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Lee K.-H.,Seoul National University | Jung H.-J.,Catholic Kwandong University | Park D.-U.,Korea University | Ryu S.-H.,Korea University | And 5 more authors.
PLoS ONE | Year: 2015

Objective: The purposes of this study were to determine the following: 1) the exposure levels of municipal household waste (MHW) workers to diesel particulate matter (DPM) using elemental carbon (EC), organic carbon (OC), total carbon (TC), black carbon (BC), and fine particulate matter (PM 2.5) as indicators; 2) the correlations among the indicators; 3) the optimal indicator for DPM; and 4) factors that influence personal exposure to DPM. Methods: A total of 72 workers in five MHW collection companies were assessed over a period of 7 days from June to September 2014. Respirable EC/OC samples were quantified using the thermal optical transmittance method. BC and PM 2.5 were measured using real-time monitors, an aethalometer and a laser photometer. All results were statistically analyzed for occupational and environmental variables to identify the exposure determinants of DPM. Results: The geometric mean of EC, OC, TC, BC and PM 2.5 concentrations were 4.8, 39.6, 44.8, 9.1 and 62.0 μg/m3, respectively. EC concentrations were significantly correlated with the concentrations of OC, TC and BC, but not with those of PM 2.5. The exposures of the MHW collectors to EC, OC, and TC were higher than those of the drivers (p<0.05). Workers of trucks meeting Euro 3 emission standard had higher exposures to EC, OC, TC and PM 2.5 than those working on Euro 4 trucks (p<0.05). Multiple regression analysis revealed that the job task, European engine emission standard, and average driving speed were the most influential factors in determining worker exposure. Conclusions: We assessed MHW workers' exposure to DPM using parallel sampling of five possible indicators. Of these five indicators, EC was shown to be the most useful indicator of DPM exposure for MHW workers, and the job task, European emission standard, and average driving speed were the main determinants of EC exposure. Copyright: © 2015 Lee et al. Source

Sung M.-S.,Chonnam National University | Yoon J.-H.,Occupational Lung Disease Institute | Park S.-W.,Chonnam National University
Journal of Glaucoma | Year: 2014

Purpose: To evaluate the diagnostic validity of macular ganglion cell-inner plexiform layer (mGCIPL) thickness deviation map algorithm using Cirrus high definition-optical coherence tomography to discriminate between normal controls and patients with preperimetric or early glaucoma.Patients and Methods: Seventy-two normal controls, 37 patients with preperimetric glaucoma and 70 patients with early glaucoma were enrolled. mGCIPL thickness and peripapillary retinal nerve fiber layer (pRNFL) thickness were measured by Cirrus high definition-optical coherence tomography. Areas showing abnormal color coding were obtained by customized Image J software calculating the number of abnormal superpixels at 1% and 5% level in each deviation map of measurements (GCIPL-DM1, GCIPLDM5, RNFL-DM1, RNFL-DM5). The area under the receiver operating characteristic curve (AROC) of each parameter was calculated to provide diagnostic ability between normal controls and patients with preperimetric or early glaucoma.Results: AROCs of the deviation map algorithms were higher than those of other parameters. Parameter with the best AROC was the GCIPL-DM5 (0.920 and 0.968) in both preperimetric and early glaucoma. The sensitivities of the GCIPL-DM5 at 80% and 95% specificities were 92% and 68% in preperimetric glaucoma and 98% and 90% in early glaucoma, respectively. Pairwise comparisons between AROCs of parameters from deviation map algorithms did not show statistically significant differences.Conclusions: mGCIPL thickness deviation map showed good diagnostic ability in detecting preperimetric and early glaucoma, and it was comparable with pRNFL thickness deviation map. Our findings suggest that it can be an important parameter in detecting subtle glaucomatous structural change. Copyright © 2013 by Lippincott Williams & Wilkins. Source

Kim B.,Occupational Lung Disease Institute | Kim H.,Catholic University of Korea | Yu I.J.,Hoseo University
Industrial Health | Year: 2014

Nanosilica is one of the most widely used nanomaterials across the world. However, their assessment data on the occupational exposure to nanoparticles is insufficient. The present study performed an exposure monitoring in workplace environments where synthetic powders are prepared using fumed nanosilica. Furthermore, after it was observed during exposure monitoring that nanoparticles were emitted through leakage in a vacuum cleaner (even with a HEPA-flter installed in it), the properties of the leaked nanoparticles were also investigated. Workers were exposed to high-concentration nanosilica emitted into the air while pouring it into a container or transferring the container. The use of a vacuum cleaner with a leak (caused by an inadequate sealing) was found to be the origin of nanosilica dispersion in the indoor air. While the particle size of the nanosilica that emitted into the air (during the handling of nanosilica by a worker) was mostly over 100 nm or several microns (μm) due to the coagulation of particles, the size of nanosilica that leaked out of vacuum cleaner was almost similar to the primary size (mode diameter 11.5 nm). Analysis of area samples resulted in 20% (60% in terms of peak concentration) less than the analysis of the personals sample. © 2014 National Institute of Occupational Safety and Health. Source

Lee K.-H.,Seoul National University | Jung H.-J.,Catholic Kwandong University | Shin J.-A.,Occupational Lung Disease Institute | Kwak H.-S.,Occupational Lung Disease Institute | And 5 more authors.
Aerosol and Air Quality Research | Year: 2016

The objectives of this study to characterize exposure to respirable elemental carbon (EC), organic carbon (OC) and total carbon (TC) in relation to waste-handling activities and vehicle characteristics among workers who collect household wastes, and to examine the relationships among EC, OC and TC. A total of 72 household waste collectors were selected for exposure assessment over a full workday and most (70 of 72) exposures were collected from diesel emissions that underwent catalytic after-treatment by diesel particulate filters (DPFs). The exposure assessments were conducted from June through September 2014. Airborne EC and OC from the breathing zone were collected on pre-fired quartz filters and quantified using the thermal optical reflectance method. The average EC exposure level of the household waste collectors was 7.2 µg m–3 with a range of 2.0-30.4 µg m–3. A significant relationship between EC and TC exposure levels was observed (logTC = 0.38 × logEC + 3.22, p < 0.0001, adjusted R2 = 0.23). EC level (µg m–3), truck age (< 10 year-old vs. ≥ 10 year-old), type of waste collection job (collector vs. driver), current smoking status (yes vs. no) and month were found to significantly influence the level of TC exposure (n = 70, adjusted R2 = 0.56, p < 0.0001). The average exposure to EC of household waste collectors can be categorized into the relatively low exposure group when compared to other DE exposure jobs. TC was not a best surrogate for DE exposure in household waste collection environments because it was affected by other OC interferences that were not generated from diesel engines. © Taiwan Association for Aerosol Research. Source

Lee J.H.,University of Washington | Han J.H.,Chonnam National University | Kim J.H.,Korea Institute of Machinery and Materials | Kim B.,Occupational Lung Disease Institute | And 8 more authors.
Inhalation Toxicology | Year: 2016

Graphenes have emerged as a highly promising, two-dimensional engineered nanomaterial that can possibly substitute carbon nanotubes. They are being explored in numerous R&D and industrial applications in laboratories across the globe, leading to possible human and environmental exposures to them. Yet, there are no published data on graphene exposures in occupational settings and no readily available methods for their detection and quantitation exist. This study investigates for the first time the potential exposure of workers and research personnel to graphenes in two research facilities and evaluates the status of the control measures. One facility manufactures graphene using graphite exfoliation and chemical vapor deposition (CVD), while the other facility grows graphene on a copper plate using CVD, which is then transferred to a polyethylene terephthalate (PET) sheet. Graphene exposures and process emissions were investigated for three tasks - CVD growth, exfoliation, and transfer - using a multi-metric approach, which utilizes several direct reading instruments, integrated sampling, and chemical and morphological analysis. Real-time instruments included a dust monitor, condensation particle counter (CPC), nanoparticle surface area monitor, scanning mobility particle sizer, and an aethalometer. Morphologically, graphenes and other nanostructures released from the work process were investigated using a transmission electron microscope (TEM). Graphenes were quantified in airborne respirable samples as elemental carbon via thermo-optical analysis. The mass concentrations of total suspended particulate at Workplaces A and B were very low, and elemental carbon concentrations were mostly below the detection limit, indicating very low exposure to graphene or any other particles. The real-time monitoring, especially the aethalometer, showed a good response to the released black carbon, providing a signature of the graphene released during the opening of the CVD reactor at Workplace A. The TEM observation of the samples obtained from Workplaces A and B showed graphene-like structures and aggregated/agglomerated carbon structures. Taken together, the current findings on common scenarios (exfoliation, CVD growth, and transfer), while not inclusive of all graphene manufacturing processes, indicate very minimal graphene or particle exposure at facilities manufacturing graphenes with good manufacturing practices. © 2016 Taylor & Francis. Source

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