Gastrointestinal absorption of uranium in humans.

The gastrointestinal absorption factor (f1) for uranium in humans has been determined from a study of 50 volunteers, ingesting uranium at natural levels in drinking water and food. The purpose of the study was to find an appropriate f1 value for humans to use in deriving exposure guidelines for uranium. The participants ranged in age from 13 to 87 years. They were selected from two communities: New Ross, Nova Scotia with elevated uranium in drinking water, and Ottawa, Ontario with very low levels of uranium. Uranium intake and excretion were measured in samples collected concurrently from the same individuals over a three-day period. The duplicate diet method was used to monitor uranium intake in food and water. Uranium levels in all samples were measured by inductively coupled plasma mass spectrometry (ICP/MS). The distribution of f1 values obtained was non-Gaussian with a range of 0.001 to 0.06 and a median of 0.009. Seventy-eight percent of the subjects had values less than 0.02. These values are consistent with the recommendations of ICRP 69. The f1 values were not gender-sensitive and were independent of age at time of study, duration of exposure, and total uranium intake. The implications of these findings are discussed in terms of setting drinking water guidelines.

Chronic ingestion of uranium in drinking water: a study of kidney bioeffects in humans.

A study was conducted of the chemical effects on the human kidney induced by the chronic ingestion of uranium in drinking water. Subjects were divided into two groups: The low-exposure group, whose drinking water was obtained from a municipal water system and contained < 1 microgram uranium/L, and the high-exposure group, whose drinking water was obtained from private drilled wells and contained uranium levels that varied from 2 to 781 micrograms/L. Years of residence varied from 1 to 33 years in the low-exposure group and from 3 to 59 years in the high-exposure group. The indicators of kidney function measured in this study included glucose, creatinine, protein, and beta 2-microglobulin (BMG). The markers for cell toxicity studied were alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT), lactate dehydrogenase (LDH), and N-acetyl-beta-D-glucosaminidase (NAG). Urinary glucose was found to be significantly different and positively correlated with uranium intake for males, females, and pooled data. Increases in ALP and BMG were also observed to be correlated with uranium intake for pooled data. In contrast, the indicators for glomerular injury, creatinine and protein, were not significantly different between the two groups nor was their urinary excretion correlated to uranium intake. These results suggest that at the intakes observed in this study (0.004 microgram/kg to 9 micrograms/kg body wt), the chronic ingestion of uranium in drinking water affects kidney function and that the proximal tubule, rather than the glomerulus, is the site for this interference.

Comparison of the ANSI, RSD, KKH, and BRMD thyroid-neck phantoms for 125I thyroid monitoring.

The Human Monitoring Laboratory, which acts as the Canadian National Calibration Reference Centre for In Vivo Monitoring, has determined the performance characteristics of four thyroid phantoms for 125I thyroid monitoring. The phantoms were a phantom built to the specifications of the American National Standards Institute Standard N44.3; the phantom available from Radiology Support Devices; the phantom available from Kyoto Kagaku Hyohon; the phantom manufactured by the Human Monitoring Laboratory and known as the BRMD phantom. The counting efficiencies of the phantoms for 125I were measured at different phantom-to-detector distances. The anthropomorphic characteristics of the phantoms have been compared with the average man parameters. It was concluded that the BRMD, American National Standards Institute, and Radiology Support Devices phantoms have the same performance characteristics when the neck-to-detector distances are greater than 12 cm and all phantoms are essentially equivalent at 30 cm or more. The Kyoto Kagaku Hyohon phantom showed lower counting efficiencies at phantom-to-detector distances less than 30 cm. This was attributed to the design of the phantom. This study has also shown that the phantom need not be highly anthropomorphic provided the calibration is not performed at short neck-detector distances. Indeed, it might be possible to use t simple point source of 125I placed behind a 1.5 cm block of lucite at neck detector distances of 12 cm or more.

The Canadian National Calibration Reference Centre for In-Vivo Monitoring: thyroid monitoring. Part V: Minimizing placement error in a thyroid monitoring system.

This article is the last of a five-part series covering various aspects of occupational thyroid monitoring. This part describes the techniques for minimizing errors due to improper placement of the detector. The impact of counting time and minimum detectable activity as a function of detector position are also discussed. The importance of minimum detectable activity is exemplified by showing how it can be used to ensure that the thyroid monitoring system can detect an amount of radioactivity below the derived investigation level.

The Canadian National Calibration Reference Centre for In-Vivo Monitoring: thyroid monitoring. Part IV: Optimizing a counting system that uses a single-channel analyzer.

This article is the fourth of a five-part series covering various aspects of occupational thyroid monitoring. This article describes the energy calibration of the monitoring system with particular emphasis on techniques for optimizing a system that is based on a single-channel analyzer, or any system that does not have a multi-channel analyzer. These systems cannot directly show the operator the photopeak of the calibration source. The article also briefly discusses quality control and problem solving.

The Canadian National Calibration Reference Centre for In-Vivo Monitoring: thyroid monitoring. Part III: A basic calibration procedure for thyroid monitoring.

This article is the third of a five-part series covering various aspects of occupational thyroid monitoring. This article introduces the basic concepts required to understand the procedure for determining the counting efficiency of a thyroid detector. The B.R.M.D. thyroid-neck phantom is used as the calibration source. A procedure for personnel monitoring is also discussed and the concept of Minimum Detectable Activity (MDA) is introduced. The last two articles in this series discuss energy calibration, counting system optimization based on a single-channel analyzer and placement error minimization.

The Canadian National Calibration Reference Centre for In-Vivo Monitoring. Part II: Sources of errors in thyroid monitoring of occupationally exposed personnel.

This article, the second of a five-part series covering various aspects of occupational thyroid monitoring, addresses the sources of error that can affect the final result obtained from thyroid monitoring, such as geometry effects (thyroid size, thyroid depth, precision and accuracy of the detector placement, and neck-detector distance). The article also suggests ways in which these errors can be minimized and identifies those errors that are difficult to quantify.

The Canadian National Calibration Reference Centre for In-Vivo Monitoring: thyroid monitoring. Part I: The national inter-comparison programme.

This article is the first part of a five-part series covering various aspects of occupational thyroid monitoring. The Canadian National Calibration Reference Centre for In-Vivo Monitoring conducts a thyroid inter-comparison programme that now includes more than 100 facilities. The scope of the programme, begun in 1988, has greatly expanded in the last two years following a considerable effort to locate and inform facilities. This article presents the details of the programme, its results, and the lessons learned. Subsequent articles will discuss sources of errors, methodology, instrumental configuration, and counting geometry optimization.