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What is the causal link behind the correlation of melanoma: negatively with UV index, negatively with ozone in the lower atmosphere, and positively with ozone in the upper atmosphere? Intuitively, melanoma would positively correlate with UV index, and negatively with upper atmospheric ozone.

Increased melanoma risk with higher latitude seems to be true on a global scale as well as locally in the US, but is reversed locally in the UK and Australia where melanoma rate negatively correlates with latitude. Could high population density and high ozone in the lower atmosphere be affecting a lower risk of melanoma?

  • It appears melanoma rates do not always negatively correlate with ozone in the upper atmosphere, and positively with high UV index.
  • It does appear that melanoma sometimes negatively correlates with population density and ozone in the lower atmosphere (caused by pollution in heavily populated areas).

In this study, Chinese individuals living in the US have a higher risk of melanoma than those in China. The map of the United States with the highest rates of skin cancer (below in blue) appears to strongly correlate with a map of ozone in the lower atmosphere (below in orange). enter image description here

Positively correlating latitude with rate of melanoma (higher towards the poles)

  • US map from CDC in cases per 100,000 enter image description here
  • World map from Nature enter image description here

Negatively correlating latitude and population density with rate of melanoma

UK

  • UK melanoma rate map from BBC enter image description here
  • UK population density map. Population density seems to negatively correlate with melanoma. enter image description here

Australia

  • Australia melanoma guidelines from Cancer.org.au stating the north has a higher risk for melanoma. enter image description here
  • Australia population density map. Population density seems to negatively correlate with melanoma. enter image description here

Negatively correlating latitude with UV index (higher towards the equator)

enter image description here enter image description here

Positively correlating temperate zones with ozone in the upper atmosphere.

enter image description here enter image description here

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  • $\begingroup$ That's two questions too many. Voting to close as 'Too broad'. $\endgroup$ – Jan Doggen Aug 7 '15 at 12:59
  • $\begingroup$ @JanDoggen - I think this can be migrated to sustainability SE. $\endgroup$ – gansub Aug 7 '15 at 13:09
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    $\begingroup$ This question isn't about sustainability, it's more of a health/medical question linked with aspects earth & cosmic science. $\endgroup$ – Fred Aug 7 '15 at 14:16
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    $\begingroup$ Where is the data on time spent outdoors? You talk about population density but lifestyle is key... it is predominantly coastal communities and other places where people have outdoor lifestyles (e.g. agricultural workers) that have the greatest risks... $\endgroup$ – farrenthorpe Aug 7 '15 at 14:41
  • $\begingroup$ Melanoma has more to do with a lifetime exposure to ultraviolet light, particularly lifetime sunburns than recent exposure. $\endgroup$ – Fred Aug 7 '15 at 14:48
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I cannot address your specific questions, but with regards to cancer, Cedric Garland has analyzed and presented similar data and attributed a lower incidence of cancer with a higher production of vitamin D at the lower latitudes as a possible reason. Mina Bissel at Berkeley labs and others have discovered that cells in isolation can lead to cancer. The other connecting link is that vitamin D promotes intercellular communications and thus may be aiding whatever process it is that leads to cancer. If you just google these names, vitamin D and cancer, you will find links to most if not all the papers.

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Regarding linking population density with cases of melanoma, that causal link occurs with all diseases. Cases don't occur where people don't live, they occur where people do live. Consequently, the likelihood of cases occurring increases with population density.

UV C radiation is blocked by nitrogen in the upper atmosphere. Upper atmospheric ozone acts as a barrier to UV radiation by absorbing most of the UV B radiation and whereas UV A radiation is not blocked by the atmosphere. Near surface ozone will not do anything to protect against UV radiation. Ozone is very reactive and is a powerful oxidizing agent and can damage skin.

Prolonged exposure to lower levels of UV radiation (low UV index) can be more damaging than short exposure to high UV index radiation. UV index is a poor guide to the likelihood of developing melanoma, or any other form of skin cancer. Duration of exposure is very critical.

When it's hot people to tend to stay out of the sun, which also reduces their exposure to UV radiation. When it's cooler, people tend to stay out in the sunshine, increasing their exposure to UV radiation.

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  • $\begingroup$ It appears heavily populated areas have a decreased rate of melanoma. $\endgroup$ – 12345678910111213 Aug 7 '15 at 22:09
  • $\begingroup$ @12345678910111213 I believe you only showed that with the UK (never showed melanoma map for Australia?) Fair theories include: people nearer big cities are more contemporary and focused on skin care... or visit dermatologists to get concern spots removed before they ever reach diagnosis... also, with the UK, I believe the London and Liverpool areas are fairly cloudy areas in comparison to much of the country, so maybe it's even coincidence... or possibly due to pollution reducing UV in cities?? Fred's suggestion, of lower exposure levels in cities, seems a very valid possibility. $\endgroup$ – JeopardyTempest Jul 12 '17 at 6:49

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