The text consists of two sections, one for those studying or practicing diagnostic radiology, nuclear medicine and radiation oncology; the other for those engaged in the study or clinical practice of radiation oncology--a new chapter, on radiologic terrorism, is specifically for those in the radiation sciences who would manage exposed individuals in the event of a terrorist event. The 17 chapters in Section I represent a general introduction to radiation biology and a complete, self-contained course especially for residents in diagnostic radiology and nuclear medicine that follows the Syllabus in Radiation Biology of the RSNA. The 11 chapters in Section II address more in-depth topics in radiation oncology, such as cancer biology, retreatment after radiotherapy, chemotherapeutic agents and hyperthermia.

Radiobiology for the Radiologist

Micronucleus assays with fish have been shown to be useful in vivo techniques for genotoxicity testing, and show potential for in situ monitoring of water quality In this paper, we review the literature on the clastogenic effects of chemical and physical agents on fish cells, with emphasis on the induction of micronuclei in teleosts Included in the review is a description of the mechanisms for formation of micronuclei in cells, and a summary of the various techniques that have been used for micronucleus analysis in fish This review is directed to assisting laboratories in the development of fish genotoxicity assays for water quality monitoring

Fish micronuclei for assessing genotoxicity in water

In concert with the development of new materials in the last decade, the need for toxicological studies of these materials has been increasing. These new materials include a group of rare earths (RE). The use of RE nanotechnology is being considered in some green applications, to increase their efficiency by using nano-sized RE compounds, and therefore hazard evaluation and risk assessment are highly recommended. This review was conducted through an extensive contemplation of the literatures in toxicology with in vitro and in vivo studies. Major aspects reviewed were the toxicological evaluations of these elements and metallic compounds at the molecular and cellular level, animal and human epidemiological studies and environmental and occupational health impacts on workers. We also discuss the future prospect of industries with appliances using RE together with the significance of preventive efforts for workers’ health. To establish a safe and healthy working environment for RE industries, the use of biomarkers is increasing to provide sustainable measure, due to demand for information about the health risks from unfavorable exposures. Given the recent toxicological results on the exposure of cells, animals and workers to RE compounds, it is important to review the toxicological studies to improve the current understanding of the RE compounds in the field of occupational health. This will help to establish a sustainable, safe and healthy working environment for RE industries.

Toxicological Evaluations of Rare Earths and Their Health Impacts to Workers: A Literature Review

The micronucleus test in piscine erythrocytes.

Our aim is to develop and evaluate monitoring systems that use aquatic organisms to assess the genotoxicity of water in the field and in the laboratory. In a field study, we have shown that the micronucleus assay is applicable to freshwater and marine fishes and that gill cells are more sensitive than hematopoietic cells to micronucleus-inducing agents. Gill cells from Carassius sp. (Funa) and Zacco platypus (Oikawa) collected upstream on the Tomio River (Nara, Japan), tended to have lower micronucleus frequencies than gill cells from fish collected at the midstream of the river. Leiognathus nuchalis (Hiiragi) and Ditrema temmincki (Umitanago), small marine fishes collected periodically at Mochimune Harbor (Shizuoka, Japan), showed seasonal differences in the frequencies of micronucleated gill cells and erythrocytes; they were highest in summer. For laboratory studies, we developed a method for analyzing chromosomal aberrations and micronuclei using Rhodeus ocellatus ocellatus (rose bitterling) embryos. One day after artificial insemination (gastrula stage), we observed structural chromosomal aberrations and micronuclei in the cells of embryos grown in water containing trichloroethylene. Although more work is needed to fully assess their sensitivity, these assays show promise as a means of detecting environmental genotoxins.

Development of genotoxicity assay systems that use aquatic organisms

An in vivo study on the effects of both physical (gamma-radiation) and chemical (mitomycin C) genotoxic agents was carried out with the catfish species, Clarias gariepinus. The fish were either exposed to gamma-radiation at doses of 0-9 Gy or injected intraperitoneally with mitomycin C at concentrations of 0-2 mg/kg. Micronucleated erythrocytes were sampled from 0 to 60 days post treatment. Data obtained showed a time-dependent response of the induction of micronucleated erythrocytes with both genotoxic agents. A linear dose-dependent increase was observed 2-4 days after treatment. These data show the importance of sampling time in the micronucleus assay with Clarias gariepinus.

Micronucleated erythrocytes as an assay to assess actions by physical and chemical genotoxic agents in Clarias gariepinus.

Radioactivity and radiological risk associated with effluent sediment containing technologically enhanced naturally occurring radioactive materials in amang (tin tailings) processing industry.

Previous studies have shown that the natural radioactivity contained in building materials have significantly influenced the dose rates in dwelling. Exposure to natural radiation in building has been of concerned since almost 80 % of our daily live are spend indoor. Thus, the aim of the study is to assess the radiological risk associated by natural radioactivity in soil based building materials to dwellers. A total of 13 Portland cement, 46 sand and 43 gravel samples obtained from manufacturers or bought directly from local hardware stores in Peninsular of Malaysia were analysed for their radioactivity concentrations. The activity concentrations of 226Ra, 232Th and 40K in the studied building materials samples were found to be in the range of 3.7–359.3, 2.0–370.8 and 10.3–1,949.5 Bq kg−1 respectively. The annual radiation dose rates (μSv year−1) received by dwellers were evaluated for 1 to 50 years of exposure using Resrad-Build Computer Code based on the activity concentration of 226Ra, 232Th and 40K found in the studied building material samples. The rooms modelling were based on the changing parameters of concrete wall thickness and the room dimensions. The annual radiation dose rates to dwellers were found to increase annually over a period of 50 years. The concrete thicknesses were found to have significantly influenced the dose rates in building. The self-absorption occurred when the concrete thickness was thicker than 0.4 m. Results of this study shows that the dose rates received by the dwellers of the building are proportional to the size of the room. In general the study concludes that concrete building materials; Portland cements, sands, and gravels in Peninsular of Malaysia does not pose radiological hazard to the building dwellers.

Radiological dose assessment of naturally occurring radioactive materials in concrete building materials

Gamma spectroscopy was performed to determine the concentrations of uranium-238 and thorium-232 concentrations in the environment as a consequence of amang processing. In this study 33 water samples and 26 sediment samples were collected from 7 amang processing areas. The concentrations of uranium-238 and thorium-232 were determined by direct counting using a hyper pure germanium (HPGe) detector inter phased with a multi channel analyzer (MCA) . Results showed that the maximum mass and activity concentrations of uranium in water samples were 6.64 ppm and 78.53 Bql -1 respectively, while in sediment samples were 69.75 mgkg -1 and 860.57 Bqkg -1 respectively. The maximum mass and activity concentrations of thorium in water samples were 1.71 ppm and 6.90 Bql -1 , while in sediment samples were 157.73 mgkg -1 and 637.61 Bqkg -1 respectively. Concentrations of uranium-238 and thorium-232 in sediment samples were higher than concentrations of uranium-238 and thorium-232 in water samples, and this may be attributed to insolubility of these radionuclides in water. The concentrations of both radionuclides were higher in sediments collected from ponds involved in the close water recycle system compared to those ponds involved in the open water system. Results also showed that the concentrations of these radionuclides were higher than background indicating that amang processing activity has enhanced the natural radionuclides contents in water and sediment.

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Assessment of natural radioactivity in water and sediment from amang (tin tailing) processing ponds

The usefulness of peripheral human lymphocytes as a bioindicator for ionizing radiation effect was tested in a survey of Malaysian workers in two industries producing technologically enhanced naturally occurring radioactive material (TENORM). Workers in amang processing plants who have been with the plant for an average of 12.9 years and who were exposed to radioactive dust showed significantly higher frequencies of chromosomal aberration compared to control and even ilmenite-processing workers. Such frequency was not significantly different between workers in ilmenite-processing plant and control. The differences in duration of employment, occupational hygiene, together with the difference in the percentage of ‘old’ and ‘new’ aberrations among the groups sampled were used to explain the high chromosomal aberration frequency among amang workers. The presence of significantly high chromosome damage (dicentrics and fragments) in workers who were chronically exposed to doses below 50 mSv per year or 20 mSv per year averaged over 5 years (ICRP, 1991) provided additional experimental data on the dose-effect relationship at these low-dose ranges. The results confirm the usefulness of using human lymphocytes as a bioindicator for chronic exposure to ionizing radiation and in cases where physical radiation detectors are not available.

Ismail Bahari

Papers

Micronucleated erythrocytes as an assay to assess actions by physical and chemical genotoxic agents in Clarias gariepinus.

Radioactivity and radiological risk associated with effluent sediment containing technologically enhanced naturally occurring radioactive materials in amang (tin tailings) processing industry.

Radiological dose assessment of naturally occurring radioactive materials in concrete building materials

Assessment of natural radioactivity in water and sediment from amang (tin tailing) processing ponds

Radiation-induced chromosomal aberrations among TENORM workers: amang- and ilmenite-processing workers of Malaysia