[Calculation of gaseous forms and sizes of aerosol particles 131 Iodine- the radioactive fallout of Chernobyl accident by calculation of inhaled radiation dose].

After the Chernobyl accident the isotopes of radioiodine in air were detected both in aerosol and gaseous forms. In the ICRP publication, No 30 the committed dose equivalent in thyroid per intake of unit activity of 131I, B(ih), were presented. This value holds true only for aerosols with activity median aerodynamic diameter (AMAD) 1 micron. The radioactivity deposition coefficients in human respiratory tract have another values for molecular and organic forms of gaseous radioiodine. In present work the measured AMAD and the proportion between aerosols, molecular and organic forms of 131I in various regions after the accident are given. The correction factors for B(ih) are calculated for the following cases: 1) the radioiodine concentration in air is measured by means of the aerosol filter only, 2) all forms of radioiodine are sampled. The neglection of the gaseous forms of radioiodine could lead to extremely large errors in the determination of inhaled dose radiation: the real value of dose radiation could exceed calculated one by more than 5 times.