In present study, the temporal characteristics of nine selected volatile organic compounds (VOCs), including four alcohol, 2 aldehyde, and 3 ketone compounds, in high-stories urban apartments over a 2-y period were investigated. The indoor VOC concentrations had generally a decreasing trend over the 2-y follow-up period. For examples, the 2E1H indoor concentration decreased from 10.8 ㎍/m3 for the first two months to 5.1 ㎍/m3 for the last two months. In addition, the DCA and ACT indoor concentrations decreased from 5.0 and 14 ㎍/m3 for the first two months to 2.2 and 6.4 ㎍/m3, respectively, for the last two months. The indoor-to outdoor concentration ratios over the 2-y period were much greater than 1, indicating that indoor VOC concentrations were higher than the outdoor VOC concentrations. Similar to those of the individual VOCs, the indoorto- outdoor concentration ratios of all three VOC groups were higher than 1 over the 2-y follow-up period, suggesting higher indoor concentrations of the three VOC groups than outdoor concentrations. In consistence with the results of VOC indoor concentrations, the VOC emission rates decreased gradually as time passed, due to the decreased VOC emission strengths of indoor sources. Finally, there was an initial sharp decrease in the indoor VOC concentrations followed by a slower decrease, indicating a multi-exponential decay model for the target VOCs, which was demonstrated by comparison of the residuals and the adjusted coefficient of determination associated with the one and two-exponential fits of each data set.

The current study evaluated the technical feasibility of the application of titanium dioxide (TiO2) photocatalytic air cleaners for the disinfection of bioaerosols present in indoor air. The evaluation included both laboratory and field tests and the tests of hydraulic diameter (HD) and lamp type (LT). Disinfection efficiency of photocatalytic oxidation (PCO) technique was estimated by survival ratio of bacteria or fungi calculated from the number of viable cells which form colonies on the nutrient agar plates. It was suggested that the reactor coating with TiO2 did not enhance the adsorption of bioaerosols, and that the UV irradiation has certain extent of disinfection efficiency. The disinfection efficiency increased as HD decreased, most likely due to the decrease in the light intensity since the distance of the catalyst from the light source increased when increasing the HD. It was further suggested that the mass transfer effects were not as important as the light intensity effects on the PCO disinfection efficiency of bioaerosols. Germicidal lamp was superior to the black lamp for the disinfection of airborne bacteria and fungi, which is supported by the finding that the disinfection efficiencies were higher when the germicidal lamp was used compared to the black lamp in the laboratory test. These findings, combined with operational attributes such as a low pressure drop across the reactor and ambient temperature operation, can make the PCO reactor a possible tool in the effort to improve indoor bioaerosol levels.

Present study was designed to characterize the concentrations of major roadside air pollutants in Daegu and to compare with those of Seoul and Busan. Evaluated were the exceedance frequence of mean concentrations of target compounds(CO, NO2, O3, PM10, SO2) and the relationship for time variation. Two air pollution monitoring stations(one roadside station and one residential station) in Daegu were selected for this study. In addition, one roadside monitoring station from each of Seoul and Busan was chosen for the comparison of Daegu monitoring stations. The data analyzed in the current study were collected from 1998 to 2000 by Daegu Regional Environmental Management Office. The roadside concentrations of NO2 and PM10 and the exceedance frequency of ambient air standard levels in Daegu were higher than those of Seoul and Busan. Except O3, the roadside concentrations of all target compounds showed following three distinguished patterns; first, possibly due to increased traffic density, the concentrations increased from 0500 to 0900(LST), second, the concentrations decreased from 0900 to 1700(LST) possibly due to the increased wind velocity and decreased traffic density, and finally, increased traffic density, the concentrations increased again from 1700 to 2100(LST). An implication was that major air pollution sources shifted from residential area to road-area during rush hours.

Since low-floor apartments are vertically closer to parking lots and roadways, it is hypothesized that residents in low-floor apartments may be exposed to elevated ambient levels of motor vehicle emissions compared to residents in high-floor apartments. The present study examined this hypothesis by measuring two motor vehicle source-related pollutants(CO and PM10) in ambient air of high-rise apartment buildings within the boundary of industrial complexes according to atmospheric stability. The ambient air concentrations of CO and PM10 were higher for low-floor apartments than for high-floor apartments, regardless of atmospheric stability. The median concentration ratio of the low-floor air to high-floor air ranged from 1.3 to 2.0, depending upon atmospheric stabilities, seasons and compounds. Moreover, the CO and PM10 concentrations were significantly higher in the winter and in the summer, regardless of the floor height. Atmospheric stability also was suggested to be important for the residents' exposure of high-rise apartment buildings to both CO and PM10. The median ratios of surface inversion air to non-surface inversion air ranged from 1.2 to 1.7 and from 1.0 to 1.6 for PM10 and CO, respectively, depending upon seasons. Conclusively, these parameters(apartment floor height, season, and atmospheric stability) should be considered when evaluating the exposure of residents, living in high-rise apartment buildings, to CO and PM10. Meanwhile, the median PM10 outdoor concentrations were close to or higher than the Korean annual standards for PM10, and the maximum PM10 concentrations substantially exceeded the Korean PM10 standard, thus suggesting the need for a management strategy for ambient PM10. Neither the median nor the maximum outdoor CO concentrations, however, were higher than the Korean CO standard.

Present study evaluated the low-temperature destruction of n-hexane and benzene using mesh-type transition-metal platinum(Pt)/stainless steel(SS) catalyst. The parameters tested for the evaluation of catalytic destruction efficiencies of the two volatile organic compounds(VOC) included input concentration, reaction time, reaction temperature, and surface area of catalyst. It was found that the input concentration affected the destruction efficiencies of n-hexane and benzene, but that this input-concentration effect depended upon VOC type. The destruction efficiencies increased as the reaction time increased, but they were similar between two reaction times for benzene(50 and 60 sec), thereby suggesting that high temperatures are not always proper for thermal destruction of VOCs, when considering the destruction efficiency and operation costs of thermal catalytic system together. Similar to the effects of the input concentration on destruction efficiency of VOCs, the reaction temperature influenced the destruction efficiencies of n-hexane and benzene, but this temperature effect depended upon VOC type. As expected, the destruction efficiencies of n-hexane increased as the surface area of catalyst, but for benzene, the increase rate was not significant, thereby suggesting that similar to the effects of the reaction temperature on destruction efficiency of VOCs, high catalyst surface areas are not always proper for economical thermal destruction of VOCs. Depending upon the inlet concentrations and reaction temperatures, almost 100% of both n-hexane and benzene could be destructed. The current results also suggested that when applying the mesh type transition Metal Pt/SS catalyst for the better catalytic pyrolysis of VOC, VOC type should be considered, along with reaction temperature, surface area of catalyst, reaction time and input concentration.

Volatile organic compounds(VOCs) are of concern for their potential chronic toxicity, their suspected role in the formation of smog, and their suspected role in destruction of stratospheric ozone. Present study evaluated the exposures to selected VOCs in three microenvironments: 2 chlorinated and 5 aromatic VOCs in the indoor and outdoor air, and 5 aromatic VOCs in the breathing zone air of gas-service station attendants. With permissible Quality Assurance and Quality Control performances VOC concentrations were measured 1) to be higher in indoor air than in outdoor air, 2) to be higher in two Taegu residential areas than in a residential area of Hayang, and 3) to be higher in the nighttime than in the daytime. Among five aromatics, Benzene and Toluene were two most highly measured VOCs in breathing zone air of service station attendants. Based on the sum of VOC concentrations, the VOC exposure during refueling was estimated to be about 10% of indoor and outdoor exposures. For Benzene only, the exposure during refueling was estimated to cause about 52% of indoor and outdoor exposure. The time used to calculate the exposures was 2 minutes for refueling and 24 hours for indoor and outdoor exposures.

The use of chlorinated water in swimming pools produces elevated chloroform levels in the water and air of the pools which can cause chloroform body burden of swimming individuals. Present study confirmed the chloroform body burdens from a 40-min swimming and evaluated the decay of chloroform breath concentration after the cessation of a 60-min swimming. Air and water concentrations were measured in the pools. The water and air chloroform concentrations ranged from 18.1 to 25.3 ㎍/ℓ and from 30.9 to 60.7 ㎍/㎥ for the confirmation study, respectively. The breath level after 40-min swimming was about 64 to 266 folds higher than the corresponding background breath. The breath concentration after the 40-min swimming ranged from 10.5 to 21.3 ㎍/㎥, while that prior to the corresponding swimming ranged from 0.07 to 0.19 ㎍/㎥. In addition, the post-exposure breath level varied with the subjects who swam in the pool on the same visiting day. Breath concentration increased gradually during 60-min swimming, then decreased rapidly within 5 minutes after the cessation of exposure, after that, decreased slowly, and finally approached to a background breath level at 1-2 hr after exposure.

There has been an increased awareness of the need to confirm the chloroform exposure associated with using chlorinated household water. Ten of a 30-minute tub bath were normally taken by two volunteers in a bathroom of an apartment. Chloroform concentrations were measured in bathing water and bathroom air, and exhaled breath of the subjects prior to and after bathing. Bathing using chlorinated tap water resulted in a chloroform exposure and caused a body burden. Based on the difference of chloroform concentrations between breath samples collected prior to and after bathing, the chloroform body burden from a 30-minute bath was estimated to be about 8 to 26 folds higher than that prior to the bath. The mean water and bathroom air chloroform concentrations measured to evaluate the body burden were 9.4 ㎍/ℓ and 14.9 ㎍/㎥, respectively. The chloroform level of the bathroom air was 34 to 130 times higher than that of the living-room air. The relationship between the bathroom air and the corresponding breath chloroform concentrations were significant with p=0.03 and R^2=0.47.

Chloroform present in the swimming water disinfected with sodium hypochlorite is released to the air of swimming pools. The air chloroform concentrations were measured in two swimming pools A and B which applied both sodium hypochlorite and ozone. Their mean concentrations are 28.0 ㎎/㎥ and 33.6 ㎍/㎥ in the swimming pools A and B, respectively. On the other hand, the mean water chloroform concentrations in the swimming pools A and B were 23.9 ㎍/ℓ and 19.5 ㎍/ℓ, respectively. The air chloroform concentrations were lower in the swimming pools A and B than those reported by previous studies abroad employed the swimming pools which applied sodium hypochlorte only for water disinfection. The water chloroform concentrations were also lower in this study than in the previous studies. The relationship between the air and water chloroform concentrations measured in this study was significant with p=0.002 and R^2=O.42. At similar time to the indoor air sampling, outdoor air samples were collected at two sites near each of the swimming pools A and B. The mean outdoor air chloroform concentrations near the swimming pools A and B were 0.41 ㎍/㎥ and 0.16 ㎍/㎥, respectively. The outdoor air chloroform concentrations measured in this study were equal to or lower than those reported by previous studies abroad. The chloroform dose inhaled for a typical one-hour swim was estimated to be 25.9 ㎍ per person, corresponding to a specific 0.37 ㎍/㎏ body weight. for a reference 70 ㎏ male adult, while the inh lation dose of chloroform from the outdoor air was estimated to be 5.6 ㎍ per person per day, corresponding to a specific 0.08 ㎍/㎏/day for the same reference male adult.

Chlorinated water in swimming pools contains chloroform at elevated levels compared to chlorinated drinking water. Chloroform levels in four indoor swimming pools(swimming pools A, B and C in a city of Korea and swimming pool D in a city of New Jersey in the United States) were examined. The chloroform levels in the water of swimming pool C (city-managed) were shown to be significantly(p=0.0001) different from those of private swimming pools A and B: the mean chloroform levels in the pools A, B, and C are 22.8, 17.8, and 31.1 ㎍/ℓ respectively. Furthermore, all of these chloroform levels are significantly(p=0.0001) different from those of New Jersey: chloroform concentration of the Korean pools ranged from 10.9 ㎍/ℓ to 47.9 ㎍/ℓ with a mean of 23.2 ㎍/ℓ, while it ranged from 27 ㎍/ℓ to 96 ㎍/ℓ with a mean of 64.4 ㎍/ℓ in the New Jersey pool. The disinfection processes would cause part of this difference since the swimming pools in Korea applied both chlorination and ozonation method, while the swimming pool in New Jersey used chlorination method only. It was implied that swimming parameters inconsistently vary, resulting in fluctuation of and no constant accumulation of chloroform in the water with the change of time for the day. A regression analysis showed no relationships between sampling time and chloroform concentrations for the sampling day in the swimming pools of Korea. A F-test indicated no significant difference of chloroform concentrations in the morning and afternoon samples collected in the swimming pools. Ingestion dose was estimated to be 0.58 ㎍ from an hour swimming in a city of Korea, taking into accounting an average of 23.2 ㎍/ℓ in swimming pools in the city. In extreme situation, the ingestion dose was estimated to he 12.0 ㎍ from an hour swimming in a city of Korea.