Investigating illicit drugs in PM10 from Northern Italy using a rapid HPLC-MS/MS method

Illicit drugs (IDs) are substances whose production, consumption, and health impact are increasing globally. While their presence in water and soil has been studied, airborne concentrations remain largely unexplored. Airborne IDs could serve as markers of consumption patterns and potentially help identify local drug distribution zones. Few analytical methods have been developed, but preanalytical treatments are often time-consuming. To address this, we developed and validated a reliable, fast analytical method based on HPLC-MS/MS for cocaine, amphetamine, and heroin – three largely consumed IDs. Low Method Detection and Quantification Limits were achieved, with cocaine reaching the lowest reported in the literature (0.02 and 0.08 pg m -3 , respectively). Our methodology was applied to nearly 180 PM 10 samples collected during December 2023 across thirteen cities in northern Italy. Cocaine was always detected and quantified, whereas amphetamine and heroin were below the detection limit. The highest cocaine concentrations were recorded in Milan (229 pg m -3 ), Collegno (195 pg m -3 ), and Treviso (111 pg m -3 ). A notable increase in cocaine levels over the month suggests a link with holidays, tourism, and the Christmas Depression phenomenon. In some cities, concentration spikes coincided with traditional festivities. Statistical analyses were conducted to explore correlations between cocaine, PM 10 , inorganic major ions, and atmospheric variables. Negative correlation was found between cocaine concentration and wind in six cities, suggesting multiple local sources. Local available healthcare and drug seizure data were also considered, and an interesting correlation was found between cocaine levels and people taken into care by private services. • A reliable LC-ESI-MS/MS methodology was developed to analyze three illicit drugs in PM 10 • Cocaine was quantified in all 13 cities across Northern Italy • Cocaine increased during December, possibly due to holidays, tourism, and Christmas Depression • The highest concentration peak was observed in Milan during a traditional festivity • Correlation was trivial with PM 10 and inorganic major ions, but negative with wind