Chromosomal aberrations in peripheral blood lymphocytes exposed to a mixed beam of low energy neutrons and gamma radiation

Abstract

Cells exposed to thermal neutrons are simultaneously damaged by radiations with high and low linear energy transfer (LET). A question relevant for the assessment of risk of exposure to a mixed beam is whether the biological effect of both radiation types is additive or synergistic. The aim of the present investigation was to calculate whether the high and low LET components of a thermal neutron field interact when damaging cells. Human peripheral blood lymphocytes were exposed to neutrons from the HB11 beam at the Institute for Energy and Transport, Petten, Netherlands, in a 37 °C water phantom at varying depths, where the mix of high and low LET beam components differs. Chromosomal aberrations were analysed and the relative biological effectiveness (RBE) values as well as the expected contributions of protons and photons to the aberration yield were calculated based on a dose response of aberrations in lymphocytes exposed to (60)Co gamma radiation. The RBE for 10 dicentrics per 100 cells was 3 for mixed beam and 7.2 for protons. For 20 dicentrics per 100 cells the respective values were 2.4 and 5.8. Within the limitations of the experimental setup the results indicate that for this endpoint there is no synergism between the high and low LET radiations.

Neutron relative biological effectiveness in Hiroshima and Nagasaki atomic bomb survivors: a critical review

“…Experimental systems using fission neutrons are usually a mixture of differing levels of γ-rays. Yet, at least at biologically relevant moderate doses, nil or negligible levels of interaction of high– and low–linear energy transfer (LET) radiations have been reported for various biological endpoints in mixed radiation fields [34–41]; however, others have reported synergistic-like effects [42, 43]. …”

Cancer Studies under Space Conditions: Finding Answers Abroad

“…In addition to the differences between high-LET and low-LET radiation, there are conflicting results on whether irradiation of cells with low-LET radiation before high-LET radiation, as would occur in a space environment, has a synergistic or protective effect on DNA damage. Most researchers have stated there is a detrimental effect of pre-irradiation with low-LET radiation followed by high-LET radiation, with peak chromosomal damage at a 30-min interval between the irradiation regimes [ 68 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 ]. However, Buonanno et al [ 87 , 88 ] and Stoilov et al [ 87 , 88 ] have observed a protective effect if the interval is up to 24 h, with researchers attributing this effect to the upregulation of redox scavengers of antioxidants.…”

High-Accuracy Relative Biological Effectiveness Values Following Low-Dose Thermal Neutron Exposures Support Bimodal Quality Factor Response with Neutron Energy

“…Evaluations of the dicentric chromosome assay (DCA) RBE M of low-energy thermal neutrons in human peripheral blood lymphocytes are reported in several previous publications (Table 1), with maximum RBE (RBE M ) results ranging from 10.8 ± 1.8 to 51.1 ± 31.3 [16][17][18][19]. The wide range of DCA RBE values and the large associated errors makes pinpointing a single thermal neutron RBE value difficult.…”