• Environmental Mutagens and Carcinogens
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• v.22 no.3
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• pp.187-198
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• 2002

Chlorpyrifos is an organophosphate insecticide and one of the most commonly and widely used insecticide. However, a little known about the dermal risk of chlorpyrifos on human being. Therefore, this study was conducted for the dermal risk assessment after exposure to chlorpyrifos in Korean farmers. First, skin irritation by chlorpyrifos (10 mg/$\textrm{cm}^2$, 50 mg/$\textrm{cm}^2$, 100 mg/$\textrm{cm}^2$, 250 mg/$\textrm{cm}^2$ in acetone) was determined in rabbits for 5 days considering the usage of chlorpyrifos short term highly exposure. The index of skin irritation by chlorpyrifos was increased in each dose and length of exposure dependent manners. Next, using benchmark dose (BMD$_{5}$) approach, the dose-response relationship was assessed to calculate the reference dose (RfD). The value of RfD was 2.84 $\mu\textrm{g}$/kg/day from 142.16 $\mu\textrm{g}$/kg/day BMD5 value divided uncertainty factor 50. Finally, we assessed human dermal risk of chlorpyrifos with exposure level and RfD. Skin absorbed levels were assumed with several exposure scenarios encounting the circumstances of exposure that application method, protection equipment and cloth, exposure time and exposure frequency during chlorpyrifos spraying. By the comparison of skin absorbed dose with the reference dose, it was identified that risk values (risk index) to skin chlorpyrifos exposure were 0.958 from the point of above results and it was recommended that the occurrence of hazard effect (skin irritation toxicity) of chlorpyrifos would not be expected. Risk index was smaller than 1 in the case of spraying vehicle mounted application, 1hour exposure time and wearing protective cloth exposure. Whereas, risk index was above 1 in the case of hand-held application, 2hour exposure time and wearing common cloth. Comparing two kinds of application method, total risk index of the hand held application (1.67) was higher than vehicle mounted (0.27). Therefore, chlorpyrifos skin exposure was mainly affected by application equipment and applied form. The results of risk assessment on the human dermal toxicity of chlorpyrifos should be required to control in keeping safety rules, skin surface area available for contact, spraying time ,and spraying frequency.y.

• Journal of Environmental Health Sciences
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• v.27 no.1
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• pp.20-26
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• 2001

personal nitrogen dioxide(NO$_2$) exposures for 31 professional drivers were measured using passive sampler and time activity diary in Asan and Chunan area, and were estimated using time-weighted average model. Mean concentrations of driver’s indoor and outdoor were 24.7$\pm$10.7 ppb and 23.3$\pm$8.3 ppb, respectively with indoor/outdoor of 1.1. Mean personal NO$_2$ exposure was 30.3$\pm$9.7 ppb. Personal NO$_2$ exposures were strongly correlated with indoor car NO$_2$ levels ($R^2$=0.80) rather than residential indoor NO$_2$ level ($R^2$=0.55). and outdoor NO$_2$ level ($R^2$=0.50). The driver’s NO$_2$ exposure using LP-gas with 24.4$\pm$8.0 ppb were statistically different from those using diesel with 36.3$\pm$14.1 ppb(p<0.01). The effect of driver’s smoking for personal NO$_2$ exposure was not found. It was considered that the main NO$_2$in driver is transportation. Since drivers mostly spent their times in indoor and inside car, time-weighted average model could be used to estimated personal NO$_2$ exposure using time activity diary, Though we did not measure all microenvironments, the estimated personal NO$_2$ exposures with 26.9$\pm$10.2 ppb were statistically correlated with measured personal NO $_2$ exposures30.3$\pm$9.7 ppb ($R^2$=0.89). The mean and standard deviation of personal NO$_2$ exposure using Mote-Carlo simulation were 26.6$\pm$7.2 ppb.

• Research in Community and Public Health Nursing
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• v.17 no.3
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• pp.376-386
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• 2006

Purpose: This study was conducted to analyze the exposure of female high school students to Internet pornography and its related factors. Methods: A total of 392 female high school students were selected through convenience sampling. Data were collected using self-reported questionnaires from June 27 to July 8, 2005. Results: 1. As for exposure to Internet pornography, 61.0% of the respondents had been exposed to Internet pornography and 29.7% had their first exposure to Internet pornography when they were in the 3rd grade of middle school. In addition, 87.9% of the respondents spent less than 30 minutes each time to view Internet pornography. In 41.8% of the respondents, the reason for seeing Internet pornography was curiosity about sexuality. 2. Both the level of sexual knowledge (t=3.174, p=.002) and attitude (t=2.567, p=.011) were significantly different between the exposure group and the non-exposure group. 3. Grade, daily mean time to use computer, and sexual knowledge had statistically significant effects on exposure to Internet pornography. Conclusion: It is necessary to make repeated study to find other variables that affect students' exposure to Internet pornography and to develop education programs to enhance students' coping ability against Internet pornography. Also, parents' concern over youth is necessary to prevent them from being exposed to Internet pornography.

• Nuclear Engineering and Technology
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• v.50 no.7
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• pp.1088-1098
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• 2018

Kori unit #1, which is the first commercial nuclear power plant in Korea, was permanently shutdown in June 2017, and it is about to be decommissioned. Currently in Korea, researches on the decommissioning technology are actively conducted, but there are few researches on workers internal exposure to radioactive aerosol that is generated in the process of decommissioning nuclear power plants. As a result, the over-exposure of decommissioning workers is feared, and the optimal working time needs to be revised in consideration of radioactive aerosol. This study investigated the annual exposure limits of various countries, which can be used as an indicator in evaluating workers' internal exposure to radioactive aerosol during pipe cutting in the process of decommissioning nuclear power plants, and the growth and dynamics of aerosol. Also, to evaluate it, the authors compared/analyzed the cases of aerosol generated when activated pipes are cut in the process of nuclear power plants and the codes for evaluating internal exposure. The evaluation codes and analyzed data conform to ALARA, and they are believed to be used as an important indicator in deriving an optimal working time that does not excess the annual exposure limit.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.25 no.1
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• pp.51-70
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• 1995

The purpose of this investigation was to compare the direct digital radiographic system with film-based digital imaging system using Ektaspeed and Ektaspeed Plus film with respect to image characteristics and detectability and evaluate the sensor noise with the use of subtraction method. Direct digital radiographic system which used was Sens-A-Ray system(Regam Medical Systems, Sundsvall, Sweden) and film-based digital imaging system was composed of Macintosh II ci computer, high resolution Sony XC-77 CCD camera and intraoral x-ray film(Kodak Ektaspeed film, Kodak Ektaspeed Plus film). Images were taken by using CCD sensor of Sens-A-Ray system, Ektaspeed film and Ektaspeed Plus film with variable exposure time(0.06s, 0.1s, 0.16s, 0.2s, 0.3s, 0.4s, 0.5s, 0.6s, O.8s, LOs), 5 times at each exposure time. And then ektaspeed films and ektaspeed plus films were digitized using CCD camera. Image groups were divided into 3 groups; Sens-A-Ray group(direct digital radiographic system), Ektaspeed group and Ektaspeed Plus group (film-based digital imaging system) They were assessed by the following three aspects; image density, image contrast and detectability and sensor noise of Sens-A-Ray system was also evaluated. The results were as follow : 1. S group showed higher density than E , EP group except at the low exposure time(p<0.01). 2. S group showed higher contrast than E,EP group except at the high exposure time(p<0.01). 3. All groups showed good detectability at the each proper exposure time. Lowest exposure time which shows maximum detectability in S,EP group(0.5s) was lower than that in E group(0.6s). 4. Sensor noise of Sens-A-Ray system generally increased according to exposure time. On the basis of the above results, it was considered that Sens-A-Ray system could show higher speed, higher contrast than Ektaspeed, Ektaspeed Plus film except at too high and low exposure time and the same detectability as the conventional intraoral film.

• Safety and Health at Work
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• v.9 no.3
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• pp.290-295
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• 2018

Background: There is little information on the dose-response relationship between exposure to occupational carcinogenic agents and mesothelioma. This study aimed to investigate this association as well as the existence of agents other than asbestos that might cause mesothelioma. Methods: The Swedish component of the Nordic Occupational Cancer (NOCCA) study consists of 6.78 million individuals with detailed information on occupation. Mesothelioma diagnoses recorded in 1961-2009 were identified through linkage to the Swedish Cancer Registry. We determined cumulative exposure, time of first exposure, and maximum exposure intensity by linking data on occupation to the Swedish NOCCA job-exposure matrix, which includes 29 carcinogenic agents and corresponding exposure for 283 occupations. To assess the risk of mesothelioma, we used conditional logistic regression models to estimate hazard ratios and 95% confidence intervals. Results: 2,757 mesothelioma cases were identified in males, including 1,416 who were exposed to asbestos. Univariate analyses showed not only a significant excess risk for maximum exposure intensity, with a hazard ratio of 4.81 at exposure levels 1.25-2.0 fb/ml but also a clear dose-response effect for cumulative exposure with a 30-, 40-, and 50-year latency time. No convincing excess risk was revealed for any of the other carcinogenic agents included in the Swedish NOCCA job-exposure matrix. Conclusion: When considering asbestos exposure, past exposure, even for short periods, might be enough to cause mesothelioma of the pleura later in life.

• Toxicological Research
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• v.26 no.2
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• pp.131-136
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• 2010

The time-dependent changes in cadmium (Cd) concentration were studied in Female Sprague-Dawley (SD) rats during and after Cd exposure via drinking water (10 and 50 ppm) for 30 days. The cadmium concentration in muscle, liver, kidney, blood plasma, and urine, and the metallothionein concentration in blood plasma were determined every 10 days during exposure and every 7 days after exposure for 3 weeks. The muscle Cd concentration did not change during, and neither after, exposure. The liver Cd concentration increased from 1.4 to 3.3 (at 10 ppm) and from 6.1 to 10.1 folds (at 50 ppm) during exposure and remained higher than those of controls in both groups even during post-exposure period. The kidney Cd concentrations were 2.3 to 5.1 (at 10 ppm) and 4.9-14.0 folds (at 50 ppm) higher than those of controls during exposure and also remained elevated during the post-exposure period. Plasma Cd concentrations were not significantly different from those of controls in both groups. Urine Cd concentrations were more than 2 folds (at 10 ppm) and 6.5 to 12.6 folds (at 50 ppm) higher than those of controls but rapidly decreased over the 7 days of withdrawal. Blood plasma metallothionein concentrations were more than 2.4 folds (at 10 ppm) and 3.1 to 7.4 folds (at 50 ppm), and they remained elevated till 7 days (10 ppm) and 14 days (at 50 ppm) after exposure. Our data support that Cd in urine could be a useful biomarker during Cd exposure period and metallothionein in blood plasma could be as a supportive biological marker for during and post Cd exposure.

• Journal of the Korean Vacuum Society
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• v.8 no.2
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• pp.102-110
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• 1999

The LIGA X-ray exposure step was modelled into three inequalities, by assuming that the X-ray energy attenuated within a resist is deposited only in the localized range of the resist. From these inequalities, equations for the minimum and maximum exposure times required for a good quality microstructure were obtained. Also, an equation for the thickness of an X-ray mask absorber was obtained from the exposure requirement of threshold dose deposition. The calculation method of the synchrotron radiation power from a synchrotron radiation source was introduced and applied to an X-ray exposure step. A power from a synchrotron radiation source was introduced and applied to an X-ray exposure step/ A power function of photon energy, approximating the attenuation length of the representative LIGA resist, PMMA, and the mean photon energy of the XZ-rays incident upon an X-ray mask absorber were applied to the above mentioned equations. Consequently, the tendencies of the minimum and maximum exposure and with respect to mean photon energy and thick ness of PMMA was obtained. Additionally, the tendencies of the necessary thickness of PMMA and photon energy of the X-ray mask absorber with respect to thickness of PMMA and photon energy of the X-rays incident upon an X-ray mask absorber were examined. The minimum exposure time increases monotonically with increasing mean photon energy for the same total power density and is not a function of the thickness of resist. The minimum exposure time increases with increasing mean photon energy for the same total power density in the case of the general LIGA process, where the thickness of PMMA is thinner than the attenuation length of PMMA. Additionally, the minimum exposure time increases monotonically with increasing thickness of PMMA. The maximally exposable thickness of resist is proportional to the attenuation length of the resist at the mean photon energy with its proportional constant of ln $(Dd_m/D_{dv})$. The necessary thickness of a gold X-ray mask absorber due to absorption edges of gold, increases smoothly with increasing PMMA thickness ratio, and is independent of the total power density itself. The simplicity of the derived equations has made clearly understandable the X-ray exposure phenomenon and the correlation among the exposure times, the attenuation coefficient and the thickness of an X-ray mask absorber, the attenuation coefficient and the thickness of the resist, and the synchrotron radiation power density.

• Korean Journal of Optics and Photonics
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• v.9 no.5
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• pp.315-320
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• 1998

The characteristics and structures of photopolymer are analyzed in this paper, which recently have various applications in optical information processing and optical memory, Especially, Du Pont's photopolymer OmniDex 706 reflection film is used in many experiments of different exposures and incident angles, and analyzed by the diffraction pattern generated by glass plate's reflection beam. With the dark reaction of the monomer in photopolymerization, dynamic parameters are considered due to the variation of exposure time and diffusion time delay after exposure. The performance of diffraction efficiency is improved by 10%, when an exposure time is 6.25 sec, and a diffusion time delay is 2 minute.

• Journal of the Korean Institute of Gas
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• v.21 no.5
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• pp.77-82
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• 2017

Thus, chemicals are managed under 9 related central government department and 16 relevant laws with program such as Process Safety Management and Offsite Consequence Analysis in korea. Guidelines for set the endpoint concentration for chemcals based on the ERPG-2 (Emergency Response Planning Guidelines-2) and AEGL-2 (Acute Exposure Guidelines Level-2). but ERPG and AEGL do not describe exposure for less than 10 minutes. because of this, each guidelines define criteria differently for short time less than 10 minutes exposure. This indefinite exposure criteria would give rise to a confusion in the chemical plants, and potentially lead to a critical decision making error when accidents happen. In an effort to apply guidelines with evenly-distributed initial time frame, AEGL concentrations within 10 minute exposure time were evaluated by examining statistical regression curves. The results were in good agreement with those from the Probit Function based on each AEGL grade to explain 3 different threshold levels of exposure effects. Resultant re-enforced guidelines for endpoint chemical concentrations are, therefore, to provide powerful tool to assess and manage the risk associated with any potential chemical accidents at an early stage.