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Biomedical subjects

D L Ashley

Publications and source records attributed to D L Ashley.

At least 19 recordsLinked to original sources
PubMed1995

Using biological monitoring to assess human exposure to priority toxicants.

Scientifically valid exposure assessment is crucial to risk assessment, risk management, and prevention of environmental disease. Scientists have used three tools to assess exposure: exposure history/questionnaire, environmental monitoring (including personal monitoring), and biological monitoring. Combinations of these tools usually provide the exposure information needed to meet objectives of human studies evaluating the exposure-health effect relationship. Biological monitoring is a capable exposure assessment tool that has provided important information used in public health decisions. We briefly describe how risk assessment and risk management decisions for lead, dioxin, and volatile organic compounds have substantially benefited from exposure information obtained from biological monitoring.

Dioxins↗
PubMed1995

The priority toxicant reference range study: interim report.

The relationship between human exposure to environmental toxicants and health effects is of utmost interest to public health scientists. To define this relationship, these scientists need accurate and precise methods for assessing human exposure and effects. One of the most accurate and precise means of assessing exposure is to measure the level of the toxicant or its primary metabolite in a biologic specimen; this has been defined as measuring the internal dose. This measurement must be quantitative to best study the dose-response relationship. Pertinent questions asked during an exposure assessment include "How do the levels of a given toxicant in a particular population compare with the levels of that toxicant in other populations?" and "What is the prevalence of exposure to that toxicant in other populations?" To answer these questions for two chemical classes of environmental toxicants, we developed state-of-the-art analytic methods and then applied them to measure the levels of 44 environmental toxicants in biologic specimens from 1000 United States residents who participated in the Third National Health and Nutrition Examination Survey (NHANES III). These 1000 people are a cross-sectional subset of the NHANES III population and were selected from urban and rural communities in four regions of the United States; all were between 20 and 59 years of age. This subset is not a probability-based sample.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Volatile organic compounds in the blood of persons in Kuwait during the oil fires.

Between March and November of 1991, approximately 9000 workers from 43 different countries battled the burning oil wells in Kuwait. To document the exposure of persons in Kuwait during the oil well fires to volatile organic compounds (VOCs), we obtained samples of blood from 14 U.S. personnel in Kuwait City in May of 1991 (group I) and 40 American firefighters working in the oil fields in October of 1991 (group II). Concentrations of VOCs in group I and group II were compared with those of a random sample of 114 persons in the United States (reference group). The median concentrations of VOCs in group I were equal to or lower than those in the reference group. We found significant differences between the median concentrations of several VOCs in group II and the reference group. Median levels of ethylbenzene were about 10 times higher among group II than among the reference group (0.53 microgram/l vs 0.052 microgram/l). Median levels of benzene, m-/p-xylene, o-xylene, styrene, and toluene among group II were more than double those of the reference group. Although firefighters had higher median concentrations of VOCs than the reference group, those American personnel in Kuwait not involved in fighting the oil fires had concentrations of VOCs comparable to those in the reference group. Blood VOC measurements indicate a significant increase in exposure to VOCs in firefighters, but do not demonstrate this in personnel in Kuwait City.

Adult↗
PubMed1994

Production of blank water for the analysis of volatile organic compounds in human blood at the low parts-per-trillion level.

Blank water with low levels of volatile organic compounds (VOCs) is of critical importance in many analytical procedures. Because of the increased use of more sophisticated instrumentation, the detection limits for these compounds have dropped dramatically. Consequently, techniques in use in the analytical laboratory to generate blank water may now prove inadequate. The need for blank water with low levels of VOCs was recently underscored by the development of an analytical procedure to analyze 32 VOCs in whole blood; this procedure has detection limits in the tens of parts-per-trillion level for most VOCs. Common sources of blank water in the laboratory such as deionized, cartridge-filtered, and HPLC-grade bottled water are analyzed. These sources contained high concentrations of some VOCs that would interfere with low parts-per-trillion analyses. Well water and bottled water used for human consumption are analyzed, but both prove inadequate for the analysis of VOCs at parts-per-trillion levels. A combination of distillation and purging with helium produced blank water with VOC levels of less than 10 parts-per-trillion for most of the 16 VOCs studied.

Blood Chemical Analysis↗
PubMed1994

Technical and scientific developments in exposure marker methodology.

Recent advances in techniques to measure markers of exposure to environmental toxicants in humans are changing the ways in which environmental scientists, epidemiologists, and policymakers characterize and interpret such exposure. In this article we review some major technical and scientific developments in exposure marker methodology for estimating internal dose, with special reference to studies conducted at the US Centers for Disease Control and Prevention. We consider important characteristics of laboratory methods, advances in laboratory technology, analytical standards, and quality assurance of laboratory measurements; comparisons with indirect methods for estimating exposures, such as exposure indices and questionnaires; human pharmacokinetic data; sampling problems; surveillance of human exposures to toxicants; and interpretation of measurements. With a view to increasing the reliability of exposure assessment, we make recommendations for obtaining more data on human exposure to toxicants.

Biomarkers↗
PubMed1994

Blood concentrations of volatile organic compounds in a nonoccupationally exposed US population and in groups with suspected exposure.

Exposure to certain volatile organic compounds (VOCs) commonly occurs in industrialized countries. We developed a method for measuring 32 VOCs in 10 mL of whole blood at low concentration. We used this method to determine the internal dose of these compounds in 600 or more people in the US who participated in the Third National Health and Nutrition Examination Survey. From our study results, we established a reference range for these VOCs in the general population of the US. We found detectable concentrations of 1,1,1-trichloroethane, 1,4-dichlorobenzene, 2-butanone, acetone, benzene, chloroform, ethylbenzene, m,p-xylene, styrene, tetrachloroethane, and toluene in most of the blood samples of nonoccupationally exposed persons. The accuracy of VOC evaluations depends on the ability of investigators to make sensitive and reproducible measurements of low concentrations of VOCs and to eliminate all sources of interference and contamination.

Environmental Exposure↗
PubMed1992

Performance characteristics of a composite multivariate quality control system.

We present the results of an evaluation of the performance characteristics of a composite multivariate quality control (CMQC) system that incorporates quality control rules for univariate, multivariate, and correlation conditions. The CMQC system evaluated is designed to help analysts detect unacceptable trends and systematic error in one or more variables, unacceptable random error in one or more variables, and unacceptable changes in the correlation structure of any pair of variables. It is also designed to be tolerant of missing data, to allow analysts to reject as few as one or as many as all variables in a run, and to provide analysts with control statistics and graphics that logically relate to sources of analytical error. We show that the various components of the CMQC system have adequate statistical power to detect systematic errors, random errors, and correlation changes under the conditions likely to be encountered with multivariate analytical measurement systems: (1) a single variable with increased systematic or random error; (2) all variables or a subgroup of variables affected by a common problem that increases systematic or random error; and (3) missing data for one or more variables in a run. We also show that the power of the multivariate component of the CMQC system to detect systematic and random errors is higher than the power of an alternative multivariate test criterion.

Chemistry Techniques, Analytical↗
PubMed1992

Determining volatile organic compounds in human blood from a large sample population by using purge and trap gas chromatography/mass spectrometry.

Volatile organic compounds (VOCs) are a major public health concern, because of their ubiquitous nature and the possible health effects associated with exposure to them. An analytical method has been developed that enabled the determination of parts per trillion levels of 32 VOCs in 10 mL of blood. Special efforts toward reducing blank levels and improving measurement sensitivity have resulted in an analytical method that shows excellent reproducibility and recovery even at these ultratrace levels. Results on normal human blood indicate that quantifiable levels of eleven VOCs can be found in virtually all whole blood samples. In a fraction of the samples, six other VOCs can also be determined at levels above detection limits. This method shows promise as a technique for estimating the normal baseline level of VOCs in human blood and may have future applications in cases of exposure.

Blood Chemical Analysis↗
PubMed1991

Composite multivariate quality control using a system of univariate, bivariate, and multivariate quality control rules.

We propose a composite multivariate quality control (CMQC) system to control simultaneously measured variables. This system is designed to detect unacceptable trends and systematic error in one or more variables, unacceptable random error in one or more variables, and unacceptable changes in the correlation structure in any pair of variables. It is also designed to be tolerant of missing data, to be capable of rejecting as few as one or as many as all variables in a run, and to provide the analyst with control statistics and graphics that logically relate to sources of analytical error. Quality control rules for univariate, multivariate, and correlation conditions are incorporated in the system, as are plots displaying CMQC statistic values and control limits for univariate, multivariate, and correlation parameters. We also discuss advantages of the CMQC over the T2 and principal component multivariate quality control methods. We demonstrate the CMQC procedure using data from a laboratory process in which 40 variables were measured during 40 characterization runs and 23 runs analyzing unknowns.

Chemistry Techniques, Analytical↗
PubMed1990

Gas chromatographic and spectral properties of pentafluorobenzyl derivatives of 2,4-dichlorophenoxyacetic acid and phenolic pesticides and metabolites.

Eleven phenols and 2,4-dichlorophenoxyacetic acid, compounds that may be found in body fluids of humans exposed to pesticides, are derivatized with pentafluorobenzyl bromide and characterized by gas chromatography with electron capture detection. These derivatives are further characterized by positive and negative chemical ionization mass spectrometry, nuclear magnetic resonance spectroscopy, and gas chromatography-Fourier transform infrared spectroscopy. Negative chemical ionization mass spectra of all derivatives have an anionic base peak derived from the parent analyte. In the positive mode the nonchlorinated derivatives have base peaks indicative of the analyte, while chlorinated derivatives are cleaved to give the pentafluorobenzyl cation as base peak. The possibility is explored that ortho-substituted phenols might be formed as byproducts in these derivatizations.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1989

Chromatographic and spectroscopic properties of hemiacetals of aflatoxin and sterigmatocystin metabolites.

Improved fluorescence detection of aflatoxin B1 by chromatographic analysis is accomplished by conversion to the corresponding hemiacetal, aflatoxin B2a. Because the metabolites aflatoxin M1, aflatoxin P1, aflatoxin Q1, sterigmatocystin, and O-methylsterigmatocystin have the same molecular conversion site, we investigated the chromatographic and spectroscopic properties of hemiacetals of these compounds to assist in confirming aflatoxins and sterigmatocystins in human urine. Nuclear magnetic resonance and infrared absorbance were used to confirm the hemiacetal structure for aflatoxin B1 and sterigmatocystin. The ultraviolet absorbance, fluorescence, and chromatographic properties of the metabolites were investigated. Using these data, we optimized the detection and solvent conditions for high-performance liquid chromatography. We determined that, of the conditions studied, maximum sensitivity and resolution for the native aflatoxins were achieved with a mobile phase of methanol, tetrahydrofuran, and water, a C8 column in series with a C18 column, and fluorescence detection with 365 nm excitation and 430 nm emission wavelengths for aflatoxins B1 and M1 and with 500 nm emission wavelength for aflatoxins P1 and Q1. For the analysis of the hemiacetals, a mobile phase of methanol, acetonitrile, and water provided better chromatography and fluorescence detection. Sterigmatocystin and O-methylsterigmatocystin were readily converted to the hemiacetal forms, which, like the aflatoxins, were more polar and, therefore, earlier eluting by reversed-phase HPLC (methanol, acetonitrile, and water, 236 nm absorbance). These data are important to maximize the sensitivity and confidence for detecting the mycotoxin metabolites in biological specimens.

Acetals↗
PubMed1989

Synthesis of N-(5-vinyl-1,3-thiazolidin-2-ylidene)phenylamine and analysis of oils implicated in the Spanish toxic oil syndrome for its presence.

Previous reports have implicated 1-phenyl-5-vinyl imidazolidine-2-thione (PVIZT), a cyclic reaction product of aniline and naturally occurring rapeseed oil isothiocyanates, as the potential causative agent of the Spanish toxic oil syndrome (TOS). This report describes the synthesis, preliminary characterization and analysis of that reaction product, which has been identified as N-(5-vinyl-1,3-thiazolidin-2-ylidene)phenylamine (5-VTPA) rather than PVIZT. Oil samples (n = 21) that contained fatty acid anilides and were epidemiologically linked to TOS were analysed for the presence of 5-VTPA by extraction of the oil with methanol and clean-up on an ion-exchange column, followed by capillary gas chromatography-mass spectrometry using selected ion detection. A limit of detection of less than 500 ppb was established for these analyses. No 5-VTPA could be detected, however, in any of the TOS oils. As 5-VTPA was shown to be unstable in both heated and unheated food oils, it is possible that the compound had been lost from the oils since the time of the epidemic in 1981. However, no direct evidence for the involvement of 5-VTPA in TOS could be obtained in this study.

Brassica↗
PubMed1989

Structural identification of a heterocyclic compound implicated in the Spanish toxic oil syndrome.

The compound 1-phenyl-5-vinylimidazolidine-2-thione was previously reported to be the causative agent in the outbreak referred to as Spanish toxic oil syndrome. X-ray crystallography, together with nuclear magnetic resonance and infra-red spectroscopy, now show the correct structure of this compound to be N-(5-vinyl-1,3-thiazolidin-2-ylidene)phenylamine (5-VTPA). Data for the structural characterization of 5-VTPA and the closely related isomer N-(4-vinyl-1,3-thiazolidin-2-ylidene)phenylamine are reported.

Brassica↗
PubMed1986

Assessment of a scheme for prioritizing inorganic toxicants by using signs-and-symptoms analysis.

In cases of exposure to unknown substances, analyzing environmental or biological samples for elevated levels of toxicants can be extremely complex. We assessed a method for prioritizing toxic substances according to the agreement between toxic-specific and incident-reported signs and symptoms by analyzing 25 reported case histories of exposure to inorganic toxicants. In all but one case, this analysis scheme successfully prioritized toxicants for subsequent analysis. Despite its limitations, the scheme is a substantial improvement over other available methods.

Diagnosis, Differential↗
PubMed1983

In vitro erythrocyte water transport in Duchenne muscular dystrophy: an NMR investigation.

Previous nuclear magnetic resonance (NMR) studies of erythrocyte water transport in Duchenne muscular dystrophy (DMD) have been extended to include mothers, as well as a larger patient group. The results, reported as values of the mean residence time, tau a, of intracellular water, reveals an experimentally significant decrease in permeability to water in most of the patients and one-half of the mothers examined. It was found that all mothers of patients with normal tau a values also show normal results. This finding suggests that Duchenne muscular dystrophy may exhibit genetic heterogeneity.

Biological Transport↗