Last data update: May 06, 2024. (Total: 46732 publications since 2009)
Records 1-11 (of 11 Records) |
Query Trace: Estill CF[original query] |
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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. |
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. |
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. |
COVID-19 and the Workplace: Research Questions for the Aerosol Science Community.
Lindsley WG , Blachere FM , Burton NC , Christensen B , Estill CF , Fisher EM , Martin SB , Mead KR , Noti JD , Seaton M . Aerosol Sci Technol 2020 54 (10) 1117-1123 The global Coronavirus Disease (COVID-19) pandemic caused by the SARS-CoV-2 virus has raised many urgent questions about the transmission of this disease, including the possible roles of aerosols containing SARS-CoV-2. This is particularly true in workplace settings where workers may encounter customers and coworkers who are infected with COVID-19 and where aerosols can be produced in a variety of ways. Research by the aerosol science community is needed to learn more about whether SARS-CoV-2 can spread by infectious aerosols and about the effectiveness of different protective measures. The purpose of this commentary is to present some of the questions surrounding aerosols containing SARS-CoV-2 and to provide suggestions for future research topics. |
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. |
Noise and neurotoxic chemical exposure relationship to workplace traumatic injuries: A review
Estill CF , Rice CH , Morata T , Bhattacharya A . J Safety Res 2016 60 35-42 Introduction: More than 5,000 fatalities and eight million injuries occurred in the workplace in 2007 at a cost of $6 billion and $186 billion, respectively. Neurotoxic chemicals are known to affect central nervous system functions among workers, which include balance and hearing disorders. However, it is not known if there is an association between exposure to noise and solvents and acute injuries. . Method: A thorough review was conducted of the literature on the relationship between noise or solvent exposures and hearing loss with various health outcomes. . Results: The search resulted in 41 studies. Health outcomes included: hearing loss, workplace injuries, absence from work due to sickness, fatalities, hospital admissions due to workplace accidents, traffic accidents, hypertension, balance, slip, trips, or falls, cognitive measures, or disability retirement. Important covariates in these studies were age of employee, type of industry or occupation, or length of employment. . Discussion: Most authors that evaluated noise exposure concluded that higher exposure to noise resulted in more of the chosen health effect but the relationship is not well understood. Studies that evaluated hearing loss found that hearing loss was related to occupational injury, disability retirement, or traffic accidents. Studies that assessed both noise exposure and hearing loss as risk factors for occupational injuries reported that hearing loss was related to occupational injuries as much or more than noise exposure. Evidence suggests that solvent exposure is likely to be related to accidents or other health consequences such balance disorders. . Conclusions: Many authors reported that noise exposures and hearing loss, respectively, are likely to be related to occupational accidents. . Practical applications: The potential significance of the study is that findings could be used by managers to reduce injuries and the costs associated with those injures. |
Comparison of air sampling methods for aerosolized spores of B. anthracis Sterne
Estill CF , Baron PA , Beard JK , Hein MJ , Larsen LD , Deye GJ , Rose L , Hodges L . J Occup Environ Hyg 2011 8 (3) 179-86 Bacillus anthracis Sterne spores were aerosolized within a chamber at concentrations ranging from 1x10(3) to 1.7x10(4) spores per cubic meter of air (particles (p)/m(3)) to compare three different sampling methods: Andersen samplers, gelatin filters, and polytetrafluoroethylene (PTFE) membrane filters. Three samples of each type were collected during each of 19 chamber runs. Chamber concentration was determined by an aerodynamic particle sizer (APS) for the size range of 1.114-1.596 mum. Runs were categorized (low, medium, and high) based on tertiles of the APS estimated air concentrations. Measured air concentrations and recovery efficiency [ratio of the measured (colony forming units (CFU)/m(3)) to the APS estimated (particles/m(3)) air concentrations] for the sampling methods were compared using mixed-effects regression models. Limits of detection for each method were estimated based on estimated recovery efficiencies. Mean APS estimated air concentrations were 1600 particles/m(3), 4100 particles/m(3), and 9100 particles/m(3) at the low, medium, and high tertiles, respectively; coefficient of variation (CV) ranged from 25 to 40%. Statistically significant differences were not observed among the three sampling methods. At the high and medium tertiles, estimated correlations of measured air concentration (CFU/m(3)) among samples collected from the same run of the same type were high (0.73 to 0.93). Among samples collected from the same run but of different types, correlations were moderate to high (0.45 to 0.85); however, correlations were somewhat lower at the low tertile (-0.31 to 0.75). Estimated mean recovery efficiencies ranged from 0.22 to 0.25 CFU/particle with total CVs of approximately 84 to 97%. Estimated detection limits ranged from 35 to 39 particles/m(3). These results will enable investigators to conduct environmental sampling, quantify contamination levels, and conduct risk assessments of B. anthracis. |
Use of historical data and a novel metric in the evaluation of the effectiveness of hearing conservation program components
Heyer N , Morata TC , Pinkerton LE , Brueck SE , Stancescu D , Panaccio MP , Kim H , Sinclair JS , Waters MA , Estill CF , Franks JR . Occup Environ Med 2010 68 (7) 510-7 OBJECTIVES: To evaluate the effectiveness of hearing conservation programs (HCP) and their specific components in reducing noise-induced hearing loss (NIHL). METHODS: This retrospective cohort study was conducted at one food-processing plant and two automotive plants. Audiometric and work-history databases were combined with historical noise monitoring data to develop a time-dependent exposure matrix for each plant. Historical changes in production and HCP implementation were collected from company records, employee interviews and focus groups. These data were used to develop time-dependent quality assessments for various HCP components. 5478 male (30 427 observations) and 1005 female (5816 observations) subjects were included in the analysis. RESULTS: Analyses were conducted separately for males and females. Females tended to have less NIHL at given exposure levels than males. Duration of noise exposure stratified by intensity (dBA) was a better predictor of NIHL than the standard equivalent continuous noise level (L(eq)) based upon a 3-dBA exchange. Within this cohort, efficient dBA strata for males were <95 versus ≥95, and for females <90 versus ≥90. The reported enforced use of hearing protection devices (HPDs) significantly reduced NIHL. The data did not have sufficient within-plant variation to determine the effectiveness of noise monitoring or worker training. An association between increased audiometric testing and NIHL was believed to be an artifact of increased participation in screening. CONCLUSIONS: Historical audiometric data combined with noise monitoring data can be used to better understand the effectiveness of HCPs. Regular collection and maintenance of quality data should be encouraged and used to monitor the effectiveness of these interventions. |
Recovery efficiency and limit of detection of aerosolized Bacillus anthracis Sterne from environmental surface samples
Estill CF , Baron PA , Beard JK , Hein MJ , Larsen LD , Rose L , Schaefer FW 3rd , Noble-Wang J , Hodges L , Lindquist HD , Deye GJ , Arduino MJ . Appl Environ Microbiol 2009 75 (13) 4297-306 After the 2001 anthrax incidents, surface sampling techniques for biological agents were found to be inadequately validated, especially at low surface loadings. We aerosolized Bacillus anthracis Sterne spores within a chamber to achieve very low surface loading (ca. 3, 30, and 200 CFU per 100 cm(2)). Steel and carpet coupons seeded in the chamber were sampled with swab (103 cm(2)) or wipe or vacuum (929 cm(2)) surface sampling methods and analyzed at three laboratories. Agar settle plates (60 cm(2)) were the reference for determining recovery efficiency (RE). The minimum estimated surface concentrations to achieve a 95% response rate based on probit regression were 190, 15, and 44 CFU/100 cm(2) for sampling steel surfaces and 40, 9.2, and 28 CFU/100 cm(2) for sampling carpet surfaces with swab, wipe, and vacuum methods, respectively; however, these results should be cautiously interpreted because of high observed variability. Mean REs at the highest surface loading were 5.0%, 18%, and 3.7% on steel and 12%, 23%, and 4.7% on carpet for the swab, wipe, and vacuum methods, respectively. Precision (coefficient of variation) was poor at the lower surface concentrations but improved with increasing surface concentration. The best precision was obtained with wipe samples on carpet, achieving 38% at the highest surface concentration. The wipe sampling method detected B. anthracis at lower estimated surface concentrations and had higher RE and better precision than the other methods. These results may guide investigators to more meaningfully conduct environmental sampling, quantify contamination levels, and conduct risk assessment for humans. |
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