Phosphodiesterase-5 (PDE-5) Inhibitors as Emergent Environmental Contaminants: Advanced Remediation and Analytical Methods

Pharmaceuticals, fundamental in therapy and the prevention of known pathologies, are responsible for environmental pollution. These substances, called "emerging contaminants, " are harmful to human health because they enter the environment in quantities exceeding the natural self-capacity purification of the ecosystems. Furthermore, wastewater treatment plants (WWTPs) cannot remove these substances, which can undergo chemical/biological transformations in the environment, thus forming by-products, sometimes more toxic than the parent molecules; successively, they move into rivers and could reach the drinking water supplies. All these phenomena represent a severe public health problem. Therefore, the Water Framework Directive by European Union imposed the monitoring of drugs' levels in aqueous matrices. Every two years, the EU carefully updates the list of potential water pollutants, called the Watch List, including pharmaceuticals, to evaluate their risk on the aquatic environment. The last Commission Implementing Decision (EU 2018/840) comprises several substances of primary concern. In addition, the scientific community is giving particular attention to other pharmaceuticals not yet on the Watch list, whose markets are in growth; particularly, the Phosphodiesterase 5 (PDE-5) inhibitors used for the pharmaceutical treatment of erectile dysfunction (ED) in men. This review discusses the presence of PDE-5 inhibitors in environmental systems, their toxic effects, the different kinds of removal, and the analytical methods normally adopted for their detection. In addition, the study helps figure out the best possible strategy to tackle pharmaceutical pollution by using analytical and advanced diagnostic methods.