Complex sentence: Aside from the direct effect of ultraviolet radiation on organisms, increased surface UV leads to increased tropospheric ozone, ground-level increased ozone is generally recognized to be a health risk, as ozone is toxic due to its strong oxidant properties.
Split into simpler sentences: Aside from the direct effect of ultraviolet radiation on organisms, increased surface UV leads to increased tropospheric ozone, as noted above. Paradoxically, at ground-level increased ozone is generally recognized to be a health risk, as ozone is toxic due to its strong oxidant properties.