Pharmaceuticals in the environment: An introduction to the ET&C special issue

Photodegradation fate of different dissociation species of antidepressant paroxetine and the effects of metal ion Mg2+: Theoretical basis for direct and indirect photolysis

Paroxetine (abbreviated as PXT) has been widely used as one of the standard antidepressants for the treatment of depression. PXT has been detected in the aqueous environment. However, the photodegradation mechanism of PXT remains unclear. The present study aimed to use density functional theory and time-dependent density functional theory to study the photodegradation process of two dissociated forms of PXT in water. The main mechanisms include direct and indirect photodegradation via reaction with ·OH and ¹O₂ and photodegradation mediated by the metal ion Mg²⁺. Based on the calculations, PXT and PXT-Mg²⁺ complexes in water are photodegraded mainly indirectly and directly. It was found that PXT and PXT-Mg²⁺ complexes were photodegraded by H-abstraction, OH-addition and F-substitution. The main reaction of PXT indirect photolysis is OH-addition reaction, while the main reaction of PXT⁰-Mg²⁺ complex is H-abstraction. All the reaction pathways of H-abstraction, OH-addition and F-substitution are exothermic. PXT⁰ reacts more readily with ·OH or ¹O₂ in water than PXT⁺. However, the higher activation energy of PXT with ¹O₂ indicates that the ¹O₂ reaction plays a minor role in the photodegradation pathway. The direct photolysis process of PXT includes ether bond cleavage, defluorination, and dioxolane ring-opening reaction. In the PXT-Mg²⁺ complex, the direct photolysis process occurs via a dioxolane ring opening. Additionally, Mg²⁺ in water has a dual effect on the direct and indirect photolysis of PXT. In other words, Mg²⁺ can inhibit or promote their photolytic reactions. Overall, PXT in natural water mainly undergo direct and indirect photolysis reactions with ·OH. The main products include direct photodegradation products, hydroxyl addition products and F-substitution products. These findings provide critical information for predicting the environmental behavior and transformation of antidepressants.

A Review of Pectin-Based Material for Applications in Water Treatment

Climate change and water are inseparably connected. Extreme weather events cause water to become more scarce, polluted, and erratic than ever. Therefore, we urgently need to develop solutions to reduce water contamination. This review intends to demonstrate that pectin-based materials are an excellent route to detect and mitigate pollutants from water, with several benefits. Pectin is a biodegradable polymer, extractable from vegetables, and contains several hydroxyl and carboxyl groups that can easily interact with the contaminant ions. In addition, pectin-based materials can be prepared in different forms (films, hydrogels, or beads) and cross-linked with several agents to change their molecular structure. Consequently, the pectin-based adsorbents can be tuned to remove diverse pollutants. Here, we will summarize the existing water remediation technologies highlighting adsorption as the ideal method. Then, the focus will be on the chemical structure of pectin and, from a historical perspective, on its structure after applying different cross-linking methods. Finally, we will review the application of pectin as an adsorbent of water pollutants considering the pectin of low degree methoxylation.

Environmental loadings of Active Pharmaceutical Ingredients from manufacturing facilities in Canada

Recent evidence has revealed that cities with pharmaceutical manufacturers have elevated concentrations of Active Pharmaceutical Ingredients (APIs) in their receiving water bodies. The purpose of this study was to gather information on direct sewer discharges of APIs during their manufacturing and processing from five pharmaceutical manufacturing facilities in Ontario, Canada. Drug classes and maximum reported concentrations (ng/L) for which APIs were directly discharged included: antidepressants (paroxetine - 3380 and sertraline - 5100); mood stabilizer (carbamazepine - 575,000); antibiotics (penicillin - 14,300); analgesics (acetaminophen - 461,000; codeine - 49,200; ibuprofen - 344,000; naproxen - 253,000 and oxycodone 21,000); cardiovascular drugs (atorvastatin - 893 and metoprolol - 7,333,600) and those drugs used for blood pressure control (amlodipine - 22,900; diltiazem - 1,160,000; furosemide - 1,200,000 and verapamil - 7340). Based on flow and water usage data from the individual facilities, the maximum concentrations for acetaminophen, ibuprofen, carbamazepine, diltiazem and metoprolol correlate to approximately 200, 220, 390, 420 and 14,200 g respectively, of lost product being directly discharged to the sewers daily during active manufacturing. This survey demonstrates that direct point source discharges from pharmaceutical manufacturers represent a key source of pharmaceutical pollution to receiving sewersheds. Onsite recovery of product or treatment at pharmaceutical manufacturing or processing facilities to reduce the sewage loadings to receiving treatment plants, product loss and potential environmental loadings is strongly recommended.