SEVERAL-FOLD ENHANCEMENT OF BIOLOGICALLY EFFECTIVE ULTRAVIOLET-RADIATION LEVELS AT MCMURDO STATION ANTARCTICA DURING THE 1990 OZONE HOLE

Spectral measurements of biologically relevant radiation at McMurdo Station, Antarctica reveal ultraviolet (UV) irradiance levels at 305 nm in October exceeding by a factor between 3 and 6 "normal" values expected for undepleted ozone levels. This enhancement is directly related to the ozone depletion. The column abundance of stratospheric ozone derived from these measurements was as low as 145 Dobson Units (DU) in October, 1990. This is more than a factor of 2 lower than the value at solstice, and 100 DU less than in October, 1988. The dose rate for damage to the DNA molecule based on Setlow's action spectrum and UV radiation measured at noon is well above normal levels most of the time between October 1 and December 5 and is as much as three times the normal value for a few days at the end of October.