• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.17 no.2
• /
• pp.81-88
• /
• 2007

The aim of this study was to investigate whether the exposure to vinyl chloride monomer(VCM) induces lipid peroxidation in workers by evaluating the concentration of malondialdehyde(MDA) in the urine in order to assess worker's oxidative stress due to exposure of vinyl chloride monomer. The subjects investigated in the study were divided into the experimental group; 18 workers exposed to VCM, and the control group; 19 workers unexposed to VCM. A gas chromatography/pulsed flame photometric detector(GC/PFPD) was utilized to analyze thiodiglycolic acid(TDGA), which was methylated with trimethylsilyldiazomethane (2.0M in diethyl ether) in urine and the urinary MDA, the product of lipid peroxidation, was determined by high-performance liquid chromatography/ultraviolet-visible detector after derivatized with 2,4-dinitrophenylhydrazine(DNPH). The concentrations of urinary TDGA in controls and VCM exposure workers were 0.13(2.01)mg/g Cr. GM(GSD) and 0.35(1.96)mg/gCr. GM(GSD), respectively. The concentrations of urinary MDA were $0.12(2.21){\mu}mol/gCr$. GM(GSD) in controls and $1.35(1.79){\mu}mol/gCr$. GM(GSD) in VCM exposure workers. As a result of simple regressions analysis between urinary concentration of TDGA and MDA in VCM exposure workers, it was found that the $R^2$ value was 0.261 (p=0.03) and the drinking and smoking did not affect their level. In conclusion, the workers exposed to VCM have a potentially to suffered by oxidative stress due to VCM exposure and the urinary MDA can be applicable to the marker of effect to assess the level of worker's VCM exposure.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.16 no.2
• /
• pp.131-144
• /
• 2006

For the purpose of preparing the fundamental data on working environment of small scale manufacturing industries and preventing the occupational diseases of workers in these industries, authors surveyed the status of working environment to several chemical substances and physical agents by types of industry and types of process in the small scale manufacturing industries with less than five workers in Gimhae including 235 workplaces, 14 types of industry and 25 types of process from January 2002 to December 2004. This measurement method was work environment measurement method (established in Ministry of Labor, Korea), analytical methods (2nd Ed.) of Occupational Safety and Health Administration (OSHA) and manual of analytical methods (4th Ed.) of National Institute for Occupational Safety and Health (NIOSH) and collected data was analyzed by using SPSS 10.0 for windows, the results were as follows: 1. Noise generated in 14 types of industry and 22 types of process. an actual level of mean exposure (90.7 dB(A)) exceeded threshold limit values (TLVs) in manufacture of other transport equipment. An actual level of mean exposure (90.2dB) exceeded TLVs in the process of wire-drawing and 90.4dB in the process of wire-stranding. 2. Dusts of type I, II, III were generated in 9 types of industry and 8 types of process. Its mean concentration did not exceed TLVs. 3. Heavy metals (Pb, Mn, Cr, Ni) were generated in 7 types of industry and 7 types of process. Its mean concentration did not exceed TLVs. 4. 16 kinds of organic solvents were generated in 11 types of industry and 6 types of process. Its mean concentration did not exceed TLVs. As the above results, chemical substances and physical agents were generated in the several different types of industry and process of the manufacturing industry with less than five workers, and only mean level of noise was exceeded TLVs. In case of exceeding threshold limit values, improvement of work environment is actively needed, and work environment management should be performed continuously for prevention of an occupational diseases and work related diseases.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.26 no.1
• /
• pp.11-19
• /
• 2016

Objectives: Exposure to volatile organic compounds such as trichloroethylene(TCE) and perchloroethylene(PCE), along with Agent Orange, that were issued around Camp Carroll US Army Base situated in Waegwan, Chilgok-gun, Gyeongsangbuk-do Province, Korea. The main objective of this study was to assess the exposure to TCE and PCE of residents of the area surrounding Camp Carroll. Methods: The TCE, PCE and trichloroethanol(TCEOH) concentrations in blood and trichlroroacetic acid(TCA) and TCEOH concentrations in urine were measured and analyzed in a total of 1,033 residents around Camp Carroll. TCA and TCEOH are metabolites of TCE and PCE, respectively. The information on demographic characteristics and exposure variables in relation to underground water were obtained through a questionnaire completed by the subjects. Results: TCE, PCE and TCEOH concentrations were not detected in blood. Detection rates of TCA and TECOH concentrations in urine were 98.5% and 36.6%, respectively. Creatinine-corrected average TCA and TCEOH concentrations were $12.23{\pm}23.81{\mu}g/g$ and $0.66{\pm}4.31{\mu}g/g$, respectively. A significant difference was not shown between the drinking group and no drinking group for underground water, which was assumed as a potential route of exposure to TCE and PCE through the consumption of ground water. However, females drinking ground water showed a significantly higher mean level of TCA in urine than did males. There was no significant difference according to drinking ground water as a potential source of exposure to TCE and PCE in residents around Camp Carroll. Conclusions: Considering the statistical analysis of factors affecting exposure to TCE and PCE in ground water along with previous reports, TCA in urine as exposure to TCE and PCE might not be appropriate because it is found in chlorinated drinking water. Therefore, TCA concentration in urine may be the result of drinking of chlorinated water.

• Journal of Digital Convergence
• /
• v.12 no.10
• /
• pp.445-453
• /
• 2014

The purpose of this study was to examine the necessity of oral health education to analyze the knowledge and status of oral health according to smoking in some college students. The subjects in this study were 217 selected college students, on whom a survey was conducted from September 3 to September 7, 2013. The data were analyzed using SPSS 19.0(SPSS 19.0 K for window, SPSS Inc USA). The findings of the study were as follows: First, concerning toothbrushing frequency, the smokers brushed their teeth twice, and the nonsmokers did that three times(p<0.05). The male students did toothbrushing twice, and the female students did that three times(p<0.05). As to scaling experience, the female students got their teeth cleaned more often(p<0.05). Second, the nonsmokers who had received oral health education outnumbered the smokers who had(p<0.01). In regard to the necessity of smoking-related oral health education, both of the smokers and the nonsmokers replied it was necessary(p<0.05). Third, as for the level of oral health knowledge, the nonsmokers were more aware than the smokers that the use of oral hygiene supplies had an effect on the prevention of dental caries(p<0.05). Given the findings of the study, the smoking-related oral health education and the development of programs that are intended for college students seems necessary.

• Journal of dental hygiene science
• /
• v.4 no.3
• /
• pp.111-115
• /
• 2004

This study was aimed to establish the self-concept as the dental profession and dedicate to the development of dental hygienist role by understanding the relation between the self-concept of dental hygienist and practice performance as dental hygienist. Following the thorough investigation of this correlation, the importance of self-concept as the dental profession was confirmed, and the understanding about the practice performance as dental hygienist was renewed. Dental hygienist working in dental clinic located in Jeonju city, Jeollabuk-Do were selected as the subjects of this study, and the materials were collected from Mar. 11 to Mar. 25, 2002 for 15 days. SPSS was used for analysis of data to deal with ANOVA and verification of Pearson correlation. The results of this research can be summarized as follows; 1. In comparison of the degree of professional self-concept according to the general characteristics of the subjects, there were significant differences in religion(p<.05) and educational background(p<.01). 2. In comparison of the degree of practice performance according to the general characteristics of the subjects, the results showed the significant difference in religion(p<.05). 3. There were highly significant correlation between the professional self-concept and practice performance as dental hygienist(F=.663, p<.001).

• Journal of dental hygiene science
• /
• v.9 no.4
• /
• pp.405-412
• /
• 2009

The purpose of this study investigated the effect of Au coating on adhesion between porcelain matrix and metal substructure interface. Titanium, Ni-Cr alloy and Co-Cr alloy are well known as proper metal for the dental restorations. The success of a porcelain fused to metal (PFM) restoration depends upon the quality of the porcelain-metal bond. However, adhesion between dental alloys and porcelain is related to diffusion of oxygen during ceramic firing. The excessive oxidized layers make hard adhesion between dental alloy and ceramic. Ni-Cr and Co-Cr specimens were divided into test and a control group and Titanium specimens were divided into three test groups and a control group. Each group had 20 specimens. The adhesion characteristics of porcelain and metal with Au coating layer and without Au coating layer were observed with scanning electron microscopy(SEM). The adhesion was evaluated by a biaxial flexure test and volume fraction of adherent porcelain was determined by SEM/EDS analysis. Result of this study suggest that Au coating layer is effective barrier to diffuse oxide layer completely protect non-precious alloys from oxidation during the porcelain firing. The SEM photomicrographs of cross-section specimens showed a smooth interface between Au coating layer and metals and porcelain which suggested proper chemical bonding, and no gap, porosity were observed. The mode of failure was mainly adhesive for Ti tested specimens, but mixed failures with adhesive and cohesive were observed in Ni-Cr and Co-Cr specimens. The adhesion between non-precious metals and porcelain would not be improved by Au coating agent. However, It is suggested that the continuous study is required further investigation and development.

• The Journal of the Convergence on Culture Technology
• /
• v.4 no.1
• /
• pp.57-65
• /
• 2018

The purpose of this study was to investigate the factors affecting the actual condition and effectiveness of orthodontic treatment among some dental hygienists and students. This study was carried out from September to December, 2016 to describe the purpose of the study and the method of writing the questionnaire for some dental hygienists and students. The final 430 sections were analyzed and analyzed using PASW Statistics 18.0. First, the duration of orthodontic treatment was 34.4% for college students, 36.9% for orthodontic treatment for less than 2 ~ 3 years, and 62.3% for internal motivation. The factors affecting the orthodontic treatment effect were the patient's cooperativeness and the hospital's scale was the lowest. The higher the grade level, the more the clinical experience and dental part-time experience were, the higher the correlation between dental specialty and dental hygienist's medical service, education and counseling was .521(P<0.001). The higher the level of cooperation, the higher the grade level, the more dental treatment and orthodontic treatment experience, the lower the level of family co - operation. Therefore, it is important to emphasize the importance of cooperation of orthodontic patients and to develop a strategic program for each individual patient.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.28 no.1
• /
• pp.1-17
• /
• 2018

Objectives: This research is part of a study to be conducted over five years starting from 2017 by the Ministry of Environment on the development of technologies to evaluate the impact of chemical accidents on the human body. Methods: For this research, a five-stage specific study method was developed. Results: In brief, the developed health risk assessment method can be summarized as follows. First, a health risk assessment system was built based on the guidelines set forth by the USA NRC/NAS. Second, based on the disease manifestation theory, the health risk assessment method was divided into 1) a carcinogenic health risk assessment method focused on all carcinogens except non-genotoxic carcinogens and 2) a non-carcinogenic health risk assessment method focused on noncarcinogens including non-genotoxic carcinogens. Third, the detailed contents of the health risk assessment method were developed in four stages(hazard identification, dose-response assessment, exposure assessment, and risk determination) through theoretical consideration of the assessment of the level of health risk related to chemical exposure. Finally, a health risk assessment methodology, classified into stages to address acute, subacute/subchronic, and chronic conditions was developed after considering the physicochemical behavior of hazardous chemicals upon implementation of countermeasures after a chemical accident. Conclusions: A method to evaluate the health risks related to toxic chemicals generated by chemical accidents was developed. This study was performed with the purpose of developing a mathematical health risk assessment method to evaluate the health effects of exposure to hazardous chemicals upon implementation of emergency countermeasures after chemical accidents.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.28 no.1
• /
• pp.61-79
• /
• 2018

Objectives: The objective of this study was to examine the effect of non-thermal dielectric barrier discharge(DBD) plasma on decontamination of Staphylococcus aureus(S. aureus) and Escherichia coli(E. coli) as common pathogens. Methods: This experiment was carried out in a chamber($0.64m^3$)designed by the authors. The plasma was continuously generated by a non-thermal DBD plasma generator(Model TB-300, Shinyoung Air tech, Korea). Suspensions of S. aureus and E. coli of 0.5 McFarland standard($1.5{\times}10^8CFU/mL$) were prepared using a Densi-Check photometer(bio $M{\acute{e}}rieux$, France). The suspensions were diluted1:1000 in sterile PBS solutions(approximately$10^{4-5}CFU/mL$) and inoculated on tryptic soy agar(TSA) in Petri dishes. The Petri dishes(80mm internal diameter)were exposed to the non -thermal DBD plasma in the chamber. Results: The results showed that 95% of S. aureus colonies were killed after a six-hour exposure to the DBD plasma. In the case of E. coli, it took two hours to kill 100% of the colonies. The gram-negative E. coli had a greater reduction than the gram-positive S. aureus. This difference may be due to the structure of their cell membranes. The thickness of gram-positive bacteria is greater than that of gram-negative bacteria. The S. aureus is more resistant to DBD plasma exposures than is E. coli. It should be noted that average concentrations of ozone, a byproduct of the DBD plasma generator, were monitored throughout the experiment and the results were well below the criteria, 50 ppb, recommended by the Korean Ministry of the Environment. Thus, non-thermal DBD plasma is deemed safe for use in hospital and public facilities. Conclusions: There was evidence that non-thermal DBD plasma can effectively kill S. aureus and E. coli. The results indicate that DBD plasma technology can greatly contribute to the control of infections in hospitals and other public and private facilities.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.31 no.4
• /
• pp.427-439
• /
• 2021

Objectives: This study aims to investigate differences in microbial contamination according to the duration and environment of mask wearing. Methods: Forty-five participants were recruited from workers in an offices, multi-purpose facilities, and a schools. After wearing of KF94 mask for two. four, and six hours, the microorganisms adsorbed on the outer and inner layers of the mask were inoculated on BAP(Blood Agar Plate), Chocolate agar, and SDA plates. The bacterial count (CFUs: colony-forming units) cultured in each plate was measured and analyzed for changes in filtration efficiency. Results: The microbial contamination of masks worn in classrooms, offices, and multi-purpose facilities showed a significant difference depending on the environment (p<0.000). The measured CFUs increased significantly according to the time wearing the mask. The difference between the inner and outer layers of the mask was also significant (p<0.05). However, there was no statistical difference in the filtration efficiency of the masks by duration time (p=0.515). Conclusions: Masks worn by workers in the offices, multi-purpose facilities, and schools showed an increase of microbial contamination with the amount of time wearing the mask. The results indicate that the masks used in daily life may have adverse health effects if they are worn for a long time or reused over several days without the realizing that the masks can be contaminated with biological hazards. Guidelines on the safe threshold time for mask use should be established through further research.