Indoor air quality and its determinants in underground shopping malls in Korea.

Underground shopping malls (USMs) are often open or semi-open environments with interconnected passageways, resulting in the sharing of indoor air. However, indoor air quality (IAQ) within these spaces can vary due to many diverse emission sources. We investigated the relationships between IAQ and geographical areas, as well as IAQ and store types, within USMs, in Korea. In 2020, we studied 10 different USMs, with a total of 128 outlets. We conducted comprehensive IAQ assessments (including measurements of fine particles (PM2.5), aldehydes, and volatile organic compounds (VOCs)) in stores, passages, and outdoor areas. The stores were categorized into three types: clothing, fashion accessories, and food services. Additionally, we measured environmental factors such as CO2 levels and presence of storefront walls. PM2.5 levels were higher outdoors, whereas aldehyde and VOC levels exhibited elevations within passages and the interior of stores than in the outdoor environment. The store-to-passage ratios for PM2.5, individual aldehydes, and VOC concentrations ranged from 1.06 to 4.93. Formaldehyde and total VOC (TVOC) concentrations were found to be elevated in clothing and fashion accessory stores, whereas PM2.5 concentrations were more prominent in food service establishments. Specific individual compounds, including propionaldehyde, hexaldehyde, benzene, n-heptane, toluene, n-octane, xylene, d-limonene, n-undecane, n-dodecane, and ethylbenzene concentrations exhibited associations with store types. Multivariate regression models demonstrated positive associations between most aldehydes and VOCs with CO2 concentrations and presence of storefront walls. This study underscored variations within USMs based on area and store type. Aldehyde and VOC concentrations were notably higher in clothing and fashion accessory stores than in food service outlets; these elevations were closely linked to CO2 levels and presence of storefront walls. These findings suggest that monitoring CO2 levels within USM stores, optimizing air-conditioning systems, and designing future stores without storefront walls can collectively contribute to an overall improvement of IAQ within USMs.

Characterization of urinary cotinine concentrations among non-smoking adults in smoking and smoke-free homes in the Korean national environmental health survey (KoNEHS) cycle 3 (2015-2017).

BACKGROUND: Although many indoor public places have implemented smoke-free regulations, private homes have remained sources of tobacco smoke pollutants. This study examined differences in urinary cotinine concentrations in the Korean non-smoking adult population between living in smoking and smoke-free homes, and the relationship of urinary cotinine concentrations with socio-demographic factors in smoke-free homes. METHODS: Samples from 2575 non-smoking adults (≥19 years old) in the Korean National Environmental Health Survey cycle 3 (2015-2017), a representative Korean study, were used. Smoking and smoke-free homes were defined based on whether there were smokers at homes. Weighted linear regression models were used to determine urinary cotinine concentrations and identify factors associated with urinary cotinine. RESULTS: The geometric mean of urinary cotinine concentrations for non-smoking adults living in smoking homes was 2.1 µg/L (95% confidence interval [CI] = 1.8-2.4), which was significantly higher than the mean of 1.3 µg/L (95% CI = 1.2-1.4) for those living in smoke-free homes. Urinary cotinine concentrations were different significantly by home smoking status in most socio-demographic subgroups. Data from smoke-free home showed urinary cotinine concentration in adults was significantly higher in those who lived in homes with ventilation duration < 30 min/day, those who spent more time indoors at home, those who spent less time outdoors, and those who worked in non-manual or manual occupations. CONCLUSIONS: The urinary cotinine concentration in Korean non-smoking adults living in smoking homes was higher than that in adults living in smoke-free homes. Even in smoke-free homes, home-related factors, such as ventilation duration and time spent indoors, were associated with urinary cotinine concentration. Further study is warranted to examine potential sources of tobacco smoke pollution in smoke-free homes.

Volatile Organic Compounds in Underground Shopping Districts in Korea.

Underground shopping districts (USDs) are susceptible to severe indoor air pollution, which can adversely impact human health. We measured 24 volatile organic compounds (VOCs) in 13 USDs throughout South Korea from July to October 2017, and the human risk of inhaling hazardous substances was evaluated. The sum of the concentrations of the 24 VOCs was much higher inside the USDs than in the open air. Based on factor analysis, six indoor air pollution sources were identified. Despite the expectation of a partial outdoor effect, the impacts of the indoor emissions were significant, resulting in an indoor/outdoor (I/O) ratio of 5.9 and indicating elevated indoor air pollution. However, the effects of indoor emissions decreased, and the contributions of the pollution sources reduced when the USD entrances were open and the stores were closed. Although benzene, formaldehyde, and acetaldehyde exhibited lower concentrations compared to previous studies, they still posed health risks in both indoor and outdoor settings. Particularly, while the indoor excess cancer risk (ECR) of formaldehyde was ~10 times higher than its outdoor ECR, benzene had a low I/O ratio (1.1) and a similar ECR value. Therefore, indoor VOC concentrations could be reduced by managing inputs of open air into USDs.

PM2.5 and Trace Elements in Underground Shopping Districts in the Seoul Metropolitan Area, Korea.

We measured PM2.5 in 41 underground shopping districts (USDs) in the Seoul metropolitan area from June to November 2017, and associated 18 trace elements to determine the sources and assess the respiratory risks. The PM2.5 concentrations were 18.0 ± 8.0 µg/m3 inside USDs, which were lower than 25.2 ± 10.6 µg/m3 outside. We identified five sources such as indoor miscellanea, soil dust, vehicle exhaust/cooking, coal combustion, and road/subway dust, using factor analysis. Almost 67% of the total trace element concentration resulted from soil dust. Soil dust contribution increased with the number of stores because of fugitive dust emissions due to an increase in passers-by. Vehicle exhaust/cooking contribution was higher when the entrances of the USDs were closed, whereas coal combustion contribution was higher when the entrances of the USDs were open. Although miscellanea and coal combustion contributions were 3.4% and 0.7%, respectively, among five elements with cancer risk, Cr and Ni were included in miscellanea, and Pb, Cd, and As were included in coal combustion. The excess cancer risk (ECR) was the highest at 67 × 10-6 for Cr, and the ECR for Pb was lower than 10-6, a goal of the United States Environmental Protection Agency for hazardous air pollutants.

Pore Parameters-Dependent Adsorption Behavior of Volatile Organic Compounds on Graphene-Based Material.

Mesoporous graphenes (MPGs) with interpenetrating porous networks are successfully obtained by the pyrolysis of composite gel consisting of graphite oxide (GO) and the amphiphilic triblock copolymer (Pluronic P123) under Ar atmosphere, wherein P123 is used as a soft-template. The as-prepared composite gel is obtained following self-assembly and freeze-drying. The obtained MPGs have high BET specific surface area (531-746 m2 g-1 and ink-bottle like pores with three dimensional interconnected network. Furthermore, the specific surface area and porous parameters such as pore volume, pore size, and pore size distribution of MPGs can be rationally controlled by regulating the initial mass ratio of P123 to GO. With the increase of P123 ratio, the average mesopore size is decreased from ∼16.4 nm to ∼9.5 nm, which is similar to the diameter size of P123 micelles. Also, the adsorption capacities of MPG-20 for 52 indoor air standard components (100 µg mL-1, Supelco) are compared with two different materials, namely commercial porous polymers (2,6-diphenyleneoxide) and reduced graphene oxide (RGO). The result shows that MPG-20 has significantly better adsorption capacity than RGO but also similar or slightly better than commercial porous polymer. The mesoporous structure and surface chemistry of MPGs were the most important factors for the enhancement of the adsorption efficiency for volatile organic compounds.

Direct synthesis and bonding origins of monolayer-protected silver nanocrystals from silver nitrate through in situ ligand exchange.

In this study, we attempt to present a direct synthesis of narrowly dispersed silver nanoparticles in a highly concentrated organic phase (>2 M) without the use of a size-selection process. The fully organic phase system contains silver nitrate as a silver precursor, n-butylamine as a medium dissolving the silver salt, dodecanoic acid as a capping molecule, toluene as a medium, and NaBH4 as a reducing reagent. Even using only generic chemicals, monodisperse silver nanocrystals with a size of 7 nm were easily synthesized on the 100-g scale in a 1-L reactor. In addition, systematic studies revealed that the silver nanocrystals synthesized through in situ ligand exchange were stabilized through bidentate bridging of carboxyl groups in dodecanoic acid.