Detection of biological responses to low-dose radiation in humans.

It has been considered difficult to detect the biological effects of low-dose radiation exposure below approximately 100 mSv in humans. Serum proteomic analysis and oxidative modification profiling were conducted with blood samples collected from residents of a newly discovered high-level natural background radiation area (annual effective dose approximately 50 mSv y) and normal-level area (1.22 mSv y) in Mamuju, Indonesia, where many people have been living for generations. Dose-dependent oxidative modifications in amino acid sequences of human serum albumin, especially the 162 and 356 tyrosine residues and 111 and 470 methionine residues, were found. None of these findings have been reported in humans exposed to chronic low-dose radiation. It can be used as a biomarker not only for the assessment of the presence or absence of radiation exposure but also for dose prediction in living organisms for chronic radiation. These results suggest that traces of radiation exposure are recorded in serum albumin and that there is a possibility of a new methodology that can evaluate biological responses below 100 mSv.