• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.24 no.3
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• pp.256-262
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• 2014

Objectives: The purpose of this study was to identify the major volatile organic compounds generated during extrusion work with nylon 66 resin and evaluate causes of discomfort among extrusion workers. Methods: A thermal decomposition experiment using nylon 66 resin collected at a worksite was conducted in the laboratory. Based on hazards identified through the thermal decomposition experiment, the exposure levels of the workers were evaluated. Results: The major decomposition products were formaldehyde, acetaldehyde, aniline, cyclopentanone and diphenyl amine. These materials were identical to those sampled in the extrusion booth. The sources of the annoying smells, about which the workers had complained, were formaldehyde, aniline, diphenyl amine, and other hazards in the vapor and fine particles produced by the extrusion work. Formaldehyde, acetaldehyde, and aniline were detected from air samples among workers involved in extrusion work. However, the concentration levels were much lower than Korean occupational exposure limits. The average concentration levels of formaldehyde, acetaldehyde, and aniline were 0.0120 ppm, 0.0036 ppm and 0.0006 ppm, respectively. Conclusions: The extrusion process at around $300^{\circ}C$ thermally decomposes the nylon 66 resin, emitting formaldehyde, aniline, and other hazards, which might have made workers uncomfortable due to their smells. The workers exposure levels to volatile organic compounds were far lower than Korean occupational exposure limits. However, since formaldehyde is a human carcinogen and acetaldehyde and aniline are also confirmed animal carcinogens, it is recommended that exposure levels should be maintained at a minimum level.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.7
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• pp.688-693
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• 2008

TiO$_2$ photocatalyst films deposited beads were prepared by circulating fluidized bed chemical vapor deposition(CFB-CVD) using TTIP(Titanium Tetra Iso-Propoxyde). Photocatalytic activities of Photocatalyst beads were evaluated by decomposition rate of formaldehyde in aqueous solution using a photo-reactor. From the result of photocatalytic degradation of formaldehyde, decomposition rate were shown gradually increased according to the increase of UV intensity, circulating fluid velocity and addition amount of H$_2$O$_2$. However the decomposition rate of formaldehyde were decreased according to the increase of initial concentration and pH value.

• Microbiology and Biotechnology Letters
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• v.34 no.3
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• pp.216-220
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• 2006

Thermophillic fungus Thermoascus aurantiacus showed excellent growth and produced high amount of alcohol oxidase and catalase in a pectin medium. Besides, the strain produced enzymes which related with pectin or alcohol decomposition. We detected extracellular pectin esterase (EC 3.1.1.11) activity and, both intracellular and extracellular pectinase (EC 4.2.2.10) activity, as pectinolytic enzymes produced by T. aurantiacus. The production of methanol decomposition enzymes, such as alcohol oxidase (AOD, EC 1.1.3.13), alcohol dehydrogenase (ADH, EC 1.1.1.1), formaldehyde dehydrogenase (FADH, EC 1.2.1.1) and formate dehydrogenase (FDH, EC 1.2.1.2) follows by pectin esterase reaction which is converted to methanol. We concluded that T. aurantiacus has pectinolytic and alcohol - oxidative enzymological mechanism which produced carbon dioxide as a final material, started from pectin.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.22 no.1
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• pp.52-59
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• 2012

Objectives: The purpose of this study was to evaluate the exposure possibility of by-products during the semiconductor manufacturing processes. Methods: The authors investigated types of chemicals generated during semiconductor manufacturing processes by the qualitative experiment on generation of by-products at the laboratory and a literature survey. Results: By-products due to decomposition of photoresist by UV-light during the photo-lithography process, ionization of arsine during the ion implant process, and inter-reactions of chemicals used at diffusion and deposition processes can be generated in wafer fabrication line. Volatile organic compounds (VOCs) such as benzene and formaldehyde can be generated during the mold process due to decomposition of epoxy molding compound and mold cleaner in semiconductor chip assembly line. Conclusions: Various types of by-products can be generated during the semiconductor manufacturing processes. Therefore, by-products carcinogen such as benzene, formaldehyde, and arsenic as well as chemical substances used during the semiconductor manufacturing processes should be controlled carefully.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 1997.04a
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• pp.55-57
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• 1997

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.6
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• pp.1284-1291
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• 2006

This work examined improving the activity of photocatalyts by novel metal doping for the degradation of volatile organic compounds, such as formaldehyde and acetone. The activity was determined with type of dopant novel metal and volatile organic compounds. The palladium-doped $TiO_2$ was found to be improved the decomposition of acetone. The photocatalytic degradation rate for acetone was increased with decreasing temperature to $45^{\circ}C$. The optmum temperature of photocatalytic degradation rate for formaldehyde was $75^{\circ}C$. The enhancement of reaction rate with novel metal were 1.0 wt.% of palladium for acetone, 1.0 wt.% of plaitnum for formaldehyde.

• Bulletin of the Korean Chemical Society
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• v.24 no.11
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• pp.1618-1622
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• 2003

The photochemical reactions of methanolic nalidixic acid (NAL) solution in the absence and in the presence of air have been investigated using 300 nm UV light. From the reactions, 1-ethyl-7-methyl-4-oxo-4-hydro-1,8-naphthyridine (EMDN),formic acid, and formaldehyde are produced. In the presence of air, hydrogen peroxide is also detected along with the products listed above. The presence of oxygen during the irradiation of methanolic NAL solution effects on the product yield. The initial quantum yields of the products and of the NAL decomposition are determined. Possible reaction pathways for the photochemical reaction are suggested on the basis of the products analysis.

• Journal of Preventive Medicine and Public Health
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• v.27 no.2 s.46
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• pp.274-285
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• 1994

The effects of resin on the respiratory health have been investigated in 309 workers from four iron and steel foundries and the results compared with those from 122 workers who were not significantly exposed to resin gas and silica dust at the same industries. Phenol-formaldehyde resin was used in the core making and molding processes and workers were exposed to their decomposition products as well as to silica dust containing particulates. The subjects were grouped according to formaldehyde, dust and other gas exposures, and smoking habits were considered also in thi analysis. Standardized respiratory symptom questionnaire was administered by trained interviewers. Chest radiograph, pulmonary funtion tests, and methacholine challenge tests were done. Environmental measurements at the breathing zone were carried out to determine levels of formaldehyde, respiable dust and total dust. Foundry workers had a higher prevalence of symptoms of chronic bronchitis with chronic phlegm and chronic cough when exposed to dust. Exposure to gas was significantly associated with lowered $FEV_1$ and obstructive pulmonary function changes. Exposure to formaldehyde and phenol gas was associated with wheezing symptom among workers, but $FEV_1$ changes after methacholine challenge were not significantly different among different exposure groups. When asthma was defined as the presence of bronchial hyperreactivity with more than 20% decrease in $FEV_1$ after methacholine challenge, 17 workers out of 222 tested had asthma. Fewer asthmatic welters were found among groups exposed to formaldehyde, gas and dust, which indicates a healthy worker effects ill a cross-sectional study. The concentration of formaldehyde gas ranged from 0.24 to 0.43 ppm among studied foundries. The authors conclude that formaldehyde and phenol gas from combusted resin is probably the cause of asthmatic symptoms and also a selection force of those with higher bronchial reactivity away from exposures.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.24 no.3
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• pp.272-280
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• 2014

Objectives: The purpose of this study was to evaluate the characteristics of worker exposure to hazardous chemical substances and propose the direction of work environment management for protecting worker's health in the semiconductor assembly process. Methods: Four assembly lines at two semiconductor manufacturing companies were selected for this study. We investigated the types of chemicals that were used and generated during the assembly process, and evaluated the workers' exposure levels to hazardous chemicals such as benzene and formaldehyde and the current work environment management in the semiconductor assembly process. Results: Most of the chemicals used at the assembly process are complex mixtures with high molecular weight such as adhesives and epoxy molding compounds(EMCs). These complex mixtures are stable when they are used at room temperature. However workers can be exposed to volatile organic compounds(VOCs) such as benzene and formaldehyde when they are used at high temperature over $100^{\circ}C$. The concentration levels of benzene and formaldehyde in chip molding process were higher than other processes. The reason was that by-products were generated during the mold process due to thermal decomposition of EMC and machine cleaner at the process temperature($180^{\circ}C$). Conclusions: Most of the employees working at semiconductor assembly process are exposed directly or indirectly to various chemicals. Although the concentration levels are very lower than occupational exposure limits, workers can be exposed to carcinogens such as benzene and formaldehyde. Therefore, workers employed in the semiconductor assembly process should be informed of these exposure characteristics.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2001.11a
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• pp.291-292
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• 2001

자동차 운행 및 산업화로 인한 유류 및 유기용제의 사용증가는 배출되는 휘발성 유기화합물의 증가로 이어졌다. 이로 인해 광학적 스모그의 생성과 오존층파괴, 지구 온난화 그리고 악취공해 유발등 환경오염을 촉진시키고 자체의 유해한 성질로 환경 및 건강에 심각한 영향을 초래하여 이러한 오염물질의 제거를 위한 수단으로 광촉매반응이 최근 주목을 받고 있다. (중략)