Search Results

You are looking at 51 - 60 of 334 items for :

  • "population" x
  • Chemistry and Chemical Engineering x
  • All content x
Clear All

Abstract  

The concentrations of trace elements As, Br, Cd, Cr, Cu, Hg, Pb, Sb, Se and Zn in Chinese foodstuffs were determined by instrumental or radiochemical neutron activation analysis or atomic absorption spectrometric methods. 1198 samples including 20–25 kinds of main foodstuffs were analyzed. The results are given and the daily intake of the trace elements for population groups concerned have been calculated.

Restricted access

Abstract  

The paper deals with modeling of -radiation fields produced by natural terrestrial radionuclides in construction materials of houses. Isodoses computed in planes crossing a rectangular room with specified thickness of walls as well as the concentration of radionuclides in building materials enable one to estimate health risks of the population dwelling in such a room.

Restricted access

Abstract  

The occurrence of anomalous enhancements of U-isotope activities in the surrounding environment of a phosphate fertilizer factory complex at the southwest of Spain has been established. It seems that significant amounts of U, released by such industries, are being accumulated in the environment, which may substantially contribute to the collective radiation dose received by the local population.

Restricted access

Abstract  

The concentrations of Cl, K and Na were analyzed in human body fluids (whole blood and serum) using NAA, resulting in the first biochemical baseline values for the Brazilian population. These data permitted us a discussion about the advantages and limitations of using this analytical technique for clinical chemistry.

Restricted access

Abstract  

The number of chromosomal and chromatid breaks, deletions, as well as fragments, have been followed in correlation to the physical dose as assessed by the specific radioactivity of DNA. Human lymphocytes from adult donors were incubated for 44 hours in media supplemented with tritiated thymidine. An uneven distribution of labelling in the cell population has been found and about 50% of the population of cells remained unlabelled. The dose-response curve was flat reflecting loss of damaged cells and/or repair of damage. The dose-response curve showed that at the experimental conditions used the dose of 100 mGy absorbed from incorporated tritium caused about 0.1 deletions per. cell. Doubling the number of deletions to about 0.2 per cell required approximately a five times higher absorbed dose.

Restricted access

Abstract  

Sixteen minor and trace element contents of diet samples collected from the Pratas islanders were determined using instrumental neutron activation analysis. Samples were prepared by the duplicate portion technique, collecting during a 3-day period in winter. Dry weight elemental concentrations and daily dietary intake by islanders are compared with those taken by urban population living in Taiwan, resulting in higher intake of most elements. In addition, concentration of natural radionuclides and artificial fallout in daily diet were determined by means of -spectroscopy; the annual intake of radioactivity was evaluated and compared with those in population of neighboring Taiwan and South China. Features of the elemental concentration and radioactive concentration in the diet are discussed.

Restricted access

Abstract  

Calculation of meaningful minimum detectable concentrations (MDCs) and decision levels (DLs) requires proper evaluation of all uncertainties and biases of the measurement process as determined by appropriate blanks. Using a population of method blank results to estimate blank is appropriate for calculation of MDCs since MDC is an a priori concept and not intended to be sample specific. Using a population of method blanks for calculation of sample specific decision levels (DLs) requires estimation of blank from net counts or count-rate so that sample specific efficiency, recovery, decay correction, and other factors can be used. However, data has shown that DLs calculated as 1.65 sample are easier to implement and compare favorably with DLs calculated as the t blank when a total propagated uncertainty (TPU) is reported by the laboratory and used to estimate sample instead of just the counting uncertainty. DLs calculated in either of these ways resulted in no more than 5% false positives.

Restricted access

Abstract  

XRF and TXRF were established as useful techniques for multi-element analysis of whole blood and human head hair samples. Direct-XRF with different collimation units and different X-ray excitation modes was successfully used for the determination of S, P, K, Ca, Fe, and Br elements in blood samples and K, Ca, Mn, Fe elements in human hair samples. Direct analysis by TXRF was used for the determination of Rb and Sr in digested blood and human hair samples, respectively, while, the co-precipitation method using APDC for TXRF analysis was used for the determination of Ni, Cu, Zn, and Pb elements in both matrices. As a result, the improved XRF and TXRF methods were applied for multi-element determination of elements in whole blood and human hair samples in non-occupational exposed population living in Damascus city. The mean concentrations of analyzed elements in both matrices were on the reported range values for non-occupational population in other countries.

Restricted access

Abstract  

The role of fluorine in human health has become somewhat controversial. It is widely accepted as protective against dental caries, may be protective against osteoporosis, and has been very conservatively implicated with osteosarcoma in male rats. In this study, we repot on the development of a neutron activation analysis method and its application to the analysis of human nails. We have found that toenails collected in population-based epidemiology studies apparently reflect fluoride intake.

Restricted access

Abstract  

Gamma-ray spectrometric measurements of nearground atmospheric aerosols by means of a lead shielded 80 cm3 Ge(Li)-coaxial detector are reported. The dust samples were taken from air-conditioning filters. Data on activity concentration of various natural and man-made airborne radionuclides are given and discussed for the time period from Octobr 1980 to November 1982. These data are useful in estimating the population's radiation burden due to gamma-ray emitting radionuclides.

Restricted access