Exposure to Volatile Organic Compounds and Possibility of Exposure to By-product Volatile Organic Compounds in Photolithography Processes in Semiconductor Manufacturing Factories

OBJECTIVES: The purpose of this study was to measure the concentration of volatile organic compound (VOC)s originated from the chemicals used and/or derived from the original parental chemicals in the photolithography processes of semiconductor manufacturing factories. METHODS: A total of four photolithography processes in 4 Fabs at three different semiconductor manufacturing factories in Korea were selected for this study. This study investigated the types of chemicals used and generated during the photolithography process of each Fab, and the concentration levels of VOCs for each Fab. RESULTS: A variety of organic compounds such as ketone, alcohol, and acetate compounds as well as aromatic compounds were used as solvents and developing agents in the processes. Also, the generation of by-products, such as toluene and phenol, was identified through a thermal decomposition experiment performed on a photoresist. The VOC concentration levels in the processes were lower than 5% of the threshold limit value (TLV)s. However, the air contaminated with chemical substances generated during the processes was re-circulated through the ventilation system, thereby affecting the airborne VOC concentrations in the photolithography processes. CONCLUSION: Tens of organic compounds were being used in the photolithography processes, though the types of chemical used varied with the factory. Also, by-products, such as aromatic compounds, could be generated during photoresist patterning by exposure to light. Although the airborne VOC concentrations resulting from the processes were lower than 5% of the TLVs, employees still could be exposed directly or indirectly to various types of VOCs.

Quantitative Exposure Assessment of Various Chemical Substances in a Wafer Fabrication Industry Facility

OBJECTIVES: This study was designed to evaluate exposure levels of various chemicals used in wafer fabrication product lines in the semiconductor industry where work-related leukemia has occurred. METHODS: The research focused on 9 representative wafer fabrication bays among a total of 25 bays in a semiconductor product line. We monitored the chemical substances categorized as human carcinogens with respect to leukemia as well as harmful chemicals used in the bays and substances with hematologic and reproductive toxicities to evaluate the overall health effect for semiconductor industry workers. With respect to monitoring, active and passive sampling techniques were introduced. Eight-hour long-term and 15-minute short-term sampling was conducted for the area as well as on personal samples. RESULTS: The results of the measurements for each substance showed that benzene, toluene, xylene, n-butyl acetate, 2-methoxyethanol, 2-heptanone, ethylene glycol, sulfuric acid, and phosphoric acid were non-detectable (ND) in all samples. Arsine was either "ND" or it existed only in trace form in the bay air. The maximum exposure concentration of fluorides was approximately 0.17% of the Korea occupational exposure limits, with hydrofluoric acid at about 0.2%, hydrochloric acid 0.06%, nitric acid 0.05%, isopropyl alcohol 0.4%, and phosphine at about 2%. The maximum exposure concentration of propylene glycol monomethyl ether acetate (PGMEA) was 0.0870 ppm, representing only 0.1% or less than the American Industrial Hygiene Association recommended standard (100 ppm). CONCLUSION: Benzene, a known human carcinogen for leukemia, and arsine, a hematologic toxin, were not detected in wafer fabrication sites in this study. Among reproductive toxic substances, n-butyl acetate was not detected, but fluorides and PGMEA existed in small amounts in the air. This investigation was focused on the air-borne chemical concentrations only in regular working conditions. Unconditional exposures during spills and/or maintenance tasks and by-product chemicals were not included. Supplementary studies might be required.

A Case of Pituitary Apoplexy Misdiagnosed as Aseptic Meningitis / 대한내과학회지

Pituitary apoplexy is a clinical syndrome caused by an acute ischemic or hemorrhagic vascular accident. Although pituitary apoplexy is an emergency, it is often overlooked because it is rare and presents with various signs and symptoms, including those of neurologic and endocrine disorders. We describe a case of pituitary apoplexy misdiagnosed as aseptic meningitis accompanied by acute-onset headache and nausea, followed by fever. Subsequently, it was revealed as pituitary apoplexy by brain magnetic resonance imaging (MRI) performed when the clinical course worsened and ophthalmoplegia developed. We suggest that pituitary apoplexy be included in the differential diagnosis of patients presenting with headache or signs of meningeal irritation; when there is no clinical improvement, prompt steroid treatment should be started, while considering neurological decompression to prevent neurological sequelae.

A Case of Pituitary Abscess that was Difficult to Diagnose due to Repeated Symptomatic Responses to Every Corticosteroid Administration

Pituitary abscess is a rare pathology, but it is a potentially life-threatening condition. Therefore, timely intervention, including antibiotics and an operation, can prevent the morbidity and mortality in such cases. A 31-year-old woman, who was 16 months after her second delivery, presented with intermittent headache for 3 months. Amenorrhea, polyuria and polydipsia were noticed and the endocrinological hormone studies were compatible with panhypopituitarism and diabetes insipidus. Pituitary MRI demonstrated a 2.3 cm sized cystic mass with an upper small nodular lesion. Her symptoms such as headache and fever were repeatedly improved whenever corticosteroid was administered, which led us to suspect the diagnosis of an inflammatory condition like lymphocytic hypophysitis. During the hormone replacement therapy, her cystic pituitary mass had grown and her symptoms progressively worsened for another two months. The patient underwent trans-sphenoidal exploration and she turned out to have a pituitary abscess. At the 3-month follow-up, amenorrhea was noticed and her residual function of the pituitary was tested by a combined pituitary stimulation test. The results were compatible with panhypopituitarism. She received levothyroxine 100 microg, prednisolone 5 mg and desmopressin spray and she is being observed at the out-patient clinic. The authors experienced a patient with primary pituitary abscess that was confirmed pathologically and we report on its clinical course with a literature review.

Characteristics of Occupational Exposure to Benzene during Turnaround in the Petrochemical Industries

OBJECTIVES: The level of benzene exposure in the petrochemical industry during regular operation has been well established, but not in turnaround (TA), where high exposure may occur. In this study, the characteristics of occupational exposure to benzene during TA in the petrochemical companies were investigated in order to determine the best management strategies and improve the working environment. This was accomplished by evaluating the exposure level for the workers working in environments where benzene was being produced or used as an ingredient during the unit process. METHODS: From 2003 to 2008, a total of 705 workers in three petrochemical companies in Korea were studied. Long- and short-term (< 1 hr) samples were taken during TAs. TA was classified into three stages: shut-down, maintenance and start-up. All works were classified into 12 occupation categories. RESULTS: The long-term geometric mean (GM) benzene exposure level was 0.025 (5.82) ppm (0.005-42.120 ppm) and the short-term exposure concentration during TA was 0.020 (17.42) ppm (0.005-61.855 ppm). The proportions of TA samples exceeding the time-weighted average, occupational exposure level (TWA-OEL in Korea, 1 ppm) and the short-term exposure limit (STEL-OEL, 5 ppm) were 4.1% (20 samples of 488) and 6.0% (13 samples of 217), respectively. The results for the benzene exposure levels and the rates of exceeding the OEL were both statistically significant (p < 0.05). Among the 12 job categories of petrochemical workers, mechanical engineers, plumbers, welders, fieldman and scaffolding workers exhibited long-term samples that exceeded the OEL of benzene, and the rate of exceeding the OEL was statistically significant for the first two occupations (p < 0.05). CONCLUSION: These findings suggest that the periodic work environment must be assessed during non-routine works such as TA.

Characteristics of Occupational Exposure to Benzene during Turnaround in the Petrochemical Industries

OBJECTIVES: The level of benzene exposure in the petrochemical industry during regular operation has been well established, but not in turnaround (TA), where high exposure may occur. In this study, the characteristics of occupational exposure to benzene during TA in the petrochemical companies were investigated in order to determine the best management strategies and improve the working environment. This was accomplished by evaluating the exposure level for the workers working in environments where benzene was being produced or used as an ingredient during the unit process. METHODS: From 2003 to 2008, a total of 705 workers in three petrochemical companies in Korea were studied. Long- and short-term (< 1 hr) samples were taken during TAs. TA was classified into three stages: shut-down, maintenance and start-up. All works were classified into 12 occupation categories. RESULTS: The long-term geometric mean (GM) benzene exposure level was 0.025 (5.82) ppm (0.005-42.120 ppm) and the short-term exposure concentration during TA was 0.020 (17.42) ppm (0.005-61.855 ppm). The proportions of TA samples exceeding the time-weighted average, occupational exposure level (TWA-OEL in Korea, 1 ppm) and the short-term exposure limit (STEL-OEL, 5 ppm) were 4.1% (20 samples of 488) and 6.0% (13 samples of 217), respectively. The results for the benzene exposure levels and the rates of exceeding the OEL were both statistically significant (p < 0.05). Among the 12 job categories of petrochemical workers, mechanical engineers, plumbers, welders, fieldman and scaffolding workers exhibited long-term samples that exceeded the OEL of benzene, and the rate of exceeding the OEL was statistically significant for the first two occupations (p < 0.05). CONCLUSION: These findings suggest that the periodic work environment must be assessed during non-routine works such as TA.

A Study for Health Hazard Evaluation of Methylene Chloride Evaporated from the Tear Gas Mixture

This study explored the health hazard of those exposed to methylene chloride by assessing its atmospheric concentration when a tear gas mixture was aerially dispersed. The concentration of methylene chloride ranged from 311.1-980.3 ppm (geometric mean, 555.8 ppm), 30 seconds after the dispersion started. However, the concentration fell rapidly to below 10 ppm after dispersion was completed. The concentration during the dispersion did not surpass the National Institute for Occupational Safety and Health 'immediately dangerous to life or health' value of 2,300 ppm, but did exceed the American Conference of Governmental Industrial Hygienists excursion limit of 250 ppm. Since methylene chloride is highly volatile (vapor pressure, 349 mmHg at 20degrees C), the postdispersion atmospheric concentration can rise instantaneously. Moreover, the o-chlorobenzylidenemalononitrile formulation of tear gas (CS gas) is an acute upper respiratory tract irritant. Therefore, tear gas mixtures should be handled with delicate care.

Hematochezia with Colonic Polypoid Angiodysplasia in a Young Female Patient

A 18-year-old girl visited the hospital due to hematochezia. Colonoscopy revealed a 6-mm Yamada type II polyp with stigmata of bleeding, and a shallow ulcer on top was found at the cecum base. The polyp was removed by snare polypectomy, and hematochezia stopped thereafter. Angiodysplasia was diagnosed histopathologically. Generally, angiodysplasia appears as a flat or elevated, bright-red lesion on endoscopy, with a polypoid shape being extremely rare. This case is significant because the lesion occurred at the youngest reported age and was the smallest that has been reported, and is the only polypoid arteriovenous malformation to be discovered in the cecum.

A Case of Hypercapnic Respiratory Failurein a Patient with Eosinophilic Polymyositis / 대한류마티스학회지

Eosinophilic infiltration into skeletal muscles has been rarely reported in a variety of conditions such as parasite infection, sarcoidosis, rheumatoid arthritis, eosinophilia-myalgia syndrome, and idiopathic hypereosinophilic syndrome. Eosinophilic myositis (EM) is one of idiopathic inflammatory muscle diseases associated with muscle and/or blood eosiophilia. The case of EM complicated with hypercapnic respiratory failure has been extremely rarely reported. A 61-year-old woman was admitted with sudden-onset pain in both calves. She had elevated serum muscle enzymes and peripheral eosinophil count. Findings of electromyography were consistent with inflammatory myopathy. MRI showed diffuse hyperintensity of calf muscles on T2-weighted and enhanced T1 images. Muscle biopsy showed eosinophils' infiltration in the endomysium and perivascular area. During the diagnostic work-up, she presented with hypercapnic respiratory failure. She was successfully treated with mechanical ventilation and high doses of prednisolone. This case suggests EM can cause respiratory failure secondary to respiratory muscle involvement.

Remediable Hyperglycemia in a Patient with Weber-Christian Disease / 대한류마티스학회지

Weber-Christian disease (WCD) is an inflammatory disease of subcutaneous fat tissue which is characterized by relapsing, febrile tender nodules and histologically lobular panniculitis. Any area of the body containing fat can be affected by WCD. Several cases of WCD have been reported as involvement of the heart, lung, liver and kidney. Acute illness (ex. acute myocardiac infarction, infection, etc) can be complicated with stress-related hyperglycemia and increase insulin restistance. Finally this case show that Weber-Christian disease accompanied by marked hyperglycemia and insulin resistance, which resolved soon after corticosteroid.

A case report of infective endocarditis of the aortic valve in a patient with an implanted pacemaker / 대한내과학회지

Infective endocarditis related to pacemaker implantation is a rare complication. However, it is a potentially lethal complication with a mortality rate of 30 to 35%. Infective endocarditis associated with pacemaker implantation usually involves the right heart and tricuspid valve. Conservative treatment without complete removal of the entire pacing system is prone to fail (i.e. result in infection relapse or development of sepsis). Therefore, the total extraction of the entire pacemaker system should be considered as standard therapy for most patients with pacemaker-related endocarditis and for many patients with local infectious symptoms at the site of pacemaker implantation to achieve complete recovery. We report a case of a 42-year-old man with documented pacemaker related left-sided endocarditis that was associated with multiple embolic events. Also, we review the literature regarding pacemaker-related endocarditis and local wound infection, in particular with respect to the modalities of treatment.