CSC & Community

In the 2025 European wastewater study, Chemnitz has the lowest cannabis value of all German cities and at the same time the highest value for methamphetamine, better known in Saxony as crystal. The obvious reading of this pattern of cannabis and meth in wastewater: people who turn to crystal leave cannabis alone, or the other way round. We checked whether the data support that. They do not. Cannabis and meth in wastewater: the figures from Chemnitz, Dresden and Erfurt During the measurement week in spring 2025, three eastern German cities recorded the highest levels of crystal meth in wastewater in Germany (in mg per 1,000 inhabitants per day): Chemnitz 381.6, Erfurt 371.2 and Dresden 327.2 (EUDA and SCORE, 2026b). This is not a one-off. Back in 2023 the same three cities were at the top, with 346.3 for Chemnitz, 334.4 for Erfurt and 316.8 for Dresden (EUDA and SCORE, 2024). For cannabis, the ranking looks different. Erfurt leads the German cities with 178.5, Dresden sits in the lower midfield with 114.6 and Chemnitz comes last with 74.9 (EUDA and SCORE, 2026b). The EUDA describes methamphetamine in Europe as a substance whose use has historically been concentrated mainly in Czechia and Slovakia (EUDA and SCORE, 2026a). Chemnitz and Dresden are close to the Czech border. The study does not offer this as an explanation of cause; the proximity is mentioned here only for context. Why you cannot set the figures against each other 381 versus 75 looks like a clear ratio. It is not. For methamphetamine, the lab measures the drug itself. For cannabis, it measures a metabolite, of which only a small share ends up in urine and a good part of which sticks to solids in the wastewater. On top of that, the typical doses of the two substances are very different. Milligrams of methamphetamine and milligrams of THC-COOH therefore cannot be compared. What you can compare is a city’s ranking for the same substance. Anyone who writes that Chemnitz consumes “five times more crystal than cannabis” is using numbers that were never designed for that. What the data say about a connection The substitution hypothesis (the idea that one substance replaces the other) can be tested another way. In winter 2023/24, TU Dresden measured cannabis and other substances in parallel at 24 German wastewater treatment plants and correlated the values with each other (TU Dresden, 2025). The result: there was no correlation between THC-COOH and methamphetamine (r = minus 0.064 in the final report, r = minus 0.07 at p = 0.28 in the short report; r is the correlation coefficient, 0 means no relationship). A pattern along the lines of “more crystal, less cannabis” does not show up. THC-COOH was most strongly linked to cotinine, a metabolite of nicotine (r = 0.671 in the final report). The researchers attribute this to the fact that cannabis is often smoked mixed with tobacco, and that situations in which people smoke can also encourage cannabis use. Erfurt fits this picture from the other side: the city ranks near the top for both substances, which does not fit a simple trade-off either. For context: a correlation across treatment plants says nothing about what individual people do. Whether someone switches from one substance to another at some stage of their life cannot be answered with wastewater. The substitution hypothesis is neither proven nor disproven by these data. But these data give it no support. What this means for the debate The comparison invites two wrong conclusions. The first: cannabis is harmless because crystal is more dangerous. Cannabis also carries a risk of dependence (on the mental health risks, see Cannabis and Psychosis: What the Numbers Actually Show). In the 2024 Epidemiological Survey of Substance Abuse in Germany, 1.0% of 18- to 64-year-olds met the criteria for cannabis dependence and a further 0.5% met those for abuse (Olderbak et al., 2025). The second: more cannabis could help against crystal. These data give no indication of that whatsoever, and cannabis is not a treatment for methamphetamine dependence. For Saxony and Thuringia, the meth in wastewater figures point to a problem of its own with its own dynamics. Prevention has to take both substances seriously, each on its own terms. What this means for your club Every cultivation association in Germany has to appoint a person responsible for prevention (for an overview of the obligations, see CSC Rules 2026: What the Gera Court Ruling Means for Cannabis Clubs). In Saxony and Thuringia, methamphetamine belongs in this work, even if the club’s work only concerns cannabis. Some members may know people who use crystal, or may have come into contact with it themselves. Anyone leading prevention conversations should know the regional support services for stimulants and be able to pass them on. And if someone in the local debate uses wastewater as an argument, the same applies as with any ranking: the measurement shows quantities in one week, not substitution effects and not harmlessness. Key takeaways Chemnitz, Erfurt and Dresden had the highest methamphetamine values of all German cities in 2025, as they did in 2023. For cannabis, Chemnitz is at the bottom and Erfurt at the top. Milligram values of different substances are not comparable, only a city’s position within one substance. TU Dresden found no correlation between cannabis and methamphetamine, but a clear one with the nicotine marker cotinine. The data do not support a substitution hypothesis. This does not make cannabis any less risky, and it is not a treatment for methamphetamine use. Sources EUDA and SCORE (2024). Raw data of the 2023 wastewater study (ww-data-long-2024). https://www.euda.europa.eu/sites/default/files/data/2024/ww2024/ww-data-long-2024-03-20.csv EUDA and SCORE (2026a). Wastewater analysis and drugs: a European multi-city study. Updated 18 March 2026. https://www.euda.europa.eu/publications/pods/waste-water-analysis_en EUDA and SCORE (2026b). Raw data of the 2025 wastewater study (ww2026-all-data). https://www.euda.europa.eu/sites/default/files/data/data-nodes/33337/versions/5/ww2026-all-data_en.csv Olderbak, S., Hollweck, R., Krowartz, E. M., et al. (2025). Psychoactive substance use in Germany: findings from the Epidemiological Survey of Substance Abuse (ESA) in 2024. Deutsches Ärzteblatt International, 122, 625 to 631. https://di.aerzteblatt.de/int/archive/article?id=246641 TU