Last data update: Jan 27, 2025. (Total: 48650 publications since 2009)
Records 1-25 (of 25 Records) |
Query Trace: Chen IC[original query] |
---|
Evaluating the ingress of total polycyclic aromatic hydrocarbons (PAHs) specifically naphthalene through firefighter hoods and base layers
Kander MC , Wilkinson AF , Chen IC , Bertke S , Kesler RM , Smith DL , Horn GP , Fent KW . J Occup Environ Hyg 2025 1-9 Structural firefighters are exposed to an array of polycyclic aromatic hydrocarbons (PAHs) as a result of incomplete combustion of both synthetic and natural materials. PAHs are found in both the particulate and vapor phases in the firefighting environment and are significantly associated with acute and chronic diseases, including cancer. Using a fireground exposure simulator (FES) and standing mannequins dressed in four different firefighter personal protective equipment (PPE) conditions, each with varying levels of protective hood interface and particulate-blocking features, the efficacy of the hoods was assessed against the ingress of PAHs (specifically, naphthalene). The authors also explored the effectiveness of a 100% cotton turtleneck at further attenuating the amount of naphthalene reaching the surface of the mannequin's neck. Air samples were collected at the breathing zone, abdomen, and thigh heights from the 6 ft-2 in mannequins used in this study. Naphthalene was the most abundant PAH (55% of the total PAH concentrations) in the FES and existed primarily in the vapor phase (92% vapor in the breathing zone). Additionally, bulk base layer and under the base layer polytetrafluoroethylene (PTFE) filter samples (used as skin surrogates) were collected from the neck region of the mannequins and analyzed for PAHs. A larger percentage of naphthalene was collected on the filter under the traditional knit hoods than on the cotton base layer, suggesting a small protective effect of the base layer against solid-phase naphthalene. Previous studies investigating naphthalene by employing air sampling under PPE have found a larger protective effect of base layers against the ingress of naphthalene vapor. PAHs that exist primarily as particulate in the fire environment were largely not detected on the base layers or PTFE filters under the gear. Further research is needed that involves more sensitive methods and non-static human subjects. |
Quantile regression for longitudinal data with values below the limit of detection and time-dependent covariates-application to modeling carbon nanotube and nanofiber exposures
Chen IC , Bertke SJ , Dahm MM . Ann Work Expo Health 2024 BACKGROUND: In studies of occupational health, longitudinal environmental exposure, and biomonitoring data are often subject to right skewing and left censoring, in which measurements fall below the limit of detection (LOD). To address right-skewed data, it is common practice to log-transform the data and model the geometric mean, assuming a log-normal distribution. However, if the transformed data do not follow a known distribution, modeling the mean of exposure may result in bias and reduce efficiency. In addition, when examining longitudinal data, it is possible that certain covariates may vary over time. OBJECTIVE: To develop predictive quantile regression models to resolve the issues of left censoring and time-dependent covariates and to quantitatively evaluate if previous and current covariates can predict current and/or future exposure levels. METHODS: To address these gaps, we suggested incorporating different substitution approaches into quantile regression and utilizing a method for selecting a working type of time dependency for covariates. RESULTS: In a simulation study, we demonstrated that, under different types of time-dependent covariates, the approach of multiple random value imputation outperformed the other approaches. We also applied our methods to a carbon nanotube and nanofiber exposure study. The dependent variables are the left-censored mass of elemental carbon at both the respirable and inhalable aerosol size fractions. In this study, we identified some potential time-dependent covariates with respect to worker-level determinants and job tasks. CONCLUSION: Time dependency for covariates is rarely accounted for when analyzing longitudinal environmental exposure and biomonitoring data with values less than the LOD through predictive modeling. Mistreating the time-dependency as time-independency will lead to an efficiency loss of regression parameter estimation. Therefore, we addressed time-varying covariates in longitudinal exposure and biomonitoring data with left-censored measurements and illustrated an entire conditional distribution through different quantiles. |
Biomarkers of organophosphate and polybrominated diphenyl ether (PBDE) flame retardants of American workers and associations with inhalation and dermal exposures
Estill CF , Mayer AC , Chen IC , Slone J , LaGuardia MJ , Jayatilaka N , Ospina M , Sjodin A , Calafat AM . Environ Sci Technol 2024 This study evaluated workers' exposures to flame retardants, including polybrominated diphenyl ethers (PBDEs), organophosphate esters (OPEs), and other brominated flame retardants (BFRs), in various industries. The study aimed to characterize OPE metabolite urinary concentrations and PBDE serum concentrations among workers from different industries, compare these concentrations between industries and the general population, and evaluate the likely route of exposure (dermal or inhalation). The results showed that workers from chemical manufacturing had significantly higher (p <0.05) urinary concentrations of OPE metabolites compared to other industries. Spray polyurethane foam workers had significantly higher (p <0.05) urinary concentrations of bis(1-chloro-2-propyl) phosphate (BCPP) compared to other industries. Electronic scrap workers had higher serum concentrations of certain PBDE congeners compared to the general population. Correlations were observed between hand wipe samples and air samples containing specific flame-retardant parent chemicals and urinary metabolite concentrations for some industries, suggesting both dermal absorption and inhalation as primary routes of exposure for OPEs. Overall, this study provides insights into occupational exposure to flame retardants in different industries and highlights the need for further research on emerging flame retardants and exposure reduction interventions. |
Compare the marginal effects for environmental exposure and biomonitoring data with repeated measurements and values below the limit of detection
Chen IC , Bertke SJ , Estill CF . J Expo Sci Environ Epidemiol 2024 BACKGROUND: Environmental exposure and biomonitoring data with repeated measurements from environmental and occupational studies are commonly right-skewed and in the presence of limits of detection (LOD). However, existing model has not been discussed for small-sample properties and highly skewed data with non-detects and repeated measurements. OBJECTIVE: Marginal modeling provides an alternative to analyzing longitudinal and cluster data, in which the parameter interpretations are with respect to marginal or population-averaged means. METHODS: We outlined the theories of three marginal models, i.e., generalized estimating equations (GEE), quadratic inference functions (QIF), and generalized method of moments (GMM). With these approaches, we proposed to incorporate the fill-in methods, including single and multiple value imputation techniques, such that any measurements less than the limit of detection are assigned values. RESULTS: We demonstrated that the GEE method works well in terms of estimating the regression parameters in small sample sizes, while the QIF and GMM outperform in large-sample settings, as parameter estimates are consistent and have relatively smaller mean squared error. No specific fill-in method can be deemed superior as each has its own merits. IMPACT: Marginal modeling is firstly employed to analyze repeated measures data with non-detects, in which only the mean structure needs to be correctly provided to obtain consistent parameter estimates. After replacing non-detects through substitution methods and utilizing small-sample bias corrections, in a simulation study we found that the estimating approaches used in the marginal models have corresponding advantages under a wide range of sample sizes. We also applied the models to longitudinal and cluster working examples. |
Laboratory Study of Physical Barrier Efficiency for Worker Protection against SARS-CoV-2 while Standing or Sitting (preprint)
Bartels J , Estill CF , Chen IC , Neu D . medRxiv 2021 2021.07.26.21261146 Transparent barriers were installed as a response to the SARS-COV-2 pandemic in many customer-facing industries. Transparent barriers are an engineering control that are utilized to intercept air traveling between customers to workers. Information on the effectiveness of these barriers against aerosols is limited. In this study, a cough simulator was used to represent a cough from a customer. Two optical particle counters were used (one on each side of the barrier, labeled reference and worker) to determine the number of particles that migrated around a transparent barrier. Nine barrier sizes and a no barrier configuration were tested with six replicates each. Tests of these 10 configurations were conducted for both sitting and standing scenarios to represent configurations common to nail salons and grocery stores, respectively. Barrier efficiency was calculated using a ratio of the particle count results (reference/worker). Barriers had better efficiency when they were 9 to 39 cm (3.5 to 15.5”) above cough height and at least 91 cm (36”) wide, 92% and 93% respectively. Barriers that were 91 cm (36”) above table height for both scenarios blocked 71% or more of the particles between 0.35–0.725 µm and 68% for particles between 1 to 3 µm. A barrier that blocked an initial cough was effective at reducing particle counts. While the width of barriers was not as significant as height in determining barrier efficiency it was important that a barrier be placed where interactions between customers and workers are most frequent.Competing Interest StatementThe authors have declared no competing interest.Funding StatementThis research was funded by the CDC. NIOSH is a part of the CDCAuthor DeclarationsI confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.YesThe details of the IRB/oversight body that provided approval or exemption for the research described are given below:NIOSH Institutional Review BoardAll necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived.YesI understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).YesI have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable.YesAll the data that has been tabulated in the manuscript can be provided in a more accessible format. |
Maternal occupational exposure to selected organic and chlorinated solvents and delivery of small-for-gestational age or preterm infants
Van Buren KW , Rocheleau CM , Chen IC , Desrosiers TA , Sanderson WT , Politis MD , Ailes EC . Am J Ind Med 2023 66 (10) 842-853 BACKGROUND: Potential reproductive effects of organic solvent exposure during pregnancy remain unclear. We investigated the association between maternal occupational exposure during pregnancy to six chlorinated solvents, three aromatic solvents, and Stoddard solvent, and delivery of preterm infants or those born small-for-gestational age (SGA). METHODS: In this case-control study of SGA and preterm birth (PTB) nested within the National Birth Defects Prevention Study (NBDPS) from 1997 to 2011, we analyzed data from 7504 singleton live births without major birth defects and their mothers. Self-reported information on jobs held in the periconceptional period was assessed for solvent exposure. Unconditional logistic regression was used to estimate the association between maternal occupational exposure (any, none) during early pregnancy to organic solvents and PTB and SGA. Linear regression was used to examine changes in mean birthweight potentially associated with maternal occupational solvent exposure. RESULTS: Maternal occupational exposure to any organic solvents overall was not associated with an increased odds of PTB (adjusted odds ratio [aOR] = 0.94; 95% confidence interval [CI] 0.67-1.33) or SGA (aOR = 0.93; 95% CI 0.65-1.34). Point estimates increased modestly for higher estimated exposure versus lower, but confidence intervals were wide and not statistically significant. Maternal exposure to solvents was not associated with a statistically significant change in term birthweight among infants. CONCLUSIONS: Occupational exposure to organic solvents at the frequency and intensity levels found in a population-based sample of pregnant workers was not associated with PTB or SGA; however, we cannot rule out any effects among pregnant workers with uncommonly high exposure to organic solvents. |
Evaluating exposure to VOCs and naphthalene for firefighters wearing different ppe configurations through measures in air, exhaled breath, and urine
Mayer AC , Fent KW , Wilkinson AF , Chen IC , Siegel MR , Toennis C , Sammons D , Meadows J , Kesler RM , Kerber S , Smith DL , Masoud F , Bhandari D , Wang Y , Blount BC , Calafat AM , Horn GP . Int J Environ Res Public Health 2023 20 (12) Firefighters are at an increased risk of cancer due to their occupational exposure to combustion byproducts, especially when those compounds penetrate the firefighter personal protective equipment (PPE) ensemble. This has led to questions about the impact of base layers (i.e., shorts vs. pants) under PPE ensembles. This study asked 23 firefighters to perform firefighting activities while wearing one of three different PPE ensembles with varying degrees of protection. Additionally, half of the firefighters unzipped their jackets after the scenario while the other half kept their jackets zipped for five additional minutes. Several volatile organic compound (VOC) and naphthalene air concentrations outside and inside of hoods, turnout jackets, and turnout pants were evaluated; biological (urinary and exhaled breath) samples were also collected. VOCs and naphthalene penetrated the three sampling areas (hoods, jackets, pants). Significant (p-value < 0.05) increases from pre- to post-fire for some metabolites of VOCs (e.g., benzene, toluene) and naphthalene were found. Firefighters wearing shorts and short sleeves absorbed higher amounts of certain compounds (p-value < 0.05), and the PPE designed with enhanced interface control features appeared to provide more protection from some compounds. These results suggest that firefighters can dermally absorb VOCs and naphthalene that penetrate the PPE ensemble. |
Use of preliminary exposure reduction practices or laundering to mitigate polycyclic aromatic hydrocarbon contamination on firefighter personal protective equipment ensembles
Wilkinson AF , Fent KW , Mayer AC , Chen IC , Kesler RM , Kerber S , Smith DL , Horn GP . Int J Environ Res Public Health 2023 20 (3) Chronic health risks associated with firefighting continue to be documented and studied, however, the complexity of occupational exposures and the relationship between occupational exposure and contaminated personal protective equipment (PPE) remains unknown. Recent work has revealed that common PPE cleaning practices, which are becoming increasingly more common in the fire service, are not effective in removing certain contaminants, such as polycyclic aromatic hydrocarbons (PAHs), from PPE. To better understand the relationship between contaminated firefighter PPE and potential exposure to PAHs, and to gain further understanding of the efficacy of cleaning practices, we used a standardized fire exposure simulator that created repeatable conditions and measured PPE surface contamination levels via wipe sampling and filters attached to firefighter gear worn by standing mannequins. This study examined the effects of repeated (40 cycles) PPE cleaning (laundering and on-scene preliminary exposure reduction (PER) techniques) and repeated exposures on PAH concentration on different surfaces. Further exploration included examination of contamination breakthrough of turnout jackets (comparing outer shell and interior liner) and evaluation of off-gassing PAHs from used gear after different cleaning treatments. When compared by jacket closure type (zipper and hook and dee), total PAH concentration wiped from gear after exposure and cleanings showed no significant differences. Regression analysis indicated that there was no effect of repeated exposures on PAH contamination levels (all sampling sites combined; before fire 10, 20, and 40; after fire 1, 10, 20, and 40; p-value > 0.05). Both laundering and on-scene PER significantly reduced contamination levels on the exterior pants and helmets and were effective at reducing PAH contamination. The jacket outer shell had significantly higher PAH contamination than the jacket liner. Both laundering and wet soap PER methods (post-fire) are effective in reducing surface contamination and appear to prevent accumulation of contamination after repeated exposures. Semi-volatile PAHs deep within the fibers of bulky PPE are not effectively reduced via PER or machine laundering, therefore, permitting continued off-gassing of these compounds. Further research is needed to identify the most effective laundering methods for firefighter turnout gear that considers the broad spectrum of common contaminants. |
Exposure assessment of polycyclic aromatic hydrocarbons in refined coal tar sealant applications
McCormick S , Snawder JE , Chen IC , Slone J , Calafat AM , Wang Y , Meng L , Alexander-Scott M , Breitenstein M , Johnson B , Meadows J , Fairfield Estill C . Int J Hyg Environ Health 2022 242 113971 BACKGROUND: Refined coal tar sealant (RCTS) emulsions are used to seal the surface of asphalt pavement. Nine of the 22 polycyclic aromatic hydrocarbons (PAHs) evaluated in this study are classified as known, probable, or possible human carcinogens. Exposure assessment research for RCTS workers has not been published previously. OBJECTIVES: The overall objective of this study was to develop a representative occupational exposure assessment of PAH exposure for RCTS workers based on worksite surveys. The specific aims were to: 1) quantify full-shift airborne occupational exposures to PAHs among RCTS workers; 2) quantify workers' dermal exposures to PAHs; 3) quantify biomarkers of PAH exposure in workers' urine; 4) identify specific job titles associated with RCTS exposure; and 5) apply these results to a biological exposure index to assess risk of potential genotoxicity from occupational exposures. METHODS: A total of twenty-one RCTS workers were recruited from three companies. Personal and area air samples were collected using a modification of NIOSH Method 5515. Dermal exposure was assessed by hand and neck wipes before and after shifts. Twenty-two PAHs were quantified via gas chromatography-mass spectrometry selected ion monitoring. Internal dose was estimated by quantifying select PAH metabolites in pre- and post-shift urine samples using on-line solid phase extraction-high performance liquid chromatography-tandem mass spectrometry. RESULTS: PAH levels in the worker breathing zones were highest for naphthalene, acenaphthene, and phenanthrene, with geometric means of 52.1, 11.4, and 9.8 μg/m(3), respectively. Hand wipe levels of phenanthrene, fluoranthene and pyrene were the highest among the 22 PAHs with geometric means of 7.9, 7.7, and 5.5 μg/cm(2), respectively. Urinary PAH biomarkers for naphthalene, fluorene, phenanthrene, and pyrene were detected in all workers and were higher for post-shift samples than those collected pre-shift. Urinary concentrations of the metabolite 1-hydroxypyrene were greater than the American Conference of Governmental Industrial Hygienists (ACGIH) Biological Exposure Index (BEI) for this metabolite in 89 percent of post-shift samples collected on the final day of the work week or field survey. Statistically significances were found between concentrations of fluorene, naphthalene, and phenanthrene in the breathing zone of workers and their corresponding urinary PAH biomarkers. Workers were placed in two work place exposure groups: applicators and non-applicators. Applicators had higher total PAH concentrations in personal breathing zone (PBZ) air samples than non-applicators and were more likely to have post-shift hand wipe concentrations significantly higher than pre-shift concentrations. Concentrations of post-shift urinary biomarkers were higher, albeit not significantly, for applicators than non-applicators. CONCLUSIONS: The exposure results from RCTS worker samples cannot be explained by proximal factors such as nearby restaurants or construction. Air and skin concentration levels were substantially higher for RCTS workers than previously published levels among asphalt workers for all PAHs. PAH profiles on skin wipes were more consistent with RCTS sealant product than air samples. Last day post-shift urinary concentrations of 1-hydroxypyrene greatly exceeded the ACGIH BEI benchmark of 2.5 μg/L in 25 of 26 samples, which suggests occupational exposure and risk of genotoxicity. When pyrene and benzo[a]pyrene were both detected, concentration ratios from personal exposure samples were used to calculate the adjusted BEI. Concentrations of 1-hydroxypyrene exceeded the adjusted BEIs for air, hand wipes, and neck wipes in most cases. These results indicate the need to increase safety controls and exposure mitigation for RCTS workers. |
Firefighters' urinary concentrations of VOC metabolites after controlled-residential and training fire responses
Fent KW , Mayer AC , Toennis C , Sammons D , Robertson S , Chen IC , Bhandari D , Blount BC , Kerber S , Smith DL , Horn GP . Int J Hyg Environ Health 2022 242 113969 INTRODUCTION: Firefighters are exposed to volatile organic compounds (VOCs) during structural fire responses and training fires, several of which (e.g., benzene, acrolein, styrene) are known or probable carcinogens. Exposure studies have found that firefighters can absorb chemicals like benzene even when self-contained breathing apparatus (SCBA) are worn, suggesting that dermal absorption contributes to potentially harmful exposures. However, few studies have characterized VOC metabolites in urine from firefighters. OBJECTIVES: We quantified VOC metabolites in firefighters' urine following live firefighting activity across two field studies. METHODS: In two separate controlled field studies, spot urine was collected before and 3 h after firefighters and firefighter students responded to simulated residential and training fires. Urine was also collected from instructors from the training fire study before the first and 3 h after the last training scenario for each day (instructors led three training scenarios per day). Samples were analyzed for metabolites of VOCs to which firefighters may be exposed. RESULTS: In the residential fire study, urinary metabolites of xylenes (2MHA), toluene (BzMA), and styrene (MADA) increased significantly (at 0.05 level) from pre- to post-fire. In the training fire study, MADA concentrations increased significantly from pre- to post-fire for both firefighter students and instructors. Urinary concentrations of benzene metabolites (MUCA and PhMA) increased significantly from pre- to post-fire for instructors, while metabolites of xylenes (3MHA+4MHA) and acrolein (3HPMA) increased significantly for firefighter students. The two highest MUCA concentrations measured post-shift from instructors exceeded the BEI of 500 μg/g creatinine. CONCLUSIONS: Some of the metabolites that were significantly elevated post-fire are known or probable human carcinogens (benzene, styrene, acrolein); thus, exposure to these compounds should be eliminated or reduced as much as possible through the hierarchy of controls. Given stringent use of SCBA, it appears that dermal exposure contributes in part to the levels measured here. |
Reliability and validity of an employer-completed safety hazard and management assessment questionnaire
Moore LL , Wurzelbacher SJ , Chen IC , Lampl MP , Naber SJ . J Safety Res 2022 81 283-296 Introduction: Managing and improving occupational safety and health requires evaluating performance. Organizations are encouraged to use both lagging indicators (such as injury rates and costs) and leading indicators (such as questionnaire-assessed safety hazards and management practices) for this purpose, but the association between types of indicators over time can be complex. Longitudinal data can assist in clarifying these associations and increasing indicator utility. Method: Employer data were used to evaluate the reliability and predictive validity of a safety management questionnaire. Employers’ longitudinal questionnaire responses and workers’ compensation (WC) claims data were analyzed using a marginal model with time-dependent covariates. Multivariable Poisson and linear regression analyses with claim rate and logarithmic cost, respectively, as dependent variables were carried out after adjusting for industry sector and size. Questionnaire data were used to evaluate questionnaire scaling properties and to assess generalizability of results. Results: One safety management scale was associated with a better WC outcome as predicted and two scales were unexpectedly associated with poorer WC claim outcomes. Analyses assisted in interpreting the latter results, suggesting that WC outcomes were a stimulus for change in some cases. Twelve hazards assessed on the questionnaire were associated with poorer WC claim outcomes as predicted. Conclusions: This study extends leading indicator research using longitudinal questionnaire and WC claims data from employers. Analyses provided insight into associations between leading and lagging indicators, emphasizing the importance of both for safety improvement. Safety management questionnaire scales were predictive of WC claim outcomes, although support for hazard assessments as leading indicators was stronger. Practical Applications: This study supports the use of employer-completed hazard assessment questionnaires for targeting and prioritizing improvement efforts. Employer-completed safety management scales may be useful for directing improvement efforts, although the conditions under which they are completed, including submission to insurers, require additional consideration. © 2022 |
Laboratory study of physical barrier efficiency for worker protection against SARS-CoV-2 while standing or sitting.
Bartels J , Estill CF , Chen IC , Neu D . Aerosol Sci Technol 2021 56 (3) 295-303 Transparent barriers were installed as a response to the SARS-COV-2 pandemic in many customer-facing industries. Transparent barriers are an engineering control that intercept particles traveling between customers and workers. Information on the effectiveness of these barriers against aerosols is limited. In this study, a cough simulator was used to represent a cough from a customer. Two optical particle counters were used (one on each side of the barrier, labeled customer and worker) to determine the number of particles that migrated around a transparent barrier. Ten configurations were tested with six replicates for both sitting and standing scenarios, representing nail salons and grocery stores, respectively. Barrier efficiency was calculated using a ratio of the particle count results (customer/worker). Barriers had better efficiency (up to 93%) when its top was 9 to 39 cm above cough height and its width was at least 91 cm. Barriers that extended 91 cm above table height for both scenarios blocked 71% or more of the particles between 0.35–0.725 µm and 68% for particles between 1 to 3 µm. A barrier that blocked an initial cough was effective at reducing particle counts. While the width of the barriers was not as significant as the height in determining barrier efficiency it is important that a barrier be placed where interactions between customers and workers are most frequent. Bystander exposure was not taken into consideration along with other limitations. © 2022 The Author(s). Published with license by Taylor and Francis Group, LLC. |
Characterizing exposure to benzene, toluene, and naphthalene in firefighters wearing different types of new or laundered PPE
Mayer AC , Fent KW , Wilkinson A , Chen IC , Kerber S , Smith DL , Kesler RM , Horn GP . Int J Hyg Environ Health 2021 240 113900 The fire service has become more aware of the potential for adverse health outcomes due to occupational exposure to hazardous combustion byproducts. Because of these concerns, personal protective equipment (PPE) manufacturers have developed new protection concepts like particulate-blocking hoods to reduce firefighters' exposures. Additionally, fire departments have implemented exposure reduction interventions like routine laundering of PPE after fire responses. This study utilized a fireground exposure simulator (FES) with 24 firefighters performing firefighting activities on three consecutive days wearing one of three PPE ensembles (stratified by hood design and treatment of PPE): 1) new knit hood, new turnout jacket and new turnout pants 2) new particulate-blocking hood, new turnout jacket and new turnout pants or 3) laundered particulate-blocking hood, laundered turnout jacket and laundered turnout pants. As firefighters performed the firefighting activities, personal air sampling on the outside and inside the turnout jacket was conducted to quantify exposures to volatile organic compounds (VOCs) and naphthalene. Pre- and immediately post-fire exhaled breath samples were collected to characterize the absorption of VOCs. Benzene, toluene, and naphthalene were found to diffuse through and/or around the turnout jacket, as inside jacket benzene concentrations were often near levels reported outside the turnout jacket (9.7-11.7% median benzene reduction from outside the jacket to inside the jacket). The PPE ensemble did not appear to affect the level of contamination found inside the jacket for the compounds evaluated here. Benzene concentrations in exhaled breath increased significantly from pre to post-fire for all three groups (p-values < 0.05). The difference of pre-to post-fire benzene exhaled breath concentrations were positively associated with inside jacket and outside jacket benzene concentrations, even though self-contained breathing apparatus (SCBA) were worn during each response. This suggests the firefighters can absorb these compounds via the dermal route. |
Exposure to particulate matter and estimation of volatile organic compounds across wildland firefighter job tasks
Navarro KM , West MR , O'Dell K , Sen P , Chen IC , Fischer EV , Hornbrook RS , Apel EC , Hills AJ , Jarnot A , DeMott P , Domitrovich JW . Environ Sci Technol 2021 55 (17) 11795-11804 Wildland firefighters are exposed to smoke-containing particulate matter (PM) and volatile organic compounds (VOCs) while suppressing wildfires. From 2015 to 2017, the U.S. Forest Service conducted a field study collecting breathing zone measurements of PM(4) (particulate matter with aerodynamic diameter ≤4 μm) on wildland firefighters from different crew types and while performing various fire suppression tasks on wildfires. Emission ratios of VOC (parts per billion; ppb): PM(1) (particulate matter with aerodynamic diameter ≤1 μm; mg/m(3)) were calculated using data from a separate field study conducted in summer 2018, the Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE-CAN) Campaign. These emission ratios were used to estimate wildland firefighter exposure to acrolein, benzene, and formaldehyde. Results of this field sampling campaign reported that exposure to PM(4) and VOC varied across wildland firefighter crew type and job task. Type 1 crews had greater exposures to both PM(4) and VOCs than type 2 or type 2 initial attack crews, and wildland firefighters performing direct suppression had statistically higher exposures than those performing staging and other tasks (mean differences = 0.82 and 0.75 mg/m(3); 95% confidence intervals = 0.38-1.26 and 0.41-1.08 mg/m(3), respectively). Of the 81 personal exposure samples collected, 19% of measured PM(4) exposures exceeded the recommended National Wildland Fire Coordinating Group occupational exposure limit (0.7 mg/m(3)). Wildland fire management should continue to find strategies to reduce smoke exposures for wildland firefighters. |
Maternal occupation as a nail technician or hairdresser during pregnancy and birth defects, National Birth Defects Prevention Study, 1997-2011
Siegel MR , Rocheleau CM , Broadwater K , Santiago-Colón A , Johnson CY , Herdt ML , Chen IC , Lawson CC . Occup Environ Med 2021 79 (1) 17-23 OBJECTIVE: Nail technicians and hairdressers may be exposed to chemicals with potential reproductive effects. While studies have examined birth defects in children of hairdressers, those in children of nail technicians have not been evaluated. We investigated associations between selected birth defects and maternal occupation as a nail technician or hairdresser versus a non-cosmetology occupation during pregnancy. METHODS: We analysed population-based case-control data from the multisite National Birth Defects Prevention Study, 1997-2011. Cases were fetuses or infants with major structural birth defects; controls were live-born infants without major birth defects. Expert raters classified self-reported maternal jobs as nail technician, combination nail technician-hairdresser, hairdresser, other cosmetology work or non-cosmetology work. We used logistic regression to calculate adjusted ORs and 95% CIs for associations between occupation during pregnancy and birth defects, controlling for age, smoking, education and race/ethnicity. RESULTS: Sixty-one mothers worked as nail technicians, 196 as hairdressers, 39 as combination nail technician-hairdressers and 42 810 as non-cosmetologists. The strongest associations among nail technicians included seven congenital heart defect (CHD) groups (ORs ranging from 2.7 to 3.5) and neural tube defects (OR=2.6, CI=0.8 to 8.4). Birth defects most strongly associated with hairdressing included anotia/microtia (OR=2.1, CI=0.6 to 6.9) and cleft lip with cleft palate (OR=2.0, CI=1.1 to 3.7). All oral cleft groups were associated with combination nail technician-hairdresser work (ORs ranging from 4.2 to 5.3). CONCLUSIONS: Small samples resulted in wide CIs. Still, results suggest associations between maternal nail technician work during pregnancy and CHDs and between hairdressing work and oral clefts. |
Characterizing exposures to flame retardants, dioxins, and furans among firefighters responding to controlled residential fires
Mayer AC , Fent KW , Chen IC , Sammons D , Toennis C , Robertson S , Kerber S , Horn GP , Smith DL , Calafat AM , Ospina M , Sjodin A . Int J Hyg Environ Health 2021 236 113782 Firefighters may encounter items containing flame retardants (FRs), including organophosphate flame retardants (OPFRs) and polybrominated diphenyl ethers (PBDEs), during structure fires. This study utilized biological monitoring to characterize FR exposures in 36 firefighters assigned to interior, exterior, and overhaul job assignments, before and after responding to controlled residential fire scenarios. Firefighters provided four urine samples (pre-fire and 3-h, 6-h, and 12-h post-fire) and two serum samples (pre-fire and approximately 23-h post-fire). Urine samples were analyzed for OPFR metabolites, while serum samples were analyzed for PBDEs, brominated and chlorinated furans, and chlorinated dioxins. Urinary concentrations of diphenyl phosphate (DPhP), a metabolite of triphenyl phosphate (TPhP), bis(1,3-dichloro-2-propyl) phosphate (BDCPP), a metabolite of tris(1,3-dichloro-2-propyl) phosphate (TDCPP), and bis(2-chloroethyl) phosphate (BCEtP), a metabolite of tris(2-chloroethyl) phosphate (TCEP), increased from pre-fire to 3-hr and 6-hr post-fire collection, but only the DPhP increase was statistically significant at a 0.05 level. The 3-hr and 6-hr post-fire concentrations of DPhP and BDCPP, as well as the pre-fire concentration of BDCPP, were statistically significantly higher than general population levels. BDCPP pre-fire concentrations were statistically significantly higher in firefighters who previously participated in a scenario (within the past 12 days) than those who were responding to their first scenario as part of the study. Similarly, firefighters previously assigned to interior job assignments had higher pre-fire concentrations of BDCPP than those previously assigned to exterior job assignments. Pre-fire serum concentrations of 2,3,4,7,8-pentachlorodibenzofuran (23478-PeCDF), a known human carcinogen, were also statistically significantly above the general population levels. Of the PBDEs quantified, only decabromodiphenyl ether (BDE-209) pre- and post-fire serum concentrations were statistically significantly higher than the general population. These results suggest firefighters absorbed certain FRs while responding to fire scenarios. |
Quantile regression for exposure data with repeated measures in the presence of non-detects
Chen IC , Bertke SJ , Curwin BD . J Expo Sci Environ Epidemiol 2021 31 (6) 1057-1066 BACKGROUND: Exposure data with repeated measures from occupational studies are frequently right-skewed and left-censored. To address right-skewed data, data are generally log-transformed and analyses modeling the geometric mean operate under the assumption the data are log-normally distributed. However, modeling the mean of exposure may lead to bias and loss of efficiency if the transformed data do not follow a known distribution. In addition, left censoring occurs when measurements are below the limit of detection (LOD). OBJECTIVE: To present a complete illustration of the entire conditional distribution of an exposure outcome by examining different quantiles, rather than modeling the mean. METHODS: We propose an approach combining the quantile regression model, which does not require any specified error distributions, with the substitution method for skewed data with repeated measurements and non-detects. RESULTS: In a simulation study and application example, we demonstrate that this method performs well, particularly for highly right-skewed data, as parameter estimates are consistent and have smaller mean squared error relative to existing approaches. SIGNIFICANCE: The proposed approach provides an alternative insight into the conditional distribution of an exposure outcome for repeated measures models. |
Sociopolitical values and social institutions: Studying work and health equity through the lens of political economy.
Fujishiro K , Ahonen EQ , Gimeno Ruiz de Porras D , Chen IC , Benavides FG . SSM Popul Health 2021 14 100787 Work contributes to health and health inequity in complex ways. The traditional exposure-disease framework used in occupational health research is not equipped to address societal contexts in which work is embedded. The political economy approach to public health directly examines macro-level societal contexts, but the attention to work in this literature is mostly on unemployment. As a result, we have limited understanding of work as a social determinant of health and health inequity. To fill this gap, we propose a conceptual framework that facilitates research on work, health, and health equity in institutional contexts. As an illustration of different social institutions creating different work-related health, we present characteristics of work and health in the United States and the European Union using the 2015 Working Conditions Surveys data. The results also highlight limitations of the traditional exposure-disease approach used in occupational health research. Applying the proposed framework, we discuss how work and health could be investigated from a broader perspective that involves multiple social institutions and the sociopolitical values that underpin them. Such investigations would inform policy interventions that are congruent with existing social institutions and thus have the potential for being adopted and effective. Further, we clarify the role of research in generating knowledge that would contribute to institutional change in support of population health and health equity. |
Effects of firefighting hood design, laundering and doffing on smoke protection, heat stress and wearability
Kesler RM , Mayer A , Fent KW , Chen IC , Deaton AS , Ormond RB , Smith DL , Wilkinson A , Kerber S , Horn GP . Ergonomics 2021 64 (6) 1-13 Firefighter hoods must provide protection from elevated temperatures and products of combustion (e.g. particulate) while simultaneously being wearable (comfortable and not interfering with firefighting activities). The purpose of this study was to quantify the impact of (1) hood design (traditional knit hood vs particulate-blocking hood), (2) repeated laundering, and (3) hood removal method (traditional vs overhead doffing) on (a) protection from soot contamination on the neck, (b) heat stress and (c) wearability measures. Using a fireground exposure simulator, 24 firefighters performed firefighting activities in realistic smoke and heat conditions using a new knit hood, new particulate-blocking hood and laundered particulate-blocking hood. Overall, soot contamination levels measured from neck skin were lower when wearing the laundered particulate-blocking hoods compared to new knit hoods, and when using the overhead hood removal process. No significant differences in skin temperature, core temperature, heart rate or wearability measures were found between the hood conditions. Practitioner Summary: The addition of a particulate-blocking layer to firefighters' traditional two-ply hood was found to reduce the PAH contamination reaching the neck but did not affect heat stress measurements or thermal perceptions. Modifying the process for hood removal resulted in a larger reduction in neck skin contamination than design modification. Abbreviations: ANOVA: analysis of variance; B: new particulate-blocking hood and PPE (PPE configuration); FES: fireground exposure simulator; GI: gastrointestinal; K: new knit hood and PPE (PPE configuration); L: laundered particulate-blocking hood and PPE (PPE configuration); LOD: limit of detection; MLE: maximum likelihood estimation; NFPA: National fire protection association; PAH: polycyclic aromatic hydrocarbon; PPE: personal protective equipment; SCBA: self-contained breathing apparatus; THL: total heat loss; TPP: thermal protective performance. |
Assessment of triphenyl phosphate (TPhP) exposure to nail salon workers by air, hand wipe, and urine analysis
Estill CF , Mayer A , Slone J , Chen IC , Zhou M , La Guardia MJ , Jayatilaka N , Ospina M , Calafat A . Int J Hyg Environ Health 2020 231 113630 Triphenyl phosphate (TPP or TPhP) is commonly used as an additive plasticizer or organophosphate flame retardant (OPFR) in consumer products including nail polish. We evaluated exposure to TPhP from 12 nail salon technicians working at four nail salons located in California over a period of two work days. Bulk samples of 15 nail polishes and other nail products were collected. Study participants also provided two personal air samples, two hand wipe samples (pre- and post-shift on day two), and two urine samples (pre-shift day one and post-shift day two). The geometric mean (GM) of TPhP air sampling concentrations was 7.39 ng/m(3). Post-shift TPhP hand wipe concentrations (GM 1.35 μg/sample) were significantly higher (p = 0.024) than pre-shift hand wipe concentrations (GM 0.29 μg/sample). Diphenyl phosphate (DPP or DPhP), a urinary metabolite of TPhP used in this study as a biomarker of exposure, was detected in all post-shift urine samples and 75% of urine pre-shift samples. DPhP post-shift concentrations (GM 1.35 μg/g creatinine) were significantly higher than pre-shift concentrations (GM 0.84 μg/g creatinine; p = 0.012). In addition, DPhP post-shift concentrations were correlated with TPhP post-shift hand wipe concentrations, suggesting dermal contact may be a relevant exposure pathway for nail salon workers. |
Marginal quantile regression for longitudinal data analysis in the presence of time-dependent covariates
Chen IC , Westgate PM . Int J Biostat 2020 17 (2) 267-282 When observations are correlated, modeling the within-subject correlation structure using quantile regression for longitudinal data can be difficult unless a working independence structure is utilized. Although this approach ensures consistent estimators of the regression coefficients, it may result in less efficient regression parameter estimation when data are highly correlated. Therefore, several marginal quantile regression methods have been proposed to improve parameter estimation. In a longitudinal study some of the covariates may change their values over time, and the topic of time-dependent covariate has not been explored in the marginal quantile literature. As a result, we propose an approach for marginal quantile regression in the presence of time-dependent covariates, which includes a strategy to select a working type of time-dependency. In this manuscript, we demonstrate that our proposed method has the potential to improve power relative to the independence estimating equations approach due to the reduction of mean squared error. |
Flame retardants, dioxins, and furans in air and on firefighters' protective ensembles during controlled residential firefighting
Fent KW , LaGuardia M , Luellen D , McCormick S , Mayer A , Chen IC , Kerber S , Smith D , Horn GP . Environ Int 2020 140 105756 INTRODUCTION: Structure fires that involve modern furnishings may emit brominated flame retardants (BFRs) and organophosphate flame retardants (OPFRs), as well as brominated and chlorinated dioxins and furans, into the environment. OBJECTIVES: The goal of this study was to quantify the airborne and personal protective equipment (PPE) contamination levels of these compounds during controlled residential fires in the U.S., and to evaluate gross-decontamination measures. METHODS: Bulk-sampling was done to confirm the presence of flame retardants (FRs) in the furnishings used in 12 controlled residential structure fires. Area air samples were collected during the fires and PPE wipe samples were collected from the firefighters' turnout jackets and gloves after firefighting. For each fire, half of the jackets were decontaminated and the other half were not. RESULTS: Of the BFRs and OPFRs measured in air during the fire period, decabromodiphenyl ether (BDE-209) and triphenyl phosphate (TPP) were the most abundant, with medians of 15.6 and 408 microg/m(3), respectively, and were also detected during overhaul. These and several other BFRs and OPFRs were measured on PPE. Some gloves had contaminant levels exceeding 100 ng/cm(2) and were generally more contaminated than jackets. Air and surface levels of the brominated furans appeared to be higher than the chlorinated dioxins and furans. Routine gross decontamination appeared to reduce many of the BFR contaminants, but results for the OPFRs were mixed. CONCLUSIONS: Structure fires are likely to result in a variety of FRs, dioxins, and furans into the environment, leading to PPE contamination for those working on the fireground. Firefighters should wear self-contained breathing apparatus during all phases of the response and launder or decontaminate their PPE (including gloves) after fire events. |
Association between maternal occupational exposure to polycyclic aromatic hydrocarbons and rare birth defects of the face and central nervous system
Santiago-Colon A , Rocheleau CM , Chen IC , Sanderson W , Waters MA , Lawson CC , Langlois PH , Cragan JD , Reefhuis J . Birth Defects Res 2020 112 (5) 404-417 BACKGROUND: Previous studies suggested associations between maternal smoking, a source of exposure to polycyclic aromatic hydrocarbons (PAHs) and other chemicals, and central nervous system and face birth defects; however, no previous studies have evaluated maternal occupational PAH exposure itself. METHODS: Jobs held in the periconceptional period were retrospectively assigned for occupational PAH exposures. Associations between maternal occupational PAH exposure and selected rare defects of the face (cataracts, microphthalmia, glaucoma, microtia, and choanal atresia) and central nervous system (holoprosencephaly, hydrocephaly, cerebellar hypoplasia, and Dandy-Walker malformation) were evaluated using data from the National Birth Defects Prevention Study, a population-based case-control study in the United States. Crude and adjusted odds ratios (ORs) with 95% confidence intervals were calculated to estimate associations between each evaluated defect and PAH exposure using multivariable logistic regression. RESULTS: Food and beverage serving, as well as cooks and food preparation occupations, were among the most frequent jobs held by exposed mothers. Cataracts, microtia, microphthalmia, and holoprosencephaly were significantly associated with PAH exposure with evidence of dose-response (P-values for trend </=.05). Hydrocephaly was associated with any PAH exposure, but not significant for trend. Sensitivity analyses that reduced possible sources of exposure misclassification tended to strengthen associations. CONCLUSIONS: This is the first population-based case-control study to evaluate associations between maternal occupational PAH exposures and these rare birth defects of the central nervous system and face. |
Worker exposure to flame retardants in manufacturing, construction and service industries
Estill CF , Slone J , Mayer A , Chen IC , La Guardia MJ . Environ Int 2019 135 105349 Workers in several industries are occupationally exposed to flame retardants. This study characterizes flame retardant exposure for nine industries through air and hand wipe measures for 105 workers. Specifically, we analyzed 24 analytes from three chemical classes: organophosphate flame retardants (OFRs), polybrominated diphenyl ethers (PBDEs), and non-PBDE brominated flame retardants (NPBFRs). The industries were: carpet installation, chemical manufacturing, foam manufacturing, electronic scrap, gymnastics, rigid board installation, nail salons, roofing, and spray polyurethane foam. Workers wore personal air samplers for two entire workdays and provided hand wipe samples before and after the second work day. Bulk products were also analyzed. The air, hand wipe and bulk samples were evaluated for relevant flame retardants. Spray polyurethane foam workers' tris(1-chloro-2-propyl) phosphate air (geometric mean = 48,500 ng/m(3)) and hand wipe (geometric mean = 83,500 ng per sample) concentrations had the highest mean industry concentration of any flame retardant analyzed in this study, followed by triphenyl phosphate air concentration and tris(1,3-dichloro-2-propyl) phosphate hand wipe concentration from chemical manufacturers. Overall, OFR air and hand wipe concentrations were higher and more prevalent than PBDEs or non-PBDE brominated flame retardants. Some industries including spray polyurethane foam application, chemical manufacturing, foam manufacturing, nail salons, roofing, and rigid polyiso board installation had high potential for both air and hand exposure to OFRs. Carpet installers, electronic scrap workers, and gymnastic workers had exposures to all three classes of flame retardants including PBDEs, which were phased out of production in 2013. Air and dermal exposures to OFRs are prevalent in many industries and are replacing PBDEs in some industries. |
Assessment of spray polyurethane foam worker exposure to organophosphate flame retardants through measures in air, hand wipes, and urine
Estill CF , Slone J , Mayer AC , Phillips K , Lu J , Chen IC , Christianson A , Streicher R , Guardia MJ , Jayatilaka N , Ospina M , Calafat AM . J Occup Environ Hyg 2019 16 (7) 1-12 Tris(1-chloro-2-propyl) phosphate (TCPP, also referenced as TCIPP), a flame retardant used in spray polyurethane foam insulation, increases cell toxicity and affects fetal development. Spray polyurethane foam workers have the potential to be exposed to TCPP during application. In this study, we determined exposure to TCPP and concentrations of the urinary biomarker bis(1-chloro-2-propyl) phosphate (BCPP) among 29 spray polyurethane foam workers over 2 work days. Work was conducted at residential or commercial facilities using both open-cell (low density) and closed-cell (high density) foam. Study participants provided two personal air samples (Day 1 and Day 2), two hand wipe samples (Pre-shift Day 2 and Post-shift Day 2), and two spot urine samples (Pre-shift Day 1 and Post-shift Day 2). Bulk samples of cured spray foam were also analyzed. Sprayers were found to have significantly higher TCPP geometric mean (GM) concentration in personal air samples (87.1 mug/m(3)), compared to helpers (30.2 mug/m(3); p = 0.025). A statistically significant difference was observed between TCPP pre- and post-shift hand wipe GM concentrations (p = 0.004). Specifically, TCPP GM concentration in post-shift hand wipe samples of helpers (106,000 ng/sample) was significantly greater than pre-shift (27,300 ng/sample; p < 0.001). The GM concentration of the urinary biomarker BCPP (23.8 mug/g creatinine) was notably higher than the adult male general population (0.159 mug/g creatinine, p < 0.001). Urinary BCPP GM concentration increased significantly from Pre-shift Day 1 to Post-shift Day 2 for sprayers (p = 0.013) and helpers (p = 0.009). Among bulk samples, cured open-cell foam had a TCPP GM concentration of 9.23% by weight while closed-cell foam was 1.68%. Overall, post-shift BCPP urine concentrations were observed to be associated with TCPP air and hand wipe concentrations, as well as job position (sprayer vs. helper). Spray polyurethane foam workers should wear personal protective equipment including air-supplied respirators, coveralls, and gloves during application. |
- Page last reviewed:Feb 1, 2024
- Page last updated:Jan 27, 2025
- Content source:
- Powered by CDC PHGKB Infrastructure