This study quantitatively evaluated the impact of revamping projects on air pollutant emissions. Data from five municipal solid waste incineration (MSWI) facilities in Korea were measured by the Tele-Monitoring System (TMS) from 2011 to 2024. Concentration, total emissions, and emission factors (EF, kg/ton-waste) before and after the revamping process were compared, and each specific pollutant reduction per ton (ΔEF) was estimated, along with the associated environmental benefits. After the revamping process, waste treatment capacity increased by 8.7~29.2%, while both concentrations and emission factors of dust, NOx, and HCl decreased, indicating higher performance even in the larger treatment conditions. The societal benefit of revamping these facilities was estimated to amount to approximately 6.6 thousand KRW per ton of waste, with NOx accounting for more than 80% of the total benefit. Although HCl emission levels were relatively low, HCl reduction is environmentally beneficial due to its strong odor and corrosive properties, indicating a potential improvement in the mitigation of public complaints as well as a positive environmental impact. This research provides one of the case studies for long-term measurement-based assessments of revamping effects and may serve as fundamental data for waste management policy, societal benefits, and strategic decision-making for future MSWI refurbishment and planning.

This study investigated residual aerosol characteristics and airborne transmission risk in a classroom associated with a COVID-19 cluster outbreak. Field experiments were conducted in an actual language institute classroom where a cluster infection occurred in 2021. The research focused on the possibility of time-shift airborne exposure caused by residual aerosols remaining after the conclusion of class. Dropletlike particle experiments were performed under actual classroom operating conditions consisting of a 55-minute class period and a 5-minute break period. Aerosol behavior and concentration changes were analyzed under two conditions: opening the door and natural cross-ventilation through simultaneous opening of windows and doors. The results showed that approximately 74% of the droplet-like particles remained in the classroom after the 5-minute break period when only the door was opened. Based on the measured residual aerosol concentration, the airborne infection risk estimated using the Wells-Riley model was 29.31%. In contrast, under natural ventilation conditions, the infection risk decreased to 3.04%, demonstrating significant aerosol removal and risk reduction effects. These findings suggest that limited ventilation during short break periods may be insufficient to remove residual aerosols in educational facilities, while natural cross-ventilation can effectively reduce airborne transmission risk associated with residual aerosols.

This study evaluated the effectiveness of a roadside air quality monitoring network in one of Gyeonggi Province’s emerging cities, focusing on traffic volume and air pollutants. It showed that while the network reflected high correlations of NO2 and CO with vehicular emissions, PM10 and PM2.5 were more influenced by citywide air quality. The atmospheric concentration of O3 was linked to air temperature and solar radiation, confirming the role of meteorological and photochemical factors. Temporal analysis indicated that traffic-related pollutants partly reflected traffic flow but could not be fully explained by volume alone. Stepwise statistical methods, including Pearson correlation, multiple linear regression, and generalized additive models, revealed nonlinear behaviors beyond conventional models. Comparisons between roadside and urban background stations such as AQMS showed high correlations of PM10 and PM2.5 across networks, while NO2 and CO were more localized to roadside emissions. It is necessary to effectively achieve the purpose of roadside monitoring networks by conducting a more comprehensive and in-depth investigation into their effectiveness in various metropolitan cities where they are being installed.

Radon (222Rn) is the leading environmental cause of lung cancer among nonsmokers. Additionally, schools are critical exposure environments because children spend over 2,000 hours annually in school settings and are more vulnerable than adults. Although various mitigation systems are increasingly being installed in Korean schools, quantitative comparisons of their performance under a unified protocol have been lacking. This study evaluated four types of mitigation systems installed across 19 schools nationwide: active soil depressurization (ASD), ceiling-type (CT), window-type (WT), and floor-standing (FS) mechanical ventilators. Furthermore, three complementary methods were used: long-term alpha-track monitoring (approximately 90 days, two seasons) and short-term continuous monitoring with FRD-400 detectors (three rounds) in all 19 schools. A controlled sealed-condition evaluation during winter break was also conducted in a subset of eight schools (15 measurement points). Indoor radon concentrations were significantly higher in the second half of the year (155.7 ± 169.2 Bq/m3) than in the first half (82.1 ± 48.2 Bq/m3), corresponding to an approximately 1.9- fold seasonal increase (p < 0.01). Daytime concentrations were on average 57% lower than nighttime concentrations under natural ventilation conditions, but remained above the recommended limit (148 Bq/m3) in high-concentration schools. Mean reduction efficiencies were 74.9% for ASD, 55.4% for CT, 40.4% for WT, and 41.4% for FS. While ASD maintained on-condition concentrations below the recommended limit across the entire off-condition range (33.5~611.5 Bq/m3), on-condition concentrations under the three mechanical ventilation systems consistently remained above the recommended limit when off-condition concentrations exceeded approximately 400 Bq/ m3. These findings are consistent with the high-concentration range identified in the U.S. EPA school radon guideline (EPA, 1994), where ventilation alone is insufficient to maintain concentrations below the recommended limit. The results also provide the first quantitative observations of this concentration-dependent limit from Korean school classrooms, offering quantitative grounds for concentration-dependent selection of mitigation systems.

This study analyzed the causes of indoor radon in school classrooms in Chungcheongbuk-do, South Korea, and evaluated the reduction efficiency of various air purification devices. From January to September 2021, indoor radon concentrations were continuously measured for approximately eight days at 30 schools located in 10 administrative districts. The results were interpreted in conjunction with soil radon concentrations and the geological characteristics of each region. The mean indoor radon concentration of the 30 schools in summer was 88.2 ± 42.2 Bq/m3, with a maximum of 201.1 Bq/m3 at Goesan B and a minimum of 29.4 Bq/m3 at Jecheon B. Three schools (Goesan B, Goesan C, and Danyang B) exceeded the management standard of 148 Bq/m3. Time-of-day analysis showed that radon concentrations were relatively low during occupied daytime hours (08:00~17:00) and increased again during nighttime hours (18:00~07:00). On weekends, when natural ventilation was minimal, radon accumulated continuously, resulting in initial Monday morning concentrations approximately twice those of other weekdays. The mean radon reduction efficiency of mechanical ventilators was 22.5%, and floor-type ventilators (mean 20.1%) were more effective than ceilingtype ventilators (mean 15.3%). When the same mechanical ventilators were operated alone, the mean CO2 reduction efficiency across 23 schools was 17.3% (range 1.5~33.1%). Soil radon concentrations averaged 23,844 Bq/m3 across 10 regions and were highest in areas where the parent rock was metamorphic or acidic igneous rock (Goesan, Yeongdong, and Chungju). Although based on a single school, the high reduction efficiency observed with a soil depressurization system (ASD, 65.7%) suggests that, for classrooms with chronically high radon driven primarily by soil gas intrusion, ASD may be considered a priority option. Meanwhile, mechanical ventilation can be applied to classrooms that exceed the standard but cannot be managed through natural ventilation alone. The results provide quantitative evidence to support regionspecific radon management strategies for schools in Chungcheongbuk-do.

This study quantified the precipitation effect on residential odor complaints in a megacity (Seoul, South Korea). A total of 134,936 residential odor complaint records (2,922 days; 2014~2021) were subjected to Box-Cox transformation to attenuate the influence of extreme events. The inlier range, representing typical residential odor complaint levels, was determined to range from 4 to 191 cases/day (107,956 cases; 2,740 days). The precipitation effect on air pollutants was concurrently evaluated and benchmarked against previously reported values to validate the quantitative approach. After excluding days with yellow dust advisories (105,658 cases; 2,681 days), data were stratified into rainy (28,878 cases; 764 days) and non-rainy (28,878 cases; 764 days) periods. Optimal regression equations were derived from temporal variations in residential odor complaints and air pollutants (PM10, PM2.5, NOX, CO, O3, and SO2) across air temperature intervals delineated using Sturges’ rule. These equations were integrated over the temperature range (–1.9~28.1oC) to quantify the precipitation effect. The precipitation effect on air pollutants, expressed as percentage reductions (minimum~maximum), was 23.1% (21.2~74.9) for PM10, 19.8% (18.5~78.1) for PM2.5, 17.7% (17.6~72.1) for NOX, 12.3% (7.8~50.5) for SO2, 9.4% (7.3~63.4) for O3, and 8.7% (5.6~45.7) for CO. Although numerical deviations from prior estimates were observed, a consistent trend was evident. The precipitation effect on residential odor complaints was 14.2% (8.1~88.1%). Compared with air pollutants, residential odor-causing substances (predominantly gas-phase, 14.2%) exhibited a lower precipitation effect than particulate matter but a higher value than SO2 (12.3%) and lower than NOX (17.7%). Nonetheless, the maximum precipitation effect on residential odor complaints (88.1%) exceeded the maximum values for all examined air pollutants (PM10, PM2.5, NOX, CO, O3, and SO2). These findings suggest that residential odor-causing substances, -heterogeneous gas-phase compounds with physicochemical properties dependent on emission source characteristics, -can achieve high scavenging efficiency when water-soluble components dominate. This behavior may inform targeted management strategies for specific emission sources or regions.

This study evaluated changes in volatile organic compounds (VOCs) concentrations and health risks under three residential winter scenarios: no air purifier operation (S1), fixed air purifier operation (S2), and IoT-based mobile air purifier operation (S3). VOC reduction effects and non-carcinogenic and carcinogenic risks were compared. Some VOCs, including benzene and 1,2,4-trimethylbenzene, decreased under air purifier operation compared with S1. Benzene concentrations in S3 were approximately 19.6% lower than in S2. The proportions satisfying S2/S1 < 1.0 and S3/S1 < 1.0 were 29.1% and 40.7%, respectively. This indicates a greater reduction tendency in S3, particularly in spaces without fixed purifiers, such as kitchens, studies, and general rooms. The exceedance rates of the hazard index (HI) threshold were 83.8%, 83.4%, and 39.3% for S1, S2, and S3, respectively. This represents an approximately 53% lower non-carcinogenic risk exceedance in S3. For carcinogenic risk, the excess cancer risk (ECR) of 2-propenenitrile in S3 decreased by 86.7% and 85.8% at the 50th percentile and by 55.4% and 63.3% at the 90th percentile, compared with S1 and S2, respectively. Although total ECR exceeded the acceptable level in all scenarios, S3 showed 46.9% and 46.2% lower values at the 50th percentile than S1 and S2. Overall, IoT-based mobile air purifier operation reduced VOC concentrations and mitigated health risks by targeting rooms with elevated pollution levels using roomspecific indoor air pollution information.

This study evaluated the sterilization efficacy of gas fumigation as an environmentally friendly and effective method for microbial control in archival document disinfection. Considering the challenges associated with disinfecting archival materials and environmental concerns related to conventional chemical disinfectants, an ethylene oxide-based mixed fumigant was used to assess its bactericidal efficacy against harmful microorganisms on paper surfaces. Five bacterial species inoculated onto six different paper types were examined by comparing microbial survival before and after fumigation. Complete (100%) microbial inactivation was achieved immediately after fumigation and was maintained for at least 1-2 weeks following treatment. These results demonstrate that gas fumigation using an ethylene oxide-based mixed fumigant is an effective and safe disinfection method for the preservation of archival materials.