An exploratory study toward the contribution of 3D surface scanning for association of an injury with its causing instrument.

3D surface scanning is a technique brought forward for wound documentation and analysis in order to identify injury-causing tools in legal medicine and forensic science. Although many case reports have been published, little is known about the methodology employed by the authors. The study reported here is exploratory in nature, and its main purpose was to get a first evaluation of the ability of an operator, by means of 3D surface scanning and following a simple methodology, to correctly exclude or associate an incriminated tool as the source of a mock wound. Based on these results, an assessment of the possibility to define a structured methodology that could be suitable for this use was proposed. Blunt tools were used to produce 'wounds' on watermelons. Both wounds and tools were scanned with a non-contact optical surface 3D digitising system. Analysis of the obtained 3D models of wounds and tools was undertaken separately. This analytical phase was followed by a qualitative and a quantitative comparison. Results showed that in more than half of the cases, we obtained a correct association but the prevalence of wrong association was still high due to mark deformation and other limitations. Even if the findings of this exploratory study cannot be generalised, they suggest that the simple and direct comparison process is not reliable enough for a systematic routine application. The article highlights the importance of an analysis phase preceding the comparison step. Limitations of the technique, ensuring needs and possible paths for improvement are also expounded.

Mining the Chemical Information on Urban Wastewater: Monitoring Human Exposure to Phosphorus Flame Retardants and Plasticizers.

At the individual level, exposure to contaminants is generally assessed through the analysis of specific biomarkers in biological matrices. However, these studies are costly and logistically demanding, limiting their applicability to monitor population-wide exposure over time and space. By focusing on a selection of exposure biomarkers to phosphorus flame retardants and plasticizers (PFRs), this study aims to explore the possibility of using wastewater as a complementary source of information about exposure. Wastewater samples were collected from five cities in Europe and analyzed using a previously established method. Substantial differences in biomarker levels were observed between the investigated catchments, suggesting differences in exposure. Time trends in biomarkers observed between 2013 and 2016 were found to agree with results from human biomonitoring studies and reports about production volumes. Using Monte Carlo simulations, average urinary concentrations were estimated. These were generally higher compared to results from human biomonitoring studies. Various explanations for these differences were formulated (i.e., other excretion routes, external sources and different sampling approaches). Obtained results show that wastewater analysis provides unique information about geographical and temporal differences in exposure, which would be difficult to gather using other monitoring tools.

Study of acidified ignitable liquid residues in fire debris by solid-phase microextraction with gas chromatography and mass spectrometry.

The detection and identification of ignitable liquid residues in fire debris can be meaningful in fire investigations. However, background pyrolysis products and weathering hinder the identification and classification steps. In addition to those processes, the acidification of the ignitable liquids before the combustion process could make those tasks even more difficult. Nevertheless, there are no systematic studies assessing the extraction, analysis, and composition of acidified ignitable liquid residues obtained from fire debris. In this work, a method for the study of acidified ignitable liquid residues in fire debris by solid-phase microextraction with gas chromatography and mass spectrometry is proposed. This methodology has been evaluated, first with simulated solutions (gasoline/sulfuric acid mixtures set on fire under controlled conditions), and then with analysis of samples from real fire debris obtained from 18 chemical ignition Molotov cocktails made with sulfuric acid and three different ignitable liquids (two types of gasoline and diesel fuel). In addition, the extensive modifications observed in chromatograms of acidified ignitable liquid residues regarding neat and weathered samples were studied. These alterations were produced by the combustion and acidification processes. As a consequence, tert-butylated compounds are proposed as diagnostic indicators for the identification of acidified gasoline in fire debris, even in strongly weathered samples.

Population normalization with ammonium in wastewater-based epidemiology: application to illicit drug monitoring.

Fluctuations in ammonium (NH4+), measured as NH4-N loads using an ion-selective electrode installed at the inlet of a sewage treatment plant, showed a distinctive pattern which was associated to weekly (i.e., commuters) and seasonal (i.e., holidays) fluctuations of the population. Moreover, population size estimates based on NH4-N loads were lower compared to census data. Diurnal profiles of benzoylecgonine (BE) and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH) were shown to be strongly correlated to NH4-N. Characteristic patterns, which reflect the prolonged nocturnal activity of people during the weekend, could be observed for BE, cocaine, and a major metabolite of MDMA (i.e., 4-hydroxy-3-methoxymethamphetamine). Additional 24 h composite samples were collected between February and September 2013. Per-capita loads (i.e., grams per day per 1000 inhabitants) were computed using census data and NH4-N measurements. Normalization with NH4-N did not modify the overall pattern, suggesting that the magnitude of fluctuations in the size of the population is negligible compared to those of illicit drug loads. Results show that fluctuations in the size of the population over longer periods of time or during major events can be monitored using NH4-N loads: either using raw NH4-N loads or population size estimates based on NH4-N loads, if information about site-specific NH4-N population equivalents is available.

A forensic science perspective on the role of images in crime investigation and reconstruction.

This article presents a global vision of images in forensic science. The proliferation of perspectives on the use of images throughout criminal investigations and the increasing demand for research on this topic seem to demand a forensic science-based analysis. In this study, the definitions of and concepts related to material traces are revisited and applied to images, and a structured approach is used to persuade the scientific community to extend and improve the use of images as traces in criminal investigations. Current research efforts focus on technical issues and evidence assessment. This article provides a sound foundation for rationalising and explaining the processes involved in the production of clues from trace images. For example, the mechanisms through which these visual traces become clues of presence or action are described. An extensive literature review of forensic image analysis emphasises the existing guidelines and knowledge available for answering investigative questions (who, what, where, when and how). However, complementary developments are still necessary to demystify many aspects of image analysis in forensic science, including how to review and select images or use them to reconstruct an event or assist intelligence efforts. The hypothetico-deductive reasoning pathway used to discover unknown elements of an event or crime can also help scientists understand the underlying processes involved in their decision making. An analysis of a single image in an investigative or probative context is used to demonstrate the highly informative potential of images as traces and/or clues. Research efforts should be directed toward formalising the extraction and combination of clues from images. An appropriate methodology is key to expanding the use of images in forensic science.

Forensic exploitation of patterned injuries: Promoting structured analysis as an early assessment for comparison process.

Practice at our Center shows that approach using 3D surface imaging for morphometric comparison of patterned injuries does not always lead to accurate conclusions. We decided to evaluate whether a selection protocol focused on analysis phase could enable us to form an early assessment of the outcome of a comparison process, and then to select lesions likely to lead to a probative conclusion. 23 blunt objects were used to create 65 patterned injuries on an experimental model simulating human skin. A blinded analysis and a comparison were conducted on photographs and 3D models of the lesions. Statement of analysis phase was consistent with comparison results in most cases, enabling correct identification of the responsible object or at least keeping it as possibly responsible among 2 to 3 objects. Our protocol has been demonstrated to improve ability to exploit patterned injuries from surface imaging, despite certain limiting factors.

The emergence of 3D-printed firearms: An analysis of media and law enforcement reports.

3D-printed firearms, an emerging category of privately made firearms (PMF) produced beyond government control, have become increasingly prevalent due to technological advancements. They are now emerging as a cost-effective and reliable alternative to conventional firearms. Raised to public awareness following the 2013 release of the 3D-printed Liberator, these firearms are now more commonly encountered by police forces. This article analyses various reports involving 3D-printed firearms, reflecting the increasing encounters by law enforcement agencies. It examines 186 cases involving 3D-printed firearms, primarily from North America, Europe, and Oceania, highlighting a significant rise in incidents since 2021. These incidents include seizures, illicit uses, and online sales, with the firearms typically being hybrid models, Parts Kit Completions/Conversions (PKC), or firearm components such as auto sears. The study underscores the use of affordable equipment and materials for production, emphasizing the accessibility and potential risks of these firearms.

δ15N measurement of organic and inorganic substances by EA-IRMS: a speciation-dependent procedure.

Little attention has been paid so far to the influence of the chemical nature of the substance when measuring δ(15)N by elemental analysis (EA)-isotope ratio mass spectrometry (IRMS). Although the bulk nitrogen isotope analysis of organic material is not to be questioned, literature from different disciplines using IRMS provides hints that the quantitative conversion of nitrate into nitrogen presents difficulties. We observed abnormal series of δ(15)N values of laboratory standards and nitrates. These unexpected results were shown to be related to the tailing of the nitrogen peak of nitrate-containing compounds. A series of experiments were set up to investigate the cause of this phenomenon, using ammonium nitrate (NH(4)NO(3)) and potassium nitrate (KNO(3)) samples, two organic laboratory standards as well as the international secondary reference materials IAEA-N1, IAEA-N2-two ammonium sulphates [(NH(4))(2)SO(4)]-and IAEA-NO-3, a potassium nitrate. In experiment 1, we used graphite and vanadium pentoxide (V(2)O(5)) as additives to observe if they could enhance the decomposition (combustion) of nitrates. In experiment 2, we tested another elemental analyser configuration including an additional section of reduced copper in order to see whether or not the tailing could originate from an incomplete reduction process. Finally, we modified several parameters of the method and observed their influence on the peak shape, δ(15)N value and nitrogen content in weight percent of nitrogen of the target substances. We found the best results using mere thermal decomposition in helium, under exclusion of any oxygen. We show that the analytical procedure used for organic samples should not be used for nitrates because of their different chemical nature. We present the best performance given one set of sample introduction parameters for the analysis of nitrates, as well as for the ammonium sulphate IAEA-N1 and IAEA-N2 reference materials. We discuss these results considering the thermochemistry of the substances and the analytical technique itself. The results emphasise the difference in chemical nature of inorganic and organic samples, which necessarily involves distinct thermochemistry when analysed by EA-IRMS. Therefore, they should not be processed using the same analytical procedure. This clearly impacts on the way international secondary reference materials should be used for the calibration of organic laboratory standards.

Ok Google, Start a Fire. IoT devices as witnesses and actors in fire investigations.

Fire incidents are amongst the most destructive events an investigator might encounter, completely transforming a scene with most of the objects left in ashes or highly damaged. Until now, fire investigations relied heavily on burn patterns and electrical artifacts to find possible starting locations, as well as witness statements and more recently witness imagery. As Internet of Things (IoT) devices, often seen as connected smart devices, become more common, the various sensors embedded within them provide a novel source of traces about the environment and events within. They collect and store information in different locations, often not touched by the event, such as remote servers (cloud) or companion smartphones, widening the investigation field for fire incidents. This work presents two controlled fire incidents in apartments that we furnished, equipped with IoT devices, and subsequently burnt. We studied the traces retrievable from the objects themselves after the incident, the companion smartphone apps, and the cloud and assessed the value of the information they conveyed. This research highlighted the pertinence to consider traces from IoT devices in the forensic process of fire investigation.

Was a 3D-printed firearm discharged? Study of traces produced by the use of six fully 3D-printed firearms.

Since the blueprints of the Liberator were published and successfully tested, countless new designs for said 3D-printed firearms and 3D-printed firearm components have been created and made publicly available. These new 3D-printed firearms, which are praised by their designers as ever more reliable, can be found on the Internet with little effort. Press reports have shown that various models of 3D-printed firearms have already been confiscated by law enforcement services around the world. So far, forensic studies have addressed this set of problems relatively little, whereby for the most part only the Liberator has been examined in detail and three other designs were only included a few times. The rapid pace of this development poses new challenges for forensic investigations and unveil new spheres of investigation regarding 3D-printed firearms. This research initiative aims to determine whether the results from previous studies on Liberators, are also reproducible and observable when using other models of 3D-printed firearms. In this respect six fully 3D-printed firearms - PM422 Songbird, PM522 Washbear, TREVOR, TESSA, Marvel Revolver and Grizzly - were produced on a material extrusion type Prusa i3 MK3S using PLA as the material. Test firings of these 3D-printed firearms have shown that they are indeed functional, but that, depending on the model, they suffer different levels of damage when fired. However, they were all rendered inoperative after one discharge and could not be used for further discharges unless the broken pieces were replaced. As in other studies, the firing process and the resulting ruptures on the 3D-printed firearm, projected polymer parts and fragments of different sizes and in different quantities into the immediate environment. The parts could be physically matched, allowing the reconstruction and identification of the 3D-printed firearms. Elements of ammunition also showed traces of melted polymer on the surface and cartridge cases bore tears or swellings.

Investigating the availability of 3D-printed firearm designs on the clear web.

The release of the plans of the 3D-printed Liberator firearm sparked a wave of new designs from creators worldwide, resulting in an extensive collection of 3D-printed firearm plans, in particular blueprints, and parts available for almost unrestricted download on the internet. Identifying and categorizing the diverse range of 3D-printed firearms and components pose a challenge due to the abundance of designs available. Between 2021 and April 2023, data was collected on over 2,100 3D-printed firearm plans. While blueprints of fully 3D-printed firearms initially dominated the scene, hybrid designs and parts kit completions / conversions (PKC) have gained popularity for their improved reliability and performance. The now highly networked community offers considerable support with detailed instructions and procedures, providing precise guidance for construction. This systematic classification, grouping and structuration of the recorded data on the Clear Web supported the identification of patterns of the main threat trends related to 3D-printed firearms.

Cleaning deteriorated elements of ammunition: Development of a procedure applied to cartridge cases from the Second World War.

Deteriorated elements of ammunition can be found while investigating different types of events. Exposure to adverse environmental conditions may lead to metal alteration (corrosion) or organic material deposition (contaminations) on the exposed elements of ammunition. From a forensic perspective, both types of deterioration pose challenges when observing marks left by the firearms used to discharge the corresponding ammunition (e.g. firing pin, extractor). The longer the time of exposure to the adverse environmental conditions, the more challenging the observation of such marks. A literature review highlighted three previously published restorative methods used to clean deteriorated elements of ammunition. The aim of this research is to develop a cleaning procedure applicable to cartridge cases exposed to adverse environmental conditions, while avoiding the degradation of marks left by the firearms used to discharge the corresponding ammunition. A first batch of 21 brass cartridge cases dating back to the Second World War (WWII) was used to develop a cleaning sequence involving the three methods. The efficiency of each restorative method was qualitatively assessed using optical macroscopy and the Evofinder® ballistic identification system. The developed sequence relies on successive applications of Tickopur® TR 7 (a diluted soft metal cleaner), sulfuric acid and finally Aqua Regia (HCl 37% and HNO3 75%), all of them involving ultrasonic baths. The resulting cleaning sequence was subsequently applied to three batches of Second World War cartridge cases discovered in France and Russia. This sequential procedure allows the effective cleaning of WWII brass cartridge cases while highlighting different marks left by firing pins, extractors, ejectors, and breech faces. Applying a forensic analysis and comparison process to the marks highlighted on these elements of ammunition can support the verification of historical facts when reconstructing events which took place more than seventy years ago.

The potential of digital technologies in problem-based forensic learning activities.

Forensic practice is the concluding practical course of the forensic science bachelor program at the School of Criminal Justice of the University of Lausanne. Learning activities are constructed around five main objectives for the resolution of simulated forensic case problems: 1) select relevant traces and items to be collected at the scene and perceive their potential value in the reconstruction process, 2) apply appropriate detection techniques in sequence to obtain clues of good quality, 3) process traces using Analysis, Comparison, Evaluation and Verification (ACE-V) methodology, 4) produce and summarise information in oral and written forms to help an investigation, and 5) work collaboratively to benefit from the diversity of group members. Simulating and supervising realistic activities is a complex task that became more and more challenging with a continuously increasing number of students over the years (from ca. 30 in 2016 to more than 60 in 2021). Thus, an educational innovation project was launched and aimed at implementing digital technologies to support the teaching staff. A computer-based crime scene simulation tool (allowing students to visualize 360° crime scenes and relevant items) and a communication tool (to simplify and centralise the communication between the students and the teaching staff) were implemented. This article describes the implementation, added value and limitations of these digital technologies in problem-based learning activities. Prior to 2020, the practical course forensic practice was delivered entirely on-site without specific technologies, and entirely on-line in 2020 (due to the sanitary restrictions related to the COVID-19 pandemic). Finally, in 2021, on-line and on-site activities were implemented with success, combining the best of both approaches in a blended teaching mode. An overall increase in the satisfaction of students and teaching staff was observed with the implementation of these tools. Limiting presence on-site allowed students to take a step back from the activities and collected items. This promoted critical thinking, and together with an increase in structured (on-line and on-site) interactions allowed for a positive, continuous learning experience. While the evaluations of these novel technologies were very positive, students still expressed their willingness to perform certain tasks on-site and a preference for face-to-face interactions.

Effects of chemical warfare agent decontaminants on trace survival: Impact on fingermarks deposited on glass.

Following a chemical incident involving chemical warfare agents or more broadly, chemical weapons, there are two possible approaches in dealing with the traditional forensic analysis of contaminated exhibits. The first is to analyze the contaminated items under safe conditions (i.e. in laboratories dedicated to the handling of such substances), while the second relies on item decontamination prior to processing them in traditional forensic laboratories. One of the main limitations of the latter is the possible degradation or destruction of traces caused by the decontamination process. Hence, it is crucial to have as much information as possible on the impact of different decontamination agents and procedures on traces. This research presents experimental results on the recovery of fingermarks on glass after the application of decontaminants typically used in case of chemical incidents. The impact of 11 decontaminants on fingermarks deposited on glass and on the subsequent enhancement with cyanoacrylate and Small Particle Reagent (SPR) was evaluated (by visual examination) by four evaluators. The results of the study demonstrated that the persistence of fingermarks on glass is highly dependent on the type of decontaminant used. Decontamination agents based on the principle of nucleophilic substitution to neutralize toxic chemicals allowed good subsequent development of fingermarks with SPR. Powdered decontaminants did not show any indication of alteration of fingermarks, whereas decontamination with oxidants leads to variable results.

Influence of the printing process on the traces produced by the discharge of 3D-printed Liberators.

Since its introduction in 1986, 3D printing technology is in constant development. 3D printers are becoming more and more performant and accessible. In 2013, the Liberator blueprints are released online. This single-shot pistol can be entirely manufactured using a 3D printer, except for the firing pin and the ammunition. First, this research aims at establishing an overview of all the elements and traces potentially present when a 3D-printed firearm is involved, whether it is fired or not. In the second part, we study these elements for exploitability to obtain information about the manufacture of the firearm (printing processes, 3D printers and polymers). For this purpose, a total of 36 Liberators were manufactured using different printing conditions (i.e., printing processes, printers, polymers and parameters). The tested printing processes were based on the principles of Material Extrusion (ME), Vat Photopolymerization (VP) and Powder Bed Fusion (PBF). All 3D-printed firearms manufactured via ME and PBF were able to fire whereas Liberators manufactured by VP printing could not be fired. This could be explained by the lack of precision of the prints making it impossible to assemble some of the Liberators, or by the fact that the polymer was not suitable to produce the springs. All the barrels were broken by the discharge, projecting polymer pieces or fragments into the environment. These polymer pieces or fragments were examined to determine which printing process was used as well as other elements related to printing parameters and conditions (e.g., layer height, filling pattern and infill density). This information is useful to determine whether a certain command file, slicer or 3D printer could be at the source of a questioned 3D-printed firearm. Melted polymer or polymer particles on elements of ammunition may also be present after the firing process. However, the examination of these particles does not allow inferring other information, except the possible use of a 3D-printed polymer firearm.

Detection of gasoline on suspects' hands: Study of different sampling alternatives.

Arsonists may use ignitable liquids to start, accelerate and amplify fires. The sampling of volatiles present on the hands of suspected arsonists is therefore sometimes carried out in the course of the investigation of (possible) deliberate fires. Several collection protocols have been proposed, relying on the concentration of volatiles by the transfer on PVC gloves and further passive headspace extraction with Activated Charcoal Strips (ACS). Previous research findings assessing the use of Activated Carbon Cloth (ACC) - initially developed for the adsorption of gas in military applications - opens the path to new perspectives regarding the extraction and the concentration of ignitable liquid residues in general, and for the sampling on hands in particular. Five alternative methods (four relying on the use of ACC and one on ACS) were considered for the collection of gasoline traces present on the hands and their subsequent analysis by gas chromatography - mass spectrometry. Gasoline was deposited onto the palms of volunteers to study the differences between the collection method using ACS and those using ACC. For the latter, either the volunteer hands were placed in nylon bags with an ACC on the palm or suspended, or, powder-free latex gloves were used, with an ACC on the palm or in a separate extraction, with the glove in a nylon bag and the ACC suspended. The results showed that the background contamination was not distinguishable between ACS and ACC and their sampling ability was comparable. The two methods relying on the deposition of ACC directly on the surface of the palm where gasoline was deposited showed significantly higher collection capacity than other methods, provided that the ACC was in direct contact with the contaminated zone. The results showed that three main factors affected the collection of gasoline on the hands: the distance between the skin and the sorbent (ACC or ACS) in case of direct concentration of volatiles on the sorbent, the exposure time, and the space between the hand and the glove or bag (i.e. the headspace volume). This research opens new perspectives for the sampling of ignitable liquid residues through the use of ACC. It corroborates the perceived potential of ACC for the extraction and concentration of volatile compounds, particularly for fire debris analysis purposes. While the experiments were focused on the collection of gasoline on hands, the results provide valuable information in a more general way for the sampling of fire debris.

Use of ion mobility-high resolution mass spectrometry in metabolomics studies to provide near MS/MS quality data in a single injection.

The use of ion mobility separations (IMSs) in metabolomics approaches has started to be deeply explored in the last years. In this work, the use of liquid chromatography (LC) coupled to IMS-quadrupole time-of-flight mass spectrometry (QTOF MS) has been evaluated in a metabolomics experiments using single injection of the samples. IMS has allowed obtaining cleaner fragmentation spectra, of nearly tandem MS quality, in data-independent acquisition mode. This is much useful in this research area as a second injection, generally applied in LC-QTOF MS workflows to obtain tandem mass spectra, is not necessary, saving time and evading possible compound degradation. As a case study, the smoke produced after combustion of herbal blends used to spray synthetic cannabinoids has been selected as study matrix. The smoke components were trapped in carbon cartridges, desorbed and analyzed by LC-IMS-QTOF MS using different separation mechanisms (reversed phase and HILIC) and acquiring in both positive and negative mode to widen the chemical domain. Partial Least Squares-Discriminant Analysis highlighted several compounds, and ratio between N-Isopropyl-3-(isoquinolinyl)-2-propen-1-amine and quinoline allowed differentiating between tobacco and herbal products. These two compounds were tentatively identified using the cleaner fragmentation spectra from a single injection in the IMS-QTOF MS, with additional confidence obtained by retention time (Rt) and collisional cross section (CCS) prediction using artificial neural networks. Data from this work show that LC-IMS-QTOF is an efficient technique in untargeted metabolomics, avoiding re-injection of the samples for elucidation purposes. In addition, the prediction models for Rt and CCS resulted of help in the elucidation process of potential biomarkers.

How to share and utilise expertise in a police forensic department through externalisation and mutualisation.

The technique of fire investigation is a forensic domain in which expertise and analogies play a central role. To learn how fire investigators use these analogies to support their work, we conducted an ethnographic study in a Swiss forensic police department. To propose a suitable knowledge-management strategy, we also evaluated the knowledge conservation and sharing within the department. Our results highlighted that actionable knowledge is registered mainly in the investigators' memories of a few, very experienced, individuals. Without experience with fire-incident investigations, an agent generally requires help from a more experienced colleague, who will then use his memory to find a similar case, which can contribute to the solution of the ongoing one. The research also established that knowledge is exchanged orally during on-site investigations and that knowledge receivers are generally those who are present on the scene. Using these findings, we suggest building a case library to support the externalisation and sharing of knowledge.

Testing wastewater from a music festival in Switzerland to assess illicit drug use.

This article describes the application of a recently proposed framework for deploying wastewater-based epidemiology (WBE) to monitor illicit drug use within festivals (Benaglia et al., 2019). The festival under study was a week-long music festival in Switzerland (Swiss Festival) which attracted around 50,000 people daily. Wastewater sampling was performed during its 2014 and 2015 editions. As the Swiss Festival's wastewater is conveyed to the sewage treatment plant (STP) of the nearby city, to assess illicit drug use when there is no festival (i.e. the background consumption) wastewater sampling was also carried out during an off-festival week in 2015. During the 2014 and 2015 editions of the Swiss Festival, WBE highlighted that the most consumed illicit drugs were cannabis, MDMA, cocaine and amphetamine. Excluding cannabis, the means per capita loads of all illicit drugs were not statistically different between both editions of the Swiss Festival. The results were then compared to those of an Australian festival which had also been subject of a quantitatively assessed illicit drug use study (Lai et al., 2013). This comparison confirmed that MDMA is highly prevalent, as well as amphetamine, although to a lesser extent. Consumption of cocaine (in Switzerland) and methamphetamine (in Australia) is also high, but their use seems to be related to their availability (i.e. to the country where the festival takes place). Furthermore, it was observed that MDMA and amphetamine are more consumed during the festival compared to normal times, when there is no festival. This might suggest that their availability is increased and therefore, that a market for these substances potentially exists during the festival. This last hypothesis was assessed by consulting drug seizures made by the police during the 2015 Swiss Festival. Despite very limited data, police records suggested that most of the drugs were purchased at the festival, which supports the previous hypothesis. Results validate, on the one hand, WBE as a useful indicator to monitor illicit drug use within festivals and on the other hand, the suggested framework for deploying WBE in such environment. In addition, this study suggests the need for prevention and harm reduction measures targeted on MDMA and amphetamine during the Swiss Festival, such as drug checking laboratories.

Spatio-temporal assessment of illicit drug use at large scale: evidence from 7 years of international wastewater monitoring.

BACKGROUND AND AIMS: Wastewater-based epidemiology is an additional indicator of drug use that is gaining reliability to complement the current established panel of indicators. The aims of this study were to: (i) assess spatial and temporal trends of population-normalized mass loads of benzoylecgonine, amphetamine, methamphetamine and 3,4-methylenedioxymethamphetamine (MDMA) in raw wastewater over 7 years (2011-17); (ii) address overall drug use by estimating the average number of combined doses consumed per day in each city; and (iii) compare these with existing prevalence and seizure data. DESIGN: Analysis of daily raw wastewater composite samples collected over 1 week per year from 2011 to 2017. SETTING AND PARTICIPANTS: Catchment areas of 143 wastewater treatment plants in 120 cities in 37 countries. MEASUREMENTS: Parent substances (amphetamine, methamphetamine and MDMA) and the metabolites of cocaine (benzoylecgonine) and of Δ9 -tetrahydrocannabinol (11-nor-9-carboxy-Δ9 -tetrahydrocannabinol) were measured in wastewater using liquid chromatography-tandem mass spectrometry. Daily mass loads (mg/day) were normalized to catchment population (mg/1000 people/day) and converted to the number of combined doses consumed per day. Spatial differences were assessed world-wide, and temporal trends were discerned at European level by comparing 2011-13 drug loads versus 2014-17 loads. FINDINGS: Benzoylecgonine was the stimulant metabolite detected at higher loads in southern and western Europe, and amphetamine, MDMA and methamphetamine in East and North-Central Europe. In other continents, methamphetamine showed the highest levels in the United States and Australia and benzoylecgonine in South America. During the reporting period, benzoylecgonine loads increased in general across Europe, amphetamine and methamphetamine levels fluctuated and MDMA underwent an intermittent upsurge. CONCLUSIONS: The analysis of wastewater to quantify drug loads provides near real-time drug use estimates that globally correspond to prevalence and seizure data.