Radio-Adaptive Response to Environmental Exposures at Chernobyl

Abstract

h The genetic consequences resulting from environmental exposure to ionizing radiation have a significant impact on both radiation regulatory policies and the comprehension of the human health risks associated with radiation exposure. The primary objectives of the study were to assess 1) genotoxicity of exposure to radiation as a function of absorbed dose and dose rate, and 2) induction of a radio-adaptive response following a priming dose at varying dose rates. Results demonstrated that sub-acute environmental exposures of 10cGy gamma radiation resulted in indistinguishable levels of chromosomal damage as compared to controls. A radio-adaptive response was observed in all experimental groups, exposed to a subsequent acute challenge dose of 1.5 Gy, demonstrating that low dose rates of low energy transfer (LET) radiation are effective in reducing genetic damage from a subsequent acute low-LET radiation exposure. Furthermore, the data presented herein demonstrate a potential beneficial effect of sub-chronic exposure to low levels of low-LET radiation in an environmental setting and do not support the Linear No Threshold (LNT) hypothesis.

Low-dose Pretreatment for Radiation Therapy

“…Exposure experiments on rats have been carried out at the Chernobyl accident site (Rodgers and Holmes 2008). Under a variety of conditions, a pre-dose of 10 cGy was given at various dose rates up to 24 hours before a challenge dose of 1.5 Gy.…”

Gamma radiation at a human relevant low dose rate is genotoxic in mice

“…3 ), later revised to 100 mGy in the UNSCEAR 2013 report 4 . Indeed, very few animal studies have investigated the effects of continuous chronic LDR radiation at below 6 mGy/h 5 6 7 8 9 , likely due to the limited number of facilities allowing long term in vivo exposure at continuous LDR. This challenge was recognised by the European platform MELODI (Multidisciplinary European Low Dose Initiative) dedicated to low dose radiation risk research ( http://www.melodi-online.eu/ ).…”

Radiation Worker Protection by Exposure Scheduling

“…At U. C. Davis (Goldberg, et al 2004) en vivo genetic activation experiments were performed on healthy human skin plugs and resulted in similar protective results for the cellular adaptive response to a low radiation dose. Rodgers and Holmes (2008) showed that a low dose (~ 100 mSv) delivered to mice at a very low dose rate over several weeks caused little detectable damage over the control presumably because the cell repair mechanisms had sufficient time to act. The same low dose delivered at a high rate, over ~20 minutes, caused measurable damage.…”

“…Rodgers and Holmes (2008) showed that a low dose (∼100 mSv) delivered to mice at a very low dose rate over several weeks caused little detectable damage over the control presumably because the cell repair mechanisms had sufficient time to act. The same low dose delivered at a high rate, over ∼20 minutes, caused measurable damage.…”