Chile's Cannabis Use Plummeted 90% While Cocaine Surged, Wastewater Data Shows
Over two years of wastewater surveillance in Chile, cannabis consumption dropped over 90% while cocaine use increased tenfold, revealing a rapidly shifting drug landscape.
Quick Facts
What This Study 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.
Key Numbers
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 They Did This
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.
Why This Research 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 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.
What This Study Doesn't 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.
Questions This Raises
- ?What is driving the substitution of cannabis for cocaine in this region?
- ?Is this pattern emerging in other Latin American countries?
Trust & Context
- Key Stat:
- Cannabis down 90%; cocaine up 1,019%
- Evidence Grade:
- Validated wastewater methodology with 3,198 samples over 2 years from 33 sites, providing robust population-level data for this region.
- Study Age:
- 2026 study covering 2022-2024.
- Original Title:
- Biobio Sentinel: Two years of illicit drug surveillance in South-Central Chile.
- Published In:
- Journal of hazardous materials, 503, 141142 (2026)
- Authors:
- Reis, Andressa S, Corthorn, Francisca, Osses, Eduardo Suazo, Urzúa-Bilbao, Sebastian, Hepp, Matias I, Galbán-Malagón, Cristóbal
- Database ID:
- RTHC-08579
Evidence Hierarchy
Follows a group of people over time to track how outcomes develop.
What do these levels mean? →Frequently Asked Questions
Why did cannabis use drop so dramatically?
The study documents the trend but does not explain it. Possible factors include shifting drug markets, changing user preferences, or supply chain changes in the region.
How does wastewater testing work for drug surveillance?
Wastewater treatment plants receive sewage from entire communities. By measuring drug metabolites in the incoming water, researchers can estimate population-level drug consumption without relying on self-reports.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-08579APA
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
MLA
Reis, Andressa S, et al. "Biobio Sentinel: Two years of illicit drug surveillance in South-Central Chile.." Journal of hazardous materials, 2026. https://doi.org/10.1016/j.jhazmat.2026.141142
RethinkTHC
RethinkTHC Research Database. "Biobio Sentinel: Two years of illicit drug surveillance in S..." RTHC-08579. Retrieved from https://rethinkthc.com/research/reis-2026-biobio-sentinel-two-years
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.