From November 2023 through November 2024, RIVM monitored wastewater for six types of drugs. The researchers tested for the presence of cocaine, crystal meth, speed, XTC and two designer drugs: 3-CMC and 4-CMC. The results of the study are presented in the report Monitoring for drugs in Dutch wastewater – a pilot study (only available in Dutch).

Five measurements at twenty locations

RIVM conducted measurements at five times over the course of the year. Each measurement involved collecting daily wastewater samples at twenty different wastewater purification plants for one full week. These purification plants were located in big cities and small towns all across the Netherlands.

More drugs in cities

More drugs were used in big cities than in smaller municipalities. This difference held true even after compensating for the higher number of people living in cities.

Weekend drugs

Some drugs, like XTC, were used more on the weekend than on weekdays. Residues indicating the presence of those drugs were detected more often after weekends than on other days.

Designer drugs

Designer drugs are used less often than other drugs. Much smaller quantities of these designer drugs were found in the samples.

Figure: Drug levels per thousand inhabitants in one single day (mg/day/1000 inhabitants). The wastewater was sampled in 20 Dutch municipalities in November 2023. Samples were taken in these municipalities on every weekday. For each day, the figure shows the average of larger municipalities (more than 100,000 inhabitants, n = 10*, blue) and smaller inhabitants (fewer than 100,000 inhabitants, n = 8, red). *The data on XTC is for 9 larger municipalities instead of 10, because there was a possible drug dumping incident.