Last data update: Sep 16, 2024. (Total: 47680 publications since 2009)
Records 1-6 (of 6 Records) |
Query Trace: Bishop AM [original query] |
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Novel exposure biomarkers of N,N-diethyl-m-toluamide (DEET): Data from the 2007-2010 National Health and Nutrition Examination Survey
Calafat AM , Baker SE , Wong LY , Bishop AM , Morales AP , Valentin-Blasini L . Environ Int 2016 92-93 398-404 BACKGROUND: N,N-diethyl-m-toluamide (DEET) is a widely used insect repellent in the United States. OBJECTIVES: To assess exposure to DEET in a representative sample of persons 6years and older in the U.S. general population from the 2007-2010 National Health and Nutrition Examination Survey. METHODS: We analyzed 5348 urine samples by using online solid-phase extraction coupled to isotope dilution-high-performance liquid chromatography-tandem mass spectrometry. We used regression models to examine associations of various demographic parameters with urinary concentrations of DEET biomarkers. RESULTS: We detected DEET in ~3% of samples and at concentration ranges (>0.08mug/L-45.1mug/L) much lower than those of 3-(diethylcarbamoyl)benzoic acid (DCBA) (>0.48mug/L-30,400mug/L) and N,N-diethyl-3-hydroxymethylbenzamide (DHMB) (>0.09mug/L-332mug/L). DCBA was the most frequently detected metabolite (~84%). Regardless of survey cycle and the person's race/ethnicity or income, adjusted geometric mean concentrations of DCBA were higher in May-Sep than in Oct-Apr. Furthermore, non-Hispanic whites in the warm season were more likely than in the colder months [adjusted odds ratio (OR)=10.83; 95% confidence interval (CI), 3.28-35.79] and more likely than non-Hispanic blacks (OR=3.45; 95% CI, 1.51-7.87) to have DCBA concentrations above the 95th percentile. CONCLUSIONS: The general U.S. population, including school-age children, is exposed to DEET. However, reliance on DEET as the sole urinary biomarker would likely underestimate the prevalence of exposure. Instead, oxidative metabolites of DEET are the most adequate exposure biomarkers. Differences by season of the year based on demographic variables including race/ethnicity likely reflect different lifestyle uses of DEET-containing products. |
On-line solid phase extraction-high performance liquid chromatography-isotope dilution-tandem mass spectrometry approach to quantify N,N-diethyl-m-toluamide and oxidative metabolites in urine
Kuklenyik P , Baker SE , Bishop AM , Morales AP , Calafat AM . Anal Chim Acta 2013 787 267-73 Human exposure to N,N-diethyl-m-toluamide (DEET) occurs because of the widespread use of DEET as an active ingredient in insect repellents. However, information on the extent of such exposure is rather limited. Therefore, we developed a fast on-line solid phase extraction-high performance liquid chromatography-isotope dilution tandem mass spectrometry (HPLC-MS/MS) method to measure in urine the concentrations of DEET and two of its oxidative metabolites: N,N-diethyl-3-(hydroxymethyl)benzamide and 3-(diethylcarbamoyl)benzoic acid (DCBA). To the best of our knowledge, this is the first HPLC-MS/MS method for the simultaneous quantification of DEET and its select metabolites in human urine. After enzymatic hydrolysis of the conjugated species in 0.1mL of urine, the target analytes were retained and pre-concentrated on a monolithic column, separated from each other and from other urinary biomolecules on a reversed-phase analytical column, and detected by atmospheric pressure chemical ionization in positive ion mode. The limits of detection ranged from 0.1ngmL(-1) to 1.0ngmL(-1), depending on the analyte. Accuracy ranged between 90.4 and 104.9%, and precision ranged between 5.5 and 13.1% RSD, depending on the analyte and the concentration. We tested the usefulness of this method by analyzing 75 urine samples collected anonymously in the Southeastern United States in June 2012 from adults with no known exposure to DEET. Thirty eight samples (51%) tested positive for at least one of the analytes. We detected DCBA most frequently and at the highest concentrations. Our results suggest that this method can be used for the analysis of a large number of samples for epidemiological studies to assess human exposure to DEET. |
Quantification of riboflavin in human urine using high performance liquid chromatography-tandem mass spectrometry
Bishop AM , Fernandez C , Whitehead Jr RD , Morales AP , Barr DB , Wilder LC , Baker SE . J Chromatogr B Analyt Technol Biomed Life Sci 2011 879 (20) 1823-6 We developed a selective method to measure riboflavin in human urine. Sample preparation involved solid phase extraction and concentration of the target analyte in urine. The urine concentrate was analyzed using high performance liquid chromatography-tandem mass spectrometry. Riboflavin concentrations were quantified using an isotopically labeled internal standard. The limit of detection was 11ng/mL, and the linear range was 4.4-20,000ng/mL. The relative standard deviation at 100, 1000, and 5000ng/mL was 17%, 17%, and 12%, respectively. The accuracy was 90%. On average, 100 samples, including calibration standards and quality control samples, were prepared per day. Using our method, we measured concentrations of riboflavin in human urine samples that were collected from participants in a study where riboflavin was used as a surrogate chemical to simulate exposure to an environmental toxicant. |
Variability of urinary concentrations of bisphenol A in spot samples, first-morning voids, and 24-hour collections
Ye X , Wong LY , Bishop AM , Calafat AM . Environ Health Perspect 2011 119 (7) 983-8 BACKGROUND: Human exposure to bisphenol A (BPA) is widespread. After exposure, BPA is rapidly metabolized and eliminated in urine. Therefore, there is considerable within- and between-person variability of BPA concentrations in spot urine samples. However, no information exists on the within-day variability of urinary BPA concentrations. OBJECTIVES: We examined the between- and within-person and between- and within-day variability in the urinary BPA concentrations of eight adults who collected all voids for 1 week to investigate the impact of sampling strategy in the exposure assessment of BPA using spot, first morning, or 24-hour urine collections. METHODS: We determined the urinary concentrations of BPA using on-line solid-phase extraction coupled to isotope dilution-high-performance liquid chromatography-tandem mass spectrometry. RESULTS: The between-day/within-person variability was the primary contributor to the total variance both for first-morning voids (77 %) and 24-hr urine collections (88 %). For the spot collections, we observed considerable within-day variance (70 %), which outweighed the between-person (9 %) and between-day/within-person (21 %) variances. CONCLUSIONS: Regardless of the type of void (spot, first morning, 24-hour collections), urinary BPA concentrations for a given adult changed considerably-both within a day and among the 7 days of the study period. Single 24 hour urine collections accurately reflect daily exposure, but can misrepresent variability in daily exposures over time. Of interest, when the population investigated is sufficiently large and samples are randomly collected relative to meal ingestion times and bladder emptying times, the single spot sampling approach may adequately reflect the population's average exposure to BPA. |
Does the composition of urine change when collected from disposable diapers and other absorbent materials?
Ye X , Zhou X , Bishop AM , Needham LL , Calafat AM . J Expo Sci Environ Epidemiol 2010 20 (7) 644-9 The free and conjugated urinary species of non-persistent environmental chemicals or their breakdown products are valid human exposure biomarkers. For convenience, disposable diapers and other absorbent materials are widely used to collect urine specimens from infants and young toddlers. However, the extent to which the different urinary species of the target analytes and other components are recovered after the urine is extracted from these absorbent materials is unknown. In this proof-of-concept study, we investigated the extraction recovery from disposable diapers, cotton pads, and gauzes of the free versus glucuronidated urinary species of three example chemicals: bisphenol A, triclosan, and 4-methylumbelliferone. Although the glucuronides were almost fully recovered, the free species were not. Our results suggest that, in addition to other sampling considerations, the binding affinity and extraction recovery of the target biomarkers to the material used to collect the urine should be considered. Alternative collection approaches that do not require such an extraction (e.g., urine bags routinely used in hospitals) may be worth exploring. Despite its shortcomings, having urinary concentrations for biomonitoring considerably strengthens the exposure assessment, particularly for infants and young toddlers, and the benefits of including biomonitoring data outweigh their potential limitations.Journal of Exposure Science and Environmental Epidemiology advance online publication, 24 March 2010; doi:10.1038/jes.2010.16. |
Urinary concentrations of four parabens in the U.S. population: 2005-2006
Calafat AM , Ye X , Wong LY , Bishop AM , Needham LL . Environ Health Perspect 2010 118 (5) 679-85 BACKGROUND: Parabens are widely used as antimicrobial preservatives in cosmetics, pharmaceuticals, and in food and beverage processing. OBJECTIVES: To assess exposure to methyl, ethyl, propyl, and butyl parabens in a representative sample of persons aged 6 years and older in the U.S. general population from the 2005-2006 National Health and Nutrition Examination Survey. METHODS: We analyzed 2,548 urine samples by using online solid-phase extraction coupled to isotope dilution-high-performance liquid chromatography-tandem mass spectrometry. RESULTS: We detected methyl paraben (MP) and propyl paraben (PP) in 99.1% and 92.7% of the samples, respectively. We detected ethyl (42.4%) and butyl (47%) parabens less frequently and at median concentrations at least one order of magnitude lower than MP (63.5 microg/L) and PP (8.7 microg/L). Least square geometric mean (LSGM) concentrations of MP were significantly higher (P≤ 0.01) among non-Hispanic blacks than among non-Hispanic whites except at older ages (≥60 years). Female adolescents and adults had significantly higher (P<0.01) LSGM concentrations of MP and PP than adolescent and adult males. Females were more likely (adjusted odds ratio [OR] [95% confidence interval, 95% CI]) than males (MP: 3.2 [2.99-5.27], PP: 4.19 [2.34-7.49]) and non-Hispanic blacks were more likely than non-Hispanic whites (MP: 4.99 [2.62-9.50], PP: 3.6 [1.86-7.05]) to have concentrations above the 95th percentile. CONCLUSIONS: The general U.S. population was exposed to several parabens during 2005-2006. Differences in the urinary concentrations of methyl and propyl parabens by sex and race/ethnicity likely reflect the use of personal care products containing these compounds. |
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