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Bucheon, South Korea

Ha M.,Dankook University | Kwon H.-J.,Dankook University | Leem J.-H.,Inha University | Kim H.-C.,Inha University | And 12 more authors.
International Journal of Hygiene and Environmental Health | Year: 2014

For the first nationwide representative survey on the environmental health of children and adolescents in Korea, we designed the Korean Environmental Health Survey in Children and Adolescents (KorEHS-C) as a two-phase survey and planned a sampling strategy that would represent the whole population of Korean children and adolescents, based on the school unit for the 6-19 years age group and the household unit for the 5 years or less age group. A pilot study for 351 children and adolescents aged 6 to 19 years in elementary, middle, and high school of two cities was performed to validate several measurement methods and tools, as well as to test their feasibility, and to elaborate the protocols used throughout the survey process. Selected exposure biomarkers, i.e., lead, mercury, cadmium in blood, and bisphenol A, metabolites of diethylhexyl phthalate and di-n-butyl phthalate and cotinine in urine were analyzed. We found that the levels of blood mercury (Median: 1.7 ug/L) and cadmium (Median: 0.30 ug/L) were much higher than those of subjects in Germany and the US, while metabolites of phthalates and bisphenol A showed similar levels and tendencies by age; the highest levels of phthalate metabolites and bisphenol A occurred in the youngest group of children. Specific investigations to elucidate the exposure pathways of major environmental exposure need to be conducted, and the KorEHS-C should cover as many potential environmental hazards as possible. © 2013 Elsevier GmbH. Source

Hong S.,Seoul National University | Kwon H.-O.,Ulsan National Institute of Science and Technology | Choi S.-D.,Ulsan National Institute of Science and Technology | Lee J.-S.,NeoEnBiz Co | Khim J.S.,Seoul National University
Marine Pollution Bulletin | Year: 2016

Water, suspended particulate matter (SPM), and biota samples were collected from the Taehwa River Estuary to determine the distributions, partitioning, and bioaccumulation of arsenicals. Six forms of As were quantitated by the use of HPLC-ICP/MS. As was found mainly near urban and industrial areas, and inorganic AsV was the predominant As form in both water and SPM. Particulate arsenicals were found at the greatest concentrations in coarse particles (>180μm), followed by medium (30-180μm) and fine (0.45-30μm) particles, in freshwater. Arsenical concentrations were similar across the three particle fractions in saltwater. Field-based distribution coefficient (Kd) values for As depended strongly on SPM, with a less robust dependence on salinity. Concentrations of As were greater in macroalgae than in marine animals, such as fishes, bivalves, crabs, shrimps, and gastropods. Overall, the results of the present study provide useful information on the behaviors and fate of arsenicals in an estuarine environment. © 2016 Elsevier Ltd. Source

Yoon D.,Sogang University | Lee D.,Hankuk University of foreign Studies | Lee J.-H.,NeoEnBiz Co | Cha S.,Hankuk University of foreign Studies | Oh H.B.,Sogang University
Rapid Communications in Mass Spectrometry | Year: 2015

RATIONALE Quantifying polymers by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) with a conventional crystalline matrix generally suffers from poor sample-to-sample or shot-to-shot reproducibility. An ionic-liquid matrix has been demonstrated to mitigate these reproducibility issues by providing a homogeneous sample surface, which is useful for quantifying polymers. In the present study, we evaluated the use of an ionic liquid matrix, i.e., 1-methylimidazolium α-cyano-4-hydroxycinnamate (1-MeIm-CHCA), to quantify polyhexamethylene guanidine (PHMG) samples that impose a critical health hazard when inhaled in the form of droplets. METHODS MALDI-TOF mass spectra were acquired for PHMG oligomers using a variety of ionic-liquid matrices including 1-MeIm-CHCA. Calibration curves were constructed by plotting the sum of the PHMG oligomer peak areas versus PHMG sample concentration with a variety of peptide internal standards. RESULTS Compared with the conventional crystalline matrix, the 1-MeIm-CHCA ionic-liquid matrix had much better reproducibility (lower standard deviations). Furthermore, by using an internal peptide standard, good linear calibration plots could be obtained over a range of PMHG concentrations of at least 4 orders of magnitude. CONCLUSIONS This study successfully demonstrated that PHMG samples can be quantitatively characterized by MALDI-TOFMS with an ionic-liquid matrix and an internal standard. Copyright © 2014 John Wiley & Sons, Ltd. Source

Kim H.-S.,Sungkyunkwan University | Park J.-W.,Sungkyunkwan University | Park S.-M.,Sungkyunkwan University | Lee J.-S.,NeoEnBiz Co | Lee Y.-Z.,Sungkyunkwan University
Wear | Year: 2013

In order to develop an eco-friendly lubricant, nanodiamonds were selected and added to a paraffin liquid by a matrix synthesis method. This method can maintain good dispersibility without cohesion and avoid precipitation for an extended period of time. The lubricity of dispersed oils with different amounts of nanodiamond particles was compared using both constant load and step loading on ball-on-disk type tests. Friction characteristics, wear amount, and scuffing life were determined. During the tests, the temperatures of oils were monitored in order to verify the heat dispersion rates of oils that contained nanodiamond. Several hypotheses are presented to explain the results of this work. By the addition of nanodiamond particles, the coefficient of friction may have been reduced due to their octagonal, almost spherical shape which can act as rolling contact elements between two surfaces. Also, it is proposed that nanodiamond can support the load between two sliding surfaces because of its high hardness value. Because the nanodiamond has the ability to disperse the generated frictional heat, it leads to increase the scuffing life. © 2013 Elsevier B.V. Source

Kang C.S.,KEPCO E&C | Lee J.-H.,NeoEnBiz Co | Kim S.-K.,NeoEnBiz Co | Kim S.-K.,Seoul National University | And 10 more authors.
Chemosphere | Year: 2010

Fetal and maternal exposure levels of two emerging pollutants, polybrominated diephenyl ethers (PBDEs) and synthetic musks, were measured in Korean general population to assess prenatal and postnatal exposures in infants. For this purpose, paired samples of breast milk, maternal and cord blood were collected from 20 Korean women in 2007. In comparison to data from other countries and previous data from Korea, relatively higher and gradually increasing concentrations for PBDEs were found in Korean breast milk ( Source

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