Polydimethylsiloxane (silicone rubber) brooch as a personal passive air sampler for semi-volatile organic compounds

Chemical uptake into silicone wristbands over a five day period

Silicone wristbands are a noninvasive personal exposure assessment tool. However, despite their utility, questions remain about the rate at which chemicals accumulate on wristbands when worn, as validation studies utilizing wristbands worn by human participants are limited. This study evaluated the chemical uptake rates of 113 organic pollutants from several chemical classes (i.e., polychlorinated biphenyls (PCB), organophosphate esters (OPEs), alkyl OPEs, polybrominated diphenyl ethers (PBDEs), brominated flame retardants (BFR), phthalates, pesticides, and polycyclic aromatic hydrocarbons (PAHs) over a five-day period. Adult participants (n = 10) were asked to wear five silicone wristbands and then remove one wristband each day. Several compounds were detected in all participants' wristbands after only one day. The number of chemicals detected frequently (i.e. in at least seven participants wristbands) increased from 20% of target compounds to 26% after three days and more substantially increased to 34% of target compounds after four days of wear. Chemicals detected in at least seven participants' day five wristbands (n = 24 chemicals) underwent further statistical analysis, including estimating the chemical uptake rates over time. Some chemicals, including pesticides and phthalates, had postive and significant correlations between concentrations on wristbands worn five days and concentrations of wristbands worn fewer days suggesting chronic exposure. For 23 of the 24 compounds evaluated there was a statistically significant and positive linear association between the length of time wristbands were worn and chemical concentrations in wristbands. Despite the differences that exist between laboratory studies using polydimethylsiloxane (PDMS) environmental samplers and worn wristbands, these results indicate that worn wristbands are primarily acting as first-order kinetic samplers. These results suggest that studies using different deployment lengths should be comparable when results are normalized to the length of the deployment period. In addition, a shorter deployment period could be utilized for compounds that were commonly detected in as little as one day.

Longitudinal Mapping of Personal Biotic and Abiotic Exposomes and Transcriptome in Underwater Confined Space Using Wearable Passive Samplers

Silicone-based passive samplers, commonly paired with gas chromatography-mass spectrometry (GC-MS) analysis, are increasingly utilized for personal exposure assessments. However, its compatibility with the biotic exposome remains underexplored. In this study, we introduce the wearable silicone-based AirPie passive sampler, coupled with nontargeted liquid chromatography with high-resolution tandem mass spectrometry (LC-HRMS/MS), GC-HRMS, and metagenomic shotgun sequencing methods, offering a comprehensive view of personalized airborne biotic and abiotic exposomes. We applied the AirPie samplers to 19 participants in a unique deep underwater confined environment, annotating 4,390 chemical and 2,955 microbial exposures, integrated with corresponding transcriptomic data. We observed significant shifts in environmental exposure and gene expression upon entering this unique environment. We noted increased exposure to pollutants, such as benzenoids, polycyclic aromatic hydrocarbons (PAHs), opportunistic pathogens, and associated antibiotic-resistance genes (ARGs). Transcriptomic analyses revealed the activation of neurodegenerative disease-related pathways, mostly related to chemical exposure, and the repression of immune-related pathways, linked to both biological and chemical exposures. In summary, we provided a comprehensive, longitudinal exposome map of the unique environment and underscored the intricate linkages between external exposures and human health. We believe that the AirPie sampler and associated analytical methods will have broad applications in exposome and precision medicine.

Wearable Passive Samplers for Assessing Environmental Exposure to Organic Chemicals: Current Approaches and Future Directions

PURPOSE OF REVIEW

We are continuously exposed to dynamic mixtures of airborne contaminants that vary by location. Understanding the compositional diversity of these complex mixtures and the levels to which we are each exposed requires comprehensive exposure assessment. This comprehensive analysis is often lacking in population-based studies due to logistic and analytical challenges associated with traditional measurement approaches involving active air sampling and chemical-by-chemical analysis. The objective of this review is to provide an overview of wearable passive samplers as alternative tools to active samplers in environmental health research. The review highlights the advances and challenges in using wearable passive samplers for assessing personal exposure to organic chemicals and further presents a framework to enable quantitative measurements of exposure and expanded use of this monitoring approach to the population scale.

RECENT FINDINGS

Overall, wearable passive samplers are promising tools for assessing personal exposure to environmental contaminants, evident by the increased adoption and use of silicone-based devices in recent years. When combined with high throughput chemical analysis, these exposure assessment tools present opportunities for advancing our ability to assess personal exposures to complex mixtures. Most designs of wearable passive samplers used for assessing exposure to semi-volatile organic chemicals are currently uncalibrated, thus, are mostly used for qualitative research. The challenge with using wearable samplers for quantitative exposure assessment mostly lies with the inherent complexity in calibrating these wearable devices. Questions remain regarding how they perform under various conditions and the uncertainty of exposure estimates. As popularity of these samplers grows, it is critical to understand the uptake kinetics of chemicals and the different environmental and meteorological conditions that can introduce variability. Wearable passive samplers enable evaluation of exposure to hundreds of chemicals. The review presents the state-of-the-art of technology for assessing personal exposure to environmental chemicals. As more studies calibrate wearable samplers, these tools present promise for quantitatively assessing exposure at both the individual and population levels.

Hormone receptor activities of complex mixtures of known and suspect chemicals in personal silicone wristband samplers worn in office buildings

Humans are exposed to increasingly complex mixtures of hormone-disrupting chemicals from a variety of sources, yet, traditional research methods only evaluate a small number of chemicals at a time. We aimed to advance novel methods to investigate exposures to complex chemical mixtures. Silicone wristbands were worn by 243 office workers in the USA, UK, China, and India during four work shifts. We analyzed extracts of the wristbands for: 1) 99 known (targeted) chemicals; 2) 1000+ unknown chemical features, tentatively identified through suspect screening; and 3) total hormonal activities towards estrogen (ER), androgen (AR), and thyroid hormone (TR) receptors in human cell assays. We evaluated associations of chemicals with hormonal activities using Bayesian kernel machine regression models, separately for targeted versus suspect chemicals (with detection ≥50%). Every wristband exhibited hormonal activity towards at least one receptor: 99% antagonized TR, 96% antagonized AR, and 58% agonized ER. Compared to men, women were exposed to mixtures that were more estrogenic (180% higher, adjusted for country, age, and skin oil abundance in wristband), anti-androgenic (110% higher), and complex (median 836 detected chemical features versus 780). Adjusted models showed strong associations of jointly increasing chemical concentrations with higher hormonal activities. Several targeted and suspect chemicals were important co-drivers of overall mixture effects, including chemicals used as plasticizers, fragrance, sunscreen, pesticides, and from other or unknown sources. This study highlights the role of personal care products and building microenvironments in hormone-disrupting exposures, and the substantial contribution of chemicals not often identifiable or well-understood to those exposures.

Silicone wristbands as personal passive sampling devices: Current knowledge, recommendations for use, and future directions

Personal chemical exposure assessment is necessary to determine the frequency and magnitude of individual chemical exposures, especially since chemicals present in everyday environments may lead to adverse health outcomes. In the last decade, silicone wristbands have emerged as a new chemical exposure assessment tool and have since been utilized for assessing personal exposure to a wide range of chemicals in a variety of populations. Silicone wristbands can be powerful tools for quantifying personal exposure to chemical mixtures in a single sample, associating exposure with health outcomes, and potentially overcoming some of the challenges associated with quantifying the chemical exposome. However, as their popularity grows, it is crucial that they are used in the appropriate context and within the limits of the technology. This review serves as a guide for researchers interested in utilizing silicone wristbands as a personal exposure assessment tool. Along with briefly discussing the passive sampling theory behind silicone wristbands, this review performs an in-depth comparison of wristbands to other common exposure assessment tools, including biomarkers of exposure measured in biospecimens, and evaluates their utility in exposure assessments and epidemiological studies. Finally, this review includes recommendations for utilizing silicone wristbands to evaluate personal chemical exposure and provides suggestions on what research is needed to recognize silicone wristbands as a premier chemical exposure assessment tool.

Silicone wristbands as personal passive samplers of exposure to polychlorinated biphenyls in contaminated buildings

Polychlorinated biphenyls (PCBs) were used in a number of industrial products from 1950 to 80s, including building materials. As a result, some buildings exhibit high levels of PCBs in the indoor environment. The aim of this study was to test silicone wristbands as a method for estimating personal exposure to PCBs in buildings both in controlled experiments and field settings. In the controlled study, the sampling kinetics of silicone wristbands were investigated in a 31-day uptake study. The field study focused on the application of wristbands as a personal exposure measure. It included 71 persons in a contaminated housing estate and 23 persons in a reference group. The linear uptake of PCBs ranged from 2 to 24 days for PCB-8, 18, 28, 31, 40, 44, 49, 52, 66, 99, and 101 under controlled conditions. A generic sampling rate (R_k) of 2.3 m³ d^-1 corresponding to a mass transfer coefficient of 17 m h^-1 was found in the controlled kinetic study. Partitioning coefficients were also determined for the nine congeners. In the field study, an apparent generic field sampling rate (R_f) of 2.6 m³ d^-1 was found; when adjusted to reported hours exposed, it increased to 3.5 m³ d^-1. The wristbands were shown to be a good tool for predicting airborne exposure, as there was a highly significant difference between the exposed and reference group as well as a clear trend when used for ranking of exposure. In correlation analyses, highly significant correlations were observed between air and wristband levels, though adjusting by self-reported exposure time only increased the correlation marginally in the field study. The obtained kinetic data can be used for estimating the magnitude of external exposure. The advantages provided by the wristbands in the form of easy use and handling are significant, though the limitations should also be acknowledged.

Characterizing the external exposome using passive samplers-comparative assessment of chemical exposures using different wearable form factors

BACKGROUND

Organic contaminants are released into the air from building materials/furnishings, personal care, and household products. Wearable passive samplers have emerged as tools to characterize personal chemical exposures. The optimal placement of these samplers on an individual to best capture airborne exposures has yet to be evaluated.

OBJECTIVE

To compare personal exposure to airborne contaminants detected using wearable passive air samplers placed at different positions on the body.

METHODS

Participants (n = 32) simultaneously wore four passive Fresh Air samplers, on their head, chest, wrist, and foot for 24 hours. Exposure to 56 airborne organic contaminants was evaluated using thermal desorption gas chromatography high resolution mass spectrometry with a targeted data analysis approach.

RESULTS

Distinct exposure patterns were detected by samplers positioned on different parts of the body. Chest and wrist samplers were the most similar with correlations identified for 20% of chemical exposures (Spearman's Rho > 0.8, p < 0.05). In contrast, the greatest differences were found for head and foot samplers with the weakest correlations across evaluated exposures (8% compounds, Spearman's Rho > 0.8, p < 0.05).

SIGNIFICANCE

The placement of wearable passive air samplers influences the exposures captured and should be considered in future exposure and epidemiological studies.

IMPACT STATEMENT

Traditional approaches for assessing personal exposure to airborne contaminants with active samplers presents challenges due to their cost, size, and weight. Wearable passive samplers have recently emerged as a non-invasive, lower cost tool for measuring environmental exposures. While these samplers can be worn on different parts of the body, their position can influence the type of exposure that is captured. This study comprehensively evaluates the exposure to airborne chemical contaminants measured at different passive sampler positions worn on the head, chest, wrist, and foot. Findings provide guidance on sampler placement based on chemicals and emission sources of interest.

Chemical and biological assessments of environmental mixtures: A review of current trends, advances, and future perspectives

Considering the chemical complexity and toxicity data gaps of environmental mixtures, most studies evaluate the chemical risk individually. However, humans are usually exposed to a cocktail of chemicals in real life. Mixture health assessment remains to be a research area having significant knowledge gaps. Characterization of chemical composition and bioactivity/toxicity are the two critical aspects of mixture health assessments. This review seeks to introduce the recent progress and tools for the chemical and biological characterization of environmental mixtures. The state-of-the-art techniques include the sampling, extraction, rapid detection methods, and the in vitro, in vivo, and in silico approaches to generate the toxicity data of an environmental mixture. Application of these novel methods, or new approach methodologies (NAMs), has increased the throughput of generating chemical and toxicity data for mixtures and thus refined the mixture health assessment. Combined with computational methods, the chemical and biological information would shed light on identifying the bioactive/toxic components in an environmental mixture.

Occupational Exposure of Canadian Nail Salon Workers to Plasticizers Including Phthalates and Organophosphate Esters

Personal exposure of nail salon workers to 10 phthalates and 19 organophosphate esters (OPEs) was assessed in 18 nail salons in Toronto, Canada. Active air samplers (n = 60) and silicone passive samplers, including brooches (n = 58) and wristbands (n = 60), were worn by 45 nail salon workers for ∼8 working hours. Diethyl phthalate (median = 471 ng m^-3) and diisobutyl phthalate (337 ng m^-3) were highest in active air samplers. Most abundant OPEs in active air samplers were tris(2-chloroisopropyl)phosphate or TCIPP (303 ng m^-3) and tris(2-chloroethyl)phosphate or TCEP (139 ng m^-3), which are used as flame retardants but have not been reported for use in personal care products or nail salon accessories. Air concentrations of phthalates and OPEs were not associated with the number of services performed during each worker's shift. Within a single work shift, a combined total of 16 (55%) phthalates and OPEs were detected on passive silicone brooches; 19 (66%) were detected on wristbands. Levels of tris(2-chloroisopropyl)phosphate, tris(1,3-dichloro-2-propyl)phosphate or TDCIPP, and triphenyl phosphate or TPhP wristbands were significantly higher than those worn by e-waste workers. Significant correlations (p < 0.05) were found between the levels of some phthalates and OPEs in silicone brooches and wristbands versus those in active air samplers. Stronger correlations were observed between active air samplers versus brooches than wristbands. Sampler characteristics, personal characteristics, and chemical emission sources are the three main factors proposed to influence the use of passive samplers for measuring semi-volatile organic compound exposure.

A systematic review of the use of silicone wristbands for environmental exposure assessment, with a focus on polycyclic aromatic hydrocarbons (PAHs)

BACKGROUND

Exposure assessment is critical for connecting environmental pollutants to health outcomes and evaluating impacts of interventions or environmental policies. Silicone wristbands (SWBs) show promise for multi-pollutant exposure assessment, including polycyclic aromatic hydrocarbons (PAHs), a ubiquitous class of toxic environmental pollutants.

OBJECTIVE

To review published studies where SWBs were worn on the wrist for human environmental exposure assessments and evaluate the ability of SWBs to capture personal exposures, identify gaps which need to be addressed to implement this tool, and make recommendations for future studies to advance the field of exposure science through utilization of SWBs.

METHODS

We performed a systematic search and a cited reference search in Scopus and extracted key study descriptions.

RESULTS

Thirty-nine unique studies were identified, with analytes including PAHs, pesticides, flame retardants, and tobacco products. SWBs were shipped under ambient conditions without apparent analyte loss, indicating utility for global exposure and health studies. Nineteen articles detected a total of 60 PAHs in at least one SWB. Correlations with other concurrent biological and air measurements indicate the SWB captures exposure to flame retardants, tobacco products, and PAHs.

SIGNIFICANCE

SWBs show promise as a simple-to-deploy tool to estimate environmental and occupational exposures to chemical mixtures, including PAHs.

Operationalizing the Exposome Using Passive Silicone Samplers

The exposome, which is defined as the cumulative effect of environmental exposures and corresponding biological responses, aims to provide a comprehensive measure for evaluating non-genetic causes of disease. Operationalization of the exposome for environmental health and precision medicine has been limited by the lack of a universal approach for characterizing complex exposures, particularly as they vary temporally and geographically. To overcome these challenges, passive sampling devices (PSDs) provide a key measurement strategy for deep exposome phenotyping, which aims to provide comprehensive chemical assessment using untargeted high-resolution mass spectrometry for exposome-wide association studies. To highlight the advantages of silicone PSDs, we review their use in population studies and evaluate the broad range of applications and chemical classes characterized using these samplers. We assess key aspects of incorporating PSDs within observational studies, including the need to preclean samplers prior to use to remove impurities that interfere with compound detection, analytical considerations, and cost. We close with strategies on how to incorporate measures of the external exposome using PSDs, and their advantages for reducing variability in exposure measures and providing a more thorough accounting of the exposome. Continued development and application of silicone PSDs will facilitate greater understanding of how environmental exposures drive disease risk, while providing a feasible strategy for incorporating untargeted, high-resolution characterization of the external exposome in human studies.

Preservation of vapor samples on adsorbent alumina capillaries and implications for field sampling

Dynamic vapor microextraction (DVME) is a vapor preconcentration method that employs a capillary trap coated with an adsorbent, followed by solvent elution to recover the sample. DVME has been developed for applications in the laboratory, including highly precise vapor pressure measurements, and in the field. When vapor collection is conducted outside the laboratory, samples must almost always undergo some interval of storage representing the time between collection and analysis. This interval may be hours, days, or longer, depending on the situation. Regardless, in all situations there must be confidence that the integrity of the samples is maintained until processing and analysis. In this paper, we present results of two studies that tested the stability of a 50% weathered gasoline headspace sample on alumina PLOT (porous layer open tubular) capillaries stored at room temperature for periods from 24 h up to 20 wk. We used principal component analysis (PCA) to reduce the dimensionality of the chromatographic and mass spectral data and elucidate trends in stability with respect to the complex sample's range of hydrocarbon classes and molecular weights. Both analyses identified changes over storage periods of six weeks or more. The hydrocarbon class analysis, which used selected ion monitoring (SIM) data as input, proved more sensitive to changes over shorter storage periods. Sample integrity was preserved for at least 24 h, but losses, especially of high-volatility compounds, occurred by 168 h (7 d). Near total loss of sample occurred by 20 wk. These findings, which are specific to the sample, adsorbent, and storage conditions, will guide choices in experimental and instrumental design to ensure that data from future field studies is reliable.

Calibration of silicone for passive sampling of semivolatile organic contaminants in indoor air

Semivolatile organic compounds (SVOCs) are mostly man-made chemicals that distribute between the gas and solid phase in the environment. Many of them could pose harm to people and therefore it is important to know their concentrations in the indoor environment to evaluate the related risks. Inhalation exposure can be assessed using passive sampling. In this study, we employed silicone elastomer as a passive sampler for monitoring gaseous polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and polybrominated diphenyl ethers (PBDEs) in indoor air. We performed a sampler calibration study in which samplers consisting of 0.5 mm thick silicone sheets with a total surface area of 300 cm² were exposed to indoor air in a university lecture theatre for up to 56 days. Uptake kinetics of SVOCs was studied by collecting 2 samplers every week. The results were used to develop a model based on mass transfer theory that can be used to estimate the air sampling rate R_S as a function of compound's molecular volume. We examined release kinetics of performance reference compounds that covered a broad range of silicone-air partition coefficient (log K_SA 5.95-9.49) and investigated a hypothesis of isotropic exchange kinetics, i.e. equality of rate constants for uptake and release, of SVOCs. PCBs and OCPs concentration in air calculated from contaminant amounts accumulated in passive samplers were in good agreement with those determined by active sampling running simultaneously during the entire study. The use of performance reference compounds is suitable for in situ passive sampler calibration.

Mobility and environmental monitoring of pesticides in the atmosphere - a review

Knowledge of the partition mechanisms in the agrochemical environment is fundamental for understanding their behavior within an ecosystem and mitigating possible adverse effects of these products. In this review, the objective was to present the main transport mechanisms, physical-chemical properties, and atmospheric monitoring methodologies of the most diverse types of agrochemicals used in agriculture that can reach the atmosphere and affect different compartments. It has been verified that volatilization is one of more considerable significance of the various forms of transport since a significant part of the applied pesticides can volatilize in a few days. As for monitoring these compounds in the atmosphere, both passive and active sampling have their advantages and disadvantages. Passive samplers allow sampling in large quantities and at remote locations, in addition to making continuous measurements, while active samplers have the advantage of being able to detect low concentrations and continuously. Since a significant portion of the applied pesticides is directed to the atmosphere, monitoring makes it possible to understand some properties of the pesticides present in the air. This monitoring can be done from different existing methodologies based on adopted criteria and existing technical standards. Graphical representation of mobility and environmental monitoring of atmospheric pollutants from pesticides.

Head, Shoulders, Knees, and Toes: Placement of Wearable Passive Samplers Alters Exposure Profiles Observed

Chemical exposures are a major risk factor for many diseases. Comprehensive characterization of personal exposures is necessary to highlight chemicals of concern and factors that influence these chemical exposure dynamics. For this purpose, wearable passive samplers can be applied to assess longitudinal personal exposures to airborne contaminants. Questions remain regarding the impact of sampler placement at different locations of the body on the exposure profiles observed and how these placements affect the monitoring of seasonal dynamics in exposures. This study assessed personal air contaminant exposure using passive samplers worn in parallel across 32 participant's wrists, chest, and shoes over 24 h. Samplers were analyzed by thermal desorption gas chromatography high-resolution mass spectrometry. Personal exposure profiles were similar for about one-third of the 275 identified chemicals, irrespective of sampler placement. Signals of certain semivolatile organic compounds (SVOCs) were enhanced in shoes and, to a lesser extent, wrist samplers, as compared to those in chest samplers. Signals of volatile organic compounds were less impacted by sampler placement. Results showed that chest samplers predominantly captured more volatile exposures, as compared to those of particle-bound exposures, which may indicate predominant monitoring of chemicals via the inhalation route of exposure for chest samplers. In contrast, shoe samplers were more sensitive to particle-bound SVOCs. Seventy-one chemicals changed across participants between winter and summer in the same manner for two or more different sampler placements on the body, whereas 122 chemicals were observed to have seasonal differences in only one placement. Hence, the placement in certain cases significantly impacts exposure dynamics observed. This work shows that it is essential in epidemiological studies undertaking exposure assessment to consider the consequence of the placement of exposure monitors.

Development of a personal passive air sampler for estimating exposure to effective chlorine while using chlorine-based disinfectants

With an increasing use of indoor disinfectants such as chlorine (Cl₂ ) and hypochlorous acid, a convenient sampler for estimating exposure to oxidants, such as effective chlorine, is necessary. Here, we developed a personal passive air sampler (PPAS) composed of a redox dye, o-dianisidine, in a polydimethylsiloxane (PDMS) sheet. o-Dianisidine readily reacts with gaseous oxidants generated by bleach usage, and its color changes as the reaction progresses; hence, personal exposure to effective chlorine could be easily detected by the naked eye, while cumulative exposure could be determined by measuring concentrations of o-dianisidine reacting with it. The PPAS was calibrated, and a sampling rate of 0.00253 m³ /h was obtained using a small test chamber. The PPAS was tested with the help of ten volunteers whose personal exposure to Cl₂ -equivalent gas was estimated after bathrooms were cleaned using spray and liquid-type household disinfection products, and the accumulated exposure-gas concentrations ranged from 69 to 408 ppbv and 148 to 435 ppbv, respectively. These PPAS-derived exposure concentrations were approximately two orders lower than those estimated using ConsExpo, suggesting a significant overestimation by prevailing screening models, possibly due to the ignorance of transformation reactions.

A review of organophosphate esters in indoor dust, air, hand wipes and silicone wristbands: Implications for human exposure

The ubiquity of organophosphate esters (OPEs) in various environmental matrices inevitably pose human exposure risks. Numerous studies have investigated human exposure pathways to OPEs, including air inhalation, dust ingestion, dermal contact, and dietary and drinking water intake, and have indicated that indoor dust and indoor air routes are frequently the two main human exposure pathways. This article reviews the literature on OPE contamination in indoor air and dust from various microenvironments and on OPE particle size distributions and bioavailability in dust conducted over the past 10 years. Ways in which sampling strategies are related to the uncertainty of exposure assessment results and comparability among different studies in terms of sampling tools, sampling sites, and sample types are addressed. Also, the associations of OPEs in indoor dust/air with human biological samples were summarized. Studies on two emerging matrices, hand wipes and silicone wristbands, are demonstrated to be more comprehensive and accurate in reflecting personal human exposure to OPEs in microenvironments and are summarized. Given the direct application of some diester OPEs (di-OPEs) in numerous products, research on their existence in indoor dust and food and on their effects on human urine are also discussed. Finally, related research trends and avenues for future research are prospected.

Can Silicone Passive Samplers be Used for Measuring Exposure of e-Waste Workers to Flame Retardants?

Silicone passive samplers were assessed for measuring personal exposure to 37 flame retardants at three Québec e-waste recycling facilities. Silicone brooches (n = 45), wristbands (n = 28), and armbands (n = 9) worn during a ∼8 h work shift accumulated detectable amounts of 95-100% of the target compounds. Brooch concentrations were significantly correlated with those from active air samplers from which we conclude that the brooches could be used to approximate inhalation exposure and other exposures related to air concentrations such as dermal exposure. The generic sampling rate of the brooch (19 ± 11 m³ day^-1 dm^-2) was 13 and 22 times greater than estimated for home and office environments, respectively, likely because of the dusty work environment and greater movement of e-waste workers. BDE-209 concentrations in brooches and wristbands were moderately and significantly (p < 0.05) correlated with levels in blood plasma; organophosphorus esters in brooches and wristbands were weakly and insignificantly correlated with their metabolite biomarkers in post-shift spot urine samples. Silicone brooches and wristbands deployed over a single shift in a dusty occupational setting can be useful for indicating the internal exposure to compounds with relatively long biological half-lives, but their use for compounds with relatively short half-lives is not clear and may require either a longer deployment time or an integrated biomarker measure.

The use of silicone wristbands to evaluate personal exposure to semi-volatile organic chemicals (SVOCs) in France and Italy

In this exploratory study, we measured for the first-time human exposure to about 90 semi-volatile organic chemicals (SVOCs) in France and Italy using silicone wristbands. Participants in France (n = 40) and in Italy (n = 31) wore a silicone wristband for five days during 2018 and 2019. Samples were analyzed for 39 polybrominated diphenyl ethers (PBDEs), 10 novel brominated flame retardants (nBFRs), 25 organophosphate esters (OPEs), and 18 polycyclic aromatic hydrocarbons (PAHs). In both groups, the most commonly detected chemicals were BDE-209, BEHTBP, tris[(2R)-1-chloro-2-propyl] phosphate (TCIPP), and phenanthrene among PBDEs, nBFRs, OPEs, and PAHs, respectively. The concentrations of ∑₃₉ PBDEs, ∑₁₀ nBFRs, ∑₂₅ OPEs, ∑₁₈ PAHs, and of most individual chemicals were generally significantly higher in samples from France than in those from Italy, except for BDE-209 and TCIPP. On a broader scale, the chemical concentrations were generally significantly lower in this study than those measured in the United States in previous studies using the same type of wristbands. Efforts to standardize the protocols for the use of silicone wristbands are still needed but this study shows that wristbands are capable of capturing regional differences in human exposure to a large variety of SVOCs and, therefore, can be used as personal exposure monitor for studies with global coverage.

Passive air sampling for semi-volatile organic chemicals

During passive air sampling, the amount of a chemical taken up in a sorbent from the air without the help of a pump is quantified and converted into an air concentration. In an equilibrium sampler, this conversion requires a thermodynamic parameter, the equilibrium sorption coefficient between gas-phase and sorbent. In a kinetic sampler, a time-averaged air concentration is obtained using a sampling rate, which is a kinetic parameter. Design requirements for kinetic and equilibrium sampling conflict with each other. The volatility of semi-volatile organic compounds (SVOCs) varies over five orders of magnitude, which implies that passive air samplers are inevitably kinetic samplers for less volatile SVOCs and equilibrium samplers for more volatile SVOCs. Therefore, most currently used passive sampler designs for SVOCs are a compromise that requires the consideration of both a thermodynamic and a kinetic parameter. Their quantitative interpretation depends on assumptions that are rarely fulfilled, and on input parameters, that are often only known with high uncertainty. Kinetic passive air sampling for SVOCs is also challenging because their typically very low atmospheric concentrations necessitate relatively high sampling rates that can only be achieved without the use of diffusive barriers. This in turn renders sampling rates dependent on wind conditions and therefore highly variable. Despite the overall high uncertainty arising from these challenges, passive air samplers for SVOCs have valuable roles to play in recording (i) spatial concentration variability at scales ranging from a few centimeters to tens of thousands of kilometers, (ii) long-term trends, (iii) air contamination in remote and inaccessible locations and (iv) indoor inhalation exposure. Going forward, thermal desorption of sorbents may lower the detection limits for some SVOCs to an extent that the use of diffusive barriers in the kinetic sampling of SVOCs becomes feasible, which is a prerequisite to decreasing the uncertainty of sampling rates. If the thermally stable sorbent additionally has a high sorptive capacity, it may be possible to design true kinetic samplers for most SVOCs. In the meantime, the passive air sampling community would benefit from being more transparent by rigorously quantifying and explicitly reporting uncertainty.

Advances in Comprehensive Exposure Assessment: Opportunities for the US Military

OBJECTIVE

Review advances in exposure assessment offered by the exposome concept and new -omics and sensor technologies.

METHODS

Narrative review of advances, including current efforts and potential future applications by the US military.

RESULTS

Exposure assessment methods from both bottom-up and top-down exposomics approaches are advancing at a rapid pace, and the US military is engaged in developing both approaches. Top-down approaches employ various -omics technologies to identify biomarkers of internal exposure and biological effect. Bottom-up approaches use new sensor technology to better measure external dose. Key challenges of both approaches are largely centered around how to integrate, analyze, and interpret large datasets that are multidimensional and disparate.

CONCLUSIONS

Advances in -omics and sensor technologies may dramatically enhance exposure assessment and improve our ability to characterize health risks related to occupational and environmental exposures, including for the US military.

Measuring exposure of e-waste dismantlers in Dhaka Bangladesh to organophosphate esters and halogenated flame retardants using silicone wristbands and T-shirts

Silicone (polydimethylsiloxane or PDMS) wristbands and cotton T-shirts were used to assess the exposure of e-waste recyclers in Dhaka, Bangladesh to polybrominated diphenyl ethers (PBDEs), novel brominated flame retardants (NBFRs), dechlorane plus (DPs), and organophosphate esters (OPEs). The median surface-normalized uptake rates of PBDEs, NBFRs, DPs, and OPEs were 170, 8.5, 4.8, and 270 ng/dm²/h for wristbands and 5.4, 2.0, 0.94, and 23 ng/dm²/h for T-shirts, respectively. Concentrations of Tris(2-chloroethyl) phosphate (TCEP), Tris(1,3-dichloro-2-propyl) phosphate (TDCIPP), Tri-m-cresyl phosphate (TmCP), Bis(2-ethlyhexyl) tetrabromophthalate (BEH-TEBP), and Dechlorane plus (DPs) in wristbands were significantly correlated with those in T-shirts. Wristbands accumulated ~7 times more mass than T-shirts, especially of compounds expected to be mainly in the gas phase. We introduce the silicone "sandwich" method to approximate the easily releasable fraction (ERF) from T-shirts, hypothesized to be related to dermal exposure. ERFs varied from 6 to 75% of total chemical accumulated by T-shirts and were significantly negatively correlated with compounds' octanol-air partition coefficient (log K_oa). The median daily exposure doses via dermal transfer from the front of the T-shirt to the front body trunk were 0.32, 0.13, 0.11, and 9.1 ng/kg-BW/day for PBDEs, NBFRs, DPs, and OPEs, respectively. The evidence of e-waste recycler exposure to flame retardants in this low income country, lacking protective personal equipment, calls for measures to minimize their exposure and for chemical management regulations to consider exposures to chemicals in waste products.

Predicting Sorbent-Air Partition Coefficients for Terpenoids at Multiple Temperatures

Partition coefficients describe the relative concentration of a chemical equilibrated between two phases. In the design of air samplers, the sorbent-air partition coefficient is a critical parameter, as is the ability to extrapolate or predict partitioning at a variety of temperatures. Our specific interest is the partitioning of plant-derived terpenes (hydrocarbons formed from isoprene building blocks) and terpenoids (with oxygen-containing functional groups) in polydimethylsiloxane (PDMS) sorbents. To predict K P D M S / A I R as a function of temperature for compounds containing carbon, hydrogen, and oxygen, we developed a group contribution model that explicitly incorporates the van't Hoff equation. For the 360 training compounds, predicted K P D M S / A I R values strongly correlate (R² > 0.987) with K P D M S / A I R values measured at temperatures from 60 °C to 200 °C. To validate the model with available literature data, we compared predictions for 50 additional C₁₀ compounds, including 6 terpenes and 22 terpenoids, with K P D M S / A I R values measured at 100 °C and determined an average relative error of 3.1 %. We also compared predictions with K P D M S / A I R values measured at 25 °C. The modeling approach developed here is advantageous for properties with limited experimental values at a single temperature.

Silicone wristbands integrate dermal and inhalation exposures to semi-volatile organic compounds (SVOCs)

Silicone wristbands are being increasingly used to assess human exposure to semi-volatile organic compounds (SVOCs). However, it is unclear what exposure pathways wristbands integrate. To test the hypothesis that wristbands integrate inhalation and dermal exposures, we measured 38 chemicals from four compound groups (PAHs, PBDEs, nBFRs, and OPEs) in silicone wristbands and brooches, active air samples (Occupational Safety and Health Administration Versatile Sampler or OVS cartridge), and hand wipes from 10 adults during a 72-hour period. Phenanthrene, BDE-47, 2‑ethylhexyl 2,3,4,5‑tetrabromobenzoate (EHTBB), tris[(2R)‑1‑chloro‑2‑propyl] phosphate (TCIPP), and tris(1,3‑dichloro‑2‑propyl) phosphate (TDCIPP) were the predominant compounds in all four matrices. In a linear regression analysis, the compound levels in OVS were positively associated with those in wristbands and brooches for nBFRs and OPEs, but not for PAHs and PBDEs. The compound levels in wristbands were positively associated with those in hand wipes and brooches for all chemicals. The regressions between the levels in wristbands and OVS or brooches combined with the levels in hand wipes showed stronger, supporting the hypothesis that wristbands captured inhalation and dermal exposure pathways.

Theory and modelling approaches to passive sampling

Designs and applications of passive samplers for various environmental compartments have been broadened significantly since their introduction. Understanding the theory behind passive sampling is essential for proper development of sampling methods and for accurate interpretation of the results. Theoretical underpinnings of passive sampling have been explored using different approaches. The aim of this review is to describe passive sampling theory and modelling approaches presented in the literature in a manner that allows researchers to obtain comprehensive understanding of them and to recognize the assumptions behind each approach together with their applicability to a given passive sampling technique. A common approach originates from Whitman's two-film theory and produces an exponential model that describes the entire passive sampling process. This approach, however, is based on several assumptions including linear exchange kinetics between the sampled medium and the passive sampler. Two-phase air passive samplers with a well-defined barrier are commonly modeled based on the zero-sink assumption, which assumes efficient trapping of analytes in the receiving phase. This assumption may become invalid under various scenarios; consequently, other approaches to modelling have been introduced including simulation of the sampling process by approximate temporal-steady states in hypothetical segments in the adsorption phase. Another approach uses dynamic models to determine accumulation of analytes in passive samplers. Dynamic models are capable of describing mass accumulation in the passive sampler, its transient response, and its response to fluctuations in environmental concentrations. Finally, empirically calibrated models, attempting to simplify the process of passive sampling rate determination, are also presented. In general, dynamic models are used to establish a profound understanding of the sampling process and analyse the applicability of the simpler models and their assumptions, while the simplified models are desirable and practical for most users. Nonetheless, due to the advancement in the computational tools, application of the dynamic models could be made simple and user-friendly.

Calibration of polydimethylsiloxane and polyurethane foam passive air samplers for measuring semi volatile organic compounds using a novel exposure chamber design

Passive air sampling is increasingly used for air quality monitoring and for personal sampling. In a novel experimental exposure chamber study, 3 types of polydimethylsiloxane (PDMS, including sheet and wristband) and 1 type of polyurethane foam (PUF) passive air samplers were tested for gas-phase uptake of 200 semi volatile organic compounds (SVOCs) during six months. For 155 SVOCs including PAH, PCB, phthalates, organophosphate esters, musk compounds, organochlorine- and other pesticides, a normalized generic uptake rate (Rs) of 7.6 ± 1.3 m³ d^-1 dm^-2 and a generic mass transfer coefficient (MTC) of 0.87 ± 0.15 cm s^-1 at a wind speed of 1.3 m s^-1 were determined. Variability of sampling rates within and between passive sampling media and analyte groups was not statistically significant, supporting the hypothesis of air-side controlled uptake regardless of sampling material. A statistical relationship was developed between the sampling rate and windspeed which can be used to obtain a sampling rate applicable to specific deployment conditions. For 98 SVOCs, partition coefficients (Ksampler-air) for PUF and PDMS were obtained, which determine the duration of linear uptake and capacity of the sampler for gas-phase uptake. Ksampler-air for PDMS were approximately 10 times higher than for PUF, suggesting that PDMS can be deployed for longer time per volume of sampler, while uptake remains in the linear phase. Statistical relationships were developed to estimate Kpuf-air and Kpdms-air from Koa. These results improve the understanding of the performance of PDMS and PUF passive samplers and contribute to the development of PDMS for the use as a promising personal sampler.

Patterns of Personal Exposure to Urban Pollutants Using Personal Passive Samplers and GC × GC/ToF-MS

The performance of silicon wristband passive samplers (WB), combined with comprehensive two-dimensional gas-chromatography/time-of-flight mass-spectrometry (GC × GC/ToF-MS), for the analysis of urban derived pollutants in the personal environment was evaluated. Cumulative 5-day exposure samples from 27 individuals in areas with different geographical/socioeconomic characteristics within the Santiago Metropolitan Region (Chile) were collected during winter and summer (2016-2017). Samples were extracted without cleanup/fractionation and analyzed using targeted and nontargeted methods. The quantified semivolatile organic compounds (SVOCs, n = 33) (targeted analysis), and tentatively identified features ( n = 595-1011) (nontargeted analysis) were classified according to their use/source. Seasonal differences were observed in the targeted analysis, while seasonal and spatial differences were observed in the nontargeted analysis. Higher concentrations of combustion products were observed in winter, while higher concentrations of consumer products were found in summer. Spatial differences were observed in hierarchical clustering analysis of the nontargeted data, with distinct clusters corresponding to specific subregions of the urban area. Results from this study provide spatial and seasonal distributions of urban pollutants within an urban area and establish the utility of linking WB with nontargeted analysis as a tool to identify and prioritize new exposures to urban contaminants at the local/community level.