I heard from a reputable source, the Dead Sea is so far below sea level, that the atmosphere above is “deep” enough to absorb all harmful UV rays prior to reaching the surface.
If this is true, what is the typical, fair-weather air pressure at the Dead Sea? Would it be greater than 14.7psi? (30 mm Hg?) I would assume it must be!
I take it your “reputable” source never heard of the ozone layer…
The ozone layer blocks the overwhelming majority of UV rays. The lower atmosphere is nearly transparent to them. The few extra feet of normal atmosphere make no difference.
What in your book qualifies as a “reputable” source anyway? Egad.
I’d never heard this claim before, but it appears to be correct. According to one Dead Sea tourism site:
According to this site, “the Dead Sea has the highest recorded barometric pressure (800 mm Hg) on earth.”
UVA rays are not therapeutic. They don’t cause a sunburn as quickly as UVB rays, but they do cause longterm skin and eye damage and are linked to melanoma and other types of skin cancer. UVA rays also penetrate your skin further and cause more severe ageing and wrinkling than UVB rays do. I’d have to question the reliability of any site that promotes their location for it’s UVA rays.
See: http://www.aad.org/pamphlets/darker.html
Took some Googling but…
It appears that an 2000 meter increase in altitude causes about 20% increase in UV. But it’s obviously not an linear scale. So 360 meters would only be maybe 4%. Just waiting 20 minues after local noon would have a greater affect. Or better yet: visit someplace not so close to the equator!
On the sites I went to that advertised the UV claim, I also found such beauts as:
No sites were found making this claim that weren’t in either tourist promotion or skin condition treatment.
Again, nothing even close to a “reputable” source to back up the claim.
As a person with psoriasis who’s been subjected to all sorts of ads for Dead Sea therapy, I can say that ftg is spot-on (ha!) with the criticisms of these claims.
UV levels (both A and B) are most affected by how much ozone the sun’s light has to go through, so it’s much more about the angles than it is the small change in altitude. If you get a certain exposure at the Dead Sea at noon, it’ll be the same amount if you measure some few minutes after noon at sea level, or if you measure at sea level about 64 km north of the Dead Sea.
A year-old issue of the National Psoriasis Foundation’s magazine, the Bulletin, had a long article on Dead Sea therapy, and if I’m remembering correctly, a three-week stay there, with all the mud and pampering and everything else, was about as effective as standard dermatologist-office UVB therapy or psoralens plus UVA therapy (PUVA). The cost is probably more, however, as insurance isn’t likely to cover travel to Israel (depends on where you live, of course).
Oh, the mud they slather on may contain high-enough levels of coal tar to be photosensitizing, too, thus increasing the effects of the UV. (Coal tar is also therapeutic by itself.) This coal-tar-then-UVB therapy has been used medically for psoriasis since around 1925 or so, and is called Goeckerman therapy.