Scientists expect that as the Earth's ozone layer decreases, the amount of biologically harmful solar radiation reaching the Earth increases. New research reveals, however, that this may not always be the case. In an article in the December 1991 Geophysical Research Letters, scientists reveal that the amount of solar ultraviolet radiation reaching the Earth's surface has decreased by as much as 5–18% in non-rural areas of industrialized countries, despite a global ozone loss. This decrease has been occurring since the Industrial Revolution.
According to S. C. Liu of the National Oceanic and Atmospheric Administration, S. A. McKeen of the University of Colorado, and S. Madronich of the National Center for Atmospheric Research, sulfate aerosols, which are formed from industrial sulfur dioxide emissions, are scattering the incoming solar radiation in the atmosphere and reducing the actual amount of biologically active ultraviolet radiation (UVB) that reaches Earth.