The strength in numbers: comprehensive characterization of house dust using complementary mass spectrometric techniques

A systematic review for non-targeted analysis of per- and polyfluoroalkyl substances (PFAS)

This review follows the PRISMA guidelines to provide a systematic review of 115 peer reviewed articles that used non-targeted analysis (NTA) methods to detect per- and polyfluoroalkylated substances (PFAS). This literature highlights the significant positive impact of NTA in understanding PFAS in the environment. Within the literature a geographical bias exists, with most NTA studies (∼60 %) conducted in the United States and China. Future studies in other regions (such as South America and Africa) are needed to gain a more global understanding. More research is required in marine environments and the atmosphere, as current studies focus mainly on freshwater, groundwater, soil, and sediments. The majority of studies focus on measuring PFAS in the environment, rather than in commercial products (with the exception of AFFF). Non-lethal blood sampling has been successful for NTA in humans and wildlife, but additional biomonitoring studies are required on exposed cohorts to understand health risks and PFAS biotransformation pathways. NTA methods mostly use liquid chromatography and negative ionisation, which biases the literature towards the detection of specific PFAS. Despite improvements in data reporting and quality assurance and control (QA/QC) procedures, factors such as false negative and false positive rates are often overlooked, and many NTA workflows remain highly subjective. Perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs) are the most detected PFAS classes, identified in over 80 % of NTA studies, and are common in routine monitoring. However, our review identified >1000 PFAS from a total of 382 different PFAS classes, with over 300 classes found in fewer than 5 % of studies. This highlights the variety of different PFAS present in the environment, and the limitations of relying solely on targeted methods. Future monitoring programs and regulations would benefit from considering NTA methods to provide more comprehensive information on PFAS present in the environment.

Comprehensive characterization of European house dust contaminants: Concentrations and profiles, geographical variability, and implications for chemical regulation and health risk

This study investigated the concentration profiles and geographical variability of contaminants in house dust across Europe. A collaborative trial (CT) was organized by the NORMAN network using pooled dust and advanced chromatographic and mass spectrometric techniques combined with suspect screening and non-target screening (NTS). Over 1200 anthropogenic compounds were tentatively identified. Additionally, seventy-five individual samples were subjected to target analysis and NTS. The median concentrations of most contaminants varied <3-fold across Europe, and the contaminant profile of European dust was similar to that of North American dust, which was investigated in a previous CT. This similarity may be attributed to the use of similar consumer articles and building materials throughout the developed world. Multivariate data analysis revealed geographical trends in contaminant distribution, with north-south gradients across Europe. Geographical trends were more frequently found for compounds with rapid release (pharmaceuticals, personal care products, fragrances, pesticides, biocides) and smoke-related compounds. The concentrations of chlorinated paraffins, polycyclic aromatic hydrocarbons (PAHs), perfluorinated alkyl substances and stimulants generally increased from north to south, whereas the biocides levels decreased from north to south. Despite widespread presence of in-use contaminants in dusts, some of the highest risks come from compounds that have been restricted for decades or more. These include di(2-ethylhexyl) phthalate (DEHP), polychlorinated biphenyl (PCB) 118 and polybrominated diphenyl ethers 47, 99, and 153. DEHP remains the most abundant contaminant in European house dust, while the other compounds are classified as persistent organic pollutants (POPs). Moreover, there is a striking lack of reliable toxicity data, particularly for emerging compounds. For instance, although acceptable daily intakes (ADIs) were examined for 202 compounds, only 46 had consensus-based ADI values. The results highlight the need for proactive measures to prevent hazardous chemicals from entering the market and for careful selection of substitute chemicals, when such are needed, to avoid regrettable substitutions.

Exploring environmental modifiers of LRRK2-associated Parkinson's disease penetrance: An exposomics and metagenomics pilot study on household dust

Pathogenic variants in the Leucine-rich repeat kinase 2 (LRRK2) gene are a primary monogenic cause of Parkinson's disease (PD). However, the likelihood of developing PD with inherited LRRK2 pathogenic variants differs (a phenomenon known as "reduced penetrance"), with factors including age and geographic region, highlighting a potential role for lifestyle and environmental factors in disease onset. To investigate this, household dust samples from four different groups of individuals were analyzed using metabolomics/exposomics and metagenomics approaches: PD+/LRRK2+ (PD patients with pathogenic LRRK2 variants; n = 11), PD-/LRRK2+ (individuals with pathogenic LRRK2 variants but without PD diagnosis; n = 8), iPD (PD of unknown cause; n = 11), and a matched, healthy control group (n = 11). The dust was complemented with metabolomics and lipidomics of matched serum samples, where available. A total of 1,003 chemicals and 163 metagenomic operational taxonomic units (mOTUs) were identified in the dust samples, of which ninety chemicals and ten mOTUs were statistically significant (ANOVA p-value < 0.05). Reduced levels of 2-benzothiazolesulfonic acid (BThSO3) were found in the PD-/LRRK2+ group compared to the PD+/LRRK2+ . Among the significant chemicals tentatively identified in dust, two are hazardous chemical replacements: Bisphenol S (BPS), and perfluorobutane sulfonic acid (PFBuS). Furthermore, various lipids were found altered in serum including different lysophosphatidylethanolamines (LPEs), and lysophosphatidylcholines (LPCs), some with higher levels in the PD+/LRRK2+ group compared to the control group. A cellular study on isogenic neurons generated from a PD+/LRRK2+ patient demonstrated that BPS negatively impacts mitochondrial function, which is implicated in PD pathogenesis. This pilot study demonstrates how non-target metabolomics/exposomics analysis of indoor dust samples complemented with metagenomics can prioritize relevant chemicals that may be potential modifiers of LRRK2 penetrance.

Hydroxyl radical oxidation of chemical contaminants on indoor surfaces and dust

Humans are widely exposed to semivolatile organic contaminants in indoor environments. Many contaminants have long lifetimes following partitioning to the large surface reservoirs present indoors, which leads to long exposure times to gas-phase oxidants and multiphase chemistry. Studies have shown selective multiphase oxidation of organics on indoor surfaces, but the presence of hydroxyl radicals with nonselective reactivity and evidence of multiphase OH radical reactivity toward common indoor contaminants indicates that there may be additional unknown transformation chemistry indoors. We screened genuine indoor samples for 60 OH radical oxidation products of the common plasticizer and endocrine-disrupting contaminant bis(2-ethylhexyl) phthalate (DEHP) identified in laboratory experiments using nontargeted high-resolution mass spectrometry. At least 30 and 10 of these products are observed in indoor dust and DEHP films exposed to ambient indoor conditions, respectively, indicating that multiphase OH reactions occur indoors. Using the PROTEX model and a multimedia indoor chemical fate model, we demonstrate that these products have long indoor lifetimes and cause a higher potential for human exposure than DEHP. Some of these products are more active endocrine disruptors than DEHP itself, but most have unknown toxicities. Coexposure to all oxidation products will likely have an additive effect, leading to higher human health risks from indoor organic contaminants than previously thought. Due to the nonselective reactivity of OH radicals, it is likely that most indoor contaminants follow similar chemistry, and further study is needed to understand the prevalence and human health implications of such multiphase chemistry.

Retention time dataset for heterogeneous molecules in reversed-phase liquid chromatography

Quantitative structure-property relationships have been extensively studied in the field of predicting retention times in liquid chromatography (LC). However, making transferable predictions is inherently complex because retention times are influenced by both the structure of the molecule and the chromatographic method used. Despite decades of development and numerous published machine learning models, the practical application of predicting small molecule retention time remains limited. The resulting models are typically limited to specific chromatographic conditions and the molecules used in their training and evaluation. Here, we have developed a comprehensive dataset comprising over 10,000 experimental retention times. These times were derived from 30 different reversed-phase liquid chromatography methods and pertain to a collection of 343 small molecules representing a wide range of chemical structures. These chromatographic methods encompass common LC setups for studying the retention behavior of small molecules. They offer a wide range of examples for modeling retention time with different LC setups.

Exploring the Chemical Space of the Exposome: How Far Have We Gone?

Around two-thirds of chronic human disease can not be explained by genetics alone. The Lancet Commission on Pollution and Health estimates that 16% of global premature deaths are linked to pollution. Additionally, it is now thought that humankind has surpassed the safe planetary operating space for introducing human-made chemicals into the Earth System. Direct and indirect exposure to a myriad of chemicals, known and unknown, poses a significant threat to biodiversity and human health, from vaccine efficacy to the rise of antimicrobial resistance as well as autoimmune diseases and mental health disorders. The exposome chemical space remains largely uncharted due to the sheer number of possible chemical structures, estimated at over 1060 unique forms. Conventional methods have cataloged only a fraction of the exposome, overlooking transformation products and often yielding uncertain results. In this Perspective, we have reviewed the latest efforts in mapping the exposome chemical space and its subspaces. We also provide our view on how the integration of data-driven approaches might be able to bridge the identified gaps.

Estimating LoD-s Based on the Ionization Efficiency Values for the Reporting and Harmonization of Amenable Chemical Space in Nontargeted Screening LC/ESI/HRMS

Nontargeted LC/ESI/HRMS aims to detect and identify organic compounds present in the environment without prior knowledge; however, in practice no LC/ESI/HRMS method is capable of detecting all chemicals, and the scope depends on the instrumental conditions. Different experimental conditions, instruments, and methods used for sample preparation and nontargeted LC/ESI/HRMS as well as different workflows for data processing may lead to challenges in communicating the results and sharing data between laboratories as well as reduced reproducibility. One of the reasons is that only a fraction of method performance characteristics can be determined for a nontargeted analysis method due to the lack of prior information and analytical standards of the chemicals present in the sample. The limit of detection (LoD) is one of the most important performance characteristics in target analysis and directly describes the detectability of a chemical. Recently, the identification and quantification in nontargeted LC/ESI/HRMS (e.g., via predicting ionization efficiency, risk scores, and retention times) have significantly improved due to employing machine learning. In this work, we hypothesize that the predicted ionization efficiency could be used to estimate LoD and thereby enable evaluating the suitability of the LC/ESI/HRMS nontargeted method for the detection of suspected chemicals even if analytical standards are lacking. For this, 221 representative compounds were selected from the NORMAN SusDat list (S0), and LoD values were determined by using 4 complementary approaches. The LoD values were correlated to ionization efficiency values predicted with previously trained random forest regression. A robust regression was then used to estimate LoD values of unknown features detected in the nontargeted screening of wastewater samples. These estimated LoD values were used for prioritization of the unknown features. Furthermore, we present LoD values for the NORMAN SusDat list with a reversed-phase C18 LC method.

Emission of volatile organic compounds during open fire cooking with wood biomass: Traditional three-stone open fire vs. gasifier cooking stove in rural Kenya

Cooking with wood biomass fuels releases hazardous air pollutants, including volatile organic compounds (VOCs), that often disproportionally affect women and children. This study, conducted in Kwale and Siaya counties in Kenya, employed thermal desorption gas chromatography - mass spectrometry to analyse VOC emissions from cooking with a wood biomass three-stone open fire vs. top-lit updraft gasifier stove. In kitchens with adequate ventilation, total VOC levels increased from 35-252 μg∙m-3 before cooking to 2235-5371 μg∙m-3 during open fire cooking, whereas use of a gasifier stove resulted in reduced emissions from cooking by 48-77 % (506-2778 μg∙m-3). However, in kitchens with poor ventilation, there was only a moderate difference in total VOC levels between the two methods of cooking (9034-9378 μg∙m-3 vs. 6727-8201 μg∙m-3 for the three-stone open fire vs. gasifier stove, respectively). Using a non-target screening approach revealed significantly increased levels of VOCs, particularly benzenoids, oxygenated and heterocyclic compounds, when cooking with the traditional open fire, especially in closed kitchens, highlighting the effects of poor ventilation. Key hazardous VOCs included benzene, naphthalene, phenols and furans, suggesting potential health risks from cooking. In kitchens with good ventilation, use of the gasifier stove markedly reduced emissions of these priority toxic VOCs compared to cooking with an open fire. Thus, substituting open fires with gasifier stoves could help to improve household air quality and alleviate health risks. The study revealed that VOCs were present prior to cooking, possibly originating from previously cooked food (buildup) or the outside environment. VOC emissions were also exacerbated by reduced air flow in high humidity during rainfall, suggesting an area for further research. The findings underscore the importance of adopting cleaner cooking technologies and enhancing kitchen ventilation to mitigate the impacts of VOCs in developing countries.

Comprehensive analysis of contaminants in Brazilian infant formulas: Application of QuEChERS coupled with UHPLC-QqQ-MS/MS and suspect screening-unknown analysis by UHPLC-Q-Orbitrap-MS

Infant formulas (IF) can contain harmful chemical substances, such as pesticides and mycotoxins, resulting from the contamination of raw materials and inputs used in the production chain, which can cause adverse effects to infants. Therefore, the quick, easy, cheap, effective, rugged, and safe (QuEChERS) methodology prior ultra-high performance liquid chromatography coupled to triple quadrupole mass spectrometry (UHPL-QqQ-MS/MS) analysis was applied for the determination of 23 contaminants, in 30 samples of Brazilian IF. The method was validated in terms of limit of detection (0.2 to 0.4 μg/kg), limits of quantification (1 and 10 μg/kg), and recovery (64 % to 122 %); precision values, in terms of relative standard deviation (RSD), were ≤ 20 %. Fenitrothion, chlorpyrifos, and bifenthrin were the pesticides detected in the samples, but the values did not exceed the limit set by the European Union (EU), and ANVISA, and they were detected under their limits of quantification. Additionally, suspect screening and unknown analysis were conducted to tentatively identify 32 substances, including some compounds not covered in this study, such as pesticides, hormones, and veterinary drugs. Carbofuran was identified, confirmed and quantified in 10 % of the samples.

Innovative non-targeted screening approach using High-resolution mass spectrometry for the screening of organic chemicals and identification of specific tracers of soil and dust exposure in children

Environmental contamination through direct contact, ingestion and inhalation are common routes of children's exposure to chemicals, in which through indoor and outdoor activities associated with common hand-to-mouth, touching objects, and behavioral tendencies, children can be susceptible and vulnerable to organic contaminants in the environment. The objectives of this study were the screening and identification of a wide range of organic contaminants in indoor dust, soil, food, drinking water, and urine matrices (N = 439), prioritizing chemicals to assess children's environmental exposure, and selection of unique tracers of soil and dust ingestion in young children by non-targeted analysis (NTA) using Q-Exactive Orbitrap followed data processing by the Compound Discoverer (v3.3, SP2). Chemical features were first prioritized based on their predominant abundance (peak area>500,000), detection frequency (in >50% of the samples), available information on their uses and potential toxicological effects. Specific tracers of soil and dust exposure in children were selected in this study including Tripropyl citrate and 4-Dodecylbenzenesulfonic acid. The criteria for selection of the tracers were based on their higher abundance, detection frequency, unique functional uses, measurable amounts in urine (suitable biomarker), and with information on gastrointestinal absorption, metabolism, and excretion, and were further confirmed by authentic standards. We are proposing for the first time suitable unique tracers for dust ingestion by children.

A Light Touch: Solar Photocatalysis Detoxifies Oil Sands Process-Affected Waters Prior to Significant Treatment of Naphthenic Acids

Environmental reclamation of Canada's oil sands tailings ponds is among the single largest water treatment challenges globally. The toxicity of oil sands process-affected water (OSPW) has been associated with its dissolved organics, a complex mixture of naphthenic acid fraction components (NAFCs). Here, we evaluated solar treatment with buoyant photocatalysts (BPCs) as a passive advanced oxidation process (P-AOP) for OSPW remediation. Photocatalysis fully degraded naphthenic acids (NAs) and acid extractable organics (AEO) in 3 different OSPW samples. However, classical NAs and AEO, traditionally considered among the principal toxicants in OSPW, were not correlated with OSPW toxicity herein. Instead, nontarget petroleomic analysis revealed that low-polarity organosulfur compounds, composing <10% of the total AEO, apparently accounted for the majority of waters' toxicity to fish, as described by a model of tissue partitioning. These findings have implications for OSPW release, for which a less extensive but more selective treatment may be required than previously expected.

Exploring the hidden chemical landscape: Non-target and suspect screening analysis for investigating solid waste-associated environments

Solid waste is an inevitable consequence of urbanization. It can be safely managed in municipal landfills and processing plants for volume reduction or material reuse, including organic solid waste. However, solid waste can also be discarded in (un-)authorized dumping sites or inadvertently released into the environment. Legacy and emerging contaminants have the potential to leach from solid waste, making it a significant pathway to the environment. Non-target screening (NTS) and suspect screening analysis (SSA) have become helpful tools in environmental science for the simultaneous analysis of a wide range of chemical compounds. However, the application of these analytical approaches to environmental samples related to Raw or Processed Solid Waste (RPSW) has been largely neglected so far. This perspective review examines the potential and policy relevance of NTS and SSA applied to waste-related samples (liquid, gaseous and solid). It addresses the hurdles associated with the chemical safety of solid waste accumulation, processing, and reuse, and the need for landfill traceability, as well as effectiveness of leachate treatments. We reviewed the current applications of NTS and SSA to environmental samples of RPSW, as well as the potential adaptation of NTS and SSA techniques from related fields, such as oilfield and metabolomics, to the solid waste domain. Despite the ongoing technical challenges, this review highlights the significant potential for the implementation of NTS and SSA approaches in solid waste management and related scientific fields and provides support and guidance to the regulatory authorities.

Identification, semi-quantification and risk assessment of contaminants of emerging concern in Flemish indoor dust through high-resolution mass spectrometry

Indoor dust can contribute substantially to human exposure to known and contaminants of emerging concern (CECs). Novel compounds with high structural variability and different homologues are frequently discovered through screening of the indoor environment, implying that constant monitoring is required. The present study aimed at the identification and semi-quantification of CECs in 46 indoor dust samples collected in Belgium by liquid chromatography high-resolution mass spectrometry. Samples were analyzed applying a targeted and suspect screening approach; the latter based on a suspect list containing >4000 CECs. This allowed the detection of a total of 55 CECs, 34 and 21 of which were identified with confidence level (CL) 1/2 or CL 3, respectively. Besides numerous known contaminants such as di(2-ethylhexyl) phthalate (DEHP), di(2-ethylhexyl) adipate (DEHA) or tris(2-butoxyethyl) phosphate (TBOEP) which were reported with detection frequencies (DFs) > 90%, several novel CECs were annotated. These included phthalates with differing side chains, such as decyl nonyl and decyl undecyl phthalate detected with DFs >80% and identified through the observation of characteristic neutral losses. Additionally, two novel organophosphate flame retardants not previously described in indoor dust, i.e. didecyl butoxyethoxyethyl phosphate (DDeBEEP) and bis(butoxyethyl) butyl phosphate (BBEBP), were identified. The implementation of a dedicated workflow provided semi-quantitative concentrations for a set of suspects. Such data obtained for novel phthalates were in the same order of magnitude as the concentrations observed for legacy phthalates indicating their high relevance for human exposure. From the semi-quantitative data, estimated daily intakes and resulting hazard quotients (HQs) were calculated to estimate the exposure and potential health effects. Neither of the obtained HQ values exceeded the risk threshold, indicating no expected adverse health effects.

Aerosolomics based approach to discover source molecular markers: A case study for discriminating residential wood heating vs garden green waste burning emission sources

Biomass burning is a significant source of particulate matter (PM) in ambient air and its accurate source apportionment is a major concern for air quality. The discrimination between residential wood heating (RWH) and garden green waste burning (GWB) particulate matter (PM) is rarely achieved. The objective of this work was to evaluate the potential of non-targeted screening (NTS) analyses using HRMS (high resolution mass spectrometry) data to reveal discriminating potential molecular markers of both sources. Two residential wood combustion appliances (wood log stove and fireplace) were tested under different output conditions and wood moisture content. GWB experiments were carried out using two burning materials (fallen leaves and hedge trimming). PM samples were characterized using NTS approaches with both LC- and GC-HRMS (liquid and gas chromatography-HRMS). The analytical procedures were optimized to detect as many species as possible. Chemical fingerprints obtained were compared combining several multivariate statistical analyses (PCA, HCA and PLS-DA). Results showed a strong impact of the fuel nature and the combustion quality on the chemical fingerprints. 31 and 4 possible markers were discovered as characteristic of GWB and RWH, respectively. Complementary work was attempted to identify potential molecular formulas of the different potential marker candidates. The combination of HRMS NTS chemical characterization with multivariate statistical analyses shows promise for uncovering organic aerosol fingerprinting and discovering potential PM source markers.

Comprehensive characterization of organic compounds in indoor dust after generic sample preparation with SUPRAS and analysis by LC-HRMS/MS

In this study supramolecular solvents (SUPRAS) are employed for the first time to perform a wide screening of organic compounds in indoor dust samples. The potential of SUPRAS to efficiently extract a wide polarity range of compounds, and to simplify and improve the green properties of sample treatment in this area are discussed. SUPRAS made up of inverse aggregates of hexanol in tetrahydrofuran:water mixtures, which have been previously and successfully applied to the target determination of a variety of organic contaminants in different environmental matrices, were employed. Analysis was done with liquid chromatography and high resolution mass spectrometry. Twelve samples from public buildings (six educative buildings, two food stores, two nightclubs, one office and a coffee shop) were collected in South Spain. A total of 146 compounds were detected by target (∼33 %), suspect (∼55 %) and non-target screening (∼12 %). Around 86 % of all the compounds were identified (or tentatively identified) with levels of confidence equal or higher than 3. Novel designer drugs of abuse, unreported organophosphorus compounds and well-known organic contaminants, such as bisphenols, parabens, phthalates and flame retardants are reported. Differences with previous studies on wide screening of indoor dust reveal the influence of the employed databases for data processing and of the extraction method together with the different contamination profiles given by the sample location.

Suspect and non-target screening of semi-volatile emerging contaminants in indoor dust from Danish kindergartens

Indoor dust is a sink of hundreds of organic chemicals, and humans may potentially be exposed to these via indoor activities. This study investigated potentially harmful semi-volatile organic contaminants in indoor dust from Danish kindergartens using suspect and non-target screening on gas chromatography (GC)-Orbitrap, supported by target analyses using GC-low resolution mass spectrometry (LRMS). A suspect list of 41 chemicals with one or more toxicological endpoints, i.e. endocrine disruption, carcinogenicity, neurotoxicity and allergenicity, known or suspected to be present in indoor dust, was established including phthalate and non-phthalate plasticizers, flame retardants, bisphenols, biocides, UV filters and other plastic additives. Of these, 29 contaminants were detected in the indoor dust samples, also including several compounds that had been banned or restricted for years. In addition, 22 chemicals were tentatively identified via non-target screening. Several chemicals have not previously been detected in Danish indoor dust. Most of the detected chemicals are known to be potentially harmful for human health while hazard assessment of the remaining compounds indicated limited risks to human. However, children were not specifically considered in this hazard assessment.

What is in the fish? Collaborative trial in suspect and non-target screening of organic micropollutants using LC- and GC-HRMS

A collaborative trial involving 16 participants from nine European countries was conducted within the NORMAN network in efforts to harmonise suspect and non-target screening of environmental contaminants in whole fish samples of bream (Abramis brama). Participants were provided with freeze-dried, homogenised fish samples from a contaminated and a reference site, extracts (spiked and non-spiked) and reference sample preparation protocols for liquid chromatography (LC) and gas chromatography (GC) coupled to high resolution mass spectrometry (HRMS). Participants extracted fish samples using their in-house sample preparation method and/or the protocol provided. Participants correctly identified 9-69 % of spiked compounds using LC-HRMS and 20-60 % of spiked compounds using GC-HRMS. From the contaminated site, suspect screening with participants' own suspect lists led to putative identification of on average ∼145 and ∼20 unique features per participant using LC-HRMS and GC-HRMS, respectively, while non-target screening identified on average ∼42 and ∼56 unique features per participant using LC-HRMS and GC-HRMS, respectively. Within the same sub-group of sample preparation method, only a few features were identified by at least two participants in suspect screening (16 features using LC-HRMS, 0 features using GC-HRMS) and non-target screening (0 features using LC-HRMS, 2 features using GC-HRMS). The compounds identified had log octanol/water partition coefficient (KOW) values from -9.9 to 16 and mass-to-charge ratios (m/z) of 68 to 761 (LC-HRMS and GC-HRMS). A significant linear trend was found between log KOW and m/z for the GC-HRMS data. Overall, these findings indicate that differences in screening results are mainly due to the data analysis workflows used by different participants. Further work is needed to harmonise the results obtained when applying suspect and non-target screening approaches to environmental biota samples.

Non-target screening and human risk assessment for adult and child populations of semi-volatile organic compounds in residential indoor dust in Spain

In this work, an analytical strategy based on non-target screening of semi-volatile organic compounds and subsequent risk assessment for adult and child populations has been conducted for the first time in household indoor dust samples in Spain. The methodology was based on a microwave-assisted extraction followed by gas chromatography coupled to high resolution mass spectrometry determination, using a hybrid quadrupole-orbitrap analyzer. The procedure was applied to 19 residential indoor dust samples, collected in different Spanish regions (namely Galicia, La Rioja, Catalunya, the Balearic Islands, and the Valencian Region). From the generated data, 4067 features were obtained, of which 474 compounds were tentatively identified with a high level of identification confidence (probable structure by library spectrum match or confirmed by reference standard), using a restrictive set of identification criteria. Most of the identified chemicals were natural products, metabolites, additives, and substances with industrial applications in the field of foods, cosmetics, pharmaceuticals, pesticides, and plastics. Finally, risk assessment was carried out by applying the threshold of toxicological concern approach, showing that risk to adult and child populations associated with the presence of the identified substances in the indoor dust was not expected, although the existence of indoor environments with conditions of potential risk cannot be discarded under a worst-case scenario approach.

An integrated non-targeted and targeted analysis approach for identification of semi-volatile organic compounds in indoor dust

Household dust contains a wide variety of semi-volatile organic compounds (SVOCs) that may pose health risks. We developed a method integrating non-targeted analysis (NTA) and targeted analysis (TA) to identify SVOCs in indoor dust. Based on a combined use of gas and liquid chromatography with high-resolution mass spectrometry, an automated, time-efficient NTA workflow was developed, and high accuracy was observed. A total of 128 compounds were identified at confidence level 1 or 2 in NIST standard reference material dust (SRM 2585). Among them, 113 compounds had not been reported previously, and this suggested the value of NTA in characterizing contaminants in dust. Additionally, TA was done to avoid the loss of trace compounds. By integrating data obtained from the NTA and TA approaches, SVOCs in SRM 2585 were prioritized based on exposure and chemical toxicity. Six of the top 20 compounds have never been reported in SRM 2585, including melamine, dinonyl phthalate, oxybenzone, diheptyl phthalate, drometrizole, and 2-phenylphenol. Additionally, significant influences of analytical instruments and sample preparation on NTA results were observed. Overall, the developed method provided a powerful tool for identifying SVOCs in indoor dust, which is necessary to obtain a more complete understanding of chemical exposures and risks in indoor environments.

Critical Assessment of the Chemical Space Covered by LC-HRMS Non-Targeted Analysis

Non-targeted analysis (NTA) has emerged as a valuable approach for the comprehensive monitoring of chemicals of emerging concern (CECs) in the exposome. The NTA approach can theoretically identify compounds with diverse physicochemical properties and sources. Even though they are generic and have a wide scope, non-targeted analysis methods have been shown to have limitations in terms of their coverage of the chemical space, as the number of identified chemicals in each sample is very low (e.g., ≤5%). Investigating the chemical space that is covered by each NTA assay is crucial for understanding the limitations and challenges associated with the workflow, from the experimental methods to the data acquisition and data processing techniques. In this review, we examined recent NTA studies published between 2017 and 2023 that employed liquid chromatography-high-resolution mass spectrometry. The parameters used in each study were documented, and the reported chemicals at confidence levels 1 and 2 were retrieved. The chosen experimental setups and the quality of the reporting were critically evaluated and discussed. Our findings reveal that only around 2% of the estimated chemical space was covered by the NTA studies investigated for this review. Little to no trend was found between the experimental setup and the observed coverage due to the generic and wide scope of the NTA studies. The limited coverage of the chemical space by the reviewed NTA studies highlights the necessity for a more comprehensive approach in the experimental and data processing setups in order to enable the exploration of a broader range of chemical space, with the ultimate goal of protecting human and environmental health. Recommendations for further exploring a wider range of the chemical space are given.

Identification and Prioritization of Environmental Organic Pollutants: From an Analytical and Toxicological Perspective

Exposure to environmental organic pollutants has triggered significant ecological impacts and adverse health outcomes, which have been received substantial and increasing attention. The contribution of unidentified chemical components is considered as the most significant knowledge gap in understanding the combined effects of pollutant mixtures. To address this issue, remarkable analytical breakthroughs have recently been made. In this review, the basic principles on recognition of environmental organic pollutants are overviewed. Complementary analytical methodologies (i.e., quantitative structure-activity relationship prediction, mass spectrometric nontarget screening, and effect-directed analysis) and experimental platforms are briefly described. The stages of technique development and/or essential parts of the analytical workflow for each of the methodologies are then reviewed. Finally, plausible technique paths and applications of the future nontarget screening methods, interdisciplinary techniques for achieving toxicant identification, and burgeoning strategies on risk assessment of chemical cocktails are discussed.

Non-targeted analysis (NTA) and suspect screening analysis (SSA): a review of examining the chemical exposome

Non-targeted analysis (NTA) and suspect screening analysis (SSA) are powerful techniques that rely on high-resolution mass spectrometry (HRMS) and computational tools to detect and identify unknown or suspected chemicals in the exposome. Fully understanding the chemical exposome requires characterization of both environmental media and human specimens. As such, we conducted a review to examine the use of different NTA and SSA methods in various exposure media and human samples, including the results and chemicals detected. The literature review was conducted by searching literature databases, such as PubMed and Web of Science, for keywords, such as "non-targeted analysis", "suspect screening analysis" and the exposure media. Sources of human exposure to environmental chemicals discussed in this review include water, air, soil/sediment, dust, and food and consumer products. The use of NTA for exposure discovery in human biospecimen is also reviewed. The chemical space that has been captured using NTA varies by media analyzed and analytical platform. In each media the chemicals that were frequently detected using NTA were: per- and polyfluoroalkyl substances (PFAS) and pharmaceuticals in water, pesticides and polyaromatic hydrocarbons (PAHs) in soil and sediment, volatile and semi-volatile organic compounds in air, flame retardants in dust, plasticizers in consumer products, and plasticizers, pesticides, and halogenated compounds in human samples. Some studies reviewed herein used both liquid chromatography (LC) and gas chromatography (GC) HRMS to increase the detected chemical space (16%); however, the majority (51%) only used LC-HRMS and fewer used GC-HRMS (32%). Finally, we identify knowledge and technology gaps that must be overcome to fully assess potential chemical exposures using NTA. Understanding the chemical space is essential to identifying and prioritizing gaps in our understanding of exposure sources and prior exposures. IMPACT STATEMENT: This review examines the results and chemicals detected by analyzing exposure media and human samples using high-resolution mass spectrometry based non-targeted analysis (NTA) and suspect screening analysis (SSA).

Construction of Pt@BiFeO3 Xerogel-Supported O-g-C3N4 Heterojunction System for Enhanced Visible-Light Activity towards Photocatalytic Degradation of Rhodamine B

Synthetic organic pigments from the direct discharge of textile effluents are considered as colossal global concern and attract the attention of scholars. The efficient construction of heterojunction systems involving precious metal co-catalysis is an effective strategy for obtaining highly efficient photocatalytic materials. Herein, we report the construction of a Pt-doped BiFeO₃/O-g-C₃N₄ (Pt@BFO/O-CN) S-scheme heterojunction system for photocatalytic degradation of aqueous rhodamine B (RhB) under visible-light irradiation. The photocatalytic performances of Pt@BFO/O-CN and BFO/O-CN composites and pristine BiFeO₃ and O-g-C₃N₄ were compared, and the photocatalytic process of the Pt@BFO/O-CN system was optimized. The results exhibit that the S-scheme Pt@BFO/O-CN heterojunction has superior photocatalytic performance compared to its fellow catalysts, which is due to the asymmetric nature of the as-constructed heterojunction. The as-constructed Pt@BFO/O-CN heterojunction reveals high performance in photocatalytic degradation of RhB with a degradation efficiency of 100% achieved after 50 min of visible-light irradiation. The photodegradation fitted well with pseudo-first-order kinetics proceeding with a rate constant of 4.63 × 10^-2 min^-1. The radical trapping test reveals that h⁺ and ^•O₂^- take the leading role in the reaction, while the stability test reveals a 98% efficiency after the fourth cycle. As established from various interpretations, the considerably enhanced photocatalytic performance of the heterojunction system can be attributed to the promoted charge carrier separation and transfer of photoexcited carriers, as well as the strong photo-redox ability established. Hence, the S-scheme Pt@BFO/O-CN heterojunction is a good candidate in the treatment of industrial wastewater for the mineralization of organic micropollutants, which pose a grievous threat to the environment.

Physico-chemical characterization of indoor settled dust in Children's microenvironments in Ikeja and Ota, Nigeria

Indoor dust is a collection of particles identified as a major reservoir for several emerging indoor chemical pollutants. This study presents indoor dust particles' morphology and elemental composition in eight children's urban and semi-urban microenvironments (A-H) in Nigeria. Samples were collected using a Tesco vacuum cleaner and analyzed with scanning electron microscopy coupled with an energy-dispersive X-ray (SEM-EDX). The morphology results confirm the presence of alumino silicates, mineral particles and flakes, fly ash and soot, and soot aggregates deposited on alumino silicate particles in the sampled microenvironments. These particles may trigger serious health concerns that directly or indirectly affect the overall well-being of children. From the EDX analysis, the trend of elements (w/w %) in the dust particles across the sampled sites was silicon (386) > oxygen (174)> aluminium (114) > carbon (34.5) > iron (28.0) > calcium (16.7) > magnesium (14.2) > sodium (7.92) > potassium (7.58) > phosphorus (2.22) > lead (2.04) > manganese (1.17) > titanium (0.21). Lead (Pb), a toxic and carcinogenic heavy metal, was observed in locations A and B. This is a concern without a safe lead level because of the neurotoxicity effect on children. As a result, further research on the concentrations, bioavailability, and health risk assessment of heavy metals in these sampled locations is recommended. Furthermore, frequent vacuum cleaning, wet moping and adequate ventilation systems will significantly reduce the accumulation of indoor dust-bound metals.

Endocrine disrupting chemicals in indoor dust: A review of temporal and spatial trends, and human exposure

Several chemicals with widespread consumer uses have been identified as endocrine-disrupting chemicals (EDCs), with a potential risk to humans. The occurrence in indoor dust and resulting human exposure have been reviewed for six groups of known and suspected EDCs, including phthalates and non-phthalate plasticizers, flame retardants, bisphenols, per- and polyfluoroalkyl substances (PFAS), biocides and personal care product additives (PCPs). Some banned or restricted EDCs, such as polybrominated diphenyl ethers (PBDEs), di-(2-ethylhexyl) phthalate (DEHP), bisphenol A (BPA), perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), are still widely detected in indoor dust in most countries, even as the predominating compounds of their group, but generally with decreasing trends. Meanwhile, alternatives that are also potential EDCs, such as bisphenol S (BPS), bisphenol F (BPF), decabromodiphenyl ethane (DBDPE) and organophosphate flame retardants (OPFRs), and PFAS precursors, such as fluorotelomer alcohols, have been detected in indoor dust with increasing frequencies and concentrations. Associations between some known and suspected EDCs, such as phthalate and non-phthalate plasticizers, FRs and BPs, in indoor dust and paired human samples indicate indoor dust as an important human exposure pathway. Although the estimated daily intake (EDI) of most of the investigated compounds was mostly below reference values, the co-exposure to a multitude of known or suspected EDCs requires a better understanding of mixture effects.

Evaluating non-targeted analysis methods for chemical characterization of organic contaminants in different matrices to estimate children's exposure

BACKGROUND

Children are vulnerable to environmental exposure of contaminants due to their small size, lack of judgement skills, as well as their proximity to dust, soil, and other environmental sources. A better understanding about the types of contaminants that children are exposed to or how their bodies retain or process these compounds is needed.

OBJECTIVE

In this study, we have implemented and optimized a methodology based on non-targeted analysis (NTA) to characterize chemicals in dust, soil, urine, and in the diet (food and drinking water) of infant populations.

METHODS

To evaluate potential toxicological concerns associated with chemical exposure, families with children between 6 months and 6 years of age from underrepresented groups were recruited in the greater Miami area. Samples of soil, indoor dust, food, water, and urine were provided by the caregivers, prepared by different techniques (involving online SPE, ASE, USE, QuEChERs), and analyzed by liquid chromatography-high resolution mass spectrometry (LC-HRMS). Data post-processing was performed using the small molecule structure identification software, Compound Discoverer (CD) 3.3, and identified features were plotted using Kendrick mass defect plot and Van Krevelen diagrams to show unique patterns in different samples and regions of anthropogenic compound classifications.

RESULTS

The performance of the NTA workflow was evaluated using quality control standards in terms of accuracy, precision, selectivity, and sensitivity, with an average of 98.2%, 20.3%, 98.4% and 71.1%, respectively. Sample preparation was successfully optimized for soil, dust, water, food, and urine. A total of 30, 78, 103, 20 and 265 annotated features were frequently identified (detection frequency >80%) in the food, dust, soil, water, and urine samples, respectively. Common features detected in each matrix were prioritized and classified, providing insight on children's exposure to organic contaminants of concern and their potential toxicities.

IMPACT STATEMENT

Current methods to assess the ingestion of chemicals by children have limitations and are generally restricted by specific classes of targeted organic contaminants of interest. This study offers an innovative approach using non-targeted analysis for the comprehensive screening of organic contaminants that children are exposed to through dust, soil, and diet (drinking water and food).

Making use of apex predator sample collections: an integrated workflow for quality assured sample processing, analysis and digital sample freezing of archived samples

Using monitoring data from apex predators for chemicals risk assessment can provide important information on bioaccumulating as well as biomagnifying chemicals in food webs. A survey among European institutions involved in chemical risk assessment on their experiences with apex predator data in chemical risk assessment revealed great interest in using such data. However, the respondents indicated that constraints were related to expected high costs, lack of standardisation and harmonised quality criteria for exposure assessment, data access, and regulatory acceptance/application. During the Life APEX project, we demonstrated that European sample collections (i.e. environmental specimen banks (ESBs), research collection (RCs), natural history museums (NHMs)) archive a large variety of biological samples that can be readily used for chemical analysis once appropriate quality assurance/control (QA/QC) measures have been developed and implemented. We therefore issued a second survey on sampling, processing and archiving procedures in European sample collections to derive key quality QA/QC criteria for chemical analysis. The survey revealed great differences in QA/QC measures between ESBs, NHMs and RCs. Whereas basic information such as sampling location, date and biometric data were mostly available across institutions, protocols to accompany the sampling strategy with respect to chemical analysis were only available for ESBs. For RCs, the applied QA/QC measures vary with the respective research question, whereas NHMs are generally less aware of e.g. chemical cross-contamination issues. Based on the survey we derived key indicators for assessing the quality of biota samples that can be easily implemented in online databases. Furthermore, we provide a QA/QC workflow not only for sampling and processing but also for the chemical analysis of biota samples. We focussed on comprehensive analytical techniques such as non-target screening and provided insights into subsequent storage of high-resolution chromatograms in online databases (i.e. digital sample freezing platform) to ultimately support chemicals risk assessment.

Distribution and health risks of organic micropollutants from home dusts in Malaysia

Indoor dust is an important medium to evaluate human exposure to emerging organic contaminants. The principal aim of this study was to determine overall status of organic micropollutants (OMPs) of indoor dust in Kuala Lumpur, Malaysia and assess their corresponding health risks. One hundred thirty-three OMPs, ascribed to 13 chemical groups, were screened by Automated Identification and Quantification System with a GC-MS database. The concentrations of OMPs ranged between 460 and 4000 μg/g, with the median concentration of 719 μg/g. The dominant chemical groups were ascribed to n-alkanes (median: 274 μg/g), plasticizers (151 μg/g), sterols (120 μg/g), and pesticides (42.6 μg/g). Cholestrol was the most abundant compound (median: 115 μg/g). Different sources and usage patterns of OMPs in various houses were expected. Toxicity values of OMPs were obtained from existing databases or predicted by quantitative structure-activity relationship models. Cumulative hazard quotients for OMPs through ingestion route were lower than one for all the dust samples, demonstrating that there was no remarkable non-cancer risk. The cancer risks of these OMPs were greater than 10^-4, with cholestrol dominating 99.1% of the carcinogenic risks, which suggested that there was a significant cancer risk. This study might offer a benchmark to ensure the safety of chemical usages in future in Malaysia.

HRMS screening of organophosphate flame retardants and poly-/perfluorinated substances in dust from cars and trucks: Occurrence and human exposure implications

Time spent within vehicles' cabin has been largely increased during the last years. As a result, the assessment of indoor dust quality is meaningful since dust can be a source of numerous emerging contaminants associated with adverse effects in human health. To this end, fourteen cars and ten trucks from the city of Thessaloniki, Northern Greece were selected to assess the quality of vehicles' microenvironments. An HRMS-based strategy was deployed for the target and non-target analysis of the collected samples. The target approach aimed at the accurate mass screening of nine organophosphate flame retardants (OPFRs) and nine per-/polyfluorinated compounds (PFAS), revealing mean concentrations for the OPFRs varied from <MQL-3409 ng/g for tris(1,3-dichloro-2-propyl) phosphate (TDCP), while the PFASs were either not detected (<MDL) or detected below the quantification limit (<MQL). To exploit the advanced technology of HRMS, a non-target analysis (NTA) workflow was also designed and employed, allowing the identification of 17 non-targets (plasticizers, PPCPs, pesticides and industrial chemicals) at identification confidence levels from 3 to 1. The statistical analysis between the positive findings and vehicles' conditions evidenced a possible of association just for individual cases. Lastly, a preliminary evaluation of human exposure to the target analytes was applied with the view to assess the potential harmful effects. All values were < 1 indicating no special effects because of exposure to this concentration level.

The NORMAN Suspect List Exchange (NORMAN-SLE): facilitating European and worldwide collaboration on suspect screening in high resolution mass spectrometry

Background

The NORMAN Association (https://www.norman-network.com/) initiated the NORMAN Suspect List Exchange (NORMAN-SLE; https://www.norman-network.com/nds/SLE/) in 2015, following the NORMAN collaborative trial on non-target screening of environmental water samples by mass spectrometry. Since then, this exchange of information on chemicals that are expected to occur in the environment, along with the accompanying expert knowledge and references, has become a valuable knowledge base for "suspect screening" lists. The NORMAN-SLE now serves as a FAIR (Findable, Accessible, Interoperable, Reusable) chemical information resource worldwide.

Results

The NORMAN-SLE contains 99 separate suspect list collections (as of May 2022) from over 70 contributors around the world, totalling over 100,000 unique substances. The substance classes include per- and polyfluoroalkyl substances (PFAS), pharmaceuticals, pesticides, natural toxins, high production volume substances covered under the European REACH regulation (EC: 1272/2008), priority contaminants of emerging concern (CECs) and regulatory lists from NORMAN partners. Several lists focus on transformation products (TPs) and complex features detected in the environment with various levels of provenance and structural information. Each list is available for separate download. The merged, curated collection is also available as the NORMAN Substance Database (NORMAN SusDat). Both the NORMAN-SLE and NORMAN SusDat are integrated within the NORMAN Database System (NDS). The individual NORMAN-SLE lists receive digital object identifiers (DOIs) and traceable versioning via a Zenodo community (https://zenodo.org/communities/norman-sle), with a total of > 40,000 unique views, > 50,000 unique downloads and 40 citations (May 2022). NORMAN-SLE content is progressively integrated into large open chemical databases such as PubChem (https://pubchem.ncbi.nlm.nih.gov/) and the US EPA's CompTox Chemicals Dashboard (https://comptox.epa.gov/dashboard/), enabling further access to these lists, along with the additional functionality and calculated properties these resources offer. PubChem has also integrated significant annotation content from the NORMAN-SLE, including a classification browser (https://pubchem.ncbi.nlm.nih.gov/classification/#hid=101).

Conclusions

The NORMAN-SLE offers a specialized service for hosting suspect screening lists of relevance for the environmental community in an open, FAIR manner that allows integration with other major chemical resources. These efforts foster the exchange of information between scientists and regulators, supporting the paradigm shift to the "one substance, one assessment" approach. New submissions are welcome via the contacts provided on the NORMAN-SLE website (https://www.norman-network.com/nds/SLE/).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12302-022-00680-6.

Estimated daily intake of per- and polyfluoroalkyl substances related to different particle size fractions of house dust

Indoor environmental pollutants are a threat to human health. In the current study, we analysed 25 per- and polyfluoroalkyl substances (PFASs) in seven different size fraction of house dust including the two relevant for exposure via ingestion and inhalation. The highest PFAS concentration is found in the inhalable particulate fraction which is explained by the increased surface area as the particulate's sizes decrease. The estimated daily intake (EDI) of the individual PFAS and exposure pathways were calculated for children and adults. In addition, the total EDI for PFOA and its precursors was estimated. The polyfluoroalkyl phosphoric acid diesters (diPAP), followed by PFOA and PFHxA fluortelomer, showed the highest concentrations of PFAS analysed. The cumulative EDI of PFAS for children was 3.0 ng/kg bw per day, a worst-case scenario, which is 17 times higher than the calculated EDI for adults. For children, ingestion of dust was found to result in 800 times higher PFOA exposure than via inhalation. The contribution from PFOA precursors corresponded to only 1% of the EDI from dust indicating PFOA as the main source of exposure. The EDI's of PFOA and PFOS from dust were lower than the calculated EDI's from food ingestion reported by the Swedish Food Agency. Our data indicate that the EDI for the sum of four PFASs: PFOA, PFNA, PFHxS and PFOS from dust intake alone is close to the established tolerable weakly intake of 4.4 ng/kg bw in children, set by European Food Safety Authority (EFSA) in 2020. The combined EDI levels PFOA and PFOS from both dust and food exceeded the EFSA TWI for both children and adults. This study demonstrates that dust is a relevant exposure pathway for PFAS intake and that analysis of relevant particle size fractions is important for evaluation of dust as an exposure pathway.

Cell-line and culture model specific responses to organic contaminants in house dust: Cell bioenergetics, oxidative stress, and inflammation endpoints

Exposure to organic contaminants in house dust is linked to the development or exacerbation of many allergic and immune disorders. In this work, we evaluate the effects of organic contaminants on different cell bioenergetics endpoints using five different cell lines (16HBE14o-, NuLi-1, A549, THP-1 and HepG2), and examine its effects on lung epithelial cells using conventional 2D and 3D (air-liquid interface/ALI) models. Proposed rapid bioenergetic assays relies on a quick, 40 min, exposure protocol that provides equivalent dose-response curves for ATP production, spare respiratory capacity, and cell respiration. Although cell-line differences play an important role in assay performance, established EC₅₀ concentrations for immortalized lung epithelial cells ranged from 0.11 to 0.15 mg/mL (∼2 µg of dust in a 96-well microplate format). Bioenergetic response of distinct cell types (i.e., monocytes and hepatocytes) was significantly different from epithelial cells; with HepG2 showing metabolic activity that might adversely affect results in 24 h exposure experiments. Like in cell bioenergetics, cell barrier function assay in ALI showed a dose dependent response. Although this is a physiologically relevant model, measurements are not as sensitivity as cytokine profiling and reactive oxygen species (ROS) assays. Observed effects are not solely explained by exposure to individual contaminants, this suggests that many causal agents responsible for adverse effects are still unknown. While 16HBE14o- cells show batter barrier formation characteristics, NuLi-1 cells are more sensitivity to oxidative stress induction even at low house dust extract concentrations, (NuLi-1 2.11-fold-change vs. 16HBE14o- 1.36-fold change) at 0.06 µg/mL. Results show that immortalized cell lines can be a suitable alternative to primary cells or other testing models, especially in the development of high-throughput assays. Observed cell line specific responses with different biomarker also highlights the importance of careful in-vitro model selection and potential drawbacks in risk assessment studies.

An actionable annotation scoring framework for gas chromatography-high-resolution mass spectrometry

Omics-based technologies have enabled comprehensive characterization of our exposure to environmental chemicals (chemical exposome) as well as assessment of the corresponding biological responses at the molecular level (eg, metabolome, lipidome, proteome, and genome). By systematically measuring personal exposures and linking these stimuli to biological perturbations, researchers can determine specific chemical exposures of concern, identify mechanisms and biomarkers of toxicity, and design interventions to reduce exposures. However, further advancement of metabolomics and exposomics approaches is limited by a lack of standardization and approaches for assigning confidence to chemical annotations. While a wealth of chemical data is generated by gas chromatography high-resolution mass spectrometry (GC-HRMS), incorporating GC-HRMS data into an annotation framework and communicating confidence in these assignments is challenging. It is essential to be able to compare chemical data for exposomics studies across platforms to build upon prior knowledge and advance the technology. Here, we discuss the major pieces of evidence provided by common GC-HRMS workflows, including retention time and retention index, electron ionization, positive chemical ionization, electron capture negative ionization, and atmospheric pressure chemical ionization spectral matching, molecular ion, accurate mass, isotopic patterns, database occurrence, and occurrence in blanks. We then provide a qualitative framework for incorporating these various lines of evidence for communicating confidence in GC-HRMS data by adapting the Schymanski scoring schema developed for reporting confidence levels by liquid chromatography HRMS (LC-HRMS). Validation of our framework is presented using standards spiked in plasma, and confident annotations in outdoor and indoor air samples, showing a false-positive rate of 12% for suspect screening for chemical identifications assigned as Level 2 (when structurally similar isomers are not considered false positives). This framework is easily adaptable to various workflows and provides a concise means to communicate confidence in annotations. Further validation, refinements, and adoption of this framework will ideally lead to harmonization across the field, helping to improve the quality and interpretability of compound annotations obtained in GC-HRMS.

Non-targeted screening of volatile organic compounds in a museum in China Using GC-Orbitrap mass spectrometry

Non-targeted analysis (NTA) was used in identifying volatile organic compounds (VOCs) in a museum in China with the gas chromatograph (GC)-Orbitrap-mass spectrometer (MS). Approximately 230 VOCs were detected, of which 117 were observed at 100% frequency across all sampling sites. Although some were common in indoor environments, most of the detected VOCs were rarely reported in previous studies on museum environments. Some of the detected VOCs were found to be associated with the materials used in furnishings and the chemicals applied in conservation treatment. Spearman's correlation analysis showed that several classes of VOCs were well correlated, suggesting their common sources. Compared with compounds in outdoor air, indoor VOCs had a lower level of unsaturation and more portions of chemically reduced compounds. Hierarchical cluster analysis (HCA) were performed. The results suggested that the sampling adsorbents chosen may have a large impact and that a single type of adsorbent may not be sufficient to cover a wide range of compounds in NTA studies. The MonoTrap adsorbent containing octadecylsilane (ODS) and activated carbon (AC) is suitable for aliphatic polar compounds that contain low levels of oxygen, whereas the MonoTrap ODS and silica gel are good at sampling aliphatic and aromatic hydrocarbons with limited polarity. Principle component analysis (PCA) showed that the indoor VOCs changed significantly at different times in the museum; this may have been caused by the removal of artifacts and refurbishment of the gallery between sampling events. A comparison with compounds identified by chamber emission tests showed that decorative materials may have been one of the main sources of indoor VOCs in the museum. The VOCs identified in the present study are likely to be present in other similar museums; therefore, further examination may be warranted of their potential impacts on cultural heritage artifacts, museum personnel, and visitors.

First Novel Workflow for Semiquantification of Emerging Contaminants in Environmental Samples Analyzed by Gas Chromatography-Atmospheric Pressure Chemical Ionization-Quadrupole Time of Flight-Mass Spectrometry

The ionization efficiency of emerging contaminants was modeled for the first time in gas chromatography-high-resolution mass spectrometry (GC-HRMS) which is coupled to an atmospheric pressure chemical ionization source (APCI). The recent chemical space has been expanded in environmental samples such as soil, indoor dust, and sediments thanks to recent use of high-resolution mass spectrometric techniques; however, many of these chemicals have remained unquantified. Chemical exposure in dust can pose potential risk to human health, and semiquantitative analysis is potentially of need to semiquantify these newly identified substances and assist with their risk assessment and environmental fate. In this study, a rigorously tested semiquantification workflow was proposed based on GC-APCI-HRMS ionization efficiency measurements of 78 emerging contaminants. The mechanism of ionization of compounds in the APCI source was discussed via a simple connectivity index and topological structure. The quantitative structure–property relationship (QSPR)-based model was also built to predict the APCI ionization efficiencies of unknowns and later use it for their quantification analyses. The proposed semiquantification method could be transferred into the household indoor dust sample matrix, and it could include the effect of recovery and matrix in the predictions of actual concentrations of analytes. A suspect compound, which falls inside the application domain of the tool, can be semiquantified by an online web application, free of access at http://trams.chem.uoa.gr/semiquantification/.

Molecular mechanisms defining penetrance of LRRK2-associated Parkinson's disease

Mutations in Leucine-rich repeat kinase 2 (LRRK2) are the most frequent cause of dominantly inherited Parkinson's disease (PD). LRRK2 mutations, among which p.G2019S is the most frequent, are inherited with reduced penetrance. Interestingly, the disease risk associated with LRRK2 G2019S can vary dramatically depending on the ethnic background of the carrier. While this would suggest a genetic component in the definition of LRRK2-PD penetrance, only few variants have been shown to modify the age at onset of patients harbouring LRRK2 mutations, and the exact cellular pathways controlling the transition from a healthy to a diseased state currently remain elusive. In light of this knowledge gap, recent studies also explored environmental and lifestyle factors as potential modifiers of LRRK2-PD. In this article, we (i) describe the clinical characteristics of LRRK2 mutation carriers, (ii) review known genes linked to LRRK2-PD onset and (iii) summarize the cellular functions of LRRK2 with particular emphasis on potential penetrance-related molecular mechanisms. This section covers LRRK2's involvement in Rab GTPase and immune signalling as well as in the regulation of mitochondrial homeostasis and dynamics. Additionally, we explored the literature with regard to (iv) lifestyle and (v) environmental factors that may influence the penetrance of LRRK2 mutations, with a view towards further exposomics studies. Finally, based on this comprehensive overview, we propose potential future in vivo, in vitro and in silico studies that could provide a better understanding of the processes triggering PD in individuals with LRRK2 mutations.

Harmonized Quality Assurance/Quality Control Provisions for Nontargeted Measurement of Urinary Pesticide Biomarkers in the HBM4EU Multisite SPECIMEn Study

A set of quality assurance/quality control (QA/QC) criteria for nontargeted measurement of pesticide exposure markers in a large-scale study of human urine has been proposed and applied across five laboratories within the HBM4EU project. Quality control material, including reference standards and fortified pooled urine samples (QC urine) were prepared in a centralized way and distributed across participants to monitor analytical performance and consistency of the liquid chromatography coupled to high-resolution mass spectrometry data generated with a harmonized workflow. Signal intensities, mass accuracy, and retention times of selected QA/QC markers covering a broad range of physicochemical properties were monitored across QC solvent standards, QC urine samples, study urine samples, and procedural blanks, setting acceptance thresholds for repeatability and accuracy. Overall, results showed high repeatability of the collected data. The RSDs of the signal intensities were typically below 20-30% in QC and study samples, with good stability of the chromatographic separation (retention time drift within 2-4 s intrabatch and 5 s interbatch) and excellent mass accuracy (average error < 2 ppm). The use of the proposed criteria allowed for the identification of handling errors, instrumental issues, and potential batch effects. This is the first elaboration of harmonized QA/QC criteria applied across multiple laboratories to assess the quality of data generated by nontargeted analysis of human samples.

Pesticides in doormat and floor dust from homes close to treated fields: Spatio-temporal variance and determinants of occurrence and concentrations

Indoor dust has been postulated as an important matrix for residential pesticide exposure. However, there is a lack of information on presence, concentrations and determinants of multiple pesticides in dust in residential homes close to treated fields. Our objective was to characterize the spatial and temporal variance of pesticides in house dust, study the use of doormats and floors as proxies for pesticides in indoor dust and identify determinants of occurrence and concentrations. Homes within 250 m from selected bulb fields were invited to participate. Homes within 20 km from these fields but not having agricultural fields within 500 m were selected as controls. House dust was vacuumed in all homes from floors (VFD) and from newly placed clean doormats (DDM). Sampling was done during two periods, when pesticides are used and not-used. For determination of 46 prioritized pesticides, a multi-residue extraction method was used. Most statistical analyses are focused on the 12 and 14 pesticides that were detected in >40% of DDM and VFD samples, respectively. Mixed models were used to evaluate relationships between possible determinants and pesticides occurrence and concentrations in DDM and VFD. 17 pesticides were detected in more than 50% of the homes in both matrixes. Concentrations differed by about a factor five between use and non-use periods among homes within 250 m of fields and between these homes and controls. For 7 pesticides there was a moderate to strong correlation (Spearman rho 0.30-0.75) between concentrations in DDM and VFD. Distance to agricultural fields and air concentrations were among the most relevant predictors for occurrence and levels of a given pesticide in DDM. Concentrations in dust are overall higher during application periods and closer to fields (<250 m) than further away. The omnipresence of pesticides in dust lead to residents being exposed all year round.

Comprehensive Screening of Pollutants in Household Dust Using High-Resolution Mass Spectrometry with Enhanced Chromatographic Resolution

Individuals spend a good portion of their lives indoors and are regularly exposed to a variety of harmful substances. Hazardous chemicals are ubiquitous, and chronic exposure via inhalation, dermal uptake, or ingestion can be detrimental to human health.The sources of pollutants in homes and places of employment include, but are not limited to, textiles, electronic devices, and building materials. Dust is a repository of a wide array of substances; therefore, it is an important indicator of chronic chemical exposure (1).

TrendProbe: Time profile analysis of emerging contaminants by LC-HRMS non-target screening and deep learning convolutional neural network

Peak prioritization is one of the key steps in non-target screening of environmental samples to direct the identification efforts to relevant and important features. Occurrence of chemicals is sometimes a function of time and their presence in consecutive days (trend) reveals important aspects such as discharges from agricultural, industrial or domestic activities. This study presents a validated computational framework based on deep learning conventional neural network to classify trends of chemicals over 30 consecutive days of sampling in two sampling sites (upstream and downstream of a river). From trend analysis and factor analysis, the chemicals could be classified into periodic, spill, increasing, decreasing and false trend. The developed method was validated with list of 42 reference standards (target screening) and applied to samples. 25 compounds were selected by the deep learning and identified via non-target screening. Three classes of surfactants were identified for the first time in river water and two of them were never reported in the literature. Overall, 21 new homologous series of the newly identified surfactants were tentatively identified. The aquatic toxicity of the identified compounds was estimated by in silico tools and a few compounds along with their homologous series showed potential risk to aquatic environment.

Spotlight on mass spectrometric non-target screening analysis: Advanced data processing methods recently communicated for extracting, prioritizing and quantifying features

Non-target screening of trace organic compounds complements routine monitoring of water bodies. So-called features need to be extracted from the raw data that preferably represent a chemical compound. Relevant features need to be prioritized and further be interpreted, for instance by identifying them. Finally, quantitative data is required to assess the risks of a detected compound. This review presents recent and noteworthy contributions to the processing of non-target screening (NTS) data, prioritization of features as well as (semi-) quantitative methods that do not require analytical standards. The focus lies on environmental water samples measured by liquid chromatography, electrospray ionization and high-resolution mass spectrometry. Examples for fully-integrated data processing workflows are given with options for parameter optimization and choosing between different feature extraction algorithms to increase feature coverage. The regions of interest-multivariate curve resolution method is reviewed which combines a data compression alternative with chemometric feature extraction. Furthermore, prioritization strategies based on a confined chemical space for annotation, guidance by targeted analysis and signal intensity are presented. Exploiting the retention time (RT) as diagnostic evidence for NTS investigations is highlighted by discussing RT indexing and prediction using quantitative structure-retention relationship models. Finally, a seminal technology for quantitative NTS is discussed without the need for analytical standards based on predicting ionization efficiencies.

An overview of organic contaminants in indoor dust, their health impact, geographical distribution and recent extraction/analysis methods

People spend a substantial proportion of their time indoors; therefore, exposure to contaminants in indoor dust is persistent and profuse. According to the findings of recent studies, contaminants such as flame retardants (FRs), organochlorines (OCs), and phthalate esters (PAEs) are more prevalent in indoor dust. The discrepancy in the geographical distribution of these chemicals indicates country-specific applications. However, many studies have revealed that chlorophosphates, polychlorinated biphenyls (PCBs) and di-2-ethylhexyl phthalate are frequently detected in indoor dust throughout the world. Although some chemicals (e.g., OCs) were banned/severely restricted decades ago, they have still been detected in indoor dust. These organic contaminants have shown clear evidence of carcinogenic, neurotoxic, immunogenic, and estrogenic activities. Recent extraction methods have shown their advantages, such as high recoveries, less solvent consumption, less extraction time and simplicity of use. The latest separation techniques such as two-dimensional gas/liquid chromatography, latest ionization techniques (e.g., matrix-assisted laser desorption/ionization (MALDI)), and modern techniques of mass spectrometry (e.g., tandem mass spectrometry (MS/MS), time-of-flight (TOF) and high-resolution mass spectrometry (HRMS)) improve the detection limits, accuracy, reproducibility and simultaneous detection of organic contaminants. For future perspectives, it is suggested that the importance of the study of dust morphology for comprehensive risk analysis, introducing standard reference materials to strengthen the analytical methods, adopt common guidelines for comparison of research findings and the importance of dust analysis in the developing world since lack of records on the production and usage of hazardous substances. Such measures will help to evaluate the effectiveness of prevailing legislations and to set up new regulations.

Novel prioritisation strategies for evaluation of temporal trends in archived white-tailed sea eagle muscle tissue in non-target screening

Environmental monitoring studies based on target analysis capture only a small fraction of contaminants of emerging concern (CECs) and miss pollutants potentially harmful to wildlife. Environmental specimen banks, with their archived samples, provide opportunities to identify new CECs by temporal trend analysis and non-target screening. In this study, archived white-tailed sea eagle (Haliaeetus albicilla) muscle tissue was analysed by non-targeted high-resolution mass spectrometry. Univariate statistical tests (Mann-Kendall and Spearman rank) for temporal trend analysis were applied as prioritisation methods. A workflow for non-target data was developed and validated using an artificial time series spiked at five levels with gradient concentrations of selected CECs (n = 243). Pooled eagle muscle tissues collected 1965-2017 were then investigated with an eight-point time series using the validated screening workflow. Following peak detection, peak alignment, and blank subtraction, 14 409 features were considered for statistical analysis. Prioritisation by time-trend analysis detected 207 features with increasing trends. Following unequivocal molecular formula assignment to prioritised features and further elucidation with MetFrag and EU Massbank, 13 compounds were tentatively identified, of which four were of anthropogenic origin. These results show that it is possible to prioritise new CECs in archived biological samples using univariate statistical approaches.

Occurrence and exposure risk assessment of organic micropollutants in indoor dust from Malaysia

Indoor dust is an important source of human exposure to hazardous organic micropollutants (OMPs) because humans spend about 90 % of their time in the indoor environments. This study initially analyzed the concentrations and compositions of OMPs in the dust of different indoor environments from Kuala Lumpur, Malaysia. A total of 57 OMPs were detected and assigned to 7 chemical classes in this study. The total concentration of OMPs ranged from 5980 to 183,000 ng/g, with the median concentration of 46,400 ng/g. Personal care products, organophosphate esters, and pesticides were the dominant groups, with their median concentrations at 12,000, 10,000, and 5940 ng/g, respectively. The concentrations and compositions of influential OMPs varied in different microenvironments, suggesting different sources and usage patterns in the house. Then, the noncarcinogenic and carcinogenic risks of exposure to these substances for diverse age groups were assessed based on the median concentration. Cumulative noncarcinogenic risks of these OMPs via ingestion pathway were estimated to be negligible (1.41 × 10^-4 - 1.87 × 10^-3). The carcinogenic risks of these OMPs were higher than 10^-6 (1.63 × 10^-6 - 6.17 × 10^-6) and should be noted. Theobromine accounted for more than 89 % of the cumulative cancer risk, implying that the carcinogenic risk of theobromine needs further monitoring in the future. Toddler was the most affected group for cancer risk among all the age groups, regardless of the microenvironments. These findings from this study may provide a benchmark for future efforts to ensure the safety of indoor dust for the local residents.

Sample preparation techniques for suspect and non-target screening of emerging contaminants

The progress in sensitivity and resolution in mass spectrometers in recent years provides the possibility to detect a broad range of organic compounds in a single procedure. For this reason, suspect and non-target screening techniques are gaining attention since they enable the detection of hundreds of known and unknown emerging contaminants in various matrices of environmental, food and human sources. Sample preparation is a critical step before analysis as it can significantly affect selectivity, sensitivity and reproducibility. The lack of generic sample preparation protocols is obvious in this fast-growing analytical field, and most studies use those of traditional targeted analysis methods. Among them, solvent extraction and solid phase extraction (SPE) are widely used to extract emerging contaminants from solid and liquid sample types, respectively. Sequential solvent extraction and a combination of different SPE sorbents can cover a broad range of chemicals in the samples. Gel permeation chromatography (GPC) and adsorption chromatography, including acidification, are typically used to remove matrix components such as lipids from complex matrices, but usually at the expense of compound losses. Ideally, the purification of samples intended for non-target analysis should be selective of matrix interferences. Recent studies have suggested quality assurance/quality control measures for suspect and non-target screening, based on expansion and extrapolation of target compound lists, but method validations remain challenging in the absence of analytical standards and harmonized sample preparation approaches.

Nontargeted Screening Using Gas Chromatography-Atmospheric Pressure Ionization Mass Spectrometry: Recent Trends and Emerging Potential

Gas chromatography–high-resolution mass spectrometry (GC–HRMS) is a powerful nontargeted screening technique that promises to accelerate the identification of environmental pollutants. Currently, most GC–HRMS instruments are equipped with electron ionization (EI), but atmospheric pressure ionization (API) ion sources have attracted renewed interest because: (i) collisional cooling at atmospheric pressure minimizes fragmentation, resulting in an increased yield of molecular ions for elemental composition determination and improved detection limits; (ii) a wide range of sophisticated tandem (ion mobility) mass spectrometers can be easily adapted for operation with GC–API; and (iii) the conditions of an atmospheric pressure ion source can promote structure diagnostic ion–molecule reactions that are otherwise difficult to perform using conventional GC–MS instrumentation. This literature review addresses the merits of GC–API for nontargeted screening while summarizing recent applications using various GC–API techniques. One perceived drawback of GC–API is the paucity of spectral libraries that can be used to guide structure elucidation. Herein, novel data acquisition, deconvolution and spectral prediction tools will be reviewed. With continued development, it is anticipated that API may eventually supplant EI as the de facto GC–MS ion source used to identify unknowns.

Application of inert gas-mediated ionization for qualitative screening of chlorinated aromatics in house dust by comprehensive two-dimensional gas chromatography-high-resolution time-of-flight mass spectrometry

The development of highly selective and sensitive analytical methods for the nontarget screening of persistent organic pollutants such as halogenated compounds in environmental samples is a challenging task. Soft ionization mass spectrometry has emerged as a powerful technique for obtaining essential molecular information, and it is expected to reveal compounds that remain hidden with conventional fragmentation techniques such as electron ionization (EI). In this study, a soft ionization method based on electron capture negative ionization using an inert gas was developed for the nontarget screening of chlorinated aromatics in environmental samples and was applied to comprehensive two-dimensional gas chromatography-high-resolution time-of-flight mass spectrometry (GC × GC-HRToFMS). In particular, argon (Ar) and helium (He) were evaluated as inert moderating gases, and were compared against the conventional methane (CH₄). The optimal ionization conditions, including the flow rate and ion source temperature, were investigated based on the molecular ion intensities of highly chlorinated aromatics decachlorobiphenyl and octachlorodibenzofuran. Ar-mediated soft ionization provided the best sensitivity to molecular ions among the three gases at a low flow rate (0.1 mL min^-1) and low ion source temperature, and more selective detection of molecular ions (i.e., less fragmentation) was obtained with the inert gases than with CH₄. This method is also applicable to other chlorinated aromatics such as tetra- to nonachlorobiphenyls, tetra- to heptachlorinated dibenzofurans, pentachlorobenzene, and hexachlorobenzene. To demonstrate the applicability of the proposed method to a wide range of chlorinated aromatics in environmental samples, both Ar-mediated soft ionization and conventional EI were applied to GC × GC-HRToFMS for analysis of a crude extract of house dust. Soft ionization enabled the selective and sensitive detection of molecular ions for minor amounts of chlorinated aromatics, even in complex matrices. Furthermore, the extracted ion chromatograms of halide anions (Cl^- or Br^-) were useful for screening other chlorinated or brominated compounds in the environmental samples. The results suggest that combining information on halide anions obtained by soft ionization and the structural information provided by EI would constitute a powerful approach for the comprehensive identification of chlorinated aromatics.

LIPAD (LRRK2/Luebeck International Parkinson's Disease) Study Protocol: Deep Phenotyping of an International Genetic Cohort

Background: Pathogenic variants in the Leucine-rich repeat kinase 2 (LRRK2) gene are the most common known monogenic cause of Parkinson's disease (PD). LRRK2-linked PD is clinically indistinguishable from idiopathic PD and inherited in an autosomal dominant fashion with reduced penetrance and variable expressivity that differ across ethnicities and geographic regions.

Objective: To systematically assess clinical signs and symptoms including non-motor features, comorbidities, medication and environmental factors in PD patients, unaffected LRRK2 pathogenic variant carriers, and controls. A further focus is to enable the investigation of modifiers of penetrance and expressivity of LRRK2 pathogenic variants using genetic and environmental data.

Methods: Eligible participants are invited for a personal or online examination which comprises completion of a detailed eCRF and collection of blood samples (to obtain DNA, RNA, serum/plasma, immune cells), urine as well as household dust. We plan to enroll 1,000 participants internationally: 300 with LRRK2-linked PD, 200 with LRRK2 pathogenic variants but without PD, 100 PD patients with pathogenic variants in the GBA or PRKN genes, 200 patients with idiopathic PD, and 200 healthy persons without pathogenic variants.

Results: The eCRF consists of an investigator-rated (1 h) and a self-rated (1.5 h) part. The first part includes the Movement Disorder Society Unified Parkinson's Disease Rating, Hoehn &Yahr, and Schwab & England Scales, the Brief Smell Identification Test, and Montreal Cognitive Assessment. The self-rating part consists of a PD risk factor, food frequency, autonomic dysfunction, and quality of life questionnaires, the Pittsburgh Sleep Quality Inventory, and the Epworth Sleepiness as well as the Hospital Anxiety and Depression Scales. The first 15 centers have been initiated and the first 150 participants enrolled (as of March 25th, 2021).

Conclusions: LIPAD is a large-scale international scientific effort focusing on deep phenotyping of LRRK2-linked PD and healthy pathogenic variant carriers, including the comparison with additional relatively frequent genetic forms of PD, with a future perspective to identify genetic and environmental modifiers of penetrance and expressivity

Clinical Trial Registration:ClinicalTrials.gov, NCT04214509.