The 2014 Time-Use Survey of Statistics Korea revealed that office workers are increasingly spending more than eight hours at work. This study conducted an exposure assessment for office workers in Korea. Indoor and outdoor air pollutants were measured in offices. A self-administered questionnaire was employed to determine work information, indoor air quality (IAQ) awareness, and subjective symptoms for 328 workers. Indoor air concentrations for measured air pollutants were below IAQ guideline values. The average concentrations of target air pollutants did not show significant differences except for benzene, which had relatively a higher concentration in national industrial complexes. The indoor benzene, ethylbenzene, and acetaldehyde concentrations were higher in offices where workers were having dry eye, ophthalmitis, and headache symptoms. This study provides reference values to manage IAQ in offices, suggesting that if the benzene concentration exceeds 4.23 μg/m3 in offices, it could cause dry eye symptoms. Considering the increasing working hours for office workers and health effects, workers' exposure to indoor pollutants should be reduced. In addition, the IAQ was heavily influenced by outdoor air levels and various indoor sources. Therefore, in areas with relatively high air pollution, greater monitoring and management is required considering the influence of outdoor air quality.

Background:The coronavirus disease (COVID-19) has caused changes in human activity, and these changes may possibly increase or decrease exposure to fine dust (PM 2.5 ). Therefore, it is necessary to evaluate the exposure to PM 2.5 in relation to the outbreak of COVID-19. Objectives:The purpose of this study was to compare and evaluate the exposure to PM 2.5 concentrations by the variation of dynamic populations before and after the outbreak of COVID-19.Methods: This study evaluated exposure to PM 2.5 concentrations by changes in the dynamic population distribution in Guro-gu, Seoul, before and after the outbreak of COVID-19 between Jan and Feb, 2020. Gurogu was divided into 2,204 scale standard grids of 100 m×100 m. Hourly PM 2.5 concentrations were modeled by the inverse distance weight method using 24 sensor-based air monitoring instruments. Hourly dynamic population distribution was evaluated according to gender and age using mobile phone network data and time-activity patterns.Results: Compared to before, the population exposure to PM 2.5 decreased after the outbreak of COVID-19.The concentration of PM 2.5 after the outbreak of COVID-19 decreased by about 41% on average. The variation of dynamic population before and after the outbreak of COVID-19 decreased by about 18% on average. Conclusions:Comparing before and after the outbreak of COVID-19, the population exposures to PM 2.5 decreased by about 40%. This can be explained to suggest that changes in people's activity patterns due to the outbreak of COVID-19 resulted in a decrease in exposure to PM 2.5 .

Background: Lung injuries due to exposure to humidifier disinfectants (HDs) were reported in 2011 in South Korea. As a result of the government's epidemiological investigation and toxicity test study, it was found that HDs caused health damage such as lung disease. Objectives:The purpose of this study was to classify HD exposure ratings and analyze the affecting factors that could identify the relationship with lung disease.Methods: Exposure assessment for HDs was conducted using a questionnaire during face-to-face interviews with the applicants. Ratings of high exposure (Class 1) and low exposure (Class 2) were cross-tabulated with clinical ratings (acceptable and unacceptable). Logistic regression analysis was carried out by setting the clinical rating of lung disease as a dependent variable and the socio-demographic and exposure characteristics obtained through the questionnaire as independent variables. Results:The concentration in air of polyhexamethylene guanidine (PHMG) was 71.96±107.47 µg/m 3 , and the exposure concentration was 15.21±23.28 µg/m 3 . The exposure rating was overestimated with 97.1% of affected subjects having high exposure using margin of exposure (MOE), but only 9.9% matching the clinical class. In the overestimated group, it could be explained by the fact that the exposure time was long and the subjects had already recovered from damage symptoms. As a result of logistic regression analysis, ten variables were found to be significant influencing factors. Conclusions:A new exposure rating could be calculated based on the MOE, and factors affecting lung disease could be estimated through comparative evaluation with the clinical rating.

Background: Since people move through microenvironments rather than staying in one place, they may be exposed to both indoor and outdoor PM 2.5 concentrations. Objectives:The aim of this study was to assess the exposure level of each sub-population group and evaluate the contribution rate of the major microenvironments.Methods: Exposure scenarios for sub-population groups were constructed on the basis of a 2019 Time-Use survey and the previous literature. A total of five population groups were classified and researchers wearing MicroPEM simulated monitoring PM 2.5 exposure concentrations in real-time over three days. The exposure contribution for each microenvironment were evaluated by multiplying the inhalation rate and the PM 2.5 exposure concentration levels.Results: Mean PM 2.5 concentrations were 33.0 µg/m 3 and 22.5 µg/m 3 in Guro-gu and Wonju, respectively.When the exposure was calculated considering each inhalation rate and concentration, the home showed the highest exposure contribution rate for PM 2.5 . As for preschool children, it was 90.8% in Guro-gu, 94.1% in Wonju. For students it was 65.3% and 67.3%. For housewives it was 98.2% and 95.8%, and 59.5% and 91.7% for office workers. Both regions had higher exposure to PM 2.5 among the elderly compared to other populations, and their PM 2.5 exposure contribution rates were 98.3% and 94.1% at home for Guro-gu and Wonju, respectively. Conclusions:The exposure contribution rate could be dependent on time spent in microenvironments.Notably, the contribution rate of exposure to PM 2.5 at home was the highest because most people spend the longest time at home. Therefore, microenvironments such as home with a higher contribution rate of exposure to PM 2.5 could be managed to upgrade public health.

Background:The Korea Centers for Disease Control and Prevention (KCDC) has identified cases of people suspected of suffering lung disease potentially caused by chloromethylisothiazolinone/methylisothiazolinone (CMIT/MIT) used in humidifier disinfectants (HDs). The Korean Ministry of Environment (MoE) epidemiological investigation and toxicity test study found that HDs caused health damage such as asthma and lung disease. Objectives:The main purposes of this study were to classify the HD exposure rating and to analyze the exposure characteristics that affect exposure to CMIT/MIT HDs. Methods:The exposure characteristics and socio-demographic characteristics of victim participants using CMIT/MIT HDs were investigated through questionnaires. An inhalation no observed adverse effect level (NOAEL) for CMIT/MIT was produced based on inhalation toxicity values. Exposure ratings (class 1~class 2) were cross-tabulated with clinical ratings (acceptable~unacceptable). A correlation analysis was conducted with the main exposure characteristics that affect the exposure concentration of CMIT/MIT HDs. Results:The concentration in indoor air of CMIT/MIT was 8.75±25.40 μg/m 3 , and the exposure concentration was 2.30±6.29 μg/m 3 . The CMIT/MIT exposure rating of 67 participants with high exposures of not more than MOE 100 were evaluated as 14.5%, while the damage participants who matched the clinical rating made up 4.5%. The exposure concentration of CMIT/MIT showed a positive correlation with the daily usage amount and usage frequency, and a negative correlation with volume of the indoor environment. Conclusions:A new exposure rating could be suggested and calculated based on the MOE, and the factors affecting the exposure concentration could be identified.