The widespread use of psychoactive substances, combined with their incomplete removal in conventional wastewater treatment plants, has led to the increasing environmental presence of biologically active compounds now classified as emerging contaminants. These include pharmaceuticals such as clonazepam, a benzodiazepine prescribed for anxiety and epilepsy, and widely consumed stimulants like caffeine and nicotine. After ingestion, these substances are metabolised and excreted mainly via urine, ultimately entering wastewater systems and aquatic environments, where they persist at ng/L–µg/L concentrations.
Caffeine, nicotine, and clonazepam are among the most commonly detected psychoactive contaminants in surface waters. Although their effects on humans are well understood, their impact on aquatic organisms, especially during early development, remains poorly characterised. While these contaminants often co-occur, understanding the specific role of each compound is crucial for ecological risk assessment.
This preliminary study examined the individual effects of caffeine, nicotine, and clonazepam on the embryonic development of Xenopus laevis, a widely used vertebrate model in ecotoxicology. Embryos were exposed from the 4–8 cell stage using a modified FETAX protocol designed to better reflect environmentally relevant exposure. Concentration ranges similar to those found in surface and wastewater were tested. In addition to standard FETAX endpoints (mortality, body length, and malformations), we measured heart rate, embryo motility, and oxidative stress biomarkers to identify sublethal alterations.
Preliminary results revealed significant developmental abnormalities, including cephalic and abdominal oedema, intestinal defects, bent tail phenotypes, and altered dorsal pigmentation. LC₅₀, EC₅₀, and Teratogenic Index (TI) values confirmed a detectable teratogenic potential for all three compounds. Overall, these findings demonstrate that individual psychoactive contaminants, even at environmentally relevant concentrations, can disrupt early vertebrate development, highlighting their ecological importance and the need for further toxicity assessment.
