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 can cause.
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 does.