Since 1974, the urban subway has been used as a major form of public transportation in Seoul, Korea. The air quality in the subway environment depends on the introduction of air pollutants from roadway air and its generation is caused by subway operation in the tunnel. In the subway tunnel, PM10 concentration was monitored from March 8 to 15, 2018 and from March 26 to 28, 2018, and compared with concentrations that are routinely monitored at the subway concourse and the nearest roadside air quality monitoring station (RAQMS). Overall PM10 concentration at the concourse was similar to that of the RAQMS. However, PM10 concentration in the tunnel was significantly higher than those of the subway concourse and RAQMS, and showed distinct diurnal variation caused by train operation. The dominant peak concentrations were highly correlated with the number of train operations per hour. The minimum PM10 concentration was observed between 2 am to 5 am when the train was not operated. This was similar to that of the RAQMS. Although the diurnal variation of the PM10 concentration at the concourse is not significant, the overall trend is similar to that in the tunnel.

The urban expressway is widely used to avoid traffic jams in highly-populated urban areas. However, vehicle exhaust can be easily transported to the neighboring area including residential buildings. In this study, we investigated the transport and penetration of vehicle exhaust into the nearby high-story residential building. Black carbon (BC) and lung deposited surface area (LDSA) concentrations were monitored every 1 min using an aethalometer (AE51, Magee) and a nanoparticle aerosol monitor (AeroTrak 9000, TSI), respectively. For comparison, the measurement was carried out in both the living room and balcony of the apartment from January 18 to January 25, 2016. The CO2 concentration indicated the presence of residents in the living room and transport of vehicle exhaust from the roadway in the balcony. Its diurnal variation showed a significant difference between weekdays and the weekend, implying the different time activity of residents and traffic volume. BC and LDSA concentrations were 1.4±1.5 μg/m3 and 53.9±45.0 μm2/cm3 indoors, and 1.9±1.0 μg/m3, 76.2±34.5 μm2/cm3 outdoors, respectively. The indoor to outdoor concentration ratios range from 0.6 to 0.8, indicating the significant influence of outdoor vehicle exhaust. The highest concentrations of BC and LDSA were observed in the morning rush hours, except for those indoors during the weekend. In particular, the outdoor effect is significant during the morning rush hours. Indoor air quality management is urgently needed for residents living near the urban expressway.

Many air purifiers have been developed and released with increasing PM. In generally, the performance of air purifiers has been evaluated in the environment chamber by relevant standards. However, as there is a lack of information about air cleaning performance of air purifier in the living area, consumers have difficulty with product selection. In this study, five air purifiers were tested in apartments with different structures. In order to examine the effect of air purifiers, we assumed 3 cases such as inflow of pollutants from outdoors by ventilation, smoking patterns of residents, and cooking methods (e.g., frying fish). The evaluation results showed that the efficiency of air purifier products D and B of the 3-stage configuration (pre-filter + HEPA filter + activity carbon) was the best in most experiments. In the case of the ionizer type E product, the efficiency was very low and, at times, had increased the particulate matter indoors. Considering the cost-performance ratio, it is most reasonable to use an air purifier comprising a pre-filter and a HEPA filter without an additional configuration.

The urban railway system is a convenient public transportation system, as it carries many people without increasing traffic congestion. However, air quality in urban railway environments is worse than ambient air quality due to the internal location of the source of air pollutants and the isolated space. In this paper, characteristics of particulate matter (PM) pollution in urban railway environments are described from the perspective of diurnal variation, chemical composition and source apportionment of PM. PM concentrations in concourse, platform, passenger cabin, and tunnel are summarized through an analysis of 34 journal articles published in Korea and overseas. This information will be helpful in developing effective policies to reduce PM pollution in urban railway environments.

While the air quality of public facilities such as daycare centers is managed by law, the management of air quality in residential buildings is not mandatory. For this reason, air quality in an apartments has not been well surveyed. In this study, we investigated the influence of cooking and ventilation on the indoor air quality in an apartment. Continuous measurements were performed using real-time monitoring instruments from June 9 to 17, 2014 in Seoul, Korea. A CO2 meter was used to measure CO2 concentration and temperature. A portable aerosol spectrometer (0.25-32 μm), a nanoparticle aerosol monitor (10-1,000 nm), and an aethalometer (total suspended particulate, black carbon) were also used. During the measurement period, ventilation and cooking activities were observed 8 and 10 times, respectively. In 5 of the observed cases, both activities were done simultaneously. During the ventilation, CO2 concentration and temperature were decreased; however, particle concentrations were increased. When cooking was done, particle concentration was increased in some cases; however, CO2 concentration and temperature were unchanged. Combined cased CO2 concentration and temperature were decreased and particle concentrations were increased.

The number of children who use day-care centers is increasing. Most indoor air quality (IAQ) management has been based on daily average pollutant concentrations measured once a year. A more comprehensive management of IAQ is needed to protect children’s health from air pollutants in day-care centers. In this study, we investigated the weekly variation of air pollutant concentrations in a nursing room of a day-care center located at the roadside for a week in June of 2014. Average concentrations of CO2, PM10, black carbon, and total surface area of lungdeposited particles during nursing time of the day-care center were 510 ppm, 27.8 μg/m3, 1.87 μg/m3, and 30.6 μm2/cm3, respectively, with a similar diurnal pattern shown on weekdays.

Since people spend more than 85% of their time indoors, understanding indoor aerosol behavior is important in order to protect human health against aerosol exposure. In this article, exposure, behavior, and control technologies for indoor aerosols are addressed. Previous studies conducted in Korea during the period from 2004 to 2016 were reviewed. Most studies were focused on field surveys of PM10 concentration in public facilities regulated by law. More fundamental studies are needed in order to control indoor aerosols effectively due to the fact that Korea has different building structures and lifestyles compared with western countries.

A single-stage electrostatic precipitator (ESP) was evaluated in terms of its performance in removing dust in subway tunnels. A wire-to-plate type ESP was tested in a small-scale wind tunnel. The effects of wire-to-wire spacing (2040 mm) and the material connecting wire-to-wire on the performance of ESP were investigated, with varying applied voltage and airflow velocity. A narrower wire-to-wire spacing showed higher collection efficiency at the same applied voltage. Lower electrical resistivity of material connecting wire to wire was more effective. Ozone generation in subway tunnel applications was insignificant.

In this study, we investigated the concentrations of PM10 and CO2 in public transportation vehicles (express bus, train, KTX, and subway) reported by previous indoor air quality (IAQ) surveys carried out from 2005 to 2013 in Korea. The number of valid data for PM10 was 566 and for CO2 was 579, and all data were classified according to whether it was collected during rush-hour or non rush-hour. PM10 and CO2 concentrations in subway cabin during the rush-hour were 1.3 and 1.45 times higher, respectively, than those of non rush-hour (p<0.05) in terms of geometric mean value. PM10 and CO2 concentration of express bus and train during the rush-hour also were 1.23 times higher than those of non rush-hour with relatively weak correlations (p=0.246). Among all PM10 concentrations, 16.9% and 3.8% of PM10 concentrations exceeded the IAQ guidelines (200 μg/m3 for non-rush hour and 250 μg/m3 for rush-hour), respectively. In terms of CO2 concentrations, 10.5% and 3.0% of them exceeded the IAQ guidelines (2,500 ppm for non rush-hour and 3,000 ppm for rush-hour), respectively. As a result, concentrations of PM10 and CO2 were estimated to be dominantly influenced by the operation characteristics of public transportation, such as degree of congestion and type of vehicle. In order to improve the IAQ of public transportation vehicles, specific air purification and ventilation systems are needed, depending on the characteristics of public transportation vehicles.

It is well known that smoking generates harmful air pollutants. With smoking in buildings as well as in the streets prohibited, the need for smoking rooms has emerged. In this study, particle and CO contamination in a 63.6 m3 smoking room was experimentally investigated using Korean tobacco. Tobacco smoking was artificially simulated using a smoking machine. The number and size distribution of particles ranging from 10-420 nm and 0.25-32 μm were measured using a Nanoscan (TSI model 3910) and a portable aerosol spectrometer (Grimm model 1.109), respectively. CO concentration was also monitored using an IAQ monitor (Graywolf IAQ-Xtra 610). Four tobaccos were simultaneously smoked in each experiment, and the experiment was repeated four times. Maximum CO concentrations of 7-10 ppm were observed and high concentrations of particles (176,000-1,115,000 particles/cm3 for 10-420 nm, 3,700-5,200 particles/cm3 for 0.25-32 μm) were also monitored. The dominant size of tobacco particles was about 100 nm in diameter.

Day-care center is one of living micro-environments for children. In urban area, day-care centers may be influencedby air pollutants emitted from the vehicle exhaust. In this work, diurnal variation of major pollutants and effectof outdoor air on indoor air quality were investigated using real-time instruments for a day-care center locatednear the heavy road. 48-h continuous monitoring at both indoor and outdoor were made in summer. The day-care center equipped with ceiling system air-conditioners was operated from 7:30 a.m. to 19:30 p.m. Indoor CO₂concentration responded greatly to the human activity. Indoor NO₂ concentration shows a big difference betweendaytime and nighttime, implying that outdoor NO₂ may penetrate into the indoor through opening of doors orwindows during the daytime. Indoor to outdoor concentration ratio of submicron particle surface area is <1 dueto the penetration of outdoor ultrafine particles.

Airborne bacteria, fungi, and viruses are known to have adverse effects on human health. Various antimicrobial agents have been used to prohibit the growth of microorganisms on the surfaces of air filter media. In this study, nano-sized silver and copper particles were tested for their antifungal effects on indoor fungi, Cladosporium cladosporioides and Aspergillus versicolor. The growth circle of the fungi was observed on a solid agar plate containing the two nanoparticles. The nanoparticle concentration ranged from 0 to 500 μg/mL. The size of fungal growth circle seemed to decrease with increasing nanoparticle concentration in agar plates, indicating that silver and copper nanoparticles have antifungal properties against C. cladosporioides and A. versicolor.

Experiment on the thermal response of college-age Korean was conducted in a thermal environmental chamber during winter season. Eight environmental conditions composed of five air temperatures (18∼26℃) and two relative humidities (40, 60%) were selected. To investigate the uniformity of thermal environments, the spatial distributions and the temporal variations of thermal parameters were examined in the test chamber. Subjects of 7 females or 7 males were questioned in the chamber for three hours, where thermal and comfort sensations were surveyed every fifteen minutes. The repeatability and temporal variation of thermal response were discussed. The thermal sensation votes of subjects were compared with the predicted mean votes calculated from the thermal parameters and human parameters. The correlation between thermal sensation votes and comfort sensation votes of subjects were discussed.

Vehicle drivers are subject to be exposed to high concentrations of airborne pollutants emitted from vehicles on roads. To investigate the indoor air quality of vehicles on roads, black carbon (BC) was measured inside a passenger car commuting between the residential area in southern Seoul and the Korea Institute of Science and Technology (KIST) in northern Seoul using a portable aethalometer. When the vehicular windows were closed, the ventilation mode was set to fresh air mode (or circulation mode) for a total of thirteen runs made during May 2005. When the windows were open, the analysis was made with the system turned off (for twelve runs in October 2005). The BC concentration depended on such parameters as spatial location, time of day, and ventilation mode. The average BC concentration measured on non-express ways was higher than those measured on express ways, inside KIST, and nearby the residential area for most runs. On circulation mode, the average BC concentration was 5.9±1.7 ㎍/㎥ in the afternoon or evening, which was similar to a 24-hr average BC concentration for ambient air at 200 m apart from a road in Seoul. In the case of fresh air mode, the average BC concentrations measured in the morning rush hour, in the afternoon or evening, and after midnight were 22.8±3.4, 15.9±7.7, 3.7 ㎍/㎥, respectively. The average BC concentrations measured with the vehicular window open were 31.9±9.2, 19.4±5.9 ㎍/㎥, respectively in the morning rush hour and in the afternoon or evening. These measured values were higher than those measured with the windows closed. The average BC concentrations inside a passenger car with a fresh mode operation or open-window driving were significantly higher than a 24-hr average BC concentration measured at 200 m apart from a road in Seoul.

Activated carbon fiber (ACF) filters are widely used to remove volatile organic compounds (VOCs) in air cleaning devices. The performance of ACF filters could be enhanced combining adsorption process with photodegradation process. In this study, to investigate this enhancement effect, a duct-type reactor was made and TiO2 was i㎜obilized on a co㎜ercialized ACF filter. Benzene, toluene, and m-xylene (BTX) were chosen as target compounds. Removal experiments for BTX were done under different air velocity and upstream concentration conditions. The range of inlet concentration was 200～1,400 ppb and the air velocities were 0.4, 0.7 and 1.0 m/s. Adsorption by an ACF filter alone showed high removal efficiency of BTX, depending on the BTX species, the upstream concentration, and the air velocity. The combination of TiO2 and ACF filter significantly increased removal of benzene which was less removed than other pollutants by an ACF filter alone. It was found that the combination effect was small in removal test of toluene and m-xylene. Removal efficiency in the tested experimental conditions was decreased in order of toluene > m-xylene > benzene.

Thermal response of Korean college students was investigated in a thermal environmental chamber during summer season. Eight thermal conditions combined with four air temperatures (24, 26, 28, 30℃) and three relative humidities (40, 60, 80%) were selected. Subjects of seven females and seven males were questioned in the chamber for three hours, where thermal and comfort sensations were surveyed every fifteen minutes. During the period of thermal response experiment, four thermal parameters of air temperature, relative humidity, air velocity, and globe temperature were monitored in the test chamber. The repeatability and temporal variation of thermal response were discussed. The thermal sensation vote (TSV) of females is in good agreement with the predicted mean vote (PMV) calculated from the thermal parameters and human parameters. However, the TSV of male shows a slight discrepancy with the PMV. The neutral points of both female and male are very close to 0.18 of PMV, indicating that college-age Korean like to a slight warm environment compared with Western people. The thermal sensation vote of subjects is well correlated with the comfort sensation vote.

The antimicrobial activity of metallic nanoparticles against bacteria was investigated. Silver, copper, and titania nanoparticles were tested. The bacteria species E. coli and B. subtilis were selected as models for Gram-negative and Gram-positive bacteria, respectively. Bacteriological tests were performed in Luria-Bertani (LB) medium or Nutrient (NT) medium on solid agar plates containing different concentrations of nanoparticles in the range of 0 to 150 μg/mL. Silver and copper nanoparticles were shown to be an effective bactericide. However, titania nanoparticles were found to be ineffective as an antimicrobial agent. It appears that E. coli cells are more sensitive to the copper nanoparticles than to silver nanoparticles and B. subtilis cells have similar sensitivity against both copper and silver nanoparticles.

황해지역에서 생성 및 배출되는 자연황화합물의 규모를 정량적으로 구명하기 위한 노력의 일환으로, 본 연구진은 황해에 위치한 덕적도를 주 측정점으로 설정하고 대기 중에 존재하는 DMS의 농도분포를 1999년 4월과 9월 2차례의 집중측정기간을 통해 측정하였다. 그리고 이에 덧붙여 1999년 6월에는 청도-인천간 해상실험을 통해 황해상의 DMS 농도를 측정하였다. 덕적도를 중심으로 시행한 양 측정기간 중 DMS의 농도값은 4월 측정의 경우 평균과 표준오차가 24.0±40.5 pptv(n=40)인데 반해 9월 측정의 경우 61.1±37.9 pptv(n=35)로 나타났다. 그리고 선상실험에서 측정한 DMS 값은 대체로 배경농도에 가까운 낮은 농도범위를 갖는 것으로 밝혀졌다. DMS의 농도분포는 일반적으로 불규칙한 양상을 보였지만, 주변 기상인자의 변화경향과 유사하게 변화하는 것으로 나타났다. 본문에서는 이러한 연구결과와 기존의 연구결과 등을 연계하여 잠정적인 연간 배출량규모를 4Gg 대로 추정하였다. 이러한 배출규모는 과거 제주지역 등을 중심으로 측정한 결과에 비해 상대적으로 낮은 수치인데, 시간적 및 공간적으로 대표성이 강한 보다 객관적인 배출량을 산정하기 위해서는 추가적인 측정 자료의 축적이 요구된다.

With the development of nanotechnology, nanomaterials are used in various fields. Therefore, the interest regarding the safety of nanomaterial use is increasing and much effort is diverted toward establishment of exposure assessment and management methods. Occupational exposure limits (OELs) are effectively used to protect the health of workers in various industrial workplaces. This study aimed to propose an OEL for domestic multi-walled carbon nanotubes (MWCNTs) based on animal inhalation toxicity test. Basic procedure for development of OELs was examined. For OEL estimation, epidemiological study and quantitative risk assessment are generally performed based on toxicity data. In addition, inhalation toxicity data-based no observed adverse effect level (NOAEL) and benchmark dose (BMD) are estimated to obtain the OEL. Three different estimation processes (NEDO in Japan, NIOSH in USA, and Baytubes in Germany) of OELs for carbon nanotubes (CNTs) were intensively reviewed. From the rat inhalation toxicity test for MWCNTs manufactured in Korea, a NOAEL of 0.98 mg/㎥ was derived. Using the simple equation for estimation of OEL suggested by NEDO, the OEL of 142 μg/㎥ was estimated for the MWCNT manufacturing workplace. Here, we used test rat and Korean human data and adopted 36 as an uncertainty factor. The OEL for MWCNT estimated in this work is higher than those (2-80 μg/㎥) suggested by previous investigators. It may be greatly caused by different physicochemical properties of MWCNT and their dispersion method and test rat data. For setting of regulatory OELs in CNT workplaces, further epidemiological studies in addition to animal studies are needed. More advanced technical methods such as CNT dispersion in air and liquid should be also developed.