• Title/Summary/Keyword: Generated aerosols

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The Microbial Contamination and Effective Control Method of Dental Unit Water System (치과용 유니트 수계의 미생물 오염 및 효과적인 관리 방법)

  • Yoon, Hye Young;Lee, Si Young
    • Journal of dental hygiene science
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    • v.15 no.4
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    • pp.383-392
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    • 2015
  • Dental chair unit (DCU) is the most essential equipment for the dental treatment in dentistry. DCU output water is used for various applications during dental treatment. DCU output water must be clean at the same level as drinking water since patients and dental staff are regularly exposed to water and aerosols generated from the DCU. Many studies demonstrated that DCU output water is frequently contaminated with microorganisms including opportunistic pathogen such as Legionella and Pseudomonas species. Thus, DCU output water may be a potential source of infection. In order to reduce microbial contamination levels in DCU output water, periodic management and continuous disinfection are necessary. Currently, there are a variety of disinfection methods for managing DCU output water and its efficacy is also diverse. We reviewed the level of microbial contamination, clinical implications of contaminated DCU output water and the various DCU disinfection methods.

Characteristics of Fine Particles Measured in Two Different Functional Areas and Identification of Factors Enhancing Their Concentrations (강원도 춘천과 영월에서 측정한 미세먼지 농도 특성 및 고농도 원인 분석)

  • Cho, Sung-Hwan;Kim, Hyun-Woong;Han, Young-Ji;Kim, Woo-Jin
    • Journal of Korean Society for Atmospheric Environment
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    • v.32 no.1
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    • pp.100-113
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    • 2016
  • In this study, the characteristics of $PM_{2.5}$ and $PM_{2.5-10}$ concentrations were identified in two different functional areas including Chuncheon and Youngwol, Korea. Even though the anthropogenic emission rates of $PM_{2.5}$ and $PM_{10}$ are approximately four times higher in Youngwol than in Chuncheon their atmospheric concentrations were statistically higher in Chuncheon. In Chuncheon, both $PM_{2.5}$ concentrations and the ratio of $PM_{2.5}/PM_{10}$ increased as relative humidity (RH) increased possibly because the inorganic and/or organic secondary aerosols were actively formed at high RH. This result was also supported by that $PM_{2.5}$ concentration was enhanced under the fog and mist conditions in Chuncheon. On the other hand, both $PM_{2.5}$ and $PM_{2.5-10}$ concentrations clearly increased with the southerly winds blown from the cement production facility in Youngwol. In addition, high $PM_{2.5-10}$ concentrations were observed with high wind speed, low relative humidity, and high $NO_2$ concentrations in Youngwol, suggesting that $PM_{2.5-10}$ was generated through the physical process including crushing and packing procedures followed by resuspension from cement and lime factory.

Analytical characterization of O3 samples prepared for investigation of tropospheric heterogeneous reactions

  • Kim, Mihyeon;Park, Jong-Ho
    • Analytical Science and Technology
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    • v.35 no.5
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    • pp.212-217
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    • 2022
  • In this study, ozone (O3) samples were prepared for investigating the heterogeneous reactions between O3 and tropospheric aerosols and were characterized by spectroscopic methods. O3 generated from an ozone generator was purified by selective adsorption on refrigerated silica gel, followed by transfer to a sample bulb. The amount of UV light (λ = 256 nm) absorbed by O3 was measured as a function of time at two different temperatures (room temperature and 50 ℃) and under different irradiation conditions. A correlation plot of 1/[O3] versus time showed that O3 decomposition follows the 2nd order reaction rate under a steady-state approximation. The initial concentration of O3, observed rate constants (kobs), and the half-life of O3 in the sample stored at room temperature were determined to be 2.74 [±0.14] × 1016 molecules·cm-3, 4.47 [±0.64] × 10-23 molecules-1·cm3·s-1, and 9.5 [±1.4] days, respectively. The evaluation of O3 stability under various conditions indicated that special care should be taken to prevent the exposure of the O3 samples to hightemperature environment and/or UV radiation. This study established a protocol for the preparation of highly purified O3 samples and confirmed that the O3 samples can be stored for a day after preparation for further experiments.

Elemental components analysis according to the size of fine particles emitted from a coal-fired power plant using an ejector-porous tube dilution sampling and ELPI (이젝터-다공튜브 희석 샘플링과 ELPI를 이용한 석탄화력발전소 배출 미세먼지의 입자 크기에 따른 성분 분석)

  • Shin, Dongho;Park, Daehoon;Joe, Yunhui;Kim, Younghun;Hong, Kee-Jung;Lee, Gunhee;Han, Bangwoo;Hwang, Jungho
    • Particle and aerosol research
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    • v.18 no.3
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    • pp.69-77
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    • 2022
  • In order to understand the characteristics of fine particles emitted from coal-fired power plant stacks, it is important to analyze the size distribution and components of particles. In this study, particle size distributions were measured using the ejector-porous tube dilution device and an ELPI system at a stack in a coal-fired power plant. Main elemental components of particles in each size interval were also identified through TEM-EDS analysis for the particles collected in each ELPI stage. Particle size distributions based on number and mass were analyzed with component distributions from 0.006 to 10 ㎛. The highest number concentration was about 0.01 ㎛. The main component of the particles consisted of sulfur, which indicated that sulfate aerosols were generated by gas-to-particle conversion of SO2. In a mass size distribution, a mono-modal distribution with a mode diameter of about 2 ㎛ was shown. For the components of PM1.0 (particles less than 1 ㎛), the abundance order was F > Mg > S > Ca, and however, for the components of PM10 (particles less than 10 ㎛), it was in the order of Fe > S > Ca > Mg. The elemental components by particle size were confirmed.

An Analysis of Aerosol Mass Concentrations and Elemental Constituents Measured at Cheongwon depending on the Backward Trajectories of Air Parcel in East Asia in 2011 (2011년 동아시아에서 기류의 이동 경로에 따른 청원에서 측정한 에어로졸 질량 농도 및 원소 성분 분석)

  • Kim, Hak-Sung;Byun, Kwang-Tae;Chung, Yong-Seung;Choi, Hyun-Jung;Kim, Min-Jung
    • Journal of Environmental Science International
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    • v.21 no.7
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    • pp.855-863
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    • 2012
  • This study analyzed mass concentrations of TSP, PM10 and PM2.5 and elemental constituents according to the isentropic backward trajectories of air parcel from Cheongwonin East Asia during the period January - October, 2011. Mass concentrations of the continental polluted airflow (CP) showed levels of TSP and PM10 mass concentrations higher than the continental background airflow (CB). Also, PM2.5 mass concentrations of anthropogenic fine particles ran higher in CP than in CB. The elemental constituents and elemental constituent ratio ended up varying depending on the origin of atmospheric aerosols generated. The average absolute content of elemental constituents reached its height in CB, the ratio of anthropogenically originating elements (PE) among the all elements (AE) analyzed marked a high in CP, and Mg+Na/AE reached its height in the oceanic airflow (OA). At the same time, TSP, PM10 and PM2.5 mass concentrations, the ratio of PM2.5/TSP and PE/AE element ratio ran higher in CP than CB. Episodes of large-scale transport of atmospheric pollutants as observed at Cheongwon were 8 cases and 22 days. The ratios of PM10, PM2.5 among TSP mass concentrations showed different results and the ratios of PM2.5 showed an increasing trend in the episodes of anthropogenic air pollution transport. Overall, dustfall episodes show a level of elemental constituents higher than those of anthropogenic air pollution.Dustfall episodes were observed to contain more of Fe, Al and Ca originating from continental soils and those of air pollution were observed to contain more of Zn, Mn, Cu and Pb. By difference in contents of absolute elemental constituents, episodes of anthropogenic air pollution showed a high PE/AE rate, and dustfall episodes a high SE/AE rate.

The effect of chlorhexidine on reduction of viable organisms in aerosol produced by ultrasonic scaler (클로르헥시딘이 초음파 치석제거기에 의해 발생된 에어로졸 내 세균 수에 미치는 영향)

  • Son, Woo-Kyung;Shin, Seung-Yun;Kye, Seung-Beom;Yang, Seung-Min
    • Journal of Periodontal and Implant Science
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    • v.39 no.3
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    • pp.303-310
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    • 2009
  • Purpose: The aerosol generated by ultrasonic scaler can contain bacteria or virus which can penetrate into body through respiratory systems of dentists, dental hygienist or patients. The aim of this study is to evaluate the effect of chlorhexidine digluconate as preoperative mouthrinse or lavage for ultrasonic scaler on the reduction of viable organisms in aerosol produced during periodontal treatment using ultrasonic scaler. Methods: 30 patients with moderate chronic periodontitis were included and divided into 3 groups: Control (no preoperative mouthrinse and tap water as lavage), CHG (preoperative mouthrinse with 0.1% chlorhexidine digluconate and tap water as lavage), CHL (no preoperative mouthrinse and 0.1% chlorhexidine digluconate as lavage). Each patient received scaling or subgingival curettage for 30 min. In CHG group, mouthrinse with chlorhexidine digluconate was performed for 1 min. before treatment. Before, during and after scaling or subgingival curettage, air sampling was performed for 7 min. each (1000 L/7 min.) with trypticase-soy agar plate. Agar plates were incubated in $37^{\circ}C$ aerobically. The numbers of colony-forming units (CFU) were counted and compared. Results: The numbers of CFUs of the samples obtained during treatment were $97{\pm}14.0$ in control, $73.1{\pm}14.9$ in CHG group and $44.5{\pm}9.0$ in CHL group. The difference among the 3 groups was determined to be statistically significant (one-way ANOVA with Bonferroni's correction, p-value: 0.0003). In contrast, the numbers of CFU of samples obtained before and after treatment were not significantly different among the groups. Conclusions: Chlorhexidine digluconate used as preoperative mouthrinse or lavage for ultrasonic scaler can reduce the microorganisms in aerosol produced during periodontal treatment using ultrasonic scaler. Less number of microorganisms were detected when chlorhexidine was used as lavage for ultrasonic scaler.

Evaluation of Filtration Performance Efficiency of Commercial Cloth Masks (시판되고 있는 유사마스크 제품의 여과효율성능 비교평가)

  • Jang, Ji Young;Kim, Seung Won
    • Journal of Environmental Health Sciences
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    • v.41 no.3
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    • pp.203-215
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    • 2015
  • Objectives: This study was designed to evaluate the filtration efficiencies and pressure drops of five commercial cloth masks (4 plate type, 1 cup type) in comparison to the performance of a class 1 disposable respirator (reference respirator). A further objective was to evaluate the effects of the number of layers and wash treatment independently on filtration efficiencies and pressure drops. Methods: Polydisperse NaCl aerosols were generated in an aerosol chamber and their concentrations were measured by an optical particle counter (OPC) in the size range of $0.3{\sim}10{\mu}m$ (five channels). Results: The filtration efficiencies of the five cloth masks and the reference respirator were D: 9.5%, C: 18.5%, E: 23.6%, A: 28.5%, B: 29.7% and R: 91.1%, respectively, and the pressure drops through them were C, D: 0.8 Pa, E: 1.7 Pa, B: 6.4 Pa, A: 42.7 Pa and R: 19.3 Pa, respectively. The filtration efficiencies of the cloth masks and reference respirator were below the class 1 respirator criterion (${\geq}94.0%$) of the Ministry of Employment and Labor (MOEL) and Ministry of Food and Drug Safety (MFDS). The pressure drops satisfied the class 1 respirator criterion (${\leq}70Pa$) of MOEL and MFDS. When the cloth masks were folded into two and four layers, the filtration efficiencies of cloth masks A, B, C, D (plate type) increased 1.7-4.6 times, and 2.3-6.8 times, respectively, compared to the efficiencies of the same products in a single layer. Pressure drops increased as the number of layers was increased. The filtration efficiency of cloth mask E with a liner was 1.3 times higher than that of the same mask without a liner, and the pressure drop was lower in the no-liner configuration. After a single washing, the filtration efficiencies of all the cloth mask products decreased 1.04-4.0 times compared to those of the same products intact. For the cloth masks C and E, their filtration efficiencies were significantly decreased after washing (p<0.05). The pressure drops of all cloth masks were 1.2-2.0 times lower after washing. Conclusions: The filtration efficiencies of the five cloth masks were below 30% and did not improve greatly by increasing the number of layers. After a single washing, their performances decreased. Considering the above and other issues identified with cloth masks, such as poor fit and stretched fibers through use, people should not expect protection against particulate matters from the cloth masks on the market.

Mucociliary Clearance in the Children with Bronchial Asthma (기관지 천식 환아에서의 점액섬모 청소율(Mucociliary Clearance))

  • Lee, Myung-Hyun;Sun, Yong-Han;Nam, Seung-Gon;Koh, Young-Yull;Chung, June-Key
    • Tuberculosis and Respiratory Diseases
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    • v.43 no.2
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    • pp.173-181
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    • 1996
  • Background : Several studies have suggested that impaired mucociliary clearance plays a role in the pathophysiology of bronchial asthma. Cough productive of mucoid sputum is common, and mucous plugs in the airways are frequently observed. These clinical features are in keeping with the histologic lesions of asthma, which involve primarily the epithelial and mucous-producing structures of the conducting airways. Some studies have shown that the mucociliary clearance is impaired in adult asthma, but it has not been studied in childhood asthma. The objectives of this study were to examine whether the mucociliary clearance is impaired in childhood asthma and to estimate the degree of impairment in comparison with that of immotile cilia syndrome. Method : Thirteen children with mild stable asthma and eight patients with immotile cilia syndrome completed this study. Ten healthy children were recruited as a normal control group. The whole-lung mucociliary clearance was measured by the radioaerosol technique. Aerosols, tin colloid particles tagged with the radionuclide technetium-99m($^{99m}Tc$), were generated by means of nebulizer, and inhaled via a mouthpiece. The retention of radioactivity was measured at 30, 60, 90 and 120 minutes by gamma camera, and mucociliary clearance was calculated as percent retention at each time. Results: 1) In each subject, the percent retention decreased variably with the lapse of time. 2) The percent retention of radionuclide decreased at each time in order of normal control, bronchial asthma and immotile cilia syndrome and the percent retention of immotile cilia syndrome was significantly higher than that of normal control at each time(p<0.05). 3) At two hours, the percent retention of bronchial asthma($65.0{\pm}1.8$(SE)%) was significantly higher than that of the normal control($54.4{\pm}3.5%$, p<0.05), and significantly lower than that of immotile cilia syndrome($73.3{\pm}1.4%$, p<0.01). 4) When the percent retention was analyzed according to $PC_{20}$ in the children with bronchial asthma, they had no relationship with each other. Conclusion: Mucociliary clearance in the children with bronchial asthma was significantly lower than normal control. This finding indicates that impaired mucociliary clearance operates in childhood asthma as well, and suggests that it may be one contributing factor in the pathogenesis of asthma. The degree of impairment, however, was not so severe as immotile cilia syndrome.

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