Wastewater-based epidemiology combined with forensic toxicological information: trends in drug use and impact of law enforcement activities

Abstract

Wastewater-based epidemiology (WBE) has recently become one of the most rapidly evolving disciplines engaged in the measurement of population-level illicit drug use. Still, limited evidence has been presented how population-level WBE data correlates to forensic toxicological statistics and law enforcement activities. Objective was to study (1) how WBE methodology can efficiently give early-warning type of information on drug use and its trends, (2) how WBE findings compared to number of drivers under influence of drugs (DUID), and (3) how (exceptionally large) law enforcement operation affected actual drug use. Wastewater analysis: 24-h wastewater influent composite samples ( n = 190) were collected during 04/2013–03/2022 from Helsinki wastewater treatment plant (WWTP) serving approximately 860,000 inhabitants. Furthermore, several national sampling campaigns up to 28 WWTPs covering approximately 60% of all Finnish population (3.2 million out of 5.5 million) during 2012–2022 were performed. All samples were analysed by validated UHPLC-MS/MS. For comparison, traffic cases: Prevalence of different drugs was studied in all suspected DUID cases in Finland (from 2013 to 2021). All cases (whole blood) were systematically analysed by chromatographic mass spectrometric techniques. Law enforcement operation of illicit drugs: Information on Operation Greenlight (Trojan Shield), which was an exceptional operation in size together with Finnish and several international law enforcement authorities worldwide starting in February 2021 in Finland. Both wastewater analysis data and suspected DUID cases confirm the significant rise of amphetamine and cocaine use between 2013 to early 2021 in Finland. Based on WBE, amphetamine use peaked at record-high level from mid-2020 (after COVID-19 lockdown) to spring 2021 in the capital area of Finland. Mean amphetamine mass loads were 92 mg/1000 persons/day in 2013, 335 in 2020, 322 in H1/2021, 234 in H2/2021 and 162 in Q1/2022 at the wastewater of Helsinki WWTP. The use of amphetamine significantly decreased in 2021 after the start of Operation Greenlight, while for cocaine effects on population-level use were more temporary. The number of amphetamine positive DUID in Finland showed similar trend: 2064 cases in 2013 (45.9% of all suspected DUID cases), 7913 (65.8%) in 2020 and 6228 (63.6%) in 2021 for amphetamine. For cocaine, the similar figures in wastewater were 18 (2013), 119 (2020), 110 (H1/2021), 144 (H2/2021) and 141 mg/1000 persons/day (Q1/2022), respectively. The number of cocaine-related DUID increased from 81 (2013) to 501 (2021). Cocaine use is still highly concentrated in the capital area of Finland and there has been 6-8-fold increase in cocaine use at population-level during the last eight years. Based on WBE, the use of amphetamine was partially replaced by methamphetamine and synthetic cathinones, such as alfa-PHP, at the end of 2021, but not close to the same extent as amphetamine use was reduced. The results show in detail how use of various illicit drugs has changed during the last decade in Finland. WBE and DUID results have strongly correlated with each other concerning drug use and its trends: increase/decrease in population-level drug use has also increased/decreased harmful societal phenomena of illicit drugs, such as DUID. The results obtained during the last year indicate that unexceptionally large and successful law enforcement operations may affect drug supply, reduce actual drug use and diminish harmful societal effects, such as DUID. Extensive 10-year data and experience on WBE approach shows that objective, novel and early-warning type of information on drug use and its trends for various illicit drugs can be obtained. More comprehensive picture and unique perspectives on drug use and drug markets are further obtained when combining different indicators and information, as exemplified here with WBE and DUID data linked to law enforcement activities.