Aerospace medicine and biology: A continuing bibliography with indexes, supplement 190, February 1979

This bibliography lists 235 reports, articles, and other documents introduced into the NASA scientific and technical information system in January 1979

dynamic modelling of the swash plate of a hydraulic axial piston pump for condition monitoring applications

Abstract In the last years Prognostic and Health Management (PHM) has become one of the challenging topic in the engineering field. In particular, model-based approach for diagnostic relies on the development of a mathematical model of the system representing its flawless status. Once the model has been developed and carefully calibrated on experimental data referred to flawless pump condition the comparison between the model output and the real system output leads to the residual analysis, which gives a diagnosis of the component health. This paper presents the mathematical model of a hydraulic axial piston pump developed in order to replicate the dynamic behavior of the swash plate for PHM applications. The model has been developed on the basis of simplified hypotheses, a friction model between swash plate and bearings has been introduced. A detailed experimental activity was carried out to calibrate and validate the model with step tests and sweep tests. The comparison between numerical and experimental results shows a satisfying agreement and highlights the model capability to reproduce the swash plate dynamics. Future works will include tests with the pump in faulty conditions to evaluate the pump health state through the residual analysis of the swash plate position

Alcohol Flexible Dual-Fuel Direct Injection Engine

Laws concerning emissions from HD internal combustion engines are becoming increasingly stringent in terms of local emissions and emissions concerning global warming such as lowering tailpipe CO2. New engine technologies are needed to satisfy these new requirements and to reduce fossil fuel dependency and increase renewable fuels in the transportation sector. One way to achieve both objectives can be to partially replace fossil fuels with alternatives that are sustainable with respect to emissions of greenhouse gases and engine out particulates. Also a decrease in NOx can be achieved. Suitable candidates are ethanol or methanol. The thesis presented here summarizes results from publications and additional results presented here with the aim to investigate the possible advantages of combusting low carbon alcohol fuels in dual-fuel configuration in a HD Diesel engine - in particular, the potential to greatly reduce particulate emissions and thereby bypass the soot-NOx tradeoff and lowering tailpipe CO2 emissions. It was complimented by additional results presented in the kappa itself.Ethanol sprays were studied in a high pressure/temperature spray chamber at typical engine condition with gas densities of about 27 kg/m^3 at around 550 C and around 60 bar. Spray parameters, such as the liquid cone angle, liquid penetration length and vapor penetration at injection pressures up to 2200 bar, were investigated. The characterization of those sprays was followed by an investigation focusing on the combustion of alcohol fuels in a single cylinder engine. Methanol, ethanol and E85 were chosen, but because of their poor auto-ignition properties, a pilot Diesel injection was used to initiate the combustion process. One of the alcohol fuels and Diesel were injected directly but separately, necessitating the use of two separate common rail systems together with a newly designed cylinder head and adapted injection nozzles. The dual fuel system\u27s combustion properties were compared to those of pure Diesel with the same dual injection strategy. The injection pressure on the alcohol side were varied up to 2000 bar and investigations were carried out at low, medium and high speed-load points, with and without EGR. The investigated low carbon fuels outperformed Diesel under all tested conditions in terms of thermal efficiency and indicated specific NOx, soot and CO2 emissions. Thermal efficiency was increased by up to 3.5 %-points and simultaneously soot emissions were lowered by a factor of 40 or more and NOx by 20 %. ISCO2 emissions were down by up to 25 %. The fuel substitution ratio was over 95 % and the combustion stability was not compromised

East Lancashire Research 2008

East Lancashire Research 200

Carbon emission from urban passenger transportation in Beijing

Urban passenger transport significantly contributes to global greenhouse gas emissions, especially in developing countries owing to the rapid motorization, thus making it an important target for carbon reduction. This article established a method to estimate and analyze carbon emission from urban passenger transport including cars, rail transit, taxis and buses. The scope of research was defined based on car registration area, transport types and modes, the stages of rail transit energy consumption. The data availability and gathering were fully illustrated. A city level emission model for the aforementioned four modes of passenger transport was formulated, and parameters including emission factor of electricity and fuel efficiency were tailored according to local situations such as energy structure and field survey. The results reveal that the emission from Beijing’s urban passenger transport in 2012 stood at 15 million tonnes of CO2, of which 75.5% was from cars, whereas car trip sharing constitutes only 42.5% of the total residential trips. Bus travel, yielding 28.6 g CO2, is the most efficient mode of transport under the current situations in terms of per passenger kilometer (PKM) emission, whereas car or taxi trips emit more than 5 times that of bus trips. Although a decrease trend appears, Beijing still has potential for further carbon reduction in passenger transport field in contrast to other cities in developed countries. Development of rail transit and further limitation on cars could assist in reducing 4.39 million tonnes CO2 emission

Contributions from computational intelligence to healthcare data processing

80 p.The increasing ability to gather, store and process health care information, through the electronic health records and improved communication methods opens the door for new applications intended to improve health care in many different ways. Crucial to this evolution is the development of new computational intelligence tools, related to machine learning and statistics. In this thesis we have dealt with two case studies involving health data. The first is the monitoring of children with respiratory diseases in the pediatric intensive care unit of a hospital. The alarm detection is stated as a classification problem predicting the triage selected by the nurse or medical doctor. The second is the prediction of readmissions leading to hospitalization in an emergency department of a hospital. Both problems have great impact in economic and personal well being. We have tackled them with a rigorous methodological approach, obtaining results that may lead to a real life implementation. We have taken special care in the treatment of the data imbalance. Finally we make propositions to bring these techniques to the clinical environment

Who pays for health care in Ghana?

<p>Abstract</p> <p>Background</p> <p>Financial protection against the cost of unforeseen ill health has become a global concern as expressed in the 2005 World Health Assembly <it>resolution </it>(WHA58.33), which urges its member states to "plan the transition to universal coverage of their citizens". An important element of financial risk protection is to distribute health care financing fairly in relation to ability to pay. The distribution of health care financing burden across socio-economic groups has been estimated for European countries, the USA and Asia. Until recently there was no such analysis in Africa and this paper seeks to contribute to filling this gap. It presents the first comprehensive analysis of the distribution of health care financing in relation to ability to pay in Ghana.</p> <p>Methods</p> <p>Secondary data from the Ghana Living Standard Survey (GLSS) 2005/2006 were used. This was triangulated with data from the Ministry of Finance and other relevant sources, and further complemented with primary household data collected in six districts. We implored standard methodologies (including Kakwani index and test for dominance) for assessing progressivity in health care financing in this paper.</p> <p>Results</p> <p>Ghana's health care financing system is generally progressive. The progressivity of health financing is driven largely by the overall progressivity of taxes, which account for close to 50% of health care funding. The national health insurance (NHI) levy (part of VAT) is mildly progressive and formal sector NHI payroll deductions are also progressive. However, informal sector NHI contributions were found to be regressive. Out-of-pocket payments, which account for 45% of funding, are regressive form of health payment to households.</p> <p>Conclusion</p> <p>For Ghana to attain adequate financial risk protection and ultimately achieve universal coverage, it needs to extend pre-payment cover to all in the informal sector, possibly through funding their contributions entirely from tax, and address other issues affecting the expansion of the National Health Insurance. Furthermore, the pre-payment funding pool for health care needs to grow so budgetary allocation to the health sector can be enhanced.</p

건설업 고위험 직종별 유해인자 노출 평가

학위논문 (박사) -- 서울대학교 대학원 : 보건대학원 보건학과, 2021. 2. 윤충식.건설업은 노동의존도가 매우 높은 산업으로, 건설업 근로자는 작업과정 중 다양한 유해인자에 복합적으로 노출되는 것으로 알려져 있다. 그러나, 작업장 이동이 많고, 단위작업 장소에서의 작업시간이 짧으며, 작업환경이 지속적으로 변화하는 특성으로 인해 노출되는 유해인자의 농도수준 및 특성에 대해서는 잘 알려져 있지 못하다. 이번 연구는 건설업 근로자의 직종별 노출 유해인자를 조사하고, 직업성 암 등 건강장해 발생 위험이 높은 직종(지하 굴착공, 콘크리트 마감공, 방수도장공, 용접공, 아스팔트 도로포장공)을 우선대상으로 선정하여 발암성 물질을 중심으로 유해인자 노출농도 수준 및 농도에 영향을 주는 환경변수 등을 평가하였다. 먼저, 탑다운 공법을 적용한 주상복합 건축물 신축현장 4개소의 지하 굴착작업 중 발생하는 원소탄소 (elemental carbon, EC), 다환방향족탄화수소 (polycyclic aromatic hydrocarbons, PAHs), 호흡성 산화규소 결정체 (respirable crystalline silica, RCS)의 노출농도 수준을 살펴보았다. EC 농도는 권고기준인 20 ㎍/㎥을 초과하는 시료가 전체의 약 50 %를 차지하였다. RCS의 기하평균(geometric mean, GM)농도는 노출기준인 0.05 ㎎/㎥의 1.5배를 초과하였다. 주요 환경변수로 암석지반, 높은 장비 밀집도, 발파작업, 환기조건이 나쁠수록 EC 및 RCS 농도수준이 높은 것을 알 수 있었다. 특히, 작업환경개선이 가장 우선 적용되어야할 대상은 상부가 밀폐된 경암 지반의 현장이었다. 지하 굴착작업장에서 디젤엔진배출물 및 산화규소 노출을 최소화하기 위한 노력으로 작업장 상부를 최대한 개방하여 충분한 환기를 실시하고, 살수를 통한 습식작업환경 조성, 노후 차량의 교체, 차량의 정기 점검 및 유지 보수, 및 저유황유 사용 등의 개선조치가 필요하다. 아파트 건설현장 8개소의 콘크리트 마감작업(할석, 그라인딩, 미장작업)에 대한 RCS 노출 농도를 평가하였다. RCS의 GM 농도는 콘크리트 그라인딩 작업에서 2.06 ㎎/㎥, 할석작업에서 0.12 ㎎/㎥로 노출기준인 0.05 ㎎/㎥의 각 40배 및 2배를 초과하였다. 콘크리트 그라인딩 작업 중 RCS 농도는 계단실 (4.18 ㎎/㎥), 세대내부 (2.76 ㎎/㎥), 지하작업장 (1.30 ㎎/㎥) 등 작업 공간 체적이 작을수록 농도수준이 높음을 알 수 있었다. 작업환경개선이 가장 우선 적용되어야할 대상은 작업공간이 작은 장소에서의 콘크리트 연마작업이었다. 건설현장 콘크리트 마감 작업 중에서 RCS 노출을 저감하기 위해서는 환기캡을 적용한 국소배기장치의 사용, 습식작업 등의 작업환경개선이 시급하며, 공학적 개선과 함께 호흡보호구의 철저한 지급․착용 및 밀착도 검사, 주기적인 건강검진 모니터링이 필요하다. 건설현장 도장작업자에 대한 휘발성 유기화합물(volatile organic compounds, VOCs) 노출수준을 살펴보기 위해 8개 건설현장에서 우레탄 방수작업에 대해 평가하였다. VOCs의 혼합물질 노출지수(exposure index, EI; 노출기준=1)의 GM은 국내 노출기준(Korea occupational exposure limits, KOEL)의 약 78%수준이었으며, KOEL을 초과하는 시료가 전체시료의 약 38.6%로 작업환경관리가 요구되는 수준이다. 더욱이, EI를 미국 ACGIH TLVs에 따라 산출하면, EI의 GM이 1.84로 KOEL의 약 2배 수준으로 매우 높았다. 혼합물질 평가에 가장 큰 영향을 미치는 물질은 톨루엔이었다. 작업별로는 실내 우레탄 프라이머 도포 작업에서 노출농도가 가장 높았다. 건설현장 도장작업자의 건강관리를 위해 도료 구성성분 중 발암성 물질과 생식독성물질은 최대한 유해성이 낮은 물질로 대체하고, 농도수준에 따라 적절한 보호계수를 갖는 개인보호구의 지급 및 착용 및 지속적인 노출평가와 건강검진 실시결과에 대한 사후관리가 필요하다. 또한, 실내 작업의 경우는 환기장치를 가동하고 작업을 진행하여 유기화합물 노출을 최소화 하여야 한다. 건설현장 일반건축물 배관용접공, 화학플랜트 배관용접공, 철골용접공, 소각플랜트 보일러 제작 용접공, 금속마감용접공을 대상으로 용접흄 및 금속류에 대한 노출농도(GM) 수준을 살펴보았다. 용접흄의 농도는 일반건축물 배관공 (4.75 ㎎/㎥)> 철골용접공 (3.77 ㎎/㎥) > 보일러제작용접공 (1.38 ㎎/㎥)> 금속마감용접공 (0.78 ㎎/㎥) > 화학플랜트 배관용접공(0.71 ㎎/㎥) 순으로 높았다. 용접기법에 따른 용접흄 농도는 CO2용접 (2.08 ㎎/㎥) > 피복아크용접 (1.54 ㎎/㎥) > TIG용접 (0.70 ㎎/㎥) 순으로 높았고, 동일한 직종의 일반건축물 배관용접작업에서 지하공간 (7.75 ㎎/㎥)과 지상층 실내공간 (2.15 ㎎/㎥)의 용접흄 농도차이는 약 3.6배로 더욱 커서 작업장 환기조건이 용접흄 농도에 중요한 환경변수 임을 알 수 있었다. 용접작업 위험도가 높은 일반건축물의 배관용접과 철골용접작업, 지하공간에서의 용접작업, CO2 용접작업 등을 수행할 시에는 환기장치 사용과 호흡용 보호구 착용 등 철저한 작업환경관리와 작업 시 아크까지 일정거리 유지, 적정 용접전류 선택 등 용접흄 발생을 최소화할 수 있는 근로자 안전보건교육이 필요함을 알 수 있었다. 아스팔트 도로포장을 실시하는 건설현장 3개소에서 아스팔트 흄(벤젠추출법) 및 다환방향족탄화수소(PAHs) 농도를 직종별로 살펴보았다. 아스팔트 흄(벤젠추출법) 농도의 직종별 차이를 살펴보면, 포장특공 (42.32 ㎍/㎥), 포설장비 운전원 (41.57 ㎍/㎥), 머캐덤 운전원 (31.9 ㎍/㎥), 타이어 운전원 (30.31 ㎍/㎥) 순으로 높았다. 아스팔트 흄은 노출기준 500 ㎍/㎥의 약 10% 수준으로 매우 낮았으나, PAHs의 경우, 대기환경 농도와 비교하면 수백배 높은 농도수준이었으며, 도료, 타르 제조업 등 타 업종과 비교하여 총 PAHs 농도는 낮았으나, 세부물질 중 Benzo(a)pyrene 농도가 상대적으로 높은 특성이 있었다. 또한 아스팔트 도로포장 작업의 경우 주변 건물 및 풍속 등 환경변수에 따른 농도변이가 매우 큰 특성이 있으므로 다양한 작업현장을 대상으로 추가적인 노출평가 연구가 요구된다. 이번 연구를 통해 그동안 잘 알려져 있지 못한 건설업 근로자의 유해인자 및 노출농도 수준을 확인할 수 있었다. 직종별 노출평가 결과에서 대부분의 작업이 노출기준을 초과하여 직업성 암 등 건강장해 발생 위험이 높은 수준임을 확인할 수 있었다. 베이시안(Bayesian) 통계기법을 활용한 평가자료의 95% 상위값이 노출기준을 초과할 확률을 살펴보면, 지하굴착공의 원소탄소 및 산화규소(결정체), 콘크리트 할석, 그라인딩공의 산화규소(결정체), 도장공의 휘발성 유기화합물, 일반건축물 배관용접공 및 철골용접공의 용접흄 농도는 약 5% 이상의 작업자는 노출기준을 초과할 우려가 있음으로 평가되어 작업환경개선이 요구되었다. 또한, 건설현장의 특성상 평가그룹별 농도의 변이수준이 높음을 확인하였으며, 향후 작업환경측정 시 변이를 고려한 적정 시료수, 반복측정 및 유사노출그룹 선정과 추정 상한치 등을 통한 위험수준 평가 적용이 필요함을 알 수 있었다. 평가농도에 영향을 미치는 주요 환경변수는 작업장의 환기조건, 건축재료, 작업방식 등임을 확인하였으며, 직종별 특성에 맞는 지속적인 작업환경개선 노력과 설계단계에서부터 유해인자 노출을 감소시킬 수 있는 공법의 도입 등이 필요하다. 또한, 향후 건설업 특화된 작업환경측정 및 건강관리제도의 개선과 지속적인 노출평가 연구가 요구된다. 이번 연구결과는 건설노동자의 업무상 질병 역학조사 시, 노출농도 예측을 위한 자료로 활용가능하며, 연구결과를 통해 도출된 농도에 영향을 주는 주요 환경변수 및 개선방안에 따라 건설현장 작업환경개선에도 기여할 수 있을 것으로 기대된다.The construction industry is highly dependent upon human labor compared to other industries. Construction workers are exposed to various hazardous substances simultaneously. However, little is known about the exposure level of hazardous substances due to the characteristics of frequent workplace shifts, changes in the working environment, and the multi-level subcontractor structure. This study was aimed at (a) identifying the exposure hazards of construction workers, (b) conducting an exposure assessment of carcinogenic substances for high-risk construction workers (excavation workers, concrete finishers, waterproof painters, welders, and asphalt road pavers), and (c) determining the variables most affecting hazardous substances concentrations and work environment improvement methods for construction workers. Identification of the exposure hazards among construction workers by job type The exposure hazards of 27 construction jobs were identified and summarized through a literature review and walk-through survey. Construction workers were exposed to noise, vibrations, ultraviolet rays, solar radiation, various types of dust (cement, concrete, wood, glass wool, mineral, and gypsum), and chemicals such as crystalline silica, diesel engine exhaust, asphalt fumes, asbestos, lead, chromium, epoxy/urethane, isocyanate, carbon monoxide, metal fumes, and volatile organic compounds. The most frequently exposed seven hazards were noise, vibrations, solar radiation, crystalline silica, cement/concrete dust, metal fumes, and volatile organic compounds. As for the exposure characteristics, construction workers were exposed to various hazards simultaneously, including carcinogenic substances and those with adverse reproductive effects. Among construction workers, the job types with the highest risk of exposure to carcinogens, and in which occupational cancer has been reported, were excavation workers, concrete finishers, painters, welders, and asphalt road pavers. Exposure assessment of elemental carbon, polycyclic aromatic hydrocarbons and respirable crystalline silica among underground excavation workers The concentration of elemental carbon (EC), organic carbon (OC), and total carbon (TC) (n = 105), polycyclic aromatic hydrocarbons (PAHs) (n = 50), respirable dust (RD) (n = 34) and respirable crystalline silica (RCS) (n=34) were evaluated inside and outside the excavator at an underground excavation worksite in four different construction sites. EC, OC, and TC were collected on a quartz filter and analyzed using the thermal optical transmittance method. PAHs were collected on a polytetrafluoroethylene (PTFE) filter with an XAD-2 tube and analyzed using liquid chromatography with a fluorescence detector. RD and RCS were collected on a polyvinyl chloride (PVC) filter with aluminum cyclone and analyzed using Fourier-transform infrared spectroscopy. The geometric mean (GM) of respirable EC, OC, TC, total PAHs, RD, and RCS were 8.69 ㎍/㎥, 34.32 ㎍/㎥, 44.96 ㎍/㎥, 6.82 ㎍/㎥ 0.13 ㎎/㎥ and 0.02 ㎎/㎥ inside the excavator and 33.20 ㎍/㎥, 41.53 ㎍/㎥, 78.21 ㎍/㎥, 3.93 ㎍/㎥, 0.9 ㎎/㎥, and 0.08 ㎎/㎥, respectively, outside the excavator at the underground excavation worksite. The EC concentrations exceeded the recommended exposure limits as of 20 ㎍/㎥ accounted for about 50% of the total samples, and the GM of RCS outside the excavator exceeded 1.5 times the occupational exposure limit (OEL) of 0.05 ㎎/㎥. The worksites with hard rock ground, higher vehicle density, blasting work, and enclosed environments had higher worker exposure to EC than the other sites (p < 0.05). The most influential variables were the ground type and ventilation condition. In particular, in high-risk excavations in rocky ground and enclosed environments, more effort is needed to improve the working environment by introducing water-spraying facilities and supplying fresh air and ventilation. Furthermore, the replacement of old vehicles, regular vehicle maintenance, and the use of low sulfur oil is suggested. Exposure assessment of RD and RCS among concrete finishing workers The concentration of RD and RCS (n = 129) and the size distribution of the particles (n = 6) using a cascade impactor were evaluated at eight apartment complex construction sites. RD and RCS were collected on PVC filters with aluminum cyclone and analyzed using Fourier-transform infrared spectroscopy. The GM of RCS in concrete grinding (2.06 ㎎/㎥) and concrete chipping (0.12 ㎎/㎥) exceeded 40 times and two times the OEL of 0.05 ㎎/㎥, respectively. The highest concentration of RCS in concrete grinding work was found in the staircases (4.18 ㎎/㎥), followed by the inside walls of the apartment units (2.76 ㎎/㎥), underground parking lots (1.30 ㎎/㎥), and exterior walls (0.89 ㎎/㎥). The GM of RD from concrete chipping, grinding, and plastering was 1.78 ㎎/㎥, 49.96 ㎎/㎥, and 0.37 ㎎/㎥, respectively. The mass fraction of inhalable, thoracic, and respirable crystalline silica from concrete chipping was 73.9%, 40.2%, and 17.9% and 76.0%, 46.3%, and 19.7% from concrete grinding, respectively. The highest RCS concentration was reported in concrete grinding tasks, and the smaller the space, the higher the concentration. The most influential variables were the type of task and size of the workplace. During concrete grinding work, multiple control methods must apply to improve the work environment such as local exhaust ventilation system or water-spraying facilities targeting fine-dust (less than 10 ㎛), simultaneously with the application of high-efficiency respirators. Exposure assessment of total volatile organic compounds among construction waterproofing painters The concentration of total volatile organic compounds (TVOCs) in waterproof painting work was monitored at eight construction sites using an organic vapor monitor (n = 88). Gas chromatography with flame ionization detection was used to identify and quantify the individual organic chemicals. The GM of the TVOCs exposure index (EI, OEL = 1) by work type was the highest when primer roller painting (1.2), followed by urethane resin spread painting (0.85), workplace area samples (0.83), mixing paint (0.53), and assisting the painter (0.35). The GM of the TVOCs EI by workplace was highest in the bathroom (1.4), followed by the swimming pool (1.37), pilot floor (0.89), ground parking lot (0.82), and rooftop (0.57). From this study, the GM of the TVOCs EI was about 78% the level of the Korea OEL (KOEL), and 38.6% of the total samples exceeded the OEL. However, when calculating the EI, according to the ACGIH-TLVs, the GM of TVOCs EI was 1.84, which was more than twice as high as when the KOEL was applied. The highest TVOCs concentration was reported in primer painting tasks in an indoor workplace. The most influential variables were the work environment (indoor vs. outdoor) and the solvent content of the paint. Indoor painting work must apply a ventilation system, and personal protective devices with an appropriate protection factor, and efforts are needed to substitute paints with fewer toxic substances. Exposure assessment of welding fumes and metals among construction welders. The concentration of welding fumes and metals (n = 206) was evaluated using PVC filters with gravimetric analysis and inductively coupled plasma at eight construction sites, including three apartments, two offices, two plant buildings, and one hospital. Among the different welding tasks, the welding fume exposure was the highest for general building pipefitters (4.75 ㎎/㎥), followed by ironworkers (3.77 ㎎/㎥), boilermakers (1.38 ㎎/㎥), metal finishing welders (0.78 ㎎/㎥), and chemical pipefitters (0.71 ㎎/㎥). Among the different welding techniques, welding fume concentrations were highest when CO2 welding (2.08 ㎎/m3), followed by shield metal arc welding (SMAW, 1.54 ㎎/㎥), and tungsten inert gas welding (TIG, 0.70 ㎎/㎥). Among the different workplaces, welding fume concentrations were highest at the underground workplace (7.75 ㎎/㎥) followed by the ground level workplace (2.15 ㎎/㎥). In particular, high-risk welding tasks as general building pipefitters and ironworkers, underground welding work, and CO2 welding techniques require more attention to occupational health management, including air supply and exhaust systems, and worker training on welding fume characteristics by welding base material and welding methods. Exposure assessment of asphalt fumes and PAHs among road pavers. The concentration of asphalt fume (benzene soluble, n = 42) and PAHs (n = 41) was analyzed at three asphalt road pavement construction sites. Asphalt fumes were sampled using PTFE filters. PAHs were sampled using an XAD-2 tube with a glass fiber filter and analyzed using liquid chromatography with fluorescence detection. The exposure to asphalt fumes as benzene soluble aerosols was highest to road pavers (42.32 ㎍/㎥), followed by paver finisher operators (41.57 ㎍/㎥), macadam roller operators (31.9 ㎍/㎥), and tire roller operators (30.31 ㎍/㎥). The most influential variables were the asphalt temperature, the installation of hopper ventilation systems in the paver finisher, and the surrounding building conditions. The benzo(a)pyrene equivalent concentration (BaPeq) was 2.81 for paver finisher operators, 2.07 for road pavers, 0.41 for tire roller operators, and 0.25 for macadam roller operators. The BaPeq values for asphalt road paving workers was higher than that for workers in other PAHs exposure occupations even though at lower total PAHs concentrations. This study confirmed the carcinogenic exposure hazards of asphalt road paving workers. This study identified hazardous substance exposure among construction workers. Construction workers were exposed to various hazards simultaneously. The exposure assessment of construction workers demonstrated that excavation workers (respirable EC and RCS), concrete finishers (RD and RCS), construction painters (TVOCs), and welders (welding fume for pipefitters, boilermakers, and ironworkers) had possibilities of at least more than 5% of the exposure evaluation samples exceeded the exposure limits and their work environment was evaluated as poorly controlled. Efforts are needed to eliminate hazards during design, substitute with less toxic materials and processes, remove workers from hazardous work, select appropriate equipment, reduce the time exposed to hazards, wear protective equipment and conduct regular health checks and concentration monitoring. The characteristics of the exposure in the construction industry showed large day-to-day variations due to the mobile and varied tasks. Therefore, in the future, it is necessary to apply weights for variability when evaluating the work environment monitoring results for construction workers and manage the hazard concentration within the exposure limits. These variations should be applied to the decisions regarding the appropriate sample number, homogeneous exposure groups and the estimated upper limit of concentrations for risk assessment. This research data can be used to estimate the hazards exposure levels of construction workers when adjudicating occupational disease in health compensation insurance claims, and can contribute to improving the work environment at construction sites.1. Introduction 1 1.1. Characteristics of construction workers 1 1.2. Construction job types and hazards 3 1.3. High-risk construction workers 9 1.4. Research scope and overview 17 1.5. Objectives 19 2. Exposure Assessment of Elemental Carbon, Polycyclic Aromatic Hydrocarbons and Respirable Crystalline Silica among Underground Excavation Workers 20 2.1. Introduction 20 2.2. Materials and methods 23 2.3. Results 29 2.4. Discussion 46 2.5. Conclusions 53 3. Exposure Assessment of Respirable Dust and Crystalline Silica among Concrete Finishing Workers 54 3.1. Introduction 54 3.2. Materials and methods 56 3.3. Results 62 3.4. Discussion 74 3.5. Conclusions 77 4. Exposure Assessment of Total Volatile Organic Compounds among Construction Painters 84 4.1. Introduction 84 4.2. Materials and methods 85 4.3. Results 90 4.4. Discussion 100 4.5. Conclusions 103 5. Exposure Assessment of Welding Fumes and Metals among Construction Welders 104 5.1. Introduction 104 5.2. Materials and methods 106 5.3. Results 109 5.4. Discussion 129 5.5. Conclusions 133 6. Exposure Assessment of Asphalt Fumes and Polycyclic Aromatic Hydrocarbons among Road Pavers 134 6.1. Introduction 134 6.2. Materials and methods 136 6.3. Results 139 6.4. Discussion 147 6.5. Conclusions 151 7. Summary of conclusions 152 References 167 Appendix 185 국문초록 219Docto