Hoon Choi

Determination of toxic heavy metals and speciation of arsenic in seaweeds from South Korea

This study aimed at determining the levels of toxic heavy metals including As, Pb, Cd, Al, Hg and As species, such as, As-III, As-V, MMA, DMA, AsB, and AsC in various edible species of seaweeds from South Korea. ICP-MS was used for determination of As, Pb and Cd, ICP-OES was used for Al, DMA was used for Hg, and LC-ICP-MS was used for As speciation. The analytical methods were validated by linearity, detection limits, precision, accuracy and recovery experiments, obtaining satisfactory results in all cases. From the results toxic heavy metals were found in the decreasing order of: Al>As>Pb-Cd>Hg. Generally concentrations of all analysed heavy metals and both organic and inorganic species of As were very low compared to PTWIs specified by JECFA and EC. Their contribution to the overall intake by the subject seafoods was found very low and thus would not pose any threat to consumers.

Operative Outcomes of Robotic Partial Nephrectomy: A Comparison with Conventional Laparoscopic Partial Nephrectomy

Purpose To determine the feasibility and safety of robotic partial nephrectomy (RPN), we compared the operative outcomes of patients who had undergone RPN with those of patients who had undergone laparoscopic partial nephrectomy (LPN). Materials and Methods Between February 2009 and June 2010, 13 patients underwent transperitoneal RPN (group 1) and 14 patients underwent transperitoneal LPN (group 2) by a single surgeon. The operative outcomes of the 2 groups were compared by using Mann-Whitney U and Fishers exact tests. Results All cases were completed successfully without conversion to open surgery. The mean operative time was 153.2±22.3 and 117.5±32.0 minutes in groups 1 and 2, respectively (p=0.003). The mean robotic console time of group 1 was 101.2±21.5 minutes, and the mean laparoscopic time of group 2 was 86.8±32.3 minutes (p=0.139). The mean warm ischemic time was 35.3±8.5 minutes and 36.4±6.8 minutes in groups 1 and 2, respectively (p=0.823). The mean estimated blood loss was 283.6±113.5 ml and 264.1±163.7 ml (p=0.382), respectively. The mean length of hospital stay was 6.1 and 5.3 days (p=0.290), respectively. The mean tumor size was 2.7±1.2 cm and 2.0±1.2 cm (p=0.035), respectively. The surgical margins were negative in all cases. Conclusions Although the operative time of RPN was longer than that of LPN, there were no significant differences in operative outcomes including robotic console time and laparoscopic time between the procedures.

Determination of toxic heavy metals in Echinodermata and Chordata species from South Korea

This study aimed at analysing concentrations of heavy metals including arsenic, lead, cadmium, aluminium and mercury in commonly consumed seafood species belonging to Echinodermata (Anthocidaris crassispina and Stichopus japonicus) and Chordata (Halocynthia roretzi and Styela plicata). The samples were digested by a microwave system and analysed for As, Cd and Pb by inductively coupled plasma mass spectrometer, for Al by inductively coupled plasma-optical emission spectrometer and Hg by Direct Mercury Analyser. The analytical method was validated by determining sensitivity, linearity, precision, spiking recoveries and analysis of the Standard Reference Material (SRM) NIST 1566-b, an Oyster Tissue. Results showed considerably higher accumulation of Al and As in analysed samples, compared to Pb and Cd, while Hg had the lowest contamination. On comparison, the obtained results with the recommended standards by the Food and Agriculture Organization, European Commission and Ministry of Food and Drug Safety of Korea, it was concluded that the analysed seafoods were safe and thus would not pose a threat to consumers.

Speciation of Arsenic in Rice by High-Performance Liquid Chromatography–Inductively Coupled Plasma Mass Spectrometry

ABSTRACT This study reports the optimization and validation of arsenic speciation of rice. Total arsenic was determined by inductively coupled plasma mass spectrometry; arsenite, arsenate, monomethylarsonic acid, and dimethyarsinic acid were quantified by high-performance liquid chromatography–inductively coupled plasma mass spectrometry. Methods using nitric acid and malonic acid were validated at various extraction conditions and mobile phase systems. The linear dynamic range, limit of detection, precision, fortification, and analysis of a white rice flour certified reference material (CRM-7503-a) were evaluated for quality assurance. The use of 5 mM malonic acid for extraction with an isocratic mobile phase was optimized for extraction time and temperature and employed for arsenic speciation in rice. The concentrations of total arsenic, arsenite, arsenate, monomethylarsonic acid, and dimethyarsinic acid were low compared to the provisional tolerable weekly intakes specified by the Food and Agriculture Organization/World Health Organization Joint Expert Committee on food additives and European food safety authority and thus do not pose a threat to consumers.

Analysis of cyazofamid and its metabolite in the environmental and crop samples using LC-MS/MS.

A rapid and robust LC–MS/MS method for the analysis of cyazofamid and its metabolite, 4-chloro-5-p-tolylimidazole-2-carbonitrile (CCIM), in environmental samples (soil and water) and a variety of crops (apple, mandarin, Kimchi cabbage, green pepper, potato and soybean) was established in this study. Those compounds were analyzed by selected reaction monitoring with electrospray ionization (positive mode) on LC–MS/MS. Method limit of quantitations were 2xa0ngxa0g−1 (cyazofamid) and 5xa0ngxa0g−1 (CCIM) for soil/crop samples, while 0.02xa0ngxa0mL−1 (cyazofamid) and 0.05xa0ngxa0mL−1 (CCIM) were achieved for water samples. Matrix effect (%) was different depending on sample matrices. For recovery tests, soil/crop samples were treated with QuEChERS method and water samples were extracted with dichloromethane. The recoveries of target analytes in the environmental and crop samples were 80.2xa0%–105.1xa0% for cyazofamid and 75.1xa0%–99.1xa0% for CCIM (coefficients of variation; ≤16.4xa0%).

Risk Assessment of Arsenic in Agricultural Products

The present study was carried out to assess exposure & risk for Korean by total and inorganic As intake through agricultural products. Total arsenic analysis was performed using microwave device and ICP-MS. 50% MeOH extraction and anion-exchange HPLC-ICP-MS method has been used to determine arsenic species. 329 samples covering 20 kinds of agricultural products were collected from various retail outlets and markets across Korea. The concentration of total As was in the range of 0.001~0.718 mg/kg, while inorganic and organic arsenic species in all samples was not determined. For risk assessment, probable daily intake was calculated and compared with provisional tolerable weekly intake (PTWI, 15 /kg b.w./week for inorganic arsenic) established by JECFA. The median daily exposure to total and inorganic As by intake of agricultural products except rice was ranged 0.0002~0.012, 0.0001~0.001 /kg b.w./day, corresponding to 0.01~0.5%, 0.002~0.1% of PTWI, respectively. The median level of total and inorganic As intake through rice was 0.603 and 0.041 /kg b.w./day, and 28.1% and 1.9% of PTWI, respectively. Therefore, the level of overall exposure to arsenic for Korean through agricultural products was below the recommended JECFA levels, indicating of least possibility of risk.

Antifungal and antiaflatoxigenic effects of a fumigant, ethanedinitrile, on Aspergillus flavus

Antifungal effects of ethanedinitrile (EDN) and ethyl formate (EF) on Aspergillus flavus were investigated using radial growth bioassay. A. flavus was inoculated in the center of potato dextrose agar plate and treated with 1, 5, and 10xa0g/m3 of EDN, or 5, 35, and 70xa0g/m3 of EF. EDN strongly inhibited fungal growth. At 1xa0g/m3 of EDN, the fungal growth reduced by 22.2% by the final days of culture. The growth was completely inhibited by EDN at the concentration of 5xa0g/m3. Antiaflatoxigenic activity of both the fumigants was also assessed. Aflatoxin formation was determined using high-performance liquid chromatography with a fluorescence detector. A. flavus did not produce aflatoxin B1 and aflatoxin B2 at EDN concentrations >5xa0g. EF had no inhibitory effect on A. flavus growth and the formation of aflatoxin. These results suggest that EDN can be an alternative for currently used antifungal agents to control fungal and aflatoxin contamination of stored grains.

Determination of toxic heavy metal levels in commonly consumed species of shrimp and shellfish using ICP-MS/OES

Toxic metal concentrations, including lead (Pb), cadmium (Cd), aluminum (Al), mercury (Hg), and arsenic (As) in edible tissues of different species of shrimp and shellfish consumed in South Korea were analyzed. Analysis was performed using inductively coupled plasma (ICP)-MS) for Pb, Cd and As, ICP-optical emission spectrometry (OES) for Al, and a direct mercury analyzer for Hg. Methods used were validated. Limited variation in heavy metal concentrations between shrimp and shellfish were observed. Al and As concentrations were highest while Hg was lowest. Heavy metal levels found in edible tissues of shellfish and shrimp were below international and local maximum permissible levels for human consumption. The methods used were accurate and reproducible for use in determination of toxic heavy metal levels in seafoods.

Prostate-Specific Antigen Density as a Powerful Predictor of Extracapsular Extension and Positive Surgical Margin in Radical Prostatectomy Patients with Prostate-Specific Antigen Levels of Less than 10 ng/ml.

Purpose To assess the ability of preoperative variables to predict extracapsular extension (ECE) and positive surgical margin (PSM) in radical prostatectomy patients with prostate-specific antigen (PSA) levels of less than 10 ng/ml. Materials and Methods From January 2008 to December 2009, 121 patients with prostate cancer with PSA levels lower than 10 ng/ml who underwent radical prostatectomy were enrolled in the study. The differences in clinical factors (age, PSA, PSA density [PSAD], digital rectal examination [DRE] positivity, positive magnetic resonance imaging [MRI], Gleason sum, positive core number, and positive biopsy core percentage) with ECE and the presence of positive margins were determined and their independent predictive significances were analyzed. Results The ECE-positive patients had higher PSA, PSAD, and MRI-positive percentages, and PSM patients had higher PSA, PSAD, MRI-positive percentages, Gleason sum, and positive biopsy core percentages for prostate cancer. In the multivariate analysis, PSAD and MRI positivity were the best independent predictors for ECE, and PSA and PSAD were the best independent predictors of PSM. By receiver operating characteristic curve analysis, PSAD had better discriminative area under the curve value than did PSA for ECE (0.765 vs 0.661) and PSM (0.780 vs 0.624). The best predictive PSAD value was 0.29 ng/ml/cc for ECE and 0.27 ng/ml/cc for PSM. Conclusions PSAD has relevance to ECE (plus MRI findings) and PSM (plus PSA). PSAD might be a powerful predictor of ECE and PSM preoperatively in patients undergoing a radical prostatectomy with PSA levels of less than 10 ng/ml.

RADIATION DOSE DISTRIBUTION FOR WORKERS IN SOUTH KOREAN NUCLEAR POWER PLANTS

A total of 33 680 nuclear power plants (NPPs) workers were monitored and recorded from 1990 to 2007. According to the record, the average individual radiation dose has been decreasing continually from 3.20 mSv man(-1) in 1990 to 1.12 mSv man(-1) at the end of 2007. After the International Commission on Radiological Protection 60 recommendation was generalised in South Korea, no NPP workers received >20 mSv radiation, and the numbers of relatively highly exposed workers have been decreasing continuously. The age distribution of radiation workers in NPPs was composed mainly of 20-30 y olds (83 %) for 1990-1994 and 30-40 y olds (75 %) for 2003-2007. The difference in individual average dose by age was not significant. Most (77 %) of the NPP radiation exposures from 1990 to 2007 occurred mostly during the refueling period. With regard to exposure type, the majority of exposures was external exposures, representing 95 % of the total exposures, whereas internal exposures represented only 5 %. External effective dose was affected mainly by gamma radiation exposure, with an insignificant amount of neutron exposure. As for internal effective dose, tritium in the pressurised heavy water reactor was the biggest cause of exposure.