Abstract
In this study, the yields of unstable chromosome aberrations in human lymphocytes induced by β particles from low-dose HTO have been measured. HTO was mixed with heparinized blood in varying amounts so that a dose of 6.24 × 10－4 Gy to 1.23 Gy were delivered in 24 and 48 h, respectively. After 72-h culture, the dicentric yield was measured as a function of dose to the blood and compared with data from 60Co γ-radiation. Using a linear-quadratic dose-effect relation to fit the experimental data, a significant linear contribution Y = 0.062D + 0.053D2 was found. The main difference between the coefficients for β and γ-radiation was in the a values, indicating that HTO β-rays were more efficient, particularly at low doses. As per the theory of dual radiation, the relative biological effectiveness (RBE) of HTO β-particles relative to γ-rays is 2.21 at 0.06 Gy and decreases with increasing dose. Micronucleus yield at low doses was fitted to a linear equation Y = C + αD, indicating that the RBE value of MN for HTO β-rays irradiation was between 1.46 and 2.17, which is similar in shape to the chromosome aberrations experiments. Thus, β-rays were found to be more efficient in producing two lesions with single ionizing tracks at low dose.
Highlights
Tritium is a naturally occurring radionuclide widespread in nature as well as an important fission nuclide
Tritium can enter the human body via inhalation, ingestion, and penetration through skin, where it binds to DNA and RNA within cells causing direct radiation-mediated damage and chromosomal aberrations
The benefit of using dic + r for aberration evaluation is that the incidence of spontaneous dic + r is relatively low in non-irradiated controls (0.5‰ to 5‰ per cell) while high incidence of this event can be induced by radiation
Summary
Tritium is a naturally occurring radionuclide widespread in nature as well as an important fission nuclide. The average range of tritium β-rays is only 0.036 cm in air, it does not pose a radiation hazard outside the human body; tritium can cause internal radiation-mediated injury when ingested. Tritium can enter the human body via inhalation, ingestion, and penetration through skin, where it binds to DNA and RNA within cells causing direct radiation-mediated damage and chromosomal aberrations. Studies on the biological effect of tritium have shown that HTO can pose radiation hazards to the human body including acute radiation injury, somatic cell damage, reproductive cell damage, chromosomal aberrations, hazardous effects on growth and development of offspring, and other non-stochastic effects. Studies on the carcinogenic and genotoxic effects and the toxic effect on reproductive cells have revealed that the radiation weighting factor for tritium ranges between 1.7 and 2.4 [4]; tritium is a radionuclide closely associated with public health
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