MeeKyung Kim

Photodegradation of polychlorinated dibenzo-p-dioxins and dibenzofurans in aqueous solutions and in organic solvents

Aqueous solutions of selected polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were prepared using a generator column and exposed to UV (300 nm) light in the laboratory and to sunlight in an outdoor environment. In the laboratory, additional exposures were also carried out using 60% acetonitrile/water solutions. At 300 nm di- and tetra PCDDs had higher first-order photodegradation rate constants in 60% acetonitrile/water than in pure water. The solvent effect was reversed for PCDFs. These results may be a reflection of the higher polarity of PCDFs compared to PCDDs. In both the indoor and outdoor exposures photodegradation rates decreased with increasing concentrations of chlorination. However, OCDF exposed to 300 nm light in 60% acetonitrile/water and to sunlight in pure water photodegraded more rapidly than tetra CDF. Photolysis rates in sunlight were considerably slower (t(1/2) of 6.4-23 h) than photolysis rates at 300 nm in the laboratory (t(1/2) of 4.3-680 min), reflecting the lower intensity of sunlight in the 300 nm region of the UV/Vis spectrum. The extent of dechlorination of the PCDDs/PCDFs was less than 20% and reductive dechlorination does not appear to be a major process in the photodegradation of PCDDs/PCDFs in aqueous solutions.

Development and verification for analysis of pesticides in eggs and egg products using QuEChERS and LC-MS/MS.

QuEChERS method was applied and validated for the multi-residue analysis of pesticides in eggs and egg products. The method includes extraction with buffered acetonitrile and clean-up with dispersive sorbents, followed by LC-MS/MS analysis. The validation parameters were used based on the guideline of SANCO/12495/2011. Recoveries were within the range of 71-108%, and the relative standard deviations were 2-13% at the 3 different concentrations evaluated for eggs and egg products. The limits of quantification for the target compounds ranged from 0.3 to 6 ng/g. Monitoring of 100 domestic eggs and 50 imported egg products were performed to verify the adaptability in real samples. No samples contained residues exceeding the maximum residue limit (MRL). Carbendazim, dimethoate, and pirimicarb were each found in egg yolks at the level of 2 ng/g, in the same sample, well below their MRLs of 50-100 ng/g.

Formation of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) from a refinery process for zinc oxide used in feed additives: A source of dioxin contamination in Chilean pork

The Republic of Korea found dioxin at concentrations exceeding the Korean maximum residue limit (MRL) in pork (2 pg TEQ g(-1) fat) imported from Chile in June 2008. Korea and Chile collaborated and investigated to find out the sources of contamination. An isotope dilution method and high resolution gas chromatography/mass spectrometry (HR-GC/MS) were used for the analysis of PCDD/Fs. PCDD/Fs were found from 2.17 to 36.7 pg TEQ g(-1) fat from Chilean pork. 2,3,4,7,8-PeCDF, 1,2,3,4,7,8-HxCDF, 1,2,3,6,7,8-HxCDF, and 2,3,4,6,7,8-HxCDF were found as the major congeners in pork samples. 2,3,4,7,8-PeCDF showed the highest concentration and contributed about 30% among the congeners in most of the samples. 2,3,7,8-TCDD, 1,2,3,7,8,9-HxCDD, OCDD, 2,3,7,8-TCDF, 1,2,3,7,8-PeCDF, 1,2,3,7,8,9-HxCDF, and OCDF were not detected or exist at background levels in the less contaminated samples. Remarkably high concentrations of PCDD/Fs were found in samples of zinc oxide (17147 pg TEQ g(-1)), zinc oxide based premix (6673 pg TEQ g(-1)), and the residue crust (800 pg TEQ g(-1)) in a mixing chamber in the feed mill. From the results of various investigations, this case concluded that zinc oxide in the feed was the major source of the dioxin contamination in pork. The dioxins were formed from a metal refinery process to collect zinc oxide.

Cadmium and lead in animal tissue (muscle, liver and kidney), cow milk and dairy products in Korea

ABSTRACT A survey of Cd and Pb in animal tissue, milk and dairy products was conducted. Muscle, liver and kidney of domestically produced cows, pigs, chickens and ducks were collected from eight regions in Korea. Raw cow milk was collected from 9 regions, and imported dairy products (butter, cheese, cream and powdered milk) were collected from 15 countries. Cd and Pb were analysed by inductively coupled plasma mass spectrometry (ICP-MS) after microwave digestion. Concentrations of Cd and Pb did not exceed the Korean legal maximum levels in any of the samples. Correlation coefficients were estimated between concentration of Cd or Pb and animal age and between muscle, liver and kidney. In cows, there were good correlations between age and Cd in kidney (r = 0.748) and between Cd in liver and in kidney (r = 0.878). Continuous monitoring will be an important role to safeguard consumers in the event of a food contamination incident.

Concentrations of PCDD/Fs, dioxin-like PCBs, PBDEs, and hexachlorobenzene in fat samples from cattle of different ages and gender in Korea.

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenyls (DL-PCBs), polybrominated diphenyl ethers (PBDEs), and hexachlorobenzene (HCB) concentrations were determined in abdominal fat samples from 30 cattle. The relationships between chemicals, age, and gender were investigated. The concentration of PCDD/Fs ranged from 0.01 to 1.36 pg TEQ g(-1) fat, DL-PCBs ranged from 0.17 to 1.64 pg TEQ g(-1) fat, PBDEs ranged from 135 to 725 pgg(-1) fat, and HCB ranged from 25.5 to 2061 pgg(-1) fat. A comparison between cattles age and gender vs. the concentration of contaminants revealed higher concentrations of PCDD/Fs and DL-PCBs in cattle aged more than 3 years; no difference between genders was apparent. Moreover, the concentrations of PBDEs in cattle fat did not correspond with the age of cattle. Relative to cattle 1.5-2.5 years of age, cattle aged 3 and 4 years had higher concentration of HCB but the concentration difference was not clear at age 5. Human exposures to these compounds from beef sources were calculated based on beef consumption.

Determination of phthalates in raw bovine milk by gas chromatography/time-of-flight mass spectrometry (GC/TOF-MS) and dietary intakes

Low levels of phthalates, including di(2-ethylhexyl) phthalate (DEHP), in raw bovine milk were determined using gas chromatography/time-of-flight mass spectrometry (GC/TOF-MS). A fast and convenient process of sample treatment combined with TOF-MS analysis (medium resolution >5000), yielded good recoveries (85–125%) and low limits of detection (<0.002 mg kg−1). The most commonly used phthalate, DEHP, was found in 15 out of 30 samples monitored in this study. DEHP concentrations in raw milk ranged from not detected to 0.154 mg kg−1, and the mean concentration was 0.057 mg kg−1. The dietary intake of DEHP was about 0.004 mg kg−1 body weight day−1 if a child (24 months, 13 kg body weight) drinks 1 L day−1 of milk that contains the mean concentration of DEHP found in raw milk. The estimated dietary intake corresponded to 8% of the European Union tolerable daily intake (TDI) of 0.05 mg kg−1 body weight day−1. Dimethyl phthalate (DMP) and di-n-butyl phthalate (DBP) were found from two and 20 samples, respectively, at low levels. Diethyl phthalate (DEP), butylbenzyl phthalate (BBP), and di-n-octyl phthalate (DnOP) were not found in any of the samples.

Chemical Residues and Contaminants in Foods of Animal Origin in Korea during the Past Decade

Residues of veterinary drugs, pesticides, and environmental contaminants in domestic and imported foods of animal origin were monitored by the National Residue Program and inspection service in Korea in the past decade. In all, 134 substances were analyzed in the monitoring plan; 35 substances were examined in the surveillance and enforcement testing program, and 27 substances were investigated in exploratory projects. The overall trend of violation rates gradually decreased over the past decade. Pesticides were not found in any domestic samples of animal origin. The violation rates of chlortetracycline and oxytetracycline decreased, but quinolone and penicillin detections increased in Korea. Several kinds of residue violations of veterinary drugs, endosulfan, or dioxins were found in the imported products each year. In an example event in 2008, the Korea monitoring plan contributed globally to investigate the dioxin contamination from Chilean pork. Continuous monitoring based on internationally harmonized standards and methods provides the essential scientific basis to manage and ensure food safety.

Monitoring of environmental contaminants in raw bovine milk and estimates of dietary intakes of children in South Korea.

Persistent organic pollutants (POPs) are ubiquitous residual contaminants in the environment and in the food chain. Milk is an important matrix for monitoring POP contamination. This study determined the concentrations of POPs including polybrominated diphenyl ethers (PBDEs), hexachlorobenzene (HCB), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and dioxin-like polychlorinated biphenyls (DL-PCBs) in raw bovine milk, and the data was used to estimate dietary intakes in South Korea. The average concentrations of PBDEs, HCB, PCDD/Fs, and DL-PCBs in raw milk were 0.29 ng g(-1)fat, 0.50 ng g(-1)fat, 0.27 pg TEQ g(-1)fat, and 0.33 pg TEQ g(-1)fat, respectively. No significant relationship was found between the concentrations of analytes and the regions sampled. The dietary intakes of PBDEs from the consumption of milk was calculated to be 0.26, 0.10, and 0.05ng kg(-1)bwd(-1) for the group of ages 0-6, 7-12, and 13-19, respectively. The dietary intakes of HCB was calculated to be 0.44, 0.16, and 0.09 ng kg(-1)bwd(-1) for the group of ages 0-6, 7-12, and 13-19, respectively. The dietary intakes of PCDD/Fs and DL-PCBs was calculated to be 0.78, 0.29, and 0.16pgTEQ kg(-1)bwd(-1) for the group of ages 0-6, 7-12, and 13-19, respectively. These results indicated that the residual levels of PBDEs, HCB, PCDD/Fs, and DL-PCBs in raw bovine milk were within safe levels.

Safety assessment of 16 sweeteners for the Korean population using dietary intake monitoring and poundage method

ABSTRACT A sweetener is a food additive that imparts a sweet taste to food products. Sweeteners have been increasingly used in Korea since the approval of sodium saccharin and d-sorbitol in 1962. Unlike food contaminants, humans are exposed to food additives only through the consumption of processed food products. For exposure assessments of sweeteners, the dietary intakes of food products containing acesulfame-K, aspartame, saccharin-Na, and sucralose were determined, and the resulting calculated estimated daily intake (EDI) values were compared directly with each additive’s ADI. The poundage method was used to calculate the daily intake per capita for 12 additional sweeteners, such as lactitol, for which appropriate analytical methods for food products do not exist. The risk, as evaluated by comparing the EDI with the ADI, was determined to be 2.9% for acesulfame-K, 0.8% for aspartame, 3.6% for saccharin-Na, 4.3% for steviol glycosides, and 2.1% for sucralose. No hazardous effect was predicted for the other 11 sweeteners, including lactitol.

Simultaneous Determination of Aminoglycoside Antibiotics in Meat using Liquid Chromatography Tandem Mass Spectrometry

A simultaneous determination was developed for 9 aminoglycoside antibiotics (amikacin, apra- mycin, dihydrostreptomycin, gentamicin, hygromycin B, kanamycin, neomycin, spectinomycin, and streptomycin) in meat by liquid chromatography tandem mass spectrometry (LC-MS/MS). Each parameter was established by multiple reaction monitoring in positive ion mode. The developed method was validated for specificity, linearity, accuracy, and precision based on CODEX validation guideline. Linearity was over 0.98 with calibration curves of the mixed stan- dards. Recovery of 9 aminoglycosides ranged on 60.5~114% for beef, 60.1~112% for pork and 63.8~131% for chicken. The limit of detection (LOD) and limit of quantification (LOQ) were 0.001~0.009 mg/kg and 0.006~ 0.03 mg/kg, respectively in livestock products including beef, pork and chicken. This study also performed survey of residual aminoglycoside antibiotics for 193 samples of beef, pork and chicken collected from 9 cities in Korea. Ami- noglycosides were not found in any of the samples.