Wastewater research helps achieve a clearer overview of drug use in the Netherlands. This is the outcome of a pilot project by RIVM and the Trimbos Institute. The Trimbos Institute has been researching drug use in the Netherlands for years. Wastewater research may supplement these efforts in significant ways.
People who use drugs then excrete the residues of those drugs in their urine. As a result, drug residues end up in the sewer. RIVM conducted research in 20 Dutch municipalities to determine whether wastewater measurements could clarify drug use levels.
From late 2023 to late 2024, RIVM performed wastewater measurements at five points through the year, testing for specific drugs: cocaine, crystal meth, XTC, speed and two designer drugs (3-CMC and 4-CMC). Each measurement involved collecting wastewater samples at twenty different wastewater purification plants on several different days in the same week. These water purification plants were located in big cities and small towns all across the Netherlands.
Clear measurements of drugs in wastewater in big cities and small towns
The study showed that it is possible to achieve clear measurements of these drugs in wastewater. Since the measurements took place at municipalities of all sizes all across the country, the results offer a clear impression of drug use throughout the Netherlands. Wastewater research showed that there are differences in drug use in big cities compared to small towns. More drugs are almost always used in bigger towns and cities, even after compensating for the higher number of inhabitants. Designer drug use is low in all the municipalities included in the study. As a result, it is difficult to detect differences in designer drug use between different municipalities or measurement periods.
Drug use remains stable throughout most of the year
The measurements also showed that use of all drugs remained more or less stable throughout most of the year. However, researchers did find significantly higher levels of cocaine and XTC in wastewater after New Year’s Eve. The measurements also show that some drugs, like XTC, were used more on the weekend.
Annual wastewater research reveals changes in drug use
The pilot project shows that wastewater research is a valid and objective supplement to the current Trimbos studies. Since the measurements showed that drug use was stable throughout the year, a single measurement period once year will be sufficient to offer a clear overview of drug use levels in the Netherlands. If the measurement takes place at the same time every year, changes over time will be revealed.
RIVM carried out this study on drugs in wastewater under the auspices of the Ministry of Public Health, Welfare and Sports (VWS) and the Ministry of Justice and Security (J&V).