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Gestagens are common pollutants accumulated in the aquatic ecosystem. Gestagens are comprised of natural gestagens (i.e. progesterone) and synthetic gestagens (i.e. progestins). The major contributors of gestagens in the environment are paper plant mill effluent, wastewater treatment plants, discharge from pharmaceutical manufacturing, and livestock farming. Gestagens present in the aquatic environment interact with progesterone receptors and other steroid hormone receptors, negatively influencing fish reproduction, development, and behavior. In fish, the gonadotropin induces 17α, 20β-dihydroxy-4-pregnen-3-one (DHP) production, an important steroid hormone involved in gametogenesis. DHP interacts with the membrane progestin receptor (mPR), which regulates sperm motility and oocyte maturation. Gestagens also interfere with the hypothalamic-pituitary-gonadal (HPG) axis, which results in altered hormone levels in fish. Moreover, recent studies showed that even at low concentrations exposure to gestagens can have detrimental effects on fish reproduction, including reduced egg production, masculinization, feminization in males, and altered sex ratio, raising concerns about their impact on the fish population. This review highlights the hormonal regulation of sperm motility, oocyte maturation, the concentration of environmental gestagens in the aquatic environment, and their detrimental effects on fish reproduction. However, the long-term and combined impacts of multiple gestagens, including their interactions with other pollutants on fish populations and ecosystems are not well understood. The lack of standardized regulations and monitoring protocols for gestagens pollution in wastewater effluent hampers effective control and management. Nonetheless, advancements in analytical techniques and biomonitoring methods provide potential solutions by enabling better detection and quantification of gestagens in aquatic ecosystems. • DHP is an important steroid for sperm motility and oocyte maturation. • DHP interacts with the membrane progestin receptor, which controls sperm motility and oocyte maturation. • Gestagens are common pollutants in the aquatic ecosystem. • Gestagens negatively affect fish reproduction, behavior, and development. [ABSTRACT FROM AUTHOR]

This work provides a first-time comparative study examining the photocatalytic activity of functionalized TiO 2 -based composites to eliminate naphthol blue in Batik wastewater. Reduced graphene oxide (RGO) was synthesized by oxidizing solid graphite using the Hummers' method followed by sonication and reduction. N-doped TiO 2 (N–TiO 2) was synthesized from titanium tetrachloride (TiCl 4) and urea (CH₄N₂O) precursors by the sol-gel method. N–TiO 2 modified RGO (RGO/NT) was synthesized using a hydrothermal method from N–TiO 2 and RGO. Prepared TiO 2 -based composites and commercial TiO 2 , for comparison were characterized using Fourier transform infrared spectrometer (FTIR), X-Ray diffractometer (XRD), scanning electron microscope-energy dispersive X-ray (SEM-EDX), and UV–Vis diffuse reflectance spectrometer (UV–Vis DRS). FTIR characterization indicated Ti–N bonding in N–TiO 2 and RGO/NT. XRD patterns showed that commercial TiO 2 had a rutile phase, while N–TiO 2 and RGO/NT had an anatase phase with crystal sizes of 30.09, 16.28, and 12.02 nm, respectively. SEM results displayed the presence of small and glossy white N–TiO 2 dispersed on the surface of RGO. Characterization using UV–Vis DRS showed that the band gap energy values for TiO 2 , N–TiO 2 , and RGO/NT were 3.25, 3.12, and 3.08 eV with absorption regions at the wavelengths of 382, 398, and 403 nm, respectively. The highest photocatalytic activity for RGO/NT for degrading naphthol blue was obtained at pH 5, with a photocatalyst mass of 60 mg, and an irradiation of 15 min. Photocatalytic degradation by RGO/NT on Batik wastewater under visible light showed higher effectivity than under UV light. [Display omitted] • Comparative study examining TiO 2 -based composites was briefly discussed. • N doping and RGO loading enhanced absorption ability of TiO 2 towards visible light. • RGO/NT demonstrated great photocatalytic activity for Batik wastewater treatment. [ABSTRACT FROM AUTHOR]