Victor Hugo, in Les Misérablesto the city’s sewer system”conscience “City” collects the waste of society and reveals all the secrets. Today’s analysis sewage or wastewater-based epidemiology (WBE) is a new way to determine which drugs are used, when and where. For example, Johnny Jones at 15 Maple Street can’t tell you what he used ketamine a few days ago. This possible Tell me, has ketamine or other drugs been rampant in Johnny’s town?
When people take drugs, their bodies break them down and leave traces in their urine and feces that flow into the sewage system to be measured.
Why is this important? Emergency room physicians and other health care providers need timely information which drugs are currently being used. Health and government agencies need up-to-date information to protect the public. The media need accurate information to reduce harm, inform and warn the public. Families, including users themselves, need to be aware of new drug combinations or dangerous drugs that can be fatal if ingested.
By analyzing drug metabolites in municipal sewage, WBE can provide drug information to aid preparedness. For example, wastewater alerts precede overdoses, allowing for proactive interventions such as targeted Narcan distribution to reverse opioid overdoses and EMS readiness. Some cities, such as Denver, have implemented pilot programs to manage high-risk substance monitoring and intervention tactics.
Epidemiology of Substance Use Traditionally – Who Uses What Drugs by Age? genderand race/ethnic origin— relied on large annual population surveys, including the Monitoring the Future survey, the National Survey on Drug Use and Health, and the Youth Risk Behavior Survey. But these methods are underreporting, it should be remembered biasand it takes a long time (9-18 months) to collect, tabulate, analyze and report this data. Although 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 bias. Sometimes people lie about their drug use, and misrepresentation can reduce accuracy, especially over long periods of time. Such biases are more pronounced in high-risk populations.
Requests refer to individuals to know which substances they used, but this speculation is growing. The drug market is currently characterized by widespread counterfeiting and drug substitution, as well as the proliferation of new psychoactive substances. Individuals use drugs regularly without knowing their contents, particularly fentanyl contamination of drugs they thought they had taken or emerging compounds like xylazine adulterating substances they thought they had ingested. Self-reported data do not reliably correlate with actual exposure.
Administrative drug data sets—treatment admissions, poison control calls, and emergency department visits—provide additional information, but are also limited. They cover acute events, but are affected 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 the changing drug use environment, such as the current problems of polysubstance use and drug counterfeiting.
An increase in emergency department visits may reflect an increase in drug use, but it may also reflect changes in EMT or diagnostic practices or health care referrals.
Problems with surveys became apparent early in the opioid crisis. As overdoses and deaths from illicitly produced fentanyl have risen rapidly, survey-based estimates have continued to show relatively stable opioid use. The discrepancy between reported prevalence and observed mortality indicated that surveillance systems were unable to capture events in real time.
In contrast, WBE with daily or weekly sampling allows rapid detection changes in forms of drug use. It covers broad populations, including individuals not represented in surveys or clinical databases. This allows for fine-grained geographic analysis to detect localized trends and micro-epidemics (small, area-specific drug outbreaks).
Today’s drug landscape, which often begins in clubs and events, is defined by synthetic compounds and an ever-changing supply of counterfeit drugs. Research by NYU professor Joey Palamar supports a shift from relying on self-reports to implementing objective measures of drug effects. Surface sampling of drugs in nightlife settings by analyzing swabs from tables, cell phones, and other environmental surfaces can also provide information on drug trends and effects in real time.
New data have been revealed with wastewater-based epidemiology in Europe and the United States
European data provided the most comprehensive examples of WBE. Longitudinal monitoring from 2011 to 2025 showed a geographic pattern, with cocaine use accelerating, concentrated in Western and Southern Europe, and amphetamines more prevalent in the North. Europe is better for consistency of WBE surveillance and international trends and epidemiology. The US is better at spotting localized patterns, micro-epidemics and rapid changes in drug markets.
The most recent WBE findings in the United States (2024–2025) highlighted a changing addiction landscape. Cocaine residues increased by about 22 percent and ketamine by 41 percent, while MDMA (Ecstasy or “E”) decreased by about 16 percent. Cannabis has remained relatively stable, but variation across cities has persisted. Ketamine has expanded rapidly in the recreational drug landscape, especially along with the high use of cocaine. The wastewater data also showed a weekend drug peak associated with nightlife.
Effluent monitoring can also function as a public health early warning system. In Nantucket, Massachusetts, wastewater analyzes revealed cocaine concentrations three times the national average. These levels also showed strong seasonal variations related to tourism. Wastewater data revealed the use of new synthetic opioids in addition to fentanyl. Fentanyl exposure is stabilizing or decreasing, while other synthetic opioids are increasing. US data showed that patterns of drug use vary 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, identifying opioid trends, counterfeiting, and emerging synthetic drugs (nitazenes, xylazine compounds).
Instead of testing people, cities collect a small amount of wastewater from a treatment plant over the course of a day and test a mixed sample of thousands of people to give an indication of local drug use. Long-term wastewater monitoring in Tempe, Arizona, showed that opioid exposure was not concentrated in specific “hot spots” but rather spread throughout the city.
Environmental surface sampling and exposure to multiple substances
Complementing wastewater analysis, environmental sampling—especially in clubs or nightlife—provides insight into the effects of drugs in specific environments. Recent studies show that surface analysis shows the popularity of substances such as cocaine and ketamine in this environment.
Important analytical studies by Palamar have shown the discrepancy between drug acceptance and actual use. Individuals who believe they have taken one substance (such as MDMA-ecstasy) have actually been found to have taken completely different compounds. Perhaps most importantly, it showed that fentanyl is increasingly being detected among individuals who refuse to use opioids.
Emerging approaches—including wastewater-based epidemiology, environmental sampling, and real-time EMT, or toxicological monitoring—have shifted monitoring upstream. They serve as leading indicators of drug use epidemiology, exposure, and delivery patterns, allowing for more targeted public health interventions.
