Presence of Benzodiazepines in Aquatic Environments: A Systematic Review of the Literature

INTRODUCTION: Pharmaceuticals in aquatic environments are a growing environmental concern. Because of their widespread use and poor removal by conventional wastewater treatment, benzodiazepines are frequently detected in treated effluents. OBJECTIVE: To synthesise global evidence on the occurrence and distribution of benzodiazepines and their metabolites across the urban water cycle. METHODS: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed in performing this systematic review. Bibliographic databases PubMed (including PubMed Central and Medline), Embase and Scopus were searched, from the inception date to July 26th, 2024, using query terms related to benzodiazepines (BDZs) and water pollution. Titles, abstracts and full text of the articles were independently evaluated by six review authors. RESULTS: Of 1973 records identified, 119 studies published between 2001 and 2024 met the inclusion criteria. Most research (N = 102) was conducted in European countries, followed by Asia (N = 29), America (N = 16), Africa (N = 5) and Australia (N = 2). Reported BDZ concentrations varied widely across the included studies, ranging from below analytical detection limits to several thousand ng/L, depending on the specific compound, sampling strategy, analytical technique, and environmental matrix. Most of the included studies searched BDZs in surface water (N = 61), followed by wastewater treatment plants (WWTP) effluents (N = 47) and WWTP influents (N = 40). Diazepam (N = 64 studies), oxazepam (N = 58 studies), lorazepam (N = 45 studies), temazepam (N = 31 studies) and alprazolam (N = 29 studies) were the most frequently detected compounds. CONCLUSION: Global data highlight the need for standardised monitoring frameworks, targeted sources mitigation, and advanced water treatment technologies capable of efficiently removing chemically stable pharmaceutical compounds. Strengthening these approaches is essential to reduce ecological risks, minimise human exposure, and safeguard the long-term integrity of aquatic ecosystems.