This thesis concerned with iodine status, sources in human body, and measurements especially here in Canada, where iodine status for the Canadian population is not well known. With the recent re-emergence of iodine deficiency among individuals in other industrial countries, understanding the main sources of iodine to the Canadian population is necessary to ensure fortification strategies are justified and effective. Uncertinaty has arisen to the importance of iodized salt recently, along with medical warnings to reduce salt consumbtion. This conflicts give rise to improve scientific research and hone thier methods with new applications. The research question here is that: Can we benefit from the existence of long-lived radioiodine-129 in the environment and explore its potential as a tracer? To answer this question, the study was divided into an introductory chapter contains a review about the topic, then three research chapters. The second chapter was devoted to study the possibility of extracting 129I from human urine. As for third chapter of the thesis, it was about refining a method that already established, and use it to extract 129I from breastmilk using combustion, then determine the radiological dose of 129I in infants’ thyroid. While the fourth chapter was devoted to investigate the main sources of 127I and 129I in the Canadian diet based on daily food consumption and modelling the urinary iodine concentration for adults and infants through the novel application of a well-established compartment model implemented in AMBER. The path of this thesis was crowned with a set of results, which are detailed in the end of each chapter as follow: 1- The advantage of accelerator mass spectrometry (AMS) helps to measure 129I in human urine for the first time. The result for 25 participants from Ottawa ranged from 3.3 x 106 atoms/L to 884 x 106 atoms/L with a median of 108.7 x 106 atoms/L, and the 129I/127I ratio ranged from 7.38 x 10-12 to 3.97 x 10-10 with a mean of 1.3 x 10-10. 2- The concentration of 127I and 129I in Ottawa urine samples were significantly correlated and generally similar to the 129I concentrations and 129I/127I ratios from environmental samples collected around Ottawa. 3- This correlation suggests that 129I could be a potential nutritional tracer of dietary iodine. 4- In chapter 3, the 129I in breastmilk ranged from 1.26x108 atoms/L to 6.64x108 atoms/L with a median of 2.10 x108 atoms/L, and the 129I/127I ratio ranged from 1.27x10-10 to 9.9x10-10 with a median of 2.13x10-10. 5- A correlation was also observed between 127I and 129I concentrations in breastmilk. 6- The isotopic ratios in breastmilk were similar to Canadian cow’s’ milk, indicating that the milk of both cows and humans is a reflection of the 129I concentration of their local environment and the food ingested. 7- Result from chapter 3 confirms that humans are exposed to the 129I from birth through their mother breastmilk, giving them an average dose of 1.10 x10-4 Bq/year and thyroid dose rate equal to 5.92 x10-10 Sv/year. 8- In fourth chapter, the daily milk consumption was measured for 78 mother-infants’ pairs, and ranged from 275 -1202 g/day, with a mean of 731 g/day. This value agrees well with global infant milk intake which estimated at 730g/day. 9- The daily iodine intake from breastmilk ranged from 11.2 µg/day to 476.2 µg/day with a median of 127.9 µg/day. 10- The urinary iodine concentrations were estimated without urine collection using iodine biokinetic model, giving a median urinary iodine concentration (n=78) at 304.7 µg/L. The result was compared to those measured by Health Canada (median= 398.7 µg/L), showing a moderate correlation (r= 0.496). 11- A further comparison of the results was made based on gender shows that the difference between UIC in male and female infants measured by Health Canada and those estimated by AMBER is non-significant. 12- Through AMBER software, the influence of seven common diets on UICs was assessed to determine which foods play an important role in ensuring iodine adequacy. We observed that the main source of iodine in a vegan diet is grain products providing up to 70%, while in remaining diets the main source of iodine was dairy products (50-69%) when they are consumed. 13- The contribution of iodized salt to all Canadian diets was ranked second, after dairy, unless the diet is vegan or ovo-vegetarian, where dairy is not consumed, iodized salt was ranked first. 14- Among 23 scenarios for seven different diets, the urinary iodine-129 concentrations ranged from 1.4 x10-7 to 3.3 x10-7 µg/L with a median of 3.1 x10-7 µg/L, and the isotopic 129I/127I ratio ranged from 1.1 x10-9 to 1.2 x10-8 with a median of 2.8 x10-9. 15- In contrast to stable iodine, the highest isotopic ratio was observed in vegan diet, while the lowest was observed in ketogenic diet. This suggests that grain products are the main contributor of 129I to humans. 16- Despite being the primary contributors of stable iodine (127I), salt and dairy show a lower contribution of 129I. Based on this we can qualitatively predict the source of iodine 127 using isotopic ratio 129I/127I. For example, in cases where the isotopic ratio was between 10-8 and 10-9, therefore, the main sources of iodine in this person may be from grains products, vegetables, and fruits; and in cases where the isotopic ratio was between 10-10 and 10-11, therefore, the main sources of iodine in this person may be from dairy products and some contribution from salt. This study has shown the capability of 129I to be used in biomedical fields. In this thesis 129I used as a nutritional tracer where it helps to detect the sources of stable iodine in human body based on isotopic ratio. The extraction method invented in Chapter 2 can be used to evaluate 129I exposure directly in the human body for those who live nearby nuclear fuel reprocessing plants. An additional application for this method can be in assessing 129I in human to investigate 131I uptake in the event of a nuclear emergency using 129I in urine as a proxy. Moreover, the extraction technique used Chapter 3, can be extended to other biological samples such as thyroid or brain. Furthermore, Chapter 4 shows that with the right estimation of daily iodine intake and urine volume, a biokinetic model of iodine, built in the AMBER software, can predict urinary iodine concentration with a high degree of accuracy without collecting urine samples.

Thesis (MSc)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: The Auger electron emitter iodine-123 was examined in the form of 4- [12311iodoantipyrineand as [12311Nal for its effectiveness in killing cells of different sensitivity to photon irradiation. Micronucleus assays showed that 4- [12311iodoantipyrineis two to three times more effective in cell inactivation than C2311Nai.This can be attributed to the fact that antipyrine, for reason of its lipid solubility, can enter cells and can reach the cell nucleus, whereas C231]Nai is excluded from the cytoplasm. The differential targeting of intra- and extracellular compartments was confirmed by radionuclide uptake experiments. In the nucleus, Auger decay conceivably is located on the DNA where it may invoke high-LET irradiation damage. Irradiation damage by [12311Naisl by long range y-irradiation and hence low-LET. Results of the present study demonstrate however that the enhancement of MN-frequency seen with 4-[123I]iodoantipyrine over [12311Nalis similar for all cell lines and that the narrowing of MN-response expected for 4- [12311iodoantipyrinedoes not occur. Experiments with the free radical scavenger, DMSO, indicated nearly identical dose reduction factors for both iodine-123 carriers. These two observations strongly suggest that the cell inactivation by 4- [12311iodoantipyrine is not by high-LET direct ionisation of DNA, but due to an indirect effect. The indirect radiation effect of Auger decay in the nucleus is attributed to shielding of DNA by histones. Such a protection mechanism is not unrealistic if it is realised that histones and DNA associate in a 1: 1 weight ratio and that higher order folding of the nucleosome chain into solenoids, loops, and chromatids generates considerable protein density. In the nucleosome core, the histone acta mer measures 7 nm and closely approximates the 10 nm dimention of the Auger electron range. It is suggested that the interlacing of protein density with DNA density suppresses direct ionisation from Auger decay at the DNA and directs the majority of Auger decay to the histones. / AFRIKAANSE OPSOMMING: Die Auger-elektron-uitstraler, jodium-123, is ondersoek in die vorm van 4- [123l]jodoantipirien en [12311Nal om die effektiwiteit te bepaal waarmee dit selle met verskillende grade van sensitiwiteit vir fotonbestraling doodmaak. Mikrokerntellings toon aan dat 4-[123I]jodoantipirien selle twee tot drie maal meer effektief inaktiveer as [12311Nal.Dit kan toegeskryf word aan die feit dat antipirien, as gevolg van sy vetoplosbaarheidseienskappe, die selle kan binnedring en die kern bereik, teenoor [12311Nalwat uitgesluit word uit die sitoplasma. Die differensiële blootstelling van intra- en ekstrasellulere gebiede is bevestig deur radionukliedopname eksperimente. In die selkern vind Auger verval waarskynlik by die DNA plaas waar dit hoë-LET stralingskade veroorsaak. Stralingskade afkomstig van [1231]Nalis deur langafstand y-strale en dus lae-LET. Die resultate van die huidige studie bewys egter dat die verhoogde mikrokernfrekwensie van 4-[12311jodoantipirienteenoor [1231]Nal dieselfde is vir al die sellyne en dat die vernouïng van mikrokernreaksie soos verwag met 4- [12311jodoantipirien, nie plaasvind nie. Eksperimente met die vryradikaalopruimer, DMSO, dui op feitlik identiese dosis-modifiseringsfaktore vir beide jodium-123 draers. Hierdie twee waarnemings is 'n besliste aanduiding dat die selinaktivering deur 4-[12311jodoantipiriennie deur hoë-LET direkte ionisering van DNA plaasvind nie, maar eerder deur indirekte stralingsaksie. Die indirekte stralingseffek van Augerverval in die kern kan toegeskryf word aan afskerming van DNA deur histone. So 'n beskermingsmeganisme is nie onrealisties nie, as in ag geneem word dat histone en DNA in 'n 1: 1 gewigsverhouding assosieer en dat hoër orde vouïng van die nukleosoomketting tot solenoïede, lusse en chromatiede 'n beduidende protïendigtheid genereer. In die nukleosoomkern is die histoon-oktameer ongeveer 7 nm in deursnit en dus vergelykbaar met die 10 nm reikafstand van die Auger elektrone. Dit word voorgestel dat die ineengeweefdheid van die protien-digtheid met die DNA-digtheid die direkte ionisering van die DNA tydens Auger verval onderdruk en dat die meeste van die Auger verval in die histone plaasvind.