Characterizing firefighter's exposure to over 130 SVOCs using silicone wristbands: A pilot study comparing on-duty and off-duty exposures

The Fire Fighter Cancer Cohort Study: Protocol for a Longitudinal Occupational Cohort Study

BACKGROUND

Firefighters are at an increased risk of cancer and other health conditions compared with the general population. However, the specific exposures and mechanisms contributing to these risks are not fully understood. This information is critical to formulate and test protective interventions.

OBJECTIVE

The purpose of the Fire Fighter Cancer Cohort Study (FFCCS) is to conduct community-engaged research with the fire service to advance the evaluation and reduction of firefighter exposures, along with understanding and mitigating effects leading to an increased risk of cancer and other health conditions. This involves establishing a long-term (>30 years) firefighter multicenter prospective cohort study.

METHODS

The structure of the FFCCS includes a fire service oversight and planning board to provide guidance and foster communication between researchers and fire organizations; a data coordinating center overseeing survey data collection and data management; an exposure assessment center working with quantitative exposure data to construct a firefighter job exposure matrix; and a biomarker analysis center, including a biorepository. Together, the centers evaluate the association between firefighter exposures and toxic health effects. Firefighter research liaisons are involved in all phases of the research. The FFCCS research design primarily uses a set of core and project-specific survey questions accompanied by a collection of biological samples (blood and urine) for the analysis of biomarkers of exposure and effect. Data and samples are collected upon entry into the study, with subsequent collection after eligible exposures, and at intervals (eg, 1-2 years) after enrollment. FFCCS data collection and analysis have been developed to evaluate unique exposures for specific firefighter groups; cancer risks; and end points in addition to cancer, such as reproductive outcomes. Recruitment is carried out with coordination from partnering fire departments and eligible participants, including active career and volunteer firefighters in the United States.

RESULTS

The FFCCS protocol development was first funded by the US Federal Emergency Management Agency in 2016, with enrollment beginning in February 2018. As of September 2024, >6200 participants from >275 departments across 31 states have enrolled, including recruit and incumbent firefighters. Biological samples have been analyzed for measures of exposure and effect. Specific groups enrolled in the FFCCS include career and volunteer structural firefighters, women firefighters, trainers, fire investigators, wildland firefighters, firefighters responding to wildland-urban interface fires, and airport firefighters. Peer-reviewed published results include measurement of exposures and the toxic effects of firefighting exposure. Whenever possible, research results are provided back to individual participants.

CONCLUSIONS

The FFCCS is a unique, community-engaged, multicenter prospective cohort study focused on the fire service. Study results contribute to the evaluation of exposures, effects, and preventive interventions across multiple sectors of the US fire service, with broad implications nationally.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/70522.

Addressing the need for individual-level exposure monitoring for firefighters using silicone samplers

BACKGROUND

Firefighters are occupationally exposed to hazardous chemical mixtures. Silicone passive sampling devices capture unique exposures over time with minimal impact to the participant and allow for the analysis of a broad chemical space.

OBJECTIVE

Silicone dog tags were worn by firefighters while on- and off-duty to measure individual exposures, identify potential occupational exposures, and assess their relation to occupational variables including fire response frequency, rank, and years as a firefighter.

METHODS

Fifty-six firefighters were recruited from two fire departments with relatively high and low call volumes in the Kansas City metropolitan area to wear two different silicone dog tags as passive samplers while on- and off-duty. Each dog tag was worn for a cumulative 30-day exposure period. Extracts of the dog tags were analyzed with gas chromatography, mass spectrometry methods for 43 flame retardants (FRs), 21 volatile organic compounds (VOCs), 42 polychlorinated biphenyls (PCBs), and 63 polycyclic aromatic hydrocarbons (PAHs).

RESULTS

Ninety-two total chemicals were detected, with eight chemicals not previously reported in firefighter exposure studies. Based on the magnitude and frequency of increased exposure in on-duty dog tags, relative to paired off-duty dog tags, five PBDEs and sec-butylbenzene were identified as potential occupational exposures; sec-butylbenzene and PBDE 49 have not previously been reported in firefighter exposure studies to the authors' knowledge. Multivariate analyses for these six compounds indicated that firefighter rank, fire response rates, and years in the fire service were poor indicators of increased occupational exposure. The greatest on-duty exposures to PBDEs were found in the low-call volume department among operational firefighters. Dog tags from firefighters at the high-call volume department accounted for 75% of PCB detections; one particular fire response may have contributed to this. Additionally, there was measurable similarity in total chemical exposure profiles between paired on- and off-duty tags for some firefighters.

IMPACT

This study used personal silicone passive samplers in the configuration of dog tags worn around the neck to quantify firefighter occupational exposure in on-duty samples relative to paired off-duty samples for several chemical categories: flame retardants, VOCs, and PCBs. Five PBDEs and sec-butylbenzene were identified as potential occupational exposures, however their prevalence in on-duty tags was not associated with frequency of fire responses, firefighter rank, or years the firefighter has been in the fire service. Additionally, similarity between chemical exposures in on- and off-duty tags from the same firefighter invites further investigation into individual behaviors influencing occupational and para-occupational exposures.

Tracking toxic chemical exposure in Uganda: Insights from silicone wristbands

The increasing use of synthetic chemicals, including pesticides for agriculture and flame retardants from consumer products like electronics, raises environmental concerns for public health and biodiversity, particularly in agricultural and rural communities. Although these chemicals have been extensively studied in industrialized regions, data on human exposure particulary near protected areas in sub-Saharan Africa, remain scarce. This study provides novel insights into chemical exposure among different occupational groups in Uganda using silicone wristbands. We collected 39 silicone wristbands from participants living around Kibale National Park, including tea workers (n = 8), researchers (n = 10), commercial farmers (n = 6), subsistence farmers (n = 7), and urban workers (n = 8), and analyzed for 21 polybrominated biphenyl ethers (PBDEs), 11 novel flame retardants (nFRs), 20 current-use pesticides (CUPs), and 21 organochlorine pesticides (OCPs). CUPs the most abundant chemicals detected (range 18.2-54.4 ng/g), were significantly higher for commercial and subsistence farmers and tea workers. Urban workers and researchers had higher levels of PBDEs and nFRs than the other three groups with BDE-47, -99, -139, -153, -209, bis (2-ethylhexyl) tetrabromophthalate (BETHTBP) and decabromodiphenylethane (DBDPE) being the most detected compounds. Ametryn, β-HCH, o,p'-DDT, p,p'-DDT, and endosulfan sulfate were the most frequently detected pesticides. The widespread detection of legacy and emerging chemicals at levels similar to urban and industrialized areas among populations near a protected area in Eastern Africa highlights an urgent environmental and public health concern.

Silicone wristbands for assessing personal chemical exposures: impacts of movement on chemical uptake rates

Silicone wristbands are utilized as personal passive sampling devices for exposure assessments of semi-volatile organic compounds (SVOCs). While research demonstrates that accumulation of SVOCs on the wristbands correlates with internal dose for many different chemical classes, the mechanisms of accumulation remain poorly understood. Multiple factors such as movement of the individual lead to variable mass transfer conditions at the sampler interface. The objective of this study was to investigate the effect of air flow velocity across the wristband surface on SVOC uptake rates and to evaluate if enhanced rates vary between compounds with a range physicochemical properties. Experiments were conducted in a residential home where wristbands were either held in static conditions or attached to an end-over-end rotator at different speeds for a four week period. We measured the uptake of 17 different SVOCs that are commonly detected in indoor environments and compared their accumulation rates as a function of the rotating velocity. For wristbands moving at tangential speeds of 0.05, 0.5, and 1.1 m s-1 (relevant for a walking pace), the motion enhanced uptake rates by 1.2 ± 0.2, 3.2 ± 0.6, and 4.3 ± 0.8 times the respective rates for the static controls. This enhancement is consistent with gas phase diffusion-controlled mass transfer theory at the wristband interface. Moreover, the enhancement of uptake positively correlated with octanol-air partition coefficients log KOA (R = 0.6; p < 0.02) of the chemicals and negatively correlated with diffusivity (R = 0.5; p < 0.05). In a comparison with worn wristband studies, the ratio of uptakes rates for worn relative to rotating wristbands correlated with SVOC properties (R = 0.85 for log KOA). For SVOCs with log KOA > 9, uptake rates on worn wristbands greatly exceeded (by a factor of 10 to 104) the respective rates in this rotator experiment. These results suggest that a mass transfer mechanism based solely on gas-solid partitioning under variations in air velocity cannot fully explain uptake on worn wristbands. Instead, the results implicate additional processes such as particle phase deposition, direct contact with certain materials, and excretion from skin as pathways of accumulation on the wristband sampler and personal exposure.

Evaluation of Passive Silicone Samplers Compared to Active Sampling Methods for Polycyclic Aromatic Hydrocarbons During Fire Training

Firefighters are occupationally exposed to many chemicals, including polycyclic aromatic hydrocarbons (PAHs), which are formed by the incomplete combustion of organic matter during fire response and training activities. However, due to the harsh environments in which firefighters work, as well as consideration for time and physical safety while wearing bulky equipment, traditional active sampling methods may not be feasible to measure PAH exposures. Silicone passive samplers offer an alternative approach to assess exposure during fire responses and live fire training due to their heat resistance and ease of deployment in remote or time-limited environments. In this study, the primary objective was to investigate and determine the statistical strength of the relationship between active air sampling methods and passive silicone samplers for PAHs. In this study, silicone wristbands were paired with active sampling devices in a series of burn experiments to compare PAH measurements. Silicone-based measurements correlated strongly with active air samples for the dominant PAHs found, naphthalene and phenanthrene; however, detection was limited in the wristbands when air concentrations were low in active samples. In situations where PAH levels are expected to be high and the potential for contaminant loss via off-gassing is low, silicone samplers may be a useful tool for industrial hygienists to measure PAHs in fire and other emergency responses in extreme environments.

Environmental Exposures and Canine Bladder Cancer: A Case Control Study Using Silicone Passive Samplers

Pet dogs offer valuable models for studying environmental impacts on human health due to shared environments and a shorter latency period for cancer development. We assessed environmental chemical exposures in a case-control study involving dogs at high risk of urothelial carcinoma, identified by a BRAF V595E mutation in urinary epithelial cells. Cases (n = 25) exhibited low-level BRAF mutations, while controls (n = 76) were matched dogs without the mutation. Each dog wore a silicone sampler for five continuous days to assess environmental exposures. Silicone samplers were analyzed using targeted and suspect screening (i.e., nontargeted) methods. Of 115 targeted chemicals, 39 were detected in >50% of samplers, with cases showing significantly higher levels (2-3×) of BDE-47, BDE-99, anthracene, and benzyl butyl phthalate (p < 0.05). Suspect screening identified that cases were exposed to more chemicals, often at higher exposure levels. For example, cases had significantly higher levels of 25 chemical features compared to controls (p < 0.05). This is the largest study to date to quantify such a wide breadth of contaminant exposure levels associated with canine urothelial carcinoma and the first to assess a population with subclinical disease, highlighting pet dogs as models to study environmental contributions to cancer risk, advancing both human and veterinary health.

Advancing environmental epidemiologic methods to confront the cancer burden

Even though many environmental carcinogens have been identified, studying their effects on specific cancers has been challenging in nonoccupational settings, where exposures may be chronic but at lower levels. Although exposure measurement methods have improved considerably, along with key opportunities to integrate multi-omic platforms, there remain challenges that need to be considered, particularly around the design of studies. Cancer studies typically exclude individuals with prior cancers and start recruitment in midlife. This translates into a failure to capture individuals who may have been most susceptible because of both germline susceptibility and higher early-life exposures that lead to premature mortality from cancer and/or other environmentally caused diseases like lung diseases. Using the example of breast cancer, we demonstrate how integration of susceptibility, both for cancer risk and for exposure windows, may provide a more complete picture regarding the harm of many different environmental exposures. Choice of study design is critical to examining the effects of environmental exposures, and it will not be enough to just rely on the availability of existing cohorts and samples within these cohorts. In contrast, new, diverse, early-onset case-control studies may provide many benefits to understanding the impact of environmental exposures on cancer risk and mortality. This article is part of a Special Collection on Environmental Epidemiology.

Determining personal exposure to high production volume chemicals (HPVCs) and polycyclic aromatic hydrocarbons (PAHs) with silicone wristbands: A pilot study

High production volume chemicals (HPVCs) and polycyclic aromatic hydrocarbons (PAHs) are semi-volatile organic compounds (semi-VOCs) of great environmental concern because of their presence worldwide and health problems resulting from long-term exposure to some of them. It is essential to have robust analytical methods to monitor the concentrations of these compounds not only in environmental samples but also individual exposure. In this pilot study we develop and validate a multiresidue analytical method based on ultrasound-assisted extraction and gas-chromatography mass spectrometry for the simultaneous determination of 56 semi-VOCs using silicone wristbands (SWBs) as personal passive samplers. The developed method provided recoveries between 43% and 114% on sampled SWBs and method detection and quantification limits in the range of 0.1-35 ng/g and 0.3-119 ng/g, respectively. A preliminary study was performed with a small group of adults living in the industrial city of Tarragona (north-eastern Spain) to evaluate the applicability of SWBs for monitoring individual exposure to the studied HPVCs and PAHs. Benzothiazoles, benzenesulfonamides, UV stabilisers and phenolic antioxidants were determined for the first time in SWBs. Phthalates (PAEs), stood out above the rest, accounting for 52% of the total concentrations. Diethylhexyl phthalate was the compound found at the highest concentrations with values between 1.1 and 82 μg/g. Carcinogenic and non-carcinogenic dermal risk assessment was performed for adults and considering two scenarios (low and high). PAHs were the compounds with the highest carcinogenic and non-carcinogenic dermal risk regardless of the exposure scenario. The second family of compounds that contributed the most to the total risk were PAEs but high punctual concentrations of these compounds caused significant differences between exposure scenarios.

Children's exposure to chemical contaminants: Demographic disparities and associations with the developing basal ganglia

Children are regularly exposed to chemical contaminants that may influence brain development. However, relatively little is known about how these contaminants impact the developing human brain. Here, we combined silicone wristband exposure assessments with neuroimaging for the first time to examine how chemical contaminant mixtures are associated with the developing basal ganglia-a brain region key for the healthy development of emotion, reward, and motor processing, and which may be particularly susceptible to contaminant harm. Further, we examined demographic disparities in exposures to clarify which children were at highest risk for any contaminant-associated neurobiological changes. Participants included 62 community children (average age 7.00 years, 53% female, 66% White) who underwent structural neuroimaging to provide data on their basal ganglia structure and wore a silicone wristband for seven days to track their chemical contaminant exposure. 45 chemical contaminants-including phthalates and their alternatives, brominated flame retardants, organophosphate esters, pesticides, polycyclic aromatic hydrocarbons, and polychlorinated biphenyls-were detected in over 75% of wristbands. Notable demographic disparities in exposure were present, such that Non-White and lower-income children were more exposed to several contaminants. Exposure to chemical contaminant mixtures was not associated with overall basal ganglia volume; however, two organophosphate esters (2IPPDPP and 4IPPDPP) were both associated with a larger globus pallidus, a basal ganglia sub-region. Results highlight demographic disparities in exposure and suggest possible risks to a brain region key for healthy emotional development.

Associations of environmental chemical exposures measured in personal silicone wristbands with sociodemographic factors, COVID-19 restrictions, and child respiratory health

BACKGROUND

Although human biomonitoring of environmental chemicals has been considered a gold standard, these methods can be costly, burdensome, and prone to unwanted sources of variability that may cause confounding. Silicone wristbands have recently emerged as innovative passive samplers for measuring personal exposures.

METHODS

In a pilot study from 2019 to 2021 involving 55 children aged 5-9 years in Seattle and Yakima, Washington, we utilized silicone wristbands to explore associations of sociodemographic variables and COVID-19-related restrictions, including school closures, with exposures to numerous chemicals including brominated and organophosphate ester (OPE) flame retardants, polychlorinated biphenyls, polycyclic aromatic hydrocarbons (PAHs), phthalates, and pesticides. We additionally conducted the first analysis testing silicone wristband chemicals as predictors of child wheeze, individually and in mixtures via logistic weighted quantile sum regression (WQS).

RESULTS

Among 109 semi-volatile organic compounds measured, we detected 40 in >60% of wristbands worn by children continuously for an average of 5 days. Chemicals were generally positively correlated, especially within the same class. Male sex and increasing age were linked with higher exposures across several chemical classes; Hispanic/Latino ethnicity was linked with higher exposures to some phthalates and OPEs. COVID-19 restrictions were associated with lower wristband concentrations of brominated and triaryl OPE flame retardants. Each one-decile higher WQS exposure index was suggestively associated with 2.11-fold [95% CI: 0.93-4.80] higher odds of child wheeze. Risk of child wheeze was higher per 10-fold increase in the PAH chrysene (RR = 1.93[1.07-3.49]), the pesticide cis-permethrin (3.31[1.23-8.91]), and di-isononyl phthalate (DINP) (5.40[1.22-24.0]) CONCLUSIONS: Our identification of demographic factors including sex, age, and ethnicity associated with chemical exposures may aid efforts to mitigate exposure disparities. Lower exposures to flame retardants during pandemic restrictions corroborates prior evidence of higher levels of these chemicals in school versus home environments. Future research in larger cohorts is needed to validate these findings.

Characterization of exposure to air pollutants for workers in and around fires

Firefighters can be occupationally exposed to a wide range of airborne pollutants during fire-extinguishing operations. The overall study aim was to characterize occupational exposure to smoke for several groups of workers responding to fires, with specific aims to determine the correlations between exposure markers and to biologically assess their systemic exposure to polycyclic aromatic hydrocarbons (PAHs) in urine. Personal exposure measurements of equivalent black carbon (eBC), elemental carbon (EC), organic carbon (OC), nitrogen dioxide (NO2), PAHs, lung deposited surface area (LDSA), and particle number concentration (PNC) of ultrafine particles were performed on firefighters, observers, and post-fire workers during firefighting exercises. Urine samples were collected before and after exposure and analyzed for PAH metabolites. Additional routes for PAH skin exposure were investigated by wipe sampling on defined surfaces: equipment, personal protective equipment (PPE), and vehicles. Among workers without PPE, observers generally had higher exposures than post-fire workers. The observers and post-fire workers had an occupational exposure to smoke measured e.g. as EC of 7.3 µg m-3 and 1.9 µg m-3, respectively. There was a good agreement between measurements of carbonaceous particles measured as EC from filters and as eBC with high time resolution, especially for the observers and post-fire workers. Ultrafine particle exposure measured as LDSA was two times higher for observers compared to the post-fire workers. The urinary levels of PAH metabolites were generally higher in firefighters and observers compared to post-fire workers. Investigation of PAH contamination on firefighters' PPE revealed high PAH contamination on surfaces with frequent skin contact both before and after cleaning. Exposure to smoke can be assessed with several different exposure markers. For workers residing unprotected around fire scenes, there can be high peak exposures depending on their behavior concerning the smoke plume. Several workers had high urinary PAH metabolite concentrations even though they were exposed to low air concentrations of PAHs, indicating skin absorption of PAH as a plausible exposure route.

Online SPE-LC-MS-MS method for eight hydroxylated metabolites of polycyclic aromatic hydrocarbons in urine and determination of optimal sampling time after firefighter training

Polycyclic aromatic compounds (PAHs) are formed during incomplete combustion and firefighters are inadvertently at risk of being exposed to these and other hazardous compounds. Exposure to PAHs is often estimated by measuring their hydroxylated metabolites (OH-PAH) in urine. Here, an online-SPE LC-MS-MS method was set up for eight OH-PAHs thus increasing sample throughput and minimizing manual handling. The method was validated over a 5-month period and showed good reproducibility with intra- and inter-day variation of 2.4-8.1 % and 1.6-6.5 %, respectively, of low-level samples and accuracy (91.6-104.8 %) for a standard reference material. The method was applied to urine samples from conscripts training to become firefighters to determine the optimal sampling time for this training activity before a large intervention study. In total, six conscripts sampled urine 6-8 times over a 40-hr period during a 3-day training course. All eight metabolites were detected in ≥ 97 % of the samples and showed peak excretion 4-6 hrs after the training corresponding to 8-10 hrs after first exposure. Samples taken the morning after the exercise contained low levels of most metabolites. Consequently, 4-6 hrs post exposure is recommended as the optimal sampling time for quantification of PAH exposure and monitoring of potential differences in exposure.

Silicone wristbands reveal ubiquitous human exposure to ortho-phthalates and non-ortho-phthalate plasticizers in Southern California

In the United States and abroad, ortho-phthalates and non-ortho-phthalate plasticizers continue to be used within a diverse array of consumer products. Prior California-specific biomonitoring programs for ortho-phthalates have focused on rural, agricultural communities and, to our knowledge, these programs have not measured the potential for exposure to non-ortho-phthalate plasticizers. Therefore, the potential for human exposure to ortho-phthalates and non-ortho-phthalate plasticizers have not been adequately addressed in regions of California that have higher population density. Since there are numerous sources of ortho-phthalates and non-ortho-phthalate plasticizers in population-dense, urban regions, the objective of this study was to leverage silicone wristbands to quantify aggregate ortho-phthalate and non-ortho-phthalate plasticizer exposure over a 5-day period across two different cohorts (2019 and 2020) of undergraduate students at the University of California, Riverside (UCR) that commute from all over Southern California. Based on 5 d of aggregate exposure across two different cohorts, total ortho-phthalate plus non-ortho-phthalate plasticizer concentrations ranged, on average, from ∼100,000-1,000,000 ng/g. Based on the distribution of individual ortho-phthalate and non-ortho-phthalate plasticizer concentrations, the concentrations of di-isononyl phthalate (DiNP, a high molecular weight ortho-phthalate), di (2-ethylhexyl) phthalate (DEHP, a high molecular weight ortho-phthalate), and di-2-ethylhexyl terephthalate (DEHT, a non-ortho-phthalate plasticizer) detected within wristbands were higher than the remaining seven ortho-phthalates and non-ortho-phthalate plasticizers measured, accounting for approximately 94-97% of the total mass depending on the cohort. Overall, our findings raise concerns about chronic DiNP, DEHP, and DEHT exposure in urban, population-dense regions throughout California.

Breast Cancer-Related Chemical Exposures in Firefighters

To fill a research gap on firefighter exposures and breast cancer risk, and guide exposure reduction, we aimed to identify firefighter occupational exposures linked to breast cancer. We conducted a systematic search and review to identify firefighter chemical exposures and then identified the subset that was associated with breast cancer. To do this, we compared the firefighter exposures with chemicals that have been shown to increase breast cancer risk in epidemiological studies or increase mammary gland tumors in experimental toxicology studies. For each exposure, we assigned a strength of evidence for the association with firefighter occupation and for the association with breast cancer risk. We identified twelve chemicals or chemical groups that were both linked to breast cancer and were firefighter occupational exposures, including polycyclic aromatic hydrocarbons, volatile aromatics, per- and polyfluoroalkyl substances, persistent organohalogens, and halogenated organophosphate flame retardants. Many of these were found at elevated levels in firefighting environments and were statistically significantly higher in firefighters after firefighting or when compared to the general population. Common exposure sources included combustion byproducts, diesel fuel and exhaust, firefighting foams, and flame retardants. Our findings highlight breast-cancer-related chemical exposures in the firefighting profession to guide equitable worker's compensation policies and exposure reduction.

Occupational Exposure of On-Shift Ottawa Firefighters to Flame Retardants and Polycyclic Aromatic Hydrocarbons

Firefighters can be exposed to complex mixtures of airborne substances, including hazardous substances released during structural fires. This study employed silicone wristbands (SWBs) as passive samplers to investigate potential exposure to polycyclic aromatic hydrocarbons (PAHs) and flame retardants (FRs). SWBs were deployed at different areas of four fire stations, in four truck cabins, and at an office control location; they were also donned outside the jackets of 18 firefighters who responded to fire calls. Overall, office areas had significantly lower PAHs than fire station areas. Vehicle bays and truck cabins had significantly higher concentrations of low molecular weight (LMW) PAHs than sleeping and living room areas. For organophosphate ester flame retardants (OPFRs), tri-n-butyl phosphate (TnBP) and tris(1-chloro-2-propyl) phosphate (TCPP) were detected in all the samples; 2-ethylhexyl diphenyl phosphate (EHDPP) was more frequently detected in the fire station areas. Triphenyl phosphate (TPP) concentrations were highest in the truck cabin and office areas, and tris(1,3-dichloro-2-propyl)phosphate (TDCPP) was highest in truck cabins. Thirteen of 16 PAHs and nine of 36 OPFRs were detected in all the SWBs worn by firefighters, and tris (2-butoxyethyl) phosphate (TBEP) was the predominant OPFR. Levels of LMW PAHs were significantly lower when firefighters did not enter the fire. LMW PAHs, HMW (high molecular weight) PAHs, and EHDPP were significantly elevated when heavy smoke was reported. This work highlights the potential for occupational exposure to PAHs and flame retardants in some fire station areas; moreover, factors that may influence exposure during fire suppression. Whilst firefighters' occupational exposure to PAHs is likely related to fire suppression and exposure to contaminated gear and trucks, exposure to OPFRs may be more related to their presence in truck interiors and electronics.

Silicone Wristbands as a Personal Passive Sampler to Evaluate Indoor Exposure to Volatile and Non-volatile PFASs

Exposure to per- and polyfluoroalkyl substances (PFASs) primarily occurs via consumption of contaminated drinking water and food; however, individuals can also be exposed dermally and via inhalation indoors. This study developed an analytical method for measuring volatile PFASs in silicone wristbands and used them to assess personal exposure in a Midwestern community (n = 87). Paired samples of blood and wristbands were analyzed for PFASs using LC-MS/MS and GC-HRMS to monitor both non-volatile and volatile PFASs. The most frequently detected PFASs in wristbands were: 6:2 diPAP, 6:2 FTOH, MeFOSE and EtFOSE. Females had a 4-fold higher exposure to 6:2 diPAP compared to males and age-dependent differences in exposure to 6:2 FTOH, MeFOSE and EtFOSE were observed. Exposure to MeFOSE and EtFOSE differed based on the average time spent in the home. Frequently detected PFASs in blood were: PFOA, PFOS, PFHxS, PFHpS, and N-MeFOSAA. A strong correlation was found between MeFOSE in the wristbands and N-MeFOSAA in serum (rs = 0.90, p-value <0.001), suggesting exposure to this PFAS was primarily via inhalation and dermal exposure. These results demonstrate that wristbands can provide individual level data on exposure to some polyfluoroalkyl precursors present indoors that reflect serum levels of their suspected biotransformation products.

Wristband Personal Passive Samplers and Suspect Screening Methods Highlight Gender Disparities in Chemical Exposures

Wristband personal samplers enable human exposure assessments for a diverse range of chemical contaminants and exposure settings with a previously unattainable scale and cost-effectiveness. Paired with nontargeted analyses, wristbands can provide important exposure monitoring data to expand our understanding of the environmental exposome. Here, a custom scripted suspect screening workflow was developed in the R programming language for feature selection and chemical annotations using gas chromatography-high-resolution mass spectrometry data acquired from the analysis of wristband samples collected from five different cohorts. The workflow includes blank subtraction, internal standard normalization, prediction of chemical uses in products, and feature annotation using multiple library search metrics and metadata from PubChem, among other functionalities. The workflow was developed and validated against 104 analytes identified by targeted analytical results in previously published reports of wristbands. A true positive rate of 62 and 48% in a quality control matrix and wristband samples, respectively, was observed for our optimum set of parameters. Feature analysis identified 458 features that were significantly higher on female-worn wristbands and only 21 features that were significantly higher on male-worn wristbands across all cohorts. Tentative identifications suggest that personal care products are a primary driver of the differences observed.

Per- and polyfluoroalkyl substances (PFAS) in paired tap water and house dust from United States homes

Most people in the United States have been exposed to per- and polyfluoroalkyl substances (PFAS) which have been linked to a wide array of adverse health conditions in adults and children. The consumption of contaminated drinking water is an important human exposure pathway to PFAS. Residential sources also contribute to PFAS exposure through dermal contact and ingestion of house dust, which acts as an aggregate of chemicals from sources like furnishing materials and consumer products. The U.S. Department of Housing and Urban Development (HUD) conducted the first nationwide survey of residential hazards called the American Healthy Homes Survey (AHHS) in 2005, followed by a second survey (AHHS II) in 2017. The U.S. Environmental Protection Agency (EPA) collaborated with HUD on both efforts and subsequently analyzed PFAS in household tap water and house dust collected from the same homes during the AHHS II study. This study leverages these paired samples to investigate potentially important exposure sources and pathways in the residential environment. Here we report results for paired household tap water and house dust samples from 241 homes for 13 and 16 PFAS chemicals, respectively. All 13 targeted chemicals were detected in the household tap water samples with detections ranging from 100 % for PFBS to 1 % for PFNS, and all 16 targeted chemicals were detected in the house dust samples with detections ranging from 97 % for PFOA to 9 % for PFNS. Four chemicals (PFOA, PFOS, PFHxS, and PFHpA) were measured above the limit of detection in at least 50 % of the samples in both media. All households had at least one of the targeted PFAS detected in both their tap water and house dust. Results provided evidence that geographical factors, such as proximity to ambient contamination sources, were main drivers of PFAS contamination in tap water, while PFAS contamination in house dust was driven mainly by within-home sources. Exposure estimates calculated from the measured PFAS concentrations highlight the importance of addressing potential sources of exposure to PFAS within homes in addition to ambient sources affecting communities' drinking water, particularly to reduce children's exposure to these chemicals.

Association of co-exposure to organophosphate esters and per- and polyfluoroalkyl substances and mixture with cardiovascular-kidney-liver-metabolic biomarkers among Chinese adults

BACKGROUND

Organophosphate esters (OPEs) and Per- and polyfluoroalkyl substances (PFAS) are ubiquitous environmental contaminants with common exposure sources, leading to their widespread presence in human body. However, evidence on co-exposure to OPEs and PFAS and its impact on cardiovascular-kidney-liver-metabolic biomarkers remains limited.

METHODS

In this cross-sectional study, 467 adults were enrolled from January to May 2022 during physical visits in Shijiazhuang, Hebei province. Eleven types of OPEs and twelves types of PFAS were detected, among which eight OPEs and six PFAS contaminants were detected in more than 60% of plasma samples. Seventeen biomarkers were assessed to comprehensively evaluate the cardiovascular-kidney-liver-metabolic function. Multiple linear regression, multipollutant models with sparse partial least squares, and Bayesian kernel machine regression (BKMR) models were applied to examine the associations of individual OPEs and PFAS and their mixtures with organ function and metabolism, respectively.

RESULTS

Of the over 400 exposure-outcome associations tested when modelling, we observed robust results across three models that perfluorohexanoic acid (PFHxS) was significantly positively associated with alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin (TBIL), and indirect bilirubin (IBIL). Perfluorononanoic acid was significantly associated with decreased AST/ALT and increased very-low-density lipoprotein cholesterol levels. Besides, perfluorodecanoic acid was correlated with increased high lipoprotein cholesterol and perfluoroundecanoic acid was consistently associated with lower glucose level. BKMR analysis showed that OPEs and PFAS mixtures were positively associated with IBIL and TBIL, among which PFHxS was the main toxic chemicals.

CONCLUSIONS

Our findings suggest that exposure to OPEs and PFAS, especially PFHxS and PFNA, may disrupt organ function and metabolism in the general population, providing insight into the potential pathophysiological mechanisms of OPEs and PFAS co-exposure and chronic diseases.

Characterization of fire investigators' polyaromatic hydrocarbon exposures using silicone wristbands

BACKGROUND

Exposures to polyaromatic hydrocarbons (PAHs) contribute to cancer in the fire service. Fire investigators are involved in evaluations of post-fire scenes. In the US, it is estimated that there are up to 9000 fire investigators, compared to approximately 1.1 million total firefighting personnel. This exploratory study contributes initial evidence of PAH exposures sustained by this understudied group using worn silicone passive samplers.

OBJECTIVES

Evaluate PAH exposures sustained by fire investigators at post-fire scenes using worn silicone passive samplers. Assess explanatory factors and health risks of PAH exposure at post-fire scenes.

METHODS

As part of a cross-sectional study design, silicone wristbands were distributed to 16 North Carolina fire investigators, including eight public, seven private, and one public and private. Wristbands were worn during 46 post-fire scene investigations. Fire investigators completed pre- and post-surveys providing sociodemographic, occupational, and post-fire scene characteristics. Solvent extracts from wristbands were analyzed via gas chromatography-mass spectrometry (GC-MS). Results were used to estimate vapor-phase PAH concentration in the air at post-fire scenes.

RESULTS

Fire investigations lasted an average of 148 minutes, standard deviation ± 93 minutes. A significant positive correlation (r=0.455, p<.001) was found between investigation duration and PAH concentrations on wristbands. Significantly greater time-normalized PAH exposures (p=0.039) were observed for investigations of newer post-fire scenes compared to older post-fire scenes. Regulatory airborne PAH exposure limits were exceeded in six investigations, based on exposure to estimated vapor-phase PAH concentrations in the air at post-fire scenes.

DISCUSSION

Higher levels of off-gassing and suspended particulates at younger post-fire scenes may explain greater PAH exposure. Weaker correlations are found between wristband PAH concentration and investigation duration at older post-fire scenes, suggesting reduction of off-gassing PAHs over time. Exceedances of regulatory PAH limits indicate a need for protection against vapor-phase contaminants, especially at more recent post-fire scenes.

Per- and polyfluoroalkyl substances (PFAS) in senior care facilities and older adult residents

Per- and polyfluoroalkyl substances (PFAS) are fluorinated organic compounds used in a variety of consumer products and industrial applications that persist in the environment, bioaccumulate in biological tissues, and can have adverse effects on human health, especially in vulnerable populations. In this study, we focused on PFAS exposures in residents of senior care facilities. To investigate relationships between indoor, personal, and internal PFAS exposures, we analyzed 19 PFAS in matched samples of dust collected from the residents' bedrooms, and wristbands and serum collected from the residents. The median ∑PFAS concentrations (the sum of all PFAS detected in the samples) measured in dust, wristbands, and serum were 120 ng/g, 0.05 ng/g, and 4.0 ng/mL, respectively. The most abundant compounds in serum were linear- and branched-perfluorooctane sulfonic acid (L-PFOS and B-PFOS, respectively) at medians of 1.7 ng/mL and 0.83 ng/mL, respectively, followed by the linear perfluorooctanoic acid (L-PFOA) found at a median concentration of 0.59 ng/mL. Overall, these three PFAS comprised 80 % of the serum ∑PFAS concentrations. A similar pattern was observed in dust with L-PFOS and L-PFOA found as the most abundant PFAS (median concentrations of 13 and 7.8 ng/g, respectively), with the overall contribution of 50 % to the ∑PFAS concentration. Only L-PFOA was found in wristbands at a median concentration of 0.02 ng/g. Significant correlations were found between the concentrations of several PFAS in dust and serum, and in dust and wristbands, suggesting that the indoor environment could be a significant contributor to the personal and internal PFAS exposures in seniors. Our findings demonstrate that residents of assisted living facilities are widely exposed to PFAS, with several PFAS found in blood of each study participant and in the assisted living environment.

Personal environmental exposure to plasticizers and organophosphate flame retardants using silicone wristbands and urine: Patterns, comparisons, and correlations

Plasticizers (PLs) and organophosphate flame retardants (OPFRs) are ubiquitous in the environment due to their widespread use and potential for leaching from consumer products. Environmental exposure is a critical aspect of the human exposome, revealing complex interactions between environmental contaminants and potential health effects. Silicone wristbands (SWBs) have emerged as a novel and non-invasive sampling device for assessing personal external exposure. In this study, SWBs were used as a proxy to estimate personal dermal adsorption (EDdermal) to PLs and OPFRs in Belgian participants for one week; four morning urine samples were also collected and analyzed for estimated daily intake (EDI). The results of the SWBs samples showed that all the participants were exposed to these chemicals, and the exposure was found to be highest for the legacy and alternative plasticizers (LP and AP), followed by the legacy and emerging OPFRs (LOPFR and EOPFR). In urine samples, the highest levels were observed for metabolites of diethyl phthalate (DEP), di-isobutyl phthalate (DiBP) and di-n-butyl phthalate (DnBP) among LPs and di(2-ethylhexyl) terephthalate (DEHT) for APs. Outliers among the participants indicated that there were other sources of exposure that were not identified. Results showed a significant correlation between EDdermal and EDI for DiBP, tris (2-butoxyethyl) phosphate (TBOEP) and triphenyl phosphate (TPhP). These correlations indicated their suitability for predicting exposure via SWB monitoring for total chemical exposure. The results of this pilot study advance our understanding of SWB sampling and its relevance for predicting aggregate environmental chemical exposures, while highlighting the potential of SWBs as low-cost, non-invasive personal samplers for future research. This innovative approach has the potential to advance the assessment of environmental exposures and their impact on public health.

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.

Perfluoroalkyl/Polyfluoroalkyl Substances: Links to Cardiovascular Disease Risk

Conservative estimates by the World Health Organization suggest that at least a quarter of global cardiovascular diseases are attributable to environmental exposures. Associations between air pollution and cardiovascular risk have garnered the most headlines and are strong, but less attention has been paid to other omnipresent toxicants in our ecosystem. Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are man-made chemicals that are extensively used in industrial and consumer products worldwide and in aqueous film-forming foam utilized in firefighting. As such, our exposure to PFAS is essentially ubiquitous. Given the long half-lives of these degradation-resistant chemicals, virtually, all people are carrying a body burden of PFAS. Health concerns related to PFAS are growing such that the National Academies of Sciences, Engineering and Medicine has recommended standards for clinical follow-up of individuals with high PFAS blood levels, including prioritizing screening for dyslipidemia. The link between PFAS and dyslipidemia has been extensively investigated, and evidence for associations is compelling. However, dyslipidemia is not the only cardiovascular risk factor with which PFAS is associated. Here, we review the epidemiological evidence for links between PFAS of concern identified by the National Academies of Sciences, Engineering and Medicine and risk factors for cardiovascular disease, including overweight/obesity, glucose intolerance, hypertension, dyslipidemia, and hyperuricemia. Moreover, we review the potential connections of PFAS with vascular disease and atherosclerosis. While observational data support associations between the National Academies of Sciences, Engineering and Medicine PFAS and selected cardiac risk factors, additional research is needed to establish causation and better understand how exposure to PFAS leads to the development of these conditions.

Quantifying 209 Polychlorinated Biphenyl Congeners in Silicone Wristbands to Evaluate Differences in Exposure among Demolition Workers

A social housing estate in Denmark was designated for demolition due to exceedance of guidance values for polychlorinated biphenyls (PCBs) in indoor air. Here, we deployed precleaned silicone wristbands (n = 46) among demolition workers of these contaminated buildings during single workdays while conducting various work tasks. We established a method to analyze all 209 PCBs in wristbands to identify prominent congeners of exposure and evaluate differences between tasks. Wristbands were extracted using microwave-assisted extraction and then concentrated for gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis. Twenty-nine chromatographic peaks representing 37 congeners were detected in every wristband, and tetra-CBs were the dominant homologue group. PCB-66, -44, and -70 were the most abundant congeners measured in worker wristbands, none of which are included within the typical seven indicator or WHO 12 PCBs. Workers who cut PCB-containing sealants had wristbands with the highest PCB concentrations (geometric mean ∑209PCBs = 1963 ng/g wristband), which were followed by those handling concrete elements on the building roof. Additionally, wristbands captured a broader range of PCBs than has been previously measured in air and serum samples. Taken together, our results highlight the importance of total congener analysis in assessing current PCB exposure in demolition work and the utility of wristbands for assessing these exposures.

Arachidonic Acid Metabolites in Self-collected Biospecimens Following Campfire Exposure: Exploring Non-invasive Biomarkers of Wildfire Health Effects

Climate change has contributed to increased frequency and intensity of wildfire. Studying its acute effects is limited due to unpredictable nature of wildfire occurrence, which necessitates readily deployable techniques to collect biospecimens. To identify biomarkers of wildfire's acute effects, we conducted this exploratory study in eight healthy campers (four men and four women) who self-collected nasal fluid, urine, saliva, and skin wipes at different time points before, during, and after 4-hour exposure to wood smoke in a camping event. Concentrations of black carbon in the air and polycyclic aromatic hydrocarbons in participants' silicone wristbands were significantly elevated during the exposure session. Among 30 arachidonic acid metabolites measured, lipoxygenase metabolites were more abundant in nasal fluid and saliva, whereas cyclooxygenase and non-enzymatic metabolites were more abundant in urine. We observed drastic increases, at 8 hours following the exposure, in urinary levels of PGE2 (398%) and 15-keto-PGF2α (191%) (FDR<10%), with greater increases in men (FDR < 0.01%) than in women. No significant changes were observed for other metabolites in urine or the other biospecimens. Our results suggest urinary PGE2 and 15-keto-PGF2α as promising biomarkers reflecting pathophysiologic (likely sex-dependent) changes induced by short-term exposure to wildfire.

Assessment of phthalate exposure at a fire site in Korean firefighters

To determine phthalate exposure in 32 firefighters, the concentrations of urinary phthalate metabolites, immediately (exposure day) and three weeks (control day) after fire suppression, were compared. Mono-(2-ethyl-5-carboxypentyl) phthalate, mono-(2-ethyl-5-hydroxyhexyl) phthalate, mono-(2-ethyl-5-oxohexyl) phthalate, mono-n-butyl phthalate (MBP), mono-n-benzyl phthalate (MBzP), and total phthalates (∑phthalates) levels, and creatinine-adjusted levels of MBP, MBzP, and ∑phthalates were significantly higher on exposure day than on control day. Phthalate concentration was significantly higher in firefighters who performed the fire extinguishing tasks (geometric mean [GM], 149.9 μg/L) than in those who performed other tasks (GM 70.8 μg/L) (p = .012). The GM concentration of firefighters who were active ≤ 50 m from the fire was 119.0 μg/L, and 37.6 μg/L for those who were > 50 m away (p = .012). The GM concentration was significantly different (p = .039) in firefighters with subjective symptoms after fire suppression (151.9 μg/L) compared to those without symptoms (81.6 μg/L). This study showed that firefighters were exposed to phthalate.

Comparison of Serum Per- and Polyfluoroalkyl Substances Concentrations in Incumbent and Recruit Firefighters and Longitudinal Assessment in Recruits

OBJECTIVE

Firefighters are occupationally exposed to per- and polyfluoroalkyl substances (PFAS). This study objective was to compare serum PFAS concentrations in incumbent and recruit firefighters and evaluate temporal trends among recruits.

METHODS

Serum PFAS concentrations were measured in 99 incumbent and 55 recruit firefighters at enrollment in 2015-2016, with follow-up 20 to 37 months later for recruits. Linear and logistic regression and linear mixed-effects models were used for analyses. Fireground exposure impact on PFAS concentrations was investigated using adjusted linear and logistic regression models.

RESULTS

Incumbents had lower n-PFOA and PFNA than recruits and most PFAS significantly decreased over time among male recruits. No significant links were found between cumulative fireground exposures and PFAS concentrations.

CONCLUSIONS

Serum PFAS concentrations were not increased in incumbent firefighters compared with recruits and were not associated with cumulative fireground exposures.

Firefighting, per- and polyfluoroalkyl substances, and DNA methylation of genes associated with prostate cancer risk

Prostate cancer is the leading incident cancer among men in the United States. Firefighters are diagnosed with this disease at a rate 1.21 times higher than the average population. This increased risk may result from occupational exposures to many toxicants, including per- and polyfluoroalkyl substances (PFAS). This study assessed the association between firefighting as an occupation in general or PFAS serum levels, with DNA methylation. Only genomic regions previously linked to prostate cancer risk were selected for analysis: GSTP1, Alu repetitive elements, and the 8q24 chromosomal region. There were 444 male firefighters included in this study, with some analyses being conducted on fewer participants due to missingness. Statistical models were used to test associations between exposures and DNA methylation at CpG sites in the selected genomic regions. Exposure variables included proxies of cumulative firefighting exposures (incumbent versus academy status and years of firefighting experience) and biomarkers of PFAS exposures (serum concentrations of 9 PFAS). Proxies of cumulative exposures were associated with DNA methylation at 15 CpG sites and one region located within FAM83A (q-value <0.1). SbPFOA was associated with 19 CpG sites (q < 0.1), but due to low detection rates, this PFAS was modeled as detected versus not detected in serum. Overall, there is evidence that firefighting experience is associated with differential DNA methylation in prostate cancer risk loci, but this study did not find evidence that these differences are due to PFAS exposures specifically.

Expanding the access of wearable silicone wristbands in community-engaged research through best practices in data analysis and integration

Wearable silicone wristbands are a rapidly growing exposure assessment technology that offer researchers the ability to study previously inaccessible cohorts and have the potential to provide a more comprehensive picture of chemical exposure within diverse communities. However, there are no established best practices for analyzing the data within a study or across multiple studies, thereby limiting impact and access of these data for larger meta-analyses. We utilize data from three studies, from over 600 wristbands worn by participants in New York City and Eugene, Oregon, to present a first-of-its-kind manuscript detailing wristband data properties. We further discuss and provide concrete examples of key areas and considerations in common statistical modeling methods where best practices must be established to enable meta-analyses and integration of data from multiple studies. Finally, we detail important and challenging aspects of machine learning, meta-analysis, and data integration that researchers will face in order to extend beyond the limited scope of individual studies focused on specific populations.

Use of silicone wristbands to measure firefighters' exposures to polycyclic aromatic hydrocarbons (PAHs) during live fire training

Firefighters experience exposures to carcinogenic and mutagenic substances, including polycyclic aromatic hydrocarbons (PAHs). Silicone wristbands (SWBs) have been used as passive samplers to assess firefighters' exposures over the course of a shift but their utility in measuring short term exposures, source of exposure, and correlations with other measurements of exposure have not yet been investigated. In this study, SWBs were used to measure the concentrations of 16 priority PAHs inside and outside of firefighters' personal protective equipment (PPE) while firefighting. SWBs were placed on the wrist and jacket of 20 firefighters conducting live fire training. Correlations were made with matching data from a sister project that measured urinary concentrations of PAH metabolites and PAH concentrations from personal air samples from the same participants. Naphthalene, acenaphthylene and phenanthrene had the highest geometric mean concentrations in both jacket and wrist SWB, with 1040, 320, 180 ng/g SWB for jacket and 55.0, 4.9, and 6.0 ng/g SWB for wrist, respectively. Ratios of concentrations between the jacket and wrist SWBs were calculated as worker protection factors (WPFs) and averaged 40.1 for total PAHs and ranged from 2.8 to 214 for individual PAHs, similar to previous studies. Several significant correlations were observed between PAHs in jacket SWBs and air samples (e.g., total and low molecular weight PAHs, r = 0.55 and 0.59, p < 0.05, respectively). A few correlations were found between PAHs from SWBs worn on the wrist and jacket, and urinary concentrations of PAH metabolites and PAH concentrations in air samples. The ability of the SWBs to accurately capture exposures to various PAHs was likely influenced by short sampling time, high temperatures, and high turbulence. Future work should further examine the limitations of SWBs for PAH exposures in firefighting, and other extreme environments.

Expanding the access of wearable silicone wristbands in community-engaged research through best practices in data analysis and integration

Wearable silicone wristbands are a rapidly growing exposure assessment technology that offer researchers the ability to study previously inaccessible cohorts and have the potential to provide a more comprehensive picture of chemical exposure within diverse communities. However, there are no established best practices for analyzing the data within a study or across multiple studies, thereby limiting impact and access of these data for larger meta-analyses. We utilize data from three studies, from over 600 wristbands worn by participants in New York City and Eugene, Oregon, to present a first-of-its-kind manuscript detailing wristband data properties. We further discuss and provide concrete examples of key areas and considerations in common statistical modeling methods where best practices must be established to enable meta-analyses and integration of data from multiple studies. Finally, we detail important and challenging aspects of machine learning, meta-analysis, and data integration that researchers will face in order to extend beyond the limited scope of individual studies focused on specific populations.

Measuring semi-volatile organic compound exposures during pregnancy using silicone wristbands

Silicone wristbands were utilized as personal passive samplers in a sub-cohort of 92 women, who participated in New York University Children's Health and Environment Study, to assess exposure to semi-volatile organic compounds (SVOCs). Wristbands were analyzed for 77 SVOCs, including halogenated and non-halogenated organophosphate esters (OPEs), polychlorinated biphenyls (PCBs), pesticides, phthalates, and brominated flame retardants (BFRs) (e.g. polybrominated diphenyl ethers (PBDEs)). This study aimed to look for patterns in chemical exposure utilizing participant demographics gathered from a questionnaire, and chemical exposure data across multiple timepoints during pregnancy. Analysis focused on 27 compounds detected in at least 80% of the wristbands examined. The chemicals detected most frequently included two pesticides, eight phthalates, one phthalate alternative, seven BFRs, and nine OPEs, including isopropylated and tert-butylated triarylphosphate esters (ITPs and TBPPs). Co-exposure to different SVOCs was most prominent in compounds that were within the same chemical class or were used in similar consumer applications such as phthalates and OPEs, which are often used as plasticizers. Pre-pregnancy BMI was positively associated with multiple compounds, and there were both positive and negative associations between women's parity and SVOC exposure. Outdoor temperature was not correlated with the wristband concentrations over a five-day sampling period. Lastly, significant and moderately high Intraclass Correlation Coefficient (ICC) (0.66-0.84) values for phthalate measurementsacross pregnancy indicate chronic exposure and suggest that using wristbands during one sampling period may reliably predict exposure. However, multiple sampling periods may be necessary to accurately determine indoor exposure to other SVOCs including OPEs and BFRs.

Balancing Acute and Chronic Occupational Risks: The Use of Nitrile Butadiene Rubber Undergloves by Firefighters to Reduce Exposure to Toxic Contaminants

Firefighters are exposed via multi-route exposure to a multitude of chemicals (PAHs, VOCs, flame retardants, dioxins, etc.) that may cause acute and long-term health effects. The dermal absorption of contaminants is a major contributor to the overall exposure and can be reduced by wearing appropriate personal protective equipment. As leather firefighters' gloves cannot be decontaminated regularly by wet cleaning, many Belgian firefighters wear supplementary undergloves made of nitrile butadiene rubber (NBR) to protect against the accumulation of toxicants. However, the safety of this practice has been questioned. In this commentary, the current practice and risks are outlined for the first time, assessed by an interdisciplinary working group of the Belgian Superior Health Council. As NBR sticks to the skin more at high temperatures, the contact time on removal will be prolonged, posing an additional risk for deeper burns. However, based on the physicochemical properties of NBR and the existing experience of firefighters and burn centers, it is estimated that such incidents occur relatively rarely in practice. On the other hand, the risk of repeated exposure to contaminated gloves if no undergloves are worn is unacceptable. Despite the slightly increased risk for deeper burns, it is concluded that wearing disposable NBR gloves under regular firefighters' gloves is an appropriate and effective preventive measure against toxic contamination. The nitrile butadiene rubber must always be fully covered to avoid any contact with the heat.

Silicone passive sampling used to identify novel dermal chemical exposures of firefighters and assess PPE innovations

A plethora of chemicals are released into the air during combustion events, including a class of compounds called polycyclic aromatic hydrocarbons (PAHs). PAHs have been implicated in increased risk of cancer and cardiovascular disease, both of which are disease endpoints of concern in structural firefighters. Current commercially available personal protective equipment (PPE) typically worn by structural firefighters during fire responses have gaps in interfaces between the ensemble elements (e.g., hood and jacket) that allow for ingress of contaminants and dermal exposure. This pilot study aims to use silicone passive sampling to assess improvements in dermal protection afforded by a novel configuration of PPE, which incorporates a one-piece liner to eliminate gaps in two critical interfaces between pieces of gear. The study compared protection against parent and alkylated PAHs between the one-piece liner PPE and the standard configuration of PPE with traditional firefighting jacket and pants. Mannequins (n = 16) dressed in the PPE ensembles were placed in a Fireground Exposure Simulator for 10 min, and exposed to smoke from a combusting couch. Silicone passive samplers were placed underneath PPE at vulnerable locations near interfaces in standard PPE, and in the chamber air, to measure PAHs and calculate the dermal protection provided by both types of PPE. Silicone passive sampling methodology and analyses using gas chromatography with mass-spectrometry proved to be well-suited for this intervention study, allowing for the calculation and comparison of worker protection factors for 51 detected PAHs. Paired comparisons of the two PPE configurations found greater sum 2-3 ring PAH exposure underneath the standard PPE than the intervention PPE at the neck and chest, and at the chest for 4-7 ring PAHs (respective p-values: 0.00113, 0.0145, and 0.0196). Mean worker protection factors of the intervention PPE were also greater than the standard PPE for 98% of PAHs at the neck and chest. Notably, the intervention PPE showed more than 30 times the protection compared to the standard PPE against two highly carcinogenic PAHs, dibenzo[a,l]pyrene and benzo[c]fluorene. Nine of the detected PAHs in this study have not been previously reported in fireground exposure studies, and 26 other chemicals (not PAHs) were detected using a large chemical screening method on a subset of the silicone samplers. Silicone passive sampling appears to be an effective means for measuring dermal exposure reduction to fireground smoke, providing evidence in this study that reducing gaps in PPE interfaces could be further pursued as an intervention to reduce dermal exposure to PAHs, among other chemicals.

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.

Serum per- and polyfluoroalkyl substance concentrations in four municipal US fire departments

BACKGROUND

Firefighters have occupational and environmental exposures to per- and polyfluoroalkyl substances (PFAS). The goal of this study was to compare serum PFAS concentrations across multiple United States fire departments to National Health and Nutrition Examination Survey (NHANES) participants.

METHODS

Nine serum PFAS were compared in 290 firefighters from four municipal fire departments (coded A-D) and three NHANES participants matched to each firefighter on sex, ethnicity, age, and PFAS collection year. Only Departments A and C had sufficient women study participants (25 and six, respectively) to compare with NHANES.

RESULTS

In male firefighters compared with NHANES, geometric mean perfluorohexane sulfonate (PFHxS) was elevated in Departments A-C, sum of branched perfluoromethylheptane sulfonate isomers (Sm-PFOS) was elevated in all four departments, linear perfluorooctane sulfonate (n-PFOS) was elevated in Departments B and C, linear perfluorooctanoate (n-PFOA) was elevated in Departments B-D, and perfluorononanoate (PFNA) was elevated in Departments B-D, but lower in A. In male firefighters compared with NHANES, perfluoroundecanoate (PFUnDA) was more frequently detected in Departments B and D, and 2-(N-methyl-perfluorooctane sulfonamido) acetate (MeFOSAA) was less frequently detected in Departments B-D. In female firefighters compared with NHANES, PFHxS and Sm-PFOS concentrations were elevated in Departments A and C. Other PFAS concentrations were elevated and/or reduced in only one department or not significantly different from NHANES in any department.

CONCLUSIONS

Serum PFHxS, Sm-PFOS, n-PFOS, n-PFOA, and PFNA concentrations were increased in at least two of four fire departments in comparison to NHANES.