The present study investigated the degradation of levonorgestrel (LNG) and gestodene (GES) through an anodic oxidation process mediated by active chlorine species. The independent variables [LNG]₀ and [GES]₀, current density (mA cm⁻²), and [NaCl]₀ (mol L⁻¹) were optimized through a response surface methodology (RSM) based on a four-level central composite design (CCD). Specific energy consumption allowed CCD-RSM analysis and optimization. The decay of progestins was followed to verify the kinetics of the anodic degradation process. Chlorine monitoring showed that excess Cl⁻ concentration did not mean high hormones removal, as well as the excess of current density. Central point conditions ([NaCl]₀ = 0.07 mol L⁻¹, j = 32.5 mA cm⁻², [LNG]₀, and [GES]₀ 1.0 mg L⁻¹) proved to be the best operational option. The performance with real pharmaceutical wastewater confirmed model optimization (2.2 ± 0.2 kWh g⁻¹, with removals of 83.1 ± 0.9% and 75.1 ± 2.8% for LNG and GES, respectively). The selected condition was used for estrogenic activity and acute toxicity assays. The first allowed the identification of the initial estrogenic activity for the mixture of LNG and GES (924 E2-EQ ng L⁻¹). Additionally, the electrochemical process could decrease this environmental parameter by 74.6%. The progestin mixture was classified as acute toxicity to Daphnia similis, with a toxicity unit (TU) of 2.5 100/EC50%. After electrolysis, the hormone solutions reached a fourfold increase in TU value, classified as high acute toxicity.

Metformin (MET), an antidiabetic compound, has received increasing attention, as it cannot be effectively removed during conventional wastewater treatment processes and may act as an endocrine disruptor. Electron beam irradiation (EBI) is an eco-friendly process able to degrade and neutralize biohazardous pollution almost instantly. In this context, this study applied EBI to MET degradation and detoxification in aqueous solutions. A 98% MET degradation rate and TOC removal of 19.04 ± 1.20% at a 1.0 kGy EBI dose was obtained, with up to 65% mineralization reached at 5.0 kGy. Toxicity assays were performed with Vibrio fischeri, Saccharomyces cerevisiae, and Daphnia similis, and the findings indicate that generated byproducts were only more toxic to D. similis. This reveals the need to assess organisms belonging to different trophic levels. A cytotoxic assessment employing Allium cepa roots demonstrated no toxic effects concerning untreated and irradiated samples.

Water quality in urban streams is closely linked to socioeconomic conditions, particularly in densely populated and poorly sanitized areas. This study evaluates the physicochemical and microbiological quality of water in the Billings-Tamanduateí sub-basin and investigates its correlation with social indicators such as population density, informal settlements, and lack of sewage treatment. Water samples were collected from 14 sub-basins, analyzing parameters, including dissolved organic and inorganic carbon, total dissolved nitrogen, pH, dissolved oxygen, oxidation-reduction potential, conductivity, and the presence of enterobacteria (Escherichia coli, Enterococcus, and Pseudomonas aeruginosa). Statistical analyses revealed strong associations between water quality degradation and increased population density, lack of sanitation, and lower per capita income. The findings reinforce that socially vulnerable areas are the most affected, with higher levels of organic and microbiological contamination. Despite improvements in sewage collection over time, gaps in wastewater management persist, even in major metropolitan areas such as São Paulo. Future studies could expand the analysis to include less vulnerable regions for comparison and explore the impacts of climate change on urban stream water quality. The results highlight the urgent need for improved sanitation infrastructure and policies to mitigate contamination and protect public health.

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This study combines experimental and theoretical methods to explore the photochemical stability of progestins in a climate-sensitive model system for urban reservoirs worldwide, with a focus on the Guarapiranga Reservoir in São Paulo, Brazil. The target contaminants were levonorgestrel (LNG) and gestodene (GES), synthetic progestins used in contraceptive methods. Photoinduced reaction kinetics showed that LNG’s indirect photolysis is affected by triplet excited states of chromophoric dissolved organic matter (3CDOM*), hydroxyl radicals (HO·), and singlet oxygen ( ¹ O ₂ ), in the order 3CDOM* > HO· > ¹ O ₂ . Conversely, for GES, the sequence was HO· ≈ 3CDOM* > ¹ O ₂ . Water quality data from 2022 to 2024, along with kinetic modeling, estimated half-lives of 6.9 ± 1.2 days for LNG and 25.8 ± 9.0 days for GES. Density Functional Theory (DFT) analysis identified key reactive sites and degradation pathways, aligning well with experimental results. An ecotoxicological assessment of the photo intermediates using the ECOSAR model showed notable toxicity to daphnia, fish, and green algae, especially after the addition of HO· radicals. These findings offer valuable insights into the environmental fate of LNG and GES in urban surface waters and contribute scientific evidence to decision-making on monitoring and removing emerging contaminants through advanced wastewater treatment technologies.