Abstract

Improving air quality by reducing ambient ozone (O₃) will likely lower O₃ concentrations throughout the troposphere and increase the transmission of solar ultraviolet (UV) radiation to the surface. The changes in surface UV radiation between two control scenarios (nominally 84 and 70 ppb O₃ for s... Show moreImproving air quality by reducing ambient ozone (O₃) will likely lower O₃ concentrations throughout the troposphere and increase the transmission of solar ultraviolet (UV) radiation to the surface. The changes in surface UV radiation between two control scenarios (nominally 84 and 70 ppb O₃ for summer 2020) in the Eastern two-thirds of the contiguous U. S. are estimated, using tropospheric O₃ profiles calculated with a chemistry-transport model (Community Multi- Scale Air Quality, CMAQ) as inputs to a detailed model of the transfer of solar radiation through the atmosphere (Tropospheric Ultraviolet-Visible, TUV) for clear skies, weighed for the wavelengths known to induce sunburn and skin cancer. Because the incremental emission controls differ according to region, strong spatial variability in O₃ reductions and in corresponding UV radiation increments is seen. The geographically averaged UV increase is 0.11±0.03 %, while the population-weighted increase is larger, 0.19±0.06 %, because O₃ reductions are greater in more densely populated regions. These relative increments in exposure are non-negligible given the already high incidence of UV-related health effects, but are lower by an order of magnitude or more than previous estimates Show less