The purpose of this study was to compare the performance characteristics of Andersen and total suspended particulate (TSP) samplers in terms of particle size distribution (PSD) and mass sampling efficiency. In the present study, two Andersen and four TSP samplers were selected and tested to quantitatively estimate human exposure to fly ash representing industrial particulate matter (PM) in a carefully controlled chamber. The PSD characteristics, a mass median aerodynamic diameter and a geometric standard deviation, were found from the sampled PM of airborne samplers in the chamber. An Andersen sampler was compared with a TSP sampler quantified by a coulter counter multisizer, as a reference sampler, to describe the correlation of mass sampling efficiencies between two types of samplers. Overall results indicate that Andersen samplers overestimated small PM due to particle bounce phenomena between impaction stages. There was reasonably good correlation ($R^2$ = 0.89 and 0.91) between the mass sampling efficiencies of Andersen and TSP samplers during the two tests. However, the lower values of slope (0.71 and 0.72) in two tests showed that the Andersen sampler underestimated PM (> AD $10.1\;{\mu}m$) with sufficient inertia due to a relatively lower Andersen inlet velocity at 0.8 m/s comparing with the operating air velocity at 2.1 m/s in the sampling zone of a chamber.

Objectives: The purpose of this study is to analyze the occupational safety and health(OSH) state of precarious employee. Methods: The questionnaire of this survey is composed of 9 categories that are the workplace general information and the state of occupational injury and disease, OSH organization, OSH education and training. The subjects of this survey were the Manufacturing. The hypothesis of this study is where the proportion of precarious employee is higher, the OSH state is worse. To verify this hypothesis, we grouped the subjects into three categories by the proportion of precarious employee like as 0%(all standard employee), less than 30% and 30% or more. Using the SPSS 12.0 program to analyze the data, logistic regression analysis were implemented to find affective factors for the rate of occupational injury and disease. Results: 2,633 manufacturing workplaces were included for subjects. The proportions of precarious employee were 9.6 %. In manufacturing industry, about 70 % companies had no precarious employee. 16.8 % companies were in less than 30 % group, 13.2 % companies were in 30% or more group. For the rate of occupational injury and disease, the precarious group were 0.85(${\pm}1.8$), 1.19(${\pm}2.9$), 0.59(${\pm}1.1$). There was a trend that the higher precarious proportion groups was the higher rate of occupational injury and disease by the logistic regression analysis. It is more strong relationship than company size and OSH committee. Conclusions: We could find a significant result there was a positive relationship between the hiring proportion of precarious employee and the rate of occupational injury and disease in manufacturing industry with 50 employees and more.

Cylindrical bag filter system with pulse jet cleaning has been the most common device to control particle laden exhaust gas from the various industrial processes. But, it has many shortcomings due to particle reattachment and frequent bag rupture. In recent years, rectangular type bag filter system has been developed to overcome the problems associated with the cylindrical system. However, not many studies about the rectangular system were not done, compared to the cylindrical system. In this study, the optimum pulse jet cleaning conditions were thus tested by the series of experiments. The factors tested in this study are pulse distance, pulse pressure, pulse duration, the number of holes for pulsing and bag materials. A single bag ($1,500mmL{\times}50mmW{\times}300mmH$) system and a multi-bags (3 bags in a row) were tested separately. The highest removal efficiency with a single bag system was found at the conditions with pulse distance of 10cm, pulse pressure of $3kg/cm^2$, pulse duration of 0.3s, pulse jet number of 6 and Polyester bag. With the multi-bags system, the best cleaning conditions were found at the bag interval of 20cm with the simultaneous pulsing and the bag interval of 15cm with the serial pulsing.

Many researches for service-life of chemical cartridges of respirators have been performed in many countries. On the result of these researches a few softwares programs were eventually developed to be used. In spite of that, it is difficult to apply these researches and softwares practically in the work spot because of too many factors that influence on service-life of chemical cartridges. This study was the first of two conducted for the purpose of developing program for estimating exchange period or service-life of chemical cartridges available feasibly in the workplaces. Collecting plan of cartridges discarded after use is in principle that three cartridges from three workers at a time, three steps of 1/2 exchange time due to smelling, just routine exchange time and 1.2 to 1.3 expanded time of routine exchange, total nine cartridges are collected in the same job site. 33 cartridges for organic vapor were collected in paint spray process of ship yard and paint factory, and 6 cartridges for acid were collected in plating process. These cartridges were analysed the remaining breakthrough time in 3M Innovation Center. Challenge vapor and breakthrough concentration were complied with Korean regulation for chemical cartridge respirators. Estimated breakthrough time was determined from previously used time plus breakthrough time for the remaining. Exchange period of cartridge would be the shortest time among three estimated breakthrough times. On the result breakthrough time for organic vapor was found to be relatively easily estimated, but that for acid aerosol or vapor was difficult to be confident. Even though this method was difficult to be precisely predicted exchange period of cartridge, it could be an alternative program practically available in the job site.

Objectives : To investigate the effect of overtime work on fatigue symptoms among Korean female workers. Methods : A total of 1,875 subjects were analyzed using the structured questionnaire, which was composed of overtime work, fatigue symptom, and background characteristics. Data analysis included multiple regression to test for a relationship of overtime work with fatigue symptom while statistically controlling for demographic and occupational variables. Results : Overtime work was more common in those with shorter work years of 3 or less than in those with longer work years. Overtime work was more popular in day workers than in shift workers. No significant difference of smoking and drinking state was observed between two groups. Subjective fatigue symptoms were significantly higher in overtime workers than in workers without overtime work. In a multiple regression analysis with significant control variables, overtime work was associated with 0.31 more fatigue symptom(p<0.001). Conclusion : Our findings suggest that overtime work may increase risks for fatigue symptom. Therefore, preventive strategies will be needed to control the negative effect of overtime work on health status of female workers.

The aim of this study is to confirm the physicochemical property and hazard of thinner (012), which is a diluent of enamel paint used for floor coating for waterproofing and oil painting for the outer wall. The literatures of physicochemical property and hazard of thinner were surveyed and its physicochemical property were evaluated. And then, the inhalation toxicity of thinner affecting the central nervous system and reproductive organs in rats were examined by subchronic (6 h./day. 5 days/ week for 13 weeks) inhalation test. 1) According to the 13-week subchronic inhalation test, there were no significant changes in clinical test and body weight. However, a significant evidence of toxicity was observed in the hematological test and organ weight such as heart, kidney, liver and brain (p<0.01) in the 200 ppm and 1,000 ppm exposure groups in a dose response manner. In the histopathology analysis, there were no significant evidence of toxicity. Therefore, thinner was not classified as an organ targeted toxic agent. In case of Harmfulness, it could be classified as a chronic toxic agent 3($500 ppm/4hr, rat). 2) The reproductive toxicity such as extension of the period of estrous cycle, reduction of serum estradiol concentration and increase of frequency of the abnormal sperm was observed in the 1,000 ppm exposed animals. 3) The result of the physicochemical property of the test material showed that the specific gravity was 0.793, boiling point $155.8^{\circ}C$, steam pressure 2.1 kPa, ignition point $34.5^{\circ}C$, and spontaneous ignition point $280^{\circ}C$. The endothermic and exothermic values were 371.4 J/g and 159.1 J/g. respectively. The explosion limit was 214 mg/l. These data showed that thinner could be classified as an explosion agent level 1.2 and ignitive liquid agent 3 ($23-60^{\circ}C$) according to the notification No. 2008-1 of the Labor Ministry, "Classifying Standard of Chemical Materials."

Low back disorders (LBDs) have been the most common musculoskeletal problem in Korean workplaces. It affects many workers, and is associated with high costs to many companies as well as the individual, which can negatively influence even the quality of life of workers. The _evaluation of low back disorder risk associated with manual materials handling tasks can be performed using variety of ergonomic assessment tools such as National Institute for Occupational Safety and Health (NIOSH) Revised Lifting Equation (NLE), the Washington Administrative Code 296-62-0517 (WAC), the Snook Tables etc. But most of these tools provide limited information for choosing the most appropriate assessment method for a particular job and in finding out advantage and disadvantage of the methods, and few have been assessed for their predictive ability. The focus of this study was to _evaluate spinal loads in real time with lifting and pulling heavy cow leathers in variety of postures. Data for estimating mean trunk motions were collected as employees did their work at the job site, using the Lumbar Motion Monitor. Eight employees (2 males, 6 females) were selected in this study, in which the load weight and the vertical start and destination heights of the activity remained constant throughout the task. Variance components (three dimensional spaces) of mean trunk kinematic measures were estimated in a hierarchical design. They were used to compute velocity and acceleration of multiple employees performing the same task and to repetitive movements within a task. Therefore, a results of this study could be used as a quantitative, objective measure to design the workplace so that the risk of occupationally related low back disorder should be minimized.

During survey of blood lead concentration of workers who worked in lead refining industry, we found that some foreign workers showed increased blood lead level compared with that of domestic workers. The mean concentration of lead in blood for foreign workers (15%, 13 workers, mean age: 29) was 55.8 ug/dL which was over biological exposure index, while that of Korean workers (85%, 76 workers, mean age: 42) was 28.9 ug/dL. Some other biological markers of lead exposure such as ZPP and ${\delta}-ALA$ also showed elevated levels. Most of foreign workers stayed in dormitories near or in the factories that may cause to let them under the condition of 24 hours exposure of lead. The lack of safety manual on proper prevention of lead exposure in their own language for effective communication may be one of reasons of elevated blood lead concentration of foreign workers.