ULTRAVIOLET IRRADIANCE OVER MEXICO-CITY

This article compiles and analyzes information on the interaction of b oth ground-level ultraviolet radiation and anthropogenic ozone in the extremely polluted atmosphere of Mexico City. Simultaneous anthropogen ic ozone and global flux (sun and sky) measurements were recorded in n ear-ultraviolet radiation (295-385 nm) for a 30-month period (March 19 90 to August 1992). Results reveal that under clear-sky conditions, hi gh concentrations of ozone (and presumably of other pollutants) impede UV-fluxes from reaching their maximum values. Furthermore, heavy clou d cover causes ozone concentrations to reach their minimum values toge ther with UV-minimum fluxes. Seasonal variation in W-irradiance is als o discussed. Findings indicate that maximum UV-fluxes occur in spring and summer and that minimum values occur in autumn and winter. Signifi cant daily local reductions in UV-fluxes (up to 50%) during afternoon hours in Mexico City can be attributed to air pollution. Finally, the growing incidence of rickets in children residing in the Mexico City m etropolitan area may be related both to dietary deficiencies and to th e UV-flux depletion on the ground.