Daniel C. Paschal

Determination of lead in blood using electrothermal atomisation atomic absorption spectrometry with a L'vov platform and matrix modifier

Accuracy in the determination of blood lead is of primary importance in such diverse activities as screening for childhood lead poisoning, occupational exposure monitoring and population surveys. To meet the stringent requirements of the third National Health and Nutrition Examination Survey (NHANES III), a large normative population study to be held from 1988–1994, we needed a method for the determination of lead in blood that was simple, accurate, rugged and of defined accuracy for both calibration and control materials. The recent availability of the National Bureau of Standards Standard Reference Materials 2121–2 and 955, a lead standard solution (10 000 mg l–1) and a certified lead in blood reference material has made it possible to evaluate a method against definitive values and NBS reference materials.In the proposed method, sample preparation consists of a simple dilution (1 + 9) with a matrix modifier which contains 0.5%V/V Triton X-100, 0.2%V/V 16 M nitric acid and 0.2%m/V dibasic ammonium phosphate. This matrix modifier stabilises lead so that the majority of the blood matrix may be removed during the char step. Maximum accuracy in dilution is achieved with the use of autopipettes which have been shown to deliver viscous materials such as blood and serum with high accuracy. The method described in this study has a detection limit of about 0.07 µmol l–1(3 SD) and a precision and accuracy of ±2–5% at the 0.24–2.4 µmol l–1 concentration level. Linearity has been demonstrated up to about 4 µmol l–1. Comparability has been established with the previous blood lead analytical method used in other surveys via the analysis of 435 specimens by both the previous (modified Delves cup) and proposed methods. The equation of the resulting line is [ETA-AAS]= 1.0007[Delves]– 0.051, r= 0.924.

Profiles of Great Lakes critical pollutants: a sentinel analysis of human blood and urine.

To determine the contaminants that should be studied further in the subsequent population-based study, a profile of Great Lakes (GL) sport fish contaminant residues were studied in human blood and urine specimens from 32 sport fish consumers from three Great Lakes: Lake Michigan (n =10), Lake Huron (n = 11), and Lake Erie (n = 11). Serum was analyzed for 8 polychlorinated dioxin congeners, 10 polychlorinated furan congeners, 4 coplanar and 32 other polychlorinated biphenyl (PCB) congeners, and 11 persistent chlorinated pesticides. Whole blood was analyzed for mercury and lead. Urine samples were analyzed for 10 nonpersistent pesticides (or their metabolites) and 5 metals. One individual was excluded from statistical analysis because of an unusual exposure to selected analytes.

Serum selenium levels in the US population: Third National Health and Nutrition Examination Survey, 1988-1994.

The published literature on serum selenium levels in the US population describes studies on small samples that may not be representative of the US population. This analysis provides the first nationally representative serum selenium levels in the US population by age group, sex, race-ethnicity, poverty income ratio (PIR), geographic region, and urban status. The Third National Health and Nutrition Examination Survey (NHANES III) is a national population-based cross-sectional survey with an in-person interview and serum selenium measurements.For the 18,597 persons for whom serum selenium values were available in NHANES III, the mean concentration was 1.58 µmol/L and the median concentration was 1.56 µmol/L. Mean serum selenium levels differed by age group, sex, race-ethnicity, PIR, and geographic region. The US population has slight differences in serum selenium levels by demographic factors.

Environmental and biomarker measurements in nine homes in the Lower Rio Grande Valley: Multimedia results for Pesticides, metals, PAHs, and VOCs

Residential environmental and biomarker measurements were made of multiple pollutants during two seasons (spring and summer, 1993) in order to assess human exposure for a purposeful sample of 18 nonsmoking adults residing within nine homes (a primary and secondary subject in each home) in the Lower Rio Grande Valley (LRGV) near Brownsville, TX. Pesticides, metals, PAHs, VOCs, and PCBs were measured in drinking water, food, air, soil, and house dust over a one- to two-day period in each season. Biomarker measurements were made in blood, breath, and urine. A total of 375 measurements across five pollutant classes (227 pesticides, 44 trace elements, 78 VOCs, 18 PAHs, and 8 PCBs) was possible for each home in one or more media. A large percentage of the measurements was below the method limit of detection ranging from 0–37% for pesticides, 22–61% for metals, 6% and 90% for VOCs in water and air, respectively, and 0–74% for PAHs. The total number of analytes measurable in blood, urine, or breath was considerably less, i.e., 58 (21 pesticides, 1 PCB, 4 metals, 31 VOCs, and 1 PAH) with the percentage above the method limit of detection for pesticides and metals ranging from 40 to 100%, while for VOCs, PAHs, and PCBs, this percentage ranged from 2 to 33%. A significant seasonal difference (p≤0.10) was found in the biomarker levels of two of seven nonpersistent pesticides (3,5,6-trichloro-2-pyridinol and 2,5-dichlorophenol) and 3 of 3 metals (arsenic, cadmium, and mercury) and the pyrene metabolite, 1-hydroxypyrene, measured in urine. In all cases, levels were higher in the summer relative to the spring. For the persistent pesticides and PCBs in blood serum, a seasonal effect could be evaluated for 5 of 10 analytes; a significant difference (p≤0.10) was observed only for hexachlorobenzene, which like the urine biomarkers, was higher in the summer. In contrast to the urine metals, blood-Pb concentrations did not change significantly (p≤0.05) from spring to summer. Biological results from the current study are compared to the reference range furnished by the Third National Health and Nutrition Examination Survey (NHANES III). Comparisons are only suggestive due to limitations in comparability between the two studies. Based on the percentage of measurements above the detection limit, a significant elevation (p≤0.10) in 2 of 12 nonpersistent pesticides (4-nitrophenol and 2,4-D) was observed for the LRGV study subjects. The VOC carbon tetrachloride was found in the blood (monitored only in spring) with greater prevalence (p≤0.10) than would be expected from NHANES III results. Blood serum levels of two persistent pesticides (4,4′-DDE, and trans-nonachlor) and PCB exceeded median and/or 95th percentile reference levels as did arsenic in urine. Where seasonal differences were identified or for compounds exceeding reference levels, environmental monitoring results were investigated to identify potential contributing pathways and sources of exposure. However, because environmental sampling did not always coincide with the biological sampling and because of the high frequency of analytes measured below the limit of detection, sources and pathways of exposure in many cases could not be explained. Chlorpyrifos was an exception where urine metabolite (3,5,6-TCP) levels were found to be significantly correlated with air (R2=0.55; p≤0.01) and dust (R2=0.46; p≤0.01) concentrations. Based on the results of biomarker and residential environmental measurements over two seasons, this scoping study shows a seasonal effect for some analytes and suggests where exposures may be high for others. This information may be useful in considering future studies in the region.

Chronic renal effects in three studies of men and women occupationally exposed to cadmium

We measured sensitive indicators of renal damage in three different populations occupationally exposed to cadmium, and examined the degree of variation in damage and the relative sensitivity of different types of indicators. The three studies included (1) men exposed in a cadmium recovery plant, (2) men exposed in a nickel/cadmium battery plant, and (3) women exposed in the latter plant. The indicators of renal damage were urinary proteins in three categories: (1) the high molecular weight enzymes alanine aminopeptidase (AAP) and N-acetyl-β-D-glucosaminidase (NAG), (2) the intermediate molecular weight protein albumin (ALB), and (3) the low molecular weight proteins retinol-binding protein (RBP) and β2-microglobulin (B2M). These tests indicate that exposed groups with higher urine cadmium levels had varying degrees of renal damage. All exposed groups showed evidence of renal damage when compared with their respective control groups. A higher percentage of elevated protein levels was noted in the exposed group of Study 1 than in the exposed groups of Studies 2 and 3. In Study 1, the means of all five protein levels and ALB, RBP, and B2M fractional clearances were significantly elevated in the group with higher urine cadmium concentrations when compared with the groups with lower urine cadmium concentrations. Highly significant dose-response relationships for all of the urinary protein tests, including fractional clearances, were found. All of the tests were more sensitive in detecting evidence of subclinical renal damage than serum creatinine, a commonly used indicator of renal function. The order of test sensitivity in men was determined by considering three factors: (1) the magnitude of the correlation coefficient between the test and the urine cadmium concentration in the study with the most advanced damage, (2) the relative cadmium level predicted by the dose-response model at which there is a 10% chance of observing an elevated test value, and (3) the ability of the tests to detect renal effects in the population with less advanced damage. The tests in order of decreasing sensitivity in men are ALB, AAP, NAG, RBP≈B2M. The women with higher urine cadmium levels in Study 3 had a higher percentage of elevated AAP and NAG values when compared with the control group.

Determination of thorium and uranium in urine with inductively coupled argon plasma mass spectrometry

An accurate and simple method has been developed for the determination of thorium and uranium in urine using inductively coupled argon plasma mass spectrometry (ICP-MS). Determination of thorium and uranium was by external calibration using matrix matched standards and high-purity spiking materials. Aliquots of each urine specimen were diluted (1 + 9) with 0.2 mol l–1 nitric acid containing iridium as an internal standard. The counts at m/z 232 (thorium), 238 (uranium) and 193 (iridium) were measured, and ratios of the counts at m/z 232 or 238 to those at m/z 193 were calculated. These ratios were compared with those from urine-based calibration standards to calculate the thorium and uranium concentrations in unknown specimens. The concentrations of thorium and uranium were calculated as µg l–1 in the sample and also corrected for dilution via creatinine measurement, expressed as µg g–1 of creatinine. The method has been evaluated by determination of reference materials from the Los Alamos National Laboratory, as well as of those from the Oak Ridge National Laboratory. The proposed method provides the basis of an accurate method for determining thorium and uranium in unexposed subjects as well as in those considered to be exposed to thorium or uranium through environmental or other pathways. About 40 specimens, excluding blanks, calibration standards and quality-control materials, can be processed in an 8 h day.

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.

Determining lead sources in Mexico using the lead isotope ratio

OBJECTIVE Lead poisoning can, in some cases, be traced to a specific route or source of exposure on the basis of the individuals blood lead isotope ratio. To assess the major source of lead exposure among women residing in Mexico City, we compared blood, ceramic, and gasoline lead isotope ratios. MATERIAL AND METHODS The study population, randomly selected from participants of a large trial, (1/1996-12/1996) comprised of 16 women whose lead levels exceeded 10 micrograms/dl and who reported using lead-glazed ceramics. Lead isotope ratios were performed on a Perkin Elmer 5000 Inductively Coupled Plasma Mass Spectrometer (ICP-MS) interfaced with a Perkin Elmer HGA-600MS Electrothermal Vaporization System (ETV). RESULTS The isotope ratios (206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb) of both the blood specimens and their corresponding ceramic specimens were highly correlated, with r = 0.9979, r2 = 0.9958, r = 0.9957, r2 = 0.9915 and r = 0.9945, r2 = 0.9890 values for the three isotope ratios, respectively, suggesting that the lead exposure most likely resulted from the use of these ceramic. Measurements of lead isotope ratios from leaded gasoline in use at the time of blood sampling, differed from those in blood and ceramics. CONCLUSIONS Determining lead isotope ratios can be an efficient tool to identify a major source of lead exposure and to support the implementation of public health prevention and control measures. This paper is available too at: http://www.insp.mx/salud/index.html.

Organic Mercury Levels among the Yanomama of the Brazilian Amazon Basin

Abstract The Catrimani River basin in northern Brazil is the home of the Yanomama and has been the site of renegade gold mining since 1980. Gold-mining operations release inorganic mercury (Hg) into the environment where it is organified and biomagnified in aquatic ecosystems. Ingestion of mercury-contaminated fish poses a potential hazard to fish-eating populations such as the Yanomama. We surveyed Hg levels in Yanomama villagers living near mined and unmined rivers in 1994 and 1995, and analyzed Hg levels in piranha caught by villagers. In 1994, 90 Yanomama Indians from 5 villages and in 1995, 62 Yanomama Indians from 3 villages participated in the studies. Four villages surveyed in 1994 were located directly on the Catrimani River, approximately 140–160 km downstream from past gold-mining activities. The other village surveyed in 1994 was situated on the unmined Ajaraní River. In 1995, 2 of the Catrimani River villages were revisited, and a third Yanomama village, on the unmined Pacu River, was surveyed. Blood organic mercury levels among all villagers surveyed ranged from 0 to 62.6 µg L–1 (mean levels in each village between 21.2 µg L–1 and 43.1 µg L–1). Mercury levels in piranha from the mined Catrimani River ranged from 235 to 1084 parts per billion (ppb). Nine of 13 piranhas, measuring 30 cm or longer had total mercury levels which exceeded mercury consumption limits (500 ppb) set by both the World Health Organization and the Brazilian Ministry of Health. Unexpectedly, high mercury levels were also observed in fish and villagers along the unmined Ajaraní and Pacu Rivers suggesting that indirect sources may contribute to environmental mercury contamination in the Amazon basin.

Determination of lead in whole blood using inductively coupled argon plasma mass spectrometry with isotope dilution

An accurate and simple method for determination of lead in whole blood using inductively coupled argon plasma mass source mass spectrometry (ICP-MS) was developed. Determination of lead was by stable isotope dilution, using a spiking material from the National Institute of Standards and Technology (NIST), Standard Reference Material (SRM) 983, Radiogenic Lead Isotopic Standard, enriched to 92.15 at.% lead 206 (206Pb). Two aliquots of each whole blood specimen were taken (about 0.50 g) and weighed accurately by difference. One of the aliquots was then spiked with about 100 mg of a solution prepared from SRM 983; about 1 µg g–1 of Pb in concentration. Both aliquots were then digested with ultrapure, concentrated nitric acid in a microwave oven. The digestate was cooled, diluted, and both unspiked and spiked digests were aspirated into the ICP-MS instrument and isotope ratios of lead 208 : lead 206 were measured. The amount and concentration of lead was calculated as µg of lead per g sample, and multiplied by 100 to give µg of lead per 100 g of sample. This mass-basis measurement (µg per 100 g) was then converted to mass per volume (µg dl–1) using the measured density of the whole blood specimen as a correction factor. The method has been evaluated using SRM 955a to determine accuracy. The proposed method provides a standard of accuracy for determination of lead in blood in a nationally based standardization programme, the Blood Lead Laboratory Reference System (BLLRS).