Skin cancer's secrets unveiled

news.com.au ^ | May 8, 2003 | World exclusive by Jen Kelly

[kstewskis]

re: the humidity vs. skin cancer incidence issue:

Hang 'em, I took physics in college, your explanation was interesting, but not entirely correct. The amount of water vapor in the air has NO bearing on the amount of UVA, UVB or UVC rays of the sun beating down on the earth's surface.

Refraction of light, yes, will "appear" like more of a thermal/heat burn, but has no bearing from the harmful amount of burning ultraviolet rays of the sun. It is the chemical reactions from the UVA, UVB, ect...that occur within the skin cells that we believe cause skin cancer.

I wrote the American Cancer Society about this, and this was the reply I received this morning:

Thank you for contacting your American Cancer Society.

Your message indicates that you would like to know why skin cancer is far greater in certain parts of the United States than others. It seems you are interested in knowing if humidity is a significant factor in developing skin cancer in these areas.

The vast majority of skin cancers are due to unprotected ultraviolet radiation (UV) exposure. Most of this radiation comes from sunlight. People who live in areas with year-round, bright sunlight have a higher risk. For example, the risk of nonmelanoma skin cancer is twice as high in Arizona compared to Minnesota. This is because of the length of time the sun is out for longer periods of the day, and the summer season is typically longer in areas like Arizona. Spending a lot of time outdoors for work or recreation without protective clothing and sunscreen increases your risk. The risk is also increased for people who live at high altitudes.

We hope this information adequately addresses your question.

Hope this helps. Be safe this summer everyone.

[hang 'em]

To find the effects of atmospheric water vapor on UV here:

http://rain.atmos.colostate.edu/AT622_section10.pdf

and look at the upper right hand figure on the first page. It is a plot of the absorption coefficients for several atmospheric components (e.g. CO, CO2, ozone, NO2, H2O, etc.) The horizontal axis is wavelength in nm (nanometers). UA, UB are roughly in the range 2 to 4 nm. Look at the curve labeled H20. You will see that water vapor (H2O) has an absorption of nearly 100% in at some parts of the UV spectrum. Therefore water vapor can have a significant effect on UV.

Now as to the response from the Cancer Institute, realize that they want people to know that cloud cover is not perfect protection from UV. Of course it's not... BUT IT HELPS! Also, my comparison was meant to be between the SW (e.g. Arizona) and the SE (e.g. Alabama, NOT Michigan), two states at the same latitude, but with vastly different levels of average UV.

Here's a common sense answer to the issue: If you have to be outside naked for 3 hours in the mid day, would you rather it be a cloudy day?

[kstewskis]

Here's a common sense answer to the issue: If you have to be outside naked for 3 hours in the mid day, would you rather it be a cloudy day?

Thanks for the link, but it doesn't change anything. You don't seem to understand that Arizona is not dry 100% of the time. The deadliest UV ray index readings come through here when our dewpoints reach in the 60 degree range.

As for your question, all it would do would be more comfortable while being out there under cloud cover, rather than in the sun. The damage would still be the same.

[hang 'em]

Compare AZ (9) and AL (5).

I've lived in both places. As far as the UV death rays go, AZ wins hands down!

[aShepard]

After my cancer doctor did some slice-em and dice-em on my face and ear, and since I am very fair and burn easily, I've taken my doctor's advice and use Blue Lizard, an Australian sunscreen.

http://www.bluelizard.net/BlueLizard/home.html

Great stuff, and though advertised as SPF 30+ doctor tells me that it's about SPF 100, but can't be advertised that way. Like the way it protects, but doesn't make your skin a greasy mess the forces you to sweat profusely.

Effective when chartering a yacht for a winter week in the Virgin Islands, but I did visit a tanning salon for a couple of visits before the trip to get a base coat of UV exposure.

Blue Lizard is hard to find, but their web-site has a retail locator. About $15 a bottle.

[kstewskis]

I've lived in both places. As far as the UV death rays go, AZ wins hands down!

there's no question about that! I've said it, and it's been stated ad hominem in research. It is well known.

The point is, humidity in the air is a "false" protection idea, in thinking that the UV rays aren't as harmful.

As far as humid Flori-duh and Texas, I guarantee you that someone living in Miami or Houston doesn't give a rat's patutti whether the index is a 9 there or a 10, as it is in AZ. Fact is, it's all deadly. When you live with malignant melenoma because you've spent too much time getting exposed to UV, it really doesn't matter, does it?

And, according to the graph you posted, it proves my point. I had mentioned Hawaii earlier. They have high humidity there, and the index surpasses even AZ.

Just my humble O, granted, places like Alabama aren't destination resort-type places that people flock to. The humidity is so high in those areas in the country, no one stays outdoors for long in the summer months. So, therefore, less chance of UV exposure would be expected.

That is reason why the ACS states it's the rate of exposure. You can spend a lot more time in the sun in the other areas where the index isn't as high, and expect to have the same damage as someone only spending a smaller amount of time outdoors in AZ when the index is high. That's all that means.

I've lived in the SW for 40 years and have been in the sun much of that time. Thanks be to God, I'm skin-cancer free, according to my last check this month.

My prayers go out to those who's spent a lot of time in the sun, without the protection, (who live where the indexes are less than AZ) who are battling skin cancer now.

[kstewskis]

One more thing I'd point out, might be of interest. The date on the graph (thanks, btw) is 5/15. Skies are overcast all over the Phoenix Metro area today.

UV index is still at 10. It will stay that way through most of the summer (I've actually seen it hit 11 in the papers...during monsoon season.)

[kstewskis]

thanks for that link!

[armed_in_sydney]

Most Australians grow up as beach babies,and 20 years ago it was rare for anyone to be using sunblock.Milky white or tan,it makes little difference to who gets skin cancer when you spend half your life on the beach.

[Hillary's Lovely Legs]

Thank you for the information on Blue Lizard. I am a red headed, green eyes, very fair skinned human. I went through severe sunburns and sun poisoning as a kid on our boat.

I just got on the crew of a sailing race team and am looking for a new high powered sunscreen.

[FourPeas]

My dad died of melanoma last June. Since then, we've slathered our sons in BullFrog every time they go into the sun for any length of time. It works great. Applies easily, smoothly and without getting your hands all greasy. We se the watermellon scented type for the boys and the plain for us adults. I buy it by the case when I can get it.

[aShepard]

"I just got on the crew of a sailing race team "

Good on you! Have fun.

As a kid, I had a crewcut, and sailing all day long made the top of my head an absolute mess. Now I have to wear a wide brim hat. Looks dorky, but a baseball cap keeps the top of what's left of the top of my ear exposed.

[FourPeas]

ACK! Make that BullFrog. Now, I'm off to write "The preview button is our friend" one hundred times.

[hang 'em]

It's even more overcast here (AL).

If you can, open this .pdf file

http://nadp.nrel.colostate.edu/UVB/publications/uvb_primer.pdf

Page eight (8) shows UV measurements for a clear day and a cloudy day, same place. Pretty much lays the issue to rest... Except: thin clouds and thick clouds can have different effects.

[kstewskis]

can you post it? I'm unable to open this link. thanks

[rangerwife]

I just had a spot removed from my back this afternoon that I was concerned about. It was also getting annoying because it was right on my bra line. The doc seems to think it is just a dermatofibroma. It popped up about 4 years ago after I had my son. Then I noticed it started to change colors...it got darker. I won't find out anything till next week, but hopefully it is nothing.

[hang 'em]

To illustrate these effects (primarily for clouds), the plots in Figure 7 are actual field measurements of UV irradiance at 305 nm on a clear day and cloudy day in Texas on March 28 (clear) and 30(cloudy). While there is cloud cover the entire day on the 30th, the UVB irradiance is still significant. As is illustrated in the previous figure, thin clouds actually scatter a significant portion of the UVB toward the earth while thick clouds scatter most back to space. Thus, clouds are not necessarily good protection from sun-burn.

The above is an excerpt from

http://nadp.nrel.colostate.edu/UVB/publications/uvb_primer.pdf

and can be viewed with Adobe Acrobat Reader/viewer available free. (Good reference on UV and skin cancer)

[Doctor Stochastic]

Here in NM the problem is altitude. Working at 7500ft means you are above most of the atmosphere. (I did have a cancer removed from the nose. It was the least problematic one but I don't remember which.)

Sunscreen is a good idea.

http://www.maui.net/~southsky/introto.html#basal

[Axenolith]

If you're really hard core you can grab those skin tags between your thumb and forefinger and just rip em off :)

We had a laborer a few years back who had a thumb sized one on the back of his neck. A project manager saw it one day and exclaimed "What the HELL is that!?!? Is that your unformed twin??? I thought it just winked at me!"