Current Trends in Radiation Protection

The IRPA congresses constitute umque opportumtles to gather ali actors of radiological protection, irrespective of their ongm or their field of action in the vast world of radioprotection. The IRPA11 Congress in Madrid will perpetuate this tradition at the very moment where all stakeholders, whether researchers, radioprotectionists, regulators, private industrial operators or national institutions, feel a need for widening the scope of this profession.

Radiological protection falls now under the public's active scrutiny. Its perception of risks and the measures taken to reduce them as much as possible, whilst maintaining the activities necessary to the well being of humankind need now to be explained. This congress directly fulfùs this new line of action, a perfect illustration lying in the title that has been chosen: "Widening the radiation protection world".

However, this widening should also become apparent on the libraries shelves and the fruitful debates of IRPA congres ses should evolve beyond the restricted circles of specialists. This is why we have launched this new series of books "Trends in radiation protection" which will spread the state of the art in radiological protection to the entite world, researchers, regulators, experts. In arder to guarantee information of high quality and devoid of passion, we have called on board renowned experts in their various fields of activities. Their immediate agreement upon our invitation constitutes the first success of this book. We are very grateful to all of them without whom this book would not exist.

ICRP recommendations being endorsed throughout the world, a critical analysis of their impact on current life was necessary: how are the recommendations applied, what are the physical tools necessary for their application, how professionals must be educated and especially the medical world that is the big responsible for the collective irradiation of populations.

But beyond such recommendations and the application of rigorous safety rules, incidents with radioactive sources and nuclear accidents remain possible. It is thus necessary to reconstruct such difficult situations in terms of exposure, to properly evaluate the contamination of the affected territories, and to promote coherent and practical proposals for remediation. The experimental feedback from such situations is a tremendous source of progress for their prevention.

Abstract. It is widely accepted that damage to DNA is the critical event in irradiated cells, and that double strand breaks are the primary DNA lesions responsible for the biological effects of ionizing radiation. This has led to the long standing paradigm that these effects, be they cytotoxicity, mutagenesis or malignant transformation, occur in irradiated cells as a consequence of the DNA damage they incur. Evidence has been accumula ting over the past decade, however, to indicate that radiation may induce effects that are not targeted to the irradiated cell itself. Two "non-targeted effects will be described in this review. The first, radiation-induced genomic instability, is a phenomenon whereby signais are rransmitted to the progeny of the irradiated cell over many generations, leading to the occurrence of genetic effects such as mutations and chromosomal aberrations arising in the distant descendants of the irradiated cel!. Second, the bystander effect, is a phenomeon whereby irradiated cells transmit damage signais to non-irradiated cells in a mixed population, leading to genetic effects arising in the se "bystander" cells that received no radiation exposure. The mode! system described in this review involves dense monolayer cultures exposed to very low fluences of alpha particles. The potential implications of these two phenomena for the analysis of the risk to the human population of exposure to low levels of ionizing radiation is discussed.

Ionizing radiation has many unique characteristics as a mutagen and carcinogen. These derive from its ability to penetrate cells and tissues and to deposit energy within them in the form of ionizations; that is, the ejection of orbital electrons from atoms or molecules. This event may lead to irreversible damage in the molecule involved, or the resultant free radical (an atom or molecule containing an unpaired electron) may initiate a chain of chemical reactions mediated through cellular water with the ultimate biology damage occurring in another molecule in the cel!.