Dosimetry and occupational radiation exposure

In Switzerland, more than 100,000 people are occupationally exposed to radiation. This corresponds to about 2% of the working population that must be effectively protected from ionising radiation. This includes individual monitoring of the radiation dose.

Anyone who is at increased risk of radiation exposure during work or training is considered to be an occupationally exposed person. In the area supervised by the FOPH this applies, for example, to people operating an X-ray machine or handling radioactive substances in hospital or in research.

Dosimetry

Dosimetry refers to the measurement and evaluation of radiation exposure, aimed at radiological protection, compliance with dose limits, and assessment of the risks associated with radiation exposure.

For persons occupationally exposed to radiation, radiation exposure must be determined individually in accordance with the Dosimetry Ordinance by a recognized dosimetry service. In this case, it is referred to as individual dosimetry.

In individual dosimetry, a distinction is made between dose due to external exposure and internal exposure:

  • Dose due to external exposure: Exposure to external radiation, such as that emitted by X-ray installations or computed tomography scanners, or by sealed and unsealed radioactive sources, is usually measured using personal dosimeters. A dosimeter is a measuring device used to determine the dose of radiation received by a person as a result of exposure. Measurements are performed, for example, using whole-body dosimeters, extremity dosimeters, or lens dosimeters.
  • Dose due to internal exposure: In the case of a risk of internal exposure to radioactive substances, this is referred to as incorporation, i.e., the absorption of radioactive nuclides via ingestion, inhalation, or through the skin. This exposure is assessed by direct measurements on the body (triage measurements) and, if necessary, supplemented by more precise analyses of biological samples (urine and/or feces) or whole-body measurements (whole-body counter) to determine the activity accumulated and/or excreted by the body, as well as the committed effective dose (incorporation measurements).
  • A proven method for flight personnel is calculating doses on the basis of the flight route.

A proven method for flight personnel is calculating doses on the basis of the flight route.

If elevated doses or limit exceedances are detected, the FOPH conducts an investigation together with the concerned establishment. Radiation protection measures are implemented to prevent further exposure or, at a minimum, to reduce it. Establishments have a fundamental obligation to optimise radiological protection, ensuring that doses and the risks of exposure are reduced as far as reasonably practicable.

Central Dose Registry

The FOPH maintains a Central Dose Registry (CDR). Here the results of the dosimetry of each occupationally exposed person have been recorded since 1989.

The register serves the following purposes:

  • To record the doses determined over the entire professional activity of exposed persons, in order to clarify any potential insurance claims;
  • To perform supervisory functions;
  • To provide the basis for the preparation of an annual statistical report, published in the the annual dosimetry report of the supervisory authorities (annual dosimetry report, not available in Italian) by the supervisory authorities.

The number of occupationally exposed persons in Switzerland has increased by nearly 60% in the last 20 years, while the total dose received by all persons monitored (collective dose) has remained relatively stable. Approximately two-thirds of these workers are in the medical sector, which is also where most dose limit exceedances are currently observed. These exceedances mostly concern the lens of the eye dose of personnel performing procedures involving fluoroscopy, in interventional radiology or cardiology.

Further information

Federal Office of Public Health FOPH

Radiological Protection Division
Non-ionising Radiation and Dosimetry Section
Schwarzenburgstrasse 157
Switzerland - 3003 Bern