Parabens as emerging contaminants: Environmental persistence, current practices and treatment processes

The unmatched levels of water contamination by emerging contaminants (ECs), such as endocrine disrupting compounds (EDCs) and pharmaceuticals, has become a relevant environmental problem due to their considerable ecotoxicity and associated health issues. Among the EDCs, parabens are a group of preservative compounds widely used on a daily basis in cosmetic, personal care products, food products and pharmaceuticals. Parabens can cause a variety of adverse health effects, particularly in the endocrine system. They are frequently detected in environmental matrices (up to 170.9 μg/L in surface waters), with a critical presence and persistence in aquatic systems (up to 36,000 h of a half-life time). Despite the advances in wastewater treatment technologies, the design of existing treatment plants is not suited to remove these ECs, generating wastes containing high concentrations of persistent contaminants or chemically unstable products and can demand high amounts of energy for operation. Moreover, there is a lack of published health standards that provide guidelines for treating parabens, highlighting the need for innovative approaches. Microalgae bioremediation is starting to evolve scientifically as feasible for the removal of parabens, namely with laboratorial and pilot scale studies achieving removal efficiencies close to 100%. However, large scale microalgae-based treatment of wastewaters containing parabens and other ECs faces challenges of process optimization. This study reviews the physicochemical properties of parabens, their regulation and environmental persistence. It further provides a rigorous analysis of parabens removal by the existing treatment process in comparison with microalgae-based systems, reinforcing the need for further research.