BIOLOGICAL EFFECTS OF IRRADIATION

Binder, R. Nowotny, W. Schmidt, N.0. Bianchi, P.P.W. van Buul, A.T. Natarajan, L. Fabry, A. Leonard, M. KucerovA, D.C. Lloyd, U. Mukherjee, G. Obe, F. Palitti, and T. Sharma, Comparison of Dose Dependence of Chromosome Aberrations in Peripheral Lymphocytes at Low Levels of Acute in Vitro Irradiation With 250 kV X-Rays and 14 MeV Neutrons, in Proceedings of the International Symposium on Biological Effects of Low-Level Radiation in Venice, pp. 171-184 International Atomic Energy Agency, Vienna, Austria (1983). 

Fig. 5.43 The UV part of the sun spectrum, the erythema action spectrum and the biological effective solar irradiance. The biological effective irradiance has been obtained by folding the radiation density of the sun with the erythema action spectrum.

Biologic effects of non-excited fullerenes C60, that are revealed at the concentration range lower than 10 4 M, are mostly positive, but depend on the type of cells and the way of modification of fullerene C60 (Yamakoshi et al., 1994). As we have shown earlier, upon the presence of 10 6 M fullerenes C60 in incubation medium, resistance of erythrocytes to hemolysis is not altered, whilst at the concentration of 10 5 M fullerenes C60 the hemolysis rate is accelerated. Hemolytic effect was not revealed if fullerene C. at the concentration of 10 5 M was introduced to the con-tent of aminopropylaerosyl (i.e., upon the presence of fullerene C60-composite-l). Cytotoxic influence was not found if thymocytes and EAC cells were incubated with fullerenes C60 (10 5 M) or fullerene C60-containing composites for 24 h (Piylutska et al., 2006). That is why the study of the influence of irradiation on biologic activity of fullerenes C60 was carried out at their concentration of 10 5 M. 

From the data of literature it is known that water-soluble derivatives of fullerenes are able to be localized in mitochondria and influence their state as well as enzyme system (Foley et al., 2002). Such intracellular localization of fullerenes C60 could explain biologic effects under irradiation, because generation of free oxygen radicals in the cells occurs during emission of electrons from electron-transport chain of mitochondria. 

AltshuUer. A. P.. D. L. Klosterman, P. W. Leach. I. J. Hindawi, and J. E. Sigsby. Jr. Products and biological effects from irradiation of nitrogen oxides with hydrocarbons or aldehydes under dynamic conditions. Int. J. Air Water Pollut. 10 81-96, 1966. 

The biological effectiveness of dose depends on the type of radiation and also on the mass and sensitivity of the irradiated tissue. For alpha irradiation, a quality factor of 20 is assumed (ICRP, 1981), and the dose in Sieverts is 20 times the dose in Grays. In addition, ICRP recommends a weighting factor of 0.12 for irradiation of the whole lung and 0.06 for irradiation of bronchial epithelium only. Thus the effective dose equivalent , symbol HE, is defined as the dose to the whole body which carries the same risk as the given dose to the organ or tissue. This, for irradiation of bronchial tissue is 20 x 0.06 = 1.2 times the dose to the organ in Gy. 

Altshuller, A. P. et al., Products and Biological Effects from Irradiation of... 

Sievert (Sv) It is a more modem unit that substitutes the rem, as it reflects the biological effect of radiation. It is defined as the absorbed dose in Gy multiplied by a somewhat complicated factor that takes into account for example the quality factor defined above, the part of the body irradiated and the time and volume of exposure. 1 Sv = 100 rems. 

Zapol Skaya NA, Borisova W, Zhomo LY, et al. 1974. Comparison of the biological effect of strontium-90, cesium-13 7, iodine-131 and external irradiation. In International Radiation Protection Association, ed. Third International Congress of the International Radiation Protection Association. Springfield, VA U.S. Atomic Energy Commission, 147-152. 

The units of absorbed dose defined in the previous section are quite adequate for the quantitative assessment of the effects of radiation to inanimate objects, like irradiated transistors or reactor fuel. For protection of people, however, the important thing is not the measurement of energy deposited—i.e., the absorbed dose—but the biological effects due to radiation exposure. Unfortunately, biological effects and absorbed dose do not always have one-to-one correspondence, and for this reason a new unit had to be defined a unit that takes into account the biological effects of radiation. 

---