Imperial College London

DrLeonBarron

Faculty of MedicineSchool of Public Health

Reader in Analytical & Environmental Sciences
 
 
 
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leon.barron

 
 
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Location

 

Norfolk PlaceSt Mary's Campus

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Summary

 

Publications

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89 results found

Perkins R, Barron L, Glauser G, Whitehead M, Woodward G, Goulson Det al., 2024, Down-the-drain pathways for fipronil and imidacloprid applied as spot-on parasiticides to dogs: Estimating aquatic pollution., Sci Total Environ, Vol: 917

Fipronil and imidacloprid have been widely detected in UK surface waters in recent years, often at concentrations that ecotoxicological studies have shown can harm aquatic life. Down-the-drain (DTD) passage of pet flea and tick treatments are being implicated as an important source, with many of the UK's 22 million cats and dogs receiving routine, year-round preventative doses containing these parasiticides. The UK Water Industry's 3rd Chemical Investigation Programme (UKWIR CIP3) has confirmed wastewater as a major entry pathway for these chemicals into surface waters, but the routes by which they enter the wastewater system remain unclear. We addressed this knowledge gap by conducting the first quantification of DTD emissions from 98 dogs treated with spot-on ectoparasiticides containing fipronil or imidacloprid, through bathing, bed washing and washing of owners' hands. Both chemicals were detected in 100 % of washoff samples, with bathing accounting for the largest emissions per event (up to 16.8 % of applied imidacloprid and 24.5 % of applied fipronil). Modelled to account for the frequency of emitting activities, owner handwashing was identified as the largest source of DTD emissions from the population overall, with handwash emissions occurring for at least 28 days following product application and an estimated 4.9 % of imidacloprid and 3.1 % of fipronil applied in dog spot-ons passing down-the-drain via this route. The normalised daily per capita emissions for all routes combined were 8.7 μg/person/day for imidacloprid and 2.1 μg/person/day for fipronil, equivalent to 20-40 % of the daily per capita load in wastewater, as estimated from UKWIR CIP3 data. Within the current international regulatory framework adhered to by the UK, the environmental exposure of veterinary medicines intended for use in small companion animals is assumed to be low, and DTD pathways are not considered. We recommend a systematic rev

Journal article

Egli M, Rapp Wright H, Oloyede O, Francis W, Preston-Allen R, Friedman S, Woodward G, Piel FB, Barron LPet al., 2023, A One-Health environmental risk assessment of contaminants of emerging concern in London’s waterways throughout the SARS-CoV-2 pandemic, Environment International, Vol: 180, ISSN: 0160-4120

The SARS-CoV-2 pandemic had huge impacts on global urban populations, activity and health, yet little is known about attendant consequences for urban river ecosystems. We detected significant changes in occurrence and risks from contaminants of emerging concern (CECs) in waterways across Greater London (UK) during the pandemic. We were able to rapidly identify and monitor large numbers of CECs in n=390 samples across 2019–2021 using novel direct-injection liquid chromatography-mass spectrometry methods for scalable targeted analysis, suspect screening and prioritisation of CEC risks. At total of 10,029 measured environmental concentrations (MECs) were obtained for 66 unique CECs. Pharmaceutical MECs decreased during lockdown in 2020 in the R. Thames (p≤0.001), but then increased significantly in 2021 (p ≤0.01). For the tributary rivers, the R. Lee, Beverley Brook, R. Wandle and R. Hogsmill were the most impacted primarily via wastewater treatment plant effluent and combined sewer overflows. For the R. Hosgmill in particular, pharmaceutical MEC trends were generally correlated with NHS prescription statistics, likely reflecting limited wastewater dilution. Suspect screening of ∼1,200 compounds tentatively identified 25 additional CECs at the five impacted sites, including metabolites such as O-desmethylvenlafaxine, an EU Watch List compound. Lastly, risk quotients (RQs) ≥0.1 were calculated for 21 compounds across the whole Greater London freshwater catchment, of which 7 were of medium risk (RQ ≥1.0) and three were in the high-risk category (RQ ≥10), including imidacloprid (RQ=19.6), azithromycin (15.7) and diclofenac (10.5). This is the largest spatiotemporal dataset of its kind for any major capital city globally and the first for Greater London, representing ∼16 % of the population of England, and delivering a foundational One Health case study in the third largest city in Europe across a global pandemic.

Journal article

Rapp-Wright H, Rodríguez-Mozaz S, Álvarez-Muñoz D, Barceló D, Regan F, Barron LP, White Bet al., 2023, International comparison, risk assessment, and prioritisation of 26 endocrine disrupting compounds in three European river catchments in the UK, Ireland, and Spain, Molecules, Vol: 28, Pages: 1-25, ISSN: 1420-3049

Endocrine-disrupting compounds (EDCs) constitute a wide variety of chemistries with diverse properties that may/can pose risks to both humans and the environment. Herein, a total of 26 compounds, including steroids, flame retardants, and plasticizers, were monitored in three major and heavily urbanized river catchments: the R. Liffey (Ireland), the R. Thames (UK), and the R. Ter (Spain), by using a single solid-phase extraction liquid chromatography-mass spectrometry (SPE-LC-MS/MS) method. Occurrence and frequency rates were investigated across all locations over a 10-week period, with the highest concentration obtained for the flame retardant tris(2-chloroethyl) phosphate (TCEP) at 4767 ng∙L−1 in the R. Thames in Central London. Geographical variations were observed between sites and were partially explained using principal component analysis (PCA) and hierarchical cluster analysis (HCA). In particular, discrimination between the R. Ter and the R. Thames was observed based on the presence and concentration of flame retardants, benzotriazole, and steroids. Environmental risk assessment (ERA) across sites showed that caffeine, a chemical marker, and bisphenol A (BPA), a plasticizer, were classified as high-risk for the R. Liffey and R. Thames, based on relative risk quotients (rRQs), and that caffeine was classified as high-risk for the R. Ter, based on RQs. The total risks at each location, namely ΣRQriver, and ΣrRQriver, were: 361, 455, and 723 for the rivers Liffey, Thames, and Ter, respectively. Caffeine, as expected, was ubiquitous in all 3 urban areas, though with the highest RQ observed in the R. Ter. High contributions of BPA were also observed across the three matrices. Therefore, these two compounds should be prioritized independently of location. This study represents a comprehensive EDC monitoring comparison between different European cities based on a single analytical method, which allowed for a geographically independent ERA prioritiz

Journal article

Barron L, Barron L, 2023, TRANSFERABLE MASS SPECTROMETRY METHODS: SUSTAINABLE FORENSIC INTELLIGENCE: MASS SPECTROMETRY-BASED METHODS FOR MONITORING FENTANYL-RELATED SUBSTANCES IN WASTEWATER-BASED EPIDEMIOLOGY, Application of Mass Spectrometry for the Provision of Forensic Intelligence

Journal article

Ciccarelli D, Christopher Braddock D, Surman AJ, Arenas BIV, Salal T, Marczylo T, Vineis P, Barron LPet al., 2023, Enhanced selectivity for acidic contaminants in drinking water: From suspect screening to toxicity prediction, Journal of Hazardous Materials, Vol: 448, Pages: 1-12, ISSN: 0304-3894

A novel analytical workflow for suspect screening of organic acidic contaminants in drinking water is presented, featuring selective extraction by silica-based strong anion-exchange solid-phase extraction, mixed-mode liquid chromatography-high resolution accurate mass spectrometry (LC-HRMS), peak detection, feature reduction and compound identification. The novel use of an ammonium bicarbonate-based elution solvent extended strong anion-exchange solid-phase extraction applicability to LC-HRMS of strong acids. This approach performed with consistently higher recovery and repeatability (88 ± 7 % at 500 ng L-1), improved selectivity and lower matrix interference (mean = 12 %) over a generic mixed-mode weak anion exchange SPE method. In addition, a novel filter for reducing full-scan features from fulvic and humic acids was successfully introduced, reducing workload and potential for false positives. The workflow was then applied to 10 London municipal drinking water samples, revealing the presence of 22 confirmed and 37 tentatively identified substances. Several poorly investigated and potentially harmful compounds were found which included halogenated hydroxy-cyclopentene-diones and dibromomethanesulfonic acid. Some of these compounds have been reported as mutagenic in test systems and thus their presence here requires further investigation. Overall, this approach demonstrated that employing selective extraction improved detection and helped shortlist suspects and potentially toxic chemical contaminants with higher confidence.

Journal article

Rapp-Wright H, Regan F, White B, Barron LPet al., 2023, A year-long study of the occurrence and risk of over 140 contaminants of emerging concern in wastewater influent, effluent and receiving waters in the Republic of Ireland, Science of the Total Environment, Vol: 860, ISSN: 0048-9697

Despite being a developed country in the European Union (EU), knowledge of the nature and extent of contamination of water bodies with contaminants of emerging concern (CECs) in Ireland is limited. In this study, >140 CECs including pharmaceuticals, pesticides and personal care products were monitored in monthly samples of wastewater treatment plant (WWTP) influent, effluent and receiving surface waters at both an urban and a rural location (72 samples in total) in Ireland over a 12-month period in 2018-2019. In total, 58 CECs were detected, including several EU Water Framework Directive Watch List compounds. Of all classes, the highest concentrations were measured for pharmaceuticals across all media, i.e., propranolol in surface waters (134 ng·L-1), hydrochlorothiazide in effluent (1067 ng·L-1) and venlafaxine in influent wastewater (8273 ng·L-1). Overall, high wastewater treatment removal was observed and a further reduction in CEC occurrence and concentration was measured via dilution in the receiving river environment. Lastly, an environmental risk assessment (ERA) was performed using risk quotients (RQ), which revealed that in surface waters, total RQ for all CECs was an order of magnitude lower than in effluents. The majority of CECs in surface waters posed a lower risk except E2 and EE2 which presented a medium risk (RQs of 3.5 and 1.1, respectively) in the rural area. This work represents the most comprehensive CEC monitoring dataset to date for Ireland which allowed for an ERA prioritisation to be performed for the first time.

Journal article

Adhikari S, Kumar R, Driver EM, Bowes DA, Ng KT, Sosa-Hernandez JE, Oyervides-Muñoz MA, Melchor-Martínez EM, Martínez-Ruiz M, Coronado-Apodaca KG, Smith T, Bhatnagar A, Piper BJ, McCall KL, Parra-Saldivar R, Barron LP, Halden RUet al., 2023, Occurrence of Z-drugs, benzodiazepines, and ketamine in wastewater in the United States and Mexico during the Covid-19 pandemic, Science of the Total Environment, Vol: 857, Pages: 1-9, ISSN: 0048-9697

Z-drugs, benzodiazepines and ketamine are classes of psychotropic drugs prescribed for treating anxiety, sleep disorders and depression with known side effects including an elevated risk of addiction and substance misuse. Both groups of these drugs have a strong potential for misuse, which has escalated over the years and was hypothesized here to have been exacerbated during the COVID-19 pandemic. Wastewater-based epidemiology (WBE) constitutes a fast, easy, and relatively inexpensive approach to epidemiological surveys for understanding the incidence and frequency of uses of these drugs. In this study, we analyzed wastewater (n = 376) from 50 cities across the United States and Mexico from July to October 2020 to estimate drug use rates during a pandemic event. Both time and flow proportional composite and grab samples of untreated municipal wastewater were analyzed using solid-phase extraction followed by liquid chromatography-tandem mass spectrometry to determine loadings of alprazolam, clonazepam, diazepam, ketamine, lorazepam, nordiazepam, temazepam, zolpidem, and zaleplon in raw wastewater. Simultaneously, prescription data of the aforementioned drugs were extracted from the Medicaid database from 2019 to 2021. Results showed high detection frequencies of ketamine (90 %), lorazepam (87 %), clonazepam (76 %) and temazepam (73 %) across both Mexico and United States and comparatively lower detection frequencies for zaleplon (22 %), zolpidem (9 %), nordiazepam (<1 %), diazepam (<1 %), and alprazolam (<1 %) during the pandemic. Average mass consumption rates, estimated using WBE and reported in units of mg/day/1000 persons, ranged between 62 (temazepam) and 1100 (clonazepam) in the United States. Results obtained from the Medicaid database also showed a significant change (p < 0.05) in the prescription volume between the first quarter of 2019 (before the pandemic) and the first quarter of 2021 (pandemic event) for alprazolam, clonazepam and lorazepam.

Journal article

Richardson AK, Irlam RC, Wright HR, Mills GA, Fones GR, Stürzenbaum SR, Cowan DA, Neep DJ, Barron LPet al., 2022, A miniaturized passive sampling-based workflow for monitoring chemicals of emerging concern in water, Science of The Total Environment, Vol: 839, Pages: 156260-156260, ISSN: 0048-9697

The miniaturization of a full workflow for identification and monitoring of contaminants of emerging concern (CECs) is presented. Firstly, successful development of a low-cost small 3D-printed passive sampler device (3D-PSD), based on a two-piece methacrylate housing that held up to five separate 9 mm disk sorbents, is discussed. Secondly, a highly sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method reduced the need for large scale in-laboratory apparatus, solvent, reagents and reference material quantities for in-laboratory passive sampler device (PSD) calibration and extraction. Using hydrophilic-lipophilic balanced sorbents, sampling rates (Rs) were determined after a low 50 ng L−1 exposure over seven days for 39 pesticides, pharmaceuticals, drug metabolites and illicit drugs over the range 0.3 to 12.3 mL day−1. The high sensitivity LC-MS/MS method enabled rapid analysis of river water using only 10 μL of directly injected sample filtrate to measure occurrence of 164 CECs and sources along 19 sites on the River Wandle, (London, UK). The new 3D-PSD was then field-tested over seven days at the site with the highest number and concentration of CECs, which was down-river from a wastewater treatment plant. Almost double the number of CECs were identified in 3D-PSD extracts across sites in comparison to water samples (80 versus 42 CECs, respectively). Time-weighted average CEC concentrations ranged from 8.2 to 845 ng L−1, which were generally comparable to measured concentrations in grab samples. Lastly, high resolution mass spectrometry-based suspect screening of 3D-PSD extracts enabled 113 additional compounds to be tentatively identified via library matching, many of which are currently or are under consideration for the EU Watch List. This miniaturized workflow represents a new, cost-effective, and more practically efficient means to perform passive sampling chemical monitoring at a large scale.

Journal article

Egli M, Hartmann A, Rapp Wright H, Ng KT, Piel FB, Barron LPet al., 2021, Quantitative determination and environmental risk assessment of 102 chemicals of emerging concern in wastewater-impacted rivers using rapid direct-injection liquid chromatography-tandem mass spectrometry., Molecules, Vol: 26, Pages: 1-17, ISSN: 1420-3049

The rapid source identification and environmental risk assessment (ERA) of hundreds of chemicals of emerging concern (CECs) in river water represent a significant analytical challenge. Herein, a potential solution involving a rapid direct-injection liquid chromatography-tandem mass spectrometry method for the quantitative determination of 102 CECs (151 qualitatively) in river water is presented and applied across six rivers in Germany and Switzerland at high spatial resolution. The method required an injection volume of only 10 µL of filtered sample, with a runtime of 5.5 min including re-equilibration with >10 datapoints per peak per transition (mostly 2 per compound), and 36 stable isotope-labelled standards. Performance was excellent from the low ng/L to µg/L concentration level, with 260 injections possible in any 24 h period. The method was applied in three separate campaigns focusing on the ERA of rivers impacted by wastewater effluent discharges (1 urban area in the Basel city region with 4 rivers, as well as 1 semi-rural and 1 rural area, each focusing on 1 river). Between 25 and 40 compounds were quantified directly in each campaign, and in all cases small tributary rivers showed higher CEC concentrations (e.g., up to ~4000 ng/L in total in the R. Schwarzach, Bavaria, Germany). The source of selected CECs could also be identified and differentiated from other sources at pre- and post- wastewater treatment plant effluent discharge points, as well as the effect of dilution downstream, which occurred over very short distances in all cases. Lastly, ERA for 41 CECs was performed at specific impacted sites, with risk quotients (RQs) at 1 or more sites estimated as high risk (RQ > 10) for 1 pharmaceutical (diclofenac), medium risk (RQ of 1-10) for 3 CECs (carbamazepine, venlafaxine, and sulfamethoxazole), and low risk (RQ = 0.1-1.0) for 7 CECs (i.e., RQ > 0.1 for 11 CECs in total). The application of high-throughput methods like this could ena

Journal article

Zhang C, Barron L, Sturzenbaum S, 2021, The transportation, transformation and (bio)accumulation of pharmaceuticals in the terrestrial ecosystem, Science of the Total Environment, Vol: 781, ISSN: 0048-9697

Soil dwelling organisms, plants and many primary consumers in food webs face the challenge of exposure to contaminants of emerging concern (CECs) present in terrestrial systems, including thousands of substances derived from pharmaceutical and personal care products (PPCPs). The recent increase in the consumption of modern human or veterinary drugs has resulted in a surge of anthropogenic pharmaceuticals, frequently introduced into terrestrial environments via untreated/treated wastewater. Pharmaceuticals display diverse degradation and accumulation behaviours in receiving bodies, however their impact on soils has, at large, been overlooked. Details about adsorption, absorption, degradation and uptake behaviours, as well as the fate and actual environmental impact of pharmaceuticals are a prerequisite before the traditional transportation prediction models originally designed for the aquatic environment can be extrapolated to terrestrial systems. Without this knowledge, our ability for informed risk assessments and the resultant implementation of contamination management strategies of soils will remain limited. This review discusses the current knowledgebase pertaining the introduction of pharmaceuticals to soils via wastewater irrigation or the application of biosolids. The focus on the transportation, transformation and accumulation of pharmaceuticals through the food chain highlights the urgent need to strengthen our capabilities concerning their detection and characterization in the terrestrial ecosystem.

Journal article

Richardson AK, Chadha M, Rapp-Wright H, Mills GA, Fones GR, Gravell A, Stürzenbaum S, Cowan DA, Neep DJ, Barron LPet al., 2021, Rapid direct analysis of river water and machine learning assisted suspect screening of emerging contaminants in passive sampler extracts., Analytical Methods: advancing methods and applications, Vol: 13, Pages: 595-606, ISSN: 1759-9660

A novel and rapid approach to characterise the occurrence of contaminants of emerging concern (CECs) in river water is presented using multi-residue targeted analysis and machine learning-assisted in silico suspect screening of passive sampler extracts. Passive samplers (Chemcatcher®) configured with hydrophilic-lipophilic balanced (HLB) sorbents were deployed in the Central London region of the tidal River Thames (UK) catchment in winter and summer campaigns in 2018 and 2019. Extracts were analysed by; (a) a rapid 5.5 min direct injection targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for 164 CECs and (b) a full-scan LC coupled to quadrupole time of flight mass spectrometry (QTOF-MS) method using data-independent acquisition over 15 min. From targeted analysis of grab water samples, a total of 33 pharmaceuticals, illicit drugs, drug metabolites, personal care products and pesticides (including several EU Watch-List chemicals) were identified, and mean concentrations determined at 40 ± 37 ng L-1. For targeted analysis of passive sampler extracts, 65 unique compounds were detected with differences observed between summer and winter campaigns. For suspect screening, 59 additional compounds were shortlisted based on mass spectral database matching, followed by machine learning-assisted retention time prediction. Many of these included additional pharmaceuticals and pesticides, but also new metabolites and industrial chemicals. The novelty in this approach lies in the convenience of using passive samplers together with machine learning-assisted chemical analysis methods for rapid, time-integrated catchment monitoring of CECs.

Journal article

Miller T, Ng K, Lamphiere A, Cameron T, Bury N, Barron Let al., 2021, Multicompartment and cross-species monitoring of contaminants of emerging concern in an estuarine habitat, Environmental Pollution, Vol: 270, Pages: 1-12, ISSN: 0269-7491

The fate of many chemicals in the environment, particularly contaminants of emerging concern (CEC), have been characterised to a limited extent with a major focus on occurrence in water. This study presents the characterisation, distribution and fate of multiple chemicals including pharmaceuticals, recreational drugs and pesticides in surface water, sediment and fauna representing different food web endpoints in a typical UK estuary (River Colne, Essex, UK). A comparison of contaminant occurrence across different benthic macroinvertebrates was made at three sites and included two amphipods (Gammarus pulex & Crangon crangon), a polychaete worm (Hediste diversicolor) and a gastropod (Peringia ulvae). Overall, multiple contaminants were determined in all compartments and ranged from; <LOQ – 386 ng∙L-1 in surface water (n=59 compounds), <LOQ – 146 ng∙g-1 in sediment (n=39 compounds) and <LOQ – 91 ng∙g-1 biota (n=33 compounds). H. diversicolor and P. ulvae (sediment dwellers) showed greater chemical body burden compared with the two swimming amphipod species sampled (up to 2.5 - 4-fold). The most frequently determined compounds in biota (100%, n=36 samples) included; cocaine, benzyoylecgonine, carbamazepine, sertraline and diuron. Whilst some of the highest concentrations found were in species H. diverscolor and P. ulvae for psychoactive pharmaceuticals including citalopram (91 ng∙g-1), sertraline (69 ng∙g-1), haloperidol (66 ng∙g-1) and the neonicotinoid, imidacloprid (33 ng∙g-1) Sediment was noted as an important exposure route for these benthic dwelling organisms and will be critical to monitor in future studies. Overall, the analysis of multiple species and compartments demonstrates the importance of including a range of exposure pathways in order to appropriately assess chemical fates and associated risks in the aquatic environment. Keywords: Occurrence, Pesticides, Pharmaceuticals, Environmental Risk, Sediment, Invertebrate

Journal article

Alsaleh SA, Barron L, Sturzenbaum S, 2021, Perchlorate detection via an invertebrate biosensor, Analytical Methods: advancing methods and applications, Vol: 13, Pages: 327-336, ISSN: 1759-9660

Improvised explosive devices (IEDs) are constructed from easily obtainable ingredients that are often unregulated and difficult to trace. Salts of the oxyhalide perchlorate are frequently used as oxidisers in IEDs and in commercially available munitions, thus a reliable detection is needed to aid forensic investigations and the tracing of environmental ground or surface water contamination. We introduce the nematode Caenorhabditis elegans as a biosensor for the presence of perchlorate, a promising alternative to the costly, technically challenging and time-consuming current perchlorate detection methods. Perchlorate uptake dynamics in C. elegans were first validated using ion exchange chromatography followed by assessing the effects of perchlorate on key life-point indices to verify the suitability of the nematodes as a forensic biosensor. Whole genome microarrays and qPCR analyses established that a set of immune and stress response genes were enriched during perchlorate exposure. A nematode strain (agIs219) containing an integrated copy of the significantly overexpressed t24b8.5 gene promoter followed by a GFP reporter gene was shown to fluoresce in a perchlorate dose dependent manner with a limit of detection (LOD) of 0.5 mg mL−1. Whilst chemicals commonly used in the construction of IEDs did not induce fluorescence, exposure to other oxyhalides did, highlighting the presence of possible shared stress response pathways. Burnt wire sparklers containing potassium perchlorate elicited fluorescence while other non-perchlorate containing post-blast explosion matrices did not. This demonstrates how C. elegans can be used to screen for perchlorate at environmental hotspots, an optimization, possibly with other target transgenes, is required to enable the detection of perchlorate at concentrations below 0.5 mg mL−1.

Journal article

Dominguez-Fernandez M, Xu Y, Yang PYT, Alotaibi W, Gibson R, Hall WL, Barron L, Ludwig IA, Cid C, Rodriguez-Mateos Aet al., 2021, Quantitative assessment of dietary (Poly)phenol intake: a high-throughput targeted metabolomics method for blood and urine samples, Journal of Agricultural and Food Chemistry, Vol: 69, Pages: 537-554, ISSN: 0021-8561

Many studies have associated the consumption of (poly)phenol-rich diets with health benefits. However, accurate high-throughput quantitative methods for estimating exposure covering a broad spectrum of (poly)phenols are lacking. We have developed and validated a high-throughput method for the simultaneous quantification of 119 (poly)phenol metabolites in plasma and urine using ultra high-performance liquid chromatography coupled with triple quadrupole mass spectrometry, with a very fast sample treatment and a single run time of 16 min. This method is highly sensitive, precise, accurate, and shows good linearity for all compounds (R2 > 0.992). This novel method will allow a quantitative assessment of habitual (poly)phenol intake in large epidemiological studies as well as clinical studies investigating the health benefits of dietary (poly)phenols.

Journal article

Sheikholeslami MN, Gómez-Canela C, Barron LP, Barata C, Vosough M, Tauler Ret al., 2020, Untargeted metabolomics changes on Gammarus pulex induced by Propranolol, Triclosan, and Nimesulide pharmaceutical drugs, Chemosphere, Vol: 260, ISSN: 0045-6535

The presence of pharmaceuticals and personal care products (PPCPs) in natural water resources due to incomplete removal in Wastewater Treatment Plants (WWTPs) is a serious environmental concern at present. In this work, the effects of three pharmaceuticals (propranolol, triclosan, and nimesulide) on Gammarus pulex metabolic profiles at different doses and times of exposure have been investigated by liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS). The complex data sets generated in the different exposure experiments were analyzed with the ROIMCR procedure, based on the selection of the MS regions of interest (ROI) data and on their analysis by the Multivariate Curve-Resolution Alternating Least Squares (MCR-ALS) chemometrics method. This approach, allowed the resolution and identification of the metabolites present in the analyzed samples, as well as the estimation of their concentration changes due to the exposure experiments. ANOVA Simultaneous Component Analysis (ASCA) and Partial Least Squares Discriminant Analysis (PLS-DA) were then conducted to assess the changes in the concentration of the metabolites for the three pharmaceuticals at the different conditions of exposure. The three tested pharmaceuticals changed the concentrations of metabolites, which were related to different KEGG functional classes. These changes summarize the biochemical response of Gammarus pulex to the exposure by the three investigated pharmaceuticals. Possible pathway alterations related to protein synthesis and oxidative stress were observed in the concentration of identified metabolites.

Journal article

Ng KT, Rapp-Wright H, Egli M, Hartmann A, Steele JC, Sosa-Hernández JE, Melchor-Martínez EM, Jacobs M, White B, Regan F, Parra-Saldivar R, Couchman L, Halden RU, Barron LPet al., 2020, High-throughput multi-residue quantification of contaminants of emerging concern in wastewaters enabled using direct injection liquid chromatography-tandem mass spectrometry., Journal of Hazardous Materials, Vol: 398, Pages: 1-14, ISSN: 0304-3894

A rapid quantitative method for 135 contaminants of emerging concern (CECs) in untreated wastewater enabled with direct injection liquid chromatography-tandem mass spectrometry is presented. All compounds were analysed within 5 min on a short biphenyl cartridge using only 10 μL of filtered sample per injection. Up to 76 compounds were monitored simultaneously during the gradient (including mostly two transitions per compound and stable isotope-labelled analogues) while yielding >10 data points per peak. Evaluation of seven solid phase extraction sorbents showed no advantage for wastewater matrix removal. Excellent linearity, range, accuracy and precision was achieved for most compounds. Matrix effects were <11 % and detection limits were <30 ng L-1 on average. Application to untreated wastewater samples from three wastewater treatment works in the UK, USA and Mexico, enabled quantification of 56 compounds. Banned and EU 'watch-list' substances are critically discussed, including pesticides, macrolide antibiotics, diclofenac, illicit drugs as well as multiple pharmaceuticals and biocides. This high-throughput method sets a new standard for the speedy and confident determination of over a hundred CECs in wastewater at the part-per-trillion level, as demonstrated by performing over 260 injections per day.

Journal article

Irlam R, Hughes C, Parkin M, Beardah M, O'Donnell M, Brabazon D, Barron Let al., 2020, Trace multi-class organic explosives analysis in complex matrices enabled using LEGO®-inspired clickable 3D-printed solid phase extraction block arrays, Journal of Chromatography A, Vol: 1629, ISSN: 0021-9673

The development of a new, lower cost method for trace explosives recovery from complex samples is presented using miniaturised, click-together and leak-free 3D-printed solid phase extraction (SPE) blocks. For the first time, a large selection of ten commercially available 3D printing materials were comprehensively evaluated for practical, flexible and multiplexed SPE using stereolithography (SLA), PolyJet and fused deposition modelling (FDM) technologies. Miniaturised single-piece, connectable and leak-free block housings inspired by Lego® were 3D-printed in a methacrylate-based resin, which was found to be most stable under different aqueous/organic solvent and pH conditions, using a cost-effective benchtop SLA printer. Using a tapered SPE bed format, frit-free packing of multiple different commercially available sorbent particles was also possible. Coupled SPE blocks were then shown to offer efficient analyte enrichment and a potentially new approach to improve the stability of recovered analytes in the field when stored on the sorbent, rather than in wet swabs. Performance was measured using liquid chromatography-high resolution mass spectrometry and was better, or similar, to commercially available coupled SPE cartridges, with respect to recovery, precision, matrix effects, linearity and range, for a selection of 13 peroxides, nitramines, nitrate esters and nitroaromatics. Mean % recoveries from dried blood, oil residue and soil matrices were 79 ± 24%, 71 ± 16% and 76 ± 24%, respectively. Excellent detection limits between 60 fg for 3,5-dinitroaniline to 154 pg for nitroglycerin were also achieved across all matrices. To our knowledge, this represents the first application of 3D printing to SPE of so many organic compounds in complex samples. Its introduction into this forensic method offered a low-cost, ‘on-demand’ solution for selective extraction of explosives, enhanced flexibility for multiplexing/design alteration and po

Journal article

Barron LP, 2020, Spatio-temporal assessment of illicit drug use at large scale: evidence from seven years of international wastewater monitoring, Addiction, Vol: 115, Pages: 109-120, ISSN: 0965-2140

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 seven years (2011-2017); (ii) address overall drug use by estimating the average number of combined doses consumed per day in each city. Design: Analysis of daily composite raw wastewater samples collected over one week per year from 2011 to 2017. Setting: Catchment areas of 143 wastewater treatment plants in 120 cities in 37 countries. Methods: 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 worldwide, and temporal trends were discerned at European level by comparing 2011-2013 drug loads versus 2014-2017 loads. Findings: Benzoylecgonine was the stimulant metabolite detected at higher loads in southern and western Europe, and amphetamine, MDMA, and methamphetamine in the east and the north-centre of Europe. In other continents methamphetamine showed the highest levels in the United States and Australia and benzoylecgonine in South America. Over 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 updated and objective estimates of drug use that globally correspond to prevalence

Journal article

Irlam RC, Parkin MC, Brabazon DP, Beardah MS, O'Donnell M, Barron LPet al., 2019, Improved determination of femtogram-level organic explosives in multiple matrices using dual-sorbent solid phase extraction and liquid chromatography-high resolution accurate mass spectrometry, Talanta, Vol: 203, Pages: 65-76, ISSN: 0039-9140

Identification and trace quantification of multiple explosives residues, their precursors and transformation products in complex samples remains very challenging. For solid phase extraction (SPE) and liquid chromatography-high resolution accurate mass spectrometry-based methods (LC-HRMS), interferences from co-extracted matrix components can significantly affect recovery during extraction and/or detector signal. The aim of this work was to develop a new, improved and more generalisable extraction approach to trace explosives analysis in a range of matrices using dual-sorbent SPE with LC-HRMS. Recoveries of 44 organic explosives from model solutions were optimised and compared for seven different sorbents (Oasis HLB, HyperSep Retain PEP and Isolute ENV+, HyperSep SAX, HyperSep NH2, Strata Alumina-N and Bond Elut CN). On average, Oasis HLB and Isolute ENV+ yielded the best recoveries (>80 %). For three sorbents, mean recoveries remained ≤1 %, which made them potentially suitable for matrix removal when used in series with more analyte-selective sorbents. To evaluate matrix effects, a range of aqueous (river- and wastewater), solid (soil), dirty (road sign swabs), oily (oven hood swabs) and biological (dried blood) samples were selected based on complexity and forensic relevance. With the exception of river water, matrix effects were lowest using dual-sorbent SPE, with little/no compromise in recovery. Quantitative method performance assessment is presented for 14 selected explosives, representative of different classes, molecular weights and volatilities, and across three different matrices (i.e. untreated wastewater, cooking oil residues and dried blood). Limits of detection improved by ~10-fold over a single sorbent approach, enabling fg sensitivity in many cases. Finally, application of the method to untreated wastewater enabled detection of new explosives traces for the first time, which could be used to help identify clandestine manufacture or sources of en

Journal article

Gallidabino MD, Irlam RC, Salt MC, O'Donnell M, Beardah MS, Barron LPet al., 2019, Targeted and non-targeted forensic profiling of black powder substitutes and gunshot residue using gradient ion chromatography – high resolution mass spectrometry (IC-HRMS), Analytica Chimica Acta, Vol: 1072, Pages: 1-14, ISSN: 0003-2670

A novel and simplified gradient IC-HRMS approach is presented in this work for forensic profiling of ionic energetic material residues, including low-order explosives and gunshot residue (GSR). This new method incorporated ethanolic eluents to facilitate direct coupling of IC and HRMS without auxiliary post-column infusion pumps that are traditionally used to assist with gas phase transfer. Ethanolic eluents also enabled better integration with an in-service protocol for direct analysis of high-order organic explosives by ICHRMS, without requiring solvent exchange before injection. Excellent method performance was achieved, enabling both full scan qualitative and quantitative analysis, as required. In particular, linearity for 19 targeted compounds yielded R2 > 0.99 across several orders of magnitude, with trace analysis possible at the low-mid pg level. Reproducibility and mass accuracies were also excellent, with peak area %RSDs < 10 %, tR %RSDs < 0.4% and δm/z < 3 ppm. The method was applied to targeted analysis of latent fingermarks and swabbed hand sweat samples to determine contact with a black-powder substitute containing nitrate, benzoate and perchlorate. When combined with principal component analysis (PCA), the effect of time since handling on recorded signals could be interpreted further in order to support forensic investigations. In a second, non-targeted application, PCA using full scan IC-HRMS data enabled classification of GSR from three different types of ammunition. An additional 20 markers of GSR were tentatively identified in silico, in addition to the 15 anions detected during targeted analysis. This new approach therefore streamlines and adds consistency and flexibility to forensic analysis of ionic energetic material. Furthermore, it also has implications for targeted, non-targeted and suspect screening applications in other fields by expanding the separation space to low molecular weight inorganic and organic anions.

Journal article

Barron L, Loftus N, 2019, Gradient retention time predictopm for 653 pesticides on a biphenyl column using machine learning, Chromatography Today

Journal article

Miller TH, Ng KT, Bury ST, Bury SE, Bury NR, Barron LPet al., 2019, Biomonitoring of pesticides, pharmaceuticals and illicit drugs in a freshwater invertebrate to estimate toxic or effect pressure, Environment International, Vol: 129, Pages: 595-606, ISSN: 0160-4120

Multiple classes of environmental contaminants have been found in aquatic environments, globally. Understanding internalised concentrations in the organism could further improve the risk assessment process. The present study is concerned with the determination of several contaminant classes (107 compounds) in Gammarus pulex collected from 15 sites covering 5 river catchments across Suffolk, UK. Quantitative method performance was acceptable for 67 compounds including pharmaceuticals, pesticides, illicit drugs and drugs of abuse. A total of 56 compounds were detectable and ranged from <LOQ to 45.3 ng g-1, with cocaine and lidocaine being the most frequently detected compounds present in all biota samples (n=66). For surface water, 50 compounds were detectable and ranged from <LOQ to 382.2 ng L-1. Additionally, some pesticides currently not approved for use were detected, including fenuron that reached a maximum of 16.1 ng g-1. The internal concentrations of pesticides were used to estimate toxic pressure which showed that for the measured pesticides toxic pressure was low ranging from logTU ≤-7 to ≤-2. This methodology was extended to pharmaceuticals and drugs of abuse in a novel approach that proposed the use of pharmacological data (human therapeutic plasma concentrations) to estimate the likelihood of an effect (or effect pressure) to occur based on the internal exposure of the organism. The quantified effect pressure ranged from logEU ≤-9 to ≤1 with haloperidol showing the largest likelihood for an effect. The approach showed that several pharmaceuticals have the potential to elicit effects but further investigation surrounding thresholds for effects would be required. This new approach presented showed potential to be used to improve risk assessment for pharmaceuticals in the environment.

Journal article

Shimko KM, O'Brien JW, Barron L, Kayalar H, Mueller JF, Tscharke BJ, Choi PM, Jiang H, Eaglesham G, Thomas KVet al., 2019, A pilot wastewater-based epidemiology assessment of anabolic steroid use in Queensland, Australia, Drug Testing And Analysis, Vol: 11, Pages: 937-949, ISSN: 1942-7603

Anabolic‐androgenic steroids are synthetic compounds prohibited due to their performance enhancing characteristics. The use of these substances is known to cause health‐related issues, which highlights the importance of being able to evaluate the scale of consumption by the general population. However, most available research on the analysis of anabolic steroids is focussed on animals and athletes in connection with doping. The potential of wastewater‐based epidemiology as an intelligence tool for the assessment of community level use of anabolic steroids is presented herein. A liquid chromatography tandem mass spectrometry method was developed for the analysis of ten anabolic‐androgenic steroids and 14 endogenous hormones in influent wastewater. The validated method was applied to sixteen 24‐hour composite wastewater influent samples that were collected over a period of five years from two wastewater treatment plants in Queensland, Australia. Nine investigated compounds were found to be present at concentrations between 14‐611 ng L‐1 which translated into 3‐104 mg excreted per 1000 individuals per day. It was concluded that the developed analytical method is suitable for the analysis of AAS in wastewater matrix. Additionally, both the inclusion of metabolites and further investigation into deconjugation by enzymatic hydrolysis would aid in understanding and evaluating community anabolic steroid use. For the first time, this study presents the application of wastewater‐based epidemiology on anabolic‐androgenic steroids in Australia.

Journal article

Munro K, Martins CPB, Loewenthal M, Comber S, Cowan DA, Pereira L, Barron LPet al., 2019, Evaluation of combined sewer overflow impacts on short-term pharmaceutical and illicit drug occurrence in a heavily urbanised tidal river catchment (London, UK), Science of the Total Environment, Vol: 657, Pages: 1099-1111, ISSN: 0048-9697

The occurrence of pharmaceutical and illicit drug residues potentially arising from combined sewer overflows (CSOs) in the Central London portion of the Thames Estuary is presented. Approximately 39 million tonnes of untreated sewage enter the River Thames at 57 CSO points annually. Differential analysis of influents and effluents in a major wastewater treatment plant identified seven potential drug-related CSO markers based on removal rates. Three were present in influent at concentrations >1 μg L−1 (caffeine, cocaine and benzoylecgonine). During dry weather, analysis of hourly samples of river water revealed relatively consistent concentrations for most drugs, including CSO markers, over a tidal cycle. River water was monitored over a week in January and July and then daily across six consecutive weeks in November/December 2014. Out of 31 compounds monitored, 27 drug residues were determined in the River Thames and, combined, ranged between ~1000–3500 ng L−1. Total drug concentration generally declined during extended periods of drier weather. For CSO markers, short-term increases in caffeine, cocaine and benzoylecgonine concentration were observed ~24 h after CSO events (especially those occurring at low tide) and generally within one order of magnitude. Timings of elevated occurrence also correlated well with ammonium ion and dissolved oxygen data following CSOs. This work also represents an important study of pharmaceutical occurrence before a major 'super Sewer’ infrastructure upgrade in London aiming to reduce CSOs by 95%.

Journal article

Miller TH, Gallidabino MD, MacRae JI, Owen SF, Bury NR, Barron LPet al., 2019, Prediction of bioconcentration factors in fish and invertebrates using machine learning, Science of the Total Environment, Vol: 648, Pages: 80-89, ISSN: 0048-9697

The application of machine learning has recently gained interest from ecotoxicological fields for its ability to model and predict chemical and/or biological processes, such as the prediction of bioconcentration. However, comparison of different models and the prediction of bioconcentration in invertebrates has not been previously evaluated. A comparison of 24 linear and machine learning models is presented herein for the prediction of bioconcentration in fish and important factors that influenced accumulation identified. R2 and root mean square error (RMSE) for the test data (n = 110 cases) ranged from 0.23–0.73 and 0.34–1.20, respectively. Model performance was critically assessed with neural networks and tree-based learners showing the best performance. An optimised 4-layer multi-layer perceptron (14 descriptors) was selected for further testing. The model was applied for cross-species prediction of bioconcentration in a freshwater invertebrate, Gammarus pulex. The model for G. pulex showed good performance with R2 of 0.99 and 0.93 for the verification and test data, respectively. Important molecular descriptors determined to influence bioconcentration were molecular mass (MW), octanol-water distribution coefficient (logD), topological polar surface area (TPSA) and number of nitrogen atoms (nN) among others. Modelling of hazard criteria such as PBT, showed potential to replace the need for animal testing. However, the use of machine learning models in the regulatory context has been minimal to date and is critically discussed herein. The movement away from experimental estimations of accumulation to in silico modelling would enable rapid prioritisation of contaminants that may pose a risk to environmental health and the food chain.

Journal article

Gallidabino MD, Barron LP, Weyermann C, Romolo FSet al., 2019, Quantitative profile-profile relationship (QPPR) modelling, A novel machine learning approach to predict and associate chemical characteristics of unspent ammunition from gunshot residue (GSR), Vol: 144, Pages: 1128-1139, ISSN: 0003-2654

Evidence association in forensic cases involving gunshot residue (GSR) remains very challenging. Herein, a new in silico approach, called quantitative profile-profile relationship (QPPR) modelling, is reported. This is based on the application of modern machine learning techniques to predict the pre-discharge chemical profiles of selected ammunition components from those of the respective post-discharge GSR. The obtained profiles can then be compared with one another and/or with other measured profiles to make evidential links during forensic investigations. In particular, the approach was optimised and successfully tested for the prediction of GC-MS profiles of smokeless powders (SLPs) from organic GSR in spent cases, for nine ammunition types. Results showed a high degree of similarity between predicted and experimentally measured profiles, after adequate combination and evaluation of fourteen machine learning techniques (median correlation of 0.982). Areas under the curve (AUCs) of 0.976 and 0.824 were observed after receiver operating characteristic (ROC) analysis of the results obtained in the comparisons between predicted-predicted and predicted-measured profiles, respectively, in the specific case that the ammunition types of interest were excluded from the training dataset (i.e., extrapolation). Furthermore, AUCs of 0.962 and 0.894 were observed in interpolation mode. These values were close to those of the comparison of the measured SLP profiles between themselves (AUC = 0.998), demonstrating excellent potential to correctly associate evidence in a number of different forensic scenarios. This work represents the first time that a quantitative approach has successfully been applied to associate a GSR to a specific ammunition.

Journal article

Miller TH, Gallidabino MD, Macrae JI, Hogstrand C, Bury NR, Barron LP, Snape JR, Owen SFet al., 2018, Machine learning for environmental toxicology, A Call for Integration and Innovation, Vol: 52, Pages: 12953-12955, ISSN: 0013-936X

Journal article

Aliferi A, Ballard D, Gallidabino MD, Thurtle H, Barron L, Syndercombe Court Det al., 2018, DNA methylation-based age prediction using massively parallel sequencing data and multiple machine learning models, Forensic Science International-Genetics, Vol: 37, Pages: 215-226, ISSN: 1872-4973

The field of DNA intelligence focuses on retrieving information from DNA evidence that can help narrow down large groups of suspects or define target groups of interest. With recent breakthroughs on the estimation of geographical ancestry and physical appearance, the estimation of chronological age comes to complete this circle of information. Recent studies have identified methylation sites in the human genome that correlate strongly with age and can be used for the development of age-estimation algorithms. In this study, 110 whole blood samples from individuals aged 11-93 years were analysed using a DNA methylation quantification assay based on bisulphite conversion and massively parallel sequencing (Illumina MiSeq) of 12 CpG sites. Using this data, 17 different statistical modelling approaches were compared based on root mean square error (RMSE) and a Support Vector Machine with polynomial function (SVMp) model was selected for further testing. For the selected model (RMSE = 4.9 years) the mean average error (MAE) of the blind test (n = 33) was calculated at 4.1 years, with 52% of the samples predicting with less than 4 years of error and 86% with less than 7 years. Furthermore, the sensitivity of the method was assessed both in terms of methylation quantification accuracy and prediction accuracy in the first validation of this kind. The described method retained its accuracy down to 10 ng of initial DNA input or ~2 ng bisulphite PCR input. Finally, 34 saliva samples were analysed and following basic normalisation, the chronological age of the donors was predicted with less than 4 years of error for 50% of the samples and with less than 7 years of error for 70%.

Journal article

Miller TH, Bury NR, Owen SF, MacRae JI, Barron LPet al., 2018, A review of the pharmaceutical exposome in aquatic fauna, Environmental Pollution, Vol: 239, Pages: 129-146, ISSN: 0269-7491

Pharmaceuticals have been considered ‘contaminants of emerging concern’ for more than 20 years. In that time, many laboratory studies have sought to identify hazard and assess risk in the aquatic environment, whilst field studies have searched for targeted candidates and occurrence trends using advanced analytical techniques. However, a lack of a systematic approach to the detection and quantification of pharmaceuticals has provided a fragmented literature of serendipitous approaches. Evaluation of the extent of the risk for the plethora of human and veterinary pharmaceuticals available requires the reliable measurement of trace levels of contaminants across different environmental compartments (water, sediment, biota - of which biota has been largely neglected). The focus on pharmaceutical concentrations in surface waters and other exposure media have therefore limited both the characterisation of the exposome in aquatic wildlife and the understanding of cause and effect relationships. Here, we compile the current analytical approaches and available occurrence and accumulation data in biota to review the current state of research in the field. Our analysis provides evidence in support of the ‘Matthew Effect’ and raises critical questions about the use of targeted analyte lists for biomonitoring. We provide six recommendations to stimulate and improve future research avenues.

Journal article

van Nuijs ALN, Lai FY, Been F, Jesus Andres-Costa M, Barron L, Baz-Lomba JA, Berset J, Benaglia L, Bijlsma L, Burgard D, Castiglioni S, Christophoridis C, Covaci A, de Voogt P, Emke E, Fatta-Kassinos D, Fick J, Hernandez F, Gerber C, González-Mariño I, Grabic R, Gunnar T, Kannan K, Karolak S, Kasprzyk-Hordern B, Kokot Z, Krizman-Matasic I, Li A, Li X, Löve ASC, Lopez de Alda M, Meyer MR, Oberacher H, OBrien J, Benito Quintana J, Reid M, Schneider S, Simoes SS, Thomaidis NS, Thomas K, Yargeau V, Ort Cet al., 2018, Multi-year interlaboratory exercises for the analysis of illicit drugs and metabolites in wastewater, TrAC - Trends in Analytical Chemistry, Vol: 103, Pages: 34-43, ISSN: 0165-9936

This study presents the development of a worldwide inter-laboratory testing scheme for the analysis of seven illicit drug residues in different matrices (standard solutions, tap- and wastewater). By repeating this exercise for six years with participation of 37 laboratories from 25 countries, the testing scheme was substantially improved based on experiences gained across the years (e.g. matrix type, sample conditions, spiking levels). From the exercises (pre-)analytical issues (e.g. pH adjustment, filtration), were revealed for some analytes which resulted in formulation of best-practice protocols, both for inter-laboratory setup and analytical procedures. The results illustrate the effectiveness of the inter-laboratory testing scheme in assessing laboratory performance in the framework of illicit drug analysis in wastewater. The exercise proved that measurements of laboratories were of high quality (>80% satisfactory results for 6 out of 7 analytes) and that analytical follow-up is important to assist laboratories in improving robustness of wastewater-based epidemiology results.

Journal article

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