Qualitative fingerprinting of psychoactive pharmaceuticals, illicit drugs, and related human metabolites in wastewater: A year-long study from Riga, Latvia

Abstract

The COVID-19 pandemic has become an unprecedented public health emergency causing immense societal and socio-economic consequences. Multiple studies have outlined that interventions to curb the spread of the virus are likely to have an effect on substance use patterns. In this study, we explored the presence of psychoactive pharmaceuticals, illicit drugs and related human metabolites in 24-h composite wastewater samples that were collected weekly in 2021 from the central WWTP of Riga, Latvia. The analysis was performed via suspect screening approach using three separate high-resolution mass spectrometry (HRMS) workflows, which relied on reversed-phase liquid chromatography (RPLC), hydrophilic interaction liquid chromatography (HILIC) and direct infusion HRMS. In total, 39 out of 149 substances were detected throughout the sampling period. These include pharmaceuticals (mainly antiepileptics, antidepressants and antipsychotics), illicit drugs (e.g., MDMA, MDEA, cocaine, etc.) and new psychoactive substances (alpha-PVP). The results were evaluated in relation to COVID-19 incidence rate and the severity of containment and closure policies. For some compounds we observed temporal changes that may be potentially linked to the state of the pandemic. For instance, higher detection rates were observed for several illicit drugs during periods, when restrictions on public events were relaxed. Meanwhile, some psychoactive pharmaceuticals and drugs used to treat upper respiratory tract infections displayed increased prevalence in weeks when the national COVID-19 incidence rates were higher. However, without baseline reference data from previous years, it is difficult to discern how much of the relationships seen are linked to pandemic progression and seasonal variability.

Keywords: COVID-19; HILIC; High resolution mass spectrometry; Illicit drugs; Pharmaceuticals; Suspect screening.

Graphical abstract

Fig. 1

Scheme of the applied suspect screening workflow and confidence levels of identification (1, 2a, 2b and 3) using LC-HRMS and DI-HRMS approaches.

Fig. 2

RPLC-HRMS and HILIC-HRMS chromatograms, DI-HRMS full-scan data and corresponding MS² spectra for an antipsychotic drug sulpiride measured in wastewater. Diagnostic MS² fragments from the mzCloud library (ID: 3452) are at m/z 214.0169, m/z 112.1121, m/z 98.0964 and m/z 58.0651.

Fig. 3

Normalized peak areas of selected APIs that were identified during the study from December 22, 2020 till December 12, 2021. The dashed line represents the 14-day notification rate of newly reported COVID-19 cases per 1,00,000 population in Latvia. Pearson product-moment correlation is depicted at the left upper corner of each facet. Asterisks indicate statistical significance (*p < 0.05, **p < 0.01 and ***p < 0.001). The area highlighted in red indicates period from October 21 to November 14 when curfew was imposed as one of the confinement measures to curb the pandemic.

Fig. 4

Normalized peak areas of selected illicit drugs and NPS that were identified during the study from December 22, 2020 till December 14, 2021. The dashed line represents the stringency index used by the Oxford COVID-19 Government Response Tracker. The area highlighted in red indicates period from October 21 to November 14 when curfew was imposed as one of the confinement measures to curb the pandemic.