New developments in chromosomal analysis for biological dosimetry

Biological dosimetry by dicentric analysis has proved useful on many occasions. An example is given where cytogenetics combined with physical methods have been used to estimate dose in a recent serious over-exposure. The value of dose information for the physician is emphasised since dose can be related to risk of deterministic and stochastic consequences to health. A major new development, FISH, for visualising stable translocations, is discussed with respect to its applicability as a retrospective dosemeter. An example is given where a credible estimate of dose was obtained 11 years after a uniform whole-body accidental exposure. A cautionary note is raised, illustrated by an in vitro experiment, indicating that non-uniform or partial body irradiation may cause the translocation yield to decrease with time. Finally, comments are made on the effort required and the limits of low dose resolution that FISH offers, which must be considered if the technique is to be used for retrospectively evaluating populations exposed to widespread environmental contamination by radionuclides.