Dayton T. Miller

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.

Arteriovenous Crossing Patterns in Branch Retinal Vein Occlusion

PURPOSE The study was designed to evaluate the relative anatomic position of the crossing vessels at the site of occlusion in eyes with branch retinal vein occlusion (BRVO). METHODS Fundus photographs of 106 eyes (104 patients) with recent BRVO from the Eye Disease Case-Control Study were used to examine the relative position of artery and vein at occluded crossings. Three separate comparison groups were formed by identifying corresponding arteriovenous crossings for each occluded crossing in: (1) the ipsilateral but opposite vessel arcade within eyes affected by BRVO; (2) the same quadrant in unaffected eyes of BRVO patients; and (3) the same quadrant in eyes of patients without BRVO, matched by age, sex, and race with the BRVO patients. RESULTS The site of obstruction of the branch vein was an arteriovenous crossing in all affected eyes. In 99% of eyes with BRVO, the artery was located anterior to the vein at the obstructed site. In the three comparison groups, the artery was anterior to the vein in 62%, 61%, and 54% of the crossings, respectively, yielding statistically significant differences for each group of control crossings compared with BRVO crossings (P < 0.001). CONCLUSION Finding the vein to be consistently between the more rigid artery and the retina at almost all arteriovenous crossings affected by BRVO suggests a possible role for mechanical obstruction in the pathogenesis of BRVO.

Blood lead concentration and children's anthropometric dimensions in the Third National Health and Nutrition Examination survey (NHANES III), 1988-1994

OBJECTIVE To assess the association between lead exposure and childrens physical growth. DESIGN Cross-sectional analysis of data from the Third National Health and Nutrition Examination Survey, 1988-1994. PARTICIPANTS A total of 4391 non-Hispanic white, non-Hispanic black, and Mexican-American children age 1 to 7 years. MEASUREMENTS AND RESULTS We investigated the association between blood lead concentration and stature, head circumference, weight, and body mass index with multiple regression analysis adjusting for sex, ethnic group, iron status, dietary intake, medical history, sociodemographic factors, and household characteristics. Blood lead concentration was significantly negatively associated with stature and head circumference. Regression models predicted reductions of 1. 57 cm in stature and 0.52 cm in head circumference for each 0.48 micromol/L (10 micrograms/dL) increase in blood lead concentration. We did not find significant associations between blood lead concentration and weight or body mass index. CONCLUSIONS The significant negative associations between blood lead concentration and stature and head circumference among children age 1 through 7 years, similar in magnitude to those reported for the Second National Health and Nutrition Examination Survey, 1976-1980, suggest that although mean blood lead concentrations of children have been declining in the United States for 2 decades, lead exposure may continue to affect the growth of some children.

Determination of uranium-235, uranium-238 and thorium-232 in urine by magnetic sector inductively coupled plasma mass spectrometry

Inductively coupled plasma mass spectrometry (ICP-MS) is a very useful method for the determination of long-lived isotopes of uranium, thorium and other elements. This study investigates parameters for measurement of isotopes of these elements in human urine using a magnetic sector ICP-MS method and a previously established quadrupole ICP-MS method. The investigation was performed by means of comparison of data from the determination of 238U, 235U and 232Th in urine-based quality control materials, as well as specimens from an investigation of occupational exposure to smoke and particulates from a population of firefighters. In addition to difference in instrumentation, additional isotopes were quantitated, and sample size was decreased to 100 µL for the magnetic sector method from 500 µL for the quadrupole method. Though non-instrumental bias in samples >500 ng L−1238U due to differences in the serial dilution technique (Digiflex diluter for quadrupole, Eppendorf pipettor for the magnetic sector method) was noted, results of comparison of the analyses of samples by magnetic sector ICP-MS compare very favorably with those from quadrupole ICP-MS (rsquared = 0.991 inclusive, 0.987 excluding serially diluted samples), with a near unity slope (0.934 inclusive, 1.06 excluding serially diluted samples) and near-zero intercept (0.0105 inclusive, 0.001 excluding serially diluted samples). Addition of calibration with 235U (0.72% in NIST U standard) allowed the characterization of QCs and measurement of this isotope using the magnetic sector method with a multi-run (n = 28) urine LOD of 0.06 ng L−1. Other magnetic sector urinary isotopic multi-run LODs were in the below 3 ng L−1 range for a 100 µL sample versus 4 ng L−1 for a 500 μL sample with the quadrupole (n = 43).

Chernobyl and iodine deficiency in the Russian Federation: an environmental disaster leading to a public health opportunity.

The Chernobyl nuclear disaster of April 26, 1986, triggered a chain of devastating events that later included an unexpected increase in childhood thyroid cancer and evidence of iodine deficiency (ID) in Russia. For the Russian people the Chernobyl event had profound psychological impacts, provoking anxiety about nuclear technology and mistrust of governmental control efforts. Frequently in public health a crisis is required to create the political will to manage longstanding problems, and public health officials must rapidly mobilize to take advantage of the opportunity. In this case, ID, previously not seen as a problem in Russia, was recognized to be potentially serious, and the Russian Federation, assisted by the catalytic binational effort of the U.S.-Russian Joint Commission on Economic and Technological Cooperation (Gore-Chernomyrdin Commission (GCC)) established a model salt iodization policy, developed a planning process, and implemented a program to prevent ID through a systematic approach that included the people, government, and private groups using open communication, dissemination of the findings, and action plans. By 1999, political will had been mobilized and over 20% of the nations salt was being iodized, up from about 1% in 1996. Universal iodization of salt was not a specific objective of the GCC; however, the increasing availability of iodized salt is leading to the elimination of ID, which is now a political goal in Russia. The full realization of this goal will require more time for education, marketing, and possibly legislative action.

Current activities at the Centers for Disease Control and Prevention's National Diabetes Laboratory.

In 1997, the Centers for Disease Control and Prevention established the National Diabetes Laboratory in order to help prevent and treat type 1 diabetes. This state-of-the-art laboratory collaborates with research scientists and key national and international organizations throughout the world to identify and study risk factors for type 1 diabetes by developing measurements for glycosylated proteins, developing and evaluating technology for measuring genetic risk factors for the disease, and working to standardize autoantibody measurements. Developing improved technologies for diagnosing and managing diabetes and developing reference materials for properly calibrating and standardizing blood glucose meters are also critical aspects of the laboratorys work. In addition, the laboratory provides quality storage for valuable collections of biologics and other materials and facilitates sharing of specimens, associated epidemiologic data, and test results. Working with our partners in diabetes research, we are improving the diagnosis, treatment, and prevention of type 1 diabetes.