square meter over a 24-hour day; this figure is estimated by NASA to be about a quarter of Earth's average total solar irradiance.

<span class="mw-page-title-main">Ultraviolet</span> Energetic, invisible light energy range

Ultraviolet (UV) light is electromagnetic radiation of wavelength shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight, and constitutes about 10% of the total electromagnetic radiation output from the Sun. It is also produced by electric arcs; Cherenkov radiation; and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights.

<span class="mw-page-title-main">Electromagnetic radiation and health</span> Aspect of public health

Electromagnetic radiation can be classified into two types: ionizing radiation and non-ionizing radiation, based on the capability of a single photon with more than 10 eV energy to ionize atoms or break chemical bonds. Extreme ultraviolet and higher frequencies, such as X-rays or gamma rays are ionizing, and these pose their own special hazards: see radiation poisoning.

<span class="mw-page-title-main">Sunscreen</span> Topical skin product that helps protect against sunburn

Sunscreen, also known as sunblock or sun cream, is a photoprotective topical product for the skin that helps protect against sunburn and most importantly prevent skin cancer. Sunscreens come as lotions, sprays, gels, foams, sticks, powders and other topical products. Sunscreens are common supplements to clothing, particularly sunglasses, sunhats and special sun protective clothing, and other forms of photoprotection.

<span class="mw-page-title-main">Blacklight</span> Light fixture that emits long-wave ultraviolet light and very little visible light

A blacklight, also called a UV-A light, Wood's lamp, or ultraviolet light, is a lamp that emits long-wave (UV-A) ultraviolet light and very little visible light. One type of lamp has a violet filter material, either on the bulb or in a separate glass filter in the lamp housing, which blocks most visible light and allows through UV, so the lamp has a dim violet glow when operating. Blacklight lamps which have this filter have a lighting industry designation that includes the letters "BLB". This stands for "blacklight blue". A second type of lamp produces ultraviolet but does not have the filter material, so it produces more visible light and has a blue color when operating. These tubes are made for use in "bug zapper" insect traps, and are identified by the industry designation "BL". This stands for "blacklight".

<span class="mw-page-title-main">Sun tanning</span> Darkening of skin in response to ultraviolet light

Sun tanning or tanning is the process whereby skin color is darkened or tanned. It is most often a result of exposure to ultraviolet (UV) radiation from sunlight or from artificial sources, such as a tanning lamp found in indoor tanning beds. People who deliberately tan their skin by exposure to the sun engage in a passive recreational activity of sun bathing. Some people use chemical products which can produce a tanning effect without exposure to ultraviolet radiation, known as sunless tanning.

<span class="mw-page-title-main">Germicidal lamp</span> Ultraviolet C light-emitting device

A germicidal lamp is an electric light that produces ultraviolet C (UVC) light. This short-wave ultraviolet light disrupts DNA base pairing, causing formation of pyrimidine dimers, and leads to the inactivation of bacteria, viruses, and protozoans. It can also be used to produce ozone for water disinfection. They are used in ultraviolet germicidal irradiation (UVGI).

<span class="mw-page-title-main">Action spectrum</span> Graph of the rate of biological effectiveness plotted against wavelength of light

An action spectrum is a graph of the rate of biological effectiveness plotted against wavelength of light. It is related to absorption spectrum in many systems. Mathematically, it describes the inverse quantity of light required to evoke a constant response. It is very rare for an action spectrum to describe the level of biological activity, since biological responses are often nonlinear with intensity.

<span class="mw-page-title-main">UV filter</span> Camera parts, features and technologies

UV filters are compounds, mixtures, or materials that block or absorb ultraviolet (UV) light. One of the major applications of UV filters is their use as sunscreens to protect skin from sunburn and other sun/UV related damage. After the invention of digital cameras changed the field of photography, UV filters have been used to coat glass discs fitted to camera lenses to protect hardware that is sensitive to UV light.

<span class="mw-page-title-main">Ultraviolet germicidal irradiation</span> Disinfection method using ultraviolet light

Ultraviolet germicidal irradiation (UVGI) is a disinfection technique employing ultraviolet (UV) light, particularly UV-C (180-280 nm), to kill or inactivate microorganisms. UVGI primarily inactivates microbes by damaging their genetic material, thereby inhibiting their capacity to carry out vital functions.

<span class="mw-page-title-main">Dobson ozone spectrophotometer</span>

The Dobson spectrophotometer, also known as Dobsonmeter, Dobson spectrometer, or just Dobson is one of the earliest instruments used to measure atmospheric ozone.

UV-B lamps are lamps that emit a spectrum of ultraviolet light with wavelengths ranging from 290–320 nanometers. This spectrum is also commonly called the biological spectrum due to the human body's sensitivity to light of such a wavelength. UV-B light does not tan the skin very much, compared to the UV-A lamps that are used in tanning beds.

<span class="mw-page-title-main">Sunburn</span> Burning of the skin by the suns radiation

Sunburn is a form of radiation burn that affects living tissue, such as skin, that results from an overexposure to ultraviolet (UV) radiation, usually from the Sun. Common symptoms in humans and other animals include red or reddish skin that is hot to the touch or painful, general fatigue, and mild dizziness. Other symptoms include blistering, peeling skin, swelling, itching, and nausea. Excessive UV radiation is the leading cause of (primarily) non-malignant skin tumors, which in extreme cases can be life-threatening. Sunburn is an inflammatory response in the tissue triggered by direct DNA damage by UV radiation. When the cells' DNA is overly damaged by UV radiation, type I cell-death is triggered and the tissue is replaced.

<span class="mw-page-title-main">Health effects of sunlight exposure</span>

Exposing skin to the ultraviolet radiation in sunlight has both positive and negative health effects. On the positive side, exposure allows for the synthesis of vitamin D3. Vitamin D has been suggested as having a wide range of positive health effects, which include strengthening bones and possibly inhibiting the growth of some cancers. A dietary supplement can also supply vitamin D, but there are also benefits to exposure not obtainable through Vitamin D supplementation. Long-term sun exposure is associated with reduced all-cause mortality and reduced mortality risk from cardiovascular disease (CVD), some forms of cancer, and non-CVD/noncancer related disease, with indications in these studies that Vitamin D is not the mediator. Supplementation offers limited bioavailability and no synthesis of subdermal nitric oxide. UV exposure also has positive effects for endorphin levels, and possibly for protection against multiple sclerosis. Abundant visible light to the eyes gives health benefits through its association with the timing of melatonin synthesis, maintenance of normal and robust circadian rhythms, and reduced risk of seasonal affective disorder.

<span class="mw-page-title-main">Non-ionizing radiation</span> Harmless low-frequency radiation

Non-ionizingradiation refers to any type of electromagnetic radiation that does not carry enough energy per quantum to ionize atoms or molecules—that is, to completely remove an electron from an atom or molecule. Instead of producing charged ions when passing through matter, non-ionizing electromagnetic radiation has sufficient energy only for excitation. Non-ionizing radiation is not a significant health risk. In contrast, ionizing radiation has a higher frequency and shorter wavelength than non-ionizing radiation, and can be a serious health hazard: exposure to it can cause burns, radiation sickness, many kinds of cancer, and genetic damage. Using ionizing radiation requires elaborate radiological protection measures, which in general are not required with non-ionizing radiation.

A dose rate is quantity of radiation absorbed or delivered per unit time. It is often indicated in micrograys per hour (µGy/h) or as an equivalent dose rate ḢT in rems per hour (rem/hr) or sieverts per hour (Sv/h).

Optical radiation is part of the electromagnetic spectrum. It is a type of non-ionising radiation (NIR), with electromagnetic fields (EMFs).

References

  1. ↑ "UV Index Overview". U.S. Environmental Protection Agency. 2022.
  2. ↑ Hanneman, K. K.; et al. (January 2006). "Ultraviolet immunosuppression: Mechanisms and consequences". Dermatologic Clinics. 24 (1): 19–25. doi:10.1016/j.det.2005.08.003. PMID   16311164.
  3. ↑ Heckman, C. J.; Liang, K.; Riley, M. (2022). "Awareness, Understanding, Use, and Impact of the UV Index: A Systematic Review of Over Two Decades of International Research". Preventive Medicine. 123: 71–83. doi:10.1016/j.ypmed.2019.03.004. PMC   6534479 . PMID   30844501.
  4. ↑ Engelsen, Ola & Kylling, Arve (April 2005). "Fast simulation tool for ultraviolet radiation at the earth's surface". Optical Engineering. 44 (4). 041012. Bibcode:2005OptEn..44d1012E. doi:10.1117/1.1885472.
  5. ↑ Gange, R. William; Parrish, John A. (1983). "Acute Effects of Ultraviolet Radiation upon the Skin". Photoimmunology. pp. 77–94. doi:10.1007/978-1-4613-3670-9_5. ISBN   978-1-4613-3672-3.
  6. ↑ Craft, Chita (July 26, 2021). "What do UV Index numbers mean?". khou.com.
  7. 1 2 Fioletov, V.; et al. (July–August 2010). "The UV index: Definition, distribution and factors affecting it". Canadian Journal of Public Health. 101 (4): I5–I9. doi:10.1007/BF03405303. PMC   6974160 . PMID   21033538.
  8. ↑ "UV Index: Is it Validated?". NOAA/National Weather Service. 2006.
  9. 1 2 McKinlay, A. F. & Diffey, B. L. (1987). "A reference action spectrum for ultraviolet induced erythema in human skin". CIE Journal. 6 (1): 17–22.
  10. 1 2 "UV Spectral Irradiances & Erythemal Action Spectrum". NOAA. 2006.
  11. ↑ Webb, Ann R.; Slaper, Harry; Koepke, Peter; Schmalwieser, Alois W. (March 2011). "Know Your Standard: Clarifying the CIE Erythema Action Spectrum". Photochemistry and Photobiology. 87 (2): 483–486. doi: 10.1111/j.1751-1097.2010.00871.x . PMID   21366601. S2CID   27978649.
  12. ↑ Moshammer, H; Simic, S; Haluza, D (24 October 2016). "UV "Indices"-What Do They Indicate?". International Journal of Environmental Research and Public Health. 13 (10): 1041. doi: 10.3390/ijerph13101041 . PMC   5086780 . PMID   27783061.
  13. 1 2 "How UV Index is Calculated". SunWise. U.S. Environmental Protection Agency. 2015-08-21. Archived from the original on November 29, 2012.
  14. 1 2 "How Is the UV Index Calculated?". Smithsonian Institution. Archived from the original on June 13, 2010. (This source contains some numerical errors.)
  15. ↑ Kerr, J. B.; et al. (1994). "The Canadian Ozone Watch and UV-B advisory programs". Ozone in the Troposphere and Stratosphere, Part 2: Proceedings of the Quadrennial Ozone Symposium 1992. NASA/Goddard Space Flight Center: 794–797. N95-11093.
  16. ↑ "Environment Canada's UV Index Celebrates Ten Years: Now Bringing Sun Safety Messages to 26 Countries" (Press release). Environment Canada. May 27, 2002. Archived from the original on July 14, 2014.
  17. ↑ Report of the WMO Meeting of Experts on UV-B Measurements, Data Quality and Standardization of UV Indices, 1994. Global Atmosphere Watch (Report). World Meteorological Organization. 1995. WMO/TD-No. 625.
  18. 1 2 3 Organization, World Meteorological (2002). Global Solar UV Index: A Practical Guide. World Health Organization. hdl:10665/42459. ISBN   978-92-4-159007-5.
  19. ↑ Oskin, Becky (July 8, 2014). "Blazing World Record: Strongest UV Rays Measured in South America". LiveScience.com.
  20. ↑ Cabrol, Nathalie A.; et al. (July 8, 2014). "Record solar UV irradiance in the tropical Andes". Frontiers in Environmental Science. 2 (19). 19. Bibcode:2014FrES....2...19C. doi: 10.3389/fenvs.2014.00019 .
  21. ↑ McKenzie, Richard L.; et al. (April 8, 2015). "Comment on "Record solar UV irradiance in the tropical Andes, by Cabrol et al."". Frontiers in Environmental Science. 3. 26. doi: 10.3389/fenvs.2015.00026 .
  22. ↑ "What is UV?". SunSmart. Cancer Council Victoria. Archived from the original on January 26, 2016.
  23. ↑ "UV Alert". SunWise. U.S. Environmental Protection Agency. 2015-08-21. Archived from the original on October 14, 2011.
  24. ↑ "Ozone awards". World Meteorological Organization. October 2007. Archived from the original on July 14, 2014.
  25. ↑ "SunSmart Global UV App helps protect you from the dangers of the sun and promotes public health". World Health Organization. 2022.
  26. 1 2 Dresbach, Sereana Howard & Brown, Wanda (2008). "Ultraviolet Radiation" (PDF). The Invisible Environment Fact Sheet Series. The Ohio State University. CDFS-199-08. Archived from the original (PDF) on January 17, 2009.
  27. ↑ "UV Index Scale". Sun Safety. U.S. Environmental Protection Agency. 2013-02-04. Retrieved June 28, 2019.
  28. ↑ Eaton, Kit (16 July 2014). "Your Time in the Sun, Measured to the Minute". The New York Times.
  29. ↑ Li, Yu-Wen; Chu, Chia-Yu (November 2007). "The Minimal Erythema Dose of Broadband Ultraviolet B in Taiwanese". Journal of the Formosan Medical Association. 106 (11): 975–978. doi:10.1016/S0929-6646(08)60071-6. PMID   18063522.
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