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Biomedical subjects

W F Sun

Publications and source records attributed to W F Sun.

14 recordsLinked to original sources
PubMed2006

Formation of iodoacetic acids during cooking: interaction of iodized table salt with chlorinated drinking water.

Iodoacetic and chloroiodoacetic acids were formed when municipal chlorinated tap water was allowed to react with iodized (with potassium iodide) table salt or with potassium iodide itself. Iodoacetic acid was recently shown to be a potent cytotoxic and genotoxic agent. For analysis, samples were extracted with t-amyl methyl ether and converted to the corresponding methyl esters using methanol and sulfuric acid. The concentration of iodoacetic acid was determined by gas chromatography-mass spectrometry (GC-MS) using an authentic standard. The identities of iodoacetic and chloroiodoacetic acids were further confirmed by gas chromatography-high-resolution mass spectrometry (GC-HRMS). Certain influences of sodium hypochlorite and humic acid as well as the concentration of potassium iodide on the yields of these acids were investigated. The concentration of iodoacetic acid in tap water samples boiled with 2 g l-1 of iodized table salt was found to be in the 1.5 microg l-1 range, whilst the concentration of chloroiodoacetic acid was estimated to be three to five times lower.

Chlorine↗
PubMed2004

Canadian Total Diet Study in 1998: pesticide levels in foods from Whitehorse, Yukon, Canada, and corresponding dietary intake estimates.

The Canadian Total Diet Study is a national survey to determine the level of chemical contaminants in the Canadian food supply. Food samples were collected from Whitehorse, Yukon, supermarkets as part of the study in 1998. Whitehorse was chosen as a sampling centre, despite its small population (n = 19,000), to determine if residue levels were different in foods available in northern communities relative to levels observed in previous studies in the more populated south. Foods were prepared as for consumption before pesticide residue analysis. Residue levels observed in most foods were similar to levels observed in samples from previous surveys from southern Canadian cities. Malathion and DDE (1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene), a transformation product of DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl(ethane), were the two most frequently detected compounds (26.4 and 25.8%, respectively). The majority of pesticides, however, had a detection frequency of < 5%. In general, pesticides in food composites were well below maximum residue limits established in the Canadian Food and Drug Regulations. Chlorpropham and captan had the highest dietary intakes (2.16 and 1.94 micrograms (kg body weight-day)-1, respectively), based on the results from Whitehorse. No dietary intakes above the acceptable daily intakes, however, were observed for any of the 39 pesticides investigated in any age-sex category, where an acceptable daily intake has been proposed.

Adolescent↗
PubMed2000

Pesticide residues in the Canadian Market Basket Survey--1992 to 1996.

Market basket food samples from six Canadian cities collected from 1992 to 1996 were analysed for pesticide residues. One hundred and thirty-six composites were prepared for each city, representing 99% of the Canadian diet. Residues were found most frequently in peanut butter and butter. DDE, malathion and captan occurred most frequently, while the fungicides chlorothalonil, dicloran and captan were present in the highest concentrations. Processed commodities contained fewer residues and at lower concentrations than the raw products. No residues were detected in either milk or soy-based infant formula. Of the infant foods sampled, fruit contained both the greatest number and highest concentrations of pesticides.

Arachis↗
PubMed1998

Residues of polychlorinated biphenyls (PCB) in fatty foods of the Canadian diet.

Market basket samples representative of food from six Canadian cities were surveyed from 1992 to 1996. Fifty composites of fatty foods, prepared for consumption were analysed for 40 PCB congeners by gas chromatography-mass spectrometry. Fish and butter contained the highest total PCB concentrations, while milk and infant foods contained the lowest. The dairy and meat composites were major contributors to the total PCB intake of 5.7 ng/kg/day, and to the TEQ (2,3,7,8-tetrachloro-p-dibenzodioxin equivalent) intake of 0.11 pg/kg/day. The pattern of congeners was similar for the different food groups with the exception of fish, which contained less tri- and tetra-chlorinated biphenyls and more of the hexachlorinated congener No. 153.

Animals↗
PubMed1993

Elimination of polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) from human blood in the Yusho and Yu-Cheng rice oil poisonings.

The pharmacokinetics of polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) in humans was studied by monitoring the blood concentrations of individuals who ingested a contaminated rice oil in Japan (yusho) in 1968 and in Taiwan (yu-cheng) in 1979. Sixteen yusho patients were followed from 1982 to 1990 and three yu-cheng individuals from 1980 to 1989. From the three yu-cheng patients, blood lipid values for the two persistent toxic congeners, 2,3,4,7,8-pentachlorodibenzofuran (PnCDF) and 1,2,3,4,7,8-hexachlorodibenzofuran (HxCDF), varied from 50 micrograms/kg at first sampling to about 1 micrograms/kg at last sampling corresponding to half-lives for elimination (t1/2) of 2-21/2 years. The blood lipid values for the same PCDF congeners in yusho patients varied from 5 micrograms/kg down to 0.1 micrograms/kg. The calculated t1/2 were more variable with median values closer to 10 years. Planar PCBs #126 and #169 were present at lower concentrations than the PCDFs. For seven of the other PCB congeners, half-lives for elimination in the yu-cheng individuals varied from 1.2 up to 4.6 yr depending on the degree of chlorination. For the yusho patients, the elimination for the PCBs was longer. These results show that clearance of the toxic PCDFs and PCBs in humans is non-linear with faster elimination at higher exposure followed by slower decreases as background levels are approached. Such a clearance pattern can best be explained by a two compartment liver and fat pharmacokinetic model.

Adolescent↗
PubMed1987

The routine analysis of some specific isomers of polychlorinated biphenyl congeners in human milk.

A mixture of 14 polychlorinated biphenyl (PCB) isomers of various congeners, representing approximately 70% of all human milk PCBs reported in the literature, was made up to identify and approximate their residues in human milk. Individual isomer levels varied from 5 to 103 nanograms per gram of milkfat with the 2,2',4,4',5,5'-hexachlorobiphenyl isomer as the major PCB contaminant of human milk. PCB isomer numbers 74, 118, 153, 138 and 180 made up approximately 75% of all PCBs as measured by this mixture. There was close agreement of total PCB isomer content in breast milk between electron capture gas chromatography and gas chromatographic mass spectrometry determinations. A major interference was encountered however for PCB isomer no. 52, whose residue level in the breast milk was approximately 3 X higher by gas liquid chromatography than by mass spectrometry.

Canada↗
PubMed1987

[Heart injuries].

Explore the source record for details and available documents.

Cardiac Tamponade↗
PubMedDate not supplied

Levels and trends of chlorinated hydrocarbon contaminants in the breast milk of Canadian women.

A total of 210 breast milk samples from 5 different regions across Canada were analyzed for polychlorinated biphenyls (PCBs), hexachloro-1,3-butadiene, ten chlorinated benzenes, two chlorinated naphthalenes, Mirex, photomirex, alpha, beta and gamma hexachlorocyclohexane, alpha and gamma chlordane, oxychlordane, trans-nonachlor, p,p'-DDT and some analogs, heptachlor epoxide, dieldrin and octachlorostyrene. There was no evidence for the presence of hexachloro-1,3-butadiene, Mirex, octachlorostyrene, chlorinated naphthalenes or tetrachlorobenzenes in the breast milk. Residues of other compounds were found in all samples, except 1,2-dichlorobenzene, gamma hexachlorocyclohexane, alpha and gamma chlordane and p,p'-TDE, which were less frequently observed, while o,p'-DDT was only found in approximately one quarter of all samples. Since 1967, a steady decline in heptachlor epoxide, dieldrin and p,p'-DDT and related residues is apparent. At the same time however, there is an apparent increase in PCB residue levels since 1970. This apparent increase should be viewed with some caution, since much of this increase might be attributed to better sampling and analytical techniques. Residue levels of breast milk in Canada were similar to those found in other industrial nations. Regional differences in residue levels appeared to be minimal.

Canada↗
PubMedDate not supplied

Application of capillary gas chromatography to a survey of wheat for five trichothecenes.

A previously published method for the determination of deoxynivalenol (DON) and nivalenol (NIV) in grains by capillary gas chromatography (GC) with electron-capture detection (ECD) has been modified to include HT-2 toxin (HT-2), T-2 toxin (T-2) and diacetoxyscirpenol (DAS). Recoveries of the five trichothecenes from wheat averaged 71-92% in the range 0.8-4 micrograms/g. Detection or quantitation limits found in two laboratories were from 0.02 to 0.4 micrograms/g, with those for T-2 and DAS at the high end of this range. The method proved of practical use in survey work for the screening and determination of these trichothecenes in wheat from the 1987 western Canadian crop. There were no false positives for HT-2, T-2 and DON in durum and HY-320 wheat. However, interferences precluded the determination of 4- and 15-monoacetoxyscirpenol (MAS) by GC-ECD. The natural occurrence of HT-2 toxin (0.06-0.59 micrograms/g) was demonstrated by GC-ECD and confirmed by GC-mass spectrometry (MS) in 23 samples of durum and HY-320 wheats (1986 and 1987 crops); it was almost always accompanied by DON and in one sample a low concentration of NIV (0-05 micrograms/g). False positives for HT-2 and DAS in red spring wheat detected in 1987 by GC-ECD were 6% (nearly all identified as variety Katepwa) and 8%, respectively. Hence confirmation of suspected HT-2 and DAS by GC-MS is necessary, particularly with red spring wheat.

Chromatography, Gas↗
PubMedDate not supplied

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in human milk samples collected across Canada in 1986-87.

Monitoring of human milk samples for the presence of chemical contaminants has been carried out in Canada for several decades. In 1986-87 over 400 donations of human milk were collected nationwide and 100 of these, selected by province according to population, were analysed for the PCDDs/PCDFs. The results show the presence of about eleven different analytes all with 2,3,7,8-substitution with the PCDDs at higher and more variable concentrations than the PCDFs. On a 2,3,7,8-TCDD toxic equivalents (TEQ) basis, the mean value for the country is about 15 ng per kg milk fat. This TEQ value is similar to that from many other industrialized nations and about 50% lower than certain European states. Little or no variation was apparent in the milk content among the various Canadian provinces probably reflecting the uniformity of the general food supply across the country. Limited data over a period of five years suggest the average level of these compounds in human milk may be decreasing.

Benzofurans↗
PubMedDate not supplied

Speciation of organotins in poly(vinyl chloride) products.

Extraction studies on butyl- and octyltins were conducted with three poly(vinyl chloride) (PVC) product types: clear food container, rigid pipe and flexible membrane. Three solvents, tetrahydrofuran, xylene and methylene chloride were evaluated for extraction efficiency. Methylene chloride extracted more than 97% of the total extractable organotin in two extractions and resulted in the highest recoveries of analytes from all three PVC products. Method detection limits ranged from 0.3 to 0.9 microgram alkyltin/g PVC. The mean precision of the method is 6.8% relative standard deviation. Food industry PVC product samples contained between < 0.8 and 8751 micrograms/g octyltins and < 0.3 and 4.7 micrograms/g butyltins. Butyltins (< 0.9-5985 micrograms/g) were detected in potable water pipe samples. Pipe used in industrial applications contained both butyl- (13-1501 micrograms/g) and octyltins (701-3033 micrograms/g).

Food Contamination↗
PubMedDate not supplied

Survey of organotin compounds in blended wines.

An extraction method for butyltin, cyclohexyltin, octyltin and phenyltin compounds in wines was developed using 0.05% tropolone in 75% diethyl ether/pentane. Recoveries averaged 96.8% (range 78-121%). Methyl derivatives made by Grignard reaction were quantitated by gas chromatography (GC)-atomic absorption spectrometry (AAS). Twenty-nine of the 90 samples (32.2%) tested contained at least one of the analytes. Mono- and diocyltin were found in one sample only, at levels of 2.41 and 0.12 ng/ml respectively. Dibutyltin levels ranged from < 0.08 to 1.44 ng/ml. Monobutyl and tributyltin were found less frequently and at lower levels than dibutyltin. GC/mass spectrometric analysis confirmed the presence of butyl- and octyltins. No other organotin compounds were detected by either GC-AAS or GC-MS.

Gas Chromatography-Mass Spectrometry↗
PubMedDate not supplied

Analysis of total free and glucose-conjugated pyrethroid acid metabolites in tea infusions as hexafluoroisopropyl esters by gas chromatography with electron capture detection.

A gas chromatographic method with electron capture detection (GC-ECD) has been developed to quantitate the sum of free acids of pyrethroid metabolites, their glucosides, and their other base-cleavable conjugates that are extracted from tea leaves when a tea infusion is prepared. Four representative glucoside conjugates were synthesized; hydrolytic conditions were established; and extraction, derivatization and GC conditions were developed for analysis of these pyrethroid acid metabolites at > or = 0.01 ppm on dry tea. GC/mass spectrometry was used to confirm assignment of residues found in some tea samples.

Chromatography, Gas↗