Assessing drug consumption patterns in Canadian cities through wastewater analysis

Monitoring drug consumption is crucial for public health systems to address ongoing crises and anticipate future surges. Considering that drug overdoses generally go unreported, wastewater-based epidemiology (WBE) can be an effective tool for assessing drug use. The presence of a drug metabolite in wastewater can predict parent drug use within a population. This study investigates the use of WBE to monitor drug consumption patterns in seven Canadian cities by focusing on the detection of drug residues (parent compounds and metabolites) in wastewater and analyzing the potential link between drugs categorized by Statistics Canada as prescribed and unprescribed and cocaine detection. A model and research hypotheses were developed based on extensive literature and theoretical reviews on prescribed and unprescribed drug consumption to affirm the nature of the hypotheses for the study. Our analysis used datasets from Statistics Canada (Drug metabolites in wastewater in select Canadian cities, by month. https://www150.statcan.gc.ca/t1/tbl1/en/tv.action?pid=1310082001/ , 2024), which categorized drugs into prescribed and unprescribed groups. These categories reflect regulatory and pharmacological status and do not allow us to distinguish between medically prescribed use, diverted prescription use, or illicit/recreational use at the individual level. The data collected were analyzed using structural equation modelling (SEM) and Artificial Neural Network (ANN) techniques to affirm the study hypotheses. The findings revealed a higher concentration of unprescribed drugs in the wastewater compared to prescribed drugs in six of the seven cities, with Prince Albert, Edmonton and Vancouver showing the highest detection. Halifax was the only city in which drugs categorized as prescribed had a higher total detection than those categorized as unprescribed. Within the three cities with the highest total detection, cocaine had the highest concentration (measured as mean concentration in mg/1000 people/day), followed by methamphetamine, amphetamine and ecstasy. Correlation analysis indicated significant positive associations between certain drugs, with the strongest observed between the prescribed drugs cannabis and morphine. Predictive modelling was performed to further examine the probability of detecting cocaine alongside drugs classified as prescribed. The probability of cocaine detection was found to be the highest when cannabis and methadone were detected separately in wastewater. The results demonstrate associations, rather than causality, between residues of selected prescribed-type and unprescribed-type drugs and cocaine residues in wastewater. WBE provides valuable population-level indicators of drug consumption patterns and co-detection trends that can inform public health and harm reduction strategies.