Multiple studies demonstrate mixture effects arising from the interactive toxicity of environmental chemicals in human blood, but identifying the main toxic drivers remains challenging. In a recent proof-of-principle in vitro study, we showed that personalized mixtures (PMs), reconstructed from 24 persistent organic pollutant (POPs) concentrations measured in individual blood samples from Swedish adults, induced unique interindividual effects on H295R cell viability and steroidogenesis. Here, we followed up by testing submixtures of four PMs (PM#3, PM#4, PC1-OC-Mix, and PC2-PFAS-Mix), separated by the chemical classes perfluoroalkyl substances (PFASs), organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs). Submixtures of PFAS and OCPs induced significant effects on testosterone synthesis at low (1×) and medium (10×) concentrations, consistent with effects observed in the corresponding whole PMs, and were therefore likely the primary drivers of the whole-mixture effects on testosterone. Notably, some submixtures altered estradiol and testosterone levels in ways not observed in full PMs, suggesting antagonistic interactions across chemical classes when combined. Potential antagonistic interaction in more complex mixtures, independent of concentration, was also observed within OCP submixtures, as only the less complex OCP mixtures lacking DDE or DDT induced testosterone synthesis. For additional mechanistic insight, we expanded the H295R assay to include oxidative stress analyses, which revealed no effects from the PMs. RT-qPCR analysis showed downregulation of CYP11A1 after exposure to PM#3 and PM#4 at high concentrations (100×), suggesting a feedback mechanism contributing to suppressed testosterone synthesis.

Toxicological studies of single chemicals overlook the real-world complexity of human exposure, where multiple compounds may interact to disrupt biological processes such as endocrine signaling. Moreover, the chemical exposome, the sum of an individual's chemical burden, varies markedly between people, yet its biological implications remain unclear. To address this gap, we reconstructed individualized human chemical exposomes to assess their effects on estrogen receptor (ER) activity. Sixteen exposomes comprising 24 persistent organic pollutant (POP) were derived from blood profiles of participants in the Swedish Västerbotten Intervention Programme. Using automated, non-contact acoustic liquid dispensing, we reconstructed 14 personalized mixtures (PMs) reflecting individual blood compositions and two formulated mixtures (FM) representing the cohort's median and maximum population exposure levels. ER activity was assessed in VM7Luc4E2 cells using a high-throughput 384-well adaption of the OECD No. 455 assay at 1×, 10× and 100× blood concentrations. While most individual POPs showed no or weak ER activity, three mixtures induced ER agonism. The PM-High, corresponding to the individual with the highest total POP levels, and the FM-Median activated the ER at 100×, while the FM-Maximum induced activation at 10× and 100×. Removing β-HCH and trans-nonachlor from the active mixtures abolished or reduced ER activity. Co-treatment with physiological estradiol levels increased ER responses in six mixtures, PM#1 (1× and 10×), PM#4 (100×), PM#8 (10×), PM#9 (100×), PM#10 (1×) and the FM-Median (1×), indicating potentiation of endogenous hormonal signaling. Overall, this study reveals endocrine activity in real-world POP mixtures and advances high-throughput screening as a scalable approach for individualized exposome-based health risk evaluation.

Polluted air is a major global health risk factor, yet the chemical composition and toxicity of airborne gases and particles remain underexplored due to their complexity and difficulties in sampling. We recently introduced how polydimethylsiloxane (PDMS) foam─or silicone foam─can be synthesized for passive air sampling, enabling simple and cost-effective nontarget chemical profiling of indoor air. Here, we demonstrate expanded applications, indoors and outdoors, with commercial PDMS-foam, including for: (i) wide-scope target analysis of >220 priority substances by quantitative liquid- and gas chromatography-high-resolution mass spectrometry, (ii) microscopic characterization and nontarget profiling of accumulated fine particles, and (iii) effect-guided discovery of harmful substances, combining toxicological data with nontarget analysis in silico. Median method quantification limits were 0.12 ng/mL, 90% of target analytes had absolute recoveries between 70 and 130%, and hazardous substances were discovered, including ethylene glycols, insecticides, and UV filters. Microscopy revealed the accumulation of abundant fine particles, and the automated characterization of the fluorescent fraction revealed that most were <4 μm. Extracts from outdoor samples reduced human lung cell viability, and multivariate modeling flagged families of potentially toxic substances in a virtual effect-directed analysis. PDMS-foam disks require field calibration to determine their linear sampling rate(s), but current results and applications establish PDMS-foam as a multimodal passive sampler, enabling integrated chemical quantitation, toxicological analysis, and molecular discovery in air.

In an analysis of the major scientific themes appearing in Environmental Science & Technology (ES&T) over its first 60 years, the exposome did not exactly stand out. (1) To be fair, the term has only existed since 2005 (2) and did not even appear in ES&T until 2011 when, then Editor-in-Chief, Jerold Schnoor enthusiastically embraced the topic and welcomed submissions. (3) Noting that the exposome was a measure of all exposures that an individual accrues in a lifetime, including to many environmental pollutants that had long been a focus of the journal, he warned that it will be “exceedingly difficult to measure due to extreme variability in space and time of a single individual’s exposure”. Notwithstanding his optimism that the scale of discoveries in exposomics could dramatically improve health, he was right that this was going to be hard.

Monitoring thousands of environmental chemicals in microliter blood volumes is now possible by chemical exposomics and high-resolution mass spectrometry (HRMS). As these technologies advance toward higher throughput to support human exposome studies with millions of participants, parallel implementation of higher-frequency blood collection methods must be considered to capture the highly dynamic nature of individual exposomes. Blood microsampling devices offer a less invasive way to collect quantitative, replicate, and repeated blood samples outside the clinic, overcoming limitations of traditional venepuncture and dried blood spots. Here we critically evaluate seven popular commercial microsampling devices for their potential use in chemical exposomics by considering previous use in molecular profiling, collection volumes, compatibility with various blood fractions, and conditions for shipping, storage, and analysis. We furthermore present the first data on extractable chemical interferences leaching from six of these devices in simulated blood sampling. Nontargeted HRMS revealed greatly different chemical backgrounds between devices, with implications for method sensitivity and false-positive discovery of exogenous and endogenous molecules. The unique advantages of each microsampler should be weighed against these chemical backgrounds, and in all cases, a systematic quality control program including field and simulated collection blanks is advised for future exposome studies utilizing these emerging devices.

Background: The chemical exposome includes exposure to numerous environmental and endogenous molecules, many of which have been linked to reproductive outcomes due to their endocrine-disrupting properties. As several breast cancer risk factors, including age and parity, are related to reproduction, it is imperative to investigate the interplay between such factors and the chemical exposome prior to conducting large scale exposome-based breast cancer studies.

Objective: This pilot study aimed to provide an overview of the chemical exposome in plasma samples from healthy women and identify associations between environmental exposures and three risk factors for breast cancer: age, parity, and age at menarche.

Material and methods: Plasma samples (n = 161), were selected based on reproductive history from 100 women participating in the Northern Sweden Health and Disease Study, between 1987 and 2006. Samples were analyzed by liquid chromatography high-resolution mass spectrometry (LC-HRMS) for 77 priority target analytes including contaminants and hormones, with simultaneous untargeted profiling of the chemical exposome and metabolome. Linear mixed effects models were applied to test associations between risk factors and chemical levels.

Results: Fifty-five target analytes were detected in at least one individual and over 94,000 untargeted features were detected across all samples. Among untargeted features, 430 could be annotated and were broadly classified as environmental (246), endogenous (167) or ambiguous (17). Applying mixed effect models to features detected in at least 70% of the samples (16,778), we found seven targeted analytes (including caffeine and various per- and poly-fluoroalkyl substances) and 38 untargeted features, positively associated with age. The directionality of these associations reversed for parity, decreasing with increasing births. Seven separate targeted analytes were associated with age at menarche.

Significance: This study demonstrates how a comprehensive chemical exposome approach can be used to inform future research prioritization regarding associations between known and unknown substances, reproduction, and breast cancer risk.

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.

The complex and dynamic nature of airborne fine particulate matter (PM2.5) has hindered understanding of its chemical composition, sources, and toxic effects. In the first steps of a larger study, here, we aimed to elucidate relationships between source regions, ambient conditions, and the chemical composition in water extracts of PM2.5 samples (n = 85) collected over 16 months at an observatory in the Yellow Sea. In each extract, we quantified elements and major ions and profiled the complex mixtures of organic compounds by nontarget mass spectrometry. More than 50,000 nontarget features were detected, and by consensus of in silico tools, we assigned a molecular formula to 13,907 features. Oxygenated compounds were most prominent, followed by mixed nitrogenated/oxygenated compounds, organic sulfates, and sulfonates. Spectral matching enabled identification or structural annotation of 43 substances, and a workflow involving SIRIUS and MS-DIAL software enabled annotation of 74 unknown per- and polyfluoroalkyl substances with primary source regions in China and the Korean Peninsula. Multivariate modeling revealed seasonal variations in chemistry, attributable to the combination of warmer temperatures and maritime source regions in summer and to cooler temperatures and source regions of China in winter.

Cetaceans face numerous anthropogenic chemical stressors in global oceans, yet there is a lack of studies that simultaneously assess their cumulative exposure to both legacy and emerging contaminants and their combined effects. To evaluate the susceptibility of fin whale (Balaenoptera physalus) to chemical pollution, this study employed for the first time a multidiagnostic molecular approach that integrates chemical exposomics and gene expression analysis in live-sampled skin and blubber biopsies from two distinct populations: the endangered Mediterranean subpopulation (Italy) and the vulnerable population from the Sea of Cortez (Mexico). Both marine regions are biodiversity hotspots characterized by different anthropogenic impacts, making them ideal for the assessment of heterogeneous contaminants exposure and their effects. Results revealed distinct exposure profiles in the two populations, with Mediterranean fin whales exhibiting higher concentrations of legacy pollutants such as polychlorinated biphenyls (PCBs), as well as plasticizers, perfluoroalkyl substances (PFAS), while both populations showed traces of pharmaceuticals and lifestyle-related chemicals (e.g., paracetamol, diclofenac, nicotine, UV filters) and other substances not previously reported in whales. Supported by 32 network correlations with gene expression relevant to transcriptional regulation, endocrine disruption, lipid homeostasis, and inflammation, our findings suggest that complex anthropogenic chemical exposures may compromise the health and reproductive viability of the endangered Mediterranean fin whales, affirming their importance as a global sentinel species, which reflects marine ecosystem integrity within the “One Health” framework.

Hydraulic fracturing flowback and produced water (HF-FPW) has raised significant concerns owing to its potential impact on aquatic organisms and human health. Understanding the chemical composition of HF-FPW is crucial for developing appropriate management and remediation strategies. Herein, we performed nontarget screening on hydrophobic organic chemicals in the particulate phase of FPW (P-FPW) using gas chromatography-Orbitrap mass spectrometry coupled with cheminformatic analysis. In total, 5807 features were discovered, with 209 annotated with positive confidence levels, which were further classified based on their chemical taxonomy and functional use information. We found that benzenoids dominated the chemical class, followed by hydrocarbons. The annotated chemicals were classified into fragrances, catalysts, antimicrobials, antioxidants, and other classes. Chemical overlap across countries (China vs. Canada) and wells was observed, with most chemicals reaching peak intensity within 24 or 48 h after the initial flowback and gradually decreasing. Approximately two-thirds of the identified or annotated chemicals have not been previously reported or included in existing HF-related databases, indicating expanded chemical coverage by the current screening workflow. A Toxicological Priority Index (ToxPi) scheme, which integrates chemical properties, ecological toxicities, and in vivo exposure potentials, was adopted to prioritize chemicals for further evaluation. Seven chemicals were proposed as prioritized compounds, of which the ester derivative of perfluorobutanoic acid, octacosyl heptafluorobutyrate (confidence level 2), exhibited the highest ToxPi score. Notably, most prioritized substances have limited toxicological data and are beyond the routine monitoring of the HF industry, highlighting significant gaps in our understanding of HF-related chemical content and environmental risk associated with water management.