Pharmaceutical compounds are categorized as contaminants of emerging concern owing to their widespread consumption, persistence in the aquatic environment, development of antibiotic resistance in microorganisms, and growing evidence of chronic and endocrine disruption effects. Therefore, pharmaceuticals have been reported to exist in numerous environmental compartments, including surface water, groundwater, and drinking water throughout the world. The principal pathway of entry of these compounds into water bodies is via treated and untreated sewage. In aquatic environments, natural attenuation of pharmaceuticals takes place through various physical, chemical, and biological processes, including dispersion and dilution, volatilization, sorption onto sediments, biotransformation, and phototransformation. Among the listed attenuation processes, both direct and indirect phototransformation play an important role in deciding the fate of pharmaceuticals. In addition to cations and anions present in the aquatic environment, dissolved organic matter (DOM) can have multiple impacts during photolytic degradation, such as photosensitization, light screening, scavenging, and oxidative inhibition. The absorption of UV rays by DOM results in the formation of a variety of photochemically produced reactive radicals, such as triplet excited states of DOM (3DOM), hydroxyl radical (HO•), and singlet oxygen (1O2). This work presents a thorough assessment of various attenuation processes, with specific attention to aqueous photochemistry of pharmaceuticals evaluated using laboratory-scale and on-site observations. This review will highlight the general extent of natural attenuation for specific classes of pharmaceuticals and focus on the governing mechanisms—underlying such attenuation processes based on studies conducted worldwide.@en

The manufacture and use of pharmaceuticals for human and veterinary use is on the rise in Southeast Asian countries. Thus, the discharge from wastewater treatment plants may contain pharmaceuticals across a wide range of drug classes. Various regions in Southeast Asia are characterized by species richness, presence of threatened species and diversity of endemic species. The rapidly growing economy, aquaculture and livestock industries, increased incidence of infectious diseases, and change in lifestyle may adversely affect these biodiversity hotspots due to increased release of pharmaceuticals. This review focuses on use and occurrence of five commonly used pharmaceutics, i.e., atenolol, carbamazepine, diclofenac, sulfamethoxazole, and 17 α-ethinylestradiol in the influent and effluent of wastewater treatment plants and in various aquatic environments, i.e., surface water, groundwater, marine environment and sediments. Threats posed by these pharmaceuticals are evident from a discussion on their adverse effects on various freshwater species. Species sensitivity distribution (SSD) constructed for each of the pharmaceuticals using reproductive toxicity data for universal biomarker species reported in the literature, reveal the community level toxic effects of these pharmaceuticals in the aquatic ecosystem. Based on SSD and occurrence data, 17 α-ethinylestradiol poses the highest risk, while atenolol and carbamazepine poses negligible risk on reproductive toxicity/reproductive failure at the concentrations currently prevailing in the aquatic environment. The high risk posed by 17 α-ethinylestradiol is due to its ability to cause reproductive failure and/or vitellogenin induction at concentrations of the order of ng/L.@en