Resumen de Drugs of abuse in the aquatic and atmospheric compartments: analysis, occurrence, and assessment of human cosumption in Spain
In the last decades, the development of increasingly sensitive analytical techniques has revealed the presence in the environment of a large number of potentially dangerous compounds for human health and the environment, globally referred to as "emerging pollutants". Due to its recent discovery or recognition as environmental contaminants, the knowledge about its presence, toxicity, and behavior in the environment is still very scarce.
Drugs of abuse and their metabolites are a class of organic substances that can be included within this category of emerging pollutants. Their high production and consumption results in a continuous inflow of these compounds and/or their metabolites into the environment, which gives them a "pseudo-persistent" character. However, the investigation of the presence of DAs in the environment is very recent.
The study of drugs in the environment has a double objective:
- to determine their presence in the different environmental compartments in order to assess their potential negative effects on ecosystems and humans and, - to estimate the consumption of drugs from the levels of the drugs themselves or their metabolites measured in the raw wastewater entering wastewater treatment plants (WWTPs) by applying the so-called "sewage epidemiology approach".
In this context, the main objectives of the work carried out in this thesis were to develop and apply different analytical methodologies to the determination of the most common drugs of abuse and their metabolites (including ethyl sulfate as a human metabolite of alcohol (ethanol), in different environmental samples, such as wastewater, surface water, sewage sludge and airborne particulate matter in order to better understand their environmental distribution and fate and to estimate drugs of abuse and alcohol consumption in different areas, with focus on the city of Barcelona.
Taking into consideration that most of the methods published for analysis of drugs of abuse focused on the dissolved phase, at the beginning of the research work a sensitive and reliable analytical method based on pressurized liquid extraction (PLE) followed by solid phase extraction (SPE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for the analysis of drugs of abuse in sewage sludge. This study provided the first insights into the fate of a wide number of drugs of abuse during wastewater treatments processes and also provided important information related to the environmental distribution of the most lipophilic compounds.
Two different analytical methodologies were then employed to study the occurrence and fate of drugs of abuse in surface water, wastewater and sewage sludge samples collected from 4 Spanish River basins in two consecutive sampling campaigns (2010 and 2011) in the frame of the CONSOLIDER-INGENIO 2010 “SCARCE” project. The main objective of this study was to provide a snapshot of the presence of the most abused illicit drugs in the Spanish environment and to study spatial and temporal differences in their distribution in the studied river basins under different climate conditions.
Concerning the sewage epidemiology approach used for estimation of drugs of abuse consumption, a five-year monitoring campaign was performed in order to study drugs consumption and temporal variations in the city of Barcelona. This study was performed in the framework of an international collaboration that aims to estimate and compare drugs of abuse consumption in different cities worldwide, to validate through annual inter-laboratory exercises the analytical methods employed for the analysis of these compounds in raw wastewater by the different laboratories, and to refine the entire methodology applied to the estimation of drug consumption based on levels of drugs residues in wastewater.
In the same context, an analytical method was developed and validated for the determination of alcohol consumption through the monitoring of a urinary biomarker, ethyl sulfate, in raw wastewater. This represented one of the first studies of this kind published worldwide in the scientific literature.
Finally, an extensive sampling campaign was carried out in the city of Barcelona to study the presence and distribution of drugs of abuse in airborne particulate samples collected throughout the entire city, in order to provide a better understanding of their environmental fate and distribution in this matrix and to evaluate whether the detection of illicit drugs in airborne particles may represent a new tool to investigate the social incidence of illicit drugs.
The main findings and conclusions of these works are itemized below.
The analytical method developed for the trace analysis of the most abused drugs and their metabolites in sewage sludge, based on PLE-LC-MS/MS, allows their reliable and accurate determination at levels below 3.3 ng/g d.w. for most of the investigated compounds. The optimization of the different aspects related to sample extraction and clean-up did not allow avoiding the matrix effects usually observed in this complex matrix, but the use of deuterium labeled compounds for the quantification of the majority of the analytes permitted to overcome the associated problems. This work investigated for the first time the presence and levels of THC, CBN, CBD, CE, EPH, HER, ALP, LSD and OH-LSD in this matrix.
Application of this methodology to the determination of DAs in 15 sewage sludge samples collected from different WWTPs located in Spain showed that: sorption onto sewage sludge represents the main route of removal of the most lipophilic drugs (e.g. cannabinoids and synthetic opioids) from wastewater, METH, EDDP and THC (present in all samples) were the most ubiquitous compounds followed by COC, EPH and CBD (present in at least 80% of the samples), while HER, 6ACM, LSD, and its metabolite OH-LSD were not detected, cannabinoids and the synthetic opioids (METH and EDDP) were also the most abundant compounds, with median concentrations ranging between 78-168 and 16-46 ng/g d.w, respectively; other compounds were detected with median concentrations lower than 6.6 ng/g d.w.
Analysis of EtS in wastewater samples, as a bio-indicator of alcohol consumption, at trace levels (LOD 0.02 µg/L and LOQ 0.07 µg/L, RSD 2.2 %) is possible with a simple developed method, based on addition of the surrogate standard, sample centrifugation, and subsequent direct analysis of the supernatant by ion pair-LC-MS/MS.
Application of this methodology to the analysis of 7 composite samples collected daily during one week at the inlet of a WWTP from Barcelona showed: a daily consumption of pure alcohol of 11000 to 25000 Kg/day in the studied area, which represents an averaged alcohol consumption of 18 mL/day/inhabitant, in agreement with similar studies performed in other countries, alcohol consumption values, estimated with the sewage epidemiology approach, lower than those published in the official reports (32 mL/day/inhabitant for Spain in the period 2003/2005, according to the WHO), concentrations of EtS, thus alcohol consumption, higher during the weekend than on weekdays.
The extensive monitoring performed to investigate the occurrence of DAs in surface water in Iberian rivers showed: comparatively higher levels of DAs in small rivers receiving WWTPs effluents than in the main course of the river, that COC, BE, EPH, MDMA, METH and EDDP were the most ubiquitous compounds, and BE and EPH the most abundant ones (with concentrations up to 144 ng/L), no direct links between the rivers flow and the levels of DAs, indicating that other attenuation mechanisms play significant roles in the environment, consistent, statistical significant differences in the presence of DAs between basins only in the case of MDMA, which suggests differentiated geographical consumption of this ATS in the studied area, a certain risk for aquatic organisms due to the presence of DAs in 4 out of the 144 river waters samples analyzed, being EDDP, METH, LOR, and MDMA the most concerning compounds.
The 5-year monitoring of DAs and alcohol in 24-h composite wastewater samples collected daily during one week in the middle of March from the inlet of a WWTP giving service to Barcelona city and its metropolitan area, showed that:
the most abused substance in Barcelona in the studied period was alcohol, followed by cannabis, cocaine, and ephedrine, in agreement with the last Drug Report of the Spanish Observatory of Drugs and Drug Addiction (OEDT), overall consumption of DAs increased in the studied period, from an average annual load of 6.5 kg/day in 2011 to 12 kg/day in 2015 (85% increase), this upward trend was mainly related to a higher consumption of cannabis, since consumption of other drugs increased to a lower extent (by 26%) and consumption of alcohol and heroin either decreased or remained stable, the optimized analytical method developed and applied to the analysis of DAs in the above wastewater samples is accurate, robust and reliable, at least for the compounds BE, AM, MA, MDMA, 6ACM and THC-COOH tested in the inter-laboratory exercises annually organized within the “SCORE” European COST Action.
The extensive monitoring of the presence of DAs in airborne matter collected in eleven different districts of the city of Barcelona in order to study presence and levels of DAs in airborne matter and to assess if levels found in this matrix can provide further information on drugs consumption in the investigated area showed that:
the most ubiquitous compounds were COC, its TP BE, MA, and CBN, detected in more than 76% of the analyzed samples; CE, DIA, LSD, OH-LSD, MOR, OH-THC, and THC-COOH were not detected; and the remaining compounds were present in less than 39% of the samples, CBN was be most abundant compound, reaching the highest mean concentration of 985 pg/m3, followed by COC (267 pg/m3), and CBD (214 pg/m3), there are significant differences between sampled days and locations, pointing out to specific local emissions, though the high temporal correlations between PM10 and total DAs in each site also suggest a strong influence of the meteorological conditions on the concentration of DAs in airborne matter, based on the concentrations measured, neither toxic nor psychotropic acute effects are expected from the daily exposure to these compounds.
