• Journal of Environmental Health Sciences
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• v.47 no.6
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• pp.521-529
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• 2021

Background: The coronavirus disease (COVID-19) has caused changes in human activity, and these changes may possibly increase or decrease exposure to fine dust (PM_2.5). Therefore, it is necessary to evaluate the exposure to PM_2.5 in relation to the outbreak of COVID-19. Objectives: The purpose of this study was to compare and evaluate the exposure to PM_2.5 concentrations by the variation of dynamic populations before and after the outbreak of COVID-19. Methods: This study evaluated exposure to PM_2.5 concentrations by changes in the dynamic population distribution in Guro-gu, Seoul, before and after the outbreak of COVID-19 between Jan and Feb, 2020. Gurogu was divided into 2,204 scale standard grids of 100 m×100 m. Hourly PM_2.5 concentrations were modeled by the inverse distance weight method using 24 sensor-based air monitoring instruments. Hourly dynamic population distribution was evaluated according to gender and age using mobile phone network data and time-activity patterns. Results: Compared to before, the population exposure to PM_2.5 decreased after the outbreak of COVID-19. The concentration of PM_2.5 after the outbreak of COVID-19 decreased by about 41% on average. The variation of dynamic population before and after the outbreak of COVID-19 decreased by about 18% on average. Conclusions: Comparing before and after the outbreak of COVID-19, the population exposures to PM_2.5 decreased by about 40%. This can be explained to suggest that changes in people's activity patterns due to the outbreak of COVID-19 resulted in a decrease in exposure to PM_2.5.

• Journal of Korean Neurosurgical Society
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• v.29 no.9
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• pp.1161-1170
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• 2000

Objective : The transverse hippocampal slice is one of the most commonly studied in vitro models of mammalian brain physiology. However, despite its broad usage, there has been no standardization of slice preparation techniques or recording condition. It is well known that variations in recording conditions can result in profound different effects to neuronal responses. Evoked field potentials, recorded extracellularly, were used to investigate the effects of variations in hippocampal slice preparation protocol on hypoxia responses of CA1 neurones. Material & Methods : Before hypoxic injury, hippocampal slices were incubated for 4 hours. During incubation period, the slices were placed in a incubation chamber($21^{\circ}C$) for recovery from preparation injury and then transferred to recording chamber($34^{\circ}C$) for more recovery and baseline electric recording with current stimulation(0.1Hz). Various time periods in incubation chamber and recording chamber were applied to each experimental group(group 1=60min : 180min, group 2=90min : 150min, group 3=180min : 60min, time in incubation chamber : time in recording chamber) before 10 min hypoxia produced by replacing 95% $O_2$+5% $CO_2$ mixed gas to 95% $N_2$+5% $CO_2$ gas. Calcium, Magnesium ions and several drugs effecting on glutamate receptor also were studied. Recoveries from hypoxic injury of hippocampal slices were estimated by percent recovery of population spike(PS). Statistic analysis of study were performed using paired t-test. Results : The percent recovery of PS after 10min hypoxia was considerably enhanced by increasing the period of current stimulation during incubation period before hypoxic injury. Temperature effect on the result of this experiment was also studied(group 4) but the result from this showed no statistic significance. Low magnesium ion concentration of artificial CSF(Mg-free aCSF) during incubation period enhanced the recovery of PS but low calcium (calcium-free) and high magnesium ion concentration(2mM) reduced it after hypoxic injury. L-glutamate($100{\mu}M$) and AP-5($50{\mu}M$) had no effect on the recovery of PS but CNQX($10{\mu}M$) in artificial CSF during incubation period markedly enhanced the recovery of PS. Co-treatment of AP-5($50{\mu}M$), CNQX($10{\mu}M$) and high magnesium concentration(2mM) enhanced recovery of PS in immediate following period of hypoxic injury but the effect of cotreatment after then decayed rapidly and lost statistic significance. Conclusions : Judging from above results, the condition of baseline recording is important in observing the recovery of population spike after hypoxia, and the time and the condition should be controled more strictly to obtain reliable results.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.5
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• pp.3105-3108
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• 2013

Background: This study used National Health and Nutrition Examination Survey III to study the relationship between blood lead concentration and all cause, all cancer and lung cancer mortality in adults. Patients and Methods: Public use National Health and Nutrition Examination Survey (NHANES III) data were used. NHANES III uses stratified, multistage probabilistic methods to sample nationally representative samples. Household adult, laboratory and mortality data were merged. Sample persons who were available to be examined in aMobile Examination Center (MEC) were included in this study. Specialized survey analysis software was used. Results: A total of 3,482 sample participants with complete information for all variables were included in this analysis. For all cause death, the odds ratios (S.E.) for statistically significant variables were body mass index, 1.03 (1.01-1.06); 1.01 (1.01-1.01); blood lead concentration, 1.05 (1.01-1.08); poverty income ratio, 0.823 (0.76-0.89); and drinking hard liquor, 1.01 (1.00-1.02). For all cancer mortality, the odds ratios (S.E.) of the statistically signigicant variables were: age, 1.01 (1.01-1.01); blood lead concentration, 1.07 (1.04-1.12), black race, using non-Hispanic white as reference, 1.69 (1.12-2.56); and smoking, 1.02 (1.01-1.04). For lung cancer mortality, the odds ratios (S.E.) of the statistically significant variables were: age, 1.01(1.01-1.01); blood lead concentration, 1.09 (1.05-1.13); Mexican Americans, using non-Hispanic white as refrence, 0.33 (0.129-0.850); other races, 1.80 (0.53-6.18); and smoking, 1.03 (1.02-1.05). Conclusion: Blood lead concentration correlated with all cause, all cancer, and lung cancer mortality in adults.

• Biomedical Science Letters
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• v.11 no.2
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• pp.143-152
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• 2005

To investigate the exposure effect of polycyclic aromatic hydrocarbons (PAHs), we analyzed the relationship between urinary 8-hydroxydeoxyguanosine (8-OHdG) concentration and PAHs exposure. The study population contained 44 workers in steel-pipe coating and paint manufacture industries. We measured airborne total PAHs as an external dose, urinary 1-hydroxypyrene (1-OHP) as an internal dose of PAHs exposure, and urinary 8-OHdG as an effective dose of oxidative DNA damage. There was significant correlation between the urinary concentration of l-OHP and the environmental concentration of PAHs, pyrene, urinary cotinine, AST, and GGT. The mean of urinary 8-OHdG was $17.07\pm1.706{\mu}g/g$ creatinine in workers exposed to airborne PAHs. There was significant correlation between the urinary concentration of 8-0HdG and the airborne concentration of PAHs. From the results of stepwise multiple regression analysis about 8-OHdG, significant independents was total PAHs. In this study, there were significant correlation between the urinary concentration of 8-OHdG and the airborne concentration of PAHs. The urinary 1-OHP was effective index as a biomarker of airborne PAHs in workplace. But it was influenced by non-occupational PAHs source, smoking and biomarkers of liver function test.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.20 no.4
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• pp.1-13
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• 2017

The purpose of this study is to analyze a term of decade of water quality data of the Mulgum intake station on the Nakdong river(dam) to find the cause of algal blooms and to set an alternative to prevent artificial lake water pollution. Our study shows that water quality changes have regular periodic regularity and there was a certain correlation between specific analytical items. According to the analysis results of each factor, the decline in precipitation was not the main reason for algal blooms. TP concentration had a slight effect on Chl-a concentration but was not a limiting nutrient of a bloom. TN concentration had a strong correlation with Chl-a and strongly negative correlation with temperature, but was not a bloom's limiting nutrient, and was only a dependent variable. As the temperature was negatively correlated with the Chl-a concentration, it is found that the aspect of the ecological influence of the temperature was the most important factor of the phytoplankton concentration change. The N/P ratio lies under a power function with a high degree of reliability by the TP concentration, and the phenomenon appeared to be the same as the results of two other comparative areas. This result confirms that TN is dependent on TP and the biota in the lake that TN is a dependent variable whose concentration is determined by TP it. In conclusion, the increase in lake bloom is the result of a food chain change, and it is necessary to control the ecosystem by the food chain in the lake in order to reduce the lake's bloom. In particular, it is important to keep the benthic ecosystem as wide as possible in the aerobic state.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.21 no.2
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• pp.90-98
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• 2011

Objectives: The aim of this study was to evaluate the level of urinary mercury and analyze which factors would affect urinary mercury concentration among dental hygienists in dental clinics. Methods: This study conducted by questionnaire and detection of urinary mercury concentration of 268 dental hygienists working in dental clinics from July to August of 2009. Data collected from two hundred and thirty-five dental hygienists were analyzed by the geometric mean (GM). Analytical results of urine samples with less than 0.3 g creatinine/L and greater than 3g creatinine/L were excluded from statistical analysis. Results: Urinary mercury concentration of 235 dental hygienists showed the geometric distribution. The arithmetic and geometric means of urinary mercury concentration were $0.996{\mu}g/g$ creatinine and $0.755{\mu}g/g$ creatinine, respectively. From multiple regression analysis, the number of amalgam filling, the consumption frequency of raw fish and the number of amalgam handling in current workplace was revealed as increasing factors of urinary mercury concentration. Conclusions: The level of urinary mercury in dental hygienists was higher than in general Korean population. The number of amalgam filling, the consumption frequency of raw fish and the number of amalgam handling in current workplace was revealed as increasing factors of urinary mercury concentration. Therefore using resin materials instead of amalgam in dental clinics is highly desirable.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.449-455
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• 2018

This study was conducted to analyze the correlation between changes in white matter and homocysteine concentration through brain computed tomography of healthy 50-75 year old subjects without stroke or dementia history. We studied 722 out of 900 patients who underwent health screening at one hospital from 2016 to 2017. Based on the medical records, retrospective studies were conducted and analyzed using SPSS. A chi-square test, T-test and univariate logistic regression analysis were used for analysis. After the subjects were divided into the group with and without white matter changes, the population characteristics were analyzed. The mean age, homocysteine concentration and prevalence of hypertension and diabetes were higher and the duration of education was shorter in the group with white matter changes. In the group with white matter changes, the population increased as homocysteine concentration increased. When the odds ratio was compared based on the lowest group (Q1), age [p<0.001], hypertension [p<0.001] and hyperhomocysteinemia [p=0.021] were risk factors for white matter changes. We also identified modifiable risk factors such as hypertension and hyperhomocysteinemia to prevent complications of white matter changes. However, there has been no report of risk for the each causes of hyperhomocysteinemia and relationship between white matter changes and homocysteine concentration in Koreans. Therefore, large scale prospective studies are needed to better understand this topic.

• Journal of Nutrition and Health
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• v.34 no.4
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• pp.440-448
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• 2001

As diverse physiological functions of taurine have been reported, taurine-containing health drinks and products are marketed worldwide for the treatment of various conditions such as improvements of liver, heart and circulatory functions or as an aid to athletic performance. Although animal studies have shown that taurine is fairly safe when supplemented in the diet for an extended period, the effective dose range of taurine for dietary supplements is in controversy. Reports on dietary taurine intakes have been sparse, and would serve as a guideline for determining an appropriate taurine dosage. The present study was aimed to estimate dietary intake level of taurine using the taurine content database of commonly used food stuffs established recently in our laboratory, and also to evaluate plasma concentration and urinary excretion of taurine in adolescents and adults residing in Seoul area. Dietary taurine intakes of the subjects were 219$\pm$16.9mg/day for 16-19 years old(n=123), 177$\pm$18.1mg/day for adults older than 20 years old(n=123). Male subjects(n=115) consumed 216$\pm$21.1mg of taurine/day, while female subjects(n=131) consumed 181$\pm$14.3mg of taurine/day(p<0.05). The level of dietary taurine intake was positively correlated with the levels of dietary intakes of energy, carbohydrate, total lipids, cholesterol, vitamin A, vitamin B$_1$, niacin, vitamin C, calcium, phosphorous, sodium and potassium at p<0.01, and with dietary intakes of iron and animal lipids at p<0.05, respectively. Plasma taurine concentration of subjects were 135$\pm$5.9$\mu$mol/L, which is considered to be within a normal range for healthy subjects. The subjects excreted 1158$\pm$72.7nmol/ of tarine mg creatinine in their urine, which is approximated as 150-170mg of taurine/24hr urine based on the assumption that 18mg creatinine/kg/day is excreted in the urine of healthy adults, and this would be about 80% of the daily taurine intake observed in the same subjects. Dietary taurine intake level was positively correlated with plasma taurine concentration, as well as with urinary taurine excretion corrected by creatinine excretion at p<0.05. The present study was the first report of taurine intake, and plasma concentration and urinary excretion of taurine in a Korean population so far, and these results would serve as an index for the future study evaluating taurine status in a diverse population within and outside Korea. (Korean J Nutrition 34(4) : 440~448, 2001)

• Korean Chemical Engineering Research
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• v.51 no.1
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• pp.136-143
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• 2013

In this study, both transient behaviors of a biofilter system with improved design and a conventional biofilter were observed to perform the treatment of waste air containing malodor and volatile organic compound (VOC). Their behaviors of removal efficiency and treated concentration of malodor and VOC were compared each other. During 1st~7th stages of improved biofilter system operation it was observed that the order of treated ethanol concentration at each sampling port was switched due to the difference of microbe-population-distribution in spite of the difference of biofilter effective height. However, at 8th stage of its operation, the order of treated ethanol concentration at each sampling port was consistent to the order of biofilter effective height at each sampling port. The same was applied to the case of hydrogen sulfide, even though the difference of switched treated-hydrogen sulfide-concentrations was less than that of switched treated-ethanol-concentrations. The ethanol-removal efficiency of the biofilter system with improved design was ca. 96%, which was greater by 2% than that of the conventional biofilter. The transient behavior of treated hydrogen sulfide concentration of both biofilters were similar to each other. However, the concentration of hydrogen sulfide treated by the biofilter system with improved design was observed lower than that by the conventional biofilter. The hydrogen sulfide-removal efficiency of the biofilter system with improved design was higher by ca. 2% than that of the conventional biofilter. Therefore, the hydrogen sulfide-removal efficiency of the biofilter system with improved design was observed to be enhanced by the same as its ethanol-removal efficiency.

• Korean Journal of Environmental Biology
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• v.34 no.3
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• pp.193-200
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• 2016

Toxicity assessment of heavy metals (As, Cr and Pb) has been investigated by using the rate of survival and population growth(r) of marine rotifer, Brachionus plicatilis. The survival rate was determined after 24 hours of exposure to As, Cr and Pb. As and Cr reduced survival rate in dose-dependent manner and a significant reduction were occurred at concentration of greater than 30 and $150mg\;L^{-1}$, but Pb had no effect on survival rate. The r was determined after 72 hours of exposure to As, Cr and Pb. As, Cr and Pb reduced r in dose-dependent manner and a significant reduction were occurred at concentration of greater than 5, 25 and $50mg\;L^{-1}$. The toxicity of heavy metals were ranked As>Cr>Pb, with $EC_{50}$ values of 12.98, 82.34 and $110.14mg\;L^{-1}$, respectively. The no-observed-effect-concentration (NOEC) of r in As, Cr and Pb exposure were 1, 12.5 and $50mg\;L^{-1}$, respectively. The lowest-observed-effect-concentration (LOEC) of r in As, Cr and Pb exposure were 5, 25, and $50mg\;L^{-1}$, respectively. From the results, the concentration of As, Cr and Pb (greater than 5, 25 and $50mg\;L^{-1}$, respectively) have toxic effect on the r of B. plicatilis in natural ecosystems. These results (including NOEC and $EC_{50}$) might be useful for the mixing toxicity assessment and toxic guide line of heavy metals in marine ecosystems.