Aerosols from anthropogenic sources contribute significantly to the scattering of solar radiation in the atmosphere over most populated areas. By using observed values of visual range we estimate that in non-urban areas of the industrialized countries the amount of biologically active solar radiation (UVB, 280 to 315 nm) reaching the surface has decreased by a range of 5 to 18% since the industrial revolution, primarily due to aerosols formed from emissions of sulfur dioxide (SO2). The UVB reduction in the industrialized countries may have offset partly or fully the UVB increases associated with current stratospheric ozone depletion at NH continental mid-latitudes. However, this offset is not expected to continue because the SO2 emissions are leveling off in the indusrialized countries.