Information about time spent in microenvironments plays a critical role in exposure assessment of the person concerned, considering that personal exposure relies on the characterization of time-activity patterns of the population at risk as human activities impact the timing, location, and level of personal pollutant exposure. The purpose of this paper was to present the time-activity patterns of Korean adults from a population-based study, and to determine the time spent each day in microenvironments. The population-based study collected time-activity data of about 46,000 adults for two consecutive days on weekdays (n=28,152) and weekends (n=18,800). The mean times spent at one’s own house, workplace or school, other’s house house, restaurant or bar, other places, and transportation related to the whole sample of 28,152 people were 14.90 hrs (62.08%), 4.28 hrs (17.81%), 0.24 hrs (1.01%), 0.51 hrs (2.14%), 2.45 hrs (10.21%), and 1.62 hrs (6.74%) on weekdays, respectively. Looking at the total time spent indoors by adults in different countries, the following four countries were ranked as follows, from lowest to highest: USA > Canada > Korea > Hong Kong. Due to cultural, socioeconomic and climatic differences, it may not be appropriate to directly apply statistical data of other countries to the Korean situation. This paper provides information on how the proportion of persons in different locations changes by time of day, on weekdays and weekends. Here, we can see that over 90% of respondents were in a residence from about 11 PM to 5 AM, and the largest proportion of respondents in workplaces or schools and other places is found between 8 AM and 5 PM.

The consumer products in the living environments include a variety of chemicals which could be harmful in the human health. The aim of this study was to assess the inhalation exposure and risk for cleaning workers who had used bleach in the university. A total of 81 cleaning workers took part in this study. Frequency and amount of cleaning bleach during working hours were investigated by questionnaire interviews. Exposure assessment was used by the exposure algorithm and exposure factors. Used cleaning bleaches were analyzed to identify the ingredients, and risk by exposure was assessed by separating as carcinogen and non-carcinogen substances. The results of chemical substances and the questionnaire were used to assess the exposure factors, and the inhalation doses were calculated through inhalation exposure algorithm. According to the questionnaires for the cleaning workers, frequence of cleaning bleach was 11.66 ± 7.21 times per month. And average usage time and amount per cleaning work were 30.78 ± 36.00 minute and 20099.53 ± 12998.60 mg, respectively. Risks for carcinogenic substances of formaldehyde, ethylbenzene, and chloroform were exceeded by 56.79%, 27.16%, and 82.72% as the reference value of 10−6, respectively.

We measured VOCs and NO2 in the indoor and outdoor air at 125 houses in Jeollanam-do and Gyeongsangnamdo, from March 2007 to January 2008. The concentration of benzene measured in the Gwangyang survey group was higher than in Yeosu and Hadong, and showed a statistically significant difference from Yeosu (p<0.05). The concentration of toluene in outdoor air was highest in the Gwangyang survey group. The concentration of NO2 measured in the Yeosu survey group was higher than in Gwangyang and Hadong, and showed a statistically significant difference from Hadong (p<0.01). According to the results of a correlation analysis, VOCs (benzene, toluene, xylene, ethylbenzene) exposure of individuals showed a significant correlation with the residential indoor air (p<0.01). Also, VOCs of residential indoor and outdoor air showed a significant correlation (p<0.01). The concentration of NO2 exposure of individuals measured in the Yeosu comparison group showed a high correlation with the residential indoor air.

The concentration of VOCs, NO2 was measured both inside and outside residential homes surrounding an industrial complex. Measurements were performed in the area of the industrial complexes and around 10 km away from the industrial complex area. Benzene did not exceed the air quality standard value. Toluene exhibited a high value of concentration in outdoor Yeosu investigated group. The concentration of NO2 is higher than outside concentrations of houses in both inside housing research group compared with the group of Gwangyang and Yeosu. Benzene and toluene showed high correlation (p<0.001) in the housing interior in Gwangyang, It showed a high correlation (p<0.01) in the housing interior in the comparison group. In Yeosu there was a high correlation (p<0.001) between the inside and outside of the housing in the survey group. In the control group there was only high correlation (p<0.05) in the inside of the housing.

The concern of fine particle (PM2.5) management of outdoor environments has been increasing due to its exposure and related health effects in Korea. As a result, PM2.5 standard in atmosphere environment was regulated in 2015. On the other hand, indoor PM2.5 standard has been required because most people spent their times in indoor environments. In this study, we measured the PM2.5 and PM10 concentrations both indoor and outdoor environments of public-use facilities such as underground stations, underground shopping centers, and nurseries for 24 hour with filter-weighing method in Seoul and Daegu. Measurement duration was from March to April in 2014 during the Asian dust period. At all measurements, indoor to outdoor (I/O) concentration ratios exceeded 1 except 1 day nursery in Daegu in spite of Asian dust period. The ratios of PM2.5 to PM10 concentrations ranged from 0.63 to 0.75 in indoor environments, and from 0.63 to 0.82 in outdoor, indicating that PM2.5 should be carefully managed in indoor environments as well as outdoor atmosphere.

This study was a time activity pattern assessment focused on transportation in subpopulation groups using the ‘Time-Use Survey’ conducted by the National Statistical Office in Korea in 2009. The time activity patterns of transportation on weekdays were analyzed, looking at average travel time in Seoul, Gyeonggido and the whole country. Various subpopulation groups were classified such as students, the elderly, workers and housewives. The population of Gyeonggido had a higher average transportation time than that of Seoul. Workers showed the highest weekly average travel, while the students group showed the lowest tendency. The times spent in walking, bus, subway and taxi were the highest in areas other than Gyeonggido, where the use of private vehicles such as car was higher. Therefore, exposure to hazardous air pollutants may vary depending on the transportation method and time spent. This results indicate that time activity pattern assessment on transportation may be an important element of exposure assessment.

The objectives of this study were to characterize the factors affecting exposure to the VOCs and NO2 in the vicinity of Gwangyang industrial complex. The VOCs and NO2 levels were measured for residents of an exposure group (industrial area within 5 km) and a control group (15 km farther), respectively using the VOCs and NO2 filter badge as a passive sampler from August to September 2006. The means of indoor, outdoor, workplace and personal exposure levels of benzene were 1.10 ppb, 0.94 ppb, 1.85 ppb and 2.35 ppb respectively in the exposure group. The means regarding toluene for the exposure group were 9.29 ppb indoor, 8.09 ppb outdoor, 14.5 ppb workplace, 14.2 ppb personal exposure. The means regarding ethylbenzene were 4.96 ppb(indoor), 4.45 ppb(outdoor), 6.84 ppb (workplace), 6.10 ppb(personal exposure), and the means regarding xylene were 0.10 ppb(indoor, outdoor), 0.18 ppb(workplace) 0.17 ppb(personal exposure). The means for the indoor, outdoor, workplace and personal exposure level of NO2 were 18.40 ppb, 18.51 ppb, 18.59 ppb, 18.80 ppb respectively in the exposure group. Correlations between personal exposures and workplace concentrations of individual VOCs and NO2 exposures, and each of the microenvironment was statistically significant.

Hazardous air pollutants such as NO2, VOCs and PM10 were measured Daegu, Korea in major micro-environments,where housewives spend the most of their time, and personal exposure times were estimated by using time activitypatterns and exposure scenarios. The major microenvironments of housewives were selected using the ‘Time-UseSurvey’ conducted by the National Statistical Office in Korea in 2009. A total of 4,514 (weekdays) and 3,063(weekends) housewives were recruited for the ‘Time-Use Survey.’ It seems that housewives are spending about80% of their time in the house, and about 5% of their time outdoors during weekdays and weekends. The indoor/outdoor ratio of the average concentration of NO2 was more than 1, which indicated that the source was indoors.Toluene was shown to have higher concentrations indoors than outdoors. Ethylbenzene and xylene displayedsimilar characteristics to toluene, and the concentration ratio for indoor/outdoor was shown to be 1.29 ± 0.76 and1.04 ± 0.45, respectively, higher concentrations indoors. Based on the results of the time activity patterns ofparticipants, 3 kinds of exposure scenarios were formulated. The spent time and air concentration in eachenvironment were assumed as normal and lognormal distribution, respectively. And then the Monte-Carlosimulation was conducted. According to the result of the simulation, the exposures to hazardous air pollutantsrevealed an increasing pattern as housewives visits other indoor environments such as supermarkets.

The objective of this study is to offer basic scientific data to support policy decision-making for the improved control of nitrogen dioxide(NO₂) and nitrous acid(HONO) in residence. The survey on concentration of NO₂and HONO in 20 houses in Seoul and Daegu was performed from January to February, 2013. Average NO₂concentrations in the kitchen, living room, and room were 25.7 ± 7.7 ppb, 24.3 ± 8.5 ppb, and 19.6 ± 5.6 ppb, respectively. Also, average HONO concentration were 3.6 ± 1.0 ppb, 3.1 ± 0.9 ppb, and 3.1 ± 0.9 ppb, respectively. NO₂and HONO concentration in kitchen were significantly higher than the concentration in the living room and room(p<0.05). Concentration ratios of HONO/NO2 were ranged to 0.070 0.277 for indoor air and 0.004 0.161 for outdoor air. Indoor HONO/NO2 ratios were higher than the outdoor HONO/NO₂ratios.

Information on time spent in microenvironments has a critical role in individuals’ exposure assessment. Time-activity studies have become an integral part of comprehensive exposure assessment and personal exposure modeling. The aims of this study were to estimate the exposure level of NO₂, PM₁₀ and VOCs, and to compare the estimated exposure by using time-activity pattern and indoor air concentration. This study was performed upon 28 university students living in Daegu. We measured air pollutants of NO₂, PM₁₀ and VOCs at houses where the university students spent most their times. In this study, according to the summer and winter, time-activity patterns of university students were different. The 28 university students average spending times in house indoors and other indoors time were 11.52±2.14 and 7.63±2.65 hours in summer, and 14.78±3.30 and 6.59±3.03 hours in winter, respectively. The university students personal exposure NO₂ concentrations were average 21.62±5.88 ppb and I/O ratio was 0.89±0.27. Personal average exposure of PM₁₀ concentration was between house indoors and outdoors concentrations which indoor house concentration was 37.68±7.57 μg/m³ and outdoor house concentration was 43.85±9.80 μg/m³ with 0.88±0.17 of I/O ratio. Personal exposure to benzene and the average concentration of benzene did not exceed in atmosphere environmental standard (annual 1.5 ppb) and the outdoor houses concentration was much higher than indoor houses.

Exposure to environmental tobacco smoke (ETS) could adversely affect health. The aim of this study was to quantify the contribution of ETS exposure in nonsmokers of entertainment facilities. We simultaneously measured nicotine and nitrogen dioxide (NO₂), which are known as indicators of ETS, concentrations in indoor internet cafe, billiard, karaoke, bar and restaurant, and estimated exposure level of other harmful agents occurred from tobacco smoking. Mean nicotine concentration (10.57±2.53㎍ /m³ ) of internet cafe was the highest comparing to other facilities, whereas mean concentration of restaurant where was non-smoking area was 0.28±0.08㎍ /m³ . There was statistically not correlated between NO₂ and nicotine concentrations in entertainment facilities. Therefore, the use of NO₂ concentration as indicator of ETS exposure may not be available. To date, there are no standards about each agent occurred from ETS. Consequently administrative control and regulation, and further researches in relation to ETS exposure should be needed.

Personal or population exposure to hazardous air pollutants has often been assessed by time-weighted average model with combining concentrations of indoor environments and time-activity pattern, which were mainly a single measurement. However, daily levels of air pollutants in indoor environments may greatly be changed because of source emission, ventilation, decay rate and so on. Subsequently exposure by a single measurement in indoor environments could not be assessed properly. In this study, we measured the consecutive 21 daily indoor and outdoor measurements of nitrogen dioxide (NO₂) with 37 houses and 19 shops such as restaurants and coffee shops beside street by using of passive samplers. Considering that average concentration during 21 days was true value, paired t-test was conducted. Daily variations of NO₂ in houses with constant or low emission source were different from those in restaurants with irregular or high emission source. These results can be explained that the NO₂ emission of indoor sources could affect the validity of measurement periods.

We measured indoor, outdoor, and personal exposure concentrations of ozone (O₃) at 54 households in Gwangyang from June to September, 2009. The results are as follows. The concentration of ozone in outdoor, 16.53±5.72 ppb, was observed two times higher than the concentration of ozone in indoor, 8.22 ± 4.60 ppb. The similar arithmetic average ozone were obtained in exposed and controlled areas, 15.16 ± 1.45 ppb and 15.25 ± 1.94 ppb, respectively. The ozone concentration of an individual smoker was 24.89 ± 7.11 ppb, which was higher than that of a non-smoker, 21.01 ± 11.79 ppb. The indoor occupant density elevated ozone concentrations. The relatively low concentration of ozone was observed in a house with air conditioner (8.59 ± 4.04 ppb) than a house without the unit(10.07 ± 6.43 ppb).

In this study, we estimated nitrogen dioxide (NO₂) concentrations in microenvironments where residential indoor, residential outdoor, other indoors, and transportation using measured personal exposure and multiple linear regression analysis of time-weighted average model, and compared with measured NO₂ concentration in microenvironments. Measured residential indoor, outdoor and other indoor NO₂ concentration was 22.22±9.59 ppb, 23.64±9.62 ppb, and 22.07±13.90 ppb, respectively. NO₂ concentrations in residential indoor and outdoor, total outdoor, other indoor, and transportation by multiple regression analysis were significantly estimated as 20.48 ppb, 32.79 ppb, 24.35 ppb, and 28.82 ppb, respectively (p= 0.000). Measured and estimated NO₂ concentration were similar with each other, therefore NO₂ concentrations in each microenvironment were able to be estimated using time-weighted average model and personal exposure with multiple regression analysis.

The purpose of this study was to assess an alternative method to characterize indoor environmental factors by multiple indoor and outdoor measurements. Using a mass balance model and regression analysis, penetration factor and source strength factor were calculated using multiple indoor and outdoor measurements. This study was performed in 30 selected apartments in Seoul, Asan, and Daegu area which were constructed within 4 years and over 4 years, to measure the concentration of NO₂ from July, 2004 to September. The results of this study are as follows. The average concentration of NO₂ in Seoul, Asan, and Daegu area in the apartment constructed within 4 years are nitrogen dioxide 48.01㎍/m³ and in the apartment over 4 years are nitrogen dioxide 46.54㎍/m³. Mean ratios of indoor to outdoor NO₂ concentrations are Seoul 0.99, Asan 0.83, Daegu 1.18. The deposition constant and the source strength of NO₂ were 0.97±0.55 hr-1 and 16.33±12.30 ppb/h, respectively. In conclusion, indoor environmental factors were effectively characterized by this method using multiple indoor and outdoor measurements.

This study presents residential indoor and outdoor exposure concentrations distributions of volatile organic compounds (VOCs, benzene, toluene, xylene) and nitrogen dioxide (NO₂) in industrial area (case) and agricultural area (control) during 5 days. Concentrations of VOCs and NO₂ were measured with passive samplers in residential indoor and outdoor. Most of benzene, toluene and NO₂ mean concentrations in case area were higher than those in control area. Considering the indoor and outdoor ratios (I/O) were higher than 1, the residence might be have the sources of indoor air pollutants such as smoking and using of gas range. Residential indoor concentrations of benzene, toluene, and NO₂ with indoor smokers were higher than those and without indoor smokers. In conclusion, it is suggested that personal exposures to air pollutants might be affected by indoor sources as well as outdoor pollutants emitted from industrial complex, and indoor air quality and outdoor air quality should be simultaneously considered to reduce the personal exposure to air pollutants.

The mask-face interface design should consider the face shape to improve the half mask respirator's fit ratio. This study tried to design the mask-face interface using recent Korean face data. By using the data of 1536 men's 3D face scanning (Size Korea data), head clay mock-up was made and mask-face interface line was extracted from this head mock-up. Using this interface line, the half-mask prototype was made. According to the quantitative fitting test, the proposed mask was found to be well fitted (average fit-ratio > 100). The proposed method had two advantages. 1) The method could use massive head-related anthropometric data like Size Korea data. 2) The qualitative fit test (observation) could be conducted very quickly by fitting the prototype to the head mock-up. However, this method also had several limitations. 1) The head clay mock-up could be different according to the mock-up maker. 2) The average values of the head-related anthropometric data were used to make the head mock-up. Small and large size head mock-ups should be made and tested.

Indoor, outdoor, and personal nitrogen dioxide (NO₂) exposures were studied in a population of housewives. Daily Indoor and outdoor NO₂ concentrations were measured and compared with simultaneously personal exposures of 17 housewives for 7 consecutive days in 17 houses. In this study, indoor and outdoor NO₂ samples at home were collected only while the housewives were at home samples. Time activity patterns and house characteristics were used to determine the effects of these factors on personal exposure. Since housewives spent their times in indoor houses with mean of 78.3%, their NO₂ exposures were associated with indoor houses NO₂ levels (r= 0.89) rather than outdoor NO₂ level (r= 0.85). Contribution of indoor NO₂ concentration on personal exposure was estimated by 70.77% by using of mass balance model. The close association between measured indoor NO₂ concentrations and measured personal exposure and contribution of indoor NO₂ concentration suggests that measuring indoor concentrations of NO₂ in the home is sufficient to estimate personal exposure accurately.

The information about time spent in microenvironments plays a critical role for an exposure assessment of the person concerned, considering the personal exposure relies on the characterization of activity patterns of the population at risk and human activities impact the timing, location, and level of personal pollutant exposure. The purposes of this paper were to present indoor time activity patterns of Korean from a population-based study and to determine individual factors of time spent in microenvironments. The population based study collected time activity pattern of about 32,000 Korean for two consecutive days. The mean times spent at home, other indoors, outdoors, and transportation in related to the whole sample of 19.025 people are 14.23hrs(59.3%), 6.80hrs(28.3%), 1.26hrs(5.2%), and 1.75hrs(7.3%) in weekday, respectively. Database provides information on how the proportion of persons in different locations changes by time of day in weekday. Here, we see that over 90% of respondents were in a residence from about 11 PM to 5 AM, and the largest proportions of respondents in offices, factories, schools and public buildings occur between 8 AM and 5 PM.

Indoor air quality can be affected by indoor sources, ventilation, decay and outdoor levels. Although technologies exist to measure these factors, direct measurements are often difficult. Toluene and nitrogen dioxide (NO₂) concentrations of residential indoor and outdoor were simultaneously measured and compared in 16 houses, using passive samplers during every 3 days for 60 days. Concentrations of toluene and NO₂ were analyzed by gas chromatography and spectrophotometer, respectively. Using a mass balance model, penetration factor (ventilation rate divided by sum of ventilation rate and deposition constant) and source generation factor (source generation rate divided by sum of ventilation rate and deposition constant) were calculated by multiple indoor and outdoor measurements. The mean contributions of toluene of indoor and outdoor sources on residential indoor air quality were estimated to be 31.01% and 67.00%, respectively. On the other hand, mean contributions of NO₂ were 58.93% and 41.06%, respectively. These results could be explained that contributions of indoor and outdoor air pollutants sources are different to residential indoor air concentrations. In conclusion, contributions of outdoor air and indoor sources affecting indoor air quality were effectively characterized using multiple indoor and outdoor measurements.