• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.16 no.4
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• pp.334-345
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• 2006

The objectives of this study were to analyze and compare 24 hrs personal exposure levels of MF at microenvironments such as home, school, educational institute, internet pc game room, transportation, and other places according to time activity patterns using various metrics for children attending the primary schools located near and away from the power lines, and to characterize the major microenvironments and impact factors attributed personal exposure level. The study was carried out for 44 children attending a primary school away from the lines(school A) and 125 children attending a school away from 154 kV power lines(school B), all who aged 12 years and were 6 grade, from July 2003 to December 2003. All participants filled in a questionnaire about characteristics, residence, use of electrical appliances and others. Children wore a small satchel in which EMDEX II and Lite (Enertech, Co. Ltd) and a diary of activity list for period of registration in 20 minutes blocks. All statistical calculations were made with the SAS System, Releas 6.12. The summary of results was presented below. First, about the characteristics of subjects, there no differences between two groups. The subject almost spent about 56 % of their time at home and about 20~25 % of their time at school. Fifty percent of children spent 2 hours at private educational institutes. Second, the personal exposure measurements of children in school B was statistically higher than those of children in school A by various metrics such as arithmetic mean, geometric mean, percentile(5, 25, 50, 75, 95), maximum, rate of change metric, constant field metric. The arithmetic and geometric mean magnetic fields during the time the children were at school B were 0.98 and $0.86{\mu}T$ and were about 23 times higher than those of children were at school A. In conclusion, the significant major determinants of personal exposure level is the distance from the power line to microenvironments.

• Journal of Environmental Health Sciences
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• v.47 no.2
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• pp.155-165
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• 2021

Objectives: Acute exposure to high concentrations of chemicals can occur when a chemical accident takes place. As such exposure can cause ongoing environmental pollution, such as in the soil and groundwater, there is a need for a tool that can assess health effects in the long term. The purpose of this study was assessing the health risks of residents living near a chemical accident site due to long-term exposure while considering the temporal concentration changes of the toxic chemicals leaked during the accident until their extinction in the environment using a multimedia environmental dynamics model. Methods: A health risk assessment was conducted on three cases of formaldehyde chemical accidents. In this study, health risk assessment was performed using a multimedia environmental dynamics model that considers the behavior of the atmosphere, soil, and water. In addition, the extinction period of formaldehyde in the environment was regarded as extinction in the environment when the concentration in the air and soil fell below the background concentration prior to the accident. The subjects of health risk assessment were classified into four groups according to age: 0-9 years old, 10-18 years old, 19-64 years old, and over 65 years old. Carcinogenic risk assessment by respiratory exposure and non-carcinogenic risk assessment by soil intake were conducted as well. Results: In the assessment of carcinogenic risk due to respiratory exposure, the excess carcinogenic risk did not exceed 1.0×10-6 in all three chemical accidents, so there was no health effect due to the formaldehyde chemical accident. As a result of the evaluation of non-carcinogenic risk due to soil intake, none of the three chemical accidents had a risk index of 1, so there was no health effect. For all three chemical accidents, the excess cancer risk and hazard index were the highest in the age group 0-9. Next, 10-18 years old, 65 years old or older, and 19-64 years old showed the highest risk. Conclusion: This study considers environmental changes after a chemical accident occurs and until the substance disappears from the environment. It also conducts a health risk assessment by reflecting the characteristics of the long-term persistence and concentration change over time. It is thought that it is of significance as a health risk assessment study reflecting the exposure characteristics of the accident substance for an actual chemical accident.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2006.10a
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• pp.132-137
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• 2006

With the help of the development of digital-multimedia in the middle of 1990's, FDP(Flat Panel Display) had attracted considerable attention. Collimation proximity exposure system that transfers the pattern on wafer or glass exactly using mask and light with appropriate wavelength is core process in semiconductor and liquid display element. The performances of resolution required in precision exposure system are evaluated by resolving power, depth of focus and storage area. Most of development has targeted on these three factors. The optical design including lamp house has played an important role on the performance of exposure process. In this study, we evaluate the cooling system, concerning on exposure device with mercury lamp among the kernel equipment for the production of LCD, to prevent the instability of lighting due to long term accumulation of excessive heating inside the lamp house. Numerical analysis is conducted on full-scale model. The characteristics of three-dimensional flow, pressure and temperature distribution on exposure system are graphically depicted to estimate the whole cooling system for lamp house and to establish the design criteria.

• Journal of Environmental Health Sciences
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• v.17 no.1
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• pp.79-88
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• 1991

These studies were carried out to find out some characteristic responses of biological samples under the exposure of trace metals. In animal experiment, six rats per week were killed for 6 weeks under Cd exposures and the concentrations of Cd, Cu and Zn in their organs and blood were determined by flame atomic absorption spectrophotometry.The results were summarized as follows: In animal experiments, the concentrations of Cd in the liver and kidney of Cd exposure groups were increased, however, the values of hematocrit and hemoglobin in blood were decreased remarkably. The body weight of the Cd exposure groups showed lower trend than that of control group. The concentrations of Cd in heart, lung and testes were increased slowly during the first 2 weeks. The concentrations of Cd in their organs decreased while the rapid increase of the concentration of Cd in the liver and kidney was observed. While rapid increase of the concentra~ion of Cd in the liver and kidney was observed, the concentrations of Cd in the organs were decreased afterward and increased again while the low increase of the concentration of Cd in the liver and kidney was observed. The concentrations Cu and Zn were increased remarkably in all the organs for first 2 and 3 weeks. In the exposure groups of Cd+Cu and Cd+Zn, the liver and kidney didn't show lower concentration of Cd than that of Cd group.

• Journal of Korean Society for Atmospheric Environment
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• v.25 no.4
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• pp.339-346
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• 2009

The objectives of this study were to introduce spatial interpolation methods which have been applied in recent papers, to apply three methods (nearest monitor, inverse distance weighting, kriging) to domestic data (Ulsan cohort) as an example of estimating the personal exposure levels. We predicted the personal exposure estimates of 2,102 participants in Ulsan cohort using spatial interpolation methods based on information of their residential address. We found that there was a similar tendency among the estimates of each method. The correlation coefficients between predictions from pairs of interpolation methods (except for the correlation coefficient between nearest montitor and kriging of CO and $SO_2$) were generally high (r=0.84 to 0.96). Even if there are some limitations such as location and density of monitoring station, spatial interpolation methods can reflect spatial aspects of air pollutant and spatial heterogeneity in individual level so that they provide more accurate estimates than monitor data alone. But they may still result in misclassification of exposure. To minimize misclassification for better estimates, we need to consider individual characteristics such as daily activity pattern.

• Journal of environmental and Sanitary engineering
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• v.16 no.1
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• pp.1-8
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• 2001

Since most people spend over 80% of their time indoor, indoor air quality tends to be the dominant contributor to personal exposure. In this study, indoor and outdoor $NO_2$concentrations were measured and compared with simultaneously personal exposures of 27 house-wives and female workers of kindergarten. Time activity pattern and house characteristics were used to determine the effects of these factors on personal exposure. Since house-wives student spent most their times in indoor with mean of 89.8%, their $NO_2$ exposure was associated with indoor $NO_2$ level(r= 0.92) rather than outdoor $NO_2$ level(r= 0.87). female workers were also associated with indoor $NO_2$ level(r= 0.70) though sample number were small. Using time-weighted average model, $NO_2$ exposures of house-wives were estimated by $NO_2$ measurements in indoor home and outdoor home levels. Estimated $NO_2$ personal exposures were significantly correlated with measured $NO_2$ personal exposures (r= 0.90). These results might mean that air pollutants exposure of old and feeble persons, and infants could be estimated by measuring concentrations of indoor home.

• International Journal of Human Ecology
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• v.12 no.2
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• pp.1-12
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• 2011

Many pharmaceutical products are available through prescription (Rx) only status. As a result, access to physicians and insurance coverage play a key role in the use of these products, and therefore may affect the population to whom advertising is targeted at. The movement of pharmaceutical products from prescription (Rx) to Over-the-Counter (OTC), or Rx-to-OTC switch changes the cost of acquiring the drug and therefore may change the incentives manufacturers have at targeting particular population segments. This study examines whether Rx-to-OTC switch changes the frequency and the distribution of who is exposed to pharmaceutical advertising. Using an archive of pharmaceutical advertisements and National Consumer Survey, this study examines how individuals with particular demographic characteristics are exposed to pharmaceutical advertisements before and after drugs are moved from Rx to OTC. The results provide evidence that individual's advertising exposure increases after Rx-to-OTC switch. Moreover, the increase in advertising exposure is greater for the low socioeconomic status (SES) consumers which implies they may get more information about the disease, treatment and product after the Rx-to-OTC switch through advertising. If low SES consumers have more exposure to the advertising after products switched to OTC, then FDA policies regulating this switch should recognize the potential role of advertising providing access to health-related information.

• Journal of Environmental Health Sciences
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• v.34 no.3
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• pp.183-187
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• 2008

Indoor air quality can be affected by indoor sources, ventilation, decay, and outdoor levels. Various indoor and out-door combustion sources produce nitrogen dioxide ($NO_2$), which is a by-product of high temperature fossil fuel combustion. Especially, the presence of gas ranges and smoking have been identified as major factors contributing to indoor $NO_2$ exposures. In this study, we compared an industrial complex area with a country area by assessing the personal exposure to $NO_2$with measurements of indoor and outdoor $NO_2$ levels in residences and by house characteristics and questionnaire. Personal exposure concentrations were significantly correlated with indoor $NO_2$ concentrations of residences in both the industrial complex area and the country area with correlation coefficients of 0.561 and 0.664, respectively, compared to outdoors. Multiple regression analysis, indicated that indoor $NO_2$ levels in residences were only affected by outdoor levels (p = 0.000) in spite of higher indoor sources such as smoking. Therefore, it is suggested that outdoor air quality as well as indoor air quality should be considered in the reduction of the personal exposure to air pollutants.

• Journal of the Korean institute of surface engineering
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• v.54 no.2
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• pp.62-70
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• 2021

Al2024 aluminum alloy specimens were exposed to atmospheric conditions for maximum 24 months and analyzed by electron microscopes to characterize their corrosion behavior and oxide film characteristics. As the exposure time increased from 12 months to 24 months, the number of pitting sites per 1 mm² increased from ~100 to ~200. The uniform oxidation (or non-pitting) region of the 12-month exposure specimen showed 30~120 nm thick oxide layer, whereas the 24-month exposure specimen showed 170~200 nm thick oxide with the local oxygen penetration region up to 1 ㎛ deep. There was no local corrosion area observed in the 12-month exposure specimen except pitting. However, in the 24-month exposure specimen, local oxygen penetration region was observed beneath the uniform oxide layer and near the pitting cavity. Al2024 showed two times thicker uniform oxide layer but much shallower local oxygen penetration region than Al1050, which appears to be related to low Si concentration. Further research is needed on the effects of Mg segregation near the tip of the oxygen penetration region.

• Journal of Sensor Science and Technology
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• v.32 no.6
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• pp.455-461
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• 2023

We investigated the electrical characteristics of ZnO nanoparticles (NPs) with air exposure that is a widely used electron transport layer for quantum dot light-emitting diodes (QLEDs). Upon air exposure, we observed changes in the density of states (DOS) of the trap levels of ZnO NPs. In particular, with air exposure, the concentration of deep trap energy levels in ZnO NPs decreased and electron mobility significantly improved. Consequently, the air-exposed ZnO reduced leakage current by approximately one order of magnitude and enhanced the external quantum efficiency at the low driving voltage region of the QLED. In addition, based on the excellent conductivity properties, high-brightness QLEDs could be achieved.