Trends in <scp>UV</scp> radiation and ozone in South America and Antarctica

Solar ultraviolet (UV) radiation and atmospheric ozone are critical determinants of ecosystem dynamics and human health. This study aimed to assess the terrestrial profile of solar UV radiation and its genotoxic risk in the South American subtropical region (29° S 53° W). From 2005 to 2021, ground-based physical sensors showed an increase of approximately 50% in UVB (280-315 nm; +0.28 kJ/m² per year), but no significant trend in UVA (315-400 nm). Despite the existence of four defined climatic seasons, simultaneous measurements using UVA, UVB, and DNA-based sensors revealed two distinct UV seasons: a high-UV season encompassing spring and summer, and a low-UV season encompassing winter and autumn. Notably, spring sunlight was found to be as genotoxic as summer sunlight, and even winter and autumn sunlight may pose a genotoxic risk on cloudless days, as indicated by measurements of cyclobutane pyrimidine dimers and oxidized bases. Given the rising UVB levels without an increase in UVA, we investigated satellite-derived ozone data from NASA's ozone monitoring instrument (OMI) and total ozone mapping spectrometer (TOMS) sensors across South America and Antarctica. Overall, analysis from 1979 to 2021 showed negative ozone trends at 2° S 54° W (Santarém), 23° S 46° W (São Paulo), and 29° S 53° W (Santa Maria) even after the onset of the Montreal Protocol, while positive trends were observed at 53° S 70° W (Punta Arenas) and 62° S 58° W (Brazilian Antarctic Station) following the protocol. Strikingly, the UVB and ozone trends observed across seasons suggest that ozone is being transported poleward persistently rather than seasonally, possibly driven by a climate change-induced acceleration of the Brewer-Dobson Circulation. This persistent pattern demonstrates that ozone depletion at low and mid-latitudes is not limited to springtime but persists throughout the year. Our findings indicate that low- and mid-latitudes in South America are experiencing climate changes, stratospheric ozone depletion, and increased UVB incidence, resulting in heightened genotoxic risks, highlighting the urgent need for monitoring and mitigation strategies.