Effect of physical activity on human potassium metabolism in a hot and humid environment.

Previous investigations have suggested that there are high potassium losses during heavy physical activities in hot climates. In order to determine if high levels of potassium losses could be offset by potassium loading, this study was conducted with five long-distance track runners who had trained in hot and humid environments. The liquid supplements containing 4.3, 98.0, and 0.0 mEq/liter of potassium were given 1 to 2 hr before physical activity. The daily diet contained 2.6 g of potassium. A sodium and potassium balance study was conducted in which stool, urine, and dermal losses were measured. In order to determine if there was a change in the distribution of body potassium during physical exercise, seven subjects total body potassium was estimated before and after exercise. This measurement was performed by counting 40K in a whole body counter. Although the subjects with potassium supplementation and higher urinary sodium and potassium losses, the 98 mEq/liter of potassium supplement resulted in a positive potassium balance. The subjects' potassium requirements exceeded the National Research Council suggested dietary intake. The total body potassium measurements indicated that the counting efficiency of 40K increases significantly immediately after the period of vigorous exercise.

Iron studies in hemophilia.

Although iron deficiency is not recognized as a usual complication of hemophilia, we questioned whether intermittent occult loss of blood in urine or stool might predispose hemophiliacs to chronic iron deficiency. Seven men with factor VII and one with factor IX deficiency were studied. Blood studied, bone marrow aspirates, urine and stool samples, and ferrokinetics with total-body counting up to five months were examined. These data showed no excessive loss of blood during the study period; however, marrow iron stores were decidedly decreased, being absent in four subjects. We suggest that in some hemophiliacs, iron deposits in tissues such as synovial membranes may form a high proportion of the body's total iron stores.

Determination of uranium and thorium concentrations in unprocessed soil samples.

An assay technique that directly determines the amount of 238U and 232Th in unprocessed, bulk soil samples has been developed. In this technique, a sample consisting of a 125-mL plastic bottle full of contaminated, moist, unprocessed soil is irradiated with gamma rays from 57Co. Induced U and Th K alpha fluorescent x rays are detected using a high-purity intrinsic germanium planar detector. Because of sample irradiation geometry, the fluorescent x-ray peaks lie on top of a large Compton backscatter peak. Spectral data are first fit to a combination polynomial and ERFc-step-function background that is subtracted from the peak data. The remaining peak data are fit to a Voigt Profile to properly determine peak area. The Voigt Profile, which is the convolution of the Gaussian response of the detector system and the Lorentzian energy distribution of x rays, describes the spectral peak better than a simple Gaussian distribution. A mathematical point-node model of the source-target-detector system, which includes fluorescent x-ray production by singly scattered Compton gamma s, calculates the predicted x-ray peak area per Bq cm-3 of target contamination. Soil attenuation coefficients, which are measured for each sample, are used by the model to properly transport gamma s and x rays through the soil sample. The sample 238U and 232Th concentrations are then calculated by dividing the measured peak areas by the model-predicted peak areas per Bq cm-3. No "soil standards," no assumptions about progeny equilibrium, and no sample preparation are required for this technique.

Indoor radon progeny exposure in the Florida phosphate mining region: a review.

This paper reviews the data generated in studies of land radioactivity and indoor airborne radon progeny associated with mined and reclaimed phosphate lands in Florida. Highest indoor radon progeny levels are associated with the slab-on-grade type of construction. Concentrations exceeding 0.03 WL are associated with overburden soils, deposits and fill, while concentrations up to about 0.03 WL are associated with tailings. The lower limit for distinguishing increases above non-enhanced natural concentrations is on the order of 0.01-0.02 WL. Results of this study show that about 25% of the land produced by present methods of mining and reclamation practices would require restrictions on the type of construction or would require special construction methods. It is projected that with modification of mining and tailings disposal practices, virtually all of the land produced by mining and reclamation would be satisfactory for unrestricted construction use.

Application of a canine 238Pu biokinetics/dosimetry model to human bioassay data.

Associated with the use of 238Pu in thermoelectric power sources for space probes is the potential for human exposure, primarily by inhalation and most likely as 238PuO2. Several models have been developed for assessing the level of intake and predicting the resulting radiation dose following human exposure to 239Pu. However, there are indications that existing models do not adequately describe the disposition and dosimetry of 238Pu following human exposure. In this study, a canine model that accounts for these differences has been adapted for use with human excretion data. The model is based on existing knowledge about organ retention of plutonium. An analysis of the sensitivity of the model to changes in aerosol-associated properties indicated that predictions of urinary excretion are most sensitive to changes in particle solubility and diameter and in the ratio of fragment:particle surface area. Application of the model to urinary excretion data from seven workers exposed to a 238Pu ceramic aerosol gave estimated intakes of 390-8,200 Bq and associated initial pulmonary burdens of 80-1,700 Bq. The resulting 50-y dose commitments to critical organs per Bq of 238Pu intake were estimated to be 0.5 mSv for the thoracic region, 0.2 mSv for the liver, and 1 mSv for the bone surfaces.