The current system of radiation protection for humans is based on the linear-no-threshold (LNT) risk-assessment paradigm. Perceived harm to irradiated nuclear workers and the public is mainly reflected through calculated hypothetical increased cancers. The LNT-based system of protection employs easy-to-implement measures of radiation exposure. Such measures include the equivalent dose (a biolog...

Exposure to ionizing radiation (IR) is inevitable to humans in real-life scenarios; the hazards of IR primarily stem from its mutagenic, carcinogenic, and cell killing ability. For many decades, extensive research has been conducted on the human cell responses to IR delivered at a low dose/low dose (LD) rate. These studies have shown that the molecular-, cellular-, and tissue-level responses ar...

Hormesis, a dose-response phenomenon characterized by a low-dose stimulation and a high-dose inhibition, has been the object of controversy due to its challenging of basic understandings of the dose-response relationship and implications for risk assessment. The author addresses issues relating to the definition of hormesis, the relationship of hormesis to risk assessment and risk management, a...

The damage and signaling to cells and tissues with subsequent stimulatory responses induced by low doses of ionizing radiation were reviewed in Part 1 (J Nucl Med. 2001;42[7]:17N–27N). In the intact organism, these responses are expressions of complex adaptive systems that maintain homeostatic control essential for survival. The antimutagenic DNA damage-control system is the central component o...

Metabolic and energetic efficiency, and hence fitness of organisms to survive, should be maximal in their habitats. This tenet of evolutionary biology invalidates the linear-no threshold (LNT) model for the risk consequences of environmental agents. Hormesis in response to selection for maximum metabolic and energetic efficiency, or minimum metabolic imbalance, to adapt to a stressed world domi...

The interrelationship between ionizing radiation and the immune system is complex, multifactorial, and dependent on radiation dose/quality and immune cell type. High-dose radiation usually results in immune suppression. On the contrary, low-dose radiation (LDR) modulates a variety of immune responses that have exhibited the properties of immune hormesis. Although the underlying molecular mechan...