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1.
Ann Work Expo Health ; 68(4): 397-408, 2024 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-38536905

RESUMO

BACKGROUND: This study was conducted as an effort to develop a Korean construction job exposure matrix (KoConJEM) based on 60 occupations recently consolidated by the construction workers mutual aid association for use by the construction industry. METHODS: The probability, intensity, and prevalence of exposure to 26 hazardous agents for 60 consolidated occupations were evaluated as binary (Yes/No) or four categories (1 to 4) by 30 industrial hygiene experts. The score for risk was calculated by multiplying the exposure intensity by the prevalence of exposure. Fleiss' kappa for each hazardous agent and occupation was used to determine agreement among the 30 experts. The JEM was expressed on a heatmap and a web-based dashboard to facilitate comparison of factors affecting exposure according to each occupation and hazardous agent. RESULTS: Awkward posture, heat/cold, heavy lifting, and noise were hazardous agents regarded as exposure is probable by at least one or more experts in all occupations, while exposure to asphalt fumes was considered hazardous in the smallest number of occupations (n = 5). Based on the degree of agreement among experts, more than half of the harmful factors and most occupations showed fair to good results. The highest risk value was 16 for awkward posture for most occupations other than safety officer. CONCLUSIONS: The KoConJEM provides information on the probability, intensity, and prevalence of exposure to harmful factors, including most occupations employing construction workers; therefore, it may be useful in the conduct of epidemiological studies on assessment of health risk for construction workers.

2.
Ann Work Expo Health ; 68(3): 256-268, 2024 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-38377017

RESUMO

OBJECTIVES: Industry- and occupation-based carcinogen exposure matrices play a pivotal role in preventing occupational cancer. While the Korean CARcinogen EXposure (K-CAREX) has been developed in recent years to assess exposure prevalence and intensity by industry, the feasibility of constructing an occupation-based exposure matrix remains unexplored. Hence, the objective of this study is to explore the potential of combining the nationwide work environment measurement database (WEMD) and the special health examination database (SHED) to develop a comprehensive occupation-based exposure matrix. METHODS: The WEMD provides information on airborne lead measurements, including industry codes, but it does not include data related to occupations. In contrast, the SHED contains information on both occupation and blood lead levels. By integrating these 2 databases, we attempted to assess airborne lead exposure levels by occupation. Additionally, we performed a rank correlation analysis to compare the airborne exposure levels with corresponding blood lead levels according to occupation. RESULTS: A total of 35 425 workers who both wore air samplers for lead and underwent special health examinations for lead were extracted between 2019 and 2021. An occupation-based exposure matrix was developed to evaluate the intensity of lead exposure across a range of occupations, encompassing 51 minor occupations and 70-unit occupations. Rank correlation analyses showed strong positive correlations between airborne lead and blood lead measurements according to occupation. CONCLUSIONS: Our study findings suggest that combining 2 nationwide surveillance databases can be an effective approach for creating an occupation-based exposure matrix. However, our results also highlight several limitations that need to be addressed in future studies to improve the accuracy and reliability of such matrices.


Assuntos
Exposição Ocupacional , Humanos , Exposição Ocupacional/análise , Chumbo/análise , Reprodutibilidade dos Testes , Ocupações , Carcinógenos/análise , República da Coreia/epidemiologia
3.
Phys Rev Lett ; 131(12): 126301, 2023 Sep 22.
Artigo em Inglês | MEDLINE | ID: mdl-37802950

RESUMO

Josephson tunnel junctions exhibit a supercurrent typically proportional to the sine of the superconducting phase difference ϕ. In general, a term proportional to cos(ϕ) is also present, alongside microscopic electronic retardation effects. We show that voltage pulses sharply varying in time prompt a significant impact of the cos(ϕ) term. Its interplay with the sin(ϕ) term results in a nonequilibrium fractional Josephson effect (NFJE) ∼sin(ϕ/2) in the presence of bound states close to zero frequency. Our microscopic analysis reveals that the interference of nonequilibrium virtual quasiparticle excitations is responsible for this phenomenon. We also analyze this phenomenon for topological Josephson junctions with Majorana bound states. Remarkably, the NFJE is independent of the ground state fermion parity unlike its equilibrium counterpart.

4.
Nicotine Tob Res ; 2023 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-37742212

RESUMO

INTRODUCTION: Cigarette smoke increases peripheral white blood cell (WBC) count. However, the dose-dependent association between smoking and C-reactive protein (CRP), an important inflammatory marker, has been reported inconsistent. Here, we evaluated the associations between smoking and CRP using both smoking questionnaires and urine cotinine as exposure markers. METHODS: The Korea National Health and Nutrition Examination Survey data were used for analyzing the associations. Multiple regression analyses were performed to examine the associations between cigarette smoke exposure, as assessed by questionnaires and urine cotinine, and health effects, as measured by CRP and WBC count, controlling for potential confounders. The confounders, including age, sex, body mass index, blood pressure, cholesterol, glucose, alanine aminotransferase, and uric acid, were selected a priori based on the literature. RESULTS: A total of 11,435 participants were included for analysis. For the exposure-response relationship, the results indicated a significant increase in CRP levels in male smokers compared to male non-smokers (p=0.002), whereas no significant increase was found in female smokers compared to female non-smokers (p=0.680). For the dose-response relationship, a significant positive association was observed between urine cotinine and CRP in male smokers (p=0.018), whereas no significant association was found in female smokers (p=0.508). WBC count consistently showed significant exposure-response and dose-response relationships in both sexes. CONCLUSIONS: WBC count was found to be a consistent effect marker of cigarette smoke exposure, while the association between CRP level and smoking was inconsistent and varied by sex. The sex-specific response to cigarette smoke exposure warrants further exploration in future studies. IMPLICATION: Cigarette smoke exposure is known to increase inflammation and has been thought to increase C-reactive protein (CRP), a significant inflammation marker. However, recent studies have reported conflicting results regarding the dose-dependent association between cigarette smoke exposure and CRP. This study found that the association between smoking and CRP is inconsistent and varies by sex, showing significant exposure-response in men but not in women. Furthermore, the study suggests that white blood cell count is a more consistent marker for cigarette smoke exposure.

5.
J Korean Med Sci ; 38(34): e271, 2023 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-37644685

RESUMO

BACKGROUND: Lead, which is widely used in various industrial settings, is a major health hazard for manufacturing workers. Therefore, control of lead exposure has been implemented in an effort to prevent lead-related health problems. In this study, our aim was to evaluate temporal trends in occupational lead exposure in Korean lead workers using data from monitoring of workplace exposure. METHODS: A nationwide work environment monitoring database, data from a work environment monitoring institution, and data extracted from a review paper were utilized. Different versions of standard industrial classification codes were aligned with the 10th Korean Standard Industrial Classification, which is generally consistent with the 4th revision of the International Standard Industrial Classification. The multiple data sources were combined and temporal trends over the period from 1994-2021 were estimated. In addition, separate estimation of temporal trends in the storage battery manufacturing industry over the period from 1987-2021 was also performed. RESULTS: A total of 444,296 personal airborne lead measurements were used for the estimation process. The temporal trends in occupational exposure to lead declined by -6% annually over the study period. In particular, levels of lead exposure in the storage battery manufacturing industry showed a steeper decline of -12% annually. CONCLUSIONS: Findings of our study showed that occupational exposure to lead declined over the period from 1994 to 2021 in Korea. However, adverse effects of exposure to lead on health should be regarded with caution. The results will be useful in conduct of epidemiological studies examining lead-related effects on health.


Assuntos
Chumbo , Exposição Ocupacional , Local de Trabalho , Humanos , Povo Asiático , Bases de Dados Factuais , República da Coreia
6.
Ann Work Expo Health ; 67(4): 508-517, 2023 04 21.
Artigo em Inglês | MEDLINE | ID: mdl-36857508

RESUMO

OBJECTIVES: Peak exposure to extremely low-frequency magnetic fields (ELF-MF) among semiconductor workers was characterized by type of factory, operation, and job. METHODS: A portable EMDEX meter was used to monitor the ELF-MF exposure of 117 semiconductor workers who are involved in wafer fabrication (fab) and assembly operations. ELF-MF measurements were logged every 3 s and categorized by process and job or activity during working hours. Two values of 0.5 and 1 µT were adopted subjectively as cutoff values of peak exposure levels based on a literature review. RESULTS: All semiconductor workers who were involved in diffusion, ion implanter operation, module, and chip test were exposed to ELF-MF higher than 0.5 µT during their entire working time. Engineers who maintained electric facilities in the semiconductor operations were exposed to the highest ELF-MF peak levels (2.5 µT on average above 0.5 µT and 3.6 µT on average above 1 µT). Operators working in chip testing showed the highest daily contribution of their peak levels to their daily average ELF-MF exposure levels (98.1% and 83.9%). In contrast, chemical mechanical planarization engineers, wafer test operators, and administrative workers outside clean rooms showed average exposure to less than 0.5 µT and a low proportion of duration of time exposed above either the 0.5 µT or 1 µT peak level points, along with a low daily contribution of peak exposure levels (16.0, 11.9, and 18.7%). CONCLUSIONS: Most of the activities and working locations next to machines generating ELF-MF in semiconductor operations showed high contributions of ELF-MF peak exposure to daily exposure dose despite their relative minor fraction of workers' daily time.


Assuntos
Exposição Ocupacional , Humanos , Campos Magnéticos , Semicondutores , Local de Trabalho , Campos Eletromagnéticos
7.
Ind Health ; 61(1): 78-87, 2023 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-35173135

RESUMO

This study aimed to identify the major industries and jobs with the highest proportion of workers' compensation (WC) claims for COVID-19, characterize COVID-19 WC claims in terms of their demographic properties and disease severity, and identify factors influencing the approval of COVID-19 WC claims as occupational disease. A total of 488 workers who submitted COVID-19-related claims to the Korea Workers' Compensation and Welfare Service (KWCWS) from January 2020 to July 2021 were analyzed. A Fisher's exact test was employed to associate the severity of COVID-19 infection with demographic properties. The highest proportion of all COVID-19 WC claims compensated as occupational disease (N=462) were submitted by healthcare workers (HCW=233, 50%), while only 9% (N=41) of the total originated from manufacturing industries. The 5% (N=26) of the COVID-19 WC claims accepted were evaluated as severe (N=15) and acute respiratory distress syndrome (N=9). A total of 71% (N=329) of the COVID-19 patients compensated (N=462) were from workplaces with infection clusters. A total of 26 WC cases were rejected for various reasons, including unclear infection routes, infection at private gatherings (including within families), no diagnosis, and more. Given our findings, we suggest an official system should be established to detect and compensate more job-associated infectious diseases like COVID-19.


Assuntos
COVID-19 , Doenças Profissionais , Indenização aos Trabalhadores , Humanos , COVID-19/epidemiologia , Indústrias/estatística & dados numéricos , Doenças Profissionais/epidemiologia , República da Coreia/epidemiologia , Indenização aos Trabalhadores/estatística & dados numéricos
8.
Saf Health Work ; 13(4): 493-499, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36579012

RESUMO

Background: The purpose of this study is to construct a job-exposure matrix for lead that accounts for industry and work processes within industries using a nationwide exposure database. Methods: We used the work environment measurement data (WEMD) of lead monitored nationwide from 2015 to 2016. Industrial hygienists standardized the work process codes in the database to 37 standard process and extracted key index words for each process. A total of 37 standardized process codes were allocated to each measurement based on an automated key word search based on the degree of agreement between the measurement information and the standard process index. Summary statistics, including the arithmetic mean, geometric mean, and 95th percentile level (X95), was calculated according to industry, process, and industry process. Using statistical parameters of contrast and precision, we compared the similarity of exposure groups by industry, process, and industry process. Results: The exposure intensity of lead was estimated for 583 exposure groups combined with 128 industry and 35 process. The X95 value of the "casting" process of the "manufacture of basic precious and non-ferrous metals" industry was 53.29 µg/m3, exceeding the occupational exposure limit of 50 µg/m3. Regardless of the limitation of the minimum number of samples in the exposure group, higher contrast was observed when the exposure groups were by industry process than by industry or process. Conclusion: We evaluated the exposure intensities of lead by combination of industry and process. The results will be helpful in determining more accurate information regarding exposure in lead-related epidemiological studies.

9.
Saf Health Work ; 13(3): 308-314, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-36156867

RESUMO

Background: Occupational cancer is a global health issue. The Korean CARcinogen EXposure (K-CAREX), a database of CARcinogen EXposure, was developed for the Korean labor force to estimate the number of workers exposed to carcinogens by industry. The present study aimed to estimate the intensity of exposure to carcinogens by industry, in order to supply complementary information about CARcinogen EXposure intensity to the K-CAREX. Methods: We used nationwide workplace monitoring data from 2014 to 2016 and selected target carcinogens based on the K-CAREX list. We computed the 95th percentile levels of measurements for each industry by carcinogens. Based on the 95th percentile level relative to the occupational exposure limit, we classified the CARcinogen EXposure intensity into five exposure ratings (1-5) for each industry. Results: The exposure ratings were estimated for 21 carcinogenic agents in each of the 228 minor industry groups. For example, 3,058 samples were measured for benzene in the manufacturing industry of basic chemicals. This industry was assigned a benzene exposure rating of 3. Conclusions: We evaluated the CARcinogen EXposure ratings across industries in Korean workers. The results will provide information on the exposure intensity to carcinogens for integration into the K-CAREX. Furthermore, it will aid in prioritizing control efforts and identifying industries of concern.

10.
Ann Occup Environ Med ; 34: e12, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35923795

RESUMO

Background: Gender equality in the workplace remains a challenge. This study aimed to investigate the gender gap of human resources in the field of occupational safety and health (OSH) in Korea. Methods: Several national statistical data that can confirm the gender distribution of personnel in the OSH sector were reviewed. The gender distribution of industrial technical manpower statistics, professional certificate holders in the OSH field, and the status of the appointment of safety and health managers by industry was analyzed. Results: The distribution of professionals in the OSH sector in Korea had a large gender gap with a small number of women. In particular, the proportion of women in the safety field was lower than that in the health field. In the younger age group, while the proportion of women is increasing, the gender gap tends to decrease. Conclusions: Few data are available to understand the gender-related aspects of OSH professions. Nevertheless, our results provide basic information for initiating a discussion on the necessity of establishing gender-sensitive culture and policies in the OSH sector.

11.
Nat Mater ; 21(10): 1144-1149, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-35927432

RESUMO

Van der Waals heterostructures with two-dimensional magnets offer a magnetic junction with an atomically sharp and clean interface. This attribute ensures that the magnetic layers maintain their intrinsic spin-polarized electronic states and spin-flipping scattering processes at a minimum level, a trait that can expand spintronic device functionalities. Here, using a van der Waals assembly of ferromagnetic Fe3GeTe2 with non-magnetic hexagonal boron nitride and WSe2 layers, we demonstrate electrically tunable, highly transparent spin injection and detection across the van der Waals interfaces. By varying an electrical bias, the net spin polarization of the injected carriers can be modulated and reversed in polarity, which leads to sign changes of the tunnelling magnetoresistance. We attribute the spin polarization reversals to sizable contributions from high-energy localized spin states in the metallic ferromagnet, so far inaccessible in conventional magnetic junctions. Such tunability of the spin-valve operations opens a promising route for the electronic control of next-generation low-dimensional spintronic device applications.

12.
Phys Rev Lett ; 128(12): 126801, 2022 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-35394303

RESUMO

Deep theoretical understanding of the electrical response of Josephson junctions is indispensable regarding both recent discoveries of new kinds of superconductivity and technological advances such as superconducting quantum computers. Here, we study the microscopic theory of the dc current-biased I-V characteristics of Josephson tunnel junctions. We derive an analytical formula of the I-V characteristics of generic junctions. We identify subharmonics of the I-V characteristics and their underlying mechanism as the feedback effect of intrinsic ac currents generated by voltage pulses in the past. We apply our theory to analytically solve the Werthamer equation and describe various dc current-biased I-V characteristics as a function of softening of the superconducting gap. Strikingly, we identify voltage staircases of the I-V characteristics in a genuine Josephson junction without ac current bias or qubit dynamics. Our general analytical formalism opens new avenues for a microscopic understanding of I-V characteristics of Josephson junctions that have been limited to phenomenological models so far.

13.
Ann Work Expo Health ; 66(9): 1224-1230, 2022 11 15.
Artigo em Inglês | MEDLINE | ID: mdl-35467719

RESUMO

OBJECTIVES: The purpose of this study is to investigate health managers' exposure to workplace violence (WPV) at construction sites and to review the statistical characteristics of experts in the safety and health fields using a gender-based analysis. METHODS: A preliminary survey of health managers at construction sites was conducted from March to April 2020 via the Health Managers Council in Construction Industry online community (https://band.us/band/62438722). Available national statistical data of safety and health personnel were reviewed. RESULTS: A total of 85 health managers (13 men, 72 women) responded to a preliminary survey. Health managers reported little physical violence (5.9%), while inappropriate work orders (83.5%) and sexual harassment (52.9%) were high, and health managers' experience of sexual harassment was significantly higher among women than men (P < 0.01). The professional safety and health field in Korea have a large gender gap, with few women. In particular, the proportion of women in the safety field was lower than in the health field. CONCLUSIONS: Young female health managers in the male-dominated construction industry are more vulnerable to WPV, including sexual harassment. To reduce the risk of WPV exposure and gender discrimination among female health managers, it is necessary to increase regular employment and provide more practical WPV prevention education for all construction employees.


Assuntos
Indústria da Construção , Exposição Ocupacional , Violência no Trabalho , Humanos , Feminino , Masculino , Local de Trabalho , Inquéritos e Questionários
14.
J Korean Med Sci ; 37(13): e101, 2022 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-35380026

RESUMO

The association between lung injury and exposure to humidifier disinfectant (HD) containing a mixture of chloromethylisothiazolinone (CMIT) and methylisothiazolinone (MIT) has been controversial in South Korea. This study conducts a literature review in order to evaluate the likelihood of CMIT/MIT reaching the lower part of the respiratory tract and causing lung injury. A literature review focused on the inhalation risk of HD containing a mixture of CMIT and MIT. The major contents included the physicochemical properties of CMIT and MIT contained in HDs and methodological reviews on substance analysis, toxicity tests and clinical cases. HD products marketed in South Korea have been reported to contain approximately 1-2% CMIT and 0.2-0.6% MIT along with magnesium nitrate (20-25%), magnesium chloride (0.2-1.0%), and water (70-75%). The types of CMIT and MIT dispersed into the air and deposited in the respiratory tract are assumed to be either gaseous substances or nanoparticles mixed with magnesium salts. The result of the literature review including clinical cases of lung injury among CMIT/MIT HD product users, demonstrated that these chemicals likely reach the lower respiratory tract and accordingly cause lung injury. A number of humidifier disinfectant-associated lung injury cases with clinical evidence should be prioritized in risk assessment of HD containing CMIT and MIT, even though there might be insufficient evidence in all related areas, including inhalation exposure assessment studies, animal testing, and epidemiological studies.


Assuntos
Desinfetantes , Lesão Pulmonar , Animais , Desinfetantes/toxicidade , Humanos , Umidificadores , Lesão Pulmonar/etiologia , Medição de Risco , Tiazóis
15.
J Occup Health ; 64(1): e12318, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-35152501

RESUMO

OBJECTIVE: Exposure to ultraviolet (UV) radiation from sunlight induces the production of essential vitamin D, whereas overexposure to sunlight leads to skin cancer. Sunlight exposure has been measured using questionnaires, dosimeters, and vitamin D levels. Several studies have measured vitamin D in the working population; however, these studies were limited to certain occupations such as farmers and construction workers. In the present study, we evaluated sunlight exposure using blood vitamin D as an exposure surrogate across industries and occupations. METHODS: The Korea National Health and Nutrition Examination Survey (KNHANES) is a nationwide study representing the Korean population. We analyzed data from KNHANES between 2008 and 2009. We examined the association between vitamin D levels and pertinent personal, seasonal, residential, and occupational factors. Furthermore, we developed a multiple regression model with factors other than occupational factors (industry and occupation) and obtained residual values. We computed the third quartile (Q3) of the residuals and then calculated the fractions exceeding the Q3 level for each combination of industry and occupation. RESULTS: Age, sex, body mass index, year, season, latitude, living area, living in an apartment, industry, and occupation were significantly associated with vitamin D levels. Based on the exceeding fraction, the armed forces showed the highest exceeding fraction level of 0.71. CONCLUSIONS: Our results present the high exposure groups to sunlight across industries and occupations. Our results may provide a source for prioritizing occupational groups with a high risk of adverse health effects from sunlight exposure.


Assuntos
Luz Solar , Vitamina D , Biomarcadores , Humanos , Inquéritos Nutricionais , Ocupações , Raios Ultravioleta
16.
Saf Health Work ; 12(4): 439-444, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34900362

RESUMO

BACKGROUND: In a previous study, we estimated exposure prevalence and the number of workers exposed to carcinogens by industry in Korea. The present study aimed to evaluate the optimal exposure intensity indicators of airborne lead exposure by comparing to blood lead measurements for the future development of the carcinogen exposure intensity database. METHODS: Data concerning airborne lead measurements and blood lead levels were collected from nationwide occupational exposure databases, compiled between 2015 and 2016. Summary statistics, including the arithmetic mean (AM), geometric mean (GM), and 95th percentile level (X95) were calculated by industry both for airborne lead and blood lead measurements. Since many measurements were below the limits of detection (LODs), the simple replacement with half of the LOD and maximum likelihood estimation (MLE) methods were used for statistical analysis. For examining the optimal exposure indicator of airborne lead exposure, blood lead levels were used as reference data for subsequent rank correlation analyses. RESULTS: A total of 19,637 airborne lead measurements and 32,848 blood lead measurements were used. In general, simple replacement showed a higher correlation than MLE. The results showed that AM and X95 using simple replacement could be used as optimal exposure intensity indicators, while X95 showed better correlations than AM in industries with 20 or more measurements. CONCLUSION: Our results showed that AM or X95 could be potential candidates for exposure intensity indicators in the Korean carcinogen exposure database. Especially, X95 is an optimal indicator where there are enough measurements to compute X95 values.

17.
Saf Health Work ; 12(3): 403-415, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34527403

RESUMO

BACKGROUND: This study aimed to assess the possibility of benzene exposure in workers of a Korean semiconductor manufacturing company by reviewing the issued patents. METHODS: A systematic patent search was conducted with the Google "Advanced Patent Search" engine using the keywords "semiconductor" and "benzene" combined with all of the words accessed on January 24, 2016. RESULTS: As a result of the search, we reviewed 75 patent documents filed by a Korean semiconductor manufacturing company from 1994 to 2010. From 22 patents, we found that benzene could have been used as one of the carbon sources in chemical vapor deposition for capacitor; as diamond-like carbon for solar cell, graphene formation, or etching for transition metal thin film; and as a solvent for dielectric film, silicon oxide layer, nanomaterials, photoresist, rise for immersion lithography, electrophotography, and quantum dot ink. CONCLUSION: Considering the date of patent filing, it is possible that workers in the chemical vapor deposition, immersion lithography, and graphene formation processes could be exposed to benzene from 1996 to 2010.

18.
Sci Rep ; 11(1): 17086, 2021 08 24.
Artigo em Inglês | MEDLINE | ID: mdl-34429439

RESUMO

This study aimed to evaluate the exposure levels and variation in airborne endotoxin and heavy metals such as aluminum, chromium (Cr), iron (Fe), manganese (Mn), nickel (Ni), zinc, and lead (Pb) in the three different South Korean subway environments (driver room, station office, and underground tunnel) and identify subway characteristics influencing endotoxin and heavy metals levels. Air samples were collected and analyzed using the kinetic Limulus Amebocyte Lysate assay and inductively coupled plasma mass spectrometers. The geometric mean was determined for endotoxin levels (0.693 EU/m3). It was also found that Fe (5.070 µg/m3) had the highest levels in subway environments while Pb (0.008 µg/m3) had the lowest levels. Endotoxin levels were higher in the underground tunnel and lower in the station office; the total heavy metal levels showed the same pattern with endotoxin levels. Endotoxins and total heavy metal levels were higher in the morning than at night. Positive correlations were found between endotoxin and Cr, Fe, Mn, and Ni levels. Given the correlation between airborne endotoxins and heavy metals, further studies with larger sample sizes are needed to identify the correlation between levels of airborne endotoxin and heavy metals.

19.
Nat Commun ; 12(1): 4520, 2021 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-34312387

RESUMO

Electron-phonon scatterings in solid-state systems are pivotal processes in determining many key physical quantities such as charge carrier mobilities and thermal conductivities. Here, we report direct probing of phonon mode specific electron-phonon scatterings in layered semiconducting transition metal dichalcogenides WSe2, MoSe2, WS2, and MoS2 through inelastic electron tunneling spectroscopy measurements, quantum transport simulations, and density functional calculation. We experimentally and theoretically characterize momentum-conserving single- and two-phonon electron-phonon scatterings involving up to as many as eight individual phonon modes in mono- and bilayer films, among which transverse, longitudinal acoustic and optical, and flexural optical phonons play significant roles in quantum charge flows. Moreover, the layer-number sensitive higher-order inelastic electron-phonon scatterings, which are confirmed to be generic in all four semiconducting layers, can be attributed to differing electronic structures, symmetry, and quantum interference effects during the scattering processes in the ultrathin semiconducting films.

20.
Saf Health Work ; 12(1): 74-95, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33732532

RESUMO

BACKGROUND: A job-exposure matrix (JEM) is an important surrogate indicator to evaluate past exposure levels. Although a Korean asbestos JEM has been constructed previously, this JEM includes only a few industrial and occupational groups. This study aimed to reconstruct the JEM by integrating the latest organized data to improve its utility. METHODS: We used recent Korean standard industry and occupation codes and extracted 36 articles from a systematic literature review to initiate the reconstruction of the previous Korean asbestos JEM. The resulting data consisted of 141 combinations of industrial and occupational groups. Data from the Netherlands's JEM were also reviewed and categorized into 70 industrial and 117 occupational groups by matching with the Korean data. We also utilized Germany's data, which consisted of 10 industrial and 14 occupational groups. RESULTS: The reconstructed Korean asbestos JEM had 141 combinations of industries and occupations. The time periods are from the 1980s to the 2000s in 10-year intervals. Most of the data were distributed between the 1990s and the 2000s. Occupations with high exposure to asbestos included knitting and weaving machine operators, automobile mechanics or assemblers, ship mechanics or assemblers, mineral ore and stone products processing mechanics, and metal casting machine operators or mold makers. CONCLUSIONS: The reconstructed Korean asbestos JEM has expanded the type and duration of the occupational groups of the previous JEM and can serve as an important reference tool for evaluating asbestos exposure and designing compensation and prevention policies in Korea.

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