Alpha particles biological effect

NT089 Piao, C. Q., and T. K. Hei. The biological effectiveness of radon daughter alpha particles. 1. Radon, cigarette smoke and oncogenic transformation. Carcinogenesis 1993 14(3) 497—501. 

Figure 1 Absorbed dose necessary to produce a given biological effect on a given system, in the present case 50% inactivation of V79 hamster cells in exponential growth phase. The dose needed depends on the type of the particles (photons, alpha particles, or uranium ions) and on their energy. (From Ref 15.)...

Alpha particles are much heavier than gamma rays so they can ionize biological materials very effectively. Gamma rays can penetrate long distances but seldom cause ionization. 

Tunneling is a ubiquitous phenomenon. It is observed in biological systems (1), and in electrochemical cells (2). Alpha particle disintegration (3), the Stark effect (4), superconductivity in thin films (5), field-electron emission (6), and field-ionization (7) are tunneling phenomena. Even the disappearance of a black hole (or the fate of a multi-dimensional universe) may depend on tunneling, but on a cosmological scale (S-9). 

Radiation is a phenomenon characterized more by its ability to canse biological effects than where it originates. Radiation was hrst discovered by German scientist Antoine Henri Becquerel, who received the Nobel Prize of Physics in 1903 for his work. Many of the terms associated with radioactivity come from those early pioneers in radiation physics Wilhelm Conrad Roentgen (1845-1923) and Pierre (1859-1906) and Marie Curie (1867-1934), who also received the Nobel Prize in Physics in 1903 for their work on radiation. Ernest Rutherford (1871-1937) is considered the father of nuclear physics. He developed the language that describes the theoretical concepts of the atom and the phenomenon of radioactivity. Particles named and characterized by him include the alpha particle, beta particle, and proton. Rutherford won the Nobel Prize for Chemistry in 1909 for his work. 

National Research Council. 1976. Health effects of alpha-emitting particles in the respiratory tract. Report of ad hoc committee on "hot particles" of the advisory committee on the biological effects of ionizing radiations. National Academy of Sciences, National Research Council, Washington, D.C. 

Thus, the Gray expresses the amount of radiation absorbed by the body and the Sievert takes into account the effect of the radiation on the human body. For electromagnetic radiation (gamma and x-rays), these are considered as equal, that is, a dose of 1 Gy is equivalent to 1 Sv. However, for energetic particles absorbed by the body, the biological effects are more severe, so that a dose of one Gy of radiation by alpha particles would be equivalent to 20 Sv. 

For alpha particles, the relative biological effectiveness (rbe) may be as high as 20, so that one rad is equivalent to 20 rem. However, for x-rays and gama rays, the rbe is taken as one so that the rad and rem are equivalent for those radiation sources. 

Although often assumed to represent the essential parameter, LET is not suitable to define uniquely the increased biological effectiveness of charged particles (see Fig. 18). For example, the action of protons has been studied in detail and compared to the effectiveness of a-particles at the same LET [73,74]. Protons show a significantly higher effectiveness compared to alpha particles in the LET region 20-30 keV/pm, where protons already have reached maximal RBE values in contrast, this maximum is shifted for alpha particles to about 100 keV/pm. The same systematics extends to even heavier particles for neon ions, the maximal RBE values are found for LET values of approximately 250 keV/pm [75]. 

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