Changes in total volatile organic compound concentration in Seoul subway stations before (2019) and after (2021) the COVID-19 outbreak.

Volatile organic compounds (VOCs) are major air pollutants often designated as specific hazardous or toxic. This study analyzed the trends in concentration changes and influencing factors of VOCs in underground subway stations in the Seoul Metro before (2019) and after (2021) the COVID-19 pandemic. A total of 506 samples were collected from 253 stations on lines 1-8 between May 2019 and September 2021. Total VOC concentrations in Seoul Metro increased after the COVID-19 pandemic 3.8 times over. The deeper the underground station platform, the greater the difference in the VOC concentrations between 2019 and 2021, which was positively related. Average VOC concentration was the highest (52.8 µg/m3) at a depth of 25-30 m and the lowest (23.9 µg/m3) at a depth of < 10 m in 2019. In conclusion, excessive disinfection during the COVID-19 pandemic resulted in increased VOC concentrations in the Seoul Metro, especially in the deeper underground stations. Less frequent quarantine disinfection is recommended to improve air quality.

Indoor exposure assessment for levels of dust mite and total volatile organic compounds (TVOCs) in living houses.

The purpose of this study is to measure the levels of dust mites (Dermatophagoides farina group 1 [Der f1] and Dermatophagoides pteronyssinus group 1 [Der p1]) and total volatile organic compounds (TVOCs) in the resident environments with living conditions such as the number of ventilation; the number of window, floor, and temperature; and relative humidity (RH) from vulnerable class in South Korea. Information on residents is designed to be prepared by residents on their general characteristics (daily residence time, heating and cooking type, and cleaning on the day of sampling). Dust mites levels ranged from 24.0 to 1087.5 ng/g with a mean of 215.4 ng/g for Der f1 and from 0.6 to 489.9 ng/g with a mean of 489.9 ng/g for Der p1. Total TVOC levels ranged from 15.3 to 1642.1 µg/m3 with a mean of 219.7 µg/m3. The correlation analysis showed a positive association between Der f1 levels and xylene levels in fall (r = 0.49, r < 0.05) of this study.

Association between levels of radon and bioaerosols (bacteria and fungi) by living conditions.

This study aimed to measure the levels of airborne radon Rn and bioaerosols - culturable airborne bacteria (CAB) and culturable airborne fungi (CAF)-in South Korea's residential environments, considering living conditions such as the number of ventilations, number of windows, floors, temperature, and relative humidity. . The range of Rn levels was 0.43-7.439 pCi/L with a median of 0.70 pCi/L. The CAB levels were 239-488 colony-forming unit (CFU)/m3 with a median of 309 CFU/m3, and CAF levels were 174-366 CFU/m3 with a median of 233 CFU/m3. Thus, this study found that semi-basement residential indoor environments negatively affected Rn and bioaerosol levels, and living in such residences resulted in high health condition scores on the bad side. Given the correlation between airborne Rn and bioaerosol levels, further large-scale studies are needed to identify more reliable and representative of research.

Prediction Model for Job Retention According to the Type of Return to Work Among Industrially Injured Workers in Korea.

OBJECTIVES: This study aimed to investigate how the type of return to work after an industrial accident affects job retention. METHODS: Using data from the panel study of workers' compensation insurance first-third, and hazard ratios (HRs) and 95% confidence intervals were calculated for workers leaving their jobs. RESULTS: The HR leaving their jobs were higher in the "reemployed" compared with that in the "returned to original work," with HR of 2.69 (2.33-3.10). According workers' status, the HRs leaving their jobs were higher among the "reemployed" than among those who "returned to original work." Regular and daily workers' HRs were 1.70 (1.37-2.11) and 3.55 (2.96-4.26), respectively. CONCLUSIONS: The findings suggest that to increase job retention rate, protection policies for reemployed workers or support for employers who hire reemployed workers should be considered.

Indoor air concentrations of carbon dioxide (CO2), nitrogen dioxide (NO2), and ozone (O3) in multiple healthcare facilities.

This study evaluates indoor air concentrations of CO2, NO2, and O3 and their relationship to other indoor environmental factors in facilities with occupants susceptible to air contaminants, such as hospitals, senior specialized hospitals, elderly care facilities, and postnatal care centers. Indoor air samples were collected from 82 indoor facilities in South Korea and organized by region. Spearman's correlation and Kruskal-Wallis analyses were employed to examine the relationship among and differences between contaminants in the indoor facilities and indoor/outdoor differences of NO2 and O3 concentrations. Significant correlations were found between CO2 and NO2 concentrations (r2 = 0.176, p < 0.01), as well as NO2 and O3 concentrations (r2 = - 0.289, p < 0.0001). The indoor/outdoor concentration ratios in the indoor facilities were 0.73 for NO2 and 0.25 for O3. CO2 and NO2 displayed the highest mean concentrations during spring, while O3 displayed the highest and lowest mean concentrations during fall and summer, respectively. The calculated hazard quotient (HQ) for NO2 was higher than the acceptable level of 1 in postnatal care centers, thus posing a health risk for children. Study results indicate that efficient ventilation is required to reduce indoor contaminants in multiple healthcare facilities. This study provides a novel approach toward health risk assessment for indoor facilities with susceptible occupants on a large geographical scale.

Changes in Income after an Industrial Accident According to Industry and Return-to-Work Status.

Objective: To investigate changes in the incomes of workers, particularly those in the construction sector, who experienced industrial accidents according to their status of return to work. Methods: We used data from the fifth Panel Study of Workers' Compensation Insurance. A repeated measures ANOVA was used to compare annual differential incomes before and after the industrial accident, and a linear mixed model was used to investigate the changes in income from before to after the industrial accident according to the industry and return-to-work status. Results: A comparison of the industrial categories revealed that construction industry workers exhibited the greatest incomes before the accident and the greatest decrease in income after the industrial accident. Regression analysis for assessing changes in income after the industrial accident showed that a comparison by industry revealed a significantly greater reduction in income in the construction than service industry. A comparison by work status revealed significantly greater decreases in income in the reemployment and non-return to work groups than among those who returned to their original work. Conclusions: The economic statuses of the victims of industrial accidents decreased relative to the pre-accident statuses in all industries. The ability to return to original work is important for preserving the accident victim's economic status.

Radon and PM10 concentrations in underground parking lots and subway stations with health risks in South Korea.

This study examined the environmental factors that affect indoor radon (Rn) and particulate matter (PM10) concentrations in underground public facilities such as subway stations and underground parking lots. Rn and PM10 concentrations from March 2014 to October 2015 were evaluated at 40 subway stations and 19 underground parking lots. Average underground concentrations of Rn and PM10 were 37.3 ± 17.1 Bq/m3 and 78.6 ± 15.1 µg/m3, respectively. There were significant difference in Rn concentration between sampling points, with the highest concentration 41.8 ± 18.1 Bq/m3 on subway platforms, while the highest concentration of PM10 was 83.7 ± 13.8 µg/m3 in transfer pathways. Rn concentration showed positive correlation with PM10 concentration (r = 0.380, p < 0.001). The highest Rn concentration occurred during fall season, followed by summer and spring. At 60-h exposure duration in underground subway stations and parking lots, the hazard quotient (HQ) of Rn exceeded 1 for children less than 1 year old and those between 8 and 10 years old.

Evaluation of PM10, CO2, airborne bacteria, TVOCs, and formaldehyde in facilities for susceptible populations in South Korea.

Poor indoor air quality can have adverse effects on human health, especially in susceptible populations; however, few studies have measured multiple pollutants in facilities for susceptible populations at a national scale in South Korea. Therefore, we measured the concentrations of indoor pollutants (fine particulate matter (PM10), CO2, airborne bacteria (AB), total volatile organic compounds (TVOCs), and formaldehyde) to determine their possible relation to other indoor environmental factors and characteristics of facilities with susceptible populations, such as hospitals, geriatric hospitals, elderly care facilities, and postnatal care centers throughout South Korea. Indoor pollutants were sampled at 82 indoor facilities, including 62 facilities for susceptible populations. Spearman's correlation, Kruskal-Wallis, and Mann-Whitney analyses were used to examine the relationship among and differences between pollutants at indoor facilities and indoor/outdoor differences in PM10 concentration. There were significant correlations between indoor temperature and AB concentration (r = 0.37, p < 0.01), TVOCs, and formaldehyde (r = 0.264, p < 0.01). Indoor PM10 concentrations were higher than outdoor concentrations at all facilities for susceptible populations (p < 0.01). CO2 might be a good indicator for predicting indoor pollutants when categorized into two levels (≤750 ppm and >750 ppm). The hazard quotient of formaldehyde was higher than the acceptable level of 1 for children under the age of eight in postnatal care centers, indicative of unsafe levels. Therefore, more depth study for exposure characteristics of formaldehyde and indoor air quality (IAQ) in postnatal care facilities as a national scale is needed for finding the children exposure levels.

Factors affecting ambient endotoxin and particulate matter concentrations around air vents of subway stations in South Korea.

Levels of airborne endotoxins and particulate matter less than 10 µm and 2.5 µm in diameter (PM) were measured in the air vents of subway stations in Seoul, South Korea, and factors affecting both pollutants were analyzed. The measurements were completed from March 2016 to February 2017 for eight air vents situated at the ground level around the subway stations. A total of 166 air samples were collected and analyzed using the kinetic limulus amebocyte lysate assay. Endotoxin levels ranged from not detected to 1.986 EU m-3, with a mean of 0.227 EU m-3. The results showed significantly different PM levels from the measurements reported by AIRKOREA as part of the comprehensive air quality index. This can be attributed to different sampling sites in the same area. Endotoxin levels tended to be higher in fall compared to summer. Airborne bacteria levels showed a pattern similar to the endotoxin levels, but no significant association was reported between them. The levels of endotoxins around air vents with a glass cover and streets that allowed smoking were significantly higher than those not containing a walled barrier and streets in which smoking was prohibited. Multivariate regression analysis showed that the factors affecting endotoxin levels comprised air vents with a glass cover (coefficient = 0.106, p = 0.014) and season (coefficient = 0.062, p < 0.0001). Therefore, installing barriers on the air vents and prohibiting smoking in streets to which the vents open may be effective ways to lessen exposure to airborne endotoxin levels around air vents.

Radon and NO2 levels and related environmental factors in 100 underground subway platforms over two-year period.

In this study, the environmental factors that affect radon (Rn) and nitrogen dioxide (NO2) levels in subway-station underground platforms are evaluated, and the outdoor NO2 levels are compared with those obtained for the underground platforms. The Rn and NO2 levels from May 2013 to September 2015 are determined for lines 1-4 of the Seoul Metro, via calculation of the arithmetic means of the Rn and NO2 levels with their standard deviations (SDs). The underground Rn levels in 2013 are found to be significantly higher than those recorded in 2015 for the Seoul Metro. In addition, the Rn levels are related to the station depth and construction year. Further, the underground NO2 levels are shown to be significantly higher than the outdoor levels for all four Seoul Metro subway lines. The Rn levels are also found to vary significantly between months, and are shown to increase gradually with depth from 8 to 20 m. The Rn levels are also higher for stations constructed in the 1980s. Therefore, stricter monitoring of Rn level may be required for stations constructed in the 1980s and/or having platform depths within the 8-20 m range. Island-type platform stations based on granite areas may also require careful attention.

Formaldehyde and carbon dioxide air concentrations and their relationship with indoor environmental factors in daycare centers.

The aim of this study was to measure the air concentrations of carbon dioxide (CO2) and formaldehyde (HCHO) in daycare centers to determine relevant influencing factors, including temperature, relative humidity (RH), type of facility, number of children, type of ventilation system, ventilation time, and air cleaning system. The authors measured HCHO, CO2, temperature, and RH in the center of classrooms in 289 daycare centers. Spearman's correlation and Mann-Whitney analyses were used to examine the relationships and differences in HCHO and CO2 for varying temperatures, RH values, and categorical indoor environmental factors. There were no significant differences in the HCHO and CO2 air concentrations with varying numbers of children, ventilation times, or ventilation and air cleaning system types. However, both the HCHO and CO2 air concentrations were significantly different for varying RH values, which were divided into five categories (p < 0.001). Only the HCHO air concentrations were significantly different for varying temperatures, which were divided into five categories (p < 0.001). Significant correlations were found between HCHO air concentrations and the temperature (r = 0.35, p < 0.0001), RH (r = 0.51, p < 0.0001), and CO2 (r = 0.36, p < 0.0001). The study results support maintaining an appropriate temperature and RH range for reducing airborne HCHO in daycare centers. Further research is needed to elucidate the precise mechanisms responsible for the relationships observed in this study. IMPLICATIONS: Data from 289 daycare centers in Seoul, South Korea, indicate that HCHO concentrations show a positive correlation with indoor temperature and relative humidity. This indicates that keeping temperatures low will help keep HCHO concentrations low, by both a direct and an indirect effect, since low temperatures also cause low relative humidity.

Monitoring of airborne particulate matter at mountainous urban sites.

Concentrations of various size fractions (TSP, PM10, PM2.5, and PM1.0) of particulate matter (PM) were measured at two mountainous sites, Buk Han (BH) and Gwan AK (GA), along with one ground reference site at Gwang Jin (GJ), located in Seoul, South Korea for the 4 years from 2010 to 2013. The daily average concentrations of TSP, PM10, PM2.5, and PM1.0 at BH were 47.9 ± 32.5, 37.0 ± 24.6, 20.6 ± 12.9, and 15.3 ± 9.53 µg m(-3), respectively. These values were slightly larger than those measured at GA while much lower than those measured at the reference site (GJ). Seasonal variations in PM concentrations were consistent across all locations with a relative increase in concentrations observed in spring and winter. Correlation analysis showed clear differences in PM concentrations between the mountainous sites and the reference site. Analysis of these PM concentrations indicated that the distribution of PM in the mountainous locations was affected by a number of manmade sources from nearby locations, including both traffic and industrial emissions.

Concentrations and identification of culturable airborne fungi in underground stations of the Seoul metro.

The purpose of this study was to measure the culturable airborne fungi (CAF) concentrations in the underground subway stations of Seoul, Korea at two time points. This study measured the CAF concentrations in enclosed environments at 16 underground stations of the Seoul Metro in 2006 and 2013 and investigated the effects of various environmental factors, including the presence of platform screen doors, temperature, relative humidity, and number of passengers. CAF concentrations at the stations in 2006 were significantly higher than that at the same stations in 2013 (p < 0.001). Furthermore, there was a significant correlation between CAF concentration and relative humidity (r = 0.311, p < 0.05). Geotrichum and Penicillium were the predominant genera. The CAF concentrations in stations with an operating supply air were significantly higher than that in stations with no supply air (p < 0.001). Therefore, it is recommended that special attention be given to stations with clean supplied air to improve the indoor air quality of these subway stations.

Evaluation of asbestos-containing products and released fibers in home appliances.

UNLABELLED: The purpose of this study was to detect asbestos-containing products and released asbestos fibers from home appliances. The authors investigated a total of 414 appliances manufactured between 1986 and 2007. Appliances were divided into three categories: large-sized electric appliances, small-sized electric appliances, and household items. Analysis for asbestos-containing material (ACM) was performed using polarized light microscopy (PLM) and stereoscopic microscopy. Air sampling was performed to measure airborne concentration of asbestos using a phase-contrast microscope (PCM). The results of the analysis for ACM in appliances show that large-sized electric appliances (refrigerators, washing machines, kimchi-refrigerators) and household items (bicycles, motorcycles, gas boilers) contain asbestos material and small-sized electric appliances do not contain asbestos material. All appliances with detected asbestos material showed typical characteristics of chrysotile (7-50%) and tremolite (7-10%). No released fibers of ACM were detected from the tested appliances when the appliances were operating. This study gives the basic information on asbestos risk to people who use home appliances. IMPLICATIONS: All appliances with detected asbestos material showed typical characteristics of chrysotile (7-50%) and tremolite (7-10%). No released fibers of ACM were detected from the tested appliances when the appliances were operating.

Seasonal variation in airborne endotoxin levels in indoor environments with different micro-environmental factors in Seoul, South Korea.

This study evaluated the variation over a year in airborne endotoxin levels in the indoor environment of five university laboratories in Seoul, South Korea, and examined the micro-environmental factors that influenced endotoxin levels. These included temperature, relative humidity, CO2, CO, illumination, and wind velocity. A total of 174 air samples were collected and analyzed using the kinetic limulus amebocyte lysate assay. Endotoxin levels ranged from <0.001 to 8.90EU/m(3), with an overall geometric mean of 0.240EU/m(3). Endotoxin levels showed significantly negative correlation with temperature (r=-0.529, p<0.001), CO2 (r=-0.213, p<0.001) and illumination (r=-0.538, p<0.001). Endotoxin levels tended to be higher in winter. Endotoxin levels in laboratories with rabbits were significantly higher than those of laboratories with mice. Multivariate regression analysis showed that the environmental factors affecting endotoxin levels were temperature (coefficient=-0.388, p<0.001) and illumination (coefficient=-0.370, p<0.001). Strategies aimed at reducing airborne endotoxin levels in the indoor environments may be most effective if they focus on illumination.