There is no system for monitoring exposure of persons working in activities which enhance exposure to NORM. The studies so far published show that exposure can range from a few millisieverts to several tens of millisieverts per year. Worker exposure to technologically-enhanced naturally occuring ionising radiation (TENORM) is the result either of the ingestion of dust containing large amounts of radionuclides (phosphates, metal ore), or of the inhalation of radon formed by uranium decay (poorly ventilated warehouses, thermal baths) or of external exposure due to process deposits (scale forming in piping for example). Thus, for example:

• industries handling raw materials that are naturally rich in radionuclides (phosphates, foundry ore, zirconium silicates, dye pigments, rare earths) can lead to annual worker exposure of several millisieverts;

• extraction of oil and natural gas can also lead to annual doses of several millisieverts through irradiation due to the particularly radioelement-rich scale that forms in the pipelines;

• in spas, the high radon content of the water and the poor ventilation indicate that there would be significant doses, both for the personnel and the public coming to take the waters (a bibliographical study by the IRSN of foreign spas shows that annual doses of 10 to 100 mSv are common for the personnel and from 1 to 4 mSv for the members of the public).

Airline flight crews and certain frequent travellers are exposed to significant doses owing to the altitude and the intensity of cosmic radiation at high altitude. These doses can exceed 1 mSv/year. We therefore estimate that the mean annual dose for "short-haul" crews would be from 1 to 2 mSv, from 3 to 5 mSv for "long-haul" crews and up to 10 mSv for certain air mail flight crews.

In order to collect data about this natural exposure, an observation system named SIEVERT was set up by the Directorate General for Civil Aviation, the IRSN, the Paris Observatory and Paul-Émile Victor French institute for polar research
(www.sievert-system.com).

The automatic monitoring networks managed nationwide by the IRSN (Téléray, Hydrotéléray and Téléhydro networks) offer real-time monitoring of environmental radioactivity and can highlight any abnormal variation. In the case of an accident or incident leading to the release of radioactive substances, these measurement networks would play an essential role by providing data to back the decisions to be made by the authorities and by notifying the population. In a normal situation, they take part in evaluating the impact of BNIs.

However, for methodological reasons, there is no overall monitoring system able to provide an exhaustive picture of the doses received by the population as a result of nuclear activities. Consequently, it is impossible to directly control compliance with the exposure limit for the population (see chapter 3). However, for BNIs, radioactive effluent discharges are precisely accounted for and radiological monitoring of the environment surrounding the installations is in place. On the basis of the data collected, the dosimetric impact of these discharges on the populations living in the immediate vicinity of the installations is then calculated, using models for simulating transfers to the environment. The dosimetric impacts vary, according to the type of installation and the living habits of the reference groups chosen, from a few microsieverts to several tens of microsieverts per year.

These estimates are unknown for nuclear activities other than BNIs. Prior methodological studies are required in order to obtain a clear knowledge of these facilities, in particular the impact of discharges containing small quantities of artificial radionuclides originating from the use of unsealed radioactive sources in research or biological laboratories, or in nuclear medicine departments. These are in progress within the IRSN at the request of the ASN.