High-Resolution Mass Spectrometry for Human Exposomics: Expanding Chemical Space Coverage

In the modern "omics" era, measurement of the human exposome is a critical missing link between genetic drivers and disease outcomes. High-resolution mass spectrometry (HRMS), routinely used in proteomics and metabolomics, has emerged as a leading technology to broadly profile chemical exposure agents and related biomolecules for accurate mass measurement, high sensitivity, rapid data acquisition, and increased resolution of chemical space. Non-targeted approaches are increasingly accessible, supporting a shift from conventional hypothesis-driven, quantitation-centric targeted analyses toward data-driven, hypothesis-generating chemical exposome-wide profiling. However, HRMS-based exposomics encounters unique challenges. New analytical and computational infrastructures are needed to expand the analysis coverage through streamlined, scalable, and harmonized workflows and data pipelines that permit longitudinal chemical exposome tracking, retrospective validation, and multi-omics integration for meaningful health-oriented inferences. In this article, we survey the literature on state-of-the-art HRMS-based technologies, review current analytical workflows and informatic pipelines, and provide an up-to-date reference on exposomic approaches for chemists, toxicologists, epidemiologists, care providers, and stakeholders in health sciences and medicine. We propose efforts to benchmark fit-for-purpose platforms for expanding coverage of chemical space, including gas/liquid chromatography-HRMS (GC-HRMS and LC-HRMS), and discuss opportunities, challenges, and strategies to advance the burgeoning field of the exposome

Changes in Flame Retardant and Legacy Contaminant Concentrations in Indoor Air during Building Construction, Furnishing, and Use

A newly constructed university building was selected for targeted assessment of changes in the levels of flame retardants and legacy contaminants during the installation of building equipment, furniture, electronics, and first year of building use. Indoor air samples were collected during several periods of intensive equipment installation to determine a relationship between newly introduced equipment and changes in the concentrations and profiles of contaminants in indoor air. Samples were analyzed for polybrominated diphenyl ethers (PBDEs), hexabromocyclododecanes (HBCDDs), and new types of flame retardants: brominated (BFRs) and organophosphate esters (OPEs). Additionally, typical outdoor contaminants such as polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were also analyzed for comparison. From the set of 90 compounds analyzed here, hexabromobenzene (HBB) and tris­(2-chloroisopropyl)­phosphate (TCIPP) showed a significant concentration increase in indoor air concentrations during computer installation and operation, suggesting emission by operating computers, while an order of magnitude concentration increase in tris­(1,3-dichloro-2-propyl)­phosphate (TDCIPP) and tri-m-cresyl phosphate (TMTP) was observed after the furniture and carpet was introduced to the computer room, suggesting furniture or carpet as a source. However, the majority of compounds had no systematic change in concentrations during equipment installation, indicating that no sources of target compounds were introduced or, that source introduction was not reflected in indoor air concentrations. Generally, low levels of legacy flame retardants compared to their novel alternatives were observed

Current Challenges in Air Sampling of Semivolatile Organic Contaminants: Sampling Artifacts and Their Influence on Data Comparability

With current science and policy needs, more attention is being given to expanding and improving air sampling of semivolatile organic contaminants (SVOCs). However, a wide range of techniques and configurations are currently used (active and passive samplers, different deployment times, different sorbents, etc.) and as the SVOC community looks to assess air measurements on a global scale, questions of comparability arise. We review current air sampling techniques, with a focus on sampling artifacts that can lead to uncertainties or biases in reported concentrations, in particular breakthrough, degradation, meteorological influences, and assumptions regarding passive sampling. From this assessment, we estimate the bias introduced for SVOC concentrations from all factors. Due to the effects of breakthrough, degradation, particle fractions and sampler uptake periods, some current passive and active sampler configurations may underestimate certain SVOCs by 30–95%. We then recommend future study design, appropriateness of sampler types for different study goals, and finally, how the SVOC community should move forward in both research and monitoring to best achieve comparability and consistency in air measurements

Passive Air Samplers As a Tool for Assessing Long-Term Trends in Atmospheric Concentrations of Semivolatile Organic Compounds

Many attempts have been made to quantify the relationship between the amount of persistent organic pollutants sequestered by passive air sampling devices and their actual concentrations in ambient air. However, this information may not be necessary for some applications. In this study, two sets of 30 ten-year-long time series of simultaneous passive and high-volume active air sampling carried out at the Košetice observatory in the Czech Republic were used for a comparison of temporal trends. Fifteen polyaromatic hydrocarbons, seven polychlorinated biphenyls and eight organochlorine pesticides were investigated. In most cases, a good agreement was observed between the trends derived from passive and active monitoring with the exception of several compounds obviously affected by sampling artifacts. Two sampling artifacts were observed: breakthrough of high-volume sampler filters for penta- and hexachlorobenzene and semiquantitative values for PAHs with a high molecular weight. It has been suggested before that annually aggregated results of passive air monitoring may be used directly for the assessment of the long-term behavior of these compounds. The extensive set of long-term data used in this study allowed us to confirm this finding and to demonstrate that it is also possible to derive temporal trends and the compounds’ half-lives in air from the passive-sampling time series

A Critical Review on the Opportunity to Use Placenta and Innovative Biomonitoring Methods to Characterize the Prenatal Chemical Exposome

Adverse effects associated with chemical exposures during pregnancy include several developmental and reproductive disorders. However, considering the tens of thousands of chemicals present on the market, the effects of chemical mixtures on the developing fetus is still likely underestimated. In this critical review, we discuss the potential to apply innovative biomonitoring methods using high-resolution mass spectrometry (HRMS) on placenta to improve the monitoring of chemical exposure during pregnancy. The physiology of the placenta and its relevance as a matrix for monitoring chemical exposures and their effects on fetal health is first outlined. We then identify several key parameters that require further investigations before placenta can be used for large-scale monitoring in a robust manner. Most critical is the need for standardization of placental sampling. Placenta is a highly heterogeneous organ, and knowledge of the intraplacenta variability of chemical composition is required to ensure unbiased and robust interindividual comparisons. Other important variables include the time of collection, the sex of the fetus, and mode of delivery. Finally, we discuss the first applications of HRMS methods on the placenta to decipher the chemical exposome and describe how the use of placenta can complement biofluids collected on the mother or the fetus

A Critical Review on the Opportunity to Use Placenta and Innovative Biomonitoring Methods to Characterize the Prenatal Chemical Exposome

Adverse effects associated with chemical exposures during pregnancy include several developmental and reproductive disorders. However, considering the tens of thousands of chemicals present on the market, the effects of chemical mixtures on the developing fetus is still likely underestimated. In this critical review, we discuss the potential to apply innovative biomonitoring methods using high-resolution mass spectrometry (HRMS) on placenta to improve the monitoring of chemical exposure during pregnancy. The physiology of the placenta and its relevance as a matrix for monitoring chemical exposures and their effects on fetal health is first outlined. We then identify several key parameters that require further investigations before placenta can be used for large-scale monitoring in a robust manner. Most critical is the need for standardization of placental sampling. Placenta is a highly heterogeneous organ, and knowledge of the intraplacenta variability of chemical composition is required to ensure unbiased and robust interindividual comparisons. Other important variables include the time of collection, the sex of the fetus, and mode of delivery. Finally, we discuss the first applications of HRMS methods on the placenta to decipher the chemical exposome and describe how the use of placenta can complement biofluids collected on the mother or the fetus

Particle Size Distribution of Halogenated Flame Retardants and Implications for Atmospheric Deposition and Transport

This study investigates the distribution of polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD) and a group of novel flame retardants (NFRs) on atmospheric aerosols. Two high volume cascade impactors were used to collect particulate fractions of ambient air over a one year period at urban and rural sites. The majority of FRs were found on the finest aerosols (<0.95 μm). Concentrations of HBCD were higher than those of ΣPBDEs. Moreover, we noted seasonality and spatial differences in particle size distributions, yet a large portion of the observed differences were due to differences in particulate matter (PM) itself. When normalized by PM, the size distributions of the FRs exhibited much greater heterogeneity. Differences existed between the FR distributions by molecular weight, with the higher molecular weight FRs (e.g., BDE-209, Dechlorane Plus) distributed more uniformly across all particulate size fractions. The seasonal, spatial, and compound-specific differences are of crucial importance when estimating dry and wet deposition of FRs as smaller aerosols have longer atmospheric residence times. Estimated wet and dry deposition of four representative FRs (BDE-47, BDE-209, HBCD, and Dechlorane Plus) using size-segregated aerosol data resulted in lower deposition estimates than when bulk aerosol data were used. This has implications for estimates of long-range atmospheric transport and atmospheric residence times, as it suggests that without size-specific distributions, these parameters could be underestimated for FRs