Biomedical subjects

L L Needham

Publications and source records attributed to L L Needham.

135 records · Page 8Linked to original sources

PubMedDate not supplied

Selected analytical methods used at the Centers for Disease Control and Prevention for measuring environmental pollutants in serum.

Blood serum is one of the more viable matrices used in assessing exposure to persistent environmental contaminants or their metabolites, especially those that are lipophilic. Analytic methods currently in use for this matrix usually involve liquid/liquid extraction followed by adsorption chromatography as a cleanup step, and low- or high-resolution gas chromatography with either electron-capture or mass spectrometric detection. The traditional analytic methods are labor intensive, have low sample throughput, and use excessive amounts of solvents and reagents. Two analytic approaches that address the requirements of modern laboratories more effectively are: 1) solid-phase extraction (SPE), used to analyze serum for several classes of compounds of environmental concern (e.g., polychlorinated biphenyls [PCBs], persistent pesticides, dioxins, furans, and coplanar polychlorinated biphenyls [CPCBs]), and 2) fast chromatography with a two-dimensional gas chromatographic system, which can be used in the determinative step for these types of analytes.

Benzofurans↗

PubMedDate not supplied

Reference range data for assessing exposure to selected environmental toxicants.

We analyzed blood and urine specimens from 32 charter boat captains, anglers, and spouses from both groups, who reportedly ate fish from Lakes Michigan, Huron, or Erie, for selected environmental toxicants. The toxicants measured in serum were polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), coplanar polychlorinated biphenyls, other polychlorinated biphenyls (PCBs), and persistent pesticides. Nonpersistent pesticides and elements were measured in urine; and elements were measured in blood. Internal dose levels of these toxicants will be compared to reference range data that we have compiled. These reference range data will be used to ascertain the exposure status of individuals or groups within this study.

Adolescent↗

PubMedDate not supplied

Serum levels of several organochlorine pesticides in farmers correspond with dietary exposure and local use history.

In response to reported increased cancer risks among farmers, the Agricultural Health Study (AHS) was designed to examine health outcomes and environmental exposures among farm families in the United States. In the pilot phase of the AHS, food, beverage, air, dermal, dust, surface wipe, and biological specimens (blood and urine) were collected and analyzed for six farm families in two states (IA and NC). In addition, questionnaires were administered to examine previous pesticide use. This paper reports the organochlorine pesticide results of the serum and dietary analyses as well as questionnaire results from the pilot exposure study of farmers and their families. Note, no organochlorine pesticides were reported as currently being applied to the study farms. In all human serum samples examined, typical U.S. population levels were found for the majority of the pesticides. In addition, human serum levels of organochlorine pesticides showed no significant daily or seasonal variation. However, serum trans-nonachlor levels were found to be higher in people living on the two farms in North Carolina than in people living on the four farms in Iowa (p < 0.05). Further, unusually high dieldrin levels were found in serum samples from a farmer and spouse living on an Iowa farm, and these levels were significantly higher than those of people living on the other farms (p < 0.05). Dieldrin was persistent in the foods consumed on the same Iowa farm where family members showed elevated serum levels. In addition, dietary samples from the North Carolina farms exhibited high levels of chlordane. No organochlorine pesticides were found in any of the drinking water samples. Dietary dieldrin levels on the same Iowa farm exceeded the oral reference dose (RfD) eight- to eleven-fold (50 ng/kg-day). No other pesticide exceeded the RfD. However, dietary chlordane levels at a North Carolina farm reached 17% of the RfD. Previous use of aldrin on an Iowa farm corresponded to dieldrin found in the diet and in the serum of the farmer and spouse. Previous reported use of chlordane on the North Carolina farms corresponded with measurable dietary levels of chlordance and higher serum trans-nonachlor levels than the levels in Iowa farm families.

Adult↗

PubMedDate not supplied

Strategies for biological monitoring of exposure for contemporary-use pesticides.

Pesticides are used on a massive scale in the United States. The widespread use of these pesticides has made it virtually impossible for the average person to avoid exposure at some level. Generally, it is believed that low-level exposure to these pesticides does not produce acute toxic effects; however, various cancers and other noncancer health endpoints have been associated with chronic exposure to several groups of pesticides. Therefore, it is imperative that well-designed studies investigate the potential relationship between contemporary pesticide exposure and health effects. For these studies to be accurate, reliable methods for determining individual exposure must be used. Biological monitoring is a useful tool for assessing exposure to some contemporary pesticides. As with any analytical method, biological monitoring entails many difficulties, but, in many instances, they can be overcome by the logical use of available information and information acquired in carefully designed studies. At the Centers for Disease Control and Prevention (CDC), we have acquired extensive experience in the development and application of specific techniques for biological monitoring of a variety of toxicants, including many of the contemporary-use pesticides. We have used these methods to measure the internal dose of pesticides received by people in acute and chronic incidents resulting from both environmental and industrial exposure. Additionally, we have established normative values, or reference ranges, of several pesticides based on measurements of their metabolites in the urine of randomly selected adults in the US population. These data have been successfully used to distinguish overt exposures from 'background' exposure. In this paper, we present several examples of the usefulness of biological monitoring in urine and blood and describe the difficulties involved with developing methods in these matrices. We also present a general strategy, considerations, and recommendations for developing biological monitoring techniques for measuring the internal dose of contemporary-use pesticides.

Adult↗

PubMedDate not supplied

Analysis of a mixture of polychlorinated biphenyls and chlorinated pesticides in human serum by column fractionation and dual-column capillary gas chromatography with electron capture detection.

An analytical method is presented for precise identification and quantitation of 29 specific polychlorinated biphenyl (PCB) congeners and 15 chlorinated pesticides in human serum. Analyte surrogates PCB 30, PCB 204, 2,2',4,4',5,5'-hexabromo-biphenyl, perthane, alpha-hexachlorocyclohexane, and dichlorobenzophenone were added to each sample. The serum was extracted with an organic solvent and separated by adsorption chromatography into 3 elution fractions for high-resolution gas chromatographic analysis. Each fraction was analyzed by dual-column capillary chromatography followed by electron capture detection. Two capillary columns, DB-5 and DB-1701, with different polarities were used to increase selectivity for each analyte. Quantitation was performed by selecting 2 sets of calibration standard mixtures and 1,2-dichloronaphthalene as an internal standard. Mean recoveries ranged from 39 to 126% for selected analytes and from 31 to 88% for surrogates. Detection limits for specific congeners and pesticides are reported. Typical chromatographic profiles of calibration standard mixtures, as well as a human sample, are illustrated. Verification of each analyte is assessed, and results of analyses of selected human samples and quality control criteria used to ensure data validity also are presented.

Calibration↗

PubMedDate not supplied

Determination of Mirex in human blood serum containing polychlorinated biphenyls by using packed column gas chromatography.

An analytical method has been developed that uses electron capture/gas-liquid chromatography to determine Mirex in serum containing polychlorinated biphenyls (PCBs) (Aroclor 1260). With this method, 0.2 ppb Mirex can be determined in 4 mL serum that also contains 10 ppb PCBs. The method provides approximately 70% recovery of Mirex at 1.0 and 3.5 ppb. The coefficients of variation are 4.5 and 4.6% at 1.0 and 3.5 ppb, respectively. In a cooperative study with the Ohio Department of Health, the Centers for Disease Control used this method to determine the extent of exposure of Salem, OH, residents to Mirex. Confirmation of Mirex was obtained by using high resolution gas chromatography and high resolution mass spectrometry.

Chromatography, Gas↗

PubMedDate not supplied

Gas chromatographic determination of polychlorinated biphenyls (as Aroclor 1254) in serum: collaborative study.

A gas chromatographic-electron capture detection method for determining the concentration of polychlorinated biphenyls (PCBs) as Aroclor 1254 (AR 1254) in serum was evaluated through a 2-phase collaborative study. In Phase I, each collaborator's lot of Woelm silica gel (70-150 mesh) was evaluated for elution and recovery of AR 1254, which had been added in vitro at 25 ng/mL to a serum extract. In Phase II, each collaborator analyzed a series of bovine serum samples that contained the following: (1) in vitro-spiked AR 1254; (2) in vivo AR 1254 and 8 in vitro-spiked chlorinated hydrocarbons; (3) in vivo AR 1254 only; (4) 8 in vitro-spiked chlorinated hydrocarbons only; and (5) neither AR 1254 nor chlorinated hydrocarbons above the detection limit of the method. In Phase I, the average recovery of AR 1254 from silica gel for the 6 collaborators was 87.9 +/- 15.44% (mean +/- 1 SD; N = 18; range = 52.3-105.8%). In Phase II, the analysis of in vitro spikes of AR 1254 in serum at 8.58, 16.8, 41.8, and 84.3 ppb gave mean (means) interlaboratory recoveries of 89.0, 83.3, 79.4, and 76.9%, respectively, with within-laboratory (repeatability) relative standard deviations (RSDr) of 18.8, 20.5, 10.2, and 14.1%, respectively, and among-laboratory (reproducibility) relative standard deviations (RSDR) of 21.5, 21.1, 14.6, and 20.8%, respectively. The determination of in vivo AR 1254 in samples containing approximately 10, 25, 50, and 100 ng/mL of AR 1254 resulted in interlaboratory means of 10, 22, 39, and 79 ng/mL, respectively, with RSDr = 6.7, 9.7, 6.4, and 5.8%, respectively, and RSDR = 20.6, 16.0, 10.9, and 10.3%, respectively. The precision of the method for incurred AR 1254 showed a maximum RSDr of less than 10% and a maximum RSDR of less than 21% for a concentration range of 10-100 ng/mL. The accuracy of the method as demonstrated by the mean recovery of in vitro-spiked AR 1254 over a concentration range of 8.58-843 ng/mL was 82.2%. The method has been approved interim official first action.

Animals↗

PubMedDate not supplied

Improving exposure assessment by monitoring human tissues for toxic chemicals.

Typically, the availability of appropriate data to estimate human exposures to toxic chemicals is scarce. Consequently, exposure assessments are often based on indirect surrogates of exposure, such as a combination of questionnaire data on time-activities and concentrations of toxic chemicals measured in environmental media (e.g., air, water, food, soil, dust). Recent advances, however, make it technically feasible and relatively affordable to measure low levels of multiple toxic chemicals in accessible human tissues (e.g., blood, urine). The increasing availability of biological markers for exposure, along with improvements in pharmacokinetic understanding, present new opportunities to estimate exposure from human tissue measurements and from knowledge of intake and uptake parameters. Biological monitoring provides exposure information that is usually complementary to the type of exposure information obtained from environmental monitoring. Biological and environmental monitoring can be used separately or together in order to meet desired objectives. We present here a discussion of the value of biological monitoring for improving exposure assessment. We emphasize the role of biological monitoring in identifying high-priority exposures, evaluating the effectiveness of intervention and prevention efforts, identifying at-risk subpopulations, recognizing time trends in population exposures, establishing reference ranges of tissue concentrations, and providing integrated dose measurements.

Environmental Monitoring↗

PubMedDate not supplied

Serum dioxin levels in Seveso, Italy, population in 1976.

On July 10, 1976, an explosion at a chemical plant near Seveso, Italy, released a mixture of chemicals, including 2,3,7,8-tetrachlorodibenzo-p-dioxin and 2,4,5-trichlorophenol. As a result, several thousand people in the Seveso area may have been exposed to those chemicals. At that time, human exposure assessment was based primarily on soil levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin. Medical examinations of this potentially exposed population and control subjects were begun in 1976 and in some cases continued until 1985. In 1988, we began assessing human exposure in this population by measuring 2,3,7,8-tetrachlorodibenzo-p-dioxin in small volumes of serum specimens remaining from the medical examinations. As expected, we found that the median serum dioxin levels were highest among people who lived closest to the explosion and were progressively lower among groups living farther away. These measurements have allowed us to assess exposure more accurately among individuals in this population and to relate exposure to various health effects. We found that some individuals in the exposed population had among the highest serum dioxin levels ever reported, yet chloracne was the only unequivocal effect found; cancer risks are still being investigated. We also found that other individuals with as high or higher serum dioxin levels did not develop chloracne. We also found that the serum half-life of dioxin in this population was 7-8 years, which agrees with other findings although we do report some differences in the serum half-life of TCDD for women and children. We also observed an increase in the percentage of female newborns to parents who resided in Zone A at the time of the explosion, and we also report on the 1976 serum dioxin levels in people who later developed cancer.

Accidents↗