Radon in the indoor environment is a recognized environmental hazard. The Environmental Protection Agency (EPA) has established several programs to develop, demonstrate, and transfer radon mitigation technology. Administration and management of these programs are shared by EPA's Office of Radiation Programs and Office of Research and Development. One measure of success of these programs is that, by 1990, approximately 90,000 houses have been professionally mitigated in the United States. Future success depends, in part, upon strong motivational campaigns conducted in local communities with regional and national support.
Nitrogen in the human body is measured in vivo using prompt neutron capture gamma-rays. The quantity of nitrogen can then be used as measured of protein. Data are presented on three groups of subjects; volunteers of different ages, those with liver ailments, and those on peritoneal dialysis. The data show that the nitrogen measurements given information (in accord with clinical findings) which is not given by indirect methods of estimating lean body mass.
Neutron activation analysis provides a useful clinical test to assess bone mass status in vivo. The neutron flux is obtained from Pu/Be sources and49Ca activity is measured by NaI detectors. For diagnostic value, the49Ca measurement is related to the mean value for normal subjects of the same body size. This normalized index, our CaBI, is used extensively to diagnose the bone loss associated with osteoporosis and to asses changes in bone mass with progression of disease and in response to treatments. Our facility operates at maximum capacity (35 tests/wk.). The hospital location and the dependability and ease of operation (provided by neutron sources) have facilitated extensive clinical use.
Authors:S. Krishnan, J. Mernagh, A. Hitchman, K. McNeill and J. Harrison
A procedure has been developed to measure fluoride concentration in bone biopsies by neutron activation analysis /NAA/. The NAA procedure is non-destructive so that the bone biopsies can be used subsequently for histological evaluation. The fluoride content is expressed as F/Ca ratio in the bone samples. The fluoride and calcium are measured using the reactions:19F/n, /20F /t=11.2 s/ and48Ca/n,/49Ca/t=8.8 m/, respectively. The F/Ca ratio normalizes the fluoride to bone mineral avoiding the use of bone weight which is unreliable with fresh biopsy samples. This ratio also corrects for variations in neutron flux and gamma counting efficiencies. Results by this procedure were compared to biochemical determinations using an ion-selective electrode for fluoride and atomic absorption for calcium. The two methods gave results which agreed within ±5% which is the precision of the NNA procedure. The NAA method provides a simple and non-destructive procedure for fluoride measurement in bone biopsies for clinical studies. The method is now routinely used in our clinical studies for the fluoride measurements on biopsies from osteoporotic patients treated with fluoride therapy for nearly four years.
Authors:J. Lawry, A. Ray, D. Klimesch, P. Thomas, J.-P. Guerbois and J. Harrison
Summary Due to growing environmental concerns and the need to use less energy-intensive building products, alternatives and improvements to Portland cement (PC) are being actively researched worldwide. Use of supplementary materials is now a common practice where PC is the predominant component of inorganic building products. This study aims to investigate the potential of magnesia (MgO), derived from a naturally occurring raw material magnesite, as a supplementary material. Results from mortar samples prepared with 10 and 20% replacements of ordinary Portland cement (OPC) by MgO are presented. DTA-TG was used to study and characterise the hydration behaviour of MgO in OPC environment after 3, 7, 14, 28, 56 and 90 days of moist curing. Microstructural and compressive strength determinations providing additional information on the influence of hydrated phases are also reported.
Authors:S. Krishnan, M. Bayley, A. Hitchman, S. Lin, K. McNeill and J. Harrison
This work describes an in vivo neutron activation analysis facility for small samples, such as rats or human hand, using two 100 g252Cf neutron sources. The irradiation area is a cylindrical space, of 12 cm diameter and about 15 cm length, with fairly uniform neutron flux distribution. Experimental data on the reproducibility, effects of volume and other conditions for in vivo measurements are given. Comparative atomic absorption data on calcium measurements on rats are reported. The facility is now used for animal experiments as well as human hand irradiations in clinical investigations involving calcium metabolism and bone diseases.
Authors:S. Krishnan, J. Harrison, R. Jervis, A. Hitchman, R. Dowlati, S. Lui and B. Krishnan
Flameless Atomic Absorption Spectrophotometry was found to be a sensitive (2·10–12 g detection limit), accurate but destructive method for cadmium assay in bone biopsy samples (about 30 mg dry weight). The inductively coupled plasma emission technique was poorer in sensitivity (1.2·10–9 g) and is also a destructive method. Activation Analysis is still less sensitive (2·10–8 g detection limit) but a nondestructive one. Cadmium was found to accumulate in bone of rats fed, for 5 weeks, 0, 50, and 100 mg Cd/l in drinking water and the bone concentrations were 0.16, 1.09, and 2.6 mg Cd/kg bone (dry wt). Histological examination of the bones showed that cadmium induced increased osteoid surface in the bone with no evidence of accompanying kidney damage. This suggests a primary effect of cadmium on bone rather than secondary effect due to kidney damage.
Authors:J. Harrison, S. Krishnan, C. Muller, A. Strauss, S. Mukherjee and W. Sturtridge
The accuracy of dual energy X-ray absorptiometry (DEXA) for measurement of bone mass carried out by quantitative digital radiography (Hologic Inc.) was compared to results with neutron activation analysis (NAA) on 106 subjects. The accuracy with DEXA was further investigated by measurements on aluminium samples of known composition. DEXA measured 4 lumbar vertebrae by spine scan. The central third of the skeleton also was measured by whole body scan to obtain data on the same large part of the skeleton as measured by NAA. Results suggested that DEXA spine scans were more reliable than whole body scans. In addition, the measurement of total mineral content (BMC) was more reliable than the normalization of BMC to bone surface area (BMC/Area) or bone mineral density (BDM). Since the proportion of bone below detection would increase with development of osteoporosis, with osteoporosis the BMC would be increasingly underestimated, but to only a small extent, while the BMD would be more significantly overestimated.
Authors:E. Bogdanovich, S. Krishnan, S. Lui, R. Hancock, Y. Pei, G. Hercz and J. Harrison
A non-destructive method based on instrumental neutron activation analysis (INAA) for the assay of aluminum in bone samples is described. The28Al signal obtained upon neutron irradiation includes contributions from both the reaction27Al(n,)28Al and31P(n,)28Al. The first reaction is with the thermal neutrons and the second one is with the fast neutrons. The contribution from the31P reaction is calculated from the fact that Ca/P ratio in bone mineral is constant and the amount of calcium can be measured from the thermal reaction48Ca(n, )49Ca. The aluminum values obtained by the INAA procedure agreed within 10% of those obtained by atomic absorption spectrophotometry. With this assay the levels of aluminum in normal bones (<70 g g–1 apatite) cannot be determined reliably but higher aluminum levles in bone biopsies associated with Al toxicity, e.g. some patients with renal osteodystrophy, can be determined with a precision of ±10%.