Over two years of wastewater surveillance in Chile, cannabis consumption dropped over 90% while cocaine use increased tenfold, revealing a rapidly shifting drug landscape.
Drug policy researchers, epidemiologists, public health officials, and anyone interested in population-level drug use trends.
Cannabis down 90%; cocaine up 1,019%
What the researchers found
The first multi-year wastewater-based epidemiology study in Chile found cannabis consumption declined by over 90% while cocaine use increased more than tenfold (+1,019%). Ketamine emerged as a new psychoactive substance. Cannabis showed inverse associations with cocaine and ketamine use. Urban areas were persistent consumption hotspots.
Why it matters
This objective population-level data reveals dramatic shifts in drug use patterns that self-report surveys might miss. The substitution pattern (cannabis down, cocaine up) has important implications for drug policy and public health resource allocation in Latin America.
The numbers in context
3,198 samples from 33 treatment plants over 2 years. Cannabis: declined >90%. Cocaine: increased +1,019%. Strong positive correlation between cocaine and ketamine (rho = 0.83). Cannabis inversely correlated with both stimulants.
How the study worked
Weekly collection of 3,198 24-hour composite influent samples from 33 wastewater treatment plants across Chile's Biobio Region from September 2022 to August 2024. Metabolites measured by SPE/LC-MS/MS.
What this study cannot tell us
Single region of Chile may not represent the entire country. Wastewater data cannot identify individual users or demographics. The dramatic cannabis decline could partly reflect changes in product types or metabolite stability rather than purely reduced use.
How to read the evidence
Validated wastewater methodology with 3,198 samples over 2 years from 33 sites, providing robust population-level data for this region.
When this study was published
2026 study covering 2022-2024.
The bigger picture
The shift from cannabinoids to stimulants observed in this Chilean region mirrors trends seen in some other countries and may reflect changing drug markets, supply chains, or cultural preferences. Wastewater-based surveillance offers a complementary and potentially more accurate picture than traditional surveys.
Questions still open
- What is driving the substitution of cannabis for cocaine in this region? Is this pattern emerging in other Latin American countries?
Common questions
Why did cannabis use drop so dramatically?
How does wastewater testing work for drug surveillance?
Read the original research
Biobio Sentinel: Two years of illicit drug surveillance in South-Central Chile.
Journal of hazardous materials, 503, 141142
Citation
Reis, Andressa S; Corthorn, Francisca; Osses, Eduardo Suazo; Urzúa-Bilbao, Sebastian; Hepp, Matias I; Galbán-Malagón, Cristóbal. (2026). Biobio Sentinel: Two years of illicit drug surveillance in South-Central Chile.. Journal of hazardous materials, 503, 141142. https://doi.org/10.1016/j.jhazmat.2026.141142