Standards in biological dosimetry: A requirement to perform an appropriate dose assessment.

Every year, many countries perform a significant number of investigations based on biological radiation dose assessment to check suspected or true overexposure by irradiation of radiation workers and individuals of the general population. The scoring of dicentrics in peripheral blood lymphocytes has gradually become the "gold standard" for the biodosimetry-based assessment of accidental situations. Nevertheless, other "classical" biodosimetric methods such as micronuclei, prematurely condensed chromosomes (PCC) and FISH translocations are relevant in some exposure situations, also for surveillance of groups of populations at risk. Historical international intercomparison studies have shown discrepancies among dose-effect curves used to estimate doses from blood samples irradiated between 0 and 4Gy. Recent experimental work performed by the biological dosimetry laboratory of the French Institute for Radiation Protection and Nuclear Safety (IRSN) has shown the impact of some blood harvesting parameters on the mitotic index, and consequently on the quality of dose assessment. Therefore, it was relevant to define the best Quality Assurance (QA) and Quality Control (QC) criteria to harmonize protocols among biodosimetry laboratories. Complementary with several editions of an IAEA technical manual, ISO standards were written with the view of considering the most used chromosome aberrations assays: dicentrics and micronuclei. An important feature of these standards is to address the organization of population triage and laboratories networking that would be required in case of a large nuclear event or malicious act involving radioactive material. These ISO standards are relevant and helpful to implement a coordinated response of several biodosimetry networks in Europe, Japan, Canada, and to support European programs such as MULTIBIODOSE and RENEB. A new important ISO standard on the use of FISH translocations in retrospective dosimetry is now being drafted.