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Checking the foundation: recent radiobiology and the linear no-threshold theory.

Authors
Ulsh-BA
Source
Health Phys 2010 Dec; 99(6):747-758
NIOSHTIC No.
20038006
Abstract
The linear no-threshold (LNT) theory has been adopted as the foundation of radiation protection standards and risk estimation for several decades. The "microdosimetric argument" has been offered in support of the LNT theory. This argument postulates that energy is deposited in critical cellular targets by radiation in a linear fashion across all doses down to zero, and that this in turn implies a linear relationship between dose and biological effect across all doses. This paper examines whether the microdosimetric argument holds at the lowest levels of biological organization following low dose, low dose-rate exposures to ionizing radiation. The assumptions of the microdosimetric argument are evaluated in light of recent radiobiological studies on radiation damage in biological molecules and cellular and tissue level responses to radiation damage. There is strong evidence that radiation initially deposits energy in biological molecules (e.g., DNA) in a linear fashion, and that this energy deposition results in various forms of prompt DNA damage that may be produced in a pattern that is distinct from endogenous (e.g., oxidative) damage. However, a large and rapidly growing body of radiobiological evidence indicates that cell and tissue level responses to this damage, particularly at low doses and/or dose-rates, are nonlinear and may exhibit thresholds. To the extent that responses observed at lower levels of biological organization in vitro are predictive of carcinogenesis observed in vivo, this evidence directly contradicts the assumptions upon which the microdosimetric argument is based.
Keywords
Radiation-protection; Radiation; Radiobiology; Radiation-exposure; Radiation-effects; Dose-response; Dosimetry; Analytical-models; Analytical-processes; Author Keywords: chromosome aberration; cytogenetics; health effects; linear hypothesis
Contact
Brant A. Ulsh, National Institute for Occupational Safety and Health, 4676 Columbia Parkway, Mailstop C-46, Cincinnati, OH 45226
CODEN
HLTPAO
Publication Date
20101201
Document Type
Journal Article
Email Address
bau6@cdc.gov
Fiscal Year
2011
NTIS Accession No.
NTIS Price
Issue of Publication
6
ISSN
0017-9078
NIOSH Division
DCAS
Source Name
Health Physics
State
OH
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