Radiological control of the environment

The "Radiological control of the environment" fact sheet monitors the concentrations of artificial and natural radionuclides in environmental compartments (atmospheric, aquatic and terrestrial) deemed as direct routes of contamination for Man, in order to ensure the monitoring of the actual exposure of the Portuguese population to radioactivity.

Radioactivity is neither a recent phenomenon, nor exclusively the result of anthropogenic actions. In fact, the Earth has always been subject to cosmic radiation and its constitution has always included a series of radionuclides (unstable form of a nuclide that releases energy in the form of ionising radiation to become stable). Nowadays, after the discovery of radioactivity and its subsequent use in various areas of activity, the radionuclides found in the environment can have either a natural or an anthropogenic origin. They basically result from four different sources: 

  • Radon (Rn) exhalation into the atmosphere, 222Rn and 220Rn, produced by the radioactive disintegration of radium (Ra), 226Ra and 224Ra (natural constituents of soils and rocks) belonging to the natural radioactive series of 238U and 232Th, respectively, a good example of which is the occurrence of 210Pb descendent of a long term disintegration of 222Rn;
  • Formation of cosmogenic radionuclides such as 7Be through the interaction of cosmic radiation with atmospheric gases containing carbon, nitrogen and oxygen;
  • Technologically enhanced natural radiation, resulting from the industrial use of raw materials containing natural radionuclides;
  • Artificial radionuclides, which are fission and activation products resulting from anthropogenic activities (nuclear tests, generation of electricity in nuclear power plants, radioisotope production, accidents, etc.).

Regardless of their origin, radionuclides can be present in the atmosphere in the gaseous or particulate form (associated with atmospheric aerosol). Usually, the particulate form is the one that poses the most significant radiological risk, since these particles interact with the biosphere through atmospheric transport and deposition processes.

The radiological surveillance of the environment in Portugal, outlined according to the country's specific characteristics, is the responsibility of the Portuguese Environmental Agency (APA) and is carried out through monitoring programmes consisting of determining the presence of artificial and natural radionuclides in environmental compartments (atmospheric, aquatic and terrestrial), which represent direct contamination pathways for Man.

Radiation exposure can affect human health, namely through genetic modifications and the emergence of various types of neoplasms (leukaemia, lung cancer, skin cancer, stomach cancer, etc.). Exposure can be direct (namely via human exposure to the source) or indirect, via the environment (air, water, soil, food) due to the accidental introduction of those substances into the environment.

Portugal has a Continuous Environmental Radiation Surveillance Network (RADNET), which is fully operational and able to detect events of abnormal increase of environmental radiation. Currently, RADNET has 14 fixed stations for measuring the dose rate of gamma radiation in the air, two fixed stations for measuring the dose rate of gamma radiation in the water (at Fratel Dam in Tagus river and at Pocinho Dam in Douro river), a mobile station (car mounted), a mobile spectroscopic station for use in terrestrial, aerial and aquatic vehicles and two portable stations. An expansion project is underway in which seven more stations with gamma spectrometry of the latest generation were acquired and are undergoing testing and installation phases. The network is continuously measuring the gamma radiation present in the environment, triggering an alarm when the measured radiation levels exceed a pre-set threshold, which corresponds to three times the average value measured in normal conditions. In these cases, the alarm received by the central unit triggers the automatic audible and visual systems installed at the Portuguese Environmental Agency, responsible for managing the RADNET.

In addition to the RADNET, there is radiological monitoring of the environment based on samples of aerosols, surface waters, food chain components and complete meals. This monitoring is carried out by Instituto Superior Técnico (IST).

This fact sheet concerns mainland Portugal and the Autonomous Regions of Madeira and the Azores and shall be updated whenever new data is made available.

Objectives and targets: 
  • Ensure that the RADNET is operational, enabling an immediate notification in the event of the detection of abnormal values and proceed with a prompt and well-coordinated response at the national level;
  • Ensure the routine monitoring of environmental radiation and the identification of deviations in values with radiological relevance.
Progress analysis:
Last update: 
Wednesday, 24 April, 2019