Comment by nabla9 | Hacker News Reader

Comment by nabla9 | Hacker News Reader

Parent Full thread

>The risk of skin cancer is elevated if you get sunburnt, if you expose your pale skin suddenly to the sun in the height of summer

This is very common skin cancer myth that can be debunked by few minutes of googling.

Any change in your natural skin color is a sign of skin damage and that damage is cumulative. Getting a tan is a sign of damage. Total UV dose you build up over time, rather than getting sunburnt, matters most (Sunburn is used as a proxy for skin cancer risk because it is related to individual sun sensitivity and UV exposure).

UV radiation is complete carcinogen. It's both a mutagen and a non-specific damaging agent. It's both tumor initiator and a tumor promoter. Three most common types of skin cancer are basal cell carcinoma (BCC) , squamous cell carcinoma (SCC) and malignant melanoma. Chronic cumulative exposure is associated with BCC and SCC and melanoma with sunburns and childhood exposure but melanoma may develop through multiple pathways.

Intuitively, based on what you're saying people around the Mediterranean (to take one region with a lot of Sun) should be dropping like flies due to these dangers you outline. Why don't they have a mortality rate affected by skin or other cancers? The Anglo world has been studying their diets due to the opposite perception.

>Why don't they have a mortality rate affected by skin or other cancers?

Do you have a source for that? A source that compares people from further North living in the Mediterranean region compared to further North for skin cancer?

So I just typed "skin cancer mortality rate by region" into DuckDuckGo and here are a few results from the first page:

the CDC on US Skin Cancer Rates By State: https://www.cdc.gov/cancer/skin/statistics/state.htm - if you squint there sure is a general north-south gradient, with LESS skin cancer in the South. Also note that "Melanoma is much more common among non-Hispanic whites than people of other races and ethnicities. More than 9 out of 10 cases of melanoma are diagnosed in non-Hispanic whites."

Forbes on "skin cancer hotspots of the world": https://www.forbes.com/2008/07/28/skin-cancer-hotspots-forbe...

relevant excerpt: "Studies have shown that while there is generally an increase in the incidence of melanoma as latitude decreases (closer to the equator), mortality from melanoma is four to six times higher in Nordic countries than in Mediterranean countries, according to the WHO." It then goes on to talk about cultural differences that essentially boil down to "people raised in sunny places get taught strategies for dealing with lots of sun".

You could probably find better studies, this is just five minutes of searching.

I’ve reduced what I’ve read about cancer and skin cancer down to the following:

Cancer is essentially triggered by damage to cellular DNA which results in a “pathological” strand. That strand then multiplies throughout our bodies through cell regrowth with the pathological DNA.

Sun light “flips the dice” with our skin cell DNA, among just generally harming our skin. Some people go their whole lives without any pathological DNA damage, and others not so much.

The skin cells of Caucasians have little to no natural defense to the sun’s rays.

Add as an anecdote: I saw a documentary with a girl born without any pigment (I think?). I forget the exact specifics. But she has to walk around in a 100% UV blocking hood and completely covering draped clothing when the sun is out. If any UV touches her skin she will get cancer then and there. She had a hole in the fabric of one of her hoods as a toddler and they had to do things to counteract that (I think they cut away that skin).

Presumably because evolution has selected genetic mutations which have provided protection against the amount of UV radiation people get in those geographic areas.

Don't forget behavior. You grow up in a sunny place, you learn the joys of sun-hats, parasols, and assorted other strategies as succinctly documented in Noel Coward's 1931 song "Mad Dogs & Englishmen"[1].

1: http://www.traditionalmusic.co.uk/folk-song-lyrics/Mad_Dogs_...

> Why don't they have a mortality rate affected by skin or other cancers?

What makes you assume that they don't?

Burden of cancer in the Eastern Mediterranean Region, 2005–2015: findings from the Global Burden of Disease 2015. https://link.springer.com/article/10.1007/s00038-017-0999-9

It doesn't say how much of that is associated with skin cancer, which is the cancer you're talking about.

Mediterranean sun is relatively benign. I am pale and used to have red hair. A full day in summer Mediterranean sun and I get a mild burn. If I go 20 minutes in New Zealand I’m toast, and mid summer it’s less than that. Even cloudy days can burn you easily here, and I’ve been burn in rainy days too. Ozone makes a hell of a lot of difference.

"This is very common skin cancer myth that can be debunked by few minutes of googling."

Please don't do this. Almost nothing is trivially googleable. For instance, the pages I'm reading say a tan is equivalent to about 2-3 SPF, which isn't a huge amount of protection (it corresponds to a 50-66% reduction in UV exposure). However, I'm not sure how to compare that 2-3 SPF to sunscreen measurements. SPF measurements for sunscreen are based on using something 4 teaspoons, or 1/3rd of a bottle per usage. No one I know does that.

On top of that, as a very pale person, I find that I don't get sunburnt because I put on SPF 15 and it's not strong enough--I get sunburnt when I don't reapply the SPF 50 after sweating for a few hours.

Or even better, trivially googling Basal Cell Carcinoma gets me to wikipedia which says that it's unclear if sunscreen even affects your risk of BCC. I probably shouldn't trust wikipedia, but that's what you're telling me to do when you say "it's easy to google for".

Short story: I'm still willing to believe that you're right. You clearly know more than I do about the subject. But "just google it" is not typically helpful.

I realize that "just google" is dangerous and I should rephrase my advice.

What I meant is to google basic public health information provided by national health authorities and international health organizations. They usually give a balanced view. For example, it's not beneficial to avoid going outside or not doing outdoor activities because they have other health benefits that outweigh skin cancer risk. Tanned skin is damaged skin but maybe you should accept the risk not avoid getting some tan.

For example:

https://www.surgeongeneral.gov/library/calls/prevent-skin-ca...

I'm not sure saying "tanned skin is damaged skin" directly answers the original question, or at least the way I'd ask it. Suppose, I go outside for a little bit at a time with my kids during the spring, and get something of a tan, then I go to the beach and am a lot of direct sun.[0] Although the articles say the tan is not much protection (2-3 SPF max), it is some. On the other hand, I had lots of exposure during the spring. Both effects are real, but which is bigger? For that matter, how big are the effects of those exposures? Can you just add up the entire time spent outside during peak hours?

[0] I do use sunscreen, but between getting in the water, uneven application or whatever else, I end up with part of my body burning a fraction on the time.

It's not clear that all UV is a complete carcinogen. Narrowband UVB is used for the treatment of psoriasis. It certainly causes a change in your natural skin colour but studies have not found that it elevates the risk of skin cancer e.g.:

https://www.ncbi.nlm.nih.gov/pubmed/18834483

You make it sound like it is a linerar relationship though, e.g. 5x 1h sun exposure over a week is the same as 1x 5h exposure. However, it is very much an exponential relationship, e.g. 50x 1h exposure is the same as 1x 5h.

Reply on news.ycombinator.com