• Korean Chemical Engineering Research
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• v.56 no.4
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• pp.474-478
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• 2018

For process safety, fire and explosion characteristics of combustible materials handled at industrial fields must be available. The combustion properties for the prevention of the accidents in the work place are flash point, fire point, explosion limit, and autoignition temperature (AIT) etc.. However, the combustion properties suggested in the Material Safety Data Sheet (MSDS) are presented differently according to the literatures. The accurate combustion properties are necessary to safely treatment, transportation and handling of flammable substances. In the chemical industries, n-ethylaniline which is widely used as a raw material of intermediate products and rubber chemicals was selected. For safe handling of n-ethyl aniline, the flash point, the fire point and the AIT were measured. The lower explosion limit (LEL)of n-ethylaniline was calculated using the lower flash point obtained in the experiment. The flash points of n- ethylaniline by using the Setaflash and Pensky-Martens closed-cup testers measured $77^{\circ}C$ and $82^{\circ}C$, respectively. The flash points of n-ethylaniline using the Tag and Cleveland open cup testers are measured $85^{\circ}C$ and $92^{\circ}C$, respectively. The AIT of the measured n-ethyl aniline by the ASTM E659 apparatus was measured at $396^{\circ}C$. The LEL of n-ethylaniline measured by Setaflash closed-cup tester at $77^{\circ}C$ was calculated to be 1.02 vol%. In this study, it was possible to predict the LEL by using the lower flash point of n-ethylaniline measured by closed-cup tester. The relationship between the ignition temperature and the ignition delay time of the n-ethylaniline proposed in this study makes it possible to predict the ignition delay time at different ignition temperatures.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.17 no.1
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• pp.21-30
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• 2007

To establish the Fourier-transform infra-red spectrophotometry (FTIR) direct-on-filter(DOF) technique as a useful analytical method for quartz in respirable dust samples, influence of the interference should be corrected. This study was designed to compare three methods of correction for cristobalite when quantifying the content of quartz, including the least square, the optimum choice and the spectral subtraction methods. Respirable dust, created in a dust chamber containing the standard material of quartz, cristobalite was collected using a cyclone equipped with a 25 mm, $0.8{\mu}m$ pore size DM filter as a collection medium. The quartz weights overestimated about 100% when mixed of cristobalite by measure using 799 cm-1 absorption peak of quartz. The quartz weights appeared over estimated by optimum choice, spectral subtraction and least square method in mixtures of 33% cristobalite were 90.3%, 60.1% and about 4.3%, respectively. The least square method have been adopted to correction methods of cristobalite and satisfactory results have been obtained. The results of this study suggest that, when correcting for effect of cristobalite on quantitative analysis of quartz in respirable dust by FTIR direct-on-filter method, the least square method produce the most unbiased results compared with those of other correction methods.

• The Journal of the Korea Contents Association
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• v.14 no.8
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• pp.266-276
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• 2014

The present study aims to determine the effect of the prevention exercise program of musculoskeletal disorders developed for apple and pear farmers. To achieve this goal, 25 farmers who have subjective symptoms in the musculoskeletal system (Criteria 1 in the National Institute for Occupational Safety and Health) have conducted the prevention exercise program for 12 weeks from April 7, 2011 to July 1, 2011. As a result, the prevention exercise program of the musculoskeletal disorders for farmers in the fruit growing industry have improved physical capability of them (upper extremity endurance, lower extremity endurance, balance and agility) as well as a quality of life effectively. In addition, a quality of life showed a significant correlation with Oswestry Disability Index, and Psychosocial Well-being Index. For the future study, various studies are expected to develop and apply exercise programs in consideration of the characteristics of farming work.

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.80-88
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• 2023

Ensuring safety in the designing of manufacturing and handling facilities for low-density polyethylene (LDPE) is difficult because there are no standards for the dust explosion characteristics of LDPE. In this study, a dust explosion test was performed on two dust samples collected from a bag filter (LDPE 1) during the LDPE manufacturing process and sedimentary dust (LDPE 2) leaked outside a facility such as a silo, and the LDPE 2 explosion test results were summarized. Particle size analysis showed that the volume-based particle diameter (median) was 95.04 ㎛ and the number density was 0-1 ㎛. The maximum explosion pressure (P_max) was 6.6 bar, and the maximum rate of explosion pressure rise was 366 [bar/s] at 1500 g/m³. Accordingly, the dust explosion index (K_st) was 99.4 bar·m/s, which was confirmed as ST-1 grade. Moreover, the minimum ignition energy and minimum ignition temperature was 10 mJ and 450 ℃, respectively. Currently, manufacturing and handling design is based on the characteristic values of high-density polyethylene (HDPE). However, as the test results show that LDPE 2 dust has a higher risk than HDPE (particle diameter 61.6 ㎛), caution is required when using the HDPE design criteria in the LDPE manufacturing process.

• Journal of Environmental Science International
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• v.17 no.9
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• pp.1005-1013
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• 2008

In this study, in order to analyze the air quality of the indoor environments of schools, we measured the indoor, outdoor and personal exposure concentration level of $PM_{10}$ for 40 classrooms(20 old, 20 new) in chungnam area from June 22 to July 19 and from November 21 to December 30, 2003. 1. Old classrooms contained more dust than new classrooms; the average of respirable dust is $43.27\;{\mu}g/m^3$ for new classrooms while $53.38\;{\mu}g/m^3$ for old one. The exposure concentration level of respirable dust in new classrooms were in summer higher outdoors than indoors. The values were indoors $46.71\;{\mu}g/m^3$, outdoors $50.46\;{\mu}g/m^3$, and personal $41.62\;{\mu}g/m^3$. Meanwhile in winter indoors had a higher concentration level than outdoors, the values being indoors $39.11\;{\mu}g/m^3$, outdoors $34.86\;{\mu}g/m^3$, and personal $49.01\;{\mu}g/m^3$. 2. Cr concentration level within dust was slightly higher in summer indoors ($101.50{\pm}32.10\;ng/m^3$) and outdoors ($100.89{\pm}35.18\;ng/m^3$) than winter indoors ($85.80{\pm}48.95\;ng/m^3$) and outdoors ($74.43{\pm}38.93\;ng/m^3$), but in personal concentration level, winter was higher. The results of this research show insufficient understanding of health risks from indoor air pollution, and shows possible health problems to students from school indoor air pollution. As such, a logical and systematic education program for students about the importance of indoor air quality should be carried out. Also the results of $PM_{10}$ concentration level measurements emphasize the need for regular measurements of indoor / outdoor and personal concentration level. New classrooms in particular needs to be used after measuring pollutants and safety, and requires installation of a ventilation device in all classrooms to improve air quality.

• Journal of Preventive Medicine and Public Health
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• v.57 no.2
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• pp.185-196
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• 2024

Objectives: Excess mortality associated with long-term exposure to fine particulate matter (PM_2.5) has been documented. However, research on the disease burden following short-term exposure is scarce. We investigated the cause-specific mortality burden of short-term exposure to PM_2.5 by considering the potential non-linear concentration-response relationship in Korea. Methods: Daily cause-specific mortality rates and PM_2.5 exposure levels from 2010 to 2019 were collected for 8 Korean cities and 9 provinces. A generalized additive mixed model was employed to estimate the non-linear relationship between PM_2.5 exposure and cause-specific mortality levels. We assumed no detrimental health effects of PM_2.5 concentrations below 15 ㎍/m³. Overall deaths attributable to short-term PM_2.5 exposure were estimated by summing the daily numbers of excess deaths associated with ambient PM_2.5 exposure. Results: Of the 2 749 704 recorded deaths, 2 453 686 (89.2%) were non-accidental, 591 267 (21.5%) were cardiovascular, and 141 066 (5.1%) were respiratory in nature. A non-linear relationship was observed between all-cause mortality and exposure to PM_2.5 at lag0, whereas linear associations were evident for cause-specific mortalities. Overall, 10 814 all-cause, 7855 non-accidental, 1642 cardiovascular, and 708 respiratory deaths were attributed to short-term exposure to PM_2.5. The estimated number of all-cause excess deaths due to short-term PM_2.5 exposure in 2019 was 1039 (95% confidence interval, 604 to 1472). Conclusions: Our findings indicate an association between short-term PM_2.5 exposure and various mortality rates (all-cause, non-accidental, cardiovascular, and respiratory) in Korea over the period from 2010 to 2019. Consequently, action plans should be developed to reduce deaths attributable to short-term exposure to PM_2.5.

• Environmental Analysis Health and Toxicology
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• v.15 no.1_2
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• pp.31-37
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• 2000

Acetanilide may be released into the environment through air and wastewater from its production and use sites and exposed to human. Acetanilide is known to produce an analgesic effect and may pose adverse effects on human health by overly exposure. According to the EUSES system, acetanilide showed a high MOS (Margin of safety) value exceeding 6$\times$10$^4$ on a regional exposure, which is safe enough for public health. Whereas the lowest MOS value in dermal exposure was estimated as 3$\times$10$^{-4}$ on a local basis (workplace), the risk could be partly counteracted by taking preventive measures such as using mask and globes and good ventilation in the work places. Acetanilide may pose a potential risk for workers by dust inhalation. For the sake of health protection in the work places, additional data should be accumulated with respect to repeated dose toxicity, reproduction toxicity and developmental toxicity, etc. It is, therefore, recommended that acetanilide should be a candidate for further work to supplement the lacking data until it is proved to be safe in the occupational health aspects.

• Journal of Preventive Medicine and Public Health
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• v.32 no.1
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• pp.30-39
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• 1999

Objectives. This study was carried out to evaluate hearing impairment judgement and to investigate the differences in various diagnostic criteria for noise-induced hearing loss (NIHL) among workers who required for close observation (C). Methods. Out of 731,029 workers who had taken the specific periodic health examination in 1994, we used the audiometric data on 37,999 workers (C) eliminating the employees who had previous otologic problems. Many investigators have being using different criteria for the evaluation of hearing impairment. In this study, we used the criteria of early (1989-1994), current, compensation for NIHL in Korea, 2-, 3-, 4-divided classification and hearing loss at 4,000 Hz and compared the evaluation results. Results. The prevalences of C and workers who had occupational disease $(D_1)$ diagnosed for NIHL were 11.1 % and 0.44 %. There were significant difference in the prevalences of C and $D_1$, depending on different province of Korea. Pure tone averages (PTAs) were not appropriately applied in their evaluation 97% of workers whom we studied on were below the level of mild hearing loss judged by ISO standard. However, there were wide variations in the prevalence rate of mild hearing loss by diagnostic criteria. Thus, there were different judgements in determining the degree of NIHL depending on which diagnostic criteria were utilized. PTAs were found 20.54 (Rt) and 20.74 (Lt) when the method of 3-divided classification was applied for audiometric data. The degree of hearing impairment of the left ear was more severe than that of right ear. The prevalence of normal hearing threshold below 20 dB was 75.4% and the range of difference in both ear was below 10 dB. Right sided hearing threshold levels were 21.08 dB (500 Hz), 18.44 dB (1,000 Hz), 22.09 (2,000 Hz) and 52.36 dB (4,000 Hz). There was typical high frequency loss (C5-dip at 4,000 Hz) above 30 - 40 dB in normal hearing level. The increasing trend in hearing threshold level was gradually decreased by the increase of PTAs. The difference between PTAs and threshold at 4,000 Hz was about 10 dB. Conclusions. We could found that PTAs in the previous examination were not appropriately evaluated. This study revealed that they did not use unique criteria for managing the workers of NIHL. For the prevention of NIHL, it was found that the quality control on diagnosis and comprehensive management program were required, especially for those of hearing loss (C).

• Journal of Korean Society of Forest Science
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• v.110 no.2
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• pp.210-216
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• 2021

Musculoskeletal disorders affect workers' safety in most industries, and forest operations are classified as a musculoskeletal burden according to the Occupational Safety and Health Act in South Korea. In particular, felling and delimbing operations are mainly conducted by manpower, and then, it is necessary to evaluate ergonomic risk assessment for safety of felling and delimbing workers. Three ergonomic risk assessment methods, such as Ovako Working posture Analysis System (OWAS), Rapid Upper Limb Assessment (RULA), and Rapid Entire Body Assessment (REBA), are available for assessing exposure to risk factors associated with timber harvesting operations. Here, three ergonomic risk assessment methods were applied to examine ergonomic risk assessments in chainsaw felling and delimbing operations. Additionally, exposure to risk factors in each method was analyzed to propose an optimal working posture in felling and delimbing operations. The risk levels of these operations were evaluated to be highest in the RULA method, followed by the OWAS and REBA methods, and most of the exposed working postures were examined with a low-risk level of two and three without requiring any immediate working posture changes. However, two significant working postures, including the bending posture of the waist and leg in felling operation and standing posture on the fallen trees in delimbing operation, were assessed as the high-risk level and needed immediate working posture changes. Low-risk work levels were examined in the squatting posture for felling operation and the straightened posture of the waist and leg for delimbing operation. Moreover, the slope in felling operation and the tree height in delimbing operation significantly affected risk level assessment of working posture. Therefore, our study supports that felling and delimbing workers must operate with low-risk working postures for safety.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.24 no.4
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• pp.518-527
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• 2014

Objectives: The adverse health effects attributed to exposure to radon have been well known over the world. However, the efforts for prevention and mitigation of radon have not been taken in Korea so far. The purpose of this study was to evaluate the effectiveness of mitigation methods applied for various types of houses and public buildings with high level of radon. Methods: Based on the results of "National Radon Survey" performed by the National Institute of Environmental Research(NIER) in 2010-2012, we selected 30 candidate buildings consisting of 20 houses and 10 public buildings with greater than $148Bq/m^3$ of radon level. We measured the concentration of radon in 30 buildings, using E-PERMs and RAD-7 during January to March of 2013. More than five E-PERMs and one RAD-7 per house were installed for seven days. Ten houses and five public buildings were finally chosen to be mitigated after mainly considering the level of radon and the location of buildings nationwide. Three mitigation methods such as Sealing, two types of Active Ventilation(window-shaped and wall-typed ventilations), and Active Soil Depressurization(ASD) were applied, and the concentrations of radon were measured before and after mitigation, respectively. To evaluate the effectiveness of mitigation methods, reduction rates of radon were calculated and Wilcoxon's signed-rank test was performed. Results: The mean concentration of 15 buildings just before radon mitigation was $297.8Bq/m^3$, and most of the buildings were located in Gangwon, Chungbuk, Chungnam, and Daegu areas(73.3%), and built in 1959-1998. The level of radon decreased from 48% to 90% and kept the below recommendation limit of $148Bq/m^3$ after installation of radon mitigation. Among mitigation methods applied, the reduction rate(58.7-90.4%) of radon attributed to ASD was the greatest than that of other methods, followed by Active Ventilation(48.4-78.4%) and Sealing(<22%). The effectiveness of radon reduction by window-shaped Active Ventilation(63.2-75.2%) was relatively better than that of wall-typed Active Ventilation(48.4-54.3%). Conclusions: The results of this study indicate that ASD could be more effective for radon mitigation. Moreover, our findings would be background information in future for making the strategy for radon mitigation nationwide, as well as for developing Korean-version of mitigation techniques according to types of dwellings in Korea.