Accumulation of perfluorooctane sulfonate (PFOS) has been demonstrated in biota across the globe. Higher trophic-level air-breathing organisms that live in or depend on aquatic ecosystems are most at risk from PFOS and other bioaccumulative per- and polyfluoroalkyl substances (PFAS). Nonetheless, there are very few guidelines available for the protection of air-breathing wildlife. The Australian and New Zealand Guidelines for Fresh and Marine Water Quality provide Default Guideline Values (DGVs) for toxicants. These DGVs are based on traditional ecotoxicological tests that do not consider bioaccumulation. For chemicals known to bioaccumulate, the guidelines recommend a precautionary approach by applying the DGV that protects 99% of species. The PFAS National Environmental Management Plan (NEMP) provides Wildlife Diet Guidelines (WDGs) to protect mammals and birds that consume aquatic organisms. Other jurisdictions have developed Water Quality Criteria for the protection of wildlife via the use of dietary studies and combined with bioconcentration factors to back-calculate a safe concentration of PFOS in the water. As end users tend to use Water Quality Guidelines/Criteria as screening tools for further risk assessment, it is critically important to understand whether these PFOS guidelines effectively protect wildlife. In 2022-2023, water, sediment, and biota samples were collected over a year at eight sites in southeast Queensland, Australia. The dominant PFAS found in biota was PFOS, with the only other PFAS found in biota to be long-chain perfluorocarboxylic acids (PFCAs). Fifty percent of the sites had mean PFOS surface water concentrations that were below the draft Australian DGV, and yet all but one had biota concentrations that exceeded the NEMP WDGs. Bioaccumulation factors (BAFS) in fish were inversely related to concentrations of PFOS in water and showed a high variability within species and sites. Considering this, an interim field derived screening threshold is proposed for wildlife risk assessments.

Passive sampling in surface waters is an important method in the monitoring and risk assessment of hydrophobic and hydrophilic organic chemicals. Sampler designs can be optimized for fast equilibrium attainment (equilibrium sampling) or improved time-integrative capability (kinetic sampling). We argue that both equilibrium and kinetic sampling can be applied when aqueous concentrations do not vary with time, whereas kinetic sampling also yields useful results for time-variable concentrations that are often observed with hydrophilic compounds in surface waters. We show that these methods have similar accuracy in principle, but that their dominant error sources are different: sampler-water sorption coefficients for equilibrium sampling and sampling rates for kinetic sampling. In contrast to passive sampling of hydrophobic compounds, passive sampling of hydrophilic compounds is not as well-established, but major progress has been made over the last decade in the modeling of transport through the water boundary layer, membrane, and sorbent, while less progress has been made for transport in the biofouling layer. We recommend a more extensive use of diffusion cells as a research tool to gain a better understanding of transport through the respective subphases, leading to a greater maturity of passive water sampling of hydrophilic compounds.

Glyphosate is the most used herbicide globally, but little is known of its prevalence in the Australian environment or its behaviour during wastewater treatment. This study examined the concentration of glyphosate and its primary biodegradation product, aminomethylphosphonic acid (AMPA), in influent and effluent from 22 Australian wastewater treatment plants (WWTPs) to inform exposure risks. Glyphosate was detected in all 22 WWTP influent samples, with concentrations ranging from 0.37 to 370 μg/L (mean: 22 ± 76 μg/L). In treated effluent, glyphosate was found in 82 % of samples with concentrations ranging from <LOQ (0.2 μg/L) to 11 μg/L (mean: 2.1 ± 3.1 μg/L). AMPA was detected in the influent of four of the 22 WWTP, with concentrations ranging from <LOQ to 32 μg/L (mean: 1.4 ± 5.2 μg/L). AMPA was detected in the effluent samples at eleven sites, with concentrations ranging from <LOQ to 19 μg/L. Glyphosate removal efficiency varied by treatment process. Plants with tertiary treatment (n = 10) removed on average 76 % of the glyphosate, while primary treatment sites (n = 4) removed the lowest (mean: -102 %; higher in the effluent). One tertiary treatment site had glyphosate concentrations 160 % higher in the treated effluent, suggesting additional sources post treatment. The mean population weighted mass load of glyphosate in treated effluent was 572 ± 856 mg per day per 1000 inhabitants, with an estimated 5000 kg/year of glyphosate reaching the Australian aquatic environment. A temporal study at two influent sites identified increasing glyphosate use over the past decade. Despite the widespread presence of glyphosate in effluent, all concentrations were all below the current Australian freshwater species protection guideline of 180 μg/L.

Water reservoirs and lakes are gaining popularity for recreation activities as populations increase and green spaces become in high demand. However, these activities may cause contamination to critical water resources. This study investigates the impact of recreational activities on the presence and concentration of polycyclic aromatic hydrocarbons (PAHs) and ultraviolet (UV) filters in drinking water reservoirs in Southeast Queensland, Australia. Polydimethylsiloxane passive samplers were used to monitor 14 lakes over a 3-year period, focusing on seasonal variations and the influence of recreational activities such as petrol-powered boating and swimming. A total of 15 PAHs and six UV filters were detected, with chrysene (97%) and octyl salicylate (34%) being the most prevalent PAH and UV filter, respectively. Polycyclic aromatic hydrocarbon levels were statistically significantly higher in lakes permitting petrol-powered boating, especially during summer (p = 0.005 to 0.05). Lake Maroon and Lake Moogerah were the only sites that showed significantly higher PAH levels in summer (3.9 ± 1.1 and 4.0 ± 1.2 ng L-1, respectively) than winter (1.6 ± 0.61 and 1.5 ± 0.84, respectively). Ultraviolet filters were generally detected in higher levels in lakes allowing swimming, with Lake Moogerah and Lake Sommerset measuring UV filter concentrations of 20 ± 4.1 and 20 ± 11 ng L-1 in summer, respectively. Other lakes that do not permit swimming, such as Lake Maroon and Lake Samsonvale, also exhibited elevated UV filter levels, suggesting illegal swimming. These findings highlight the complexity of PAH and UV filter presence, influenced by multiple factors including lake size, recreational activity type, and seasonal variations. The levels of individual PAHs and UV filters in this study were below established freshwater guidelines. However, when considering their bioaccumulation potential and mixture toxicity, mitigating the impact of these substances on our environment and the organisms within it should be of priority.

Measuring dissolved concentrations of polybrominated diphenyl ethers (PBDEs) and non-BDE flame retardants on a global scale provides critical insights into the effectiveness of the Stockholm Convention. In the present study, we deployed passive sampling devices at 43 seawater and freshwater sites covering 21 countries from 2016 to 2020. The detection frequencies were 20-94% for BDE congeners and 33-42% for dechlorane plus, higher than those (0-20%) for other target compounds. The median concentrations of dissolved Σ9PBDE (sum of BDE-28, -47, -66, -85, -99, -100, -153, -154, and -183) were 0.28 and 0.64 pg L-1 in seawater and freshwater, respectively. The concentrations of dissolved Σ9PBDE, along with published data, slightly increased before 2016 and remained steady from 2016 to 2018, indicating delayed effects of the global phaseout of technical Penta- and Octa-BDEs. The log-transformed concentrations of individual BDE congeners were better correlated with regional gross domestic product than with population density. The potential ecological risk of BDE-47 was low, and there was a lack of key risk indicators for other compounds. The present study documented the delayed response of the aquatic environment to the regulatory actions on reducing PBDE emissions.

Humans may be exposed to thousands of per- and polyfluoroalkyl substances (PFAS), yet only a small fraction of these are regularly monitored, potentially underestimating the associated risks. This study employed high-resolution mass spectrometry (HRMS)-based nontarget analysis to investigate previously unreported PFAS in pooled serum from Australians. Samples collected between 2002 and 2021 from men aged > 30 years in the general population (GP, n = 27) and firefighters (FF, n = 18), categorized into three age groups (31-45, 46-60, and ≥ 60), were analyzed. Fourteen PFAS were identified or structurally annotated, including six known (level 1a-1b) and seven suspects (level 2b-3a). Additionally, six suspects with CHF2 or CF3 functionalities were tentatively annotated. Two previously unreported PFAS in human serum, hydrogen-substituted 2:1 perfluoroether sulfonic acid (2:1 H-PFESA) and hexafluoro-1,2-propanediol (HFPrD), were detected in 42% and 56% of samples, respectively. Further analysis of these two compounds in broader GP serum pools, including six age groups and both sexes, revealed their presence even in children under five, with relatively high intensities. No clear temporal, age, sex, or occupation-related trends were observed, suggesting widespread ongoing population exposure. These findings underscore the need for expanded HRMS-based monitoring to better assess human PFAS exposure.

Per- and polyfluoroalkyl substances (PFASs) are a class of synthetic organic chemicals of global concern. A group of 36 scientists and regulators from 18 countries held a hybrid workshop in 2022 in Zürich, Switzerland. The workshop, a sequel to a previous Zürich workshop held in 2017, deliberated on progress in the last five years and discussed further needs for cooperative scientific research and regulatory action on PFASs. This review reflects discussion and insights gained during and after this workshop and summarizes key signs of progress in science and policy, ongoing critical issues to be addressed, and possible ways forward. Some key take home messages include: 1) understanding of human health effects continues to develop dramatically, 2) regulatory guidelines continue to drop, 3) better understanding of emissions and contamination levels is needed in more parts of the world, 4) analytical methods, while improving, still only cover around 50 PFASs, and 5) discussions of how to group PFASs for regulation (including subgroupings) have gathered momentum with several jurisdictions proposing restricting a large proportion of PFAS uses. It was concluded that more multi-group exchanges are needed in the future and that there should be a greater diversity of participants at future workshops.

The potential of kinetic passive samplers to monitor per and polyfluoroalkyl substance (PFAS) concentrations in wastewater treatment plants (WWTPs) was evaluated using microporous polyethylene tube (MPT) passive samplers containing hydrophilic-lipophilic-balanced (HLB) or weak-anion-exchange (WAX) sorbents. Sampling rates (R-s) from 28 day deployments in WWTP effluent were consistent with principal resistance to PFAS accumulation in wastewater-filled micropores of the polyethylene tube. Considering both sorbents, PFAS R-s in the influent were smaller than in the effluent by a factor of 3.7, attributed to micropore clogging from a colloidal material but not biofilm formation. Combined Isolute ENV+ R-s values in the influent and effluent were 2.1 times larger than for Evolute WAX. Exploring their wider applicability, samplers with Sepra ZT-WAX were deployed in six other WWTPs with varying catchment characteristics. R-s values were significantly greater than those of Evolute WAX, indicating cationic charge center possession alone is an insufficient criterion for sorbent performance. Based on longer linear uptake timespans (e.g., >10(4) days for PFOA) and provision of time-weighted average concentrations, Evolute WAX was the best sorbent investigated. PFAS concentrations in wastewater derived from MPT samplers gave comparable accuracy to current grab sampling methods (i.e., EPA Method 1633). Findings demonstrate that MPT samplers are useful tools for monitoring PFAS in WWTPs.

Wastewater treatment plants (WWTPs) have been recognized as secondary sources of per- and polyfluoroalkyl substances (PFAS) release into the environment. In this study, PFAS concentrations were measured in effluent and biosolids samples collected from 75 WWTPs across Australia during the 2016 Census period, which covers more than half of the Australian population. Twelve PFAS compounds, including six C5-C10 perfluoroalkyl carboxylic acids (PFCAs), four perfluoro sulfonic acids (PFSAs) such as perfluorobutane sulfonate (PFBS), perfuorohexane sulfonic (PFHxS), perfluorooctane sulfonic acid (PFOS), and perfluorodecane sulfonic acid (PFDS), and one fluorotelomer sulfonic acid (6:2 FTS), were detected in the effluent, with concentrations up to 504ng/L (PFHxS). Among these, perfluorooctanoic acid (PFOA), perfluorohexanoic acid (PFHxA), and perfluoropentanic acid (PFPeA) exhibited the highest median concentrations. In the biosolids, a total of 21 PFAS compounds were detected, encompassing ten C4-C14 PFCAs, four PFSAs, two FTS (6:2 and 8:2 FTS), perfluorooctane sulfonamide (PFOSA), two perfluorooctane sulfonamido acetic acid (NMethyl FOSAA and NEthyl FOSAA), and two perfluorooctane sulfonamido ethanol (FOSE), with concentrations approaching 235ng/g.dry weight (dw) (PFOS). The highest median and mean concentrations were observed for perfluorodecanoic acid (PFDA) and PFOS. An annual discharge of approximately 250kg of the total 21 PFAS compounds was estimated through the effluent and biosolids of the participating WWTPs. Notably, PFOS and 6:2 FTS constituted the largest proportion of total PFAS in the WWTPs' output. While PFCAs were higher in effluent concentrations compared to influent levels across most WWTPs (92% of WWTPs for ∑8PFCAs), the concentrations of PFSAs either decreased or remained relatively stable (in 80% of WWTPs for ∑4PFSAs) throughout the wastewater treatment process.

Nontargeted screening (NTS) utilizing liquid chromatography electrospray ionization high-resolution mass spectrometry (LC/ESI/HRMS) is increasingly used to identify environmental contaminants. Major differences in the ionization efficiency of compounds in ESI/HRMS result in widely varying responses and complicate quantitative analysis. Despite an increasing number of methods for quantification without authentic standards in NTS, the approaches are evaluated on limited and diverse data sets with varying chemical coverage collected on different instruments, complicating an unbiased comparison. In this interlaboratory comparison, organized by the NORMAN Network, we evaluated the accuracy and performance variability of five quantification approaches across 41 NTS methods from 37 laboratories. Three approaches are based on surrogate standard quantification (parent-transformation product, structurally similar or close eluting) and two on predicted ionization efficiencies (RandFor-IE and MLR-IE). Shortly, HPLC grade water, tap water, and surface water spiked with 45 compounds at 2 concentration levels were analyzed together with 41 calibrants at 6 known concentrations by the laboratories using in-house NTS workflows. The accuracy of the approaches was evaluated by comparing the estimated and spiked concentrations across quantification approaches, instrumentation, and laboratories. The RandFor-IE approach performed best with a reported mean prediction error of 15x and over 83% of compounds quantified within 10x error. Despite different instrumentation and workflows, the performance was stable across laboratories and did not depend on the complexity of water matrices.

Pesticides are ubiquitous in the catchments of the Great Barrier Reef (GBR) and regularly discharge into the nearshore waters. Effective management of pesticides requires suitable water quality guideline values (WQGVs), and further ecotoxicological data for many pesticides are needed to improve the reliability of environmental risk assessments. To help address this issue, toxicity thresholds were determined to two species of tropical marine microalgae Tisochrysis lutea and Tetraselmis sp. for a suite of herbicides detected in the GBR. Photosystem II (PSII) herbicides significantly reduced growth with no effect concentration (NEC) and 10% effect concentration (EC10) values spanning two orders of magnitude from 0.60 µg L−1 for diuron to 60 µg L−1 for simazine across both species. However, growth was insensitive to the non-PSII herbicides. The NEC/EC10 thresholds for most herbicide-microalgae combinations were greater than recent WQGVs intended to protect 99% of species (PC99); however, metribuzin was toxic to T. lutea at concentrations lower than the current PC99 value, which may have to be revisited. The toxicity thresholds for alternative herbicides derived here further inform the development of national and GBR-specific WQGVs, but more toxicity data is needed to develop WQGVs for the > 50 additional pesticides detected in catchments of the GBR.

Non-target analysis (NTA) using high-resolution mass spectrometry is becoming a useful approach to screen for suspect and unknown chemicals. For comprehensive analyses, data-independent acquisition (DIA), like Sequential Windowed Acquisition of all THeoretical Mass Spectra (SWATH-MS) on Sciex instruments, is necessary, usually followed by library matching for feature annotation. The choice of parameters, such as acquisition window number and size, may influence the comprehensiveness of the suspect features detected. The goal of this study was to assess how mass spectrometric DIA settings may influence the ability to obtain confident annotations and identifications of features in environmental (river water, passive sample extract (PSE)), wastewater (unpreserved and acidified) and biological (urine) sample matrices. Each matrix was analysed using 11 different MS methods, with 5–15 variable size acquisition windows. True positive (TP) annotation (i.e., matching experimental and library spectra) rates were constant for PSE (40%) and highest for urine (18%), wastewater (34% and 36%, unpreserved and acidified, respectively) and river water (8%) when using higher numbers of windows (15). The number of annotated features was highest for PSE (12%) and urine (8.5%) when using more acquisition windows (9 and 14, respectively). Less complex matrices (based on average total ion chromatogram intensities) like river water, unpreserved and acidified wastewater have higher annotation rates (7.5%, 8% and 13.2%, respectively) when using less acquisition windows (5–6), indicating matrix dependency of optimum settings. Library scores varied widely for correct (scores between 6 and 100) as well as incorrect annotations (scores between 2 and 100), making it hard to define specific ideal cut-off values. Results highlight the need for properly curated libraries and careful optimization of SWATH-MS and other DIA methods for each individual matrix, finding the best ratio of total annotations to true positive, (i.e., correct) annotations to achieve best NTA results.

Microplastic surface properties are dynamic in the environment, as weathering, primarily through photooxidation due to ultraviolet light (UV) exposure, modifies surface chemistry and surface roughness, which can affect the fate, transport and reactivity of microplastics, and therefore any potential environmental risk they may pose. This study aims to investigate and characterise the effect of different UV radiation sources that are typically used in weathering studies (UVA-340 fluorescent lamps, xenon-arc lamps and natural sunlight) on two key properties of microplastics: surface roughness and oxidation level. High- and low-density polyethylene, polypropylene and polystyrene microplastic nurdles (<5 mm) were weathered and characterised using Atomic Force Microscopy and Fourier-Transform Infrared spectroscopy. After two weeks, UVA light was found to significantly increase the carbonyl index of the subject high-density polyethylene and decrease its surface roughness. The subject low-density polyethylene was found to increase in carbonyl index when exposed to all three light sources for two weeks, and reduced in surface roughness when exposed to both xenon-arc and UVA light. Xenon-arc light increased surface roughness on the subject polypropylene after two weeks exposure. The subject polystyrene significantly increased in carbonyl index when exposed to xenon-arc light for two weeks but decreased in surface roughness when exposed to UVA light. Surface oxidation was found to be dependent on polymer type, UV source and additive content, with the data showing a relationship between surface roughness, surface shading and additive content. The results from this study highlight the complexity of microplastic weathering processes and how metrics such as carbonyl index must be applied with caution when estimating how long a plastic has been in the environment.

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.

Monitoring contamination from per- and polyfluoroalkyl substances (PFASs) in water systems impacted by aqueous film-forming foams (AFFFs) typically addresses a few known PFAS groups. Given the diversity of PFASs present in AFFFs, current analytical approaches do not comprehensively address the range of PFASs present in these systems. A suspect-screening and nontarget analysis (NTA) approach was developed and applied to identify novel PFASs in groundwater samples contaminated from historic AFFF use. A total of 88 PFASs were identified in both passive samplers and grab samples, and these were dominated by sulfonate derivatives and sulfonamide-derived precursors. Several ultrashort-chain (USC) PFASs (≤C3) were detected, 11 reported for the first time in Australian groundwater. Several transformation products were identified, including perfluoroalkane sulfonamides (FASAs) and perfluoroalkane sulfinates (PFASis). Two new PFASs were reported (((perfluorohexyl)sulfonyl)sulfamic acid; m/z 477.9068 and (E)-1,1,2,2,3,3,4,5,6,7,8,8,8-tridecafluorooct-6-ene-1-sulfonic acid; m/z 424.9482). This study highlights that several PFASs are overlooked using standard target analysis, and therefore, the potential risk from all PFASs present is likely to be underestimated.

Ultrashort-chain per- and polyfluoroalkyl substances (PFASs) are an emerging class of contaminants that remain underexplored in environmental research. This study examines their distribution in Australian drinking tap water, environmental waters, and wastewaters (n = 63) using nontarget analysis via high-resolution mass spectrometry. Thirteen ultrashort-chain PFASs were identified, including novel compounds such as perfluoroalkane sulfinate (PFPSi), hydrogen-substituted perfluoroalkyl carboxylate (H-PFCA), chloro-perfluoroalkanesulfonate (Cl-PFSA), and bis-perfluoroalkyl sulfonamide (bis-FASIs). Perfluoropropanesulfonic acid (PFPrS) was the most prevalent, detected in 83% of surface, groundwater, and wastewater samples, and in 67% of tap water samples from major Australian cities. Concentrations of PFPrS and perfluoroethanesulfonic acid (PFEtS) ranged from <0.02 to 8000 ng/L. Ultrashort-chain perfluoroalkane sulfonamides (FASAs) and perfluoroalkane sulfates (PFA-OS) were predominantly found in wastewater. These findings highlight the widespread presence of ultrashort-chain PFASs in Australian water systems and underscore the need for ongoing monitoring and research due to their potential ecological and human health impacts. This study provides essential baseline data that could inform future regulatory measures and environmental management strategies.

Polycyclic aromatic hydrocarbons (PAHs), released from petrogenic, pyrogenic or diagenetic sources (degradation of wood materials), are of global concern due to their adverse effects, and potential for long-range transport. While dissolved PAHs have been frequently reported in the literature, there has been no consistent approach of sampling across water bodies. Passive samplers from the AQUA/GAPS-MONET initiative were deployed at 46 sites (28 marine and 18 freshwater), and analyzed for 28 PAHs and six polycyclic musks (PCMs) centrally. Freely dissolved PAH concentrations were dominated by phenanthrene (mean concentration 1500 pg L-1; median 530 pg L-1) and other low molecular weight compounds. Greatest concentrations of phenanthrene, fluoranthene, and pyrene were typically from the same sites, mostly in Europe and North America. Of the PCMs, only galaxolide (72% of samples) and tonalide (61%) were regularly detected, and were significantly cross-correlated. Benchmarking of PAHs relative to penta- and hexachlorobenzene confirmed that the most remote sites (Arctic, Antarctic, and mountain lakes) displayed below average PAH concentrations. Concentrations of 11 of 28 PAHs, galaxolide and tonalide were positively correlated (P < 0.05) with population density within a radius of 5 km of the sampling site. Characteristic PAH ratios gave conflicting results, likely reflecting multiple PAH sources and postemission changes.

The quality of chemical analysis is an important aspect of passive sampling-based environmental assessments. The present study reports on a proficiency testing program for the chemical analysis of hydrophobic organic compounds in silicone and low-density polyethylene (LDPE) passive samplers and hydrophilic compounds in polar organic chemical integrative samplers. The median between-laboratory coefficients of variation (CVs) of hydrophobic compound concentrations in the polymer phase were 33% (silicone) and 38% (LDPE), similar to the CVs obtained in four earlier rounds of this program. The median CV over all rounds was 32%. Much higher variabilities were observed for hydrophilic compound concentrations in the sorbent: 50% for the untransformed data and a factor of 1.6 after log transformation. Limiting the data to the best performing laboratories did not result in less variability. Data quality for hydrophilic compounds was only weakly related to the use of structurally identical internal standards and was unrelated to the choice of extraction solvent and extraction time. Standard deviations of the aqueous concentration estimates for hydrophobic compound sampling by the best performing laboratories were 0.21 log units for silicone and 0.27 log units for LDPE (factors of 1.6 to 1.9). The implications are that proficiency testing programs may give more realistic estimates of uncertainties in chemical analysis than within-laboratory quality control programs and that these high uncertainties should be taken into account in environmental assessments.

High-resolution mass spectrometry (HRMS) methods applying suspect screening and non-target analysis (NTA) approaches are becoming more commonly applied for the characterization of chemicals of emerging concern in a wide range of environmental and human matrices. They are particularly useful in extending our understanding of relevant contaminants by significantly expanding the range of chemicals we can assess beyond the limited target analysis and increasing representativeness of chemical exposure assessments. However, standardized methods for the application of HRMS-NTA approaches are not yet commonplace and large variability can exist between researchers and methods used. The typically extensive and information-rich datasets generated from these methods necessitate often elaborate strategies for processing and interpretation. Because of the complex datasets, challenges arise with ensuring reproducibility of results, especially if only considering quality control and assurance practices currently applied to target analytical methods. NTA requires a careful consideration of quality assurance and quality control (QA/QC) procedures and implementations across the analytical workflow (i.e., from sample collection and preparation through analysis and data acquisition to data processing and reporting). This chapter concerns the application of QA/QC strategies in NTA experiments and analysis and provides an overview of the fundamentals to be considered when considering NTA approaches. Rather than repeating some in-depth strategies that have already been highlighted in other works, this chapter summarizes the QA/QC steps to consider across the NTA workflow. A series of recommendations are highlighted, aiming at improving the standardization of quality assurance in NTA workflows.

The use of peak-picking algorithms is an essential step in all nontarget analysis (NTA) workflows. However, algorithm choice may influence reliability and reproducibility of results. Using a real-world data set, the aim of this study was to investigate how different peak-picking algorithms influence NTA results when exploring temporal and/or spatial trends. For this, drinking water catchment monitoring data, using passive samplers collected twice per year across Southeast Queensland, Australia (n = 18 sites) between 2014 and 2019, was investigated. Data were acquired using liquid chromatography coupled to high-resolution mass spectrometry. Peak picking was performed using five different programs/algorithms (SCIEX OS, MSDial, self-adjusting-feature-detection, two algorithms within MarkerView), keeping parameters identical whenever possible. The resulting feature lists revealed low overlap: 7.2% of features were picked by >3 algorithms, while 74% of features were only picked by a single algorithm. Trend evaluation of the data, using principal component analysis, showed significant variability between the approaches, with only one temporal and no spatial trend being identified by all algorithms. Manual evaluation of features of interest (p-value <0.01, log fold change >2) for one sampling site revealed high rates of incorrectly picked peaks (>70%) for three algorithms. Lower rates (<30%) were observed for the other algorithms, but with the caveat of not successfully picking all internal standards used as quality control. The choice is therefore currently between comprehensive and strict peak picking, either resulting in increased noise or missed peaks, respectively. Reproducibility of NTA results remains challenging when applied for regulatory frameworks.