The pathology monitoring systems set up (cancer registers for example) do not enable those pathologies attributable to ionising radiation to be determined. Nor do we have reliable and easily measurable biological indicators which could be easily used to recreate the radiation dose to which the persons were exposed. In this context, "risk monitoring" is performed by measuring ambient radioactivity indicators, or at best by measuring the dose rates linked to external exposure to ionising radiation or internal contamination, or failing which, by measuring values (concentration of radionuclides in radioactive waste discharges) which would then enable an estimate of the doses received by the exposed populations to be calculated.

The entire French population is potentially exposed, although to different extents throughout the country, to ionising radiation of natural origin and to radiation created by human activities. The average exposure of the French population is estimated, per inhabitant, at 4 mSv per year, but this exposure is subject to wide individual variability, in particular depending on the place of residence and the number of radiological examinations received (source: National health and environment plan, report by the National Orientation Committee - February 2004). The following diagram represents an estimate of the respective contributions of the various sources of French population exposure to ionising radiation.

These data are mainly extracted from international literature and are too imprecise to allow identification - in each category of exposure sources - of the categories or groups of persons most exposed.

Exposure of the population to naturally-occuring ionining radiation (NORM) is the result of the presence of radionuclides of terrestrial origin in the environment, radon emanations from the ground and exposure to cosmic radiation.

Terrestrial radiation (excluding radon)

Natural radionuclides of terrestrial origin are present at various levels in all aspects of our environment, including inside the human organism. They lead to external exposure of the population owing to gamma radiation emissions produced by the uranium 238 and thorium 232 chains and by the potassium 40 present in the soil, but also to internal exposure by inhalation of radon or particles in suspension, and by ingestion of foodstuffs or drinking water.