In the past, population-based surveys provided helpful information on who abused drugs (by age, gender, race).

Key datasets supplemented survey data with treatment admission data, poison control calls, and ER overdoses.

We can track in real-time which drugs a whole community uses by analyzing what ends up in wastewater.

Victor Hugo, in Les Misérables, refers to the city's sewer system as the "conscience of the city," where the waste products of society are gathered, bringing all secrets to light. Today, analyzing sewage or wastewater-based epidemiology (WBE) is a new way to determine which drugs are being used, when, and where. It can’t tell you, for example, that Johnny Jones of 15 Maple Street used ketamine a few days ago. It can tell you if there’s just been an upward surge in ketamine or other drugs in Johnny’s city.

When people take drugs, their bodies break them down, and they leave traces in urine and feces that flow into the sewer system for measurement.

Why is this important? Emergency room doctors and other healthcare providers need timely information on which drugs are currently being used. Public health and government agencies need current information to protect the public. The media needs accurate information to reduce harm, inform, and warn the public. And families, including users themselves, need to know about new drug combinations or risky drugs that could be lethal if ingested.

By analyzing drug metabolites in municipal sewage, WBE can provide drug information that also aids in preparedness. For example, wastewater signals precede overdose surges, permitting proactive interventions, such as targeted Narcan distribution to reverse opioid overdoses and EMS preparedness. Some cities, such as Denver, have implemented pilot programs to track high-risk substances and guide intervention tactics.

Traditionally, substance use epidemiology—who is using what drugs by age, gender, and race/ethnicity—relied on large annual population surveys, including the Monitoring the Future study, the National Survey on Drug Use and Health, and the Youth Risk Behavior Surveillance System. But these methods are subject to underreporting, recall bias, and long periods (9-18 months) needed to collect, tabulate, analyze, and report this data. While surveys often underestimate the prevalence and intensity of drug use, we still use these longitudinal annual surveys to provide comparisons (changes over time) and insights into attitudes and risk perceptions. However, individual numbers are affected by biases. Sometimes people lie about their drug use, and also recall bias undermines accuracy, particularly over long timeframes. These biases are most pronounced in high-risk populations.

Surveys assume individuals know which substances they used, but this assumption is increasingly invalid. Drug markets now are characterized by widespread adulteration and drug substitutions, as well as a proliferation of novel psychoactive substances. Individuals regularly consume drugs without knowing their composition, particularly with fentanyl contamination of drugs they thought they were taking, or emerging compounds such as xylazine adulterating the substance they believed they ingested. Self-reported data no longer reliably correspond with actual exposure.

Administrative drug datasets—treatment admissions, poison control calls, and emergency department visits—provide complementary information but are also limited. They capture acute events but are influenced by access to care, insurance coverage, public awareness, and policy changes. Even when accurate, such sources are not real-time, and often miss the full complexity of a changing drug use environment, such as the current polysubstance use and issues with drug adulteration.

An increase in emergency department visits could reflect increased drug use, but it may also reflect changes in EMT or diagnostic practices, or in healthcare-seeking behavior.

Problems with surveys became obvious during the early phase of the opioid crisis. As overdoses and deaths rose rapidly with illicitly manufactured fentanyl, survey-based estimates continued to show relatively stable opioid use. The discrepancy between stated prevalence and observed mortality highlighted a failure of surveillance systems to capture events in real time.

In contrast, with daily or weekly sampling, WBE enables rapid detection of changes in drug use patterns. It captures broad populations, including individuals not represented in surveys or clinical databases. It enables fine-grained geographic analysis, identifying localized trends and micro-epidemics (small, area-specific drug outbreaks).

Today's drug landscape, which often starts in clubs and events, is defined by synthetic compounds and an ever-shifting adulterated drug supply. Research by NYU Professor Joey Palamar has championed the shifting from reliance on self-reporting to the implementation of objective indicators of drug exposure. Surface drug sampling in nightlife settings by analyzing swabs from tables, cell phones, and other environmental surfaces may also provide real-time insight into drug trends and exposure.

New Data Revealed in Europe and the United States With Wastewater-Based Epidemiology

European data have provided the most comprehensive examples of WBE. Longitudinal monitoring from 2011 to 2025 demonstrated geographic patterning, with cocaine use accelerating, concentrated in Western and Southern Europe, and amphetamines more common in the North. Europe is better for WBE surveillance consistency and cross-national trends and epidemiology. The United States is better at detecting localized patterns, micro-epidemics, and rapid shifts in drug markets.

The most recent findings (2024–2025) from WBE in the United States highlighted a changing drug landscape. Cocaine residues increased by approximately 22 percent, and ketamine by 41 percent, while MDMA (Ecstasy or “E”) declined about 16 percent. Cannabis remained relatively stable, though variations across cities persisted. Ketamine, in particular, expanded quickly in the recreational drug landscape, rising alongside high cocaine use. Wastewater data also showed weekend drug peaks tied to nightlife-associated use.

Wastewater surveillance can also function as an early local health warning system. In Nantucket, Massachusetts, wastewater analysis found cocaine concentrations were three times the national average. These levels also showed strong seasonal variations linked to tourism. Wastewater data have revealed the use of new synthetic opioids beyond fentanyl. Fentanyl exposure seems to be stabilizing or declining, while other synthetic opioids are increasing. U.S. data have also revealed that drug use patterns differ not only by region but also by individual communities.

Private and academic networks in the United States monitor ~70 wastewater sites covering ~35 million people, detecting opioid trends, adulteration, and emerging synthetic drugs (nitazenes, xylazine combinations).

Instead of testing individuals, towns collect small amounts of wastewater from a treatment plant over a full day, giving an indication of drug use in the locale by testing a mixed sample representing thousands of people. In Tempe, Arizona, long-term wastewater surveillance showed opioid exposure was distributed broadly across the city rather than concentrated in specific “hotspots.”

Environmental Surface Sampling and Polysubstance Exposure

Complementing wastewater analysis, environmental surface sampling—particularly in clubs or nightlife settings—provides insight into drug exposure within specific environments. Recent studies consistently demonstrate that analyzing surfaces shows substances like cocaine and ketamine are gaining popularity in these settings.

Important analytical studies by Palamar have demonstrated discordance between perceived and actual drug use. Individuals who believe they have taken one substance (e.g., MDMA-ecstasy) commonly are found to have actually taken entirely different compounds. Perhaps most consequentially, he has shown that fentanyl is increasingly being detected among individuals denying opioid use.

Emerging approaches—including wastewater-based epidemiology, environmental sampling, and real-time EMT or toxicologic surveillance—have shifted monitoring upstream. They serve as leading indicators of drug use epidemiology, exposure, and supply patterns, enabling earlier, more targeted public health responses.

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