Background Radiation

This paper describes the analysis of L-band radiometric measurement data gathered with the synthetic aperture radiometer HUT-2D during several ground-based and airborne measurement campaigns. The radiometric data are analyzed from the instrument's performance point of view, aiming to verify the theoretical performance of an instrument of this kind and to assess the performance of the HUT-2D radiometer system in particular. The data sets considered for the study consist of measurements of well-known natural targets, such as cosmic background radiation, and measurements of pure water scenes, the brightness temperature of which is possible to model based on in situ measurements. We define four figures of merit, which are applicable for synthetic aperture radiometers. These are radiometric resolution, image bias, pixel-to-pixel random error, and temporal stability. Then, we use the selected data sets to assess these in the case of HUT-2D. The experimental results are discussed and compared to the theoretical values, where applicable. Also, we discuss possibilities to improve the presented performance. The main results of this paper are the consolidated performance parameters of the HUT-2D instrument. We study and discuss the properties of the error components related to the technology in a general level, and study the scalability of the errors as a function of the measured targets. In particular, the stability of the direction-dependent error component is pointed out, and a mitigation guideline is proposed.

We calculate the incoherent resonant and non-resonant scattering production of sterile neutrinos in the early universe. We find ranges of sterile neutrino masses, vacuum mixing angles, and initial lepton numbers which allow these species to constitute viable hot, warm, and cold dark matter (HDM, WDM, CDM) candidates which meet observational constraints. The constraints considered here include energy loss in core collapse supernovae, energy density limits at big bang nucleosynthesis, and those stemming from sterile neutrino decay: limits from observed cosmic microwave background anisotropies, diffuse extragalactic background radiation, and Li-6/D overproduction. Our calculations explicitly include matter effects, both effective mixing angle suppression and enhancement (MSW resonance), as well as quantum damping. We for the first time properly include all finite temperature effects, dilution resulting from the annihilation or disappearance of relativistic degrees of freedom, and the scattering-rate-enhancing effects of particle-antiparticle pairs (muons, tauons, quarks) at high temperature in the early universe.

The uranium mines at Jaduguda and nearby areas of the Singhbhum thrust belt of Jharkhand State are the only operating mines in India, which supply fuel to nuclear power plants. The gamma radiation dose rates observed at different locations 1 m above the tailings surface vary from 0.8 to 3.3 μGy h−1. The geometric mean activity concentration of 222Rn in air over the tailings ponds I and II were found to be 30 and 23 Bq m−3, respectively, but reduces to the local background level at the boundaries of the tailings ponds. The uranium and 226Ra levels in the ground water sources in the vicinity of the tailings pond are very similar to the regional average of 3.6 μg L–1 and 23 mBq L−1, respectively, indicating that there is no ground water migration of radioactive material from the tailings pond. This paper gives a brief account of the environmental radioactivity monitoring during uranium mining, ore processing and waste management operations.

The potential role of cosmic topological defects has raised interest in the astrophysical community for many years now. In this set of notes, we give an introduction to the subject of cosmic topological defects and some of their possible observable signatures. We begin with a review of the basics of general defect formation and evolution, we briefly comment on some general features of conducting cosmic strings and vorton formation, as well as on the possible role of defects as dark energy, to end up with cosmic structure formation from defects and some specific imprints in the cosmic microwave background radiation from simulated cosmic strings. A detailed, pedagogical explanation of the mechanism underlying the tiny level of polarization discovered in the cosmic microwave background by the DASI collaboration (and recently confirmed by WMAP) is also given, and a first rough comparison with some predictions from defects is provided.

Natural radiation is the major source of human exposure to ionising radiation, and its largest contributing component to effective dose arises from inhalation of (222)Rn and its radioactive progeny. However, despite extensive knowledge of radiation risks gained through epidemiologic investigations and mechanistic considerations, the health effects of chronic low-level radiation exposure are still poorly understood. The present paper reviews the possible contribution of studies of populations living in high natural background radiation (HNBR) areas (Guarapari, Brazil; Kerala, India; Ramsar, Iran; Yangjiang, China), including radon-prone areas, to low dose risk estimation. Much of the direct information about risk related to HNBR comes from case-control studies of radon and lung cancer, which provide convincing evidence of an association between long-term protracted radiation exposures in the general population and disease incidence. The success of these studies is mainly due to the c...

Non-linear phenomena in biological findings of the residents of high background radiation areas of Ramsar

SMJ Mortazavi, H Mozdarani
International Journal of Radiation Research 01/2013; 11(1):3-9.


ABSTRACT Some Areas of Ramsar, a city in northern Iran are among the world’s well-known inhabited areas with highest levels of natural radiation. Annual exposure levels in these areas are up to 260 mGy y‐1 and the mean exposure rate is about 10 mGy y‐1 for a population of about 2000 residents. If elevated levels of natural radiation as high as a few hundred mSv per year is detrimental to health and leads to higher risks of genetic abnormalities and cancer, it should be evident in the residents of areas such as Ramsar. However, it has been reported that no detrimental biological effects have ever been detected in high natural background radiation areas. Some studies indicate that Ramsar residents not only show a significant increase in DNA repair but also demonstrate induction of radioadaptive response. There is currently a great debate over the shape of the dose‐response curve for stochastic effects such as mutations and cancer after exposure to low doses of ionizing radiation. Linear‐no‐threshold (LNT) model predicts that every dose, no matter how low, carries some cancer risk. Lack of any proven detrimental effect in the residents of high natural background radiation areas of Ramsar may be due to the induction of nonlinear dose‐response relationships which are not compatible with the widely accepted LNT hypothesis.

Lung Cancer in High Background Radiation Areas (HBRAs) of Ramsar

SMJ Mortazavi, Ph.D

Professor of Medical Physics & Radiobiology
Medical Physics & Medical Engineering Department
and the Center for Research on Radiological Sciences
Shiraz University of Medical Sciences
E-mail: mmortazavi@sums.ac.ir

Source: http://www.sums.ac.ir/~mmortazavi/ramsar.html


Humans, animals and plants have been exposed to natural radiation since the creation of life. Interestingly, life evolved in a radiation field that was much more intense than today. The annual effective radiation dose from natural and man-made sources for the world's population is about 3 mSv, which includes exposure to alpha radiation from radon and its progeny nuclides. Nearly 80% of this dose (2.4 mSv) comes from natural background radiation, although levels of natural radiation can vary greatly. Ramsar, a northern coastal city in Iran, has areas with some of the highest levels of natural radiation measured to date. The effective dose equivalents in very high background radiation areas (VHBRAs) of Ramsar in particular in Talesh Mahalleh, are a few times higher than the ICRP-recommended radiation dose limits for radiation workers.
Inhabitants who live in some houses in this area receive annual doses as high as 132 mSv from external terrestrial sources. The radioactivity of the high background radiation areas (HBRAs) of Ramsar is due to Ra-226 and its decay products, which have been brought to the surface by the waters of hot springs. There are more than 9 hot springs with different concentrations of radium in Ramsar that are used as spas by both tourists and residents.
According to the results of the surveys performed to date the radioactivity seems primarily to be due to the radium dissolved in mineral water and secondarily to travertine deposits having elevated levels of thorium combined with lesser concentrations of uranium (Sohrabi 1990). Due to extraordinary levels of natural radiation in these areas, in some cases 55-200 times higher than normal background areas, some experts have suggested that dwellings having such high levels of natural radiation need urgent remedial actions (Sohrabi 1997). In spite of this, many inhabitants still live in their unaltered paternal dwellings.
The preliminary results of cytogenetical, immunological and hematological studies on the residents of high background radiation areas of Ramsar have been previously reported (Mortazavi et al. 2001, Ghiassi-Nejad et al. 2002 and Mortazavi et al. in press), suggesting that exposure to high levels of natural background radiation can induce radioadaptive response in human cells. Lymphocytes of Ramsar residents when subjected to 1.5 Gy of gamma rays showed fewer induced chromosome aberrations compared to residents in a nearby control area whose lymphocytes were subjected to the same radiation dose. Despite the fact that in in vitro experiments lymphocytes of some individuals show a synergistic effect after pretreatment with a low dose(Mortazavi et al. 2000), none of the residents of high background radiation areas showed such a response.
Based on results obtained in studies on high background radiation areas of Ramsar, high levels of natural radiation may have some bio-positive effects such as enhancing radiation-resistance. More research is needed to assess if these bio-positive effects have any implication in radiation protection (Mortazavi et al. 2001). The risk from exposure to low-dose radiation has been highly politicized for a variety of reasons. This has led to a frequently exaggerated perception of the potential health effects, and to lasting public controversies.
Current radiation protection recommendations are based on the predictions of an assumption on linear, no-threshold dose-effect relationship  (LNT).Beneficial effects and lack of detriment after irradiation with low levels of ionizing radiation, including a prolonged exposure to high levels of natural radiation of the inhabitants of HBRAs, are inconsistent with LNT (Mortazavi et al. 1999).
  Our preliminary results suggest that prolonged exposure to very high levels of natural radiation could lead to the induction of radiation resistance among exposed individuals, which has interesting implications for many aspects of radiation protection policy.
The phenomenon of radioresistance in living organisms has long been a matter of interest for scientists. Experiments on Drosophila nebulosa collected in the woods of a high background radiation area in Brazil indicated the addition of some genes caused the radioresistance found in these flies compared to flies collected from adjacent control woods. In humans it is also possible that genetic alterations have occurred over the span of many generations to induce the radioresistance noted in our study. More research is needed to clarify the mechanisms that make individuals radioresistant. 
There are many other areas with high levels of background radiation around the world, and epidemiological studies have indicated that natural radiation in these areas is not harmful for the inhabitants. Results obtained in our study are consistent with the hypothesis that a threshold possibly separates the health effects of natural radiation from the harm of large doses. This threshold seems to be much higher than the greatest level of natural radiation. 

Radon levels in some dwellings of Ramsar are up to 3700 Bq/m3 (over 100 pCi/L). The people and their ancestors exposed to abnormally high radiation levels over many generations. If a radiation dose of a few hundred mSv per year is detrimental to health causing genetic abnormalities or an increased risk of cancer, it should be evident in these people. Ramsar was divided into eight health districts and a health center provided primary health services in each health district. Indoor radon concentration levels were previously measured in each dwelling by the Iranian Nuclear Regulatory Authority experts. The overall cancer mortality, lung cancer mortality and neonatal death rate of different districts in the years from 2000 to 2001 were collected. The radon prone houses were located in a district named Ramak. Our study showed that the highest lung cancer mortality rate was in Galesh Mahaleeh, where the radon levels were normal. On the other hand, the lowest lung cancer mortality rate was in Ramak, where the highest concentrations of radon in the dwellings were found.

References
1. Ghiassi-nejad, M; Mortazavi, SMJ; Cameron, JR; Niroomand-rad, A; Karam, PA; Very High Background Radiation Areas of Ramsar, Iran: Preliminary Biological Studies. Health Physics, 82(1): 87-93, 2002.

2. Mortazavi SMJ, M. Ghiassi-Nejad and M. Rezaiean. Cancer risk due to exposure to high levels of natural radon in the inhabitants of Ramsar, Iran in: High Levels of Natural Radiation and Radon Areas: Radiation Dose and Health Effects, T. Sugahara, M. Morishima, M. Sohrabi, Y Sasaki, I. Hayata, and S. Akiba Eds, pp. 436-437, Elsevier, Amsterdam, 2005.

3. Mortazavi, S.M.J., Karam, P.A. Apparent lack of radiation susceptibility among residents of the high background radiation area in Ramsar, Iran: can we relax our standards? (2005) Radioactivity in the Environment, 7 (C), pp. 1141-1147.

4. Mortazavi, S.M.J., Shabestani-Monfared, A., Ghiassi-Nejad, M., Mozdarani, H. Radioadaptive responses induced in lymphocytes of the inhabitants in Ramsar, Iran (2005) International Congress Series, 1276, pp. 201-203.

5. Mortazavi SMJ, Mozdarani H. Is it time to shed some light on the black box of health policies regarding the inhabitants of the high background radiation areas of Ramsar? Iranian Journal of Radiation Research. 2012;10(3-4):111-6.

6. Mortazavi SMJ, Niroomand-Rad A, Mozdarani H, Roshan-Shomal P, Razavi-Toosi SMT, Zarghani H. Short-term exposure to high levels of natural external gamma radiation does not induce survival adaptive response. Iranian Journal of Radiation Research. 2012;10(3-4):165-70.

7. Mortazavi SMJ, Mozdarani H. Non-linear phenomena in biological findings of the residents of high background radiation areas of Ramsar. International Journal of Radiation Research. 2013;11(1):3-9.
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We investigate how the temporal coherence interference properties of light in a Michelson-Morley interferometer (MMI), using only a single-photon detector, can be understood in a quantum-optics framework in a straightforward and pedagogical manner. For this purpose we make use of elementary quantum field theory and Glaubers theory for photon detection in order to calculate the expected interference pattern in the MMI. If a thermal reference source is used in the MMI local oscillator port in combination with a thermal source in the signal port, the interference pattern revealed by such an intensity measurement shows a distinctive dependence on the differences in the temperature of the two sources. The MMI can therefore be used in order to perform temperature measurements. A related method was actually used to carry out high precision measurements of the cosmic micro-wave background radiation on board of the COBE satellite. The theoretical framework allows us to consider any initial quantum state. The interference of single photons as a tool to determine the angular peak-frequency of a one-photon pulse interfering with a single-photon reference pulse is, e.g., considered. A similar consideration for coherent laser pulses leads to a different response in the detector. The MMI experimental setup is therefore in a sense an example of an optical device where one can exhibit the difference between classical and quantum-mechanical light using only intensity measurements.