Keywords: Microtubules; Chromosomes; UV-B
; Oryzalin; Wheat
Influenza viruses and various nonpigmented bacteria are killed by UV-B
wavelengths in sunlight (Hollaender and Oliphant 1944).
Dramatic changes have been shown to occur in lake ecosystems exposed to the same intensities of UV-B
as those found in eastern Canada today.
Science journal recently reported that UV-B
radiation over Toronto, Canada had increased 35 percent per year in the winter and seven percent per year in the summer during the four-year frog study.
A 5-percent depletion of ozone would increase UV-B
exposure by the same amount as moving a mere 60 miles south.
"This was the first experiment to look at both carbon dioxide and UV-B
long-term," says coauthor Dylan Gwynn-Jones of the University of Wales in Aberystwyth.
In this way, eumelanin appears to protect the skin from the oxidation that UV-A and UV-B
Pollen from 34 species got mock suntans in the broadest survey yet of UV-B
effects on flowering plants.
Though plant cells are adept at amending the damage caused by UV-B
, the most dangerous portion of sunlight, scientists have been in the dark about how they do it.
These studies have provided concrete evidence that not only UV-B
-- the rays with wavelengths between 280 and 320 nanometers that cause sunburn -- but also light with longer wavelengths can induce cancer, says Setlow.
Measurements made in the crisp air of the Swiss Alps indicate that levels of ultraviolet-B (UV-B
) radiation there have increased during the last decade, apparently due to a thinning of the stratospheric ozone layer.
Though long UV produces DNA damage with only perhaps 1/1,000 the efficiency of mid-range UV-B
, he points out that UV-A penetrates light-colored skin more deeply than UV-B