Gerard R. Laurer

X-RAY FLUORESCENCE: DETECTION OF LEAD IN WALL PAINT.

An instrument has been developed for the in situ determination of lead on painted surfaces. It utilizes, as a source of gamma rays, radioactive cadmium-109 and its daughter silver-109 (metastable) to excite the K series x-rays of lead, and a solid-state, lithium-drifted germanium detector. The device, which is capable of detecting 0.26 milligram of lead per square centimeter of paint [approximately 3 percent (by weight) of lead in a single coat] beneath ten layers of lead-free paint, has been tested in a preliminary survey of several tenement apartments in New York City.

In vivo measurement of lead-210 as an indicator of cumulative radon daughter exposure in uranium miners.

The accumulation of lead-2 10 in the human skeleton can be measured in uranium miners by in vivo techniques at body burdens greater than about 4 nCi using transportable equipment designed to detect the 47 keV gamma-ray from this nuclide. A burden of two nanocuries is shown to be equivalent to a calculated cumulative exposure of about 800 workinglevel months. The instrumentation utilizes the Laurer system of twin crystal gamma spectroscopy in which an 8 in. x 1 mm cesium iodide crystal is optically coupled to an 8 in. x 2 in. sodium iodide crystal and is operated in anti-coincidence on a single photomultiplier tube utilizing the principle of rise-time discrimination. The method of measuring aloPb used and the equations used to estimate the cumulative exposure in working-level months are presented, with an evaluation of the uncertainties and the extent to which the estimates can be improved by additional experimental data. The results of field measurements undertaken on the Colorado Plateau showed that, among 37 control subjects with no history of employment in mines, only one individual had counts in excess of two sigma above the mean in the 47 keV region. In contrast, 26 out of 54 mean with uranium mining histories showed counts greater than two sigma above the mean.

95ZR-95NB IN HUMAN LUNGS FROM FALLOUT.

AbstractThe presence of easily measurable quantities of intermediate-lived fission products in ground level air during the first half of 1963 prompted an investigation of the distribution of gamma emitting nuclides in human lungs. Lungs from five cadavers were dissected, ashed and measured for 95Zr

Carbon-14 and tritium measurement by means of bremsstrahlung emissions.

The feasibility of measuring carbon-14 and tritium in vivo has been demonstrated in the rat; thin scintillation detectors were used for the measurement of bremsstrahlung produced by these soft beta emitters. Measurements of tritium in vivo are limited to the study of surface phenomena, whereas bremsstrahlung produced by carbon-14 may be detected from depths of several centimeters.

Low Level in Vivo Measurement of Iodine-131 in Humans

The calibration of a whole body counter for the measurement of pC amounts of I¹³¹ in human thyroids is described. Two 3-in. diameter by 2- in. thick sodium-iodide crystals are used, connected in parallel and placed on each side of the neck over the thyroid area. Thyroid burdens as small as 20 pC may be measured at a 90 per cent confidence level with a 30-min counting period using the in vivo method described. (auth)

ESTIMATION OF THE DISTRIBUTION OF THYROID DOSES IN A POPULATION EXPOSED TO I-131 FROM WEAPONS TESTS.

The mathematical relationships that determine the distribution of thyroid doses in an exposed population are disculations based on both existing data and data yet to be obtained. (P.C.H.)

Long-term retention of 210Pb in man : a unique case of internal contamination

Knowledge of the long-term effective half-life of 210Pb in man is essential for estimating the cumulative exposure to inhaled short-lived radon daughters from measured values of the 210Pb skeletal burden. For this purpose, the effective half-life has been obtained from sequential measurements of 210Pb made in vivo during a 10-y period and by bioassay of 210Pb excreted in the urine of an individual with a 43-y-old body burden. The long-term effective half-lives obtained by these two methods were 18.1 +/- 4.8 y and 15.8 +/- 0.8 y, respectively. These values are not very different from the estimate of 12.3 y previously adopted by the ICRP.

VARIABILITY OF THE I131 CONCENTRATIONS IN THE MILK DISTRIBUTION SYSTEM OF LARGE CITY

—Late in 1962, when dairy products in New York City were contaminated with I131 from U.S.S.R. nuclear tests then in progress, studies were made of the variability of the I131 content of the milk from twenty-one of the milk processing plants in New York City. These measurements, which were made on 4 separate days, indicate that the variations from dairy to dairy were random in nature and that at the end of an extended period of sampling, such as 1 month, the mean concentrations of the milk from the various dairies would not have been significantly different from each other. It is concluded that during the period when the studies were conducted, the practice of analyzing single daily random samples of the milk of New York City provided a satisfactory estimate for the milk supply as a whole.

Variability of the I131 Concentrations in the Milk Distribution System of Large City

Late in 1962, when dairy products in New York City were contaminated with I131 from U.S.S.R. nuclear tests then in progress, studies were made of the variability of the I131 content of the milk from twenty-one of the milk processing plants in New York City. The measurements, which were made on 4 separate days, indicate that the variations from dairy to dairy were random in nature and that at the end of an extended period of sampling, such as 1 month, the mean concentrations of the mill; from the various dairies would not have been significantly different from each other. It was concluded that during the period when the studies were conducted, the practice of analyzing single daily random samples of the milk of New York City provided a satisfactory estimate for the milk supply as a whole.