Narrow Results

Space exploration poses health hazards to the crews of manned missions. Exposure to cosmic radiation and loss of bone density are considered the two most important risk factors for long-term missions. Stochastic risk deriving from cosmic radiation exposure can be estimated by physical dosimeters, using appropriate conversion factors. Recent measurements of space radiation fluence and energy spectra will improve current estimates. Biological dosimetry can be used as a tool to determine the risk directly from biological damage. Chromosomal aberrations in astronauts' peripheral blood lymphocytes have been used as a biomarker of cancer risk. In this paper we will also discuss countermeasures to radiation damage, focusing on the problem of shielding in space.

This paper reviews issues of biological effects and safety aspects of the electromagnetic fields related to both Magnetic Resonance Imaging (MRI) and Transcranial Magnetic Stimulation (TMS) as a diagnostic technique. The noninvasive character of these diagnostic techniques is based on the utilization of the electromagnetic fields such as the static magnetic field, time-varying magnetic field, and radiofrequency electromagnetic field. Following the short view of the history and the principle of these noninvasive techniques, we review the biological effects of the electromagnetic fields, the health effects and safety issues related to MRI/TMS environments. Through a discussion of biological and health effects, it shows briefly guidelines which provide a consideration in human risk for both patients and medical staff. Finally, safety issues related to MRI/TMS are discussed with the highlighting of the guideline such as the International Commission on NonIonizing Radiation Protection (ICNIRP) and EMF Directive (Directve2013/35/EU) of European Union.

The study of the biological effect of ultrasound on tissue has become an important branch of biophysical ultrasonics. Among the important biological effects, which have been discovered, are chromosomal anomalies, cell death, destruction of cellular structures. Although heating may be important in some results, nonthermal mechanics, such as cavitation, are often suggested as being responsible for the observed effects.

In this paper, the biological subject of this study is the red blood cells (RBC); the relationship between the threshold lesion of RBC and frequency of ultrasound was studied. It has been concerned that a suitable frequency value of ultrasound was selected, capable of driving the bubbles to an interesting reaction. The effective mass of the bubble.for the oscillating system is due to the motion of the surrounding medium. For the purposes, by using the approximate expressions for the effective stiffness and mass of a gas body, one can determine the resonance frequency of the gas body. In the closed system, three types of frequencies were employed with different pressure. The cell death threshold varies with the ultrasonic frequency of exposure, the minimum at about 10 MHz. This report is intended to provide a useful way for the study of the biological effect of ultrasound at medically relevant frequencies.

The effects of ultrasonic irradiation at different frequencies, i.e. 0.25, 0.5, 1, and 5 MHz, on the activation of the single cell creature biological reaction have been investigated. The ability shown by ultrasound in promoting and/or accelerating many reactions has been shown to be a useful field. The resonance frequency of Paramecium by using the ultrasound irradiation is an important parameter in this study. All other parameters being keep constant, it has been ascertained that an appropriate frequency value of ultrasound can be selected, capable of driving a biological reaction to its suitable yield. The oscillation of the cells in response to the ultrasound radiation is simulated using Rayleigh-Plesset's bubble activation theory. The resonance frequency of the unicellular creature is then calculated. In our experiment, the resonance (0.5 and 1 MHz) and non-resonance (0.25 and 5 MHz) frequencies were employed.

The resonance frequency of the Paramecium vacuole is among 0.5013 ∼ 1.2703 MHz. When the 0.5 and 1 MHz frequencies of ultrasound was irradiated in the samples, the relative growth rate was about 30% higher than that of unexposed sample. It is obviously that the inhibition or enhancement growth conditions did not appear during irradiation the non-resonance frequency ultrasound. In addition, experimental evidence suggests that the sustaining growth effect can be expected, when the irradiation time is divided into parts.

This paper investigates the biological reactions of unicellular creature irradiated to a low intensity of ultrasonic field. The current study attempts to anticipate the value of the ultrasonic driving frequency which will induce the most significant biological reactions by using the theoretical model. The theoretical model of the cells in response to the ultrasonic irradiation is simulated using Rayleigh–Plesset's bubble activation theory. The simulation results indicate that the resonant frequency of the Paramecium vacuoles considered in the present study lies in the range 0.54–1.24 MHz. Ultrasonic irradiation experiments are performed at various power level intensities at driving frequencies corresponding to resonant (0.5 and 1 MHz) and nonresonant (0.25 and 5 MHz) frequencies. It is found that samples irradiated under different ultrasonic conditions exhibit clear differences in their cell proliferation tendencies. For example, in samples irradiated with lower power intensities and driving frequencies of 0.5 and 1 MHz, the number of cells in the treated samples is found to be approximately 30% higher than that in the original unexposed samples. However, when resonant frequencies and higher intensities are applied, the ultrasonic irradiation causes a shape change of the cell organelles and a corresponding reduction in the total number of cells in the treated sample. For the samples exposed to nonresonant frequency ultrasonic irradiation, it is found that the cell proliferation is limited and appears to vary independently of the applied irradiation intensity.

Potential biological effects initiated by exposure to ionizing radiation are described in some detail, including the characteristics of radiation sources, radiation fields, dosimetry, and fundamental radiation protection quantities and units. Special attention is paid to exposure pathways and the risk assessment of radiation exposure to the human body in terms of relevant health risks reflecting biological effects resulting from external and internal radiation exposure. Some particulars are presented to illustrate the nature and severity of stochastic and deterministic effects caused by the exposure. The chapter then presents an overview of pertinent radiation protection requirements and monitoring methods for the evaluation of exposure of persons in regular and emergency situations, as well as the assessment of environmental radioactive contamination inflicted by releases of radioactivity from facilities where radioactive materials are used or stored, taking into account their possible damage or destruction resulting from accidents and potential terrorist attacks, sabotage, or other malevolent actions. In all these cases, discharges of radioactive substances from various sources, including those used in medicine, industry, and research facilities, should be considered to obtain reliable information about specific radiation routes. Radioactive materials, in the form of solid particulates, aerosols, and gases, disperse in several ways known as exposure pathways. It is essential that the description of both exposure pathways and their characteristics be expressed in officially recommended and generally accepted quantities and units. In general, the final part of an exposure pathway refers to how a person can come into contact with hazardous substances, including materials containing radionuclides.

Radionuclides are present in the environment or result from human activities, such as the use of radiation or nuclear technologies. The presence of radionuclides in foods can pose certain health risks, and their toxicity depends on several factors, including the intake of radionuclides, the type of radionuclide, its concentration, and the specific characteristics of the food. Under typical situations, the contributions of internal exposure to the human body from food or water, where only trace concentrations of usually natural radionuclides are present, are minor in most cases. Slightly different situations may occur when food, due to radionuclides from man-made sources used in various applications in industry and medicine or radioactivity induced during radiation sterilization of food, shows an increased level compared with the natural background concentrations. But even here, there is no reason to consider the impact on living organisms to be serious since the increase in exposure levels is only a fraction of exposure due to the natural background.

On the other hand, however, the concentration may be higher in some cases when the food is produced from plants or animals that are heavily contaminated. Specific aspects of radioactivity or, in general, ionizing radiation (hereinafter, simply, radiation), which can be detected even at particularly small levels thanks to the availability of very sensitive instrumentation, have to be stressed here. Radiation monitors are able to measure even extremely insignificant changes within the fluctuation level of natural radiation. When the instrument shows some results close to the background level or even up to several times this level, there is no need to be concerned since the impact of such exposure on a person is almost negligible in comparison with other, much more dangerous situations we face daily in our typical living or working environment caused by many other, much more hazardous agents. The chapter will present an overview of the health risks attributed to the toxicity resulting from exposure to foods contaminated by radionuclides of various origins.

Space exploration poses health hazards to the crews of manned missions. Exposure to cosmic radiation and loss of bone density are considered the two most important risk factors for long-term missions. Stochastic risk deriving from cosmic radiation exposure can be estimated by physical dosimeters, using appropriate conversion factors. Recent measurements of space radiation fluence and energy spectra will improve current estimates. Biological dosimetry can be used as a tool to determine the risk directly from biological damage. Chromosomal aberrations in astronauts' peripheral blood lymphocytes have been used as a biomarker of cancer risk. In this paper we will also discuss countermeasures to radiation damage, focusing on the problem of shielding in space.