A 12-month wastewater study across England has shown how high-frequency chemical monitoring can track changes in illicit drug consumption across urban populations – including weekend patterns, spikes around public events, and a temporary fall in cocaine markers following a major drug seizure.
The study, published in Addiction, analyzed 1,746 24-hour composite influent wastewater samples collected from 15 wastewater treatment plants in 2022. Together, the catchments covered an estimated 21 percent of England’s population, with sites selected across northern and southern regions and ranging from around 100,000 to more than 1 million population equivalents.
Researchers at Imperial College London and collaborators monitored 20 target compounds, including parent drugs, metabolites, and common adulterants. Most samples were analyzed using rapid direct-injection liquid chromatography-tandem mass spectrometry (LC-MS/MS), while solid-phase extraction LC-MS/MS was used for 6-monoacetylmorphine, a heroin marker present at lower concentrations.
Eighteen of the 20 compounds were detected in at least one sample. Cocaine showed the highest average population-normalized daily load, followed by heroin, ketamine, amphetamine, MDMA, and methamphetamine. When the English data were compared with European wastewater surveillance results from the same period, cocaine and ketamine loads were significantly higher at the English sites; seven English catchments recorded higher mean ketamine loads than any other European site included in the comparison.
The temporal resolution of the study allowed the team to look beyond annual averages. Cocaine and MDMA markers showed clear weekend increases, typically peaking in samples associated with Sunday excretion, while heroin was steadier across the week. The team also observed outliers around bank holidays, the Queen’s Jubilee, the Eurovision Song Contest, and England’s World Cup matches, although the authors note that some event-linked increases may overlap with normal weekend recreational use.
One of the clearest changes was a fall in cocaine consumption markers in March 2022, coinciding with the seizure of 3.7 tonnes of cocaine hydrochloride at Southampton Docks. In sites with data for both February and March, cocaine markers fell by 14-74 percent before mostly returning to average levels in April.
Speaking before publication in a webinar for The Analytical Scientist, Leon Barron, Professor of analytical and environmental sciences at Imperial College London, emphasized the practical challenge behind such large-scale monitoring. “We can’t test everywhere all the time,” he said, noting that large programs require compromises in spatial and temporal coverage. He also highlighted the importance of sample logistics, preparation speed, instrumental selectivity, and data analysis in making surveillance scalable.
Barron said rapid direct-injection workflows had been central to the program, allowing hundreds of samples per instrument per week when combined with matrix-matched calibrations, quality controls, and blanks. He also described how year-long wastewater data could identify elevated drug-use signals around specific dates. “This is very important for authorities,” he said, “to then be able to see what the impact of a seizure would be quantitatively on consumption.”
To hear more from Leon Barron on scaling targeted and non-target screening workflows for environmental monitoring – including the analytical methods behind this wastewater surveillance work – check out our New Frontiers in Non-Target Screening: Roundtable Symposium, now available on demand.
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