Talk:Ultraviolet index

Whose shi*headed idea was it to call 6 'high'? If a dish was given a rating of 6/10, would that be considered a high score? No, it would be considered moderate. Not much over an exact middling score of 5/10. When the purpose of the scale is to inform the general public, why is such a misleading inconsistency with other scales of 1 to 10 used? — Preceding unsigned comment added by 192.252.134.230 (talk) 16:04, 25 June 2014 (UTC)

:Good point. I think 6 really was considered 'high' and 10 was 'maximum' for the Canadians who defined the index in 1992. Now that the ozone layer is thinner and the UV Index is used worldwide, it often reaches 15–20 in tropical territory, and 6 is indeed mild by comparison. If they had to start fresh today, I suspect they'd define the scale differently. I'll try to add something to the article to reflect this. –Patrug (talk) 08:27, 26 June 2014 (UTC)

:I made a few edits to explain index level 10. Hope this helps a bit. –Patrug (talk) 05:14, 29 June 2014 (UTC)

Because this scale is linear, the lower numbers are still a serious health threat. 10 is only twice as dangerous as 5, which means that 5 is still half as dangerous as 10. Get a sunburn at 10 in 15 minutes or at 5 in 30 minutes, not that much difference, you are still sunburnt, just the same. This is not like most scales where there is a much bigger difference between 5 and 10.-71.174.183.90 (talk) 12:57, 13 June 2016 (UTC)

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Please add information about UV on non-horizontal surfaces.-71.174.183.90 (talk) 12:59, 13 June 2016 (UTC)

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As of this writing, the intro to the article states: "The UV index is designed as an open-ended linear scale, directly proportional to the intensity of UV radiation that causes sunburn on human skin. For example, if a light-skinned individual (without sunscreen) begins to sunburn in 30 minutes at UV index 6, then that individual should expect to sunburn in about 15 minutes at UV index 12 – twice the UV, twice as fast."

I would love this article to cover what that function is in more detail, because I've found it very difficult to find a consensus on the function between UV index and how much estimated time it takes varying skin types to burn. The Wikipedia article Sunburn touches on this topic, mainly in terms of its discussion on skin types. But understandably, it doesn't carry the topic further. (I think this ought to be the article to cover the topic in more detail, anyway.) The online sources I've come across give different quantities of minutes, which can vary by over a half hour. And they don't always have the number of minutes decreasing linearly with rising UV index.

As this article mentions in the intro, the UV Index has been adopted by the World Health Organization and World Meteorological Organization. But I haven't been able to find any information through either organization on how UV index corresponds to sunburn time. Perhaps the answer is the organizations want to shy away from the exact number of minutes originally estimated for the UV index intervals. Or, perhaps the exact number of minutes still matters to organizations with authority on UV index, but they don't closely agree on an equation.

Let me try to get the ball slowly rolling on this topic. Here are a couple sources that display a function between UV index and sunburn time based on skin type:

• COST-713 Action UVB Forecasting, Brussels 1999: http://i115srv2.vu-wien.ac.at/uv/booklet/par_4.htm (Website's Index: http://i115srv2.vu-wien.ac.at/uv/booklet/index.htm) – COST stands for European Cooperation in Science and Technology. About halfway down the webpage, there's a graph (labeled Figure 2) that shows the function. Unfortunately, I couldn't identify a formula that the graph is based on, although there is a bit of discussion on the variables used. Note that the graph is not linear.

• OpenUV Knowledge Base Fitzpatrick Skin Types & Safe Exposure Time Calculation: https://www.openuv.io/kb/skin-types-safe-exposure-time-calculation – This at least offers an equation that's dependent on skin type and UV index. The scale is linear. However, the sunburn times are consistently higher than what online calculators have to offer. (For example, the equation still allows someone of skin type 1 to be out for 16.7 minutes at UV index 10.)

This topic doesn't appear simple to answer, so it may require a source associated with the World Health Organization or World Meteorological Organization. Thanks in advance to anyone who has the time and resources to produce some more solid information on this.

--DAK4Blizzard (talk) 05:52, 1 October 2021 (UTC)

:I'm following up on this topic. Although the UV index is a linear scale, what it's actually based on with respect to sunburn time is a rational function. I thought the 2 sources I listed above were showing fundamentally conflicting functions of the UV index. But I realized they're essentially showing the same equation. (I use the word "essentially" because I can't verify whether the sources' y values (sunburn time) are the exact same with respect to UV index, but their y values do decrease at similar rates, which are non-linear.) That equation is the following: Time = (200 x f_skin )/(3 x UVI). f_skin is skin sensitivity factor and UVI is the given UV index. This will be tricky to verify, as it's tough to identify a definitive source for the equation. Plus, the f_skin constant is subject to variation for a particular skin type. For example, Fitzpatrick gave f_skin a range of 3 to 5 for skin type 3. The best I can do for now is cite a document I found, written by an atmospheric research scientist in New Zealand. It does helpfully attempt to apply a specific value to each skin type. That source is: McKenzie, Richard. "[https://www.niwa.co.nz/sites/niwa.co.nz/files/Calculation-of-UVI-for-Smartphone-Apps_V4.pdf Calculation of UVI for Smartphone Apps (PDF)]". The National Institute of Water and Atmospheric Research. The equation can be found on page 25 of that document. DAK4Blizzard (talk) 06:07, 15 November 2021 (UTC)

My main concern is I've been unable to find a source for "The recommendations below are for average adults with lightly tanned skin". So I added a 'citation needed' tag.

More generally, but of less concern (as I don't suppose it was made up), I've been unable to identify the source(s) for the contents of the table as a whole. Maybe it was collated from multiple sources. Two references are cited

{{cite web |url=https://www.epa.gov/sunsafety/uv-index-scale-0 |title=UV Index Scale |publisher=U.S. Environmental Protection Agency |series=Sun Safety |access-date=June 28, 2019|date=2013-02-04 }}

{{cite web |url=https://www.epa.gov/sites/default/files/documents/uviguide.pdf |title=A Guide to the UV Index |publisher=U.S. Environmental Protection Agency |date=2022}}.

Although they're similar to the information given in the table, the table has extra information.

Maybe the sources have been updated and pruned since this section was written.

{{cite web |url=https://www.epa.gov/enviro/uv-index-description |title=UV Index Overview |publisher=U.S. Environmental Protection Agency |date=2022}}

is also cited earlier in an earlier section. It too has similar information, but not all the information in the table.

Housecarl (talk) 06:03, 31 July 2022 (UTC)

{{reflist-talk}}

Does the UV index numbers altar how bright the sunlight is on the ground? Meaning would the sunlight on the ground if the UV Index is 8 be just as bright if the sun was at any angle in the horizon? Florida in February commonly goes up to 8 but the Suns angle is only 48°. In the north, 48° is usually around 5 or 6. So would Floridas sunlight in February be just as bright as the north’s during July which is 8 as well? RedProofHill123 (talk) 17:25, 12 October 2022 (UTC)

Would be really helpful for Wikipedia to have a table of country rankings of average UV index. From highest to lowest. 49.180.158.253 (talk) 00:56, 5 February 2023 (UTC)

:Also here's a source that provides all that info, that can be used. [https://apps.who.int/gho/data/view.main.35300]49.180.158.253 (talk) 01:01, 5 February 2023 (UTC)

The second paragraph of the introduction says “The UV index is designed as an open-ended linear scale…” The article, then refers to the (American) Fitzpatrick scale devised in 1975. Only in the third paragraph, the reader learns that the UV index was developed by Canadian scientists in 1992.

The juxtaposition of these references is confusing. Therefore, I have removed the mention of the Fitzpatrick scale from the introduction. It remains in the body of the article where I have added a few words of clarification. Humphrey Tribble (talk) 09:31, 5 February 2023 (UTC)