UV levels

[Wowbagger]

I have just had a long conversation with my daughter, whose work is in the "Sunsmart" (skin cancer prevention) scheme for Victoria state. She lives in Melbourne. It seems that she is in the process of trying to change the emphasis in her organisation. Hitherto, they have advised people that once the UV level exceeds 3, that's the time to cover up, and their publicity has been based upon the fact that the dangerous months are September to April. However, it appears that UV level 3 is reached on average 10 times every August and slightly fewer in May, so her plan is that they extend the "danger season" by one month - mid-August to mid-May. The records she has been examining go back 13 years, and the earliest level 3 she has found was 7th August.

One of the problems they face is that your body can't detect UV rays and can't feel the damage they are doing. Apparently it's the infra-red rays that make you feel hot, but the UV rays that do the damage, and it seems that there's not necessarily a direct correlation between high IR and high UV. I couldn't get my head round why, but I think it's something to do with the angle at which the sun's rays hit the upper atmosphere. People tend to think that just because it isn't hot they aren't getting burned, but that isn't so. Also, sitting in the shade isn't necessarily going to protect you 100% because UV rays can be reflected off other objects and you aren't going to be aware that you are being damaged. When I was talking to her it was a cloudy day with a temperature of about 20°C, compared to two consecutive days of 37°C previously, but still the outside level was above 3, at about 10am.

In addition, they are recommending that people who work out of doors use skin protection all the year round because even levels 1 and 2 can cause damage.

Very interesting stuff. The Sunsmart scheme was first introduced in the 1980s and it's about now that the benefits are being felt in terms of reduced levels of skin cancer amongst young people. People over 40 who were exposed to high UV levels when young will still continue to suffer high rates of skin cancer.

[hellymedic]

I am no expert on these matters.

What I understand is that UV radiation is higher energy because it has a shorter wavelength and it is   the high energy that does the damage.

Australia is much closer to the Equator than UK so the sun's rays hit at a much steeper angle, effectively increasing the dose of radiation over a given area.

I am unfamiliar with the scoring system but as the ozone layer  thins, it strikes me as wise  to reduce summer sun exposure as much as possible and remember that Spring sun burns!

[Kim]

In the absence of clouds,  IR - like visible light - is a simple function of the sun's position in the sky (stronger at the equator, weaker at the poles), but since UV is attenuated by ozone, and AIUI the ozone layer isn't consistent, UV's correlation with latitude is less intuitive.  The infamous ozone hole was a primarily southern hemisphere thing.

[Asterix, the former Gaul.]

Do people who live in hot countries invariably get skin cancer? I notice people in France doing outdoor jobs a lot but they are invariably very tanned and so should be high risk.

When I lived in Cyprus I loved going out in the sun and was deeply tanned. On coming to the UK I slowly got paler and it was several years before I realised I could get sunburn! 

Perhaps skin cancer is the penalty paid for our increasingly indoor lives?

[mrcharly-YHT]

The hole in the ozone layer over the antarctic was 'thinning' rather than an absolute hole and extended as far as Australia at times.

UV can penetrate light clothing.
UVA can penetrate most glass, so you get a lot of Australians develop skin cancer on one side of their face (cars with aircon, keeps them cool, but the UVA comes through the driver-side window and does the damage to their face).
UV can also penetrate water, so you can be swimming, feel cooled but still be getting skin damage. Hence the Aussie limb-covering swimsuits (it was an aussie who invented the burkini and that's just a slight extension of what is quite common there anyway). Those didn't exist when I lived there, we swam in budgie-smugglers.

It is scary stuff. My brother and his wife have had multiple minor skin cancers removed and their generation regard that as normal. Ditto for my parents when they were still alive. We grew up being relatively careful, wearing hats most of the time, slathering ourselves with 'pink zinc' sunblock when working outside on the farm.

I have a high degree of hypochondria/paranoia about skin cancer. I'm in that demographic your daughter is mentioning (high rates).

[Canardly]

Anyone asked the indigenous people how they deal with this?

[nicknack]

Anyone asked the indigenous people how they deal with this?

A few tens of thousands of years acclimatisation and very dark skin.

[mrcharly-YHT]

It's kinda proof that freckly mayos don't really belong there.

[Canardly]

A bit dated and English  British but makes the point.

Mad dogs and Englishmen go out in the midday sun,
 The Japanese don´t care to, the Chinese wouldn´t dare to,
 Hindus and Argentines sleep firmly from twelve to one
 But Englishmen detest-a siesta.
 In the Philippines they have lovely screens to protect you from the glare.
 In the Malay States, there are hats like plates which the Britishers won't wear.
 At twelve noon the natives swoon and no further work is done,
 But mad dogs and Englishmen go out in the midday sun.

Cancer rates due to UV are lower but are by no means absent from Indigenous people.

[Whitedown Man]

Anyone asked the indigenous people how they deal with this?

A few tens of thousands of years acclimatisation and very dark skin.

Other way round. As Homo Sapiens migrated out of Africa melanin no longer conveyed as significant an evolutionary advantage and those with paler skins were more likely to survive to child-bearing age. Whilst in tropical climes, the evolutionary advantage of higher melanin levels continued to outweigh the evolutionary disadvantage of the gene mutation that leads to sickle cell anemia, in non-tropical climes the position was the reverse. Hence darker skin remained the norm closer to the equator, and lighter skin became the norm further from the equator.

[Kim]

Also, in evolutionary terms, you only have to survive long enough to raise your children.  Doesn't matter what happens to you after that.

[orienteer]

Not necessarily! The longer life expectancy of women has been attributed to grannies being more useful than granddads in helping to bring up grandchildren.

[T42]

Anyone asked the indigenous people how they deal with this?

A few tens of thousands of years acclimatisation and very dark skin.

Other way round. As Homo Sapiens migrated out of Africa melanin no longer conveyed as significant an evolutionary advantage and those with paler skins were more likely to survive to child-bearing age. Whilst in tropical climes, the evolutionary advantage of higher melanin levels continued to outweigh the evolutionary disadvantage of the gene mutation that leads to sickle cell anemia, in non-tropical climes the position was the reverse. Hence darker skin remained the norm closer to the equator, and lighter skin became the norm further from the equator.

Curiously, high blood cholesterol conveys some protection against UV. Scandinavians have much lower levels of melanin than those from further south, and it is reckoned that this explains their higher average levels of cholesterol, which also carried over to their descendants in the lands they occupied or intermarried with.  Mrs T is from Yorkshire and was always being told by the doc to eat less meat, before his got it through his head that she doesn't eat any.

[rogerzilla]

Not necessarily! The longer life expectancy of women has been attributed to grannies being more useful than granddads in helping to bring up grandchildren.

ISTR that when you correct for unhealthy lifestyle choices like heavy drinking, smoking and risk taking, men live about as long as women.

[Nelson Longflap]

I'd expect cyclists choosing nice days to do long rides would have some elevation in skin cancer risk, especially if time off the bike is spent indoors ... however I'm not sure I really want to know how much more.

I'm not aware of any studies, but personally I do try to cover up (legs are difficult tho), always wear a buff, and in summer I wear a cap rather than a helmet (on the grounds that the UV hazard exceeds the crashing hazard - but I can't prove that, and nobody believes me). I write as somebody whose 2005 summer was ruined by daily skin cancer treatment.

[TPMB12]

There are a few activity trackers with uv sensors apparently. You can also buy uv sensors that look l like watches without a face.

As far as uv and ir exposure goes i got badly sunburnt one glorious February day walking on a Scottish hill in winter. We'd made it up a long snow slope and the top was snow free. We enjoyed snoozing in the sun with sleeves rolled up.

We got no sunburn on our arms, forehead, neck or any usual places. We all got sunburnt under our noses and bottom lip. Basically only the places that could be reached by reflection off the snow. In February too!

The only question i have is whether the uv damage was increased with the reflection? I suspect the ir damage was worse with reflection, sunburn, was worse than non-reflected ir. Is it the same with uv?

[Asterix, the former Gaul.]

The Danish Cancer Society is spreading its "Help a Dane" message through a multilingual series of videos parodying a government-style announcement. Each one sees TV presenter Mikael Bertelsen solemnly address the people of France, Greece, Italy, Spain and Thailand in their own languages, while flanked by a choir of sunburnt and swimsuit-clad Danes. The five countries are the top destinations for Danish tourists heading abroad.
"We Danes love your country, but there is a problem," Mr Bertelsen says. "The strong sun is harmful to our delicate skin and every day a Dane dies from skin cancer. We know you have a lot on your plate, but we respectfully ask for your support. Help a Dane in the sun."...


...Denmark has one of the highest cancer rates in the world, partly due to high diagnosis rates but also because of lifestyle factors. The Danish Cancer Society notes that estimated annual skin cancer cases are almost double the number in France, when differences in age distribution are taken into account.

As far as uv and ir exposure goes i got badly sunburnt one glorious February day walking on a Scottish hill in winter. We'd made it up a long snow slope and the top was snow free. We enjoyed snoozing in the sun with sleeves rolled up.

We got no sunburn on our arms, forehead, neck or any usual places. We all got sunburnt under our noses and bottom lip. Basically only the places that could be reached by reflection off the snow. In February too!

Altho' I am an outdoor type and can hack it in France without sunburn,  I don't take my shirt off outdoors and like a hat.  Nor would I go to sleep in the sun as sunbathing has never appealed to me.  The last couple of summers in S. France the sun has been very fierce indeed with little rain. 

Generally i can cycle ok as the breeze keeps me cool, but in 2015 when I visited Mont Ventoux the daily temp was in the mid or high 30s in June (they had bad fires later that summer) and very few people went out in the afternoon. The top of Ventoux was ok but as you descended it suddenly heated up at one point.  I cycled in the mornings and spent the afternoon asleep on the floor of my open van, possibly the coolest place on the campsite. 

[hellymedic]

Though reflected light does burn, I suspect TPMB12's burnt areas were those that usually NEVER get unshaded rays.

[woollypigs]

Yup the sun down under bites. We visited Melbourne in October in 2010. At 8am while getting ready for a bike ride, I could feel the sun biting away, like at noon on a scortio day in the UK. And I have a rather tough skin, takes a bit before I burn. We both applied SPF 50 on any bare skin and covered up with long sleeves, hat etc.

Edited to add. While there in 2012, the weather forecast changed the colour bar, cold -blue, hot - red. To include purple and black, eg. temperature over 50c.

Latest map looks mental ....



Hmm I can't find the one I saw, but just think the black area bigger.

[andyoxon]

Fair skin type and any sunburn are significant skin cancer risk factors.  I have freckled, non-tanning skin, and pretty much should wear sun block mid-March to October in UK. I grew up  in the tropics (Zim), and have had a range of skin cancer types (most serious @ age 23).  2015, in Wiltshire, I was sunburnt on a very sunny ride in early-April, when I failed to apply sun block.  So I'd say that in Aus, if the advice is to cover all skin types, having a wider warning season makes sense.    The sun's max height at noon in UK, mid April, is about the same as last week in August. In Melbourne sun height mid-Aug is similar to mid March in UK.  I gather that in Aus, cyclists are regarded as 'sun bathers' in terms of sc risk...

[L CC]

For cyclists:

https://youtu.be/HxvJq2-0vWM

[rogerzilla]

I had a solar keratosis cryogenically destroyed today.  More fun and a lot quicker than rubbing cream into the thing for two months.  Keratoses aren't cancerous but they sometimes turn into something that is, years later - so they are best dealt with.

[Nelson Longflap]

For cyclists:

https://youtu.be/HxvJq2-0vWM

Terrific resource fboab, thanks a lot.  It answered all my questions and more. I learned a lot on something as basic as how to treat road-rash!

A couple of years ago I did a tour of Portugal when daytime temps were always in the 30s and sometimes 40s. I wore baggy shorts, a wide brimmed hat, buff, long-sleeved close weave shirt (usually), and high spf suncream on legs and face, ears and any other exposed bits. It was a great holiday, and afaict despite the high sun exposure no bad effects either at the time or subsequently. Having watched the vid the sun protection you can wash into your clothes sounds useful.

Like rz I regularly get my solar keratoses zapped. It's a small risk, but our GP runs a regular zapping clinic, so once or twice a year seems sensible.

[hellymedic]

I suspect my tresses and clothing (including h*lm*t) have mostly kept the light off many of the areas mentioned in that video.

[andrew_s]

Other way round. As Homo Sapiens migrated out of Africa melanin no longer conveyed as significant an evolutionary advantage and those with paler skins were more likely to survive to child-bearing age. Whilst in tropical climes, the evolutionary advantage of higher melanin levels continued to outweigh the evolutionary disadvantage of the gene mutation that leads to sickle cell anemia, in non-tropical climes the position was the reverse. Hence darker skin remained the norm closer to the equator, and lighter skin became the norm further from the equator.

Sickle cell anemia is malaria, nothing to do with skin colour. Carriers are resistant enough that early deaths due to sickle cell disease are outweighed by fewer malaria deaths.
The evolutionary advantage of lighter skin in northern regions is that dark skin filters out enough UV that vitamin D production in the skin is inadequate, and the rates of other (non-skin) cancers go up, plus rickets and other problems.