Wastewater-based epidemiology (WBE) can provide objective and timely information on the use of new psychoactive substances (NPS), originally designed as legal alternatives to internationally controlled drugs. NPS have rapidly emerged on the global drug market, posing a challenge to drug policy and a risk to public health. A WBE approach monitored over 300 NPS, plus fentanyl and norfentanyl, in influent wastewater from 12 European cities during March–June 2021. Fentanyl, norfentanyl, and eight NPS were quantified, with at least three substances found in each city. N,N-dimethyltryptamine and 3-methylmethcathinone (3-MMC) were the most common; 3-MMC had the highest mass loads, up to 24.8 mg/day/1000 inhabitants. Spatial trends and a changing weekly profile for 3-MMC were observed. WBE is a useful tool to complement common indicators for public health protection.
Ketamine use is widespread across northern Belgium, with consumption levels 7 to 11 times higher in 2023 than in 2012. Analysis of wastewater from 26 locations in Flanders and Brussels detected ketamine in 98% of samples, its metabolite norketamine in 96%, and dehydronorketamine in 76%. Higher population-normalized mass loads appeared in major cities and eastern Flanders. Weekend consumption increased, suggesting recreational use, while no seasonal trends were observed. By examining the ratio of ketamine to norketamine, researchers distinguished actual consumption from direct disposal. The findings indicate a stable, year-round pattern of ketamine use, and future monitoring should measure both parent drug and metabolite to avoid misinterpreting dumping events.