Kweon Jung

Isolation and characterization of a tetrachloroethylene dechlorinating bacterium, Clostridium bifermentans DPH-1

A tetrachloroethylene (PCE)-degrading gram-positive, endospore forming, anaerobic bacterium, strain DPH-1, was isolated from a contaminated site. The organism was identified as Clostridium bifermentans by 16S rRNA gene sequence analysis and based on its physiological characteristics. Strain DPH-1 could dechlorinate high concentrations of PCE (0.9 mM), via trichloroethylene (TCE) to cis-1,2-dichloroethylene (cDCE) at a rate of 0.43 micromol/h.mg protein, as well as a number of other halogenated aliphatic compounds.

Characterization of Fine Particulate Matter and Associations between Particulate Chemical Constituents and Mortality in Seoul, Korea

Background: Numerous studies have linked fine particles [≤ 2.5 µm in aerodynamic diameter (PM2.5)] and health. Most studies focused on the total mass of the particles, although the chemical composition of the particles varies substantially. Which chemical components of fine particles that are the most harmful is not well understood, and research on the chemical composition of PM2.5 and the components that are the most harmful is particularly limited in Asia. Objectives: We characterized PM2.5 chemical composition and estimated the effects of cause-specific mortality of PM2.5 mass and constituents in Seoul, Korea. We compared the chemical composition of particles to those of the eastern and western United States. Methods: We examined temporal variability of PM2.5 mass and its composition using hourly data. We applied an overdispersed Poisson generalized linear model, adjusting for time, day of week, temperature, and relative humidity to investigate the association between risk of mortality and PM2.5 mass and its constituents in Seoul, Korea, for August 2008 through October 2009. Results: PM2.5 and chemical components exhibited temporal patterns by time of day and season. The chemical characteristics of Seoul’s PM2.5 were more similar to PM2.5 found in the western United States than in the eastern United States. Seoul’s PM2.5 had lower sulfate (SO4) contributions and higher nitrate (NO3) contributions than that of the eastern United States, although overall PM2.5 levels in Seoul were higher than in the United States. An interquartile range (IQR) increase in magnesium (Mg) (0.05 μg/m3) was associated with a 1.4% increase (95% confidence interval: 0.2%, 2.6%) in total mortality on the following day. Several components that were among the largest contributors to PM2.5 total mass—NO3, SO4, and ammonium (NH4)—were moderately associated with same-day cardiovascular mortality at the p < 0.10 level. Other components with smaller mass contributions [Mg and chlorine (Cl)] exhibited moderate associations with respiratory mortality on the following day (p < 0.10). Conclusions: Our findings link PM2.5 constituents with mortality and have implications for policy making on sources of PM2.5 and on the relevance of PM2.5 health studies from other areas to this region.

Long-Term Fine Particulate Matter Exposure and Major Depressive Disorder in a Community-Based Urban Cohort.

Background: Previous studies have associated short-term air pollution exposure with depression. Although an animal study showed an association between long-term exposure to particulate matter ≤ 2.5 μm (PM2.5) and depression, epidemiological studies assessing the long-term association are scarce. Objective: We aimed to determine the association between long-term PM2.5 exposure and major depressive disorder (MDD). Methods: A total of 27,270 participants 15–79 years of age who maintained an address within the same districts in Seoul, Republic of Korea, throughout the entire study period (between 2002 and 2010) and without a previous MDD diagnosis were analyzed. We used three district-specific exposure indices as measures of long-term PM2.5 exposure. Cox proportional hazards models adjusted for potential confounding factors and measured at district and individual levels were constructed. We further conducted stratified analyses according to underlying chronic diseases such as diabetes mellitus, cardiovascular disease, and chronic obstructive pulmonary disease. Results: The risk of MDD during the follow-up period (2008–2010) increased with an increase of 10 μg/m3 in PM2.5 in 2007 [hazard ratio (HR) = 1.44; 95% CI: 1.17, 1.78], PM2.5 between 2007 and 2010 (HR = 1.59; 95% CI: 1.02, 2.49), and 12-month moving average of PM2.5 until an event or censor (HR = 1.47; 95% CI: 1.14, 1.90). The association between long-term PM2.5 exposure and MDD was greater in participants with underlying chronic diseases than in participants without these diseases. Conclusion: Long-term PM2.5 exposure increased the risk of MDD among the general population. Individuals with underlying chronic diseases are more vulnerable to long-term PM2.5 exposure. Citation: Kim KN, Lim YH, Bae HJ, Kim M, Jung K, Hong YC. 2016. Long-term fine particulate matter exposure and major depressive disorder in a community-based urban cohort. Environ Health Perspect 124:1547–1553; http://dx.doi.org/10.1289/EHP192

Degradation of a variety of halogenated aliphatic compounds by an anaerobic mixed culture

Abstract We investigated the biodegradation of tetrachloroethylene (perchloroethylene, PCE) and halogenated aliphatic compounds by using anaerobic mixed cultivation. The mixed culture degraded PCE at concentrations of up to 150 mg/ l in 40 d via trichloroethylene (TCE) to cis -1,2-dichloroethylene (cDCE). Small amounts of vinyl chloride (VC) and CO 2 were also detected. The same culture degraded various halogenated aliphatic compounds such as cDCE, VC, 1,2-dichloroethane (DE), 1,3-dichloropropene (DP), dichloromethane (DM), 1,1,2-trichloroethane (TE), and chloroform (CF). Acetate was the most effective electron donor for dechlorination, although formate, glucose and lactate were also effective, but to a lesser extent. The mixed culture degraded PCE in the temperature range 25 to 43°C, with an optimum between 30 and 37°C, and the pH range of 6.2 to 11.0.

The effect of man made source processes on the behavior of total gaseous mercury in air: A comparison between four urban monitoring sites in Seoul Korea

Concentrations of total gaseous mercury (TGM) were measured continuously at four urban residential locations (G (Guro-gu); N (Nowon-gu); S (Songpa-gu); and Y (Yongsan-gu)) in Seoul, Korea from 2004 to 2009. The mean concentrations of Hg at these sites were found on the order of N (3.98±1.68 ng m(-3)), S (3.87±1.56 ng m(-3)), G (3.80±1.60 ng m(-3)), and Y (3.36±1.55 ng m(-3)). Evidence indicates that the spatial distribution of Hg should be affected by the combined effects of both local anthropogenic (incineration facilities and thermal power plants) and natural (soil) emission sources in association with the meteorological parameters. Inspection of the Hg temporal patterns indicates the co-existence of contrasting seasonal patterns between the central site Y (winter dominance) and all other outbound sites near city borders (summer dominance). The long-term trend of Hg, if examined by combining our previous studies and the present one, shows that Hg levels in this urban area declined gradually across decadal periods despite slight variabilities in spatial scale: (1) above 10 ng m(-3) in the late 1980s, (2) ~5 ng m(-3) in the late 1990s, and (3) ~3 ng m(-3) toward the late 2000s. The results of the principal component analysis along with observed differences in seasonal patterns (between study sites) suggest that Hg distributions between different urban sites are greatly distinguishable with strong source signatures at each individual site.

Behavior of particulate matter during high concentration episodes in Seoul

The behavior of particulate matter (PM) during high-concentration episodes was investigated using monitoring data from Guui station, a comprehensive air monitoring station in Seoul, Korea, from January 2008 to March 2010. Five non-Asian dust (ND) episodes and two Asian dust (AD) episodes of high PM concentrations were selected for the study. During the ND episode, primary air pollutants accumulated due to low wind speeds, and PM2.5 increased along with most other air pollutants. Particles larger than PM2.5 were also high since these particles were generated by vehicular traffic rather than wind erosion. During strong AD episodes, PM10–2.5 primarily increased and gaseous primary air pollutants decreased under high wind speeds. However, even during the AD episode, PM2.5 and gaseous primary air pollutants increased when the effects of AD were weak and wind speeds were low. This study corroborates that accumulation of air pollutants due to a drop in surface wind speed plays an important role in short-term high-concentration occurrences. However, low wind speeds could not be directly linked to local emissions because a significant portion of accumulated air pollutants resulted from long-range transport.

Peroxyacetyl nitrate (PAN) in the urban atmosphere

Peroxyacetyl nitrate (PAN) in air has been well known as the indicator of photochemical smog due to its frequent occurrences in Seoul metropolitan area. This study was implemented to assess the distribution characteristics of atmospheric PAN in association with relevant parameters measured concurrently. During a full year period in 2011, PAN was continuously measured at hourly intervals at two monitoring sites, Gwang Jin (GJ) and Gang Seo (GS) in the megacity of Seoul, South Korea. The annual mean concentrations of PAN during the study period were 0.64±0.49 and 0.57±0.46 ppb, respectively. The seasonal trends of PAN generally exhibited dual peaks in both early spring and fall, regardless of sites. Their diurnal trends were fairly comparable to each other. There was a slight time lag (e.g., 1 h) in the peak occurrence pattern between O3 and PAN, as the latter trended to peak after the maximum UV irradiance period (16:00 (GJ) and 17:00 (GS)). The concentrations of PAN generally exhibited strong correlations with particulates. The results of this study suggest that PAN concentrations were affected sensitively by atmospheric stability, the wet deposition of NO2, wind direction, and other factors.

Emission Rate of Particulate Matter and Its Removal Efficiency by Precipitators in Under-Fired Charbroiling Restaurants

In order to explore the potent role of meat cooking processes as the emission sources of particulate matter (PM), emission rates and the associated removal efficiency by precipitators were estimated based on the on-site measurements made at five under-fired charbroiling (UFC) restaurants. The emission patterns of PM for these five restaurants were compared after having been sorted into the main meat types used for cooking: beef (B), chicken (C), intestines (I), and pork (P: two sites). The mass concentrations (μg m-3) of three PM fractions (PM2.5/PM10/TSP) measured from these restaurants were 15,510/15,701/17,175 (C); 8,525/10,760/12,676 (B); 11,027/13,249/13,488 (P); and 22,409/22,412/22,414 (I). Emission factors (g kg-1) for those PM fractions were also estimated as 3.23/4.08/4.80 (B), 3.07/3.82/3.87 (P), 8.12/8.22/8.99 (C), and 6.59/6.59/6.59 (I). If the annual emission rate of PM10 is extrapolated by combining its emission factor, population, activity factor, etc., it is estimated as 500 ton year-1, which corresponds to 2.4% of the PM10 budget in Seoul, Korea. Removal efficiencies of PM10 via precipitators, such as an electrostatic precipitator (ESP), bag filter (BF), and the combination system (ESP + catalyst), installed in those UFC restaurants ranged between 54.76 and 98.98%. The removal efficiency of PM by this control system was the least effective for particles with <0.4 μm, although those in the range of 0.4–10 μm were the most effective.

Monitoring heavy metals, residual agricultural chemicals and sulfites in traditional herbal decoctions

BackgroundAsian traditional herbal preparations are frequently considered for the contamination with undeclared toxic or hazardous substances. The aim of this study was to determine the toxic heavy metals, pesticides and sulfur dioxide in decoctions that is a common form of final utilization in Korea.MethodsA total of 155 decoctions composed of multi-ingredient traditional herbs were randomly sampled from Seoul in Korea between 2013 and 2014. For each decoction, the concentrations of four heavy metals (arsenic, cadmium, lead and mercury), 33 pesticides and sulfur dioxide were analyzed using inductively coupled plasma mass spectrometry (ICP-MS), mercury analyzer, gas chromatography/nitrogen phosphorous detector (GC/NPD), gas chromatography/micro electron capture detector (GC/μECD), and Monier-Williams method respectively.ResultsOne hundred fifty-two of One hundred fifty-five decoctions (98.1%) contained one of three heavy metals (96.1% for As, 97.4% for Cd, and 90.3% for Pb, 0.0% for Hg). Their average concentrations (77.0 ± 79.7 ug/kg for As, 20.4 ± 23.7 ug/kg for Cd, and 68.8 ± 76.5 ug/kg for Pb) were approximately 20% of the maximum allowable limits of vegetable or ginseng beverage described in the Korean Food Standard Codex while their 95th percentile concentrations were below than the guideline for them. None of 33 pesticides was detected in 155 decoction samples, and only one sample showed over limit of detection for residual sulfites.ConclusionsThis study support that the contained status of toxic heavy metals, pesticides and sulfur dioxide in herbal decoctions are currently within safe level in Korea, and provide a reference data for the further studies focused on the safety herbal preparations.

Transfer rates of toxic metals during decoction preparation from hebal medicines and safety evaluation of the final decoction products

Transfer rates of toxic metals during herbal decoction preparation were investigated using risk assessment tools. Decoction samples were analyzed using Inductively Coupled Plasma-Mass Spectrometer (ICP-MS) and a mercury analyzer after microwave digestion. The average decoction transfer rate (%) for each toxic metal after boiling was 10.5 for As, 4.3 for Pb, 4.1 for Cd, and 2.7 for Hg. A risk assessment of toxic metals in decoctions was performed based on the percentage provisional tolerable weekly intake (PTWI) values for a mean value scenario and a 95th percentile value scenario. Samples were collected of 68 decoctions representing 8 types frequently prescribed by oriental medicine clinics in Seoul, Korea. Both scenarios demonstrated low PTWI values. All decoction samples were safe according to risk assessment results.